Parasellar Schwannomas: Extradural vs Extra-Intradural Surgical Approach

Parasellar Schwannomas: Extradural vs Extra-Intradural Surgical Approach Abstract BACKGROUND Schwannomas of the parasellar region may arise from the trigeminal, oculomotor, trochlear, and abducens nerves. OBJECTIVE To define the tumor origin, location, and dural relationship (extradural vs extra-intradural vs cisternal) on preoperative magnetic resonance imaging (MRI), in order to plan the best surgical approach (purely extradural vs extra-intradural). METHODS Twenty-four patients with parasellar schwannomas who underwent surgery were retrospectively analyzed. Twenty arose from the trigeminal nerve (7 intracavernous and 13 within the Meckel's cave), 3 from the oculomotor nerve, and 1 from the abducens nerve. The preoperative identification of the tumor location (extradural vs extra-intradural vs cisternal) and the nerve of origin was defined on MR sequences. All patients were operated on through a pterional approach (extradural or extra-intradural route). RESULTS The tumor location was correctly defined on MRI in 22 out of 24 cases (92%) and the nerve of origin in 22 (92%). An extradural approach without intradural exploration was performed in all 5 intracavernous trigeminal schwannomas, in 11 out of 13 of the Meckel's cave, and in 2 schwannomas of the oculomotor nerve. Two schwannomas of the Meckel's cave with transgression of the medial dural wall, 1 of the oculomotor nerve, and the abducens nerve schwannoma required an extra-intradural approach. Complete tumor resection was obtained in 19 out of 24 cases (80%). CONCLUSION The pterional extradural approach is sufficient for Dolenc type I and II trigeminal schwannomas, excepting for those transgressing the inner dural layer. Schwannomas of the oculomotor and abducens nerves with cisternal location require an extradural-intradural approach. Abducens nerve schwannoma, Magnetic resonance, Oculomotor nerve schwannoma, Skull base approach, Trigeminal nerve schwannoma ABBREVIATIONS ABBREVIATIONS CSF cerebrospinal fluid CT computed tomography ICA internal carotid artery MRI magnetic resonance imaging SSFP steady-state free procession Parasellar schwannomas may arise from the third, fourth, fifth, and sixth cranial nerves. Among them, trigeminal schwannomas are more frequent (0.8%-8% of all intracranial schwannomas),1-4 whereas those of the oculomotor (36 reported cases),5-8 abducens (25 cases),9-14 and trochlear (40 cases)15-17 nerves are quite rare. We have retrospectively analyzed 24 patients who underwent surgery for parasellar schwannomas. The aim of this study was to discuss the preoperative neuroradiological definition of the tumor location (extradural vs intra-extradural vs cisternal) and its role to plan the best surgical approach (pterional vs extradural vs extra-intradural). No previous studies have stressed this aspect. METHODS Twenty-four patients with schwannomas of the parasellar region who underwent surgical treatment at our neurosurgical clinic between 1995 and 2012 are included in the study. Cases extending outside the parasellar region (in the infratemporal and posterior fossae), those with insufficient clinical data, and those lost to follow-up were excluded. An ethics committee was not necessary because this is a retrospective study; however, all patients gave their consent for the use of all data. Case records, preoperative imaging studies, surgical descriptions, and postoperative clinical and radiological follow-up checks were reviewed. Detailed clinical, neurological, and ophthalmological examinations were done in each case. The preoperative neuroimaging studies included magnetic resonance imaging (MRI) with T1 basal and postcontrast sequences, T2 sequences, and 3-D gradient echo steady-state sequences in all cases. Six trigeminal schwannomas were also studied by 3-D computed tomography (CT) scan for defining the bone changes. The MR and CT images were reviewed by a neuroradiologist. The radiological variables assessed to determine the tumor location and its relationships with the dura and cisternal space included the following: (a) the evidence of the medial wall of the middle fossa in postcontrast axial and coronal images; (b) the shape of the medial tumor margins (smooth vs irregular); and (c) the relationship of the isohypointense tumor in the high-signal intensity of the cerebrospinal fluid (CSF) in axial and coronal T2-weighted images and steady-state free procession (SSFP) sequences. The tumor size was defined on postcontrast MRI sequences by measuring 3 linear dimensions (length, width, and height). The parasellar schwannomas arose from the trigeminal, oculomotor, and abducens nerves. Trigeminal schwannomas were classified, according to the classification of Dolenc,18 as type I (cavernous sinus) or type II (Meckel's cave). Schwannomas of the oculomotor and abducens nerves were classified in 3 types: cavernous, cisternal, and cisterno-cavernous.19 All patients were operated on through pterional craniotomy and skull base approach according to the tumor location and extension. In all cases, the diagnosis of schwannoma was confirmed by the histological studies and immunohistochemical staining (S100 protein). Postoperative evaluation and follow-up checks included clinical examination and MRI at 1 mo, 6 mo, 1 yr, and then every 3 yr. The extent of resection was determined on postoperative postcontrast MRI. The resection was defined as complete when no contrast enhancement was evidenced, and subtotal when the residual nodule was less than 10% of the initial tumor size. The actual follow-up ranges from 3.5 to 20 yr (average 11 yr). Factors that were considered include symptoms of clinical onset, tumor location and dural relationships, nerve of origin, type of surgical approach, entity of surgical resection, recurrence, and outcome. RESULTS The data of the 24 patients are summarized in Tables 1 to 5. The patients included 16 females and 8 males (male/female ratio = 1:2), with age ranging between 16 and 74 yr (median 51 yr). TABLE 1. Personal Series of Parasellar Schwannomas N. of case Age/sex Nerve of origin Location Size (cm) Clinical onset Surgical approach Entity of resection Outcome Follow-up (yr) Recurrence 1. 16/F l III Intracavernous and cisternal 1.7 × 1.5 × 1.2 Complete III palsy, proptosis Pterional epidural + intradural + EAC and UOC + grafting Complete Improved III palsy remission of proptosis 20 No 2. 51/F r III Intracavernous 2.0 × 1.8 × 2.0 Complete III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 11 No 3. 38/M r III Intracavernous 2.3 × 1.7 × 2.0 Partial III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 8 No 4. 30/M l VI Cisternal 3.2 × 2.6 × 2.8 Amaurosis, VI nerve palsy Pterional epidural + intradural Subtotal Unchanged 15 At 3 y reoperation 5. 45/F r V Intracavernous 2.5 × 1.8 × 1.4 V2 neuralgia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 16 No 6. 58/F l V Intracavernous and cisternal 2.0 × 2.0 × 3.0 V2-V3 neuralgia hypaesthesia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 18 No 7. 52/M r V Intracavernous 2.7 × 2.5 × 2.2 V2-V3 neuralgia Pterional epidural + EAC and UOC Gross total Remission of pain (no therapy) 17 No 8. 67/F l V Intracavernous and cisternal 2.2 × 2.0 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 20 No 9. 33/F r V Intracavernous 2.7 × 2.2 × 2.6 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 17 No 10. 28/F l V Meckel's cave 3.5 × 3.3 × 2.8 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness V2 hypaesthesia 13 At 5 y reoperation 11. 37/F r V Meckel's cave 2.0 × 1.8 × 2.4 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness V2 hypaesthesia 11 No 12. 24/F l V Meckel's cave 3.4 × 2.5 × 1.5 VI nerve palsy Pterional epidural Subtotal Improvement of diplopia 8 No 13. 45/M l V Meckel's cave 2.2 × 2.1 × 1.9 V2 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (no therapy) V2 hypaesthesia 7 No 14. 64/F r V Meckel's cave 2.4 × 2.0 × 2.6 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 3.5 No 15. 67/F l V Meckel's cave 3.6 × 3.0 × 2.8 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 4.5 No 16. 66/M l V Meckel's cave 3.2 × 2.6 × 2.0 V2-V3 neuralgia Pterional epidural Complete Remission of pain (with therapy) facial numbness 6 No 17. 59/M r V Meckel's cave 2.8 × 2.2 × 2.5 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness 8 No 18. 67/F r V Meckel's cave 3.0 × 2.7 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 9 No 19. 72/M r V Meckel's cave 2.7 × 2.4 × 2.5 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 5 No 20. 74/F r V Meckel's cave 3.4 × 2.8 × 3.0 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness 7 No 21. 49/F l V Intracavernous 1.7 × 1.5 × 1.5 V2-V3 neuralgia hypaesthesia Pterional epidural + EAC and UOC Subtotal Remission of pain (no therapy) V2 hypaesthesia 10 No 22. 61/F l V Intracavernous 1.6 × 1.3 × 1.5 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 9 No 23. 55/M l V Meckel's cave 2.0 × 1.8 × 1.7 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 5 No 24. 71/F r V Meckel's cave 3.0 × 2.8 × 1.9 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 14 No N. of case Age/sex Nerve of origin Location Size (cm) Clinical onset Surgical approach Entity of resection Outcome Follow-up (yr) Recurrence 1. 16/F l III Intracavernous and cisternal 1.7 × 1.5 × 1.2 Complete III palsy, proptosis Pterional epidural + intradural + EAC and UOC + grafting Complete Improved III palsy remission of proptosis 20 No 2. 51/F r III Intracavernous 2.0 × 1.8 × 2.0 Complete III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 11 No 3. 38/M r III Intracavernous 2.3 × 1.7 × 2.0 Partial III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 8 No 4. 30/M l VI Cisternal 3.2 × 2.6 × 2.8 Amaurosis, VI nerve palsy Pterional epidural + intradural Subtotal Unchanged 15 At 3 y reoperation 5. 45/F r V Intracavernous 2.5 × 1.8 × 1.4 V2 neuralgia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 16 No 6. 58/F l V Intracavernous and cisternal 2.0 × 2.0 × 3.0 V2-V3 neuralgia hypaesthesia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 18 No 7. 52/M r V Intracavernous 2.7 × 2.5 × 2.2 V2-V3 neuralgia Pterional epidural + EAC and UOC Gross total Remission of pain (no therapy) 17 No 8. 67/F l V Intracavernous and cisternal 2.2 × 2.0 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 20 No 9. 33/F r V Intracavernous 2.7 × 2.2 × 2.6 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 17 No 10. 28/F l V Meckel's cave 3.5 × 3.3 × 2.8 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness V2 hypaesthesia 13 At 5 y reoperation 11. 37/F r V Meckel's cave 2.0 × 1.8 × 2.4 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness V2 hypaesthesia 11 No 12. 24/F l V Meckel's cave 3.4 × 2.5 × 1.5 VI nerve palsy Pterional epidural Subtotal Improvement of diplopia 8 No 13. 45/M l V Meckel's cave 2.2 × 2.1 × 1.9 V2 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (no therapy) V2 hypaesthesia 7 No 14. 64/F r V Meckel's cave 2.4 × 2.0 × 2.6 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 3.5 No 15. 67/F l V Meckel's cave 3.6 × 3.0 × 2.8 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 4.5 No 16. 66/M l V Meckel's cave 3.2 × 2.6 × 2.0 V2-V3 neuralgia Pterional epidural Complete Remission of pain (with therapy) facial numbness 6 No 17. 59/M r V Meckel's cave 2.8 × 2.2 × 2.5 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness 8 No 18. 67/F r V Meckel's cave 3.0 × 2.7 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 9 No 19. 72/M r V Meckel's cave 2.7 × 2.4 × 2.5 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 5 No 20. 74/F r V Meckel's cave 3.4 × 2.8 × 3.0 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness 7 No 21. 49/F l V Intracavernous 1.7 × 1.5 × 1.5 V2-V3 neuralgia hypaesthesia Pterional epidural + EAC and UOC Subtotal Remission of pain (no therapy) V2 hypaesthesia 10 No 22. 61/F l V Intracavernous 1.6 × 1.3 × 1.5 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 9 No 23. 55/M l V Meckel's cave 2.0 × 1.8 × 1.7 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 5 No 24. 71/F r V Meckel's cave 3.0 × 2.8 × 1.9 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 14 No EAC, extradural anterior clinoidectomy; UOC, unroofing of the optic canal; r, right; l, left. View Large TABLE 1. Personal Series of Parasellar Schwannomas N. of case Age/sex Nerve of origin Location Size (cm) Clinical onset Surgical approach Entity of resection Outcome Follow-up (yr) Recurrence 1. 16/F l III Intracavernous and cisternal 1.7 × 1.5 × 1.2 Complete III palsy, proptosis Pterional epidural + intradural + EAC and UOC + grafting Complete Improved III palsy remission of proptosis 20 No 2. 51/F r III Intracavernous 2.0 × 1.8 × 2.0 Complete III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 11 No 3. 38/M r III Intracavernous 2.3 × 1.7 × 2.0 Partial III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 8 No 4. 30/M l VI Cisternal 3.2 × 2.6 × 2.8 Amaurosis, VI nerve palsy Pterional epidural + intradural Subtotal Unchanged 15 At 3 y reoperation 5. 45/F r V Intracavernous 2.5 × 1.8 × 1.4 V2 neuralgia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 16 No 6. 58/F l V Intracavernous and cisternal 2.0 × 2.0 × 3.0 V2-V3 neuralgia hypaesthesia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 18 No 7. 52/M r V Intracavernous 2.7 × 2.5 × 2.2 V2-V3 neuralgia Pterional epidural + EAC and UOC Gross total Remission of pain (no therapy) 17 No 8. 67/F l V Intracavernous and cisternal 2.2 × 2.0 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 20 No 9. 33/F r V Intracavernous 2.7 × 2.2 × 2.6 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 17 No 10. 28/F l V Meckel's cave 3.5 × 3.3 × 2.8 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness V2 hypaesthesia 13 At 5 y reoperation 11. 37/F r V Meckel's cave 2.0 × 1.8 × 2.4 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness V2 hypaesthesia 11 No 12. 24/F l V Meckel's cave 3.4 × 2.5 × 1.5 VI nerve palsy Pterional epidural Subtotal Improvement of diplopia 8 No 13. 45/M l V Meckel's cave 2.2 × 2.1 × 1.9 V2 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (no therapy) V2 hypaesthesia 7 No 14. 64/F r V Meckel's cave 2.4 × 2.0 × 2.6 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 3.5 No 15. 67/F l V Meckel's cave 3.6 × 3.0 × 2.8 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 4.5 No 16. 66/M l V Meckel's cave 3.2 × 2.6 × 2.0 V2-V3 neuralgia Pterional epidural Complete Remission of pain (with therapy) facial numbness 6 No 17. 59/M r V Meckel's cave 2.8 × 2.2 × 2.5 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness 8 No 18. 67/F r V Meckel's cave 3.0 × 2.7 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 9 No 19. 72/M r V Meckel's cave 2.7 × 2.4 × 2.5 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 5 No 20. 74/F r V Meckel's cave 3.4 × 2.8 × 3.0 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness 7 No 21. 49/F l V Intracavernous 1.7 × 1.5 × 1.5 V2-V3 neuralgia hypaesthesia Pterional epidural + EAC and UOC Subtotal Remission of pain (no therapy) V2 hypaesthesia 10 No 22. 61/F l V Intracavernous 1.6 × 1.3 × 1.5 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 9 No 23. 55/M l V Meckel's cave 2.0 × 1.8 × 1.7 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 5 No 24. 