Petrosal Meningiomas: Factors Affecting Outcome and the Role of Intraoperative Multimodal Assistance to Microsurgery

Petrosal Meningiomas: Factors Affecting Outcome and the Role of Intraoperative Multimodal... Abstract BACKGROUND Petrous meningiomas (PMs) represent a subset of posterior fossa tumors accounting for ∼8% of all intracranial meningiomas. Surgical treatment of PMs is challenging because of their relationships with vital neurovascular structures of the cerebellopontine angle. OBJECTIVE To investigate independent pre- and intraoperative predictors of PM surgery outcome. METHODS We reviewed the surgical and outcome data of patients who underwent microsurgical resection of PMs from 1997 to 2016. From 2007 onward, a multimodal intraoperative protocol consisting of intraoperative neuromonitoring (IONM), endoscopy, and indocyanine green (ICG) videoangiography was applied. Outcome variables included extent of resection, Karnofsky performance status (KPS), overall survival, and progression-free survival (PFS). RESULTS A total of 54 patients were included. Independent predictors of gross total resection (GTR) included retromeatal location (P < .0175; odds ratio [OR] 4.05), absence of brainstem compression (P < .02; OR 3.55), and histological WHO grade I (P < .001; OR 3.47). Nongiant size (P < .012; OR 4.38), and WHO grade I (P < .0001; OR 7.7) were independent predictors of stable or improved KPS. The use of multimodal intraoperative tools to assist surgery independently predicted GTR (P < .002; OR 6.8) and good KPS (P < .018; OR 4.23). Nongiant size (P = .01) and WHO grade I (P = .002) were significantly associated with increased PFS. CONCLUSION Notwithstanding the limitations of a retrospective study, our results suggest that support of microsurgery by a combination of IONM, endoscopy, and ICG videoangiography may improve patient outcome in PM surgery. Petrous bone meningiomas, Intraoperative neurophysiological monitoring, Endoscopic assistance, Indocyanine green videoangiography, Posterior fossa meningioma ABBREVIATIONS ABBREVIATIONS BAEP brainstem auditory evoked potentials CPA cerebellopontine angle EMG electromyography EOR extent of resection GTR gross total resection ICG indocyanine green IONM intraoperative neurophysiological monitoring KPS Karnofsky performance status MEPs motor evoked potentials MR magnetic resonance NPVs negative predictive values OR odds ratio OS overall survival PFS progression-free survival PPVs positive predictive values PMs petrous meningiomas PR partial resection SEPs somatosensory evoked potentials STR subtotal resection Petrous meningiomas (PMs) represent a subset of posterior fossa tumors. They account for approximately 8% of all intracranial meningiomas1 and 50% of all posterior cranial fossa meningiomas2 and are among the most challenging skull base meningiomas because of their relationships with vital neurovascular structures. Objective The aim of this study was to investigate pre- and intraoperative predictors of outcome for patients operated on for PMs beyond clinical variables, the use of multimodal intraoperative strategies for the surgical management of PM, including intraoperative neurophysiological monitoring (IONM), endoscopic assistance, and indocyanine green (ICG) videoangiography, was highlighted. The extent of resection (EOR), Karnofsky performance status (KPS), overall survival (OS), and progression-free survival (PFS) were analyzed. METHODS Study Design and Setting We retrospectively reviewed the clinical, surgical and outcome data of patients with PMs operated on by 1 surgeon (FT) at a single institution (Department of Neurosurgery, University of Messina, Italy) from January 1997 to December 2016. Participants and Data Sources Table 1 summarizes the clinical and demographic characteristics of the patients. All patients underwent microsurgical resection. From 2007 onward, a multimodal intraoperative strategy consisting of IONM, endoscopic assistance, and ICG videoangiography was added to the standard microsurgical technique, which remained fundamentally unchanged. TABLE 1. Clinical and Demographic Characteristics of Patients Variables N° Patients Age (mean ± SD) 56.7 ± 14.2 Sex  M 9 (17%)  F 45 (83%) Type of meningioma  Premeatal 26 (48%)  Retromeatal 28 (52%) Tumor size  Small (<1 cm) 0  Medium (1-2.4 cm) 2 (4%)  Large (2.5-4.4 cm) 24 (44%)  Giant (>4.5 cm) 28 (52%) KPS (mean ± SD) 79 ± 17 Brainstem compression 24 (44%) Other deficits  None 17 (31%)  CN III 2 (4%)  CN IV 2 (4%)  CN V 10 (18%)  CN VI 3 (5%)  CN VII 7 (13%)  CN VIII 12 (22%)  CN IX X XI 7 (13%)  CN XII 0  Cerebellar dysfunctions 13 (24%)  Motor deficits 9 (17%)  Sensory deficit 1 (2%) Variables N° Patients Age (mean ± SD) 56.7 ± 14.2 Sex  M 9 (17%)  F 45 (83%) Type of meningioma  Premeatal 26 (48%)  Retromeatal 28 (52%) Tumor size  Small (<1 cm) 0  Medium (1-2.4 cm) 2 (4%)  Large (2.5-4.4 cm) 24 (44%)  Giant (>4.5 cm) 28 (52%) KPS (mean ± SD) 79 ± 17 Brainstem compression 24 (44%) Other deficits  None 17 (31%)  CN III 2 (4%)  CN IV 2 (4%)  CN V 10 (18%)  CN VI 3 (5%)  CN VII 7 (13%)  CN VIII 12 (22%)  CN IX X XI 7 (13%)  CN XII 0  Cerebellar dysfunctions 13 (24%)  Motor deficits 9 (17%)  Sensory deficit 1 (2%) SD, standard deviation; KPS, Karnofsky performance status; CN, cranial nerve View Large TABLE 1. Clinical and Demographic Characteristics of Patients Variables N° Patients Age (mean ± SD) 56.7 ± 14.2 Sex  M 9 (17%)  F 45 (83%) Type of meningioma  Premeatal 26 (48%)  Retromeatal 28 (52%) Tumor size  Small (<1 cm) 0  Medium (1-2.4 cm) 2 (4%)  Large (2.5-4.4 cm) 24 (44%)  Giant (>4.5 cm) 28 (52%) KPS (mean ± SD) 79 ± 17 Brainstem compression 24 (44%) Other deficits  None 17 (31%)  CN III 2 (4%)  CN IV 2 (4%)  CN V 10 (18%)  CN VI 3 (5%)  CN VII 7 (13%)  CN VIII 12 (22%)  CN IX X XI 7 (13%)  CN XII 0  Cerebellar dysfunctions 13 (24%)  Motor deficits 9 (17%)  Sensory deficit 1 (2%) Variables N° Patients Age (mean ± SD) 56.7 ± 14.2 Sex  M 9 (17%)  F 45 (83%) Type of meningioma  Premeatal 26 (48%)  Retromeatal 28 (52%) Tumor size  Small (<1 cm) 0  Medium (1-2.4 cm) 2 (4%)  Large (2.5-4.4 cm) 24 (44%)  Giant (>4.5 cm) 28 (52%) KPS (mean ± SD) 79 ± 17 Brainstem compression 24 (44%) Other deficits  None 17 (31%)  CN III 2 (4%)  CN IV 2 (4%)  CN V 10 (18%)  CN VI 3 (5%)  CN VII 7 (13%)  CN VIII 12 (22%)  CN IX X XI 7 (13%)  CN XII 0  Cerebellar dysfunctions 13 (24%)  Motor deficits 9 (17%)  Sensory deficit 1 (2%) SD, standard deviation; KPS, Karnofsky performance status; CN, cranial nerve View Large Study Size A total of 54 patients with PMs were included in this study. The eligibility criteria included age of ≥18 yr and a PM with limited to the posterior cranial fossa. Patients who had undergone previous surgical treatment and/or radiotherapy were included in this analysis. Patients harboring meningiomas outside the posterior cranial fossa were excluded from the analysis. All patients signed an informed consent for the scientific use of their data according to the requirements of the local Institutional Review Board. Data Sources Clinical and treatment data were retrospectively collected in a digital archive. Follow-up information was obtained by outpatient clinical evaluation or telephone interviews at defined time intervals. Variables We collected demographic and preoperative clinical data including age, sex, KPS, and neurological examination results. Preoperatively, each patient underwent a contrast-enhanced magnetic resonance (MR) scan, integrated with T2-weighted MR sequences. In most challenging cases, MR scans were integrated with arterial and venous MR angiograms. Tumor size was categorized as small (<1.0 cm), medium (1.0-2.4 cm), large (2.5-4.4 cm), or giant (>4.5 cm).3 Surgical Management PMs were classified as premeatal or retromeatal4,5 according to the relationship between the dural attachment and the internal acoustic meatus. The most commonly employed surgical approach was the retrosigmoid approach. In selected cases, according to the extent of the tumor and its relationship with vessel and nerves, the petrosal approach was adopted.6-10 The surgical strategy aimed to achieve gross total resection (GTR) while preserving neurological function. For this purpose, we considered relationships between the tumor and the brainstem and the preservation of an arachnoidal plane between the tumor and the brainstem. IONM was carried out through evaluation of motor evoked potentials (MEPs) of the corticobulbar and corticospinal tracts, somatosensory evoked potentials (SEPs), brainstem auditory evoked potentials (BAEPs), and both free-running and triggered bipolar electromyography (EMG; Figure 1). Data were recorded using an IONM workstation (NIM Eclipse; Medtronic, Dublin, Ireland). Worldwide recommendations on arrangement and stimulation parameters were adopted.7-10 The protocol used for anesthesiology has been reported elsewhere.11 Warning criteria included the following: (1) SEPs—a more than 50% drop in amplitude during 3 consecutive recordings;9 (2) MEPs—a decrease of 50% in amplitude;9 (3) BAEP—an increase in latency of waves III and IV/V for more than 0.5 ms and an amplitude decrease of more than 50%;9 (4) free-running EMG—the appearance of A-, B-, and C-trains;9 and (5) triggered EMG—the absence of a response.9 FIGURE 1. View largeDownload slide Case example showing a left premeatal meningioma. A, Preoperative axial contrast-enhanced T1 MR scan. B, Intraoperative stimulation of the VII nerve with a bipolar concentric probe at 0.20 mA. C, Postoperative axial contrast-enhanced T1 MR scan exhibiting a GTR. Mas, masseter muscle; Orb, orbicularis oris muscle; Nas, nasalis muscle; Sf, stylopharyngeus muscle; Tps, trapezius muscle. FIGURE 1. View largeDownload slide Case example showing a left premeatal meningioma. A, Preoperative axial contrast-enhanced T1 MR scan. B, Intraoperative stimulation of the VII nerve with a bipolar concentric probe at 0.20 mA. C, Postoperative axial contrast-enhanced T1 MR scan exhibiting a GTR. Mas, masseter muscle; Orb, orbicularis oris muscle; Nas, nasalis muscle; Sf, stylopharyngeus muscle; Tps, trapezius muscle. Endoscopic assistance was performed with a rigid endoscope without a working channel (18 cm length, 4 mm, 0° and 30°; Karl Storz GmbH & Co KG, Tuttlingen, Germany) associated with a high-definition camera.12-14 The endoscope was used free-hand during the tumor removal in order to improve the surgeon's microscopic view, reducing the neurovascular retraction necessary to gain access to blind corners.15 If tumor remnants were identified and their removal was judged safe, they were taken out under endoscopic vision. ICG was used during the surgical procedure and after the meningioma removal (Figure 2). The suggested dose of ICG for videoangiography is 0.2 to 0.5 mg/kg.16,17 The intravascular dye was displayed through an operating microscope (OPMI Pentero; Carl Zeiss Meditec, Jena, Germany) equipped with an additional fluorescent light source (wavelength 700-850 nm).17 ICG was employed to assess the patency of critical vascular structures and the microvascularization of cranial nerves. FIGURE 2. View largeDownload slide Case example showing a left premeatal meningioma. A, Preoperative axial contrast-enhanced T1 MR scan. B, Postoperative axial contrast-enhanced T1 MR scan exhibiting a GTR. C, ICG videoangiography showing the preservation of microvascularization of cranial nerves V and VIII. D, Endoscopic view of cranial nerves V, VI, and VIII at the end of tumor removal. FIGURE 2. View largeDownload slide Case example showing a left premeatal meningioma. A, Preoperative axial contrast-enhanced T1 MR scan. B, Postoperative axial contrast-enhanced T1 MR scan exhibiting a GTR. C, ICG videoangiography showing the preservation of microvascularization of cranial nerves V and VIII. D, Endoscopic view of cranial nerves V, VI, and VIII at the end of tumor removal. Adjuvant Treatment Patients with subtotal resection (STR) and partial resection (PR) and patients with recurrent tumors after GTR were referred for postoperative adjuvant radiosurgery treatment.18-20 Patients underwent single session radiosurgery (median dose 14 Gy; range 13-15 Gy) using a LINAC frame-based system (3D-Line; Medica Systems, Milan, Italy) between 1997 and 2006 and 3 to 5 sessions (median 5) and 21 to 25 (median 25) Gy using a CyberKnife system (Accuray Inc, Sunnyvale, California) from 2007 onward. Assessment of Outcome and Quantitative Variables To avoid inconsistent interpretation, we evaluated clinical results according to numerical scales. The variables that were examined as independent predictors of outcome were as follows: (1) location of the tumor, (2) size of the lesion, (3) occurrence of preoperative neurological deficits, (4) presence of brainstem compression, (5) histological grading, (6) use of multimodal intraoperative tools to support microsurgical resection, (7) previous surgery, and (8) Simpson resection grade. The outcome variables included EOR and KPS analysis at long-term follow-up. OS and PFS were also analyzed. Postoperative magnetic resonance imaging studies were obtained before discharge, 3 to 6 mo postoperatively and yearly thereafter.21 The EOR was evaluated through postoperative contrast-enhanced MR.22 Postoperative radiological and clinical data were collected and stored during the outpatient visits and then reviewed and discussed by a multidisciplinary tumor board, where independent neuroradiologists provided the final evaluation of the EOR and recurrence. EOR was classified as GTR, STR (<10% of tumor remnant) or PR (>10% of tumor remnant). Simpson grade was analyzed as defined from both operative reports and postoperative images. Tumor recurrence was defined as any new, unequivocal enhancement seen in the resection cavity; tumor progression was defined as any unequivocal increase in size of the residual tumor seen on postoperative imaging (for the purpose of comparing tumor control rates, recurrence and progression were treated as similar events21). OS was defined as the time between initial surgery and death, while PFS was expressed as the time between initial surgery and either demonstration of recurrence/progression or death. Long-term follow-up evaluations were conducted by collecting medical records and by performing telephone interviews. When available, the latest MR scans and radiological reports were collected. Statistical Methods For all preoperative, surgical, and outcome variables, percentages of frequency distributions were analyzed. For the statistical analysis, variables were sorted as indicated below. A multivariate analysis was performed by using the multiple logistic regression method. Variables were transformed into binary variables to be used in the logistic regression model.23 The dichotomous variables were preoperative neurological deficit, brainstem compression, use of the multimodal intraoperative protocol, and previous surgery. For nondichotomous variables, cut-off values were chosen according to clinical criteria and published data. The subsets for predictors and outcome variables were as follows: location, premeatal vs retromeatal; tumor size, small to large vs giant; histological grade, grade I vs grades II/III; EOR, GTR vs other EOR; KPS, improved/unchanged vs worsened; Simpson grade, grade I vs other grades. OS and PFS analyses were performed by using the Kaplan–Meier method. The log-rank test was used to compare OS and PFS curves for each pre- and