Intraoperative transcranial motor-evoked potential monitoring of the facial nerve during cerebellopontine angle tumor resection

Objective: To determine whether transcranial motor-evoked potential (TCMEP) monitoring of the facial nerve (FN) during cerebellopontine angle (CPA) tumor resection can predict both immediate and long-term postoperative FN function. Design: Retrospective review. Setting: Tertiary referral center. Main Outcome Measures: DeltaTCMEP (fi nal-initial) and immediate and long-term facial nerve function using House Brackmann (HB) rating scale. Results: Intraoperative TCMEP data and immediate and follow-up FN outcome are reported for 52 patients undergoing CPA tumor resection. Patients with unsatisfactory facial outcome (HB > 2) at follow-up had an average deltaTCMEP of 57 V, whereas those with HB I or II had amean deltaTCMEP of 0.04 V (t = -2.6, p <0.05.) Intraoperative deltaTCMEP did not differ signifi cantly between groups with satisfactory (HB I, II) and unsatisfactory (HB > 2) facial function in the immediate postoperative period. Conclusion: Intraoperative TCMEP of the facial nerve can be a valuable adjunct to conventional facial nerve electromyography during resection of tumors at the CPA. Intraoperative deltaTCMEP >57 V may be worrisome for long-term recovery of satisfactory facial nerve function.