71/F r V Meckel's cave 3.0 × 2.8 × 1.9 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 14 No N. of case Age/sex Nerve of origin Location Size (cm) Clinical onset Surgical approach Entity of resection Outcome Follow-up (yr) Recurrence 1. 16/F l III Intracavernous and cisternal 1.7 × 1.5 × 1.2 Complete III palsy, proptosis Pterional epidural + intradural + EAC and UOC + grafting Complete Improved III palsy remission of proptosis 20 No 2. 51/F r III Intracavernous 2.0 × 1.8 × 2.0 Complete III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 11 No 3. 38/M r III Intracavernous 2.3 × 1.7 × 2.0 Partial III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 8 No 4. 30/M l VI Cisternal 3.2 × 2.6 × 2.8 Amaurosis, VI nerve palsy Pterional epidural + intradural Subtotal Unchanged 15 At 3 y reoperation 5. 45/F r V Intracavernous 2.5 × 1.8 × 1.4 V2 neuralgia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 16 No 6. 58/F l V Intracavernous and cisternal 2.0 × 2.0 × 3.0 V2-V3 neuralgia hypaesthesia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 18 No 7. 52/M r V Intracavernous 2.7 × 2.5 × 2.2 V2-V3 neuralgia Pterional epidural + EAC and UOC Gross total Remission of pain (no therapy) 17 No 8. 67/F l V Intracavernous and cisternal 2.2 × 2.0 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 20 No 9. 33/F r V Intracavernous 2.7 × 2.2 × 2.6 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 17 No 10. 28/F l V Meckel's cave 3.5 × 3.3 × 2.8 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness V2 hypaesthesia 13 At 5 y reoperation 11. 37/F r V Meckel's cave 2.0 × 1.8 × 2.4 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness V2 hypaesthesia 11 No 12. 24/F l V Meckel's cave 3.4 × 2.5 × 1.5 VI nerve palsy Pterional epidural Subtotal Improvement of diplopia 8 No 13. 45/M l V Meckel's cave 2.2 × 2.1 × 1.9 V2 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (no therapy) V2 hypaesthesia 7 No 14. 64/F r V Meckel's cave 2.4 × 2.0 × 2.6 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 3.5 No 15. 67/F l V Meckel's cave 3.6 × 3.0 × 2.8 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 4.5 No 16. 66/M l V Meckel's cave 3.2 × 2.6 × 2.0 V2-V3 neuralgia Pterional epidural Complete Remission of pain (with therapy) facial numbness 6 No 17. 59/M r V Meckel's cave 2.8 × 2.2 × 2.5 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness 8 No 18. 67/F r V Meckel's cave 3.0 × 2.7 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 9 No 19. 72/M r V Meckel's cave 2.7 × 2.4 × 2.5 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 5 No 20. 74/F r V Meckel's cave 3.4 × 2.8 × 3.0 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness 7 No 21. 49/F l V Intracavernous 1.7 × 1.5 × 1.5 V2-V3 neuralgia hypaesthesia Pterional epidural + EAC and UOC Subtotal Remission of pain (no therapy) V2 hypaesthesia 10 No 22. 61/F l V Intracavernous 1.6 × 1.3 × 1.5 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 9 No 23. 55/M l V Meckel's cave 2.0 × 1.8 × 1.7 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 5 No 24. 71/F r V Meckel's cave 3.0 × 2.8 × 1.9 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 14 No EAC, extradural anterior clinoidectomy; UOC, unroofing of the optic canal; r, right; l, left. View Large Tumor Origin, Location, and Size Twenty schwannomas arose from the trigeminal nerve (7 intracavernous and 13 within the Meckel's cave), 3 from the oculomotor nerve, and 1 from the abducens nerve. According to the location, 7 schwannomas (5 trigeminal and 2 oculomotor) were purely intracavernous; 4 cases (2 trigeminal, 1 oculomotor, and 1 abducens) were in the cisternal space (with intracavernous extension in 3); finally, 13 trigeminal schwannomas were at the Meckel's cave. The tumor size ranged from 1.6 × 1.3 × 1.5 to 3.6 × 3 × 2.8 cm (Table 1). Clinical Presentation and Diagnosis All 24 patients were symptomatic. Among 20 patients with parasellar trigeminal schwannomas, 19 had facial pain and paresthesia, with variable hypoesthesia in 8 (Tables 1 and 2); 1 patient with Dolenc's type II schwannoma had diplopia due to left sixth nerve paresis as the unique complaint, in absence of symptoms and signs of trigeminal involvement.20 All 19 patients with trigeminal neuralgia had been treated with carbamazepine or oxcarbamazepine at high doses for at least 3 mo, with scarce or no clinical response. TABLE 2. Summary of the Clinical Data and Outcome of 24 Parasellar Schwannomas Tumor location and origin No. of cases Visual deficit Third nerve deficit Sixth nerve deficit Proptosis Facial pain Facial numbness Facial hypoestesia Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Trigeminal intracavernous (Dolenc type I) 7 2 1 – – 1 1 – – 7 – 7 1 3 3 trigeminal cavum Meckeli (Dolenc type II) 13 – – – – 2 1 – – 12 – 12 4 5 3 oculomotor nerve 3 1 1 3 2 – – 3 – – – – – – – Abducens nerve 1 1 1 – – 1 1 – – – – – – – – Tumor location and origin No. of cases Visual deficit Third nerve deficit Sixth nerve deficit Proptosis Facial pain Facial numbness Facial hypoestesia Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Trigeminal intracavernous (Dolenc type I) 7 2 1 – – 1 1 – – 7 – 7 1 3 3 trigeminal cavum Meckeli (Dolenc type II) 13 – – – – 2 1 – – 12 – 12 4 5 3 oculomotor nerve 3 1 1 3 2 – – 3 – – – – – – – Abducens nerve 1 1 1 – – 1 1 – – – – – – – – View Large TABLE 2. Summary of the Clinical Data and Outcome of 24 Parasellar Schwannomas Tumor location and origin No. of cases Visual deficit Third nerve deficit Sixth nerve deficit Proptosis Facial pain Facial numbness Facial hypoestesia Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Trigeminal intracavernous (Dolenc type I) 7 2 1 – – 1 1 – – 7 – 7 1 3 3 trigeminal cavum Meckeli (Dolenc type II) 13 – – – – 2 1 – – 12 – 12 4 5 3 oculomotor nerve 3 1 1 3 2 – – 3 – – – – – – – Abducens nerve 1 1 1 – – 1 1 – – – – – – – – Tumor location and origin No. of cases Visual deficit Third nerve deficit Sixth nerve deficit Proptosis Facial pain Facial numbness Facial hypoestesia Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Trigeminal intracavernous (Dolenc type I) 7 2 1 – – 1 1 – – 7 – 7 1 3 3 trigeminal cavum Meckeli (Dolenc type II) 13 – – – – 2 1 – – 12 – 12 4 5 3 oculomotor nerve 3 1 1 3 2 – – 3 – – – – – – – Abducens nerve 1 1 1 – – 1 1 – – – – – – – – View Large Three cases with oculomotor schwannomas and the case of abducens nerve schwannoma had complete (3 cases) or partial (1 case) palsy of the nerve of origin, with slight proptosis in 3. Radiological Characteristics On preoperative MRI, 17 tumors were isointense and 7 were isohypointense in T1-weighted sequences; all were hyperintense on T2-weighted images. A homogeneous contrast enhancement after gadolinium was evident in 20 cases, whereas 4 showed small cystic component. CT scan, performed in 9 trigeminal schwannomas, showed bony erosion at the Meckel's cave (6 cases) or ovale and rotundum foramina (3 cases). The tumor location (extradural vs intradural, Table 3) was correctly diagnosed on MRI in 22 out of 24 cases, and particularly in all 7 intracavernous trigeminal schwannomas, in all 4 of the oculomotor (Figure 1) and abducens nerves, and in 11 out of 13 trigeminal schwannomas of the Meckel's cave (Figures 2-4); in 2 cases of the last group, the intradural extension could not be defined (Figure 5). FIGURE 1. View largeDownload slide Case 1. Schwannoma of the left oculomotor nerve. MR, postcontrast coronal T1 sequences, A, preoperative, and B, postoperative: small intracavernous enhancing round lesion, which was found to arise from the third cranial nerve at operation by extradural approach. FIGURE 1. View largeDownload slide Case 1. Schwannoma of the left oculomotor nerve. MR, postcontrast coronal T1 sequences, A, preoperative, and B, postoperative: small intracavernous enhancing round lesion, which was found to arise from the third cranial nerve at operation by extradural approach. FIGURE 2. View largeDownload slide Case 13. Trigeminal schwannoma of the Meckel's cave. MR, A-C, preoperative, and D, postoperative Turbo Spin-Echo T1-weighted coronal sections, after contrast medium injection. Presence of a small enhancing mass in left Meckel's cave (arrow), extending to the V3 mandibular nerve and the sensory root (arrow). The tumor is well separated from the ICA by the medial dural wall B. The tumor was interdural (middle fossa), covered by meningeal-periosteal dura, and interperiosteal (infratemporal fossa), covered by periosteum. The interdural location was confirmed intraoperatively by pterional extradural approach. FIGURE 2. View largeDownload slide Case 13. Trigeminal schwannoma of the Meckel's cave. MR, A-C, preoperative, and D, postoperative Turbo Spin-Echo T1-weighted coronal sections, after contrast medium injection. Presence of a small enhancing mass in left Meckel's cave (arrow), extending to the V3 mandibular nerve and the sensory root (arrow). The tumor is well separated from the ICA by the medial dural wall B. The tumor was interdural (middle fossa), covered by meningeal-periosteal dura, and interperiosteal (infratemporal fossa), covered by periosteum. The interdural location was confirmed intraoperatively by pterional extradural approach. FIGURE 3. View largeDownload slide Case 12. Meckel's cave trigeminal schwannoma. MR, A, preoperative, and B, postoperative T1-weighted postcontrast sequence: A, parasellar enhancing mass, which was confirmed as interdural at surgery by an extradural approach; B, well-defined enhancing medial dural wall at the surgical cavity. FIGURE 3. View largeDownload slide Case 12. Meckel's cave trigeminal schwannoma. MR, A, preoperative, and B, postoperative T1-weighted postcontrast sequence: A, parasellar enhancing mass, which was confirmed as interdural at surgery by an extradural approach; B, well-defined enhancing medial dural wall at the surgical cavity. FIGURE 4. View largeDownload slide Case 15. Trigeminal schwannoma. A, Turbo Spin-Echo T2-weighted axial section; B, Turbo Spin-Echo T1-weighted axial section, after contrast medium injection. Dumbbell-shaped low-signal-intensity mass, extending from the Meckel's cave (interdural) to the interpeduncular cistern (subdural) along course of left trigeminal nerve and intensely enhancing after contrast medium injection. The 2 tumor components (interdural and subdural) were confirmed intraoperatively and resected by both extradural and intradural approach. FIGURE 4. View largeDownload slide Case 15. Trigeminal schwannoma. A, Turbo Spin-Echo T2-weighted axial section; B, Turbo Spin-Echo T1-weighted axial section, after contrast medium injection. Dumbbell-shaped low-signal-intensity mass, extending from the Meckel's cave (interdural) to the interpeduncular cistern (subdural) along course of left trigeminal nerve and intensely enhancing after contrast medium injection. The 2 tumor components (interdural and subdural) were confirmed intraoperatively and resected by both extradural and intradural approach. FIGURE 5. View largeDownload slide Case 23. Left parasellar trigeminal schwannoma. MR, A, preoperative, and B, postoperative postcontrast axial sequences: round, inhomogeneus enhancing mass with not well evident medial dural wall. At the extradural surgical exploration small tumor transgression of the medial dural wall was evidenced FIGURE 5. View largeDownload slide Case 23. Left parasellar trigeminal schwannoma. MR, A, preoperative, and B, postoperative postcontrast axial sequences: round, inhomogeneus enhancing mass with not well evident medial dural wall. At the extradural surgical exploration small tumor transgression of the medial dural wall was evidenced The preoperative neuroradiological identification of the nerve of origin was correct in 22 cases, excepting for 1 oculomotor nerve and 1 abducens nerve schwannoma. Surgical Approaches and Technique For all patients, we performed a pterional craniotomy coupled with drilling of the sphenoid wing by extradural route to expose the middle cranial fossa and the cavernous sinus region. The further procedure varied according to the tumor location and origin (Tables 1, 3, and 4). In the 13 cases of trigeminal schwannomas of the Meckel's cave, the dissection of the basal temporal dura mater was carried out after cutting the middle meningeal artery and unroofing the foramina ovale and rotundum by high-speed drill. This technique allowed exposing and mobilizing the whole trigeminal complex and the tumor. After opening the thin external dural layer, the tumor was resected. In 11 out of these 13 cases, the preserved medial dural surface remained extradural. In 2 cases, a dural opening was required to remove the tumor, extended beyond the medial dural wall. The removal was complete in 10 cases and subtotal in 3, because of the intimate adherences with the Gasserian ganglion and V2 root. In 7 cases of intracavernous trigeminal schwannomas, the above-cited extradural approach was carried out to expose the trigeminal complex. Unroofing of the superior orbital fissure was performed in 5 cases, whereas the anterior clinoid process and the roof of the optic canal were removed in 4 cases to expose the medial portion of the cavernous sinus. The resection was complete in all cases, including 2 with small intradural extension. The intradural exploration was not necessary. TABLE 3. Tumor Location, Relationship with the Dura Mater, and Surgical Approach of 24 Parasellar Schwannomas Preoperative MR definition Findings at surgical exploration Surgical approach Tumor location and origin No. of cases Clearly extradural (interdural) Clearly extra-intradural Doubtful intradural extention Extradural (interdural) Extra-intradural Extradural (interdural) Extra-intradural Trigeminal intracavernous (Dolenc type I) 7 5 2 – 5 2 7 – Trigeminal cavum Meckeli (Dolenc type II) 13 9 2 2 9 4 11 2 Oculomotor nerve 3 1 2 – 1 2 2 1 Abducens nerve 1 – 1 – – 1 – 1 Total 24 15 7 2 15 (66.7%) 9 (33.3%) 20 (77.8%) 4 (22.2%) Preoperative MR definition Findings at surgical exploration Surgical approach Tumor location and origin No. of cases Clearly extradural (interdural) Clearly extra-intradural Doubtful intradural extention Extradural (interdural) Extra-intradural Extradural (interdural) Extra-intradural Trigeminal intracavernous (Dolenc type I) 7 5 2 – 5 2 7 – Trigeminal cavum Meckeli (Dolenc type II) 13 9 2 2 9 4 11 2 Oculomotor nerve 3 1 2 – 1 2 2 1 Abducens nerve 1 – 1 – – 1 – 1 Total 24 15 7 2 15 (66.7%) 9 (33.3%) 20 (77.8%) 4 (22.2%) View Large TABLE 3. Tumor Location, Relationship with the Dura Mater, and Surgical Approach of 24 Parasellar Schwannomas Preoperative MR definition Findings at surgical exploration Surgical approach Tumor location and origin No. of cases Clearly extradural (interdural) Clearly extra-intradural Doubtful intradural extention Extradural (interdural) Extra-intradural Extradural (interdural) Extra-intradural Trigeminal intracavernous (Dolenc type I) 7 5 2 – 5 2 7 – Trigeminal cavum Meckeli (Dolenc type II) 13 9 2 2 9 4 11 2 Oculomotor nerve 3 1 2 – 1 2 2 1 Abducens nerve 1 – 1 – – 1 – 1 Total 24 15 7 2 15 (66.7%) 9 (33.3%) 20 (77.8%) 4 (22.2%) Preoperative MR definition Findings at surgical exploration Surgical approach Tumor location and origin No. of cases Clearly extradural (interdural) Clearly extra-intradural Doubtful intradural extention Extradural (interdural) Extra-intradural Extradural (interdural) Extra-intradural Trigeminal intracavernous (Dolenc type I) 7 5 2 – 5 2 7 – Trigeminal cavum Meckeli (Dolenc type II) 13 9 2 2 9 4 11 2 