intraoperative variable. The accuracy of the IONM was assessed by using Fisher's exact test and by analyzing the specificity, sensitivity, and positive and negative predictive values (PPVs and NPVs). Contingency tables for size-related groups (small, medium, large, and giant) were analyzed by the chi-squared test. Statistical significance was defined as a P value < .05, and the odds ratio (OR) for each variable was reported. The multivariate analysis was accomplished by using the software STATCALC 8.2.2 (AcaStat, Poinciana, Florida; www.acastat.com). OS, PFS, and IONM analyses were performed in GraphPad Prism version 6.00 for Windows (GraphPad Software, La Jolla, California; www.graphpad.com). RESULTS Participants A total of 54 patients with PMs were included in this study. Table 2 summarizes the results of surgical treatment. TABLE 2. Follow-up Data and Results of Surgery Variables No. patient (percentage) Follow-up range (months) 6-189 Follow-up mean (months) 58 EOR  GTR 35 (70%)  Subtotal resection 13 (26%)  Partial resection 2 (4%) Simpson grade  I 6 (12%)  II 29 (58%)  III 13 (26%)  IV 2 (4%) Surgical approaches  Retrosigmoid 51 (94%)  Combined petrosal 3 (6%) Histology  WHO grade I 50 (93%)  WHO grade II 3 (5%)  WHO grade III 1 (2%) Postoperative complications  CSF leakage 0  Hydrocephalus 3 (6%)  Brainstem or cerebellar Ischemia 3 (6%)  Hemorrhage 0  Infection 0 Perioperative mortality  Brainstem and cerebellar ischemia 2 (4%)  Myocardial infarction 1 (2%)  Inhalation pneumonia 1 (2%) KPS at follow-up  KPS improved 18 (36%)  KPS worsened 16 (32%)  KPS unchanged 16 (32%) Survival at follow-up  Alive 40 (87%)  Long-term mortality for disease 4 (9%)  Long-term mortality for other reasons 2 (4%) Recurrence rate 8 (16%) Variables No. patient (percentage) Follow-up range (months) 6-189 Follow-up mean (months) 58 EOR  GTR 35 (70%)  Subtotal resection 13 (26%)  Partial resection 2 (4%) Simpson grade  I 6 (12%)  II 29 (58%)  III 13 (26%)  IV 2 (4%) Surgical approaches  Retrosigmoid 51 (94%)  Combined petrosal 3 (6%) Histology  WHO grade I 50 (93%)  WHO grade II 3 (5%)  WHO grade III 1 (2%) Postoperative complications  CSF leakage 0  Hydrocephalus 3 (6%)  Brainstem or cerebellar Ischemia 3 (6%)  Hemorrhage 0  Infection 0 Perioperative mortality  Brainstem and cerebellar ischemia 2 (4%)  Myocardial infarction 1 (2%)  Inhalation pneumonia 1 (2%) KPS at follow-up  KPS improved 18 (36%)  KPS worsened 16 (32%)  KPS unchanged 16 (32%) Survival at follow-up  Alive 40 (87%)  Long-term mortality for disease 4 (9%)  Long-term mortality for other reasons 2 (4%) Recurrence rate 8 (16%) EOR, extent of resection; KPS, Karnofsky performance status View Large TABLE 2. Follow-up Data and Results of Surgery Variables No. patient (percentage) Follow-up range (months) 6-189 Follow-up mean (months) 58 EOR  GTR 35 (70%)  Subtotal resection 13 (26%)  Partial resection 2 (4%) Simpson grade  I 6 (12%)  II 29 (58%)  III 13 (26%)  IV 2 (4%) Surgical approaches  Retrosigmoid 51 (94%)  Combined petrosal 3 (6%) Histology  WHO grade I 50 (93%)  WHO grade II 3 (5%)  WHO grade III 1 (2%) Postoperative complications  CSF leakage 0  Hydrocephalus 3 (6%)  Brainstem or cerebellar Ischemia 3 (6%)  Hemorrhage 0  Infection 0 Perioperative mortality  Brainstem and cerebellar ischemia 2 (4%)  Myocardial infarction 1 (2%)  Inhalation pneumonia 1 (2%) KPS at follow-up  KPS improved 18 (36%)  KPS worsened 16 (32%)  KPS unchanged 16 (32%) Survival at follow-up  Alive 40 (87%)  Long-term mortality for disease 4 (9%)  Long-term mortality for other reasons 2 (4%) Recurrence rate 8 (16%) Variables No. patient (percentage) Follow-up range (months) 6-189 Follow-up mean (months) 58 EOR  GTR 35 (70%)  Subtotal resection 13 (26%)  Partial resection 2 (4%) Simpson grade  I 6 (12%)  II 29 (58%)  III 13 (26%)  IV 2 (4%) Surgical approaches  Retrosigmoid 51 (94%)  Combined petrosal 3 (6%) Histology  WHO grade I 50 (93%)  WHO grade II 3 (5%)  WHO grade III 1 (2%) Postoperative complications  CSF leakage 0  Hydrocephalus 3 (6%)  Brainstem or cerebellar Ischemia 3 (6%)  Hemorrhage 0  Infection 0 Perioperative mortality  Brainstem and cerebellar ischemia 2 (4%)  Myocardial infarction 1 (2%)  Inhalation pneumonia 1 (2%) KPS at follow-up  KPS improved 18 (36%)  KPS worsened 16 (32%)  KPS unchanged 16 (32%) Survival at follow-up  Alive 40 (87%)  Long-term mortality for disease 4 (9%)  Long-term mortality for other reasons 2 (4%) Recurrence rate 8 (16%) EOR, extent of resection; KPS, Karnofsky performance status View Large Descriptive Data Twenty-six patients (48%) harbored premeatal meningiomas, while 28 (52%) had retromeatal meningiomas. Two patients had been previously treated by surgery only, and 1 by surgery followed by radiotherapy. Three patients were affected by multiple meningiomas. Fifty-two percent of patients had giant meningiomas. The retrosigmoid approach alone was used in 94% of cases, while a combined pre- and retrosigmoid approach was adopted in 3 patients (6%). Ninety-three percent of patients had a WHO grade I meningioma, 5% WHO grade II, and 2% WHO grade III. The follow-up period ranged from 6 to 189 mo, with a mean of 58 mo. Four patients were lost to follow-up and, therefore, were excluded from the long-term outcome and multivariate analysis. Main Results A surgical complication requiring a second surgery occurred in 6 patients (11%). The overall morbidity rate was 18%, consisting of a new or worsened cranial nerve deficit in 11% of cases and a new or worsened motor deficit in the remaining cases. Perioperative mortality (within 30 d after the surgical procedure) was 8% (Table 2) and exclusively involved patients who harbored premeatal meningiomas presenting a preoperative KPS score <60 together with cranial nerve deficits and limb motor deficits. The causes of mortality were brainstem and cerebellar ischemia in 2 cases, inhalation pneumonia in 1 case, and myocardial infarction in 1 case. The overall EOR analysis revealed a GTR in 70% of patients, an STR in 26%, and a PR in 4%. The KPS analysis at the follow-up evaluation revealed that 36% of patients were improved, 32% were unchanged, and 32% were worsened. At the follow-up examination, 87% of patients were alive, 9% were deceased from disease recurrence or progression, and 4% had died of other causes. Thirty-nine percent of patients (21/54) with subtotal or partial resection or with tumor recurrence (16%) had undergone single or multisession radiosurgery at the time of analysis. The multimodal intraoperative protocol was adopted for 22 patients (from 2007 onward). Factors Affecting Outcome When a multivariate analysis was performed, a retromeatal location (P = .0175; OR 4.05), the absence of brainstem compression (P = .02; OR 3.55), a WHO grade of I (P = .001; OR 3.47), and the use of a multimodal intraoperative strategy (P < .002; OR 6.8) were found to be independent predictors of GTR achievement (Table 3). A detailed examination of results by meningioma size category (Table 4) showed that the probability of a poor KPS, but not perioperative mortality, was highest for patients with giant meningiomas (P = .04). TABLE 3. Results of Multivariate, OS, and PFS Analyses Location Size Preoperative deficits Brainstem compression WHO grade Multimodal intraoperative protocol EOR P = .0175 (OR 4.05) – – P = .02 (OR 3.55) P < .001 (OR 3.47) P = .002 (OR 6.8) KPS – P = .012 (OR 4.38) – – P < .0001 (OR 7.7) P = .018 (OR 4.23) Perioperative mortality – – – – – – PFS – P = .01 – – P = .002 – Location Size Preoperative deficits Brainstem compression WHO grade Multimodal intraoperative protocol EOR P = .0175 (OR 4.05) – – P = .02 (OR 3.55) P < .001 (OR 3.47) P = .002 (OR 6.8) KPS – P = .012 (OR 4.38) – – P < .0001 (OR 7.7) P = .018 (OR 4.23) Perioperative mortality – – – – – – PFS – P = .01 – – P = .002 – EOR, extent of resection; GTR, gross total resection; KPS, Karnofsky performance status; PFS, progression-free survival; OR, odds ratio; NS, not significant; WHO, World Health Organization View Large TABLE 3. Results of Multivariate, OS, and PFS Analyses Location Size Preoperative deficits Brainstem compression WHO grade Multimodal intraoperative protocol EOR P = .0175 (OR 4.05) – – P = .02 (OR 3.55) P < .001 (OR 3.47) P = .002 (OR 6.8) KPS – P = .012 (OR 4.38) – – P < .0001 (OR 7.7) P = .018 (OR 4.23) Perioperative mortality – – – – – – PFS – P = .01 – – P = .002 – Location Size Preoperative deficits Brainstem compression WHO grade Multimodal intraoperative protocol EOR P = .0175 (OR 4.05) – – P = .02 (OR 3.55) P < .001 (OR 3.47) P = .002 (OR 6.8) KPS – P = .012 (OR 4.38) – – P < .0001 (OR 7.7) P = .018 (OR 4.23) Perioperative mortality – – – – – – PFS – P = .01 – – P = .002 – EOR, extent of resection; GTR, gross total resection; KPS, Karnofsky performance status; PFS, progression-free survival; OR, odds ratio; NS, not significant; WHO, World Health Organization View Large TABLE 4. Preoperative Characteristics and Postoperative Results According to Tumor Size Variables Small (<1.0 cm) Medium (1-2.4 cm) Large (2.5-4.4 cm) Giant (>4.5 cm) P value Type of meningioma –  Premeatal 0 0 10 (42%) 16 (57%)  Retromeatal 0 2 (100%) 14 (58%) 12 (43%) Neurological deficits –  None 0 2 (100%) 9 (37%) 6 (21%)  III CN 0 0 1 (4%) 1 (3%)  IV CN 0 0 0 2 (7%)  V CN 0 0 6 (25%) 4 (14%)  VI CN 0 0 0 3 (11%)  VII CN 0 0 2 (8%) 5 (18%)  VIII CN 0 0 5 (21%) 7 (25%)  IX-X-XI CN 0 0 2 (8%) 5 (18%)  XII CN 0 0 0 0  Cerebellar dysfunctions 0 0 5 (21%) 8 (28%)  Motor deficits 0 0 3 (12%) 6 (21%)  Sensory deficit 0 0 1 (4%) 0 EOR –  GTR 0 2 (100%) 18 (78%) 15 (60%)  Subtotal resection 0 0 5 (22%) 8 (32%)  Partial resection 0 0 0 2 (8%) Simpson grade –  I 0 0 3 (13%) 3 (12%)  II 0 2 (100%) 15 (65%) 12 (48%)  III 0 0 5 (22%) 8 (32%)  IV 0 0 0 2 (8%) Histology –  WHO grade I 0 2 (100%) 23 (96%) 25 (89%)  WHO grade II 0 0 1 (4%) 2 (7%)  WHO grade III 0 0 0 1 (4%) Postoperative complications –  CSF leakage 0 0 0 0  Hydrocephalus 0 0 1 (4%) 2 (8%)  Brainstem or cerebellar Ischemia 0 0 1 (4%) 2 (8%)  Hemorrhage 0 0 0 0  Infection 0 0 0 0 Perioperative mortality –  Brainstem and cerebellar ischemia 0 0 1 (4%) 1 (3%)  Myocardial infarction 0 0 0 1 (3%)  Inhalation pneumonia 0 0 0 1 (3%) KPS at follow-up P = .04  KPS improved 0 0 10 (44%) 8 (32%)  KPS worsened 0 0 4 (17%) 12 (48%)  KPS unchanged 0 2 (100%) 9 (39%) 5 (20%) Survival at follow-up –  Alive 0 2 (100%) 19 (86%) 19 (86%)  Long-term mortality for disease 0 0 2 (9%) 2 (9%)  Long-term mortality for other reasons 0 0 1 (5%) 1 (5%) Recurrence rate 0 0 1 (4%) 7 (28%) – Variables Small (<1.0 cm) Medium (1-2.4 cm) Large (2.5-4.4 cm) Giant (>4.5 cm) P value Type of meningioma –  Premeatal 0 0 10 (42%) 16 (57%)  Retromeatal 0 2 (100%) 14 (58%) 12 (43%) Neurological deficits –  None 0 2 (100%) 9 (37%) 6 (21%)  III CN 0 0 1 (4%) 1 (3%)  IV CN 0 0 0 2 (7%)  V CN 0 0 6 (25%) 4 (14%)  VI CN 0 0 0 3 (11%)  VII CN 0 0 2 (8%) 5 (18%)  VIII CN 0 0 5 (21%) 7 (25%)  IX-X-XI CN 0 0 2 (8%) 5 (18%)  XII CN 0 0 0 0  Cerebellar dysfunctions 0 0 5 (21%) 8 (28%)  Motor deficits 0 0 3 (12%) 6 (21%)  Sensory deficit 0 0 1 (4%) 0 EOR –  GTR 0 2 (100%) 18 (78%) 15 (60%)  Subtotal resection 0 0 5 (22%) 8 (32%)  Partial resection 0 0 0 2 (8%) Simpson grade –  I 0 0 3 (13%) 3 (12%)  II 0 2 (100%) 15 (65%) 12 (48%)  III 0 0 5 (22%) 8 (32%)  IV 0 0 0 2 (8%) Histology –  WHO grade I 0 2 (100%) 23 (96%) 25 (89%)  WHO grade II 0 0 1 (4%) 2 (7%)  WHO grade III 0 0 0 1 (4%) Postoperative complications –  CSF leakage 0 0 0 0  Hydrocephalus 0 0 1 (4%) 2 (8%)  Brainstem or cerebellar Ischemia 0 0 1 (4%) 2 (8%)  Hemorrhage 0 0 0 0  Infection 0 0 0 0 Perioperative mortality –  Brainstem and cerebellar ischemia 0 0 1 (4%) 1 (3%)  Myocardial infarction 0 0 0 1 (3%)  Inhalation pneumonia 0 0 0 1 (3%) KPS at follow-up P = .04  KPS improved 0 0 10 (44%) 8 (32%)  KPS worsened 0 0 4 (17%) 12 (48%)  KPS unchanged 0 2 (100%) 9 (39%) 5 (20%) Survival at follow-up –  Alive 0 2 (100%) 19 (86%) 19 (86%)  Long-term mortality for disease 0 0 2 (9%) 2 (9%)  Long-term mortality for other reasons 0 0 1 (5%) 1 (5%) Recurrence rate 0 0 1 (4%) 7 (28%) – View Large TABLE 4. Preoperative Characteristics and Postoperative Results According to Tumor Size Variables Small (<1.0 cm) Medium (1-2.4 cm) Large (2.5-4.4 cm) Giant (>4.5 cm) P value Type of meningioma –  Premeatal 0 0 10 (42%) 16 (57%)  Retromeatal 0 2 (100%) 14 (58%) 12 (43%) Neurological deficits –  None 0 2 (100%) 9 (37%) 6 (21%)  III CN 0 0 1 (4%) 1 (3%)  IV CN 0 0 0 2 (7%)  V CN 0 0 6 (25%) 4 (14%)  VI CN 0 0 0 3 (11%)  VII CN 0 0 2 (8%) 5 (18%)  VIII CN 0 0 5 (21%) 7 (25%)  IX-X-XI CN 0 0 2 (8%) 5 (18%)  XII CN 0 0 0 0  Cerebellar dysfunctions 0 0 5 (21%) 8 (28%)  Motor deficits 0 0 3 (12%) 6 (21%)  Sensory deficit 0 0 1 (4%) 0 EOR –  GTR 0 2 (100%) 18 (78%) 15 (60%)  Subtotal resection 0 0 5 (22%) 8 (32%)  Partial resection 0 0 0 2 (8%) Simpson grade –  I 0 0 3 (13%) 3 (12%)  II 0 2 (100%) 15 (65%) 12 (48%)  III 0 0 5 (22%) 8 (32%)  IV 0 0 0 2 (8%) Histology –  WHO grade I 0 2 (100%) 23 (96%) 25 (89%)  WHO grade II 0 0 1 (4%) 2 (7%)  WHO grade III 0 0 0 1 (4%) Postoperative complications –  CSF leakage 0 0 0 0  Hydrocephalus 0 0 1 (4%) 2 (8%)  Brainstem or cerebellar Ischemia 0 0 1 (4%) 2 (8%)  Hemorrhage 0 0 0 0  Infection 0 0 0 0 Perioperative mortality –  Brainstem and cerebellar ischemia 0 0 1 (4%) 1 (3%)  Myocardial infarction 0 0 0 1 (3%)  Inhalation pneumonia 0 0 0 1 (3%) KPS at follow-up P = .04  KPS improved 0 0 10 (44%) 8 (32%)  KPS worsened 0 0 4 (17%) 12 (48%)  KPS unchanged 0 2 (100%) 9 (39%) 5 (20%) Survival at follow-up –  Alive 0 2 (100%) 19 (86%) 19 (86%)  Long-term mortality for disease 0 0 2 (9%) 2 (9%)  Long-term mortality for other reasons 0 0 1 (5%) 1 (5%) Recurrence rate 0 0 1 (4%) 7 (28%) – Variables Small (<1.0 cm) Medium (1-2.4 cm) Large (2.5-4.4 cm) Giant (>4.5 cm) P value Type of meningioma –  Premeatal 0 0 10 (42%) 16 (57%)  Retromeatal 0 2 (100%) 14 (58%) 12 (43%) Neurological deficits –  None 0 2 (100%) 9 (37%) 6 (21%)  III CN 0 0 1 (4%) 1 (3%)  IV CN 0 0 0 2 (7%)  V CN 0 0 6 (25%) 4 (14%)  VI CN 0 0 0 3 (11%)  VII CN 0 0 2 (8%) 5 (18%)  VIII CN 0 0 5 (21%) 7 (25%)  IX-X-XI CN 0 0 2 (8%) 5 (18%)  XII CN 0 0 0 0  Cerebellar dysfunctions 0 0 5 (21%) 8 (28%)  Motor deficits 0 0 3 (12%) 6 (21%)  Sensory deficit 0 0 1 (4%) 0 EOR –  GTR 0 2 (100%) 18 (78%) 15 (60%)  Subtotal resection 0 0 5 (22%) 8 (32%)  Partial resection 0 0 0 2 (8%) Simpson grade –  I 0 0 3 (13%) 3 (12%)  II 0 2 (100%) 15 (65%) 12 (48%)  III 0 0 5 (22%) 8 (32%)  IV 0 0 0 2 (8%) Histology –  WHO grade I 0 2 (100%) 23 (96%) 25 (89%)  WHO grade II 0 0 1 (4%) 2 (7%)  WHO grade III 0 0 0 1 (4%) Postoperative complications –  CSF leakage 0 0 0 0  Hydrocephalus 0 0 1 (4%) 2 (8%)  Brainstem or cerebellar Ischemia 0 0 1 (4%) 2 (8%)  Hemorrhage 0 0 0 0  Infection 0 0 0 0 Perioperative mortality –  Brainstem and cerebellar ischemia 0 0 1 (4%) 1 (3%)  Myocardial infarction 0 0 0 1 (3%)  Inhalation pneumonia 0 0 0 1 (3%) KPS at follow-up P = .04  KPS improved 0 0 10 (44%) 8 (32%)  KPS worsened 0 0 4 (17%) 12 (48%)  KPS unchanged 0 2 (100%) 9 (39%) 5 (20%) Survival at follow-up –  Alive 0 2 (100%) 19 (86%) 19 (86%)  Long-term mortality for disease 0 0 2 (9%) 2 (9%)  Long-term mortality for other reasons 0 0 1 (5%) 1 (5%) Recurrence rate 0 0 1 (4%) 7 (28%) – View Large At follow-up, 36% of patients had an improved neurological status, 32% were unchanged, and 32% had worsened. The multivariate analysis showed that nongiant tumor size (P = .012; OR 4.38), a WHO grade of I (P < .0001; OR 7.7), and the use of the multimodal intraoperative protocol (P = .018; OR 4.23) were independent predictors of good KPS (Table 3). Finally, nongiant meningioma size (P = .01) and a WHO grade of I (P = .002) were significantly associated with increased PFS (Table 3; Figures 3 and 4). FIGURE 3. View largeDownload slide Kaplan–Meier progression-free survival (PFS) analysis of subgroups of patients defined by tumor size (small to large vs giant) showed a significant difference (P = .01). FIGURE 3. View largeDownload slide Kaplan–Meier progression-free survival (PFS) analysis of subgroups of patients defined by tumor size (small to large vs giant) showed a significant difference (P = .01). DISCUSSION Key Results In this retrospective single-center study, we reported the surgical results obtained from patients affected by PMs and operated on by the same surgeon over the past 2 decades. Our analysis showed that a retromeatal location, absence of brainstem compression, and a histological WHO grade of I predicted GTR, whereas giant size affected the postoperative KPS and produced a tendency toward elevated postoperative mortality. Notably, the adoption of multimodal intraoperative tools to assist surgery independently allowed the achievement of GTR and a good postoperative KPS. Interpretation The main goal of the study was the identification of factors predicting the EOR and the functional outcome. As expected, the site of meningioma attachment was a significant predictor of outcome. Indeed, meningiomas located ventral to the internal acoustic meatus dislocate posteriorly the neural and vascular structures of the cerebellopontine angle (CPA).24 This setting complicates surgical removal because the resection must be performed in the midst of vital neurovascular structures and along a narrower surgical corridor.5 In particular, the acoustic-facial bundle is at risk of surgical injury. Nakamura et al25 described an improved facial nerve outcome in “CPA meningiomas” when the site of tumor origin was superior or posterior to the IAC. Nevertheless, as the facial nerve is more resilient to surgical trauma, new-onset facial nerve deficits are less common than those involving the cochlear nerve.26 Deficits involving the sixth, ninth, and tenth cranial nerves have occasionally been reported in premeatal meningiomas. Brainstem lesions are also possible with large premeatal tumors, particularly with in lesions receiving a vascular supply from pial vessels. Furthermore, because of the difficulties encountered in safely removing ventral PMs, the rate of GTR is lower for this group of tumors than for retromeatal tumors.26 In the present series, smaller tumors not compressing the brainstem led to a GTR in 92% of cases. Moreover, a WHO grade I was associated with an elevated probability of GTR and improved postoperative performance status as a result of a preserved arachnoid layer protecting the brainstem and neurovascular structures of the CPA. These patients also had better PFS than those affected by giant tumors (P = .01) or WHO grade II or III tumors (P = .002). In Table 5, the overall results of our series are compared with those published in similar studies.1,2,5,25-33 TABLE 5. Literature Review About Petrous Bone Meningiomas Published Series Author and year N° patients Classifications Surgical approaches (%) GTR (%) Follow-up range (mo) Mean follow-up (mo) Recurrence rate Morbidity (%) Perioperative mortality (%) Schaller et al, 19995 31 Premeatal, retromeatal Retrosigmoid (100%) NA 12-168 84 3% 23% 0% Selesnick et al, 200133 12 NA Retrosigmoid (100%) GTR 50% 6-42 NA 8% 33% NA Liu et al, 200329 21 Posterior PM (posterior to the IAC) Retrosigmoid (80%) translabyrinthine (10%) petrosal (10%) GTR 86% NA NA NA 38% 0% Bassiouni et al, 200428 51 Postmeatal, premeatal, suprameatal inframeatal centered on the porus acusticus Retrosigmoid (100%) GTR 84% 13-156 70 4% NA 0% Nakamura et al, 200525 334 Anterior to the IAC, involvement of the IAC, superior to the IAC, inferior to the IAC Retrosigmoid (95%) combined supratentorial-infratentorial presigmoid (5%) GTR 86% 2-214 62 NA 15% 0.6% Wu et al, 200534 82 Type I: laterally to IAC; type II: medially to IAC; type III: attached to the posterior surface of the petrous bone Retrosigmoid (78%) subtemporal transtentorial (10%) presigmoid (12%) GTR 83% 6-96 4.5 NA 16% 0% Deveze et al, 20071 43 Type A: anterior to the IAC; type M: meatal; type P: posterior to the IAC Widened retrolabyrinthine (47%) translabyrinthine (44%) Transotic (2%) transcochlear (7%) GTR 79% 3-120 34 5% 37% 0% Sanna et al, 200731 81 Posterior petrous face Enlarged translabyrinthine (38%) enlarged translabyrinthine with transapical extension (36%) combined retrosigmoid-retrolabyrinthine (10%) modified transcochlear (7%) retrolabyrinthine subtemporal transapical (2%) transpetrous middle cranial fossa (2%) middle cranial fossa approach (5%) GTR 93% NA NA NA 10% 0% Sade and Lee, 200930 58 Posterior, superior and ventral to the IAC Retrosigmoid (100%) GTR 84% NA NA NA 17% NA Peyre et al, 201027 53 Posterior petrous, meatus and IAC, petroux apex w/o invasion of the IAC, CPA with invasion of the IAC Translabyrinthine (21%) enlarged translabyrinthine (21%) translabyrinthine and retrosigmoid (4%) transcochlear (11%) retrosigmoid (17%) retrosigmoid and retrolabyrinthine (13%) RS/RLII and subtemporal (2%) subtemporal with apical petrectomy (11%) GTR 72% NA 35 NA§ 25% NA§ Roche et al, 20112 57 Type A: around the porus trigeminus; type M: at the level of the porus of the IAC; type P: lateral to the IAC Anterior petrosectomy (49%) combined petrosectomy (10%) translabyrinthine (7%) retrolabyrinthine (5%) retrosigmoid (29%) GTR 39% NA§ NA§ 6% 6% 9% Nowak et al, 201330 48 Premeatal, inframeatal, retromeatal Retrosigmoid (79%) subtemporal and suboccipital (15%) combined translabyrinthine (2%) far lateral transcondylar (4%) GTR 94% 12-120 NA 4% 23% 4% Present study 54 Premeatal, retromeatal Retrosigmoid (94%) combined transpetrosal (6%) GTR 70% 6-189 58 16% 18% 8% Author and year N° patients Classifications Surgical approaches (%) GTR (%) Follow-up range (mo) Mean follow-up (mo) Recurrence rate Morbidity (%) Perioperative mortality (%) Schaller et al, 19995 31 Premeatal, retromeatal Retrosigmoid (100%) NA 12-168 84 3% 23% 0% Selesnick et al, 200133 12 NA Retrosigmoid (100%) GTR 50% 6-42 NA 8% 33% NA Liu et al, 200329 21 Posterior PM (posterior to the IAC) Retrosigmoid (80%) translabyrinthine (10%) petrosal (10%) GTR 86% NA NA NA 38% 0% Bassiouni et al, 200428 51 Postmeatal, premeatal, suprameatal inframeatal centered on the porus acusticus Retrosigmoid (100%) GTR 84% 13-156 70 4% NA 0% Nakamura et al, 200525 334 Anterior to the IAC, involvement of the IAC, superior to the IAC, inferior to the IAC Retrosigmoid (95%) combined supratentorial-infratentorial presigmoid (5%) GTR 86% 2-214 62 NA 15% 0.6% Wu et al, 200534 82 Type I: laterally to IAC; type II: medially to IAC; type III: attached to the posterior surface of the petrous bone Retrosigmoid (78%) subtemporal transtentorial (10%) presigmoid (12%) GTR 83% 6-96 4.5 NA 16% 0% Deveze et al, 20071 43 Type A: anterior to the IAC; type M: meatal; type P: posterior to the IAC Widened retrolabyrinthine (47%) translabyrinthine (44%) Transotic (2%) transcochlear (7%) GTR 79% 3-120 34 5% 37% 0% Sanna et al, 200731 81 Posterior petrous face Enlarged translabyrinthine (38%) enlarged translabyrinthine with transapical extension (36%) combined retrosigmoid-retrolabyrinthine (10%) modified transcochlear (7%) retrolabyrinthine subtemporal transapical (2%) transpetrous middle cranial fossa (2%) middle cranial fossa approach (5%) GTR 93% NA NA NA 10% 0% Sade and Lee, 200930 58 Posterior, superior and ventral to the IAC Retrosigmoid (100%) GTR 84% NA NA NA 17% NA Peyre et al, 201027 53 Posterior petrous, meatus and IAC, petroux apex w/o invasion of the IAC, CPA with invasion of the IAC Translabyrinthine (21%) enlarged translabyrinthine (21%) translabyrinthine and retrosigmoid (4%) transcochlear (11%) retrosigmoid (17%) retrosigmoid and retrolabyrinthine (13%) RS/RLII and subtemporal (2%) subtemporal with apical petrectomy (11%) GTR 72% NA 35 NA§ 25% NA§ Roche et al, 20112 57 Type A: around the porus trigeminus; type M: at the level of the porus of the IAC; type P: lateral to the IAC Anterior petrosectomy (49%) combined petrosectomy (10%) translabyrinthine (7%) retrolabyrinthine (5%) retrosigmoid (29%) GTR 39% NA§ NA§ 6% 6% 9% Nowak et al, 201330 48 Premeatal, inframeatal, retromeatal Retrosigmoid (79%) subtemporal and suboccipital (15%) combined translabyrinthine (2%) far lateral transcondylar (4%) GTR 94% 12-120 NA 4% 23% 4% Present study 54 Premeatal, retromeatal Retrosigmoid (94%) combined transpetrosal (6%) GTR 70% 6-189 58 16% 18% 8% GTR, gross total resection; IAC, internal acoustic canal; NA, not available; RS/RL, retrosigmoid/retrolabyrinthine View Large TABLE 5. Literature Review About Petrous Bone Meningiomas Published Series Author and year N° patients Classifications Surgical approaches (%) GTR (%) Follow-up range (mo) Mean follow-up (mo) Recurrence rate Morbidity (%) Perioperative mortality (%) Schaller et al, 19995 31 Premeatal, retromeatal Retrosigmoid (100%) NA 12-168 84 3% 23% 0% Selesnick et al, 200133 12 NA Retrosigmoid (100%) GTR 50% 6-42 NA 8% 33% NA Liu et al, 200329 21 Posterior PM (posterior to the IAC) Retrosigmoid (80%) translabyrinthine (10%) petrosal (10%) GTR 86% NA NA NA 38% 0% Bassiouni et al, 200428 51 Postmeatal, premeatal, suprameatal inframeatal centered on the porus acusticus Retrosigmoid (100%) GTR 84% 13-156 70 4% NA 0% Nakamura et al, 200525 334 Anterior to the IAC, involvement of the IAC, superior to the IAC, inferior to the IAC Retrosigmoid (95%) combined supratentorial-infratentorial presigmoid (5%) GTR 86% 2-214 62 NA 15% 0.6% Wu et al, 200534 82 Type I: laterally to IAC; type II: medially to IAC; type III: attached to the posterior surface of the petrous bone Retrosigmoid (78%) subtemporal transtentorial (10%) presigmoid (12%) GTR 83% 6-96 4.5 NA 16% 0% Deveze et al, 20071 43 Type A: anterior to the IAC; type M: meatal; type P: posterior to the IAC Widened retrolabyrinthine (47%) translabyrinthine (44%) Transotic (2%) transcochlear (7%) GTR 79% 3-120 34 5% 37% 0% Sanna et al, 200731 81 Posterior petrous face Enlarged translabyrinthine (38%) enlarged translabyrinthine with transapical extension (36%) combined retrosigmoid-retrolabyrinthine (10%) modified transcochlear (7%) retrolabyrinthine subtemporal transapical (2%) transpetrous middle cranial fossa (2%) middle cranial fossa approach (5%) GTR 93% NA NA NA 10% 0% Sade and Lee, 200930 58 Posterior, superior and ventral to the IAC Retrosigmoid (100%) GTR 84% NA NA NA 17% NA Peyre et al, 201027 53 Posterior petrous, meatus and IAC, petroux apex w/o invasion of the IAC, CPA with invasion of the IAC Translabyrinthine (21%) enlarged translabyrinthine (21%) translabyrinthine and retrosigmoid (4%) transcochlear (11%) retrosigmoid (17%) retrosigmoid and retrolabyrinthine (13%) RS/RLII and subtemporal (2%) subtemporal with apical petrectomy (11%) GTR 72% NA 35 NA§ 25% NA§ Roche et al, 20112 57 Type A: around the porus trigeminus; type M: at the level of the porus of the IAC; type P: lateral to the IAC Anterior petrosectomy (49%) combined petrosectomy (10%) translabyrinthine (7%) retrolabyrinthine (5%) retrosigmoid (29%) GTR 39% NA§ NA§ 6% 6% 9% Nowak et al, 201330 48 Premeatal, inframeatal, retromeatal Retrosigmoid (79%) subtemporal and suboccipital (15%) combined translabyrinthine (2%) far lateral transcondylar (4%) GTR 94% 12-120 NA 4% 23% 4% Present study 54 Premeatal, retromeatal Retrosigmoid (94%) combined transpetrosal (6%) GTR 70% 6-189 58 16% 18% 8% Author and year N° patients Classifications Surgical approaches (%) GTR (%) Follow-up range (mo) Mean follow-up (mo) Recurrence rate Morbidity (%) Perioperative mortality (%) Schaller et al, 19995 31 Premeatal, retromeatal Retrosigmoid (100%) NA 12-168 84 3% 23% 0% Selesnick et al, 200133 12 NA Retrosigmoid (100%) GTR 50% 6-42 NA 8% 33% NA Liu et al, 200329 21 Posterior PM (posterior to the IAC) Retrosigmoid (80%) translabyrinthine (10%) petrosal (10%) GTR 86% NA NA NA 38% 0% Bassiouni et al, 200428 51 Postmeatal, premeatal, suprameatal inframeatal centered on the porus acusticus Retrosigmoid (100%) GTR 84% 13-156 70 4% NA 0% Nakamura et al, 200525 334 Anterior to the IAC, involvement of the IAC, superior to the IAC, inferior to the IAC Retrosigmoid (95%) combined supratentorial-infratentorial presigmoid (5%) GTR 86% 2-214 62 NA 15% 0.6% Wu et al, 200534 82 Type I: laterally to IAC; type II: medially to IAC; type III: attached to the posterior surface of the petrous bone Retrosigmoid (78%) subtemporal transtentorial (10%) presigmoid (12%) GTR 83% 6-96 4.5 NA 16% 0% Deveze et al, 20071 43 Type A: anterior to the IAC; type M: meatal; type P: posterior to the IAC Widened retrolabyrinthine (47%) translabyrinthine (44%) Transotic (2%) transcochlear (7%) GTR 79% 3-120 34 5% 37% 0% Sanna et al, 200731 81 Posterior petrous face Enlarged translabyrinthine (38%) enlarged translabyrinthine with transapical extension (36%) combined retrosigmoid-retrolabyrinthine (10%) modified transcochlear (7%) retrolabyrinthine subtemporal transapical (2%) transpetrous middle cranial fossa (2%) middle cranial fossa approach (5%) GTR 93% NA NA NA 10% 0% Sade and Lee, 200930 58 Posterior, superior and ventral to the IAC Retrosigmoid (100%) GTR 84% NA NA NA 17% NA Peyre et al, 201027 53 Posterior petrous, meatus and IAC, petroux apex w/o invasion of the IAC, CPA with invasion of the IAC Translabyrinthine (21%) enlarged translabyrinthine (21%) translabyrinthine and retrosigmoid (4%) transcochlear (11%) retrosigmoid (17%) retrosigmoid and retrolabyrinthine (13%) RS/RLII and subtemporal (2%) subtemporal with apical petrectomy (11%) GTR 72% NA 35 NA§ 25% NA§ Roche et al, 20112 57 Type A: around the porus trigeminus; type M: at the level of the porus of the IAC; type P: lateral to the IAC Anterior petrosectomy (49%) combined petrosectomy (10%) translabyrinthine (7%) retrolabyrinthine (5%) retrosigmoid (29%) GTR 39% NA§ NA§ 6% 6% 9% Nowak et al, 201330 48 Premeatal, inframeatal, retromeatal Retrosigmoid (79%) subtemporal and suboccipital (15%) combined translabyrinthine (2%) far lateral transcondylar (4%) GTR 94% 12-120 NA 4% 23% 4% Present study 54 Premeatal, retromeatal Retrosigmoid (94%) combined transpetrosal (6%) GTR 70% 6-189 58 16% 18% 8% GTR, gross total resection; IAC, internal acoustic canal; NA, not available; RS/RL, retrosigmoid/retrolabyrinthine View Large In a subgroup of PM patients, we used multimodal intraoperative assistance with standard treatment paradigms. This resulted in an elevated GTR rate and an improved long-term functional outcome. This is, to the best of our knowledge, the first study that highlights the effects of such an integrated and multimodal operative setup on the surgical and clinical long-term outcome of patients after surgical PM resection. Nonetheless, previous studies have analyzed these techniques individually to establish their value in posterior cranial fossa surgery. Different IONM techniques have been used in posterior cranial fossa surgery. The largest clinical series was published in 2016 by Slotty et al.9 They presented results from 305 patients treated for infratentorial lesions with intraoperative cranial nerve, SEP, and MEP