This review was conducted to evaluate the long-term prognosis of children responding to
vigabatrin by examining the incidence of increased seizure frequency, loss of efficacy, and appearance of new
seizures in a cohort of 196 children (mean age, 68.2 months; range, 2 months to 19 years) with
drug-resistant epilepsy, who had received
vigabatrin as add-on treatment in clinical trials. The results indicate that an increase in seizure frequency was uncommon, occurring in only 10% of children with highly
drug-resistant epilepsy and that it usually appears shortly after the initiation of treatment. It was clearly not dose-dependent and most often occurred in patients with nonprogressive
myoclonic epilepsy. No specific seizure type was specially involved and usually the problem reversed on discontinuing
vigabatrin. Loss of efficacy was also uncommon (12% of patients), and again no specific seizure type was found to be associated.
Epilepsy syndrome does seem to be a better predictor of loss of efficacy because it occurred most often in symptomatic
generalized epilepsies and
cryptogenic infantile spasms. A total of 21 patients (11%) developed genuinely new types of
seizures. Fifteen of these patients developed new
partial seizures that had little impact on the patients' overall clinical improvement. The new
partial seizures were better tolerated than the initial seizure type which in most cases had disappeared. Approximately 3% of patients experienced new
generalized seizures that aggravated their initial condition. These occurred most often in patients with nonprogressive
myoclonic epilepsy; therefore
vigabatrin should be used with particular caution in such patients.