Oculomotor nerve 3 1 2 – 1 2 2 1 Abducens nerve 1 – 1 – – 1 – 1 Total 24 15 7 2 15 (66.7%) 9 (33.3%) 20 (77.8%) 4 (22.2%) View Large TABLE 4. Surgical Bone Steps of the Skull-Base Approach of 24 Parasellar Schwannomas Tumor location and origin No. of cases EAC Unroofing of the optic canal Unroofing of the SOF Unroofing of the foramina ovale and rotondum Trigeminal intracavernous (Dolenc type I) 7 4 4 5 7 Trigeminal cavum Meckeli (Dolenc type II) 13 – – – 13 Oculomotor nerve 3 3 3 3 – Abducens nerve 1 1 – 1 – Tumor location and origin No. of cases EAC Unroofing of the optic canal Unroofing of the SOF Unroofing of the foramina ovale and rotondum Trigeminal intracavernous (Dolenc type I) 7 4 4 5 7 Trigeminal cavum Meckeli (Dolenc type II) 13 – – – 13 Oculomotor nerve 3 3 3 3 – Abducens nerve 1 1 – 1 – EAC, extradural anterior clinoidectomy; SOF, superior orbital fissure View Large TABLE 4. Surgical Bone Steps of the Skull-Base Approach of 24 Parasellar Schwannomas Tumor location and origin No. of cases EAC Unroofing of the optic canal Unroofing of the SOF Unroofing of the foramina ovale and rotondum Trigeminal intracavernous (Dolenc type I) 7 4 4 5 7 Trigeminal cavum Meckeli (Dolenc type II) 13 – – – 13 Oculomotor nerve 3 3 3 3 – Abducens nerve 1 1 – 1 – Tumor location and origin No. of cases EAC Unroofing of the optic canal Unroofing of the SOF Unroofing of the foramina ovale and rotondum Trigeminal intracavernous (Dolenc type I) 7 4 4 5 7 Trigeminal cavum Meckeli (Dolenc type II) 13 – – – 13 Oculomotor nerve 3 3 3 3 – Abducens nerve 1 1 – 1 – EAC, extradural anterior clinoidectomy; SOF, superior orbital fissure View Large TABLE 5. Correlation Between Entity of Resection and Surgical Approach (Extradural vs Extra-Intradural) Entity of resection Tumor location and origin No. of cases Surgical approach Gross total Subtotal Trigeminal, intracavernous 5 Extradural 5 5 – Extra-intradural – – – Trigeminal, Meckel's cave 15 Extradural 13 9 4 Extra-intradural 2 2 – Oculomotor nerve 3 Extradural 5 2 – Extra-intradural – 1 – Abducens nerve 1 Extradural – – – Extra-intradural 1 – 1 Entity of resection Tumor location and origin No. of cases Surgical approach Gross total Subtotal Trigeminal, intracavernous 5 Extradural 5 5 – Extra-intradural – – – Trigeminal, Meckel's cave 15 Extradural 13 9 4 Extra-intradural 2 2 – Oculomotor nerve 3 Extradural 5 2 – Extra-intradural – 1 – Abducens nerve 1 Extradural – – – Extra-intradural 1 – 1 EAC, extradural anterior clinoidectomy; SOF, superior orbital fissure. View Large TABLE 5. Correlation Between Entity of Resection and Surgical Approach (Extradural vs Extra-Intradural) Entity of resection Tumor location and origin No. of cases Surgical approach Gross total Subtotal Trigeminal, intracavernous 5 Extradural 5 5 – Extra-intradural – – – Trigeminal, Meckel's cave 15 Extradural 13 9 4 Extra-intradural 2 2 – Oculomotor nerve 3 Extradural 5 2 – Extra-intradural – 1 – Abducens nerve 1 Extradural – – – Extra-intradural 1 – 1 Entity of resection Tumor location and origin No. of cases Surgical approach Gross total Subtotal Trigeminal, intracavernous 5 Extradural 5 5 – Extra-intradural – – – Trigeminal, Meckel's cave 15 Extradural 13 9 4 Extra-intradural 2 2 – Oculomotor nerve 3 Extradural 5 2 – Extra-intradural – 1 – Abducens nerve 1 Extradural – – – Extra-intradural 1 – 1 EAC, extradural anterior clinoidectomy; SOF, superior orbital fissure. View Large All 4 cases of oculomotor and abducens nerve schwannomas were approached by a first extradural step, drilling the sphenoid wing and anterior clinoid process, and unroofing the superior orbital fissure. The 3 cases of intracavernous schwannoma of the oculomotor nerve also required optic canal unroofing. In 2 of them, the extradural approach allowed complete tumor resection. In another (case 1) with cisternal extension, intradural exploration was necessary. In this patient, the nerve segment in the lateral wall of the cavernous sinus was found to be enlarged by the tumor, whereas the cisternal segment was normal. Thus, en bloc resection of the tumor and reconstruction of the upper and lower stump by a sural nerve graft reinforced by fibrin glue were realized. The abducens nerve schwannoma located at the cisternal segment of the nerve was removed by an extra-intradural approach. Thus, complete tumor resection was achieved in 19 out of 24 cases (80%), and subtotal resection in 5 (20%). The correlation between entity of resection and surgical approach (Table 5) showed that gross total resection was achieved in 16 out of 20 (80%) tumors treated by extradural approach, and in 3 out of 4 (75%) after extra-intradural approach. Among 5 cases treated by subtotal resection, 4 were trigeminal schwannomas of type 1 (1 case) or type 2 (3 cases), and 1 was an abducens schwannoma. In these cases, the maximum tumor diameter was >3 cm in 4 out of 5 cases, whereas a strong adherence to the nerve was found in 2 cases. Outcome There were no surgical mortality or postoperative major complications. The neurological outcome was as follows (Tables 1 and 2). Among 3 oculomotor nerve schwannomas, the nerve palsy improved in the case treated by nerve grafting and was unchanged in 2 others; the exophthalmos disappeared in all. In the case of abducens nerve schwannoma, the nerve palsy was unchanged postoperatively. All 19 patients with trigeminal schwannomas and facial pain were treated with medical therapy for 1 to 3 mo after surgery. Remission of the facial pain was obtained in all cases, with no further therapy in 14. Five patients still need low doses of oxcarbazepine and complain of residual facial numbness. Facial hypesthesia of V2 and/or V3 disappeared only in 2 among 8 cases in which it was noticed preoperatively. In case 12 with trigeminal schwannoma of the Meckel's cave and isolated sixth nerve palsy, it slightly improved after surgery. Among 5 patients who underwent subtotal resection, 1 with more significant residual nodule was treated by radiosurgery. The other 4 with very small enhancing nodule were followed up with serial MRI; among them, 1 is stable after 6 yr, another has recently been treated by radiosurgery 5 yr after the initial operation, and 2 others experienced recurrence at 3 and 5 yr, respectively, and were reoperated on. Among 2 patients with recurrence, 1 (case 4), a 30-yr-old man with left abducens nerve schwannoma, was reoperated on 3 yr after the initial surgery through the previous approach for significant regrowth; complete resection was obtained. The second patient (case 10), a 28-yr-old woman with recurrent intradural trigeminal schwannoma of the Meckel's cave and facial pain 5 yr after subtotal resection by extradural route, was reoperated on through a pterional extra-intradural approach with complete resection. In both patients, the second surgery was preferred because of their young age. DISCUSSION Most Meckel's cave and intracavernous trigeminal schwannomas and intracavernous schwannomas of the oculomotor nerve have extradural (“interdural”) location.21-24 Thus, strictly intracavernous and Meckel's cave schwannomas are well separated from the cranial nerves and internal carotid artery (ICA) by the internal dural layer. On the other hand, those with significant cisternal extension and cisternal schwannomas of the oculomotor and abducens nerves lie close to the intradural ICA and cranial nerves in the cisternal space. Clinical and Radiological Definition The nerve of origin may preoperatively be identified by both clinical presentation and tumor location. The clinical presentation of trigeminal schwannomas may often be deceptive. Trigeminal nerve symptoms are present at clinical onset in only half of the cases,4 and often occur later; in addition, no evidence of trigeminal nerve dysfunction is reported in 10%20 to 56%25 of trigeminal schwannomas. It may be presumed that in some cases, the tumor may leave most trigeminal nerve fibers intact, mainly in cases of tumors of the Gasserian ganglion. Diplopia and eye movement dysfunction are reported in 6% to 34% of the patients with trigeminal schwannomas (in 10% as the initial complaint).4 An isolated diplopia due to abducens nerve palsy as the unique symptom was reported in 3 previous cases,25-26 and in one of our patients.20 Unlike trigeminal schwannomas, tumors arising from the oculomotor and abducens nerves almost invariably present with diplopia and objective signs of eye movement dysfunction.8,11,15 The very thin structure and vulnerability of these nerves may explain their early anatomic and functional involvement during tumor growth. Symptoms of dysfunction of the nerve of origin were the first clinical manifestation in 23 out of 24 patients in our series. The preoperative neuroradiological definition of parasellar schwannomas includes tumor location, its relationships with the dura (extradural, extra-intradural, cisternal), and the identification of the nerve of origin. The tumor location may be defined on 3-D gradient echo steady-state sequences of MRI. With this imaging technique, neural structures, vessels, and dura are visualized as low-signal intensity in the CSF hyperintensity.27-28 In this way, the SSFP sequences are superior to the conventional T2-weighted sequences in visualizing the cisternal cranial nerves and cavernous sinus (Figure 6).29-31 SSFP sequences of MR evidence small- and middle-size parasellar schwannomas as a hypo- or isointense mass, well defined by the high signal intensity of the CSF. Unfortunately, in larger tumors, the relationships with the surrounding CSF signal may not be visible. FIGURE 6. View largeDownload slide MR, 3-D CISS (Constructive Interference in Steady State) for the anatomic definition of the parasellar region and trigeminal cistern in a normal case. A, Section on axial plane at the level of the upper part of the cerebello-pontine cistern. The normal course of the fifth cranial nerve is clearly evident, from the point at which the nerve arises (REZ), to the Meckel's space (arrow); a hyperintense signal due to the presence of CSF forming a true cistern and curved in a hypointense dural fold is evident. B, Right parasagittal reconstruction. The whole course of the fifth nerve is demonstrated (arrow) from the REZ to the Meckel's space. FIGURE 6. View largeDownload slide MR, 3-D CISS (Constructive Interference in Steady State) for the anatomic definition of the parasellar region and trigeminal cistern in a normal case. A, Section on axial plane at the level of the upper part of the cerebello-pontine cistern. The normal course of the fifth cranial nerve is clearly evident, from the point at which the nerve arises (REZ), to the Meckel's space (arrow); a hyperintense signal due to the presence of CSF forming a true cistern and curved in a hypointense dural fold is evident. B, Right parasagittal reconstruction. The whole course of the fifth nerve is demonstrated (arrow) from the REZ to the Meckel's space. FIGURE 7. View largeDownload slide Choice of the surgical approach according to the neuroradiological findings. FIGURE 7. View largeDownload slide Choice of the surgical approach according to the neuroradiological findings. In this series, the correct definition (preservation vs transgression of the medial dural wall) was obtained in 22 out of 24 patients; in 2 large trigeminal schwannomas of the Meckel's cave, the intradural tumor extension was suspected on MRI but not confirmed during surgery. MRI may also suggest the tumor's nerve of origin. Trigeminal schwannomas of the Meckel's cave are diagnosed because of relationships with the bone and dural structures and enlargement of the foramina ovale and/or rotundum.32 For pure intracavernous schwannomas, the identification of the nerve origin is difficult, or even impossible, and may be determined only with clinical data. Finally, cisternal and cavernous-cisternal schwannomas of the oculomotor and abducens nerves may be diagnosed on MRI from the pattern of tumor growth along the cistern.33 MR with diffusion tensor tractography has recently been introduced to identify the cranial nerves,34 mainly the facial-acoustic complex around vestibular schwannomas.35-36 A recent study37 has explored the cranial nerves in relationship with trigeminal schwannomas. This technique seems useful for identifying the nerve of origin of parasellar schwannomas. Surgical Approach and Technique Parasellar schwannomas have been treated by different surgical approaches, including pterional frontotemporal intradural or extra-intradural,4,8,11 and subtemporal intradural or extra-intradural,38-42 eventually with resection of the orbitozygomatic process. The frontotemporal extradural approach introduced by Dolenc18 allows good extradural-interdural exposure of the trigeminal complex. The Meckel's cave, the trigeminal branches, and the cavernous sinus are well exposed by rotating the trajectory anteriorly, and most schwannomas of this region may be resected.43-44 The extradural approach avoids several risks, including brain retraction, sacrifice of temporal bridging veins, and cranial nerve deficits. The indication to pterional extradural approach vs an extradural-intradural approach depends on the origin, location, and size of the schwannoma. The preoperative neuroradiological identification of the tumor location (extradural or extra-intradural Meckel's cave, cavernous sinus, and parasellar cistern) may be helpful in planning the surgical approach (Figure 7). If the tumor is exclusively extradural (Meckel's cave, cavernous sinus), the extradural route of the pterional approach is sufficient in order to expose and remove the whole tumor mass. If the tumor is extra-intradural or cisternal (as Meckel's cave and cavernous schwannomas with dural transgression or cisternal schwannomas) after the extradural step, the dural opening allows complete control of the tumor. Most Dolenc's type II trigeminal schwannomas have an interdural location with preserved medial dural wall, as in all but 2 patients in our series. In these cases, an extended pterional extradural approach allows exposing and removing the schwannoma. If transgression of the medial dural layer and significant intradural tumor component are evidenced at the end of the extradural resection, the tumor removal may be completed by intradural exploration. Dolenc's type I intracavernous trigeminal schwannomas are resected through the above depicted route. The extradural tumor dissection is facilitated by the areolar tissue plane between the dura and the outer membrane of the cavernous sinus. Drilling of the anterior clinoid process must be performed in cases in which the exposure of the medial portion of the cavernous sinus is necessary.45 Interdural and intracavernous schwannomas of the oculomotor and abducens nerves may be approached by a pterional extradural route, coupled with anterior clinoidectomy. In such cases, the tumor grows within a dural cuff, allowing dissection from the lateral wall of the cavernous sinus, while preserving the integrity of the intracavernous structures. However, most schwannomas of the oculomotor and abducens nerves lie within the cistern or extend from the cavernous sinus to the cisternal space. In these cases, intradural exploration is necessary to obtain sufficient exposure of the cisternal portion of the tumor. Surgery vs Radiosurgery Radiosurgery is a safe technique for treating intracranial schwannomas. In a series of 36 patients with nonvestibular schwannomas treated by Gamma Knife, Elsharkawy46 found tumors to decrease in 56%, increase in 19%, and remain stable in 25%, with an overall tumor control of 80.6%.46 In a review of 9 reported series (including 4 overall nonacoustic schwannomas,47-50 2 trigeminal schwannomas,51-52 1 oculomotor schwannoma,15 and 1 jugular foramen schwannoma53) for a total of more than 200 patients, they found 2- and 5-yr progression-free survival times of 91% and 78%, respectively. Similar results were found in other radiosurgical series of trigeminal54 and abducens nerve schwannomas.14 The recurrence rate of several surgical series of trigeminal schwannomas is low, ranging from 0% to 7.4%,1-4,44 except for large or intra-extracranial tumors (14%).55 In agreement with others,3,44 we treat symptomatic trigeminal and oculomotor schwannomas by surgery at our institution. This selected group of schwannomas may usually be removed by pterional extradural approach with no manipulation of other cranial nerves and low risk of neurological deficits. CONCLUSION The surgical treatment of parasellar schwannomas may be planned on the preoperative MRI findings. The pterional extradural approach is usually sufficient for intracavernous and Meckel's cave trigeminal schwannomas; an intradural exploration is necessary for tumors with significant transgression of the medial dural wall. The rare intracavernous schwannomas of the oculomotor and abducens nerves may also be approached through a pterional extradural route; cases with cisternal or cavernous-cisternal location require the intradural approach to achieve exposure of the tumor. