Perioperative lesions of the facial nerve: follow-up investigations using transcranial magnetic stimulation.

Abstract

Peripheral facial palsy can occur after aural surgery and neurosurgery. Routine neurophysiological investigation (utilizing electrical stimulation and the blink reflex) does not allow the direct assessment of the site of a lesion. In the present study transcranial magnetic stimulation (TMS) was applied in order to evaluate the usefulness of this method for prognosis. Twenty-three patients with postoperative facial pareses (after removals of an acoustic neuroma in 12 patients and parotid tumors in 11) were investigated. Ipsilateral short-latency and contralateral long-latency responses (after cortex stimulation) were elicited. At the first examination (11.7 +/- 9 days after onset of the palsy) the components of the blink reflex were absent in all cases. Responses to electrical stimulation were abnormal in 80%. Ipsilateral short-latency responses after TMS could be obtained in 7 patients. Pathological long-latency TMS responses were elicited in 17 patients. Follow-up investigations up to 2 years revealed no prognostic aspects from peripheral electrical stimulation, the blink reflex and the short-latency TMS response. The absence or extent of delay in long-latency responses at first examination was strongly correlated with final clinical outcomes. As improvements of the responses preceded clinical regressions of the paresis, TMS proved to be an important neurophysiological method for an early prognosis of recovery after perioperative lesions of the facial nerve.