Electrophysiological investigations and prognosis in idiopathic facial palsy.

In 35 patients with idiopathic facial palsy (FP) clinical and electrophysiological examinations were performed during the first month. The patients were followed up until the 4th month to establish the prognostic value of different electrophysiological tests. Electrophysiological investigations consisted of the recording of blink reflex (BR) and the recording of the direct response (DR) elicited by the stimulation of the facial nerve. FP recovered satisfactorily in 80% of the patients. In patients in whom marked paresis remained, DR amplitude ratio of the affected side to the healthy side (DRr) was less than 25%. BR indicated a poor outcome, if it was still absent at the first month. In general, BR and DR measurements gave similar information about prognosis. Rare exceptions could be explained by the representation of different mechanisms by these two methods, demyelination and axonal degeneration.