Unilateral basal-ganglia involvement likely due to valproate-induced hyperammonemic encephalopathy

A male child suffering from generalized tonic clonic epilepsy, on treatment with valproate, developed fulminant hepatic failure, hyperammonemia and encephalopathy due to drug toxicity. The most extraordinary feature was his MRI (FLAIR image) of brain which showed unilateral hyperintensities in right putamen and caudate nucleus. The patient recovered on withdrawal of valproate with mild residual left sided athetotic movements during remission. Repeat investigation confirmed an improved MRI imaging and normalised blood ammonia levels. The case report is unique because of unilateral involvement of basal ganglia due to valproate-induced encephalopathy.