monitoring. They observed that the incidence of IONM alerts during posterior cranial fossa surgery varied according to lesion site and histopathology. In PM resection, most of the alterations concerned BAEPs and free-running and triggered EMG, while no alerts were recorded from SEP or MEP. Notably, the investigators observed that new neurological deficits without IONM alteration were recorded in 11.6% of cases. In our series, using the same technique (n = 22), we found a significant correlation between the use of IONM and preservation of cranial nerves and overall neurological function (Table 3). Furthermore, no patient presented any new postoperative deficit whose occurrence remained undetected by IONM. Accordingly, IONM had a sensitivity of 100%, a specificity of 94%, a PPV of 75%, and an NPV of 100%. There are few studies specifically addressing the issue of endoscopic assistance during skull base meningioma surgery.15,34,35 In 2011, Schroeder et al15 evaluated endoscopic assistance during the microsurgical resection of 46 skull base meningiomas. Among these, 23 involved the petrous bone. They found endoscopic assistance to be particularly helpful for locations such as petroclival region and in meningiomas extending deeply into the internal acoustic meatus. They concluded that endoscopic assistance was useful especially when GTR was planned before surgery, providing additional exposure of the operative field. In our series, we found that endoscopic assistance was useful during the tumor removal, reducing the neurovascular retraction necessary to access the blind corners and thus bringing about a higher rate of GTR. Regarding ICG videoangiography, data for the posterior cranial fossa and particularly for PMs are sporadic. The ICG videoangiography study of the microvascularization of neural structures provides useful prognostic information on the postoperative performance of cranial nerves. It is less clear whether this information can positively influence the surgical strategy. Two studies on the use of ICG videoangiography in brain tumor surgery36,37 describe the possibility of distinguishing between tumor-related and normal passing vessels and verifying the patency of blood vessels around a tumor such as the perforating arteries of the vertebral artery during its mobilization. The potential benefit in identifying adjacent venous sinuses and pial blood supply to the tumors before opening the dura mater has been reported as well.17 Additionally, ICG videoangiography can support the identification of the superior petrosal vein before dural incision to preserve its blood flow during the petrosal approach.38 FIGURE 4. View largeDownload slide Kaplan–Meier progression-free survival (PFS) analysis of subgroups of patients defined by WHO grade (I vs II-III) showed a significant difference (P = .002). FIGURE 4. View largeDownload slide Kaplan–Meier progression-free survival (PFS) analysis of subgroups of patients defined by WHO grade (I vs II-III) showed a significant difference (P = .002). Above all, we believe that ICG videoangiography evaluation of the microvasculature of cranial nerves and the integrity of such vessels may support tumor resection. Indeed, the combination of IONM and ICG videoangiography provides a unique form of intraoperative feedback on the functional status of neural structures and offers insights during the manipulation of such structures. This may eventually affect the neurological outcome, although such an effect still needs to be demonstrated in dedicated studies. Limitations The retrospective and single-center nature of this study carries the unavoidable selection and expertise biases typically associated with such study designs. Nevertheless, we tried to reduce biases related to the surgical learning curve by restricting the study interval to the past 2 decades and to surgery performed by a single author (FT). In this time frame, microsurgical techniques and surgeon experience were developed, but we recognize that a time frame spanning 2 decades and a relatively limited number of patients may reduce the generalizability of our findings. CONLUSION Petrosal meningiomas are challenging tumors to treat because of their relationship to critical neurovascular structures. Important technical advances to support microsurgery, including IONM, endoscopy, and ICG videoangiography, may be helpful in improving patient outcome. Our results confirm previous experiences, showing that premeatal meningiomas are very challenging lesions requiring judicious management, and suggest that multimodal intraoperative tools offer a reliable method to achieve satisfactory outcome in terms of EOR, functional results, and, ultimately, quality of life. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Deveze A , Franco-Vidal V , Liguoro D , Guerin J , Darrouzet V . Transpetrosal approaches for meningiomas of the posterior aspect of the petrous bone Results in 43 consecutive patients . Clin Neurol Neurosurg . 2007 ; 109 ( 7 ): 578 - 588 . Google Scholar CrossRef Search ADS PubMed 2. Roche PH , Lubrano V , Noudel R , Melot A , Regis J . Decision making for the surgical approach of posterior petrous bone meningiomas . Neurosurg Focus . 2011 ; 30 ( 5 ): E14 . Google Scholar CrossRef Search ADS PubMed 3. Natarajan SK , Sekhar LN , Schessel D , Morita A . Petroclival meningiomas: multimodality treatment and outcomes at long-term follow-up . Neurosurgery . 2007 ; 60 ( 6 ): 965 - 981 . Google Scholar CrossRef Search ADS PubMed 4. Samii MAM . Cerebellopontine angle meningiomas . In: Al-Mefty O , ed. Maningiomas . New york : Raven press ; 1991 : 503 - 515 . 5. Schaller B , Merlo A , Gratzl O , Probst R . Premeatal and retromeatal cerebellopontine angle meningioma. Two distinct clinical entities . Acta Neurochir (Wien) . 1999 ; 141 ( 5 ): 465 - 471 . Google Scholar CrossRef Search ADS PubMed 6. al-Mefty O , Ayoubi S , Smith RR . The petrosal approach: indications, technique, and results . Acta Neurochir Suppl (Wien) . 1991 ; 53 : 166 - 170 . Google Scholar CrossRef Search ADS PubMed 7. Macdonald DB , Skinner S , Shils J , Yingling C . American Society of Neurophysiological M. Intraoperative motor evoked potential monitoring-a position statement by the American Society of Neurophysiological Monitoring . Clin Neurophysiol . 2013 ; 124 ( 12 ): 2291 - 2316 . Google Scholar CrossRef Search ADS PubMed 8. Nuwer MR , Daube J , Fischer C , Schramm J , Yingling CD . Neuromonitoring during surgery. Report of an IFCN Committee . Electroencephalogr Clin Neurophysiol . 1993 ; 87 ( 5 ): 263 - 276 . Google Scholar CrossRef Search ADS PubMed 9. Slotty PJ , Abdulazim A , Kodama K et al. Intraoperative neurophysiological monitoring during resection of infratentorial lesions: the surgeon's view . J Neurosurg . 2017 ; 126 ( 1 ): 281 - 288 . Google Scholar CrossRef Search ADS PubMed 10. Szelenyi A , Kothbauer KF , Deletis V . Transcranial electric stimulation for intraoperative motor evoked potential monitoring: Stimulation parameters and electrode montages . Clin Neurophysiol . 2007 ; 118 ( 7 ): 1586 - 1595 . Google Scholar CrossRef Search ADS PubMed 11. Scibilia A , Raffa G , Rizzo V et al. Intraoperative neurophysiological monitoring in spine surgery: a significant tool for neuronal protection and functional restoration . Acta Neurochir Suppl . 2017 ; 124 : 263 - 270 . Google Scholar CrossRef Search ADS PubMed 12. Angileri FF , Esposito F , Priola SM et al. Fully endoscopic freehand evacuation of spontaneous supratentorial intraparenchymal hemorrhage . World Neurosurg . 2016 ; 94 : 268 - 272 . Google Scholar CrossRef Search ADS PubMed 13. d’Avella E , Angileri F , de Notaris M et al. Extended endoscopic endonasal transclival approach to the ventrolateral brainstem and related cisternal spaces: anatomical study . Neurosurg Rev . 2014 ; 37 ( 2 ): 253 - 260 . Google Scholar CrossRef Search ADS PubMed 14. Solari D , Chiaramonte C , Di Somma A et al. Endoscopic anatomy of the skull base explored through the nose . World Neurosurg . 2014 ; 82 ( 6 ): S164 - S170 . Google Scholar CrossRef Search ADS PubMed 15. Schroeder HW , Hickmann AK , Baldauf J . Endoscope-assisted microsurgical resection of skull base meningiomas . Neurosurg Rev . 2011 ; 34 ( 4 ): 441 - 455 . Google Scholar CrossRef Search ADS PubMed 16. Kim EH , Cho JM , Chang JH , Kim SH , Lee KS . Application of intraoperative indocyanine green videoangiography to brain tumor surgery . Acta Neurochir . 2011 ; 153 ( 7 ): 1487 - 1495 . Google Scholar CrossRef Search ADS PubMed 17. Ueba T , Okawa M , Abe H et al. Identification of venous sinus, tumor location, and pial supply during meningioma surgery by transdural indocyanine green videography . J Neurosurg . 2013 ; 118 ( 3 ): 632 - 636 . Google Scholar CrossRef Search ADS PubMed 18. Conti A , Pontoriero A , Midili F et al. CyberKnife multisession stereotactic radiosurgery and hypofractionated stereotactic radiotherapy for perioptic meningiomas: intermediate-term results and radiobiological considerations . Springerplus . 2015 ; 4 ( 1 ): 37 . Google Scholar CrossRef Search ADS PubMed 19. Conti A , Pontoriero A , Ricciardi GK et al. Integration of functional neuroimaging in CyberKnife radiosurgery: feasibility and dosimetric results . Neurosurg Focus . 2013 ; 34 ( 4 ): E5 . Google Scholar CrossRef Search ADS PubMed 20. Conti A , Pontoriero A , Salamone I et al. Protecting venous structures during radiosurgery for parasagittal meningiomas . Neurosurg Focus . 2009 ; 27 ( 5 ): E11 . Google Scholar CrossRef Search ADS PubMed 21. Tomasello F , Conti A , Cardali S , Angileri FF . Venous preservation-guided resection: a changing paradigm in parasagittal meningioma surgery . J Neurosurg . 2013 ; 119 ( 1 ): 74 - 81 . Google Scholar CrossRef Search ADS PubMed 22. Almefty R , Dunn IF , Pravdenkova S , Abolfotoh M , Al-Mefty O . True petroclival meningiomas: results of surgical management . J Neurosurg . 2014 ; 120 ( 1 ): 40 - 51 . Google Scholar CrossRef Search ADS PubMed 23. Conti A , Pontoriero A , Siddi F et al. Post-treatment edema after meningioma radiosurgery is a predictable complication . Cureus . 2016 ; 8 ( 5 ): e605 . Google Scholar PubMed 24. Seifert V . Clinical management of petroclival meningiomas and the eternal quest for preservation of quality of life . Acta Neurochir . 2010 ; 152 ( 7 ): 1099 - 1116 . Google Scholar CrossRef Search ADS PubMed 25. Nakamura M , Roser F , Dormiani M , Matthies C , Vorkapic P , Samii M . Facial and cochlear nerve function after surgery of cerebellopontine angle meningiomas . Neurosurgery . 2005 ; 57 ( 1 ): 77 - 90 . Google Scholar CrossRef Search ADS PubMed 26. Peyre M , Bozorg-Grayeli A , Rey A , Sterkers O , Kalamarides M . Posterior petrous bone meningiomas: surgical experience in 53 patients and literature review . Neurosurg Rev . 2012 ; 35 ( 1 ): 53 - 66 . Google Scholar CrossRef Search ADS PubMed 27. Bassiouni H , Hunold A , Asgari S , Stolke D . Meningiomas of the posterior petrous bone: functional outcome after microsurgery . J Neurosurg . 2004 ; 100 ( 6 ): 1014 - 1024 . Google Scholar CrossRef Search ADS PubMed 28. Liu JK , Gottfried ON , Couldwell WT . Surgical management of posterior petrous meningiomas . Neurosurg Focus . 2003 ; 14 ( 6 ): 1 - 7 . Google Scholar CrossRef Search ADS 29. Nowak A , Dziedzic T , Marchel A . Surgical management of posterior petrous meningiomas . Neurol Neurochir Pol . 2013 ; 47 ( 5 ): 456 - 466 . Google Scholar PubMed 30. Sade B , Lee JH . Ventral petrous meningiomas: unique tumors . Surg Neurol . 2009 ; 72 ( 1 ): 61 - 64 . Google Scholar CrossRef Search ADS PubMed 31. Sanna M , Bacciu A , Pasanisi E , Taibah A , Piazza P . Posterior petrous face meningiomas: an algorithm for surgical management . Otol Neurotol . 2007 ; 28 ( 7 ): 942 - 950 . Google Scholar CrossRef Search ADS PubMed 32. Selesnick SH , Nguyen TD , Gutin PH , Lavyne MH . Posterior petrous face meningiomas . Otolaryngol Head Neck Surg . 2001 ; 124 ( 4 ): 408 - 413 . Google Scholar CrossRef Search ADS PubMed 33. Wu ZB , Yu CJ , Guan SS . Posterior petrous meningiomas: 82 cases . J Neurosurg . 2005 ; 102 ( 2 ): 284 - 289 . Google Scholar CrossRef Search ADS PubMed 34. Abolfotoh M , Bi WL , Hong CK et al. The combined microscopic-endoscopic technique for radical resection of cerebellopontine angle tumors . J Neurosurg . 2015 ; 123 ( 5 ): 1301 - 1311 . Google Scholar CrossRef Search ADS PubMed 35. Tatagiba MS , Roser F , Hirt B , Ebner FH . The retrosigmoid endoscopic approach for cerebellopontine-angle tumors and microvascular decompression . World Neurosurg . 2014 ; 82 ( 6 ): S171 - S176 . Google Scholar CrossRef Search ADS PubMed 36. Ferroli P , Acerbi F , Albanese E et al. Application of intraoperative indocyanine green angiography for CNS tumors: results on the first 100 cases . Acta Neurochir Suppl . 2011 ; 109 : 251 - 257 . Google Scholar CrossRef Search ADS PubMed 37. Ferroli P , Acerbi F , Tringali G et al. Venous sacrifice in neurosurgery: new insights from venous indocyanine green videoangiography . J Neurosurg . 2011 ; 115 ( 1 ): 18 - 23 . Google Scholar CrossRef Search ADS PubMed 38. Haq IB , Susilo RI , Goto T , Ohata K . Dural incision in the petrosal approach with preservation of the superior petrosal vein . J Neurosurg . 2016 ; 124 ( 4 ): 1074 - 1078 . Google Scholar CrossRef Search ADS PubMed COMMENTS This paper retrospectively reviews a single surgeon, single institution series of 54 patients treated surgically for petrous meningiomas (PM) over 20 years. Not surprisingly, favorable tumor location, small size (with lack of brainstem compression), and benign histological grade were associated with better outcome. The authors also found that a systematic strategy using adjuvant intraoperative neuromonitoring, ICG videoangiography, and endoscopic visualization led to a higher rate of gross total resection and better long-term outcomes. This strategy was not employed until 2007 during the later half of the study epoch. It is difficult to know whether this study is measuring the effect of implementation of a combination of modern surgical adjuvants or the natural maturation of the skills of the operating surgeon. It is somewhat surprising that intraoperative cranial nerve monitoring was not employed prior to 2007. This is a well-established technology that has been employed for several decades to optimize cranial nerve outcome and extent of resection. The use of this technology alone beginning in 2007 would be expected to yield improved results. It is therefore difficult to parse out the added benefit of ICG videoangiography and endoscopy. These tools may have empiric benefit but I do not believe the results of this study can establish their value for resection of PM. The operating surgeon should be congratulated for his excellent results and specifically for the lack of new cranial nerve deficit in a series of technically challenging tumors. Joel D. MacDonald Salt Lake City, Utah The authors present a retrospective series of petrous meningiomas and analysis for predictors of outcome. Specifically, the use of intraoperative monitoring, endoscopy, and ICG videoangiography versus progression free survival, Karnofsky outcome score, extent of resection, and overall survival. As would be expected, the employment of monitoring and adjunct tools as described appeared to improve outcome. Interestingly, the Simpson degree of resection was not significant. Of particular interest is the employment of ICG videoangiography. ICG-videoangiography in skull base surgery may have a prognostic value. Further, it may enhance the technical safety of surgery by distinguishing between a tumor-related and a normal surrounding vessels and evaluate the microvasculature of cranial nerves during tumor resection. Clearly this is an area of future exploration which may provide fruitful results. Carlos A. David Burlington, Massachusetts This is a retrospective review of all patients who underwent microsurgical resection of petrous meningiomas from 1997 to 2016 by the University of Messina group. A multimodal intraoperative protocol, including intraoperative neuromonitoring, endoscopy, and ICG-videoangiography, was implemented in 2007. The 2 time periods were analyzed for differences in extent of resection, Karnofsky performance status, overall survival, and progression-free survival. I think this article is an important contribution. The authors found the use of the multimodal intraoperative protocol predicts extent of resection and good functional outcomes. Although the use of the operating microscope is critical for safely performing posterior fossa surgery, I think most would agree that there is significant value in other available tools. We have used intraoperative neuromonitoring for years and feel it is invaluable. Endoscopic-assisted microsurgery has been a recent addition for us, but I agree it enables one to look around corners and verify extent of resection in many cases before closure. The use of ICG with posterior fossa meningiomas is an interesting concept. As it is usually done at the end of the case, I think it would have prognostic value but would not necessarily prevent the surgeon from doing damage. Regardless, it is a novel application of the technology, and I look forward it's future development. I applaud the authors for the work. Recognizing the need for improvement, their effort has the potential to improve outcomes for those treating this challenging pathology. L. Madison Michael II Memphis, Tennessee Copyright © 2018 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 Neurosurgery Oxford University Press

