Subacute phenytoin intoxication syndrome.

Phenytoin sodium intoxication of subacute onset may occur in cases of nonepileptic patients who receive phenytoin for suppression of cardiac arrhythmias. The case reported here is of a syndrome that consisted of dementia, cerebellar dysfunction, and peripheral neuropathy. Withdrawal of phenytoin was followed by a slow improvement in the syndrome. Awareness of the features of subacute phenytoin intoxication in cardiac patients is important because this entity may mimic cerebrovascular disease. Periodic monitoring of serum phenytoin concentrations is advisable.