Phenytoin-induced cerebellar atrophy in an epileptic boy
A 16-year-old boy was admitted to the hospital with fever and weakness. His systemic examination was normal. His past history included history of seizure for the last 10 years. He was on oral PHT, 5 mg/kg daily once daily. After initiating therapy with PHT 10 years back, he was seizure free for 2 years. Then he started getting seizures that required adjustment in his medication. Patient was also occasionally prescribed clobazam, 5 mg, oral, as and when required. The episodes used to last for a brief period of over 6-7 days. He would then be seizure free for the next 3-4 months. Seizures used to occur at every 3-4 months interval. The boy had history of birth asphyxia and delay in developmental milestones. His previous MRI scans of brain revealed no abnormality. There was no family history of seizure. The boy was managed conservatively for viral fever. After the patient recovered, he was evaluated again due to complaint of difficulty in walking. CNS examination revealed normal mentation with cerebellar signs including gaze-evoked nystagamus, truncal, and appendicular ataxia. MRI scan of the brain was advised and it showed cerebellar atrophy as shown in . The patient had no other neurological and other systemic problems other than epilepsy. Serum phenytoin level was high (30 mcg/ml) and PHT was withdrawn immediately. Patient was started on valproic acid and followed up. The causality assessment was done using the Naranjo scale.[] The causal analysis showed a probable association of the ADR with phenytoin.