Effects of topiramate in patients with epilepsy and intellectual impairment

There is little knowledge about the effects of topiramate in intellectually impaired epileptic patients. This open prospective study compares seizure frequencies during a 3-month period of topiramate add-on therapy (after 3 months of titration) compared with a 3-month baseline period. An intention-to-treat analysis was made on the first 24 consecutive topiramate-treated adult patients (residents of the Bethel epilepsy centre, therapy-resistant epilepsy, intellectual impairment of different degrees, one half with neurological deficits). The responder rate (at least a 50% reduction in seizure frequency) was 37.5%. One patient became completely seizure-free during postevaluation (up to 24 months). Efficacy was not different between different epileptic syndromes or seizure types (case number too small). Responders had topiramate dosages above 200 mg/day and serum concentrations above 2.2 mug/ml. Six patients (25%) experienced serious neuropsychiatric complications such as confusion and severe deceleration of thinking and acting, up to complete helplessness (at topiramate dosages from 50 mg/day to 900 mg/day and serum concentrations from 2.2 mug/ml to 8.0 mug/ml). Preexisting brain damage may enhance the risk of unwanted central nervous effects.