Pre- and postoperative facial nerve testing in patients with acoustic neuromas.

Clinical and electrophysiological examination of the facial nerve was performed in 49 consecutive patients, from December 1982 to January 1984, before and after surgical removal of acoustic neuroma. The electrophysiological examination included quantitative electromyography of the facial muscles and facial nerve stimulation with registration of amplitude and latency of evoked muscle potentials. 17 patients had tumours with an extrameatal size of 5-25 mm, 16 had tumours between 26 and 40 mm, and 16 (32%) tumours larger than 40 mm. At preoperative clinical examination, 9 patients had decreased facial motor function; 7 however, only by meticulous inspection, while 2 had a slight paresis. Two patients had hemifacial spasms. 25 patients had prolonged duration of motor unit potentials and/or increased incidence of polyphasic potentials by electromyography. Only one patient had denervation activity. Three patients had decreased amplitude of evoked muscle potentials to supramaximal stimulation of the facial nerve. Motor latency was normal. At the most recent examination between 3 and 12 months postoperatively, 65% of the patients had no or insignificant facial nerve involvement, 10% had slight and 25% significant involvement, of whom 6 had paralysis or only slight reinnervation. The preoperative clinical facial involvement and the degree of electrophysiological abnormality was poorly correlated to the motor function at the time of the most recent examination.