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Chowdhury FH , Haque MR , Kawsar KA , Sarker MH , Hasan M , Goel AH . Intracranial nonvestibular neurinomas: young neurosurgeons' experience . J Neurosci Rural Pract . 2014 ; 5 ( 3 ): 231 - 243 . Google Scholar CrossRef Search ADS PubMed 2. Goel A , Muzumdar D , Raman C . Trigeminal neuroma: analysis of surgical experience with 73 cases . Neurosurgery . 2003 ; 52 ( 4 ): 783 - 790 ; discussion 790 . Google Scholar CrossRef Search ADS PubMed 3. Pamir MN , Peker S , Bayrakli F , Kilic T , Ozek MM . Surgical treatment of trigeminal schwannomas . Neurosurg Rev . 2007 ; 30 ( 4 ): 329 - 337 ; discussion 337 . Google Scholar CrossRef Search ADS PubMed 4. Samii M , Migliori MM , Tatagiba M , Babu R . Surgical treatment of trigeminal schwannomas . J Neurosurg . 1995 ; 82 ( 5 ): 711 - 718 . Google Scholar CrossRef Search ADS PubMed 5. Cho YH , Sung KS , Song YJ , Kim DC , Choi S , Kim KU . Oculomotor nerve schwannoma: a case report . Brain Tumor Res Treat . 2014 ; 2 ( 1 ): 43 - 47 . Google Scholar CrossRef Search ADS PubMed 6. Mariniello G , Horvat A , Dolenc VV . En bloc resection of an intracavernous oculomotor nerve schwannoma and grafting of the oculomotor nerve with sural nerve. Case report and review of the literature . J Neurosurg . 1999 ; 91 ( 6 ): 1045 - 1049 . Google Scholar CrossRef Search ADS PubMed 7. Prabhu SS , Bruner JM . Large oculomotor schwannoma presenting as a parasellar mass: a case report and literature review . Surg Neurol Int . 2010 ; 1 ( 1 ): 15 . Google Scholar CrossRef Search ADS PubMed 8. Tanriover N , Kemerdere R , Kafadar AM , Muhammedrezai S , Akar Z . Oculomotor nerve schwannoma located in the oculomotor cistern . Surg Neurol . 2007 ; 67 ( 1 ): 83 - 88 ; discussion 88 . Google Scholar CrossRef Search ADS PubMed 9. Acharya R , Husain S , Chhabra SS , Patir R , Bhalla S , Seghal AD . Sixth nerve schwannoma: a case report with literature review . Neurol Sci . 2003 ; 24 ( 2 ): 74 - 79 . Google Scholar PubMed 10. Nakamura M , Carvalho GA , Samii M . Abducens nerve schwannoma: a case report and review of the literature . Surg Neurol . 2002 ; 57 ( 3 ): 183 - 188 ; discussion 188-189 . Google Scholar CrossRef Search ADS PubMed 11. Park JH , Cho YH , Kim JH , Lee JK , Kim CJ . Abducens nerve schwannoma: case report and review of the literature . Neurosurg Rev . 2009 ; 32 ( 3 ): 375 - 378 ; discussion 378 . Google Scholar CrossRef Search ADS PubMed 12. Williams LS , Schmalfuss IM , Sistrom CL et al. MR imaging of the trigeminal ganglion, nerve, and the perineural vascular plexus: normal appearance and variants with correlation to cadaver specimens . AJNR Am J Neuroradiol . 2003 ; 24 ( 7 ): 1317 - 1323 . Google Scholar PubMed 13. Erlich SA , Tymianski M , Kiehl TR . Cellular schwannoma of the abducens nerve: case report and review of the literature . Clin Neurol Neurochir . 2009 ; 111 ( 5 ): 467 - 471 . Google Scholar CrossRef Search ADS 14. Prasad GL , Sharma MS , Kale SS , Agrawal D , Singh M , Sharma BS . Gamma knife radiosurgery in the treatment of abducens nerve schwannomas: a retrospective study . J Neurosurg 2016 ; 125 ( 4 ): 832 - 837 . Google Scholar CrossRef Search ADS PubMed 15. Kim IY , Kondziolka D , Niranjan A , Flickinger JC , Lunsford LD . Gamma Knife surgery for schwannomas originating from cranial nerves III, IV, and VI . J Neurosurg . 2008 ; 109 ( suppl ): 149 - 153 . Google Scholar PubMed 16. Hatae R , Miyazono M , Kohri R , Maeda K , Naito S . Trochlear nerve schwannoma with intratumoral hemorrhage presenting with persistent hiccups: a case report . J Neurol Surg Rep . 2014 ; 75 ( 1 ): e183 - e188 . Google Scholar CrossRef Search ADS PubMed 17. Boucher AB , Michael LM . The middle fossa approach for the removal of a trochlear schwannoma . Case Rep Neurol Med . 2014 ; 2014 : 672314 . Google Scholar PubMed 18. Dolenc VV . Frontotemporal epidural approach to trigeminal neurinomas . Acta Neurochir (Wien) . 1994 ; 130 ( 1-4 ): 55 - 65 . Google Scholar CrossRef Search ADS PubMed 19. Celli P , Ferrante L , Acqui M , Mastronardi L , Fortuna A , Palma L . Neurinoma of the third, fourth, and sixth cranial nerves: a survey and report of a new fourth nerve case . Surg Neurol . 1992 ; 38 ( 3 ): 216 - 224 . Google Scholar CrossRef Search ADS PubMed 20. Mariniello G , Giamundo A , Seneca V , Maiuri F . Abducens nerve palsy as the unique sign of a trigeminal schwannoma . Clin Neurol Neurosurg . 2013 ; 115 ( 7 ): 1121 - 1122 . Google Scholar CrossRef Search ADS PubMed 21. Harris FS , Rhoton AL . Anatomy of the cavernous sinus. A microsurgical study . J Neurosurg . 1976 ; 45 ( 2 ): 169 - 180 . Google Scholar CrossRef Search ADS PubMed 22. Dolenc VV . The Cavernous Sinus: A Multidisciplinary Approach to Vascular and Tumorous Lesions . New York : Springer ; 1987 . 23. Rhoton AL Jr . The cavernous sinus, the cavernous venous plexus, and the carotid collar . Neurosurgery . 2002 ; 51 ( 4 suppl ): S375 - S410 . Google Scholar PubMed 24. Goel A , Shah A . “Interdural” oculomotor neurinoma: report of two surgically treated cases . Acta Neurochir (Wien) . 2010 ; 152 ( 10 ): 1721 - 1724 . Google Scholar CrossRef Search ADS PubMed 25. Majoie CB , Hulsmans FJ , Castelijns JA et al. Primary nerve-sheath tumours of the trigeminal nerve: clinical and MRI findings . Neuroradiology . 1999 ; 41 ( 2 ): 100 - 108 . Google Scholar CrossRef Search ADS PubMed 26. Yamashita J , Asato R , Handa H , Nakao S , Ogata M . Abducens nerve palsy as initial symptom of trigeminal schwannoma . J Neurol Neurosurg Psychiatry . 1977 ; 40 ( 12 ): 1190 - 1197 . Google Scholar CrossRef Search ADS PubMed 27. Ciftci E , Anik Y , Arslan A , Akansel G , Sarisoy T , Demirci A . Driven equilibrium (drive) MR imaging of the cranial nerves V-VIII: comparison with the T2-weighted 3D TSE sequence . Eur J Radiol . 2004 ; 51 ( 3 ): 234 - 240 . Google Scholar CrossRef Search ADS PubMed 28. Yousry I , Moriggl B , Holtmannspoetter M , Schmid UD , Naidich TP , Yousry TA . Detailed anatomy of the motor and sensory roots of the trigeminal nerve and their neurovascular relationships: a magnetic resonance imaging study . J Neurosurg . 2004 ; 101 ( 3 ): 427 - 434 . Google Scholar CrossRef Search ADS PubMed 29. Hatipoglu HG , Durakoglugil T , Ciliz D , Yuksel E . Comparison of FSE T2W and 3D FIESTA sequences in the evaluation of posterior fossa cranial nerves with MR cisternography . Diagn Interv Radiol . 2007 ; 13 ( 2 ): 56 - 60 . Google Scholar PubMed 30. Seitz J , Held P , Strotzer M et al. MR imaging of cranial nerve lesions using six different high-resolution T1- and T2(*)-weighted 3D and 2D sequences . Acta Radiol . 2002 ; 43 ( 4 ): 349 - 353 . Google Scholar CrossRef Search ADS PubMed 31. Osborn A . Osborn's Brain: Imaging, Pathology and Anatomy . 1st ed . Salt Lake City, Utah : Amirsys ; 2013 : 613 - 644 . 32. Zhang L , Yang Y , Xu S , Wang J , Liu Y , Zhu S . Trigeminal schwannomas: a report of 42 cases and review of the relevant surgical approaches . Clin Neurol Neurosurg . 2009 ; 111 ( 3 ): 261 - 269 . Google Scholar CrossRef Search ADS PubMed 33. Lingawi SS . Oculomotor nerve schwannoma: MRI appearance . Clin Imaging . 2000 ; 24 ( 2 ): 86 - 88 . Google Scholar CrossRef Search ADS PubMed 34. Hodaie M , Quan J , Chen DQ . In vivo visualization of cranial nerve pathways in humans using diffusion-based tractography . Neurosurgery . 2010 ; 66 ( 4 ): 788 - 795 ; discussion 795-796 . Google Scholar CrossRef Search ADS PubMed 35. Chen DQ , Quan J , Guha A , Tymianski M , Mikulis D , Hodaie M . Three-dimensional in vivo modeling of vestibular schwannomas and surrounding cranial nerves with diffusion imaging tractography . Neurosurgery . 2011 ; 68 ( 4 ): 1077 - 1083 . Google Scholar CrossRef Search ADS PubMed 36. Gerganov VM , Giordano M , Samii M , Samii A . Diffusion tensor imaging-based fiber tracking for prediction of the position of the facial nerve in relation to large vestibular schwannomas . J Neurosurg . 2011 ; 115 ( 6 ): 1087 - 1093 . Google Scholar CrossRef Search ADS PubMed 37. Wei PH , Qi ZG , Chen G et al. Identification of cranial nerves around trigeminal schwannomas using diffusion tensor tractography: a technical note and report of 3 cases . Acta Neurochir (Wien) . 2016 ; 158 ( 3 ): 429 - 435 . Google Scholar CrossRef Search ADS PubMed 38. el-Kalliny M , van Loveren H , Keller JT , Tew JM Jr . Tumors of the lateral wall of the cavernous sinus . J Neurosurg . 1992 ; 77 ( 4 ): 508 - 514 . Google Scholar CrossRef Search ADS PubMed 39. Konovalov AN , Spallone A , Mukhamedjanov DJ , Tcherekajev VA , Makhmudov UB . Trigeminal neurinomas. A series of 111 surgical cases from a single institution . Acta Neurochir (Wien) . 1996 ; 138 ( 9 ): 1027 - 1035 . Google Scholar CrossRef Search ADS PubMed 40. Goel A , Nadkarni T . Basal lateral subtemporal approach for trigeminal neurinomas: report of an experience with 18 cases . Acta Neurochir (Wien) . 1999 ; 141 ( 7 ): 711 - 719 . Google Scholar CrossRef Search ADS PubMed 41. Sharma BS , Ahmad FU , Chandra PS , Mahapatra AK . Trigeminal schwannomas: experience with 68 cases . J Clin Neurosci . 2008 ; 15 ( 7 ): 738 - 743 . Google Scholar CrossRef Search ADS PubMed 42. Srinivas D , Somanna S , Ashwathnarayana CB , Bhagavatula ID . Multicompartmental trigeminal schwannomas: management strategies and outcome . Skull Base . 2011 ; 21 ( 6 ): 351 - 358 . Google Scholar CrossRef Search ADS PubMed 43. Day JD , Fukushima T , Giannotta SL . Microanatomical study of the extradural middle fossa approach to the petroclival and posterior cavernous sinus region: description of the rhomboid construct . Neurosurgery . 1994 ; 34 ( 6 ): 1009 - 1016 ; discussion 1016 . Google Scholar PubMed 44. Day JD , Fukushima T . The surgical management of trigeminal neuromas . Neurosurgery . 1998 ; 42 ( 2 ): 233 - 240 ; discussion 240-241 . Google Scholar CrossRef Search ADS PubMed 45. Mariniello G , Cappabianca P , Buonamassa S , de Divitiis E . Surgical treatment of intracavernous trigeminal schwannomas via a fronto-temporal epidural approach . Clin Neurol Neurosurg . 2004 ; 106 ( 2 ): 104 - 109 . Google Scholar CrossRef Search ADS PubMed 46. Elsharkawy M , Xu Z , Schlesinger D , Sheehan JP . Gamma knife surgery for nonvestibular schwannomas: radiological and clinical outcomes . J Neurosurg . 2012 ; 116 ( 1 ): 66 - 72 . Google Scholar CrossRef Search ADS PubMed 47. Pollock BE , Foote RL , Stafford SL . Stereotactic radiosurgery: the preferred management for patients with nonvestibular schwannomas? Int J Radiat Oncol Biol Phys . 2002 ; 52 ( 4 ): 1002 - 1007 . Google Scholar CrossRef Search ADS PubMed 48. Hamm KD , Gross MW , Fahrig A et al. Stereotactic radiotherapy for the treatment of nonacustic schwannomas . Neurosurgery . 2008 ; 62 ( suppl 5 ): A29 - A36 . Google Scholar CrossRef Search ADS PubMed 49. Showalter TN , Werner-Wasik M , Curran WJ Jr , Friedman DP , Xu X , Andrews DW . Stereotactic radiosurgery and fractionated stereotactic radiotherapy for the treatment of nonacoustic cranial nerve schwannomas . Neurosurgery . 2008 ; 63 ( 4 ): 734 - 740 . Google Scholar CrossRef Search ADS PubMed 50. Nishioka K , Abo D , Aoyama H et al. Stereotactic radiotherapy for intracranial nonacoustic schwannomas including facial nerve schwannoma . Int J Radiat Oncol Biol Phys . 2009 ; 75 ( 5 ): 1415 - 1419 . Google Scholar CrossRef Search ADS PubMed 51. Pan L , Wang EM , Zhang N et al. Long-term results of Leksell gamma knife surgery for trigeminal schwannomas . J Neurosurg . 2005 ; 102 ( suppl ): 220 - 224 . Google Scholar CrossRef Search ADS 52. Sheehan J , Yen CP , Arkha Y , Schlesinger D , Steiner L . Gamma knife surgery for trigeminal schwannoma . J Neurosurg . 2007 ; 106 ( 5 ): 839 - 845 . Google Scholar CrossRef Search ADS PubMed 53. Zhang N , Pan L , Dai JZ , Wang BJ , Wang EM , Cai PW . J Neurosurg . 2002 ; 97 ( suppl 5 ): 456 - 458 . PubMed 54. Kano H , Niranjan A , Kondziolka D , Flickinger JC , Dade Lunsford L . Stereotactic radiosurgery for trigeminal schwannoma: tumor control and functional preservation . J Neurosurg . 2009 ; 110 ( 3 ): 553 - 558 . Google Scholar CrossRef Search ADS PubMed 55. Goel A , Shah A , Muzumdar D , Nadkarni T , Chagla A . Trigeminal neurinomas with extracranial extension: analysis of 28 surgically treated cases . J Neurosurg . 2010 ; 113 ( 5 ): 1079 - 1084 . Google Scholar CrossRef Search ADS PubMed COMMENT The authors present a review of their surgical experience with 24 patients with parasellar schwannomas including 20 of the trigeminal nerve, 3 of the oculomotor nerve, and 1 of the abducens nerve. The surgical technique used to approach these lesions is well described and illustrated with pre- and postoperative imaging. The authors describe their methods for using the preoperative imaging findings to predict whether the surgical approach will be entirely extradural, or whether an intradural exposure would be needed as well. The patient outcomes in this series of patients are excellent. The authors’ experience with these types of lesions serves as a guide to the surgeon approaching these types of tumor. That said, certainly some of the small to medium sized tumors in this series possibly could have been well treated quite effectively with stereotactic radiosurgery instead. Michael Chicoine St. Louis, Missouri Copyright © 2017 by the Congress of Neurological Surgeons This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Operative Neurosurgery Oxford University Press

Parasellar Schwannomas: Extradural vs Extra-Intradural Surgical Approach

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Congress of Neurological Surgeons
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Copyright © 2017 by the Congress of Neurological Surgeons
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2332-4252
