Hemiballism in a patient with partial motor status epilepticus treated with phenytoin

A 13-year-old girl developed left partial motor status epilepticus with severe postictal hemiparesis. Magnetic resonance imaging showed a right frontoparietal hyperintense T2 weighted signal. Treated with phenytoin, carbamazepine and phenobarbital, seizures subsided but left choreic-like flinging movements, consistent with hemiballism, presented 2 days later. On phenytoin withdrawal, symptoms gradually remitted with mild residual dystonia at 14 months follow-up. It is speculated that the lesion might have rendered the cortex more susceptible to phenytoin, inducing unilateral toxicity.