Acute effects of phenytoin on brainstem auditory evoked potentials: clinical and experimental study.

In a patient with phenytoin (PHE) intoxication, the brainstem auditory evoked potentials (BAEPs) were lost except for wave I and wave V. The patient recovered. In rats given PHE, we found changes in amplitude, morphology, and latency of BAEP. Within 5 minutes, all waves disappeared except for wave I, and soon thereafter all waves were lost, with PHE plasma concentration between 45.8 and 52.1 micrograms/ml or above. Ninety minutes after infusion, waves gradually reappeared. Loss of BAEP cannot be used as a criterion for brain death unless PHE intoxication is ruled out.