Significant improvement in frontal lobe associated neuropsychological functions after withdrawal of topiramate in epilepsy patients.

RATIONALE: Topiramate (TPM) is a highly effective anticonvulsant drug, but a comparably high rate of cognitive adverse effects have been reported. In this study, we investigated changes in frontal lobe associated cognitive measures after TPM withdrawal in epilepsy patients hospitalized for presurgical evaluation.
METHODS: Twenty epilepsy patients were administered a brief neuropsychological test battery before and after withdrawal of TPM. Neuropsychological evaluation included a verbal fluency task, verbal (Wechsler's digits) and spatial spans (Corsi block-tapping) and Trail Making Test (TMT, parts A and B). Median baseline dosage of TPM was 237.5mg/d, the median retest-interval was 8 days. Results were compared to a matched group of patients, who had been tested and retested before and after reduction of AEDs other than TPM at comparable time intervals.
RESULTS: After TPM withdrawal, group performance appeared significantly improved in five of six tests administered. The scores of the control patients remained largely unchanged after drug reduction. After withdrawal, the scores of the TPM group did not differ significantly from the results of the control group whereas pronounced differences had been observed before. Individual improvement became apparent in the majority of patients. Cognitive performance was not correlated to current daily dosages/current blood serum levels of TPM.
CONCLUSION: Withdrawal of TPM causes significant improvement in frontal lobe associated measures like verbal fluency and working memory. As withdrawal was part of the preoperative work-up, and not initiated because of patients' complaints or hints of intoxication, cognitive impairment due to TPM appears to be easily overlooked and underestimated.