Effect of phenytoin on the mental and physical function of patients with Baltic myoclonus epilepsy.

Progressive myoclonus epilepsy (PME) without Lafora bodies, or Baltic myoclonus epilepsy, is characterized by stimulus-sensitive myoclonus, generalized tonic-clonic seizures, and an irregularly progressive course beginning between 6 and 15 years of age. The EEG displays spike-and-wave paroxysms with irregular dominant activity. Baltic myoclonus epilepsy is a single-gene disorder inherited in an autosomal recessive pattern. Early cases were reported from Estonia, and many are now found in Finland, suggesting that the gene frequency is increased in those sharing the Finno-Ugric linguistic base. The use of phenytoin should be avoided in this disorder since its continued administration alone or with other antiepileptic drugs is associated with intellectual and motor deterioration, aggressive behavior, increasing ataxia, and even death. Treatment with valproate and the concomitant elimination of phenytoin have been associated with marked improvement in most cases. Baltic myoclonus epilepsy must be distinguished from Lafora body PME, which is relentlessly progressive and invariably fatal, but can usually be differentiated on clinical grounds.