The prognostic value of facial nerve conduction velocity in patients with Bell's palsy.

The facial nerve conduction velocity was measured in 30 healthy subjects (60 sides) and in 51 patients with a unilateral Bell's palsy. The normal value was 47.8 +/- 5.1 m/s. Incomplete recovery was common in Bell's palsy when the velocity was below 30 m/s. Mild synkinesis was observed in only one patient when the nerve conduction velocity was above 30 m/s. When the degree of degeneration revealed by electroneuroneography did not exceed 60%, the conduction velocity was in the normal range. For degrees of degeneration in excess of this, the conduction velocity decreased in parallel with the increase in the degree of degeneration.