Petrosal Meningiomas: Factors Affecting Outcome and the Role of Intraoperative Multimodal Assistance to Microsurgery

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Congress of Neurological Surgeons
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Copyright © 2018 by the Congress of Neurological Surgeons
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0148-396X
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1524-4040
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10.1093/neuros/nyy188
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Abstract

Abstract BACKGROUND Petrous meningiomas (PMs) represent a subset of posterior fossa tumors accounting for ∼8% of all intracranial meningiomas. Surgical treatment of PMs is challenging because of their relationships with vital neurovascular structures of the cerebellopontine angle. OBJECTIVE To investigate independent pre- and intraoperative predictors of PM surgery outcome. METHODS We reviewed the surgical and outcome data of patients who underwent microsurgical resection of PMs from 1997 to 2016. From 2007 onward, a multimodal intraoperative protocol consisting of intraoperative neuromonitoring (IONM), endoscopy, and indocyanine green (ICG) videoangiography was applied. Outcome variables included extent of resection, Karnofsky performance status (KPS), overall survival, and progression-free survival (PFS). RESULTS A total of 54 patients were included. Independent predictors of gross total resection (GTR) included retromeatal location (P < .0175; odds ratio [OR] 4.05), absence of brainstem compression (P < .02; OR 3.55), and histological WHO grade I (P < .001; OR 3.47). Nongiant size (P < .012; OR 4.38), and WHO grade I (P < .0001; OR 7.7) were independent predictors of stable or improved KPS. The use of multimodal intraoperative tools to assist surgery independently predicted GTR (P < .002; OR 6.8) and good KPS (P < .018; OR 4.23). Nongiant size (P = .01) and WHO grade I (P = .002) were significantly associated with increased PFS. CONCLUSION Notwithstanding the limitations of a retrospective study, our results suggest that support of microsurgery by a combination of IONM, endoscopy, and ICG videoangiography may improve patient outcome in PM surgery. Petrous bone meningiomas, Intraoperative neurophysiological monitoring, Endoscopic assistance, Indocyanine green videoangiography, Posterior fossa meningioma ABBREVIATIONS ABBREVIATIONS BAEP brainstem auditory evoked potentials CPA cerebellopontine angle EMG electromyography EOR extent of resection GTR gross total resection ICG indocyanine green IONM intraoperative neurophysiological monitoring KPS Karnofsky performance status MEPs motor evoked potentials MR magnetic resonance NPVs negative predictive values OR odds ratio OS overall survival PFS progression-free survival PPVs positive predictive values PMs petrous meningiomas PR partial resection SEPs somatosensory evoked potentials STR subtotal resection Petrous meningiomas (PMs) represent a subset of posterior fossa tumors. They account for approximately 8% of all intracranial meningiomas1 and 50% of all posterior cranial fossa meningiomas2 and are among the most challenging skull base meningiomas because of their relationships with vital neurovascular structures. Objective The aim of this study was to investigate pre- and intraoperative predictors of outcome for patients operated on for PMs beyond clinical variables, the use of multimodal intraoperative strategies for the surgical management of PM, including intraoperative neurophysiological monitoring (IONM), endoscopic assistance, and indocyanine green (ICG) videoangiography, was highlighted. The extent of resection (EOR), Karnofsky performance status (KPS), overall survival (OS), and progression-free survival (PFS) were analyzed. METHODS Study Design and Setting We retrospectively reviewed the clinical, surgical and outcome data of patients with PMs operated on by 1 surgeon (FT) at a single institution (Department of Neurosurgery, University of Messina, Italy) from January 1997 to December 2016. Participants and Data Sources Table 1 summarizes the clinical and demographic characteristics of the patients. All patients underwent microsurgical resection. From 2007 onward, a multimodal intraoperative strategy consisting of IONM, endoscopic assistance, and ICG videoangiography was added to the standard microsurgical technique, which remained fundamentally unchanged. TABLE 1. Clinical and Demographic Characteristics of Patients Variables N° Patients Age (mean ± SD) 56.7 ± 14.2 Sex  M 9 (17%)  F 45 (83%) Type of meningioma  Premeatal 26 (48%)  Retromeatal 28 (52%) Tumor size  Small (<1 cm) 0  Medium (1-2.4 cm) 2 (4%)  Large (2.5-4.4 cm) 24 (44%)  Giant (>4.5 cm) 28 (52%) KPS (mean ± SD) 79 ± 17 Brainstem compression 24 (44%) Other deficits  None 17 (31%)  CN III 2 (4%)  CN IV 2 (4%)  CN V 10 (18%)  CN VI 3 (5%)  CN VII 7 (13%)  CN VIII 12 (22%)  CN IX X XI 7 (13%)  CN XII 0  Cerebellar dysfunctions 13 (24%)  Motor deficits 9 (17%)  Sensory deficit 1 (2%) Variables N° Patients Age (mean ± SD) 56.7 ± 14.2 Sex  M 9 (17%)  F 45 (83%) Type of meningioma  Premeatal 26 (48%)  Retromeatal 28 (52%) Tumor size  Small (<1 cm) 0  Medium (1-2.4 cm) 2 (4%)  Large (2.5-4.4 cm) 24 (44%)  Giant (>4.5 cm) 28 (52%) KPS (mean ± SD) 79 ± 17 Brainstem compression 24 (44%) Other deficits  None 17 (31%)  CN III 2 (4%)  CN IV 2 (4%)  CN V 10 (18%)  CN VI 3 (5%)  CN VII 7 (13%)  CN VIII 12 (22%)  CN IX X XI 7 (13%)  CN XII 0  Cerebellar dysfunctions 13 (24%)  Motor deficits 9 (17%)  Sensory deficit 1 (2%) SD, standard deviation; KPS, Karnofsky performance status; CN, cranial nerve View Large TABLE 1. Clinical and Demographic Characteristics of Patients Variables N° Patients Age (mean ± SD) 56.7 ± 14.2 Sex  M 9 (17%)  F 45 (83%) Type of meningioma  Premeatal 26 (48%)  Retromeatal 28 (52%) Tumor size  Small (<1 cm) 0  Medium (1-2.4 cm) 2 (4%)  Large (2.5-4.4 cm) 24 (44%)  Giant (>4.5 cm) 28 (52%) KPS (mean ± SD) 79 ± 17 Brainstem compression 24 (44%) Other deficits  None 17 (31%)  CN III 2 (4%)  CN IV 2 (4%)  CN V 10 (18%)  CN VI 3 (5%)  CN VII 7 (13%)  CN VIII 12 (22%)  CN IX X XI 7 (13%)  CN XII 0  Cerebellar dysfunctions 13 (24%)  Motor deficits 9 (17%)  Sensory deficit 1 (2%) Variables N° Patients Age (mean ± SD) 56.7 ± 14.2 Sex  M 9 (17%)  F 45 (83%) Type of meningioma  Premeatal 26 (48%)  Retromeatal 28 (52%) Tumor size  Small (<1 cm) 0  Medium (1-2.4 cm) 2 (4%)  Large (2.5-4.4 cm) 24 (44%)  Giant (>4.5 cm) 28 (52%) KPS (mean ± SD) 79 ± 17 Brainstem compression 24 (44%) Other deficits  None 17 (31%)  CN III 2 (4%)  CN IV 2 (4%)  CN V 10 (18%)  CN VI 3 (5%)  CN VII 7 (13%)  CN VIII 12 (22%)  CN IX X XI 7 (13%)  CN XII 0  Cerebellar dysfunctions 13 (24%)  Motor deficits 9 (17%)  Sensory deficit 1 (2%) SD, standard deviation; KPS, Karnofsky performance status; CN, cranial nerve View Large Study Size A total of 54 patients with PMs were included in this study. The eligibility criteria included age of ≥18 yr and a PM with limited to the posterior cranial fossa. Patients who had undergone previous surgical treatment and/or radiotherapy were included in this analysis. Patients harboring meningiomas outside the posterior cranial fossa were excluded from the analysis. All patients signed an informed consent for the scientific use of their data according to the requirements of the local Institutional Review Board. Data Sources Clinical and treatment data were retrospectively collected in a digital archive. Follow-up information was obtained by outpatient clinical evaluation or telephone interviews at defined time intervals. Variables We collected demographic and preoperative clinical data including age, sex, KPS, and neurological examination results. Preoperatively, each patient underwent a contrast-enhanced magnetic resonance (MR) scan, integrated with T2-weighted MR sequences. In most challenging cases, MR scans were integrated with arterial and venous MR angiograms. Tumor size was categorized as small (<1.0 cm), medium (1.0-2.4 cm), large (2.5-4.4 cm), or giant (>4.5 cm).3 Surgical Management PMs were classified as premeatal or retromeatal4,5 according to the relationship between the dural attachment and the internal acoustic meatus. The most commonly employed surgical approach was the retrosigmoid approach. In selected cases, according to the extent of the tumor and its relationship with vessel and nerves, the petrosal approach was adopted.6-10 The surgical strategy aimed to achieve gross total resection (GTR) while preserving neurological function. For this purpose, we considered relationships between the tumor and the brainstem and the preservation of an arachnoidal plane between the tumor and the brainstem. IONM was carried out through evaluation of motor evoked potentials (MEPs) of the corticobulbar and corticospinal tracts, somatosensory evoked potentials (SEPs), brainstem auditory evoked potentials (BAEPs), and both free-running and triggered bipolar electromyography (EMG; Figure 1). Data were recorded using an IONM workstation (NIM Eclipse; Medtronic, Dublin, Ireland). Worldwide recommendations on arrangement and stimulation parameters were adopted.7-10 The protocol used for anesthesiology has been reported elsewhere.11 Warning criteria included the following: (1) SEPs—a more than 50% drop in amplitude during 3 consecutive recordings;9 (2) MEPs—a decrease of 50% in amplitude;9 (3) BAEP—an increase in latency of waves III and IV/V for more than 0.5 ms and an amplitude decrease of more than 50%;9 (4) free-running EMG—the appearance of A-, B-, and C-trains;9 and (5) triggered EMG—the absence of a response.9 FIGURE 1. View largeDownload slide Case example showing a left premeatal meningioma. A, Preoperative axial contrast-enhanced T1 MR scan. B, Intraoperative stimulation of the VII nerve with a bipolar concentric probe at 0.20 mA. C, Postoperative axial contrast-enhanced T1 MR scan exhibiting a GTR. Mas, masseter muscle; Orb, orbicularis oris muscle; Nas, nasalis muscle; Sf, stylopharyngeus muscle; Tps, trapezius muscle. FIGURE 1. View largeDownload slide Case example showing a left premeatal meningioma. A, Preoperative axial contrast-enhanced T1 MR scan. B, Intraoperative stimulation of the VII nerve with a bipolar concentric probe at 0.20 mA. C, Postoperative axial contrast-enhanced T1 MR scan exhibiting a GTR. Mas, masseter muscle; Orb, orbicularis oris muscle; Nas, nasalis muscle; Sf, stylopharyngeus muscle; Tps, trapezius muscle. Endoscopic assistance was performed with a rigid endoscope without a working channel (18 cm length, 4 mm, 0° and 30°; Karl Storz GmbH & Co KG, Tuttlingen, Germany) associated with a high-definition camera.12-14 The endoscope was used free-hand during the tumor removal in order to improve the surgeon's microscopic view, reducing the neurovascular retraction necessary to gain access to blind corners.15 If tumor remnants were identified and their removal was judged safe, they were taken out under endoscopic vision. ICG was used during the surgical procedure and after the meningioma removal (Figure 2). The suggested dose of ICG for videoangiography is 0.2 to 0.5 mg/kg.16,17 The intravascular dye was displayed through an operating microscope (OPMI Pentero; Carl Zeiss Meditec, Jena, Germany) equipped with an additional fluorescent light source (wavelength 700-850 nm).17 ICG was employed to assess the patency of critical vascular structures and the microvascularization of cranial nerves. FIGURE 2. View largeDownload slide Case example showing a left premeatal meningioma. A, Preoperative axial contrast-enhanced T1 MR scan. B, Postoperative axial contrast-enhanced T1 MR scan exhibiting a GTR. C, ICG videoangiography showing the preservation of microvascularization of cranial nerves V and VIII. D, Endoscopic view of cranial nerves V, VI, and VIII at the end of tumor removal. FIGURE 2. View largeDownload slide Case example showing a left premeatal meningioma. A, Preoperative axial contrast-enhanced T1 MR scan. B, Postoperative axial contrast-enhanced T1 MR scan exhibiting a GTR. C, ICG videoangiography showing the preservation of microvascularization of cranial nerves V and VIII. D, Endoscopic view of cranial nerves V, VI, and VIII at the end of tumor removal. Adjuvant Treatment Patients with subtotal resection (STR) and partial resection (PR) and patients with recurrent tumors after GTR were referred for postoperative adjuvant radiosurgery treatment.18-20 Patients underwent single session radiosurgery (median dose 14 Gy; range 13-15 Gy) using a LINAC frame-based system (3D-Line; Medica Systems, Milan, Italy) between 1997 and 2006 and 3 to 5 sessions (median 5) and 21 to 25 (median 25) Gy using a CyberKnife system (Accuray Inc, Sunnyvale, California) from 2007 onward. Assessment of Outcome and Quantitative Variables To avoid inconsistent interpretation, we evaluated clinical results according to numerical scales. The variables that were examined as independent predictors of outcome were as follows: (1) location of the tumor, (2) size of the lesion, (3) occurrence of preoperative neurological deficits, (4) presence of brainstem compression, (5) histological grading, (6) use of multimodal intraoperative tools to support microsurgical resection, (7) previous surgery, and (8) Simpson resection grade. The outcome variables included