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2332-4260
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10.1093/ons/opx174
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Abstract

Abstract BACKGROUND Schwannomas of the parasellar region may arise from the trigeminal, oculomotor, trochlear, and abducens nerves. OBJECTIVE To define the tumor origin, location, and dural relationship (extradural vs extra-intradural vs cisternal) on preoperative magnetic resonance imaging (MRI), in order to plan the best surgical approach (purely extradural vs extra-intradural). METHODS Twenty-four patients with parasellar schwannomas who underwent surgery were retrospectively analyzed. Twenty arose from the trigeminal nerve (7 intracavernous and 13 within the Meckel's cave), 3 from the oculomotor nerve, and 1 from the abducens nerve. The preoperative identification of the tumor location (extradural vs extra-intradural vs cisternal) and the nerve of origin was defined on MR sequences. All patients were operated on through a pterional approach (extradural or extra-intradural route). RESULTS The tumor location was correctly defined on MRI in 22 out of 24 cases (92%) and the nerve of origin in 22 (92%). An extradural approach without intradural exploration was performed in all 5 intracavernous trigeminal schwannomas, in 11 out of 13 of the Meckel's cave, and in 2 schwannomas of the oculomotor nerve. Two schwannomas of the Meckel's cave with transgression of the medial dural wall, 1 of the oculomotor nerve, and the abducens nerve schwannoma required an extra-intradural approach. Complete tumor resection was obtained in 19 out of 24 cases (80%). CONCLUSION The pterional extradural approach is sufficient for Dolenc type I and II trigeminal schwannomas, excepting for those transgressing the inner dural layer. Schwannomas of the oculomotor and abducens nerves with cisternal location require an extradural-intradural approach. Abducens nerve schwannoma, Magnetic resonance, Oculomotor nerve schwannoma, Skull base approach, Trigeminal nerve schwannoma ABBREVIATIONS ABBREVIATIONS CSF cerebrospinal fluid CT computed tomography ICA internal carotid artery MRI magnetic resonance imaging SSFP steady-state free procession Parasellar schwannomas may arise from the third, fourth, fifth, and sixth cranial nerves. Among them, trigeminal schwannomas are more frequent (0.8%-8% of all intracranial schwannomas),1-4 whereas those of the oculomotor (36 reported cases),5-8 abducens (25 cases),9-14 and trochlear (40 cases)15-17 nerves are quite rare. We have retrospectively analyzed 24 patients who underwent surgery for parasellar schwannomas. The aim of this study was to discuss the preoperative neuroradiological definition of the tumor location (extradural vs intra-extradural vs cisternal) and its role to plan the best surgical approach (pterional vs extradural vs extra-intradural). No previous studies have stressed this aspect. METHODS Twenty-four patients with schwannomas of the parasellar region who underwent surgical treatment at our neurosurgical clinic between 1995 and 2012 are included in the study. Cases extending outside the parasellar region (in the infratemporal and posterior fossae), those with insufficient clinical data, and those lost to follow-up were excluded. An ethics committee was not necessary because this is a retrospective study; however, all patients gave their consent for the use of all data. Case records, preoperative imaging studies, surgical descriptions, and postoperative clinical and radiological follow-up checks were reviewed. Detailed clinical, neurological, and ophthalmological examinations were done in each case. The preoperative neuroimaging studies included magnetic resonance imaging (MRI) with T1 basal and postcontrast sequences, T2 sequences, and 3-D gradient echo steady-state sequences in all cases. Six trigeminal schwannomas were also studied by 3-D computed tomography (CT) scan for defining the bone changes. The MR and CT images were reviewed by a neuroradiologist. The radiological variables assessed to determine the tumor location and its relationships with the dura and cisternal space included the following: (a) the evidence of the medial wall of the middle fossa in postcontrast axial and coronal images; (b) the shape of the medial tumor margins (smooth vs irregular); and (c) the relationship of the isohypointense tumor in the high-signal intensity of the cerebrospinal fluid (CSF) in axial and coronal T2-weighted images and steady-state free procession (SSFP) sequences. The tumor size was defined on postcontrast MRI sequences by measuring 3 linear dimensions (length, width, and height). The parasellar schwannomas arose from the trigeminal, oculomotor, and abducens nerves. Trigeminal schwannomas were classified, according to the classification of Dolenc,18 as type I (cavernous sinus) or type II (Meckel's cave). Schwannomas of the oculomotor and abducens nerves were classified in 3 types: cavernous, cisternal, and cisterno-cavernous.19 All patients were operated on through pterional craniotomy and skull base approach according to the tumor location and extension. In all cases, the diagnosis of schwannoma was confirmed by the histological studies and immunohistochemical staining (S100 protein). Postoperative evaluation and follow-up checks included clinical examination and MRI at 1 mo, 6 mo, 1 yr, and then every 3 yr. The extent of resection was determined on postoperative postcontrast MRI. The resection was defined as complete when no contrast enhancement was evidenced, and subtotal when the residual nodule was less than 10% of the initial tumor size. The actual follow-up ranges from 3.5 to 20 yr (average 11 yr). Factors that were considered include symptoms of clinical onset, tumor location and dural relationships, nerve of origin, type of surgical approach, entity of surgical resection, recurrence, and outcome. RESULTS The data of the 24 patients are summarized in Tables 1 to 5. The patients included 16 females and 8 males (male/female ratio = 1:2), with age ranging between 16 and 74 yr (median 51 yr). TABLE 1. Personal Series of Parasellar Schwannomas N. of case Age/sex Nerve of origin Location Size (cm) Clinical onset Surgical approach Entity of resection Outcome Follow-up (yr) Recurrence 1. 16/F l III Intracavernous and cisternal 1.7 × 1.5 × 1.2 Complete III palsy, proptosis Pterional epidural + intradural + EAC and UOC + grafting Complete Improved III palsy remission of proptosis 20 No 2. 51/F r III Intracavernous 2.0 × 1.8 × 2.0 Complete III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 11 No 3. 38/M r III Intracavernous 2.3 × 1.7 × 2.0 Partial III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 8 No 4. 30/M l VI Cisternal 3.2 × 2.6 × 2.8 Amaurosis, VI nerve palsy Pterional epidural + intradural Subtotal Unchanged 15 At 3 y reoperation 5. 45/F r V Intracavernous 2.5 × 1.8 × 1.4 V2 neuralgia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 16 No 6. 58/F l V Intracavernous and cisternal 2.0 × 2.0 × 3.0 V2-V3 neuralgia hypaesthesia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 18 No 7. 52/M r V Intracavernous 2.7 × 2.5 × 2.2 V2-V3 neuralgia Pterional epidural + EAC and UOC Gross total Remission of pain (no therapy) 17 No 8. 67/F l V Intracavernous and cisternal 2.2 × 2.0 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 20 No 9. 33/F r V Intracavernous 2.7 × 2.2 × 2.6 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 17 No 10. 28/F l V Meckel's cave 3.5 × 3.3 × 2.8 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness V2 hypaesthesia 13 At 5 y reoperation 11. 37/F r V Meckel's cave 2.0 × 1.8 × 2.4 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness V2 hypaesthesia 11 No 12. 24/F l V Meckel's cave 3.4 × 2.5 × 1.5 VI nerve palsy Pterional epidural Subtotal Improvement of diplopia 8 No 13. 45/M l V Meckel's cave 2.2 × 2.1 × 1.9 V2 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (no therapy) V2 hypaesthesia 7 No 14. 64/F r V Meckel's cave 2.4 × 2.0 × 2.6 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 3.5 No 15. 67/F l V Meckel's cave 3.6 × 3.0 × 2.8 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 4.5 No 16. 66/M l V Meckel's cave 3.2 × 2.6 × 2.0 V2-V3 neuralgia Pterional epidural Complete Remission of pain (with therapy) facial numbness 6 No 17. 59/M r V Meckel's cave 2.8 × 2.2 × 2.5 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness 8 No 18. 67/F r V Meckel's cave 3.0 × 2.7 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 9 No 19. 72/M r V Meckel's cave 2.7 × 2.4 × 2.5 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 5 No 20. 74/F r V Meckel's cave 3.4 × 2.8 × 3.0 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness 7 No 21. 49/F l V Intracavernous 1.7 × 1.5 × 1.5 V2-V3 neuralgia hypaesthesia Pterional epidural + EAC and UOC Subtotal Remission of pain (no therapy) V2 hypaesthesia 10 No 22. 61/F l V Intracavernous 1.6 × 1.3 × 1.5 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 9 No 23. 55/M l V Meckel's cave 2.0 × 1.8 × 1.7 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 5 No 24. 71/F r V Meckel's cave 3.0 × 2.8 × 1.9 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 14 No N. of case Age/sex Nerve of origin Location Size (cm) Clinical onset Surgical approach Entity of resection Outcome Follow-up (yr) Recurrence 1. 16/F l III Intracavernous and cisternal 1.7 × 1.5 × 1.2 Complete III palsy, proptosis Pterional epidural + intradural + EAC and UOC + grafting Complete Improved III palsy remission of proptosis 20 No 2. 51/F r III Intracavernous 2.0 × 1.8 × 2.0 Complete III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 11 No 3. 38/M r III Intracavernous 2.3 × 1.7 × 2.0 Partial III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 8 No 4. 30/M l VI Cisternal 3.2 × 2.6 × 2.8 Amaurosis, VI nerve palsy Pterional epidural + intradural Subtotal Unchanged 15 At 3 y reoperation 5. 45/F r V Intracavernous 2.5 × 1.8 × 1.4 V2 neuralgia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 16 No 6. 58/F l V Intracavernous and cisternal 2.0 × 2.0 × 3.0 V2-V3 neuralgia hypaesthesia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 18 No 7. 52/M r V Intracavernous 2.7 × 2.5 × 2.2 V2-V3 neuralgia Pterional epidural + EAC and UOC Gross total Remission of pain (no therapy) 17 No 8. 67/F l V Intracavernous and cisternal 2.2 × 2.0 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 20 No 9. 33/F r V Intracavernous 2.7 × 2.2 × 2.6 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 17 No 10. 28/F l V Meckel's cave 3.5 × 3.3 × 2.8 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness V2 hypaesthesia 13 At 5 y reoperation 11. 37/F r V Meckel's cave 2.0 × 1.8 × 2.4 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness V2 hypaesthesia 11 No 12. 24/F l V Meckel's cave 3.4 × 2.5 × 1.5 VI nerve palsy Pterional epidural Subtotal Improvement of diplopia 8 No 13. 45/M l V Meckel's cave 2.2 × 2.1 × 1.9 V2 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (no therapy) V2 hypaesthesia 7 No 14. 64/F r V Meckel's cave 2.4 × 2.0 × 2.6 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 3.5 No 15. 67/F l V Meckel's cave 3.6 × 3.0 × 2.8 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 4.5 No 16. 66/M l V Meckel's cave 3.2 × 2.6 × 2.0 V2-V3 neuralgia Pterional epidural Complete Remission of pain (with therapy) facial numbness 6 No 17. 59/M r V Meckel's cave 2.8 × 2.2 × 2.5 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness 8 No 18. 67/F r V Meckel's cave 3.0 × 2.7 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 9 No 19. 72/M r V Meckel's cave 2.7 × 2.4 × 2.5 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 5 No 20. 74/F r V Meckel's cave 3.4 × 2.8 × 3.0 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness 7 No 21. 49/F l V Intracavernous 1.7 × 1.5 × 1.5 V2-V3 neuralgia hypaesthesia Pterional epidural + EAC and UOC Subtotal Remission of pain (no therapy) V2 hypaesthesia 10 No 22. 61/F l V Intracavernous 1.6 × 1.3 × 1.5 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 9 No 23. 55/M l V Meckel's cave 2.0 × 1.8 × 1.7 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 5 No 24. 71/F r V Meckel's cave 3.0 × 2.8 × 1.9 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 14 No EAC, extradural anterior clinoidectomy; UOC, unroofing of the optic canal; r, right; l, left. View Large TABLE 1. Personal Series of Parasellar Schwannomas N. of case Age/sex Nerve of origin Location Size (cm) Clinical onset Surgical approach Entity of resection Outcome Follow-up (yr) Recurrence 1. 16/F l III Intracavernous and cisternal 1.7 × 1.5 × 1.2 Complete III palsy, proptosis Pterional epidural + intradural + EAC and UOC + grafting Complete Improved III palsy remission of proptosis 20 No 2. 51/F r III Intracavernous 2.0 × 1.8 × 2.0 Complete III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 11 No 3. 38/M r III Intracavernous 2.3 × 1.7 × 2.0 Partial III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 8 No 4. 30/M l VI Cisternal 3.2 × 2.6 × 2.8 Amaurosis, VI nerve palsy Pterional epidural + intradural Subtotal Unchanged 15 At 3 y reoperation 5. 45/F r V Intracavernous 2.5 × 1.8 × 1.4 V2 neuralgia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 16 No 6. 58/F l V Intracavernous and cisternal 2.0 × 2.0 × 3.0 V2-V3 neuralgia hypaesthesia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 18 No 7. 52/M r V Intracavernous 2.7 × 2.5 × 2.2 V2-V3 neuralgia Pterional epidural + EAC and UOC Gross total Remission of pain (no therapy) 17 No 8. 67/F l V Intracavernous and cisternal 2.2 × 2.0 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 20 No 9. 33/F r V Intracavernous 2.7 × 2.2 × 2.6 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 17 No 10. 28/F l V Meckel's cave 3.5 × 3.3 × 2.8 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness V2 hypaesthesia 13 At 5 y reoperation 11. 37/F r V Meckel's cave 2.0 × 1.8 × 2.4 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness V2 hypaesthesia 11 No 12. 24/F l V Meckel's cave 3.4 × 2.5 × 1.5 VI nerve palsy Pterional epidural Subtotal Improvement of diplopia 8 No 13. 45/M l V Meckel's cave 2.2 × 2.1 × 1.9 V2 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (no therapy) V2 hypaesthesia 7 No 14. 64/F r V Meckel's cave 2.4 × 2.0 × 2.6 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 3.5 No 15. 67/F l V Meckel's cave 3.6 × 3.0 × 2.8 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 4.5 No 16. 66/M l V Meckel's cave 3.2 × 2.6 × 2.0 V2-V3 neuralgia Pterional epidural Complete Remission of pain (with therapy) facial numbness 6 No 17. 59/M r V Meckel's cave 2.8 × 2.2 × 2.5 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness 8 No 18. 67/F r V Meckel's cave 3.0 × 2.7 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 9 No 19. 72/M r V Meckel's cave 2.7 × 2.4 × 2.5 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 5 No 20. 74/F r V Meckel's cave 3.4 × 2.8 × 3.0 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness 7 No 21. 49/F l V Intracavernous 1.7 × 1.5 × 1.5 V2-V3 neuralgia hypaesthesia Pterional epidural + EAC and UOC Subtotal Remission of pain (no therapy) V2 hypaesthesia 10 No 22. 61/F l V Intracavernous 1.6 × 1.3 × 1.5 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 9 No 23. 55/M l V Meckel's cave 2.0 × 1.8 × 1.7 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 5 No 24. 