Electrophysiological study of Bell palsy: electrically elicited blink reflex in assessment of prognosis.

The electrically elicited blink reflex was tested serially in 81 patients with Bell palsy. In 56 patients, the reflex returned before excitability of the distal segment of the facial nerve was lost, indicating recovery of conduction across the involved segment before distal degeneration. These patients generally showed a good clinical recovery within a few months after onset. The reflex latency, however, was considerably prolonged during the first month, suggesting demyelination or other pathologic change. The reflex latency was reduced considerably during the second month and returned to normal levels during the third or fourth months. In the remaining 25 patients, direct response to facial nerve stimulation became unelicitable before reflex responses returned, indicating distal degeneration of the nerve. In this group of patients, clinical recovery was prolonged and generally incomplete.