Effects of topiramate on cognitive function

Objective-To explore the impact of topiramate on tests of intellect and oth er cognitive processes. Methods-This was a retrospective study. The neuropsychological test scores of 18 patients obtained before and after the introduction of treatment with topiramate (median dose 300 mg) were compared with changes in test perform ance of 18 patients who had undergone repeat neuropsychological assessments at the same time intervals. Complaints of cognitive decline precipitated r eferral for reassessment in five cases in the topiramate treated group. The groups were matched for age and intellectual level at the time of the firs t assessment. Patients were assessed using the WAIS-R, tests of verbal and non-verbal memory, language, and perceptual processing. A subgroup of patie nts underwent a brief reassessment after the withdrawal or substantial redu ction of topiramate. Results-Repeat assessments in those taking topiramate were associated with a significant deterioration in many domains, which were not seen in the com parison group. The greatest changes were for verbal IQ, verbal fluency, and verbal learning (p<0.001). Improvements in verbal fluency (p<0.05), verbal learning (p<0.01), and digit span (p<0.001) were recorded in those patient s who had topiramate withdrawn or reduced. Conclusions-In our patient group topiramate had a negative impact on cognit ion which was consistent with subjective complaints of patients. Tests requ iring verbal processing seemed especially sensitive to the drug. A decline in verbal intellect (VIQ), a measure which has been considered by some to b e insensitive to antiepileptic drug effects, was particularly striking. Cau tion is warranted in the interpretation of the findings due to methodologic al Limitations of the study design. Further investigation of mediating fact ors such as serum concentrations, comedication, and other potential risk fa ctors, however, is needed to enable appropriate targeting of treatment with this effective andepileptic agent.