71/F r V Meckel's cave 3.0 × 2.8 × 1.9 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 14 No N. of case Age/sex Nerve of origin Location Size (cm) Clinical onset Surgical approach Entity of resection Outcome Follow-up (yr) Recurrence 1. 16/F l III Intracavernous and cisternal 1.7 × 1.5 × 1.2 Complete III palsy, proptosis Pterional epidural + intradural + EAC and UOC + grafting Complete Improved III palsy remission of proptosis 20 No 2. 51/F r III Intracavernous 2.0 × 1.8 × 2.0 Complete III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 11 No 3. 38/M r III Intracavernous 2.3 × 1.7 × 2.0 Partial III palsy, proptosis Pterional epidural + EAC and UOC Complete Unchanged III palsy improved proptosis 8 No 4. 30/M l VI Cisternal 3.2 × 2.6 × 2.8 Amaurosis, VI nerve palsy Pterional epidural + intradural Subtotal Unchanged 15 At 3 y reoperation 5. 45/F r V Intracavernous 2.5 × 1.8 × 1.4 V2 neuralgia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 16 No 6. 58/F l V Intracavernous and cisternal 2.0 × 2.0 × 3.0 V2-V3 neuralgia hypaesthesia Pterional epidural Gross total Remission of pain (no therapy) V2 hypaesthesia 18 No 7. 52/M r V Intracavernous 2.7 × 2.5 × 2.2 V2-V3 neuralgia Pterional epidural + EAC and UOC Gross total Remission of pain (no therapy) 17 No 8. 67/F l V Intracavernous and cisternal 2.2 × 2.0 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 20 No 9. 33/F r V Intracavernous 2.7 × 2.2 × 2.6 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 17 No 10. 28/F l V Meckel's cave 3.5 × 3.3 × 2.8 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness V2 hypaesthesia 13 At 5 y reoperation 11. 37/F r V Meckel's cave 2.0 × 1.8 × 2.4 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness V2 hypaesthesia 11 No 12. 24/F l V Meckel's cave 3.4 × 2.5 × 1.5 VI nerve palsy Pterional epidural Subtotal Improvement of diplopia 8 No 13. 45/M l V Meckel's cave 2.2 × 2.1 × 1.9 V2 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (no therapy) V2 hypaesthesia 7 No 14. 64/F r V Meckel's cave 2.4 × 2.0 × 2.6 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 3.5 No 15. 67/F l V Meckel's cave 3.6 × 3.0 × 2.8 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 4.5 No 16. 66/M l V Meckel's cave 3.2 × 2.6 × 2.0 V2-V3 neuralgia Pterional epidural Complete Remission of pain (with therapy) facial numbness 6 No 17. 59/M r V Meckel's cave 2.8 × 2.2 × 2.5 V2-V3 neuralgia hypaesthesia Pterional epidural Complete Remission of pain (with therapy) facial numbness 8 No 18. 67/F r V Meckel's cave 3.0 × 2.7 × 2.4 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 9 No 19. 72/M r V Meckel's cave 2.7 × 2.4 × 2.5 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 5 No 20. 74/F r V Meckel's cave 3.4 × 2.8 × 3.0 V2 neuralgia hypaesthesia Pterional epidural Subtotal Remission of pain (with therapy) facial numbness 7 No 21. 49/F l V Intracavernous 1.7 × 1.5 × 1.5 V2-V3 neuralgia hypaesthesia Pterional epidural + EAC and UOC Subtotal Remission of pain (no therapy) V2 hypaesthesia 10 No 22. 61/F l V Intracavernous 1.6 × 1.3 × 1.5 V2-V3 neuralgia Pterional epidural + EAC and UOC Complete Remission of pain (no therapy) 9 No 23. 55/M l V Meckel's cave 2.0 × 1.8 × 1.7 V1-V2-V3 neuralgia Pterional epidural + intradural Complete Remission of pain (no therapy) 5 No 24. 71/F r V Meckel's cave 3.0 × 2.8 × 1.9 V2-V3 neuralgia Pterional epidural Complete Remission of pain (no therapy) 14 No EAC, extradural anterior clinoidectomy; UOC, unroofing of the optic canal; r, right; l, left. View Large Tumor Origin, Location, and Size Twenty schwannomas arose from the trigeminal nerve (7 intracavernous and 13 within the Meckel's cave), 3 from the oculomotor nerve, and 1 from the abducens nerve. According to the location, 7 schwannomas (5 trigeminal and 2 oculomotor) were purely intracavernous; 4 cases (2 trigeminal, 1 oculomotor, and 1 abducens) were in the cisternal space (with intracavernous extension in 3); finally, 13 trigeminal schwannomas were at the Meckel's cave. The tumor size ranged from 1.6 × 1.3 × 1.5 to 3.6 × 3 × 2.8 cm (Table 1). Clinical Presentation and Diagnosis All 24 patients were symptomatic. Among 20 patients with parasellar trigeminal schwannomas, 19 had facial pain and paresthesia, with variable hypoesthesia in 8 (Tables 1 and 2); 1 patient with Dolenc's type II schwannoma had diplopia due to left sixth nerve paresis as the unique complaint, in absence of symptoms and signs of trigeminal involvement.20 All 19 patients with trigeminal neuralgia had been treated with carbamazepine or oxcarbamazepine at high doses for at least 3 mo, with scarce or no clinical response. TABLE 2. Summary of the Clinical Data and Outcome of 24 Parasellar Schwannomas Tumor location and origin No. of cases Visual deficit Third nerve deficit Sixth nerve deficit Proptosis Facial pain Facial numbness Facial hypoestesia Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Trigeminal intracavernous (Dolenc type I) 7 2 1 – – 1 1 – – 7 – 7 1 3 3 trigeminal cavum Meckeli (Dolenc type II) 13 – – – – 2 1 – – 12 – 12 4 5 3 oculomotor nerve 3 1 1 3 2 – – 3 – – – – – – – Abducens nerve 1 1 1 – – 1 1 – – – – – – – – Tumor location and origin No. of cases Visual deficit Third nerve deficit Sixth nerve deficit Proptosis Facial pain Facial numbness Facial hypoestesia Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Trigeminal intracavernous (Dolenc type I) 7 2 1 – – 1 1 – – 7 – 7 1 3 3 trigeminal cavum Meckeli (Dolenc type II) 13 – – – – 2 1 – – 12 – 12 4 5 3 oculomotor nerve 3 1 1 3 2 – – 3 – – – – – – – Abducens nerve 1 1 1 – – 1 1 – – – – – – – – View Large TABLE 2. Summary of the Clinical Data and Outcome of 24 Parasellar Schwannomas Tumor location and origin No. of cases Visual deficit Third nerve deficit Sixth nerve deficit Proptosis Facial pain Facial numbness Facial hypoestesia Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Trigeminal intracavernous (Dolenc type I) 7 2 1 – – 1 1 – – 7 – 7 1 3 3 trigeminal cavum Meckeli (Dolenc type II) 13 – – – – 2 1 – – 12 – 12 4 5 3 oculomotor nerve 3 1 1 3 2 – – 3 – – – – – – – Abducens nerve 1 1 1 – – 1 1 – – – – – – – – Tumor location and origin No. of cases Visual deficit Third nerve deficit Sixth nerve deficit Proptosis Facial pain Facial numbness Facial hypoestesia Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Trigeminal intracavernous (Dolenc type I) 7 2 1 – – 1 1 – – 7 – 7 1 3 3 trigeminal cavum Meckeli (Dolenc type II) 13 – – – – 2 1 – – 12 – 12 4 5 3 oculomotor nerve 3 1 1 3 2 – – 3 – – – – – – – Abducens nerve 1 1 1 – – 1 1 – – – – – – – – View Large Three cases with oculomotor schwannomas and the case of abducens nerve schwannoma had complete (3 cases) or partial (1 case) palsy of the nerve of origin, with slight proptosis in 3. Radiological Characteristics On preoperative MRI, 17 tumors were isointense and 7 were isohypointense in T1-weighted sequences; all were hyperintense on T2-weighted images. A homogeneous contrast enhancement after gadolinium was evident in 20 cases, whereas 4 showed small cystic component. CT scan, performed in 9 trigeminal schwannomas, showed bony erosion at the Meckel's cave (6 cases) or ovale and rotundum foramina (3 cases). The tumor location (extradural vs intradural, Table 3) was correctly diagnosed on MRI in 22 out of 24 cases, and particularly in all 7 intracavernous trigeminal schwannomas, in all 4 of the oculomotor (Figure 1) and abducens nerves, and in 11 out of 13 trigeminal schwannomas of the Meckel's cave (Figures 2-4); in 2 cases of the last group, the intradural extension could not be defined (Figure 5). FIGURE 1. View largeDownload slide Case 1. Schwannoma of the left oculomotor nerve. MR, postcontrast coronal T1 sequences, A, preoperative, and B, postoperative: small intracavernous enhancing round lesion, which was found to arise from the third cranial nerve at operation by extradural approach. FIGURE 1. View largeDownload slide Case 1. Schwannoma of the left oculomotor nerve. MR, postcontrast coronal T1 sequences, A, preoperative, and B, postoperative: small intracavernous enhancing round lesion, which was found to arise from the third cranial nerve at operation by extradural approach. FIGURE 2. View largeDownload slide Case 13. Trigeminal schwannoma of the Meckel's cave. MR, A-C, preoperative, and D, postoperative Turbo Spin-Echo T1-weighted coronal sections, after contrast medium injection. Presence of a small enhancing mass in left Meckel's cave (arrow), extending to the V3 mandibular nerve and the sensory root (arrow). The tumor is well separated from the ICA by the medial dural wall B. The tumor was interdural (middle fossa), covered by meningeal-periosteal dura, and interperiosteal (infratemporal fossa), covered by periosteum. The interdural location was confirmed intraoperatively by pterional extradural approach. FIGURE 2. View largeDownload slide Case 13. Trigeminal schwannoma of the Meckel's cave. MR, A-C, preoperative, and D, postoperative Turbo Spin-Echo T1-weighted coronal sections, after contrast medium injection. Presence of a small enhancing mass in left Meckel's cave (arrow), extending to the V3 mandibular nerve and the sensory root (arrow). The tumor is well separated from the ICA by the medial dural wall B. The tumor was interdural (middle fossa), covered by meningeal-periosteal dura, and interperiosteal (infratemporal fossa), covered by periosteum. The interdural location was confirmed intraoperatively by pterional extradural approach. FIGURE 3. View largeDownload slide Case 12. Meckel's cave trigeminal schwannoma. MR, A, preoperative, and B, postoperative T1-weighted postcontrast sequence: A, parasellar enhancing mass, which was confirmed as interdural at surgery by an extradural approach; B, well-defined enhancing medial dural wall at the surgical cavity. FIGURE 3. View largeDownload slide Case 12. Meckel's cave trigeminal schwannoma. MR, A, preoperative, and B, postoperative T1-weighted postcontrast sequence: A, parasellar enhancing mass, which was confirmed as interdural at surgery by an extradural approach; B, well-defined enhancing medial dural wall at the surgical cavity. FIGURE 4. View largeDownload slide Case 15. Trigeminal schwannoma. A, Turbo Spin-Echo T2-weighted axial section; B, Turbo Spin-Echo T1-weighted axial section, after contrast medium injection. Dumbbell-shaped low-signal-intensity mass, extending from the Meckel's cave (interdural) to the interpeduncular cistern (subdural) along course of left trigeminal nerve and intensely enhancing after contrast medium injection. The 2 tumor components (interdural and subdural) were confirmed intraoperatively and resected by both extradural and intradural approach. FIGURE 4. View largeDownload slide Case 15. Trigeminal schwannoma. A, Turbo Spin-Echo T2-weighted axial section; B, Turbo Spin-Echo T1-weighted axial section, after contrast medium injection. Dumbbell-shaped low-signal-intensity mass, extending from the Meckel's cave (interdural) to the interpeduncular cistern (subdural) along course of left trigeminal nerve and intensely enhancing after contrast medium injection. The 2 tumor components (interdural and subdural) were confirmed intraoperatively and resected by both extradural and intradural approach. FIGURE 5. View largeDownload slide Case 23. Left parasellar trigeminal schwannoma. MR, A, preoperative, and B, postoperative postcontrast axial sequences: round, inhomogeneus enhancing mass with not well evident medial dural wall. At the extradural surgical exploration small tumor transgression of the medial dural wall was evidenced FIGURE 5. View largeDownload slide Case 23. Left parasellar trigeminal schwannoma. MR, A, preoperative, and B, postoperative postcontrast axial sequences: round, inhomogeneus enhancing mass with not well evident medial dural wall. At the extradural surgical exploration small tumor transgression of the medial dural wall was evidenced The preoperative neuroradiological identification of the nerve of origin was correct in 22 cases, excepting for 1 oculomotor nerve and 1 abducens nerve schwannoma. Surgical Approaches and Technique For all patients, we performed a pterional craniotomy coupled with drilling of the sphenoid wing by extradural route to expose the middle cranial fossa and the cavernous sinus region. The further procedure varied according to the tumor location and origin (Tables 1, 3, and 4). In the 13 cases of trigeminal schwannomas of the Meckel's cave, the dissection of the basal temporal dura mater was carried out after cutting the middle meningeal artery and unroofing the foramina ovale and rotundum by high-speed drill. This technique allowed exposing and mobilizing the whole trigeminal complex and the tumor. After opening the thin external dural layer, the tumor was resected. In 11 out of these 13 cases, the preserved medial dural surface remained extradural. In 2 cases, a dural opening was required to remove the tumor, extended beyond the medial dural wall. The removal was complete in 10 cases and subtotal in 3, because of the intimate adherences with the Gasserian ganglion and V2 root. In 7 cases of intracavernous trigeminal schwannomas, the above-cited extradural approach was carried out to expose the trigeminal complex. Unroofing of the superior orbital fissure was performed in 5 cases, whereas the anterior clinoid process and the roof of the optic canal were removed in 4 cases to expose the medial portion of the cavernous sinus. The resection was complete in all cases, including 2 with small intradural extension. The intradural exploration was not necessary. TABLE 3. Tumor Location, Relationship with the Dura Mater, and Surgical Approach of 24 Parasellar Schwannomas Preoperative MR definition Findings at surgical exploration Surgical approach Tumor location and origin No. of cases Clearly extradural (interdural) Clearly extra-intradural Doubtful intradural extention Extradural (interdural) Extra-intradural Extradural (interdural) Extra-intradural Trigeminal intracavernous (Dolenc type I) 7 5 2 – 5 2 7 – Trigeminal cavum Meckeli (Dolenc type II) 13 9 2 2 9 4 11 2 Oculomotor nerve 3 1 2 – 1 2 2 1 Abducens nerve 1 – 1 – – 1 – 1 Total 24 15 7 2 15 (66.7%) 9 (33.3%) 20 (77.8%) 4 (22.2%) Preoperative MR definition Findings at surgical exploration Surgical approach Tumor location and origin No. of cases Clearly extradural (interdural) Clearly extra-intradural Doubtful intradural extention Extradural (interdural) Extra-intradural Extradural (interdural) Extra-intradural Trigeminal intracavernous (Dolenc type I) 7 5 2 – 5 2 7 – Trigeminal cavum Meckeli (Dolenc type II) 13 9 2 2 9 4 11 2 Oculomotor nerve 3 1 2 – 1 2 2 1 Abducens nerve 1 – 1 – – 1 – 1 Total 24 15 7 2 15 (66.7%) 9 (33.3%) 20 (77.8%) 4 (22.2%) View Large TABLE 3. Tumor Location, Relationship with the Dura Mater, and Surgical Approach of 24 Parasellar Schwannomas Preoperative MR definition Findings at surgical exploration Surgical approach Tumor location and origin No. of cases Clearly extradural (interdural) Clearly extra-intradural Doubtful intradural extention Extradural (interdural) Extra-intradural Extradural (interdural) Extra-intradural Trigeminal intracavernous (Dolenc type I) 7 5 2 – 5 2 7 – Trigeminal cavum Meckeli (Dolenc type II) 13 9 2 2 9 4 11 2 Oculomotor nerve 3 1 2 – 1 2 2 1 Abducens nerve 1 – 1 – – 1 – 1 Total 24 15 7 2 15 (66.7%) 9 (33.3%) 20 (77.8%) 4 (22.2%) Preoperative MR definition Findings at surgical exploration Surgical approach Tumor location and origin No. of cases Clearly