Phenytoin-induced extrapontine myelinolysis

Antiepileptic drug (AED)-induced side effects still may hinder antiepileptic therapy. We describe a 38-year-old woman with complex focal seizures. Due to normal neuroradiological findings and the lack of evident pathogenetic factors, we diagnosed cryptogenic epilepsy. In response to cognitive side effects, the initial therapy with phenobarbital was replaced by phenytoin treatment only. Subsequent MRI investigation showed a hyperintense lesion in the corpus callosum without gadolinium enhancement. Responding to an increase in seizure frequency (SF), phenytoin was replaced first by lamotrigin monotherapy and then by additional valproate treatment. An MRI follow-up investigation did not show the previously described lesion of the corpus callosum,thus suggesting phenytoin-induced extrapontine myelinolysis. In the literature, vigabatrin-induced demyelinization of the corpus callosum has also been described. In patients treated with the AEDs phenytoin or vigabatrin who demonstrate increased SF,such a side effect should be taken into account and MRI investigation performed.