Electrophysiological Monitoring of Fifth and Seventh Cranial Nerves in Cerebellopontine Angle Lesions

Abstract

Introduction: Neural preservation is particularly imperative in the surgical management of acoustic neuromas. Intraoperative neuromonitoring is essential in structural and functional preservation of these cranial nerves during the operations. Intraoperative stimulus threshold and response amplitude measurements from trigeminal and facial nerves can predict the functional outcome postoperatively. Materials and Methods: A prospective study was conducted on 30 patients over a period of one year from March 2011 to April 2012 in the Govind Ballabh Pant Hospital, New Delhi, India. Results: There were 27 (90%) cases of vestibular schwannomas, one of meningioma (3.33%), and two of epidermoids (total cases n = 30). Among these, 11 (36.66%) were male and 19 (63.33%) were female patients, and 37% of patients in our study were in the age group of 20 to 30 years. Among the vestibular schwannomas, 16 were right sided and 11 were left sided. Hearing loss was the main presenting symptom (56%) followed by tinnitus (27%), facial pain (10%), and gait instability (7%) in our study. Conclusion: Intraoperative neurophysiological monitoring showed strong support in the value of identification of facial and trigeminal nerves, prevention of injury, and value of prognosis. Stimulus thresholds, response amplitude, and proximal-to-distal amplitude ratio can assist the surgeon during tumor dissection.

Keywords

• amplitude
• cerebellopontine angle tumors
• neuromonitoring