extradural (interdural) Clearly extra-intradural Doubtful intradural extention Extradural (interdural) Extra-intradural Extradural (interdural) Extra-intradural Trigeminal intracavernous (Dolenc type I) 7 5 2 – 5 2 7 – Trigeminal cavum Meckeli (Dolenc type II) 13 9 2 2 9 4 11 2 Oculomotor nerve 3 1 2 – 1 2 2 1 Abducens nerve 1 – 1 – – 1 – 1 Total 24 15 7 2 15 (66.7%) 9 (33.3%) 20 (77.8%) 4 (22.2%) View Large TABLE 4. Surgical Bone Steps of the Skull-Base Approach of 24 Parasellar Schwannomas Tumor location and origin No. of cases EAC Unroofing of the optic canal Unroofing of the SOF Unroofing of the foramina ovale and rotondum Trigeminal intracavernous (Dolenc type I) 7 4 4 5 7 Trigeminal cavum Meckeli (Dolenc type II) 13 – – – 13 Oculomotor nerve 3 3 3 3 – Abducens nerve 1 1 – 1 – Tumor location and origin No. of cases EAC Unroofing of the optic canal Unroofing of the SOF Unroofing of the foramina ovale and rotondum Trigeminal intracavernous (Dolenc type I) 7 4 4 5 7 Trigeminal cavum Meckeli (Dolenc type II) 13 – – – 13 Oculomotor nerve 3 3 3 3 – Abducens nerve 1 1 – 1 – EAC, extradural anterior clinoidectomy; SOF, superior orbital fissure View Large TABLE 4. Surgical Bone Steps of the Skull-Base Approach of 24 Parasellar Schwannomas Tumor location and origin No. of cases EAC Unroofing of the optic canal Unroofing of the SOF Unroofing of the foramina ovale and rotondum Trigeminal intracavernous (Dolenc type I) 7 4 4 5 7 Trigeminal cavum Meckeli (Dolenc type II) 13 – – – 13 Oculomotor nerve 3 3 3 3 – Abducens nerve 1 1 – 1 – Tumor location and origin No. of cases EAC Unroofing of the optic canal Unroofing of the SOF Unroofing of the foramina ovale and rotondum Trigeminal intracavernous (Dolenc type I) 7 4 4 5 7 Trigeminal cavum Meckeli (Dolenc type II) 13 – – – 13 Oculomotor nerve 3 3 3 3 – Abducens nerve 1 1 – 1 – EAC, extradural anterior clinoidectomy; SOF, superior orbital fissure View Large TABLE 5. Correlation Between Entity of Resection and Surgical Approach (Extradural vs Extra-Intradural) Entity of resection Tumor location and origin No. of cases Surgical approach Gross total Subtotal Trigeminal, intracavernous 5 Extradural 5 5 – Extra-intradural – – – Trigeminal, Meckel's cave 15 Extradural 13 9 4 Extra-intradural 2 2 – Oculomotor nerve 3 Extradural 5 2 – Extra-intradural – 1 – Abducens nerve 1 Extradural – – – Extra-intradural 1 – 1 Entity of resection Tumor location and origin No. of cases Surgical approach Gross total Subtotal Trigeminal, intracavernous 5 Extradural 5 5 – Extra-intradural – – – Trigeminal, Meckel's cave 15 Extradural 13 9 4 Extra-intradural 2 2 – Oculomotor nerve 3 Extradural 5 2 – Extra-intradural – 1 – Abducens nerve 1 Extradural – – – Extra-intradural 1 – 1 EAC, extradural anterior clinoidectomy; SOF, superior orbital fissure. View Large TABLE 5. Correlation Between Entity of Resection and Surgical Approach (Extradural vs Extra-Intradural) Entity of resection Tumor location and origin No. of cases Surgical approach Gross total Subtotal Trigeminal, intracavernous 5 Extradural 5 5 – Extra-intradural – – – Trigeminal, Meckel's cave 15 Extradural 13 9 4 Extra-intradural 2 2 – Oculomotor nerve 3 Extradural 5 2 – Extra-intradural – 1 – Abducens nerve 1 Extradural – – – Extra-intradural 1 – 1 Entity of resection Tumor location and origin No. of cases Surgical approach Gross total Subtotal Trigeminal, intracavernous 5 Extradural 5 5 – Extra-intradural – – – Trigeminal, Meckel's cave 15 Extradural 13 9 4 Extra-intradural 2 2 – Oculomotor nerve 3 Extradural 5 2 – Extra-intradural – 1 – Abducens nerve 1 Extradural – – – Extra-intradural 1 – 1 EAC, extradural anterior clinoidectomy; SOF, superior orbital fissure. View Large All 4 cases of oculomotor and abducens nerve schwannomas were approached by a first extradural step, drilling the sphenoid wing and anterior clinoid process, and unroofing the superior orbital fissure. The 3 cases of intracavernous schwannoma of the oculomotor nerve also required optic canal unroofing. In 2 of them, the extradural approach allowed complete tumor resection. In another (case 1) with cisternal extension, intradural exploration was necessary. In this patient, the nerve segment in the lateral wall of the cavernous sinus was found to be enlarged by the tumor, whereas the cisternal segment was normal. Thus, en bloc resection of the tumor and reconstruction of the upper and lower stump by a sural nerve graft reinforced by fibrin glue were realized. The abducens nerve schwannoma located at the cisternal segment of the nerve was removed by an extra-intradural approach. Thus, complete tumor resection was achieved in 19 out of 24 cases (80%), and subtotal resection in 5 (20%). The correlation between entity of resection and surgical approach (Table 5) showed that gross total resection was achieved in 16 out of 20 (80%) tumors treated by extradural approach, and in 3 out of 4 (75%) after extra-intradural approach. Among 5 cases treated by subtotal resection, 4 were trigeminal schwannomas of type 1 (1 case) or type 2 (3 cases), and 1 was an abducens schwannoma. In these cases, the maximum tumor diameter was >3 cm in 4 out of 5 cases, whereas a strong adherence to the nerve was found in 2 cases. Outcome There were no surgical mortality or postoperative major complications. The neurological outcome was as follows (Tables 1 and 2). Among 3 oculomotor nerve schwannomas, the nerve palsy improved in the case treated by nerve grafting and was unchanged in 2 others; the exophthalmos disappeared in all. In the case of abducens nerve schwannoma, the nerve palsy was unchanged postoperatively. All 19 patients with trigeminal schwannomas and facial pain were treated with medical therapy for 1 to 3 mo after surgery. Remission of the facial pain was obtained in all cases, with no further therapy in 14. Five patients still need low doses of oxcarbazepine and complain of residual facial numbness. Facial hypesthesia of V2 and/or V3 disappeared only in 2 among 8 cases in which it was noticed preoperatively. In case 12 with trigeminal schwannoma of the Meckel's cave and isolated sixth nerve palsy, it slightly improved after surgery. Among 5 patients who underwent subtotal resection, 1 with more significant residual nodule was treated by radiosurgery. The other 4 with very small enhancing nodule were followed up with serial MRI; among them, 1 is stable after 6 yr, another has recently been treated by radiosurgery 5 yr after the initial operation, and 2 others experienced recurrence at 3 and 5 yr, respectively, and were reoperated on. Among 2 patients with recurrence, 1 (case 4), a 30-yr-old man with left abducens nerve schwannoma, was reoperated on 3 yr after the initial surgery through the previous approach for significant regrowth; complete resection was obtained. The second patient (case 10), a 28-yr-old woman with recurrent intradural trigeminal schwannoma of the Meckel's cave and facial pain 5 yr after subtotal resection by extradural route, was reoperated on through a pterional extra-intradural approach with complete resection. In both patients, the second surgery was preferred because of their young age. DISCUSSION Most Meckel's cave and intracavernous trigeminal schwannomas and intracavernous schwannomas of the oculomotor nerve have extradural (“interdural”) location.21-24 Thus, strictly intracavernous and Meckel's cave schwannomas are well separated from the cranial nerves and internal carotid artery (ICA) by the internal dural layer. On the other hand, those with significant cisternal extension and cisternal schwannomas of the oculomotor and abducens nerves lie close to the intradural ICA and cranial nerves in the cisternal space. Clinical and Radiological Definition The nerve of origin may preoperatively be identified by both clinical presentation and tumor location. The clinical presentation of trigeminal schwannomas may often be deceptive. Trigeminal nerve symptoms are present at clinical onset in only half of the cases,4 and often occur later; in addition, no evidence of trigeminal nerve dysfunction is reported in 10%20 to 56%25 of trigeminal schwannomas. It may be presumed that in some cases, the tumor may leave most trigeminal nerve fibers intact, mainly in cases of tumors of the Gasserian ganglion. Diplopia and eye movement dysfunction are reported in 6% to 34% of the patients with trigeminal schwannomas (in 10% as the initial complaint).4 An isolated diplopia due to abducens nerve palsy as the unique symptom was reported in 3 previous cases,25-26 and in one of our patients.20 Unlike trigeminal schwannomas, tumors arising from the oculomotor and abducens nerves almost invariably present with diplopia and objective signs of eye movement dysfunction.8,11,15 The very thin structure and vulnerability of these nerves may explain their early anatomic and functional involvement during tumor growth. Symptoms of dysfunction of the nerve of origin were the first clinical manifestation in 23 out of 24 patients in our series. The preoperative neuroradiological definition of parasellar schwannomas includes tumor location, its relationships with the dura (extradural, extra-intradural, cisternal), and the identification of the nerve of origin. The tumor location may be defined on 3-D gradient echo steady-state sequences of MRI. With this imaging technique, neural structures, vessels, and dura are visualized as low-signal intensity in the CSF hyperintensity.27-28 In this way, the SSFP sequences are superior to the conventional T2-weighted sequences in visualizing the cisternal cranial nerves and cavernous sinus (Figure 6).29-31 SSFP sequences of MR evidence small- and middle-size parasellar schwannomas as a hypo- or isointense mass, well defined by the high signal intensity of the CSF. Unfortunately, in larger tumors, the relationships with the surrounding CSF signal may not be visible. FIGURE 6. View largeDownload slide MR, 3-D CISS (Constructive Interference in Steady State) for the anatomic definition of the parasellar region and trigeminal cistern in a normal case. A, Section on axial plane at the level of the upper part of the cerebello-pontine cistern. The normal course of the fifth cranial nerve is clearly evident, from the point at which the nerve arises (REZ), to the Meckel's space (arrow); a hyperintense signal due to the presence of CSF forming a true cistern and curved in a hypointense dural fold is evident. B, Right parasagittal reconstruction. The whole course of the fifth nerve is demonstrated (arrow) from the REZ to the Meckel's space. FIGURE 6. View largeDownload slide MR, 3-D CISS (Constructive Interference in Steady State) for the anatomic definition of the parasellar region and trigeminal cistern in a normal case. A, Section on axial plane at the level of the upper part of the cerebello-pontine cistern. The normal course of the fifth cranial nerve is clearly evident, from the point at which the nerve arises (REZ), to the Meckel's space (arrow); a hyperintense signal due to the presence of CSF forming a true cistern and curved in a hypointense dural fold is evident. B, Right parasagittal reconstruction. The whole course of the fifth nerve is demonstrated (arrow) from the REZ to the Meckel's space. FIGURE 7. View largeDownload slide Choice of the surgical approach according to the neuroradiological findings. FIGURE 7. View largeDownload slide Choice of the surgical approach according to the neuroradiological findings. In this series, the correct definition (preservation vs transgression of the medial dural wall) was obtained in 22 out of 24 patients; in 2 large trigeminal schwannomas of the Meckel's cave, the intradural tumor extension was suspected on MRI but not confirmed during surgery. MRI may also suggest the tumor's nerve of origin. Trigeminal schwannomas of the Meckel's cave are diagnosed because of relationships with the bone and dural structures and enlargement of the foramina ovale and/or rotundum.32 For pure intracavernous schwannomas, the identification of the nerve origin is difficult, or even impossible, and may be determined only with clinical data. Finally, cisternal and cavernous-cisternal schwannomas of the oculomotor and abducens nerves may be diagnosed on MRI from the pattern of tumor growth along the cistern.33 MR with diffusion tensor tractography has recently been introduced to identify the cranial nerves,34 mainly the facial-acoustic complex around vestibular schwannomas.35-36 A recent study37 has explored the cranial nerves in relationship with trigeminal schwannomas. This technique seems useful for identifying the nerve of origin of parasellar schwannomas. Surgical Approach and Technique Parasellar schwannomas have been treated by different surgical approaches, including pterional frontotemporal intradural or extra-intradural,4,8,11 and subtemporal intradural or extra-intradural,38-42 eventually with resection of the orbitozygomatic process. The frontotemporal extradural approach introduced by Dolenc18 allows good extradural-interdural exposure of the trigeminal complex. The Meckel's cave, the trigeminal branches, and the cavernous sinus are well exposed by rotating the trajectory anteriorly, and most schwannomas of this region may be resected.43-44 The extradural approach avoids several risks, including brain retraction, sacrifice of temporal bridging veins, and cranial nerve deficits. The indication to pterional extradural approach vs an extradural-intradural approach depends on the origin, location, and size of the schwannoma. The preoperative neuroradiological identification of the tumor location (extradural or extra-intradural Meckel's cave, cavernous sinus, and parasellar cistern) may be helpful in planning the surgical approach (Figure 7). If the tumor is exclusively extradural (Meckel's cave, cavernous sinus), the extradural route of the pterional approach is sufficient in order to expose and remove the whole tumor mass. If the tumor is extra-intradural or cisternal (as Meckel's cave and cavernous schwannomas with dural transgression or cisternal schwannomas) after the extradural step, the dural opening allows complete control of the tumor. Most Dolenc's type II trigeminal schwannomas have an interdural location with preserved medial dural wall, as in all but 2 patients in our series. In these cases, an extended pterional extradural approach allows exposing and removing the schwannoma. If transgression of the medial dural layer and significant intradural tumor component are evidenced at the end of the extradural resection, the tumor removal may be completed by intradural exploration. Dolenc's type I intracavernous trigeminal schwannomas are resected through the above depicted route. The extradural tumor dissection is facilitated by the areolar tissue plane between the dura and the outer membrane of the cavernous sinus. Drilling of the anterior clinoid process must be performed in cases in which the exposure of the medial portion of the cavernous sinus is necessary.45 Interdural and intracavernous schwannomas of the oculomotor and abducens nerves may be approached by a pterional extradural route, coupled with anterior clinoidectomy. In such cases, the tumor grows within a dural cuff, allowing dissection from the lateral wall of the cavernous sinus, while preserving the integrity of the intracavernous structures. However, most schwannomas of the oculomotor and abducens nerves lie within the cistern or extend from the cavernous sinus to the cisternal space. In these cases, intradural exploration is necessary to obtain sufficient exposure of the cisternal portion of the tumor. Surgery vs Radiosurgery Radiosurgery is a safe technique for treating intracranial schwannomas. In a series of 36 patients with nonvestibular schwannomas treated by Gamma Knife, Elsharkawy46 found tumors to decrease in 56%, increase in 19%, and remain stable in 25%, with an overall tumor control of 80.6%.46 In a review of 9 reported series (including 4 overall nonacoustic schwannomas,47-50 2 trigeminal schwannomas,51-52 1 oculomotor schwannoma,15 and 1 jugular foramen schwannoma53) for a total of more than 200 patients, they found 2- and 5-yr progression-free survival times of 91% and 78%, respectively. Similar results were found in other radiosurgical series of trigeminal54 and abducens nerve schwannomas.14 The recurrence rate of several surgical series of trigeminal schwannomas is low, ranging from 0% to 7.4%,1-4,44 except for large or intra-extracranial tumors (14%).55 In agreement with others,3,44 we treat symptomatic trigeminal and oculomotor schwannomas by surgery at our institution. This selected group of schwannomas may usually be removed by pterional extradural approach with no manipulation of other cranial nerves and low risk of neurological deficits. CONCLUSION The surgical treatment of parasellar schwannomas may be planned on the preoperative MRI findings. The pterional extradural approach is usually sufficient for intracavernous and Meckel's cave trigeminal schwannomas; an intradural exploration is necessary for tumors with significant transgression of the medial dural wall. The rare intracavernous schwannomas of the oculomotor and abducens nerves may also be approached through a pterional extradural route; cases with cisternal or cavernous-cisternal location require the intradural approach to achieve exposure of the tumor. