Cerebellar atrophy in an epileptic child: is it due to phenytoin?

A four and half year old epileptic child on phenytoin therapy since one year presented with signs of cerebellar dysfunction. Serum phenytoin level was high (33 mcg/ml) and computerised tomographic scan of the brain showed severe generalised cerebellar atrophy. The cerebellar signs represented drug over dosage and toxicity and persisted long after omission of phenytoin.