Auditory brain stem response abnormalities in patients with Bell's palsy.

To evaluate the hypothesis of CNS involvement in Bell's palsy, the auditory brain stem responses (ABR) of 31 patients were studied. In nine of these patients ABR abnormalities were found. None of these patients showed evidence of dysfunction of the cochlear nerve. Six of the patients who had abnormal ABR were retested after they recovered from the facial paresis. Five of these patients showed persistent ABR abnormality, and one showed a normalization of the ABR. These results may be consistent with an injury at the brain stem level in some patients with Bell's palsy. The possible causative agent of a reactivation of a herpes simplex virus infection is discussed.