Patients with partial seizures aged 1 week to 19 years (n = 175) were included in several prospective vigabatrin studies at the hospital Saint Vincent de Paul. A decrease in seizure frequency of over 50% was achieved in 70% of patients, with 30% becoming seizure free, and only 6% experiencing an increase. Tuberous sclerosis gave the best response (85%), tumors the lowest (45%), the usual figure for other causes being 70%. Patients with malformations were the most likely to experience seizure increase. Regarding topography of focus, the lowest rate of seizure-free patients was in rolandic foci. Early treatment produced better results. Infants experienced the highest rate of response, but also of relapse, the latter occurring mainly between 6 months and 1 year. The incidence of loss of efficacy depended on etiology and topography of focus, tumors and frontal foci having the highest risk. Occurrence of new seizures was more frequent in young patients with tuberous sclerosis, the third experiencing status epilepticus. Vigabatrin monotherapy could only be achieved in 33% of seizure-free patients, reduction of comedication being a risk of relapse and of further intractability.
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.
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