The effects of topiramate (TPA) adjunctive therapy on cognition in 22 consecutive patients with intractable epilepsy were studied at the Montreal Neurological Hospital, Quebec, Canada. Performance on neuropsychological tests administered on and subsequently off TPM was analyzed. In a second study at the Minnesota Epilepsy Group, St Paul, MN, 16 patients were tested first off, then on TPM. In the Quebec study, significant improvements were observed after discontinuing TPM on 13 measures of verbal and nonverbal fluency and some perceptual tasks. In the Minnesota study, performance was impaired on all tests of cognition after TPM was begun, and especially for tests of fluency, sustained concentration, and visual motor processing speed. 
COMMENT. Topiramate is associated with impairments of fluency, attention/concentration, processing speed, language skills, and perception. Working memory but not retention is affected. The TPM-induced cognitive dysfunction is independent of the order of testing, first on or off medication.
Topiramate-asociated word-finding difficulties are reported from the Institute of Neurology, University College, Queen Square, London . Word-finding difficulties developed in 31 (7.2%) patients with epilepsy during treatment with TPM. Patients with simple partial seizures and a left temporal EEG epileptic focus were especially at risk.