Persistent cerebellar ataxia with cerebellar cognitive affective syndrome due to acute phenytoin intoxication: A case report

ABSTRACT

Phenytoin is one of the commonly used antiepileptic drugs. The common dose dependent and reversible neurological side effects of phenytoin are nystagmus, diplopia, dysarthria, ataxia, incoordination, chorioathetosis, orofacial dyskinesias and drowsiness. Persistent cerebellar dysfunction with cerebellar atrophy is a well known complication of long term phenytoin use. There are several mechanisms proposed including hypoxia due to frequent seizures or toxic effects of phenytoin on cerebellar Purkinje cells. However, irreversible cerebellar dysfunction following acute phenytoin intoxication is rare. We report a 20 year old female who presented with nystagmus, dysarthria, limb and truncal ataxia with orofacial dyskinesias and chorea. She also had cognitive and affective symptoms in the form of reduced attention, slow responses, lalling speech, blunting of affect, inappropriate laughter, reduced self care and executive dysfunction. The symptoms started 2 weeks following the initiation of phenytoin 300mg/ day, given prophylactically following left basal ganglia bleed. Her serum phenytoin was in toxic range, hence phenytoin was stopped. Her PET scan revealed bilateral cerebellar hypometabolism. At 6 months follow up, she had persistent ataxia with cognitive and affective dysfunction and follow up MRI showed diffuse cerebellar atrophy. The clinical and radiological fi ndings suggest that acute phenytoin intoxication is responsible for persistent ataxia and cerebellar cognitive affective syndrome.