Preservation of facial function during removal of acoustic neuromas. Use of monopolar constant-voltage stimulation and EMG.

The authors describe a modification in the way the facial nerve is stimulated electrically during operations to remove medium and large-sized (greater than 2 cm) acoustic tumors. This consists of monopolar stimulation with low internal impedance. Proper use of this modified stimulation technique together with acoustic monitoring of the electromyographic responses of facial muscles helps to preserve facial nerve function in patients undergoing these operations, and also decreases the duration of the operation.