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Chowdhury FH , Haque MR , Kawsar KA , Sarker MH , Hasan M , Goel AH . Intracranial nonvestibular neurinomas: young neurosurgeons' experience . J Neurosci Rural Pract . 2014 ; 5 ( 3 ): 231 - 243 . Google Scholar CrossRef Search ADS PubMed 2. Goel A , Muzumdar D , Raman C . Trigeminal neuroma: analysis of surgical experience with 73 cases . Neurosurgery . 2003 ; 52 ( 4 ): 783 - 790 ; discussion 790 . Google Scholar CrossRef Search ADS PubMed 3. Pamir MN , Peker S , Bayrakli F , Kilic T , Ozek MM . Surgical treatment of trigeminal schwannomas . Neurosurg Rev . 2007 ; 30 ( 4 ): 329 - 337 ; discussion 337 . Google Scholar CrossRef Search ADS PubMed 4. Samii M , Migliori MM , Tatagiba M , Babu R . Surgical treatment of trigeminal schwannomas . J Neurosurg . 1995 ; 82 ( 5 ): 711 - 718 . Google Scholar CrossRef Search ADS PubMed 5. Cho YH , Sung KS , Song YJ , Kim DC , Choi S , Kim KU . Oculomotor nerve schwannoma: a case report . Brain Tumor Res Treat . 2014 ; 2 ( 1 ): 43 - 47 . Google Scholar CrossRef Search ADS PubMed 6. Mariniello G , Horvat A , Dolenc VV . En bloc resection of an intracavernous oculomotor nerve schwannoma and grafting of the oculomotor nerve with sural nerve. Case report and review of the literature . J Neurosurg . 1999 ; 91 ( 6 ): 1045 - 1049 . Google Scholar CrossRef Search ADS PubMed 7. Prabhu SS , Bruner JM . Large oculomotor schwannoma presenting as a parasellar mass: a case report and literature review . Surg Neurol Int . 2010 ; 1 ( 1 ): 15 . Google Scholar CrossRef Search ADS PubMed 8. Tanriover N , Kemerdere R , Kafadar AM , Muhammedrezai S , Akar Z . Oculomotor nerve schwannoma located in the oculomotor cistern . Surg Neurol . 2007 ; 67 ( 1 ): 83 - 88 ; discussion 88 . Google Scholar CrossRef Search ADS PubMed 9. Acharya R , Husain S , Chhabra SS , Patir R , Bhalla S , Seghal AD . Sixth nerve schwannoma: a case report with literature review . Neurol Sci . 2003 ; 24 ( 2 ): 74 - 79 . Google Scholar PubMed 10. Nakamura M , Carvalho GA , Samii M . Abducens nerve schwannoma: a case report and review of the literature . Surg Neurol . 2002 ; 57 ( 3 ): 183 - 188 ; discussion 188-189 . Google Scholar CrossRef Search ADS PubMed 11. Park JH , Cho YH , Kim JH , Lee JK , Kim CJ . Abducens nerve schwannoma: case report and review of the literature . Neurosurg Rev . 2009 ; 32 ( 3 ): 375 - 378 ; discussion 378 . Google Scholar CrossRef Search ADS PubMed 12. Williams LS , Schmalfuss IM , Sistrom CL et al. MR imaging of the trigeminal ganglion, nerve, and the perineural vascular plexus: normal appearance and variants with correlation to cadaver specimens . AJNR Am J Neuroradiol . 2003 ; 24 ( 7 ): 1317 - 1323 . Google Scholar PubMed 13. Erlich SA , Tymianski M , Kiehl TR . Cellular schwannoma of the abducens nerve: case report and review of the literature . Clin Neurol Neurochir . 2009 ; 111 ( 5 ): 467 - 471 . Google Scholar CrossRef Search ADS 14. Prasad GL , Sharma MS , Kale SS , Agrawal D , Singh M , Sharma BS . Gamma knife radiosurgery in the treatment of abducens nerve schwannomas: a retrospective study . J Neurosurg 2016 ; 125 ( 4 ): 832 - 837 . Google Scholar CrossRef Search ADS PubMed 15. Kim IY , Kondziolka D , Niranjan A , Flickinger JC , Lunsford LD . Gamma Knife surgery for schwannomas originating from cranial nerves III, IV, and VI . J Neurosurg . 2008 ; 109 ( suppl ): 149 - 153 . Google Scholar PubMed 16. Hatae R , Miyazono M , Kohri R , Maeda K , Naito S . Trochlear nerve schwannoma with intratumoral hemorrhage presenting with persistent hiccups: a case report . J Neurol Surg Rep . 2014 ; 75 ( 1 ): e183 - e188 . Google Scholar CrossRef Search ADS PubMed 17. Boucher AB , Michael LM . The middle fossa approach for the removal of a trochlear schwannoma . Case Rep Neurol Med . 2014 ; 2014 : 672314 . Google Scholar PubMed 18. Dolenc VV . Frontotemporal epidural approach to trigeminal neurinomas . Acta Neurochir (Wien) . 1994 ; 130 ( 1-4 ): 55 - 65 . Google Scholar CrossRef Search ADS PubMed 19. Celli P , Ferrante L , Acqui M , Mastronardi L , Fortuna A , Palma L . Neurinoma of the third, fourth, and sixth cranial nerves: a survey and report of a new fourth nerve case . Surg Neurol . 1992 ; 38 ( 3 ): 216 - 224 . Google Scholar CrossRef Search ADS PubMed 20. Mariniello G , Giamundo A , Seneca V , Maiuri F . Abducens nerve palsy as the unique sign of a trigeminal schwannoma . Clin Neurol Neurosurg . 2013 ; 115 ( 7 ): 1121 - 1122 . Google Scholar CrossRef Search ADS PubMed 21. Harris FS , Rhoton AL . Anatomy of the cavernous sinus. A microsurgical study . J Neurosurg . 1976 ; 45 ( 2 ): 169 - 180 . Google Scholar CrossRef Search ADS PubMed 22. Dolenc VV . The Cavernous Sinus: A Multidisciplinary Approach to Vascular and Tumorous Lesions . New York : Springer ; 1987 . 23. Rhoton AL Jr . The cavernous sinus, the cavernous venous plexus, and the carotid collar . Neurosurgery . 2002 ; 51 ( 4 suppl ): S375 - S410 . Google Scholar PubMed 24. Goel A , Shah A . “Interdural” oculomotor neurinoma: report of two surgically treated cases . Acta Neurochir (Wien) . 2010 ; 152 ( 10 ): 1721 - 1724 . Google Scholar CrossRef Search ADS PubMed 25. Majoie CB , Hulsmans FJ , Castelijns JA et al. Primary nerve-sheath tumours of the trigeminal nerve: clinical and MRI findings . Neuroradiology . 1999 ; 41 ( 2 ): 100 - 108 . Google Scholar CrossRef Search ADS PubMed 26. Yamashita J , Asato R , Handa H , Nakao S , Ogata M . Abducens nerve palsy as initial symptom of trigeminal schwannoma . J Neurol Neurosurg Psychiatry . 1977 ; 40 ( 12 ): 1190 - 1197 . Google Scholar CrossRef Search ADS PubMed 27. Ciftci E , Anik Y , Arslan A , Akansel G , Sarisoy T , Demirci A . Driven equilibrium (drive) MR imaging of the cranial nerves V-VIII: comparison with the T2-weighted 3D TSE sequence . Eur J Radiol . 2004 ; 51 ( 3 ): 234 - 240 . Google Scholar CrossRef Search ADS PubMed 28. Yousry I , Moriggl B , Holtmannspoetter M , Schmid UD , Naidich TP , Yousry TA . Detailed anatomy of the motor and sensory roots of the trigeminal nerve and their neurovascular relationships: a magnetic resonance imaging study . J Neurosurg . 2004 ; 101 ( 3 ): 427 - 434 . Google Scholar CrossRef Search ADS PubMed 29. Hatipoglu HG , Durakoglugil T , Ciliz D , Yuksel E . Comparison of FSE T2W and 3D FIESTA sequences in the evaluation of posterior fossa cranial nerves with MR cisternography . Diagn Interv Radiol . 2007 ; 13 ( 2 ): 56 - 60 . Google Scholar PubMed 30. Seitz J , Held P , Strotzer M et al. MR imaging of cranial nerve lesions using six different high-resolution T1- and T2(*)-weighted 3D and 2D sequences . Acta Radiol . 2002 ; 43 ( 4 ): 349 - 353 . Google Scholar CrossRef Search ADS PubMed 31. Osborn A . Osborn's Brain: Imaging, Pathology and Anatomy . 1st ed . Salt Lake City, Utah : Amirsys ; 2013 : 613 - 644 . 32. Zhang L , Yang Y , Xu S , Wang J , Liu Y , Zhu S . Trigeminal schwannomas: a report of 42 cases and review of the relevant surgical approaches . Clin Neurol Neurosurg . 2009 ; 111 ( 3 ): 261 - 269 . Google Scholar CrossRef Search ADS PubMed 33. Lingawi SS . Oculomotor nerve schwannoma: MRI appearance . Clin Imaging . 2000 ; 24 ( 2 ): 86 - 88 . Google Scholar CrossRef Search ADS PubMed 34. Hodaie M , Quan J , Chen DQ . In vivo visualization of cranial nerve pathways in humans using diffusion-based tractography . Neurosurgery . 2010 ; 66 ( 4 ): 788 - 795 ; discussion 795-796 . Google Scholar CrossRef Search ADS PubMed 35. Chen DQ , Quan J , Guha A , Tymianski M , Mikulis D , Hodaie M . Three-dimensional in vivo modeling of vestibular schwannomas and surrounding cranial nerves with diffusion imaging tractography . Neurosurgery . 2011 ; 68 ( 4 ): 1077 - 1083 . Google Scholar CrossRef Search ADS PubMed 36. Gerganov VM , Giordano M , Samii M , Samii A . Diffusion tensor imaging-based fiber tracking for prediction of the position of the facial nerve in relation to large vestibular schwannomas . J Neurosurg . 2011 ; 115 ( 6 ): 1087 - 1093 . Google Scholar CrossRef Search ADS PubMed 37. Wei PH , Qi ZG , Chen G et al. Identification of cranial nerves around trigeminal schwannomas using diffusion tensor tractography: a technical note and report of 3 cases . Acta Neurochir (Wien) . 2016 ; 158 ( 3 ): 429 - 435 . Google Scholar CrossRef Search ADS PubMed 38. el-Kalliny M , van Loveren H , Keller JT , Tew JM Jr . Tumors of the lateral wall of the cavernous sinus . J Neurosurg . 1992 ; 77 ( 4 ): 508 - 514 . Google Scholar CrossRef Search ADS PubMed 39. Konovalov AN , Spallone A , Mukhamedjanov DJ , Tcherekajev VA , Makhmudov UB . Trigeminal neurinomas. A series of 111 surgical cases from a single institution . Acta Neurochir (Wien) . 1996 ; 138 ( 9 ): 1027 - 1035 . Google Scholar CrossRef Search ADS PubMed 40. Goel A , Nadkarni T . Basal lateral subtemporal approach for trigeminal neurinomas: report of an experience with 18 cases . Acta Neurochir (Wien) . 1999 ; 141 ( 7 ): 711 - 719 . Google Scholar CrossRef Search ADS PubMed 41. Sharma BS , Ahmad FU , Chandra PS , Mahapatra AK . Trigeminal schwannomas: experience with 68 cases . J Clin Neurosci . 2008 ; 15 ( 7 ): 738 - 743 . Google Scholar CrossRef Search ADS PubMed 42. Srinivas D , Somanna S , Ashwathnarayana CB , Bhagavatula ID . Multicompartmental trigeminal schwannomas: management strategies and outcome . Skull Base . 2011 ; 21 ( 6 ): 351 - 358 . Google Scholar CrossRef Search ADS PubMed 43. Day JD , Fukushima T , Giannotta SL . Microanatomical study of the extradural middle fossa approach to the petroclival and posterior cavernous sinus region: description of the rhomboid construct . Neurosurgery . 1994 ; 34 ( 6 ): 1009 - 1016 ; discussion 1016 . Google Scholar PubMed 44. Day JD , Fukushima T . The surgical management of trigeminal neuromas . Neurosurgery . 1998 ; 42 ( 2 ): 233 - 240 ; discussion 240-241 . Google Scholar CrossRef Search ADS PubMed 45. Mariniello G , Cappabianca P , Buonamassa S , de Divitiis E . Surgical treatment of intracavernous trigeminal schwannomas via a fronto-temporal epidural approach . Clin Neurol Neurosurg . 2004 ; 106 ( 2 ): 104 - 109 . Google Scholar CrossRef Search ADS PubMed 46. Elsharkawy M , Xu Z , Schlesinger D , Sheehan JP . Gamma knife surgery for nonvestibular schwannomas: radiological and clinical outcomes . J Neurosurg . 2012 ; 116 ( 1 ): 66 - 72 . Google Scholar CrossRef Search ADS PubMed 47. Pollock BE , Foote RL , Stafford SL . Stereotactic radiosurgery: the preferred management for patients with nonvestibular schwannomas? Int J Radiat Oncol Biol Phys . 2002 ; 52 ( 4 ): 1002 - 1007 . Google Scholar CrossRef Search ADS PubMed 48. Hamm KD , Gross MW , Fahrig A et al. Stereotactic radiotherapy for the treatment of nonacustic schwannomas . Neurosurgery . 2008 ; 62 ( suppl 5 ): A29 - A36 . Google Scholar CrossRef Search ADS PubMed 49. Showalter TN , Werner-Wasik M , Curran WJ Jr , Friedman DP , Xu X , Andrews DW . Stereotactic radiosurgery and fractionated stereotactic radiotherapy for the treatment of nonacoustic cranial nerve schwannomas . Neurosurgery . 2008 ; 63 ( 4 ): 734 - 740 . Google Scholar CrossRef Search ADS PubMed 50. Nishioka K , Abo D , Aoyama H et al. Stereotactic radiotherapy for intracranial nonacoustic schwannomas including facial nerve schwannoma . Int J Radiat Oncol Biol Phys . 2009 ; 75 ( 5 ): 1415 - 1419 . Google Scholar CrossRef Search ADS PubMed 51. Pan L , Wang EM , Zhang N et al. Long-term results of Leksell gamma knife surgery for trigeminal schwannomas . J Neurosurg . 2005 ; 102 ( suppl ): 220 - 224 . Google Scholar CrossRef Search ADS 52. Sheehan J , Yen CP , Arkha Y , Schlesinger D , Steiner L . Gamma knife surgery for trigeminal schwannoma . J Neurosurg . 2007 ; 106 ( 5 ): 839 - 845 . Google Scholar CrossRef Search ADS PubMed 53. Zhang N , Pan L , Dai JZ , Wang BJ , Wang EM , Cai PW . J Neurosurg . 2002 ; 97 ( suppl 5 ): 456 - 458 . PubMed 54. Kano H , Niranjan A , Kondziolka D , Flickinger JC , Dade Lunsford L . Stereotactic radiosurgery for trigeminal schwannoma: tumor control and functional preservation . J Neurosurg . 2009 ; 110 ( 3 ): 553 - 558 . Google Scholar CrossRef Search ADS PubMed 55. Goel A , Shah A , Muzumdar D , Nadkarni T , Chagla A . Trigeminal neurinomas with extracranial extension: analysis of 28 surgically treated cases . J Neurosurg . 2010 ; 113 ( 5 ): 1079 - 1084 . Google Scholar CrossRef Search ADS PubMed COMMENT The authors present a review of their surgical experience with 24 patients with parasellar schwannomas including 20 of the trigeminal nerve, 3 of the oculomotor nerve, and 1 of the abducens nerve. The surgical technique used to approach these lesions is well described and illustrated with pre- and postoperative imaging. The authors describe their methods for using the preoperative imaging findings to predict whether the surgical approach will be entirely extradural, or whether an intradural exposure would be needed as well. The patient outcomes in this series of patients are excellent. The authors’ experience with these types of lesions serves as a guide to the surgeon approaching these types of tumor. That said, certainly some of the small to medium sized tumors in this series possibly could have been well treated quite effectively with stereotactic radiosurgery instead. Michael Chicoine St. Louis, Missouri Copyright © 2017 by the Congress of Neurological Surgeons This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Operative NeurosurgeryOxford University Press

Published: Aug 22, 2017

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