Acute encephalopathy and myoclonic status induced by vigabatrin monotherapy]

Vigabatrin (VGB) is a new antiepileptic drug useful in refractOry partial seizures. Psychosis as a secondary effect of VGB is well known. This drug may even induce new epileptic seizures. We report a 69-year-old hypertensive patient with multiple cerebral infarcts. She was diagnosed as having late onset symptomatic partial epilepsy (complex partial seizures and generalized secondary motor partial seizures). She had been receiving VGB 3 g/day in monotherapy. She came to the emergency room in a psychotic state with new epileptic seizures. We performed an EEG and video during the ictal phase. The patient was awake, conscious and partially oriented. The video showed generalized myoclonic jerks involving facial and limb muscles, separated by non-convulsive intervals lasting three minutes. The EEG showed spike and wave discharges over a diffuse slow-wave background activity. The patient was conscious throughout the recording. The electroclinical picture was considered as an encephalopathy-associated generalized myoclonic status. VGB was replaced by phenytoin. Two weeks later, and after a clinical improvement, a new recording showed the disappearance of signs of encephalopathy and the myoclonic status. Epileptic seizures induced by VGB are well reported. Several pathogenic mechanisms have been suggested. In our case the myoclonic status was related to a non-dose dependent encephalopathy induced by VGB. The electroclinical improvement after withdrawal of the drug supports this possibility.