Choreoathetosis during phenytoin treatment.

A patient with symptomatic epilepsy receiving only phenytoin developed choreoathetosis and orofacial dyskinesias. These movement disorders disappeared when the drug was stopped and reappeared when the patient was challenged. Throughout the period of treatment, concentrations of phenytoin in serum were consistently low within the therapeutic range. Interfering symptoms from the cardiovascular system and the absence of some classic symptoms of phenytoin intoxication (nystagmus and dysarthria) contributed to delay the diagnosis. The patient died in hospital and autopsy of the brain showed rather localized encephalomalacies of corpus striatum. The pathogenic action of phenytoin and the role of preexisting brain lesions are discussed. Phenytoin must be suspected as the cause, when patients on this drug present with uncontrolllable epilepsy or neurological or mental deterioration.