Somatosensory Evoked Potential Monitoring during Positioning of the Patient for Posterior Fossa Surgery in the Semisitting Position

Somatosensory Evoked Potential Monitoring during Positioning of the Patient for Posterior Fossa... AbstractOBJECTIVE:Midcervical flexion myelopathy is a rare but well-known complication of posterior fossa surgery. To reduce the risk, we routinely used somatosensory evoked potential (SSEP) monitoring during positioning of the patient.METHODS:Fifty-five consecutive patients were operated on for posterior fossa lesions in the semisitting position via a median (5 patients) or a lateral (50 patients) suboccipital approach. During positioning, monitoring of SSEPs by stimulation of the tibial nerve (T-SSEP) as well as by stimulation of the median nerve (M-SSEP) was established. In the case of pronounced SSEP changes, the head was repositioned. Surgery was started after SSEP recordings were unchanged as compared to the baseline investigation.RESULTS:Effective monitoring was possible in all cases. Whereas M-SSEP recordings showed no changes while placing patients in the sitting position, T-SSEP recordings were altered in 14 cases (25%). In cases using the midline approach, SSEP changes were never so pronounced to require repositioning of the head. Head flexion and rotation resulted in significant changes of T-SSEP recordings in eight patients (14.5%), requiring repositioning. In two cases, an amplitude loss was noted. In only two of these eight patients were M-SSEP recordings markedly changed. SSEP recordings after repositioning disclosed recovery of spinal cord function. In no patient were clinical signs of myelopathy observed postoperatively.CONCLUSION:We observed a high incidence of pronounced changes of T-SSEP recordings when the patient's head was flexed and rotated for lateral suboccipital craniotomy in the semisitting position. Despite the low specificity monitoring of T-SSEPs during positioning of the patient for posterior fossa surgery, the semisitting position is strongly recommended. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Neurosurgery Oxford University Press

Somatosensory Evoked Potential Monitoring during Positioning of the Patient for Posterior Fossa Surgery in the Semisitting Position

Somatosensory Evoked Potential Monitoring during Positioning of the Patient for Posterior Fossa Surgery in the Semisitting Position

CLINICAL STUDIES Somatosensory Evoked Potential Monitoring during Positioning of the Patient for Posterior Fossa Surgery in the Semisitting Position Wolfgang Deinsberger, M.D., Petros Christoph is, M.D., Andreas jodicke, M.D., Michael Heesen, M.D., Dieter-Karsten Boker, M.D. Neurosurgical Clinic (WD, PC, A), D-KB) and Department of Anesthesiology (MH), lustus-Liebig-University Giessen, Giessen, Germany OBJECTIVE: Midcervical flexion myelopathy is a rare but well-known complication of posterior fossa surgery. To reduce the risk, we routinely used somatosensory evoked potential (SSEP) monitoring during positioning of the patient. M ETHO DS: Fifty-five consecutive patients were operated on for posterior fossa lesions in the semisitting position via a median (5 patients) or a lateral (50 patients) suboccipital approach. During positioning, monitoring of SSEPs by stimulation of the tibial nerve (T-SSEP) as well as by stimulation of the median nerve (M-SSEP) was established. In the case of pronounced SSEP changes, the head was repositioned. Surgery was started after SSEP recordings were unchanged as compared to the baseline investigation. RESULTS: Effective monitoring was possible in all cases. Whereas M-SSEP recordings showed no changes while placing patients in the sitting position, T-SSEP recordings were altered in 14 cases (2 5 % ). In cases using the midline approach, SSEP changes were never so pronounced to require repositioning of the head. Head flexion and rotation resulted in significant changes of T-SSEP recordings in eight patients (14.5% ), requiring repositioning. In two cases, an amplitude loss was noted. In only two of these eight patients were M-SSEP recordings markedly changed. SSEP recordings after repositioning disclosed recovery of spinal cord function. In no patient were clinical signs of myelopathy observed postoperatively. C O N C L U S IO N : We observed a high incidence of pronounced changes of T-SSEP recordings when the patient's head was...
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Publisher
Congress of Neurological Surgeons
Copyright
© Published by Oxford University Press.
ISSN
0148-396X
eISSN
1524-4040
D.O.I.
10.1097/00006123-199807000-00023
Publisher site
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Abstract

AbstractOBJECTIVE:Midcervical flexion myelopathy is a rare but well-known complication of posterior fossa surgery. To reduce the risk, we routinely used somatosensory evoked potential (SSEP) monitoring during positioning of the patient.METHODS:Fifty-five consecutive patients were operated on for posterior fossa lesions in the semisitting position via a median (5 patients) or a lateral (50 patients) suboccipital approach. During positioning, monitoring of SSEPs by stimulation of the tibial nerve (T-SSEP) as well as by stimulation of the median nerve (M-SSEP) was established. In the case of pronounced SSEP changes, the head was repositioned. Surgery was started after SSEP recordings were unchanged as compared to the baseline investigation.RESULTS:Effective monitoring was possible in all cases. Whereas M-SSEP recordings showed no changes while placing patients in the sitting position, T-SSEP recordings were altered in 14 cases (25%). In cases using the midline approach, SSEP changes were never so pronounced to require repositioning of the head. Head flexion and rotation resulted in significant changes of T-SSEP recordings in eight patients (14.5%), requiring repositioning. In two cases, an amplitude loss was noted. In only two of these eight patients were M-SSEP recordings markedly changed. SSEP recordings after repositioning disclosed recovery of spinal cord function. In no patient were clinical signs of myelopathy observed postoperatively.CONCLUSION:We observed a high incidence of pronounced changes of T-SSEP recordings when the patient's head was flexed and rotated for lateral suboccipital craniotomy in the semisitting position. Despite the low specificity monitoring of T-SSEPs during positioning of the patient for posterior fossa surgery, the semisitting position is strongly recommended.

Journal

NeurosurgeryOxford University Press

Published: Jul 1, 1998

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