MRI findings in epileptic patients on vigabatrin for more than 5 years.

Although vigabatrin is a promising new antiepileptic drug, its safety has been challenged by the report of dose-dependent central nervous system myelin vacuolation in some preclinical animal studies. Since it has been shown that vacuolation is associated with specific magnetic resonance imaging (MRI) findings in rats and dogs, MRI of the brain was performed in 11 patients with complex partial seizures who had been receiving vigabatrin for 64-78 months (mean 74.0 +/- 5.0 sd) as additional treatment for epilepsy, with a cumulative exposure ranging 4200 to 9360 g. In no case did MRI show white matter changes similar to the pathological findings of microvacuolation observed in animals. These results would appear to confirm that current doses of vigabatrin do not cause myelin vacuolation in humans, even for treatment periods of longer than 5 years.