Microvascular decompression of the facial nerve for hemifacial spasm: clinical and electrophysiologic observations.

Eight patients with idiopathic hemifacial spasm were studied before and after decompression of the facial nerve. Seven patients had an excellent clinical response to surgery, with total resolution of the spasm. One patient had a complete facial palsy and sensorineural deafness on the involved side after surgery, with recurrence of the spasm 6 months later. In all patients, synkinetic activity was present on the involved side before surgery and disappeared after surgery. These findings suggest that the disorder involves the extra-axial portion of the facial nerve. The findings do not require an etiologic role of vascular compression because the response to surgery could be related either to mild trauma of the nerve during the surgical procedure or to subsequent fibrosis.