EOR and KPS analysis at long-term follow-up. OS and PFS were also analyzed. Postoperative magnetic resonance imaging studies were obtained before discharge, 3 to 6 mo postoperatively and yearly thereafter.21 The EOR was evaluated through postoperative contrast-enhanced MR.22 Postoperative radiological and clinical data were collected and stored during the outpatient visits and then reviewed and discussed by a multidisciplinary tumor board, where independent neuroradiologists provided the final evaluation of the EOR and recurrence. EOR was classified as GTR, STR (<10% of tumor remnant) or PR (>10% of tumor remnant). Simpson grade was analyzed as defined from both operative reports and postoperative images. Tumor recurrence was defined as any new, unequivocal enhancement seen in the resection cavity; tumor progression was defined as any unequivocal increase in size of the residual tumor seen on postoperative imaging (for the purpose of comparing tumor control rates, recurrence and progression were treated as similar events21). OS was defined as the time between initial surgery and death, while PFS was expressed as the time between initial surgery and either demonstration of recurrence/progression or death. Long-term follow-up evaluations were conducted by collecting medical records and by performing telephone interviews. When available, the latest MR scans and radiological reports were collected. Statistical Methods For all preoperative, surgical, and outcome variables, percentages of frequency distributions were analyzed. For the statistical analysis, variables were sorted as indicated below. A multivariate analysis was performed by using the multiple logistic regression method. Variables were transformed into binary variables to be used in the logistic regression model.23 The dichotomous variables were preoperative neurological deficit, brainstem compression, use of the multimodal intraoperative protocol, and previous surgery. For nondichotomous variables, cut-off values were chosen according to clinical criteria and published data. The subsets for predictors and outcome variables were as follows: location, premeatal vs retromeatal; tumor size, small to large vs giant; histological grade, grade I vs grades II/III; EOR, GTR vs other EOR; KPS, improved/unchanged vs worsened; Simpson grade, grade I vs other grades. OS and PFS analyses were performed by using the Kaplan–Meier method. The log-rank test was used to compare OS and PFS curves for each pre- and intraoperative variable. The accuracy of the IONM was assessed by using Fisher's exact test and by analyzing the specificity, sensitivity, and positive and negative predictive values (PPVs and NPVs). Contingency tables for size-related groups (small, medium, large, and giant) were analyzed by the chi-squared test. Statistical significance was defined as a P value < .05, and the odds ratio (OR) for each variable was reported. The multivariate analysis was accomplished by using the software STATCALC 8.2.2 (AcaStat, Poinciana, Florida; www.acastat.com). OS, PFS, and IONM analyses were performed in GraphPad Prism version 6.00 for Windows (GraphPad Software, La Jolla, California; www.graphpad.com). RESULTS Participants A total of 54 patients with PMs were included in this study. Table 2 summarizes the results of surgical treatment. TABLE 2. Follow-up Data and Results of Surgery Variables No. patient (percentage) Follow-up range (months) 6-189 Follow-up mean (months) 58 EOR  GTR 35 (70%)  Subtotal resection 13 (26%)  Partial resection 2 (4%) Simpson grade  I 6 (12%)  II 29 (58%)  III 13 (26%)  IV 2 (4%) Surgical approaches  Retrosigmoid 51 (94%)  Combined petrosal 3 (6%) Histology  WHO grade I 50 (93%)  WHO grade II 3 (5%)  WHO grade III 1 (2%) Postoperative complications  CSF leakage 0  Hydrocephalus 3 (6%)  Brainstem or cerebellar Ischemia 3 (6%)  Hemorrhage 0  Infection 0 Perioperative mortality  Brainstem and cerebellar ischemia 2 (4%)  Myocardial infarction 1 (2%)  Inhalation pneumonia 1 (2%) KPS at follow-up  KPS improved 18 (36%)  KPS worsened 16 (32%)  KPS unchanged 16 (32%) Survival at follow-up  Alive 40 (87%)  Long-term mortality for disease 4 (9%)  Long-term mortality for other reasons 2 (4%) Recurrence rate 8 (16%) Variables No. patient (percentage) Follow-up range (months) 6-189 Follow-up mean (months) 58 EOR  GTR 35 (70%)  Subtotal resection 13 (26%)  Partial resection 2 (4%) Simpson grade  I 6 (12%)  II 29 (58%)  III 13 (26%)  IV 2 (4%) Surgical approaches  Retrosigmoid 51 (94%)  Combined petrosal 3 (6%) Histology  WHO grade I 50 (93%)  WHO grade II 3 (5%)  WHO grade III 1 (2%) Postoperative complications  CSF leakage 0  Hydrocephalus 3 (6%)  Brainstem or cerebellar Ischemia 3 (6%)  Hemorrhage 0  Infection 0 Perioperative mortality  Brainstem and cerebellar ischemia 2 (4%)  Myocardial infarction 1 (2%)  Inhalation pneumonia 1 (2%) KPS at follow-up  KPS improved 18 (36%)  KPS worsened 16 (32%)  KPS unchanged 16 (32%) Survival at follow-up  Alive 40 (87%)  Long-term mortality for disease 4 (9%)  Long-term mortality for other reasons 2 (4%) Recurrence rate 8 (16%) EOR, extent of resection; KPS, Karnofsky performance status View Large TABLE 2. Follow-up Data and Results of Surgery Variables No. patient (percentage) Follow-up range (months) 6-189 Follow-up mean (months) 58 EOR  GTR 35 (70%)  Subtotal resection 13 (26%)  Partial resection 2 (4%) Simpson grade  I 6 (12%)  II 29 (58%)  III 13 (26%)  IV 2 (4%) Surgical approaches  Retrosigmoid 51 (94%)  Combined petrosal 3 (6%) Histology  WHO grade I 50 (93%)  WHO grade II 3 (5%)  WHO grade III 1 (2%) Postoperative complications  CSF leakage 0  Hydrocephalus 3 (6%)  Brainstem or cerebellar Ischemia 3 (6%)  Hemorrhage 0  Infection 0 Perioperative mortality  Brainstem and cerebellar ischemia 2 (4%)  Myocardial infarction 1 (2%)  Inhalation pneumonia 1 (2%) KPS at follow-up  KPS improved 18 (36%)  KPS worsened 16 (32%)  KPS unchanged 16 (32%) Survival at follow-up  Alive 40 (87%)  Long-term mortality for disease 4 (9%)  Long-term mortality for other reasons 2 (4%) Recurrence rate 8 (16%) Variables No. patient (percentage) Follow-up range (months) 6-189 Follow-up mean (months) 58 EOR  GTR 35 (70%)  Subtotal resection 13 (26%)  Partial resection 2 (4%) Simpson grade  I 6 (12%)  II 29 (58%)  III 13 (26%)  IV 2 (4%) Surgical approaches  Retrosigmoid 51 (94%)  Combined petrosal 3 (6%) Histology  WHO grade I 50 (93%)  WHO grade II 3 (5%)  WHO grade III 1 (2%) Postoperative complications  CSF leakage 0  Hydrocephalus 3 (6%)  Brainstem or cerebellar Ischemia 3 (6%)  Hemorrhage 0  Infection 0 Perioperative mortality  Brainstem and cerebellar ischemia 2 (4%)  Myocardial infarction 1 (2%)  Inhalation pneumonia 1 (2%) KPS at follow-up  KPS improved 18 (36%)  KPS worsened 16 (32%)  KPS unchanged 16 (32%) Survival at follow-up  Alive 40 (87%)  Long-term mortality for disease 4 (9%)  Long-term mortality for other reasons 2 (4%) Recurrence rate 8 (16%) EOR, extent of resection; KPS, Karnofsky performance status View Large Descriptive Data Twenty-six patients (48%) harbored premeatal meningiomas, while 28 (52%) had retromeatal meningiomas. Two patients had been previously treated by surgery only, and 1 by surgery followed by radiotherapy. Three patients were affected by multiple meningiomas. Fifty-two percent of patients had giant meningiomas. The retrosigmoid approach alone was used in 94% of cases, while a combined pre- and retrosigmoid approach was adopted in 3 patients (6%). Ninety-three percent of patients had a WHO grade I meningioma, 5% WHO grade II, and 2% WHO grade III. The follow-up period ranged from 6 to 189 mo, with a mean of 58 mo. Four patients were lost to follow-up and, therefore, were excluded from the long-term outcome and multivariate analysis. Main Results A surgical complication requiring a second surgery occurred in 6 patients (11%). The overall morbidity rate was 18%, consisting of a new or worsened cranial nerve deficit in 11% of cases and a new or worsened motor deficit in the remaining cases. Perioperative mortality (within 30 d after the surgical procedure) was 8% (Table 2) and exclusively involved patients who harbored premeatal meningiomas presenting a preoperative KPS score <60 together with cranial nerve deficits and limb motor deficits. The causes of mortality were brainstem and cerebellar ischemia in 2 cases, inhalation pneumonia in 1 case, and myocardial infarction in 1 case. The overall EOR analysis revealed a GTR in 70% of patients, an STR in 26%, and a PR in 4%. The KPS analysis at the follow-up evaluation revealed that 36% of patients were improved, 32% were unchanged, and 32% were worsened. At the follow-up examination, 87% of patients were alive, 9% were deceased from disease recurrence or progression, and 4% had died of other causes. Thirty-nine percent of patients (21/54) with subtotal or partial resection or with tumor recurrence (16%) had undergone single or multisession radiosurgery at the time of analysis. The multimodal intraoperative protocol was adopted for 22 patients (from 2007 onward). Factors Affecting Outcome When a multivariate analysis was performed, a retromeatal location (P = .0175; OR 4.05), the absence of brainstem compression (P = .02; OR 3.55), a WHO grade of I (P = .001; OR 3.47), and the use of a multimodal intraoperative strategy (P < .002; OR 6.8) were found to be independent predictors of GTR achievement (Table 3). A detailed examination of results by meningioma size category (Table 4) showed that the probability of a poor KPS, but not perioperative mortality, was highest for patients with giant meningiomas (P = .04). TABLE 3. Results of Multivariate, OS, and PFS Analyses Location Size Preoperative deficits Brainstem compression WHO grade Multimodal intraoperative protocol EOR P = .0175 (OR 4.05) – – P = .02 (OR 3.55) P < .001 (OR 3.47) P = .002 (OR 6.8) KPS – P = .012 (OR 4.38) – – P < .0001 (OR 7.7) P = .018 (OR 4.23) Perioperative mortality – – – – – – PFS – P = .01 – – P = .002 – Location Size Preoperative deficits Brainstem compression WHO grade Multimodal intraoperative protocol EOR P = .0175 (OR 4.05) – – P = .02 (OR 3.55) P < .001 (OR 3.47) P = .002 (OR 6.8) KPS – P = .012 (OR 4.38) – – P < .0001 (OR 7.7) P = .018 (OR 4.23) Perioperative mortality – – – – – – PFS – P = .01 – – P = .002 – EOR, extent of resection; GTR, gross total resection; KPS, Karnofsky performance status; PFS, progression-free survival; OR, odds ratio; NS, not significant; WHO, World Health Organization View Large TABLE 3. Results of Multivariate, OS, and PFS Analyses Location Size Preoperative deficits Brainstem compression WHO grade Multimodal intraoperative protocol EOR P = .0175 (OR 4.05) – – P = .02 (OR 3.55) P < .001 (OR 3.47) P = .002 (OR 6.8) KPS – P = .012 (OR 4.38) – – P < .0001 (OR 7.7) P = .018 (OR 4.23) Perioperative mortality – – – – – – PFS – P = .01 – – P = .002 – Location Size Preoperative deficits Brainstem compression WHO grade Multimodal intraoperative protocol EOR P = .0175 (OR 4.05) – – P = .02 (OR 3.55) P < .001 (OR 3.47) P = .002 (OR 6.8) KPS – P = .012 (OR 4.38) – – P < .0001 (OR 7.7) P = .018 (OR 4.23) Perioperative mortality – – – – – – PFS – P = .01 – – P = .002 – EOR, extent of resection; GTR, gross total resection; KPS, Karnofsky performance status; PFS, progression-free survival; OR, odds ratio; NS, not significant; WHO, World Health Organization View Large TABLE 4. Preoperative Characteristics and Postoperative Results According to Tumor Size Variables Small (<1.0 cm) Medium (1-2.4 cm) Large (2.5-4.4 cm) Giant (>4.5 cm) P value Type of meningioma –  Premeatal 0 0 10 (42%) 16 (57%)  Retromeatal 0 2 (100%) 14 (58%) 12 (43%) Neurological deficits –  None 0 2 (100%) 9 (37%) 6 (21%)  III CN 0 0 1 (4%) 1 (3%)  IV CN 0 0 0 2 (7%)  V CN 0 0 6 (25%) 4 (14%)  VI CN 0 0 0 3 (11%)  VII CN 0 0 2 (8%) 5 (18%)  VIII CN 0 0 5 (21%) 7 (25%)  IX-X-XI CN 0 0 2 (8%) 5 (18%)  XII CN 0 0 0 0  Cerebellar dysfunctions 0 0 5 (21%) 8 (28%)  Motor deficits 0 0 3 (12%) 6 (21%)  Sensory deficit 0 0 1 (4%) 0 EOR –  GTR 0 2 (100%) 18 (78%) 15 (60%)  Subtotal resection 0 0 5 (22%) 8 (32%)  Partial resection 0 0 0 2 (8%) Simpson grade –  I 0 0 3 (13%) 3 (12%)  II 0 2 (100%) 15 (65%) 12 (48%)  III 0 0 5 (22%) 8 (32%)  IV 0 0 0 2 (8%) Histology –  WHO grade I 0 2 (100%) 23 (96%) 25 (89%)  WHO grade II 0 0 1 (4%) 2 (7%)  WHO grade III 0 0 0 1 (4%) Postoperative complications –  CSF leakage 0 0 0 0  Hydrocephalus 0 0 1 (4%) 2 (8%)  Brainstem or cerebellar Ischemia 0 0 1 (4%) 2 (8%)  Hemorrhage 0 0 0 0  Infection 0 0 0 0 Perioperative mortality –  Brainstem and cerebellar ischemia 0 0 1 (4%) 1 (3%)  Myocardial infarction 0 0 0 1 (3%)  Inhalation pneumonia 0 0 0 1 (3%) KPS at follow-up P = .04  KPS improved 0 0 10 (44%) 8 (32%)  KPS worsened 0 0 4 (17%) 12 (48%)  KPS unchanged 0 2 (100%) 9 (39%) 5 (20%) Survival at follow-up –  Alive 0 2 (100%) 19 (86%) 19 (86%)  Long-term mortality for disease 0 0 2 (9%) 2 (9%)  Long-term mortality for other reasons 0 0 1 (5%) 1 (5%) Recurrence rate 0 0 1 (4%) 7 (28%) – Variables Small (<1.0 cm) Medium (1-2.4 cm) Large (2.5-4.4 cm) Giant (>4.5 cm) P value Type of meningioma –  Premeatal 0 0 10 (42%) 16 (57%)  Retromeatal 0 2 (100%) 14 (58%) 12 (43%) Neurological deficits –  None 0 2 (100%) 9 (37%) 6 (21%)  III CN 0 0 1 (4%) 1 (3%)  IV CN 0 0 0 2 (7%)  V CN 0 0 6 (25%) 4 (14%)  VI CN 0 0 0 3 (11%)  VII CN 0 0 2 (8%) 5 (18%)  VIII CN 0 0 5 (21%) 7 (25%)  IX-X-XI CN 0 0 2 (8%) 5 (18%)  XII CN 0 0 0 0  Cerebellar dysfunctions 0 0 5 (21%) 8 (28%)  Motor deficits 0 0 3 (12%) 6 (21%)  Sensory deficit 0 0 1 (4%) 0 EOR –  GTR 0 2 (100%) 18 (78%) 15 (60%)  Subtotal resection 0 0 5 (22%) 8 (32%)  Partial resection 0 0 0 2 (8%) Simpson grade –  I 0 0 3 (13%) 3 (12%)  II 0 2 (100%) 15 (65%) 12 (48%)  III 0 0 5 (22%) 8 (32%)  IV 0 0 0 2 (8%) Histology –  WHO grade I 0 2 (100%) 23 (96%) 25 (89%)  WHO grade II 0 0 1 (4%) 2 (7%)  WHO grade III 0 0 0 1 (4%) Postoperative complications –  CSF leakage 0 0 0 0  Hydrocephalus 0 0 1 (4%) 2 (8%)  Brainstem or cerebellar Ischemia 0 0 1 (4%) 2 (8%)  Hemorrhage 0 0 0 0  Infection 0 0 0 0 Perioperative mortality –  Brainstem and cerebellar ischemia 0 0 1 (4%) 1 (3%)  Myocardial infarction 0 0 0 1 (3%)  Inhalation pneumonia 0 0 0 1 (3%) KPS at follow-up P = .04  KPS improved 0 0 10 (44%) 8 (32%)  KPS worsened 0 0 4 (17%) 12 (48%)  KPS unchanged 0 2 (100%) 9 (39%) 5 (20%) Survival at follow-up –  Alive 0 2 (100%) 19 (86%) 19 (86%)  Long-term mortality for disease 0 0 2 (9%) 2 (9%)  Long-term mortality for other reasons 0 0 1 (5%) 1 (5%) Recurrence rate 0 0 1 (4%) 7 (28%) – View Large TABLE 4. Preoperative Characteristics and Postoperative Results According to Tumor Size Variables Small (<1.0 cm) Medium (1-2.4 cm) Large (2.5-4.4 cm) Giant (>4.5 cm) P value Type of meningioma –  Premeatal 0 0 10 (42%) 16 (57%)  Retromeatal 0 2 (100%) 14 (58%) 12 (43%) Neurological deficits –  None 0 2 (100%) 9 (37%) 6 (21%)  III CN 0 0 1 (4%) 1 (3%)  IV CN 0 0 0 2 (7%)  V CN 0 0 6 (25%) 4 (14%)  VI CN 0 0 0 3 (11%)  VII CN 0 0 2 (8%) 5 (18%)  VIII CN 0 0 5 (21%) 7 (25%)  IX-X-XI CN 0 0 2 (8%) 5 (18%)  XII CN 0 0 0 0  Cerebellar dysfunctions 0 0 5 (21%) 8 (28%)  Motor deficits 0 0 3 (12%) 6 (21%)  Sensory deficit 0 0 1 (4%) 0 EOR –  GTR 0 2 (100%) 18 (78%) 15 (60%)  Subtotal resection 0 0 5 (22%) 8 (32%)  Partial resection 0 0 0 2 (8%) Simpson grade –  I 0 0 3 (13%) 3 (12%)  II 0 2 (100%) 15 (65%) 12 (48%)  III 0 0 5 (22%) 8 (32%)  IV 0 0 0 2 (8%) Histology –  WHO grade