Intraoperative Monitoring of Facial Nerve Evoked Electromyography during Surgery for Cerebellopontine Angle Tumors

Usefulness in Prognosis of Postoperative Facial Nerve Function

Abstract

In another report (this issue) the authors described a method of monitoring intraoperative facial nerve evoked electromyography (IFeEMG) by direct electrical stimulation of the intracranial facial nerve and discussed its usefulness in the identification of the facial nerve during surgery for cerebellopontine angle tumors. This report concerns the usefulness of IFeEMG in making prognoses of postoperative facial nerve function. In 21 patients with acoustic neurinomas the correlation between the results of IFeEMG by stimulation of the morphologically preserved facial nerve and postoperative facial nerve function was determined. Patients with no IFeEMG response at the completion of tumor removal had severe postoperative facial palsy, which did not improve. Patients with a good response had no palsy or, at most, mild palsy. These findings suggest that severe postoperative facial palsy due to neurotmesis can be predicted intraoperatively by IFeEMG monitoring. Early surgical treatment is recommended for patients with morphologically preserved facial nerves but no IFeEMG response.