Abstracts

Rationale: Vigabatrin was approved by the US FDA in 2009 for the treatment of infantile spasms and as an adjunct for the treatment of adults with refractory complex partial seizures. However, this was in use as an anti-epileptic agent in Europe as early as the late 1980s. Vigabatrin is a selective irreversible inhibitor of GABA transaminase. Studies have reported that about a third of patients on vigabatrin will have a related peripheral visual field (VF) deficit, usually after years of treatment. This review was aimed at evaluating the tolerability and sustained efficacy of long-term vigabatrin use. Methods: Twenty-one patients were found that had been taking vigabatrin for at least 2 years. Of these, records were available for 19 patients. Information was recorded regarding age of onset, type of seizures and epilepsy, duration of vigabatrin use, reason for discontinuation if relevant, and any information regarding vision, including physical examination, formal VF, and results of electroretinograms (ERG). Results: Ten of 19 patients were women. The average age at seizure onset was 13 years. Eleven patients were prescribed vigabatrin for seven or more years. Average maximum daily dosage was 3 grams. Thirteen patients had localization-related epilepsy, 3 with vascular malformations and 3 with brain tumors. All patients had previously failed multiple anti-epileptic medications. Twelve patients (63.2%) had discontinued vigabatrin. Of these, 4 stopped secondary to VF constriction and/or abnormality on ERG, all having been on it for at least 2.5 years; one had visual symptoms and 3 did not. Four patients were tapered off because they were seizure-free for years. One patient stopped vigabatrin due to irritability; and 3 stopped due to lack of efficacy. Two patients were still taking vigabatrin at the time of the last follow up visit and remained seizure-free for at least 6 years. Of the remaining 5 patients, 2 died from tumor progression or other non-seizure related cause; 1 died from possible SUDEP; 1 was in a persistent vegetative state after status epilepticus; and 1 was lost to follow up. Of the 13 (68.4%) patients who were developmentally normal with refractory localization-related epilepsy, 6 patients (46.2%) became seizure-free during some period for an average of 7.5 years. Conclusions: Among our 19 patients who took vigabatrin for at least 2 years, four had evidence of VF constriction and/or changes on ERG, all after >2.5 years of treatment. Six patients experienced prolonged seizure freedom for an average of 7.5 years. Unfortunately, this sample size was small and information was reviewed in a retrospective manner. Also, many patients were seen as early as the late 1980s to early 1990s, so there was some inconsistency in terms of how the visual system was evaluated. VF changes generally occurred very late and were mild. Despite the potential risks, vigabatrin is a useful adjunct for patients with medically refractory epilepsy, including localization-related epilepsy, and sometimes leads to long-term seizure freedom.