I 0 2 (100%) 23 (96%) 25 (89%)  WHO grade II 0 0 1 (4%) 2 (7%)  WHO grade III 0 0 0 1 (4%) Postoperative complications –  CSF leakage 0 0 0 0  Hydrocephalus 0 0 1 (4%) 2 (8%)  Brainstem or cerebellar Ischemia 0 0 1 (4%) 2 (8%)  Hemorrhage 0 0 0 0  Infection 0 0 0 0 Perioperative mortality –  Brainstem and cerebellar ischemia 0 0 1 (4%) 1 (3%)  Myocardial infarction 0 0 0 1 (3%)  Inhalation pneumonia 0 0 0 1 (3%) KPS at follow-up P = .04  KPS improved 0 0 10 (44%) 8 (32%)  KPS worsened 0 0 4 (17%) 12 (48%)  KPS unchanged 0 2 (100%) 9 (39%) 5 (20%) Survival at follow-up –  Alive 0 2 (100%) 19 (86%) 19 (86%)  Long-term mortality for disease 0 0 2 (9%) 2 (9%)  Long-term mortality for other reasons 0 0 1 (5%) 1 (5%) Recurrence rate 0 0 1 (4%) 7 (28%) – Variables Small (<1.0 cm) Medium (1-2.4 cm) Large (2.5-4.4 cm) Giant (>4.5 cm) P value Type of meningioma –  Premeatal 0 0 10 (42%) 16 (57%)  Retromeatal 0 2 (100%) 14 (58%) 12 (43%) Neurological deficits –  None 0 2 (100%) 9 (37%) 6 (21%)  III CN 0 0 1 (4%) 1 (3%)  IV CN 0 0 0 2 (7%)  V CN 0 0 6 (25%) 4 (14%)  VI CN 0 0 0 3 (11%)  VII CN 0 0 2 (8%) 5 (18%)  VIII CN 0 0 5 (21%) 7 (25%)  IX-X-XI CN 0 0 2 (8%) 5 (18%)  XII CN 0 0 0 0  Cerebellar dysfunctions 0 0 5 (21%) 8 (28%)  Motor deficits 0 0 3 (12%) 6 (21%)  Sensory deficit 0 0 1 (4%) 0 EOR –  GTR 0 2 (100%) 18 (78%) 15 (60%)  Subtotal resection 0 0 5 (22%) 8 (32%)  Partial resection 0 0 0 2 (8%) Simpson grade –  I 0 0 3 (13%) 3 (12%)  II 0 2 (100%) 15 (65%) 12 (48%)  III 0 0 5 (22%) 8 (32%)  IV 0 0 0 2 (8%) Histology –  WHO grade I 0 2 (100%) 23 (96%) 25 (89%)  WHO grade II 0 0 1 (4%) 2 (7%)  WHO grade III 0 0 0 1 (4%) Postoperative complications –  CSF leakage 0 0 0 0  Hydrocephalus 0 0 1 (4%) 2 (8%)  Brainstem or cerebellar Ischemia 0 0 1 (4%) 2 (8%)  Hemorrhage 0 0 0 0  Infection 0 0 0 0 Perioperative mortality –  Brainstem and cerebellar ischemia 0 0 1 (4%) 1 (3%)  Myocardial infarction 0 0 0 1 (3%)  Inhalation pneumonia 0 0 0 1 (3%) KPS at follow-up P = .04  KPS improved 0 0 10 (44%) 8 (32%)  KPS worsened 0 0 4 (17%) 12 (48%)  KPS unchanged 0 2 (100%) 9 (39%) 5 (20%) Survival at follow-up –  Alive 0 2 (100%) 19 (86%) 19 (86%)  Long-term mortality for disease 0 0 2 (9%) 2 (9%)  Long-term mortality for other reasons 0 0 1 (5%) 1 (5%) Recurrence rate 0 0 1 (4%) 7 (28%) – View Large At follow-up, 36% of patients had an improved neurological status, 32% were unchanged, and 32% had worsened. The multivariate analysis showed that nongiant tumor size (P = .012; OR 4.38), a WHO grade of I (P < .0001; OR 7.7), and the use of the multimodal intraoperative protocol (P = .018; OR 4.23) were independent predictors of good KPS (Table 3). Finally, nongiant meningioma size (P = .01) and a WHO grade of I (P = .002) were significantly associated with increased PFS (Table 3; Figures 3 and 4). FIGURE 3. View largeDownload slide Kaplan–Meier progression-free survival (PFS) analysis of subgroups of patients defined by tumor size (small to large vs giant) showed a significant difference (P = .01). FIGURE 3. View largeDownload slide Kaplan–Meier progression-free survival (PFS) analysis of subgroups of patients defined by tumor size (small to large vs giant) showed a significant difference (P = .01). DISCUSSION Key Results In this retrospective single-center study, we reported the surgical results obtained from patients affected by PMs and operated on by the same surgeon over the past 2 decades. Our analysis showed that a retromeatal location, absence of brainstem compression, and a histological WHO grade of I predicted GTR, whereas giant size affected the postoperative KPS and produced a tendency toward elevated postoperative mortality. Notably, the adoption of multimodal intraoperative tools to assist surgery independently allowed the achievement of GTR and a good postoperative KPS. Interpretation The main goal of the study was the identification of factors predicting the EOR and the functional outcome. As expected, the site of meningioma attachment was a significant predictor of outcome. Indeed, meningiomas located ventral to the internal acoustic meatus dislocate posteriorly the neural and vascular structures of the cerebellopontine angle (CPA).24 This setting complicates surgical removal because the resection must be performed in the midst of vital neurovascular structures and along a narrower surgical corridor.5 In particular, the acoustic-facial bundle is at risk of surgical injury. Nakamura et al25 described an improved facial nerve outcome in “CPA meningiomas” when the site of tumor origin was superior or posterior to the IAC. Nevertheless, as the facial nerve is more resilient to surgical trauma, new-onset facial nerve deficits are less common than those involving the cochlear nerve.26 Deficits involving the sixth, ninth, and tenth cranial nerves have occasionally been reported in premeatal meningiomas. Brainstem lesions are also possible with large premeatal tumors, particularly with in lesions receiving a vascular supply from pial vessels. Furthermore, because of the difficulties encountered in safely removing ventral PMs, the rate of GTR is lower for this group of tumors than for retromeatal tumors.26 In the present series, smaller tumors not compressing the brainstem led to a GTR in 92% of cases. Moreover, a WHO grade I was associated with an elevated probability of GTR and improved postoperative performance status as a result of a preserved arachnoid layer protecting the brainstem and neurovascular structures of the CPA. These patients also had better PFS than those affected by giant tumors (P = .01) or WHO grade II or III tumors (P = .002). In Table 5, the overall results of our series are compared with those published in similar studies.1,2,5,25-33 TABLE 5. Literature Review About Petrous Bone Meningiomas Published Series Author and year N° patients Classifications Surgical approaches (%) GTR (%) Follow-up range (mo) Mean follow-up (mo) Recurrence rate Morbidity (%) Perioperative mortality (%) Schaller et al, 19995 31 Premeatal, retromeatal Retrosigmoid (100%) NA 12-168 84 3% 23% 0% Selesnick et al, 200133 12 NA Retrosigmoid (100%) GTR 50% 6-42 NA 8% 33% NA Liu et al, 200329 21 Posterior PM (posterior to the IAC) Retrosigmoid (80%) translabyrinthine (10%) petrosal (10%) GTR 86% NA NA NA 38% 0% Bassiouni et al, 200428 51 Postmeatal, premeatal, suprameatal inframeatal centered on the porus acusticus Retrosigmoid (100%) GTR 84% 13-156 70 4% NA 0% Nakamura et al, 200525 334 Anterior to the IAC, involvement of the IAC, superior to the IAC, inferior to the IAC Retrosigmoid (95%) combined supratentorial-infratentorial presigmoid (5%) GTR 86% 2-214 62 NA 15% 0.6% Wu et al, 200534 82 Type I: laterally to IAC; type II: medially to IAC; type III: attached to the posterior surface of the petrous bone Retrosigmoid (78%) subtemporal transtentorial (10%) presigmoid (12%) GTR 83% 6-96 4.5 NA 16% 0% Deveze et al, 20071 43 Type A: anterior to the IAC; type M: meatal; type P: posterior to the IAC Widened retrolabyrinthine (47%) translabyrinthine (44%) Transotic (2%) transcochlear (7%) GTR 79% 3-120 34 5% 37% 0% Sanna et al, 200731 81 Posterior petrous face Enlarged translabyrinthine (38%) enlarged translabyrinthine with transapical extension (36%) combined retrosigmoid-retrolabyrinthine (10%) modified transcochlear (7%) retrolabyrinthine subtemporal transapical (2%) transpetrous middle cranial fossa (2%) middle cranial fossa approach (5%) GTR 93% NA NA NA 10% 0% Sade and Lee, 200930 58 Posterior, superior and ventral to the IAC Retrosigmoid (100%) GTR 84% NA NA NA 17% NA Peyre et al, 201027 53 Posterior petrous, meatus and IAC, petroux apex w/o invasion of the IAC, CPA with invasion of the IAC Translabyrinthine (21%) enlarged translabyrinthine (21%) translabyrinthine and retrosigmoid (4%) transcochlear (11%) retrosigmoid (17%) retrosigmoid and retrolabyrinthine (13%) RS/RLII and subtemporal (2%) subtemporal with apical petrectomy (11%) GTR 72% NA 35 NA§ 25% NA§ Roche et al, 20112 57 Type A: around the porus trigeminus; type M: at the level of the porus of the IAC; type P: lateral to the IAC Anterior petrosectomy (49%) combined petrosectomy (10%) translabyrinthine (7%) retrolabyrinthine (5%) retrosigmoid (29%) GTR 39% NA§ NA§ 6% 6% 9% Nowak et al, 201330 48 Premeatal, inframeatal, retromeatal Retrosigmoid (79%) subtemporal and suboccipital (15%) combined translabyrinthine (2%) far lateral transcondylar (4%) GTR 94% 12-120 NA 4% 23% 4% Present study 54 Premeatal, retromeatal Retrosigmoid (94%) combined transpetrosal (6%) GTR 70% 6-189 58 16% 18% 8% Author and year N° patients Classifications Surgical approaches (%) GTR (%) Follow-up range (mo) Mean follow-up (mo) Recurrence rate Morbidity (%) Perioperative mortality (%) Schaller et al, 19995 31 Premeatal, retromeatal Retrosigmoid (100%) NA 12-168 84 3% 23% 0% Selesnick et al, 200133 12 NA Retrosigmoid (100%) GTR 50% 6-42 NA 8% 33% NA Liu et al, 200329 21 Posterior PM (posterior to the IAC) Retrosigmoid (80%) translabyrinthine (10%) petrosal (10%) GTR 86% NA NA NA 38% 0% Bassiouni et al, 200428 51 Postmeatal, premeatal, suprameatal inframeatal centered on the porus acusticus Retrosigmoid (100%) GTR 84% 13-156 70 4% NA 0% Nakamura et al, 200525 334 Anterior to the IAC, involvement of the IAC, superior to the IAC, inferior to the IAC Retrosigmoid (95%) combined supratentorial-infratentorial presigmoid (5%) GTR 86% 2-214 62 NA 15% 0.6% Wu et al, 200534 82 Type I: laterally to IAC; type II: medially to IAC; type III: attached to the posterior surface of the petrous bone Retrosigmoid (78%) subtemporal transtentorial (10%) presigmoid (12%) GTR 83% 6-96 4.5 NA 16% 0% Deveze et al, 20071 43 Type A: anterior to the IAC; type M: meatal; type P: posterior to the IAC Widened retrolabyrinthine (47%) translabyrinthine (44%) Transotic (2%) transcochlear (7%) GTR 79% 3-120 34 5% 37% 0% Sanna et al, 200731 81 Posterior petrous face Enlarged translabyrinthine (38%) enlarged translabyrinthine with transapical extension (36%) combined retrosigmoid-retrolabyrinthine (10%) modified transcochlear (7%) retrolabyrinthine subtemporal transapical (2%) transpetrous middle cranial fossa (2%) middle cranial fossa approach (5%) GTR 93% NA NA NA 10% 0% Sade and Lee, 200930 58 Posterior, superior and ventral to the IAC Retrosigmoid (100%) GTR 84% NA NA NA 17% NA Peyre et al, 201027 53 Posterior petrous, meatus and IAC, petroux apex w/o invasion of the IAC, CPA with invasion of the IAC Translabyrinthine (21%) enlarged translabyrinthine (21%) translabyrinthine and retrosigmoid (4%) transcochlear (11%) retrosigmoid (17%) retrosigmoid and retrolabyrinthine (13%) RS/RLII and subtemporal (2%) subtemporal with apical petrectomy (11%) GTR 72% NA 35 NA§ 25% NA§ Roche et al, 20112 57 Type A: around the porus trigeminus; type M: at the level of the porus of the IAC; type P: lateral to the IAC Anterior petrosectomy (49%) combined petrosectomy (10%) translabyrinthine (7%) retrolabyrinthine (5%) retrosigmoid (29%) GTR 39% NA§ NA§ 6% 6% 9% Nowak et al, 201330 48 Premeatal, inframeatal, retromeatal Retrosigmoid (79%) subtemporal and suboccipital (15%) combined translabyrinthine (2%) far lateral transcondylar (4%) GTR 94% 12-120 NA 4% 23% 4% Present study 54 Premeatal, retromeatal Retrosigmoid (94%) combined transpetrosal (6%) GTR 70% 6-189 58 16% 18% 8% GTR, gross total resection; IAC, internal acoustic canal; NA, not available; RS/RL, retrosigmoid/retrolabyrinthine View Large TABLE 5. Literature Review About Petrous Bone Meningiomas Published Series Author and year N° patients Classifications Surgical approaches (%) GTR (%) Follow-up range (mo) Mean follow-up (mo) Recurrence rate Morbidity (%) Perioperative mortality (%) Schaller et al, 19995 31 Premeatal, retromeatal Retrosigmoid (100%) NA 12-168 84 3% 23% 0% Selesnick et al, 200133 12 NA Retrosigmoid (100%) GTR 50% 6-42 NA 8% 33% NA Liu et al, 200329 21 Posterior PM (posterior to the IAC) Retrosigmoid (80%) translabyrinthine (10%) petrosal (10%) GTR 86% NA NA NA 38% 0% Bassiouni et al, 200428 51 Postmeatal, premeatal, suprameatal inframeatal centered on the porus acusticus Retrosigmoid (100%) GTR 84% 13-156 70 4% NA 0% Nakamura et al, 200525 334 Anterior to the IAC, involvement of the IAC, superior to the IAC, inferior to the IAC Retrosigmoid (95%) combined supratentorial-infratentorial presigmoid (5%) GTR 86% 2-214 62 NA 15% 0.6% Wu et al, 200534 82 Type I: laterally to IAC; type II: medially to IAC; type III: attached to the posterior surface of the petrous bone Retrosigmoid (78%) subtemporal transtentorial (10%) presigmoid (12%) GTR 83% 6-96 4.5 NA 16% 0% Deveze et al, 20071 43 Type A: anterior to the IAC; type M: meatal; type P: posterior to the IAC Widened retrolabyrinthine (47%) translabyrinthine (44%) Transotic (2%) transcochlear (7%) GTR 79% 3-120 34 5% 37% 0% Sanna et al, 200731 81 Posterior petrous face Enlarged translabyrinthine (38%) enlarged translabyrinthine with transapical extension (36%) combined retrosigmoid-retrolabyrinthine (10%) modified transcochlear (7%) retrolabyrinthine subtemporal transapical (2%) transpetrous middle cranial fossa (2%) middle cranial fossa approach (5%) GTR 93% NA NA NA 10% 0% Sade and Lee, 200930 58 Posterior, superior and ventral to the IAC Retrosigmoid (100%) GTR 84% NA NA NA 17% NA Peyre et al, 201027 53 Posterior petrous, meatus and IAC, petroux apex w/o invasion of the IAC, CPA with invasion of the IAC Translabyrinthine (21%) enlarged translabyrinthine (21%) translabyrinthine and retrosigmoid (4%) transcochlear (11%) retrosigmoid (17%) retrosigmoid and retrolabyrinthine (13%) RS/RLII and subtemporal (2%) subtemporal with apical petrectomy (11%) GTR 72% NA 35 NA§ 25% NA§ Roche et al, 20112 57 Type A: around the porus trigeminus; type M: at the level of the porus of the IAC; type P: lateral to the IAC Anterior petrosectomy (49%) combined petrosectomy (10%) translabyrinthine (7%) retrolabyrinthine (5%) retrosigmoid (29%) GTR 39% NA§ NA§ 6% 6% 9% Nowak et al, 201330 48 Premeatal, inframeatal, retromeatal Retrosigmoid (79%) subtemporal and suboccipital (15%) combined translabyrinthine (2%) far lateral transcondylar (4%) GTR 94% 12-120 NA 4% 23% 4% Present study 54 Premeatal, retromeatal Retrosigmoid (94%) combined transpetrosal (6%) GTR 70% 6-189 58 16% 18% 8% Author and year N° patients Classifications Surgical approaches (%) GTR (%) Follow-up range (mo) Mean follow-up (mo) Recurrence rate Morbidity (%) Perioperative mortality (%) Schaller et al, 19995 31 Premeatal, retromeatal Retrosigmoid (100%) NA 12-168 84 3% 23% 0% Selesnick et al, 200133 12 NA Retrosigmoid (100%) GTR 50% 6-42 NA 8% 33% NA Liu et al, 200329 21 Posterior PM (posterior to the IAC) Retrosigmoid (80%) translabyrinthine (10%) petrosal (10%) GTR 86% NA NA NA 38% 0% Bassiouni et al, 200428 51 Postmeatal, premeatal, suprameatal inframeatal centered on the porus acusticus Retrosigmoid (100%) GTR 84% 13-156 70 4% NA 0% Nakamura et al, 200525 334 Anterior to the IAC, involvement of the IAC, superior to the IAC, inferior to the IAC Retrosigmoid (95%) combined supratentorial-infratentorial presigmoid (5%) GTR 86% 2-214 62 NA 15% 0.6% Wu et al, 200534 82 Type I: laterally to IAC; type II: medially to IAC; type III: attached to the posterior surface of the petrous bone Retrosigmoid (78%) subtemporal transtentorial (10%) presigmoid (12%) GTR 83% 6-96 4.5 NA 16% 0% Deveze et al, 20071 43 Type A: anterior to the IAC; type M: meatal; type P: posterior to the IAC Widened retrolabyrinthine (47%) translabyrinthine (44%) Transotic (2%) transcochlear (7%) GTR 79% 3-120 34 5% 37% 0% Sanna et al, 200731 81 Posterior petrous face Enlarged translabyrinthine (38%) enlarged translabyrinthine with transapical extension (36%) combined retrosigmoid-retrolabyrinthine (10%) modified transcochlear (7%) retrolabyrinthine subtemporal transapical (2%) transpetrous middle cranial fossa (2%) middle cranial fossa approach (5%) GTR 93% NA NA NA 10% 0% Sade and Lee, 200930 58 Posterior, superior and ventral to the IAC Retrosigmoid (100%) GTR 84% NA NA NA 17% NA Peyre et al, 201027 53 Posterior petrous, meatus and IAC, petroux apex w/o invasion of the IAC, CPA with invasion of the IAC Translabyrinthine (21%) enlarged translabyrinthine (21%) translabyrinthine and retrosigmoid (4%) transcochlear (11%) retrosigmoid (17%) retrosigmoid and retrolabyrinthine (13%) RS/RLII and subtemporal (2%) subtemporal with apical petrectomy (11%) GTR 72% NA 35 NA§ 25% NA§ Roche et al, 20112 57 Type A: around the porus trigeminus; type M: at the level of the porus of the IAC; type P: lateral to the IAC Anterior petrosectomy (49%) combined petrosectomy (10%) translabyrinthine (7%) retrolabyrinthine (5%) retrosigmoid (29%) GTR 39% NA§ NA§ 6% 6% 9% Nowak et al, 201330 48 Premeatal, inframeatal, retromeatal Retrosigmoid (79%) subtemporal and suboccipital (15%) combined translabyrinthine (2%) far lateral transcondylar (4%) GTR 94% 12-120 NA 4% 23% 4% Present study 54 Premeatal, retromeatal Retrosigmoid (94%) combined transpetrosal (6%) GTR 70% 6-189 58 16% 18% 8% GTR, gross total resection; IAC, internal acoustic canal; NA, not available; RS/RL, retrosigmoid/retrolabyrinthine View Large In a subgroup of PM patients, we used multimodal intraoperative assistance with standard treatment paradigms. This resulted in an elevated GTR rate and an improved long-term functional outcome. This is, to the best of our knowledge, the first study that highlights the effects of such an integrated and multimodal operative setup on the surgical and clinical long-term outcome of patients after surgical PM resection. Nonetheless, previous studies have analyzed these techniques individually to establish their value in posterior cranial fossa surgery. Different IONM techniques have been used in posterior cranial fossa surgery. The largest clinical series was published in 2016 by Slotty et al.9 They presented results from 305 patients treated for infratentorial lesions with intraoperative cranial nerve, SEP, and MEP monitoring. They observed that the incidence of IONM alerts during posterior cranial fossa surgery varied according to lesion site and histopathology. In PM resection, most of the alterations concerned BAEPs and free-running and triggered EMG, while no alerts were recorded from SEP or MEP. Notably, the investigators observed that new neurological deficits without IONM alteration were recorded in 11.6% of cases. In our series, using the same technique (n = 22), we found a significant correlation between the use of IONM and preservation of cranial nerves and overall neurological function (Table 3). Furthermore, no patient presented any new postoperative deficit whose occurrence remained undetected by IONM. Accordingly, IONM had a sensitivity of 100%, a specificity of 94%, a PPV of 75%, and an NPV of 100%. There are few studies specifically addressing the issue of endoscopic assistance during skull base meningioma surgery.15,34,35 In 2011, Schroeder et al15 evaluated endoscopic assistance during the microsurgical resection of 46 skull base meningiomas. Among these, 23 involved the petrous bone. They found endoscopic assistance to be particularly helpful for locations such as petroclival region and in meningiomas extending deeply into the internal acoustic meatus. They concluded that endoscopic assistance was useful especially when GTR was planned before surgery, providing additional exposure of the operative field. In our series, we found that endoscopic assistance was useful during the tumor removal, reducing the neurovascular retraction necessary to access the blind corners and thus bringing about a higher rate of GTR. Regarding ICG videoangiography, data for the posterior cranial fossa and particularly for PMs are sporadic. The ICG videoangiography study of the microvascularization of neural structures provides useful prognostic information on the postoperative performance of cranial nerves. It is less clear whether this information can positively influence the surgical strategy. Two studies on the use of ICG videoangiography in brain tumor surgery36,37 describe the possibility of distinguishing between tumor-related and normal passing vessels and verifying the patency of blood vessels around a tumor such as the perforating arteries of the vertebral artery during its mobilization. The potential benefit in identifying adjacent venous sinuses and pial blood supply to the tumors before opening the dura mater has been reported as well.17 Additionally, ICG videoangiography can support the identification of the superior petrosal vein before dural incision to preserve its blood flow during the petrosal approach.38 FIGURE 4. View largeDownload slide Kaplan–Meier progression-free survival (PFS) analysis of subgroups of patients defined by WHO grade (I vs II-III) showed a significant difference (P = .002). FIGURE 4. View largeDownload slide Kaplan–Meier progression-free survival (PFS) analysis of subgroups of patients defined by WHO grade (I vs II-III) showed a significant difference (P = .002). Above all, we believe that ICG videoangiography evaluation of the microvasculature of cranial nerves and the integrity of such vessels may support tumor resection. Indeed, the combination of IONM and ICG videoangiography provides a unique form of intraoperative feedback on the functional status of neural structures and offers insights during the manipulation of such structures. This may eventually affect the neurological outcome, although such an effect still needs to be demonstrated in dedicated studies. Limitations The retrospective and single-center nature of this study carries the unavoidable selection and expertise biases typically associated with such study designs. Nevertheless, we tried to reduce biases related to the surgical learning curve by restricting the study interval to the past 2 decades and to surgery performed by a single author (FT). In this time frame, microsurgical techniques and surgeon experience were developed, but we recognize that a time frame spanning 2 decades and a relatively limited number of patients may reduce the generalizability of our findings. CONLUSION Petrosal meningiomas are challenging tumors to treat because of their relationship to critical neurovascular structures. Important technical advances to support microsurgery, including IONM, endoscopy, and ICG videoangiography, may be helpful in improving patient outcome. Our results confirm previous experiences, showing that premeatal meningiomas are very challenging lesions requiring judicious management, and suggest that multimodal intraoperative tools offer a reliable method to achieve satisfactory outcome in terms of EOR, functional results, and, ultimately, quality of life. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Deveze A , Franco-Vidal V , Liguoro D , Guerin J , Darrouzet V . Transpetrosal approaches for meningiomas of the posterior aspect of the petrous bone Results in 43 consecutive patients . Clin Neurol Neurosurg . 2007 ; 109 ( 7 ): 578 - 588 . Google Scholar CrossRef Search ADS PubMed 2. Roche PH , Lubrano V , Noudel R , Melot A , Regis J . Decision making for the surgical approach of posterior petrous bone meningiomas . Neurosurg Focus . 2011 ; 30 ( 5 ): E14 . Google Scholar CrossRef Search ADS PubMed 3. 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Post-treatment edema after meningioma radiosurgery is a predictable complication . Cureus . 2016 ; 8 ( 5 ): e605 . Google Scholar PubMed 24. Seifert V . Clinical management of petroclival meningiomas and the eternal quest for preservation of quality of life . Acta Neurochir . 2010 ; 152 ( 7 ): 1099 - 1116 . Google Scholar CrossRef Search ADS PubMed 25. Nakamura M , Roser F , Dormiani M , Matthies C , Vorkapic P , Samii M . Facial and cochlear nerve function after surgery of cerebellopontine angle meningiomas . Neurosurgery . 2005 ; 57 ( 1 ): 77 - 90 . Google Scholar CrossRef Search ADS PubMed 26. Peyre M , Bozorg-Grayeli A , Rey A , Sterkers O , Kalamarides M . Posterior petrous bone meningiomas: surgical experience in 53 patients and literature review . Neurosurg Rev . 2012 ; 35 ( 1 ): 53 - 66 . Google Scholar CrossRef Search ADS PubMed 27. Bassiouni H , Hunold A , Asgari S , Stolke D . Meningiomas of the posterior petrous bone: functional outcome after microsurgery . J Neurosurg . 2004 ; 100 ( 6 ): 1014 - 1024 . Google Scholar CrossRef Search ADS PubMed 28. Liu JK , Gottfried ON , Couldwell WT . Surgical management of posterior petrous meningiomas . Neurosurg Focus . 2003 ; 14 ( 6 ): 1 - 7 . Google Scholar CrossRef Search ADS 29. Nowak A , Dziedzic T , Marchel A . Surgical management of posterior petrous meningiomas . Neurol Neurochir Pol . 2013 ; 47 ( 5 ): 456 - 466 . Google Scholar PubMed 30. Sade B , Lee JH . Ventral petrous meningiomas: unique tumors . Surg Neurol . 2009 ; 72 ( 1 ): 61 - 64 . Google Scholar CrossRef Search ADS PubMed 31. Sanna M , Bacciu A , Pasanisi E , Taibah A , Piazza P . Posterior petrous face meningiomas: an algorithm for surgical management . Otol Neurotol . 2007 ; 28 ( 7 ): 942 - 950 . Google Scholar CrossRef Search ADS PubMed 32. Selesnick SH , Nguyen TD , Gutin PH , Lavyne MH . Posterior petrous face meningiomas . Otolaryngol Head Neck Surg . 2001 ; 124 ( 4 ): 408 - 413 . Google Scholar CrossRef Search ADS PubMed 33. Wu ZB , Yu CJ , Guan SS . Posterior petrous meningiomas: 82 cases . J Neurosurg . 2005 ; 102 ( 2 ): 284 - 289 . Google Scholar CrossRef Search ADS PubMed 34. Abolfotoh M , Bi WL , Hong CK et al. The combined microscopic-endoscopic technique for radical resection of cerebellopontine angle tumors . J Neurosurg . 2015 ; 123 ( 5 ): 1301 - 1311 . Google Scholar CrossRef Search ADS PubMed 35. Tatagiba MS , Roser F , Hirt B , Ebner FH . The retrosigmoid endoscopic approach for cerebellopontine-angle tumors and microvascular decompression . World Neurosurg . 2014 ; 82 ( 6 ): S171 - S176 . Google Scholar CrossRef Search ADS PubMed 36. Ferroli P , Acerbi F , Albanese E et al. Application of intraoperative indocyanine green angiography for CNS tumors: results on the first 100 cases . Acta Neurochir Suppl . 2011 ; 109 : 251 - 257 . Google Scholar CrossRef Search ADS PubMed 37. Ferroli P , Acerbi F , Tringali G et al. Venous sacrifice in neurosurgery: new insights from venous indocyanine green videoangiography . J Neurosurg . 2011 ; 115 ( 1 ): 18 - 23 . Google Scholar CrossRef Search ADS PubMed 38. Haq IB , Susilo RI , Goto T , Ohata K . Dural incision in the petrosal approach with preservation of the superior petrosal vein . J Neurosurg . 2016 ; 124 ( 4 ): 1074 - 1078 . Google Scholar CrossRef Search ADS PubMed COMMENTS This paper retrospectively reviews a single surgeon, single institution series of 54 patients treated surgically for petrous meningiomas (PM) over 20 years. Not surprisingly, favorable tumor location, small size (with lack of brainstem compression), and benign histological grade were associated with better outcome. The authors also found that a systematic strategy using adjuvant intraoperative neuromonitoring, ICG videoangiography, and endoscopic visualization led to a higher rate of gross total resection and better long-term outcomes. This strategy was not employed until 2007 during the later half of the study epoch. It is difficult to know whether this study is measuring the effect of implementation of a combination of modern surgical adjuvants or the natural maturation of the skills of the operating surgeon. It is somewhat surprising that intraoperative cranial nerve monitoring was not employed prior to 2007. This is a well-established technology that has been employed for several decades to optimize cranial nerve outcome and extent of resection. The use of this technology alone beginning in 2007 would be expected to yield improved results. It is therefore difficult to parse out the added benefit of ICG videoangiography and endoscopy. These tools may have empiric benefit but I do not believe the results of this study can establish their value for resection of PM. The operating surgeon should be congratulated for his excellent results and specifically for the lack of new cranial nerve deficit in a series of technically challenging tumors. Joel D. MacDonald Salt Lake City, Utah The authors present a retrospective series of petrous meningiomas and analysis for predictors of outcome. Specifically, the use of intraoperative monitoring, endoscopy, and ICG videoangiography versus progression free survival, Karnofsky outcome score, extent of resection, and overall survival. As would be expected, the employment of monitoring and adjunct tools as described appeared to improve outcome. Interestingly, the Simpson degree of resection was not significant. Of particular interest is the employment of ICG videoangiography. ICG-videoangiography in skull base surgery may have a prognostic value. Further, it may enhance the technical safety of surgery by distinguishing between a tumor-related and a normal surrounding vessels and evaluate the microvasculature of cranial nerves during tumor resection. Clearly this is an area of future exploration which may provide fruitful results. Carlos A. David Burlington, Massachusetts This is a retrospective review of all patients who underwent microsurgical resection of petrous meningiomas from 1997 to 2016 by the University of Messina group. A multimodal intraoperative protocol, including intraoperative neuromonitoring, endoscopy, and ICG-videoangiography, was implemented in 2007. The 2 time periods were analyzed for differences in extent of resection, Karnofsky performance status, overall survival, and progression-free survival. I think this article is an important contribution. The authors found the use of the multimodal intraoperative protocol predicts extent of resection and good functional outcomes. Although the use of the operating microscope is critical for safely performing posterior fossa surgery, I think most would agree that there is significant value in other available tools. We have used intraoperative neuromonitoring for years and feel it is invaluable. Endoscopic-assisted microsurgery has been a recent addition for us, but I agree it enables one to look around corners and verify extent of resection in many cases before closure. The use of ICG with posterior fossa meningiomas is an interesting concept. As it is usually done at the end of the case, I think it would have prognostic value but would not necessarily prevent the surgeon from doing damage. Regardless, it is a novel application of the technology, and I look forward it's future development. I applaud the authors for the work. Recognizing the need for improvement, their effort has the potential to improve outcomes for those treating this challenging pathology. L. Madison Michael II Memphis, Tennessee Copyright © 2018 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)

Journal

NeurosurgeryOxford University Press

Published: May 22, 2018

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