A New Device for Locating the Facial Nerve During Surgery

Abstract

Richard Prass, MD, PhD, Department of Otolaryngology, and Hans Luders, MD, PhD, Department of Neurology, Cleveland Clinic, have developed an acoustic (loudspeaker) facial nerve electromyogram monitoring system. The use of this monitoring technique has facilitated the dissection of the facial nerve during acoustic neuroma surgery. The stimulus probe is flush-tipped with insulation that reaches to the end. The flush tip prevents widespread electrical current in the presence of cerebrospinal fluid. A reference electrode is placed on the patient's forehead. The recording system consists of bipolar wires placed directly in the facial muscles using a 22-gauge needle. The response is amplified, and an acoustic response is delivered back into the operating room over a loudspeaker for immediate recognition on the part of the operating surgeon. Three types of activity have been identified: burst activity, which results from direct manipulation of the facial nerve; train activity, which results from stretching the nerve;