Vestibular and hearing manifestations of phenytoin toxicity: a retrospective series.

We undertook a study to identify the vestibular and hearing abnormalities associated with phenytoin toxicity. Since October 1977, 23 patients with phenytoin toxicity have been referred to the Department of Otorhinolaryngology by the Department of Neurology for electrooculographic (EOG) evaluation. (There have been no cases of serious phenytoin toxicity seen in our department since August 1989.) In addition to EOG, all patients had undergone otoscopic, audiometric, and neurologic examinations. We found that the most common pathologic findings detected by EOG were abnormalities in pursuit tracking. The most common signs found on clinical exploration were cerebellar dysfunction and facial palsy. EOG findings in patients with phenytoin toxicity are compatible with cerebellar disease.