Transtympanic surgery for hemifacial spasm--an electrophysiological study.

Producing deliberate damage to the facial nerve in the middle ear is an established method of treating idiopathic hemifacial spasm. However, no previous electrophysiological studies have investigated the effect of this operation on facial nerve function. Eleven patients undergoing transtympanic facial nerve needling were investigated with electromyography. Following operation reduction in the abnormal discharges and synkinesis typical of hemifacial spasm was seen in the majority of patients. The success of this type of operation, although temporary in some patients, together with other neurophysiological studies conflicts with the hypothesis that this disorder is due to ephaptic transmission caused by vascular compression of the facial nerve in the cerebello-pontine angle.