Idiopathic facial palsy (Bell's palsy) is the most common mononeuropathy, but one from which 70∼80 percents of patient recover completely without treatment.

The prospective study of 84 facial nerve paralysis was carried out to observe the course of the disease and to correlate the physical findings, electrodiagnostic findings with the prognosis. The suspected lesion site was determined and comparision of compound muscle action potential amplitude, needle EMG, and blink reflex were performed as electrodiagnostic test. The result of 84 subjects was as follows.

1) The class Ⅴ was in 45 cases (52.4%) and the class Ⅳ, Ⅲ, Ⅱ, Ⅰwas in 15 cases (17.8%), 14 cases (16.7%), 2 cases (2.7%), 8 cases (9.5%), respectively.

2) According to the facial nerve pathway, the more distal the lesion, the better the prognosis.

3) There was higher recovery rate in the cases which reveal less than 90% of axonal degeneration.

4) The more the number of muscles which show motor unit action potentials in the lesion side, the higher the recovery rate.

5) There was higher recovery rate in the cases which preserve blink reflex in the lesion side.