Zonisamide changes unilateral cortical excitability in focal epilepsy patients.

BACKGROUND AND PURPOSE: To evaluate changes in cortical excitability induced by zonisamide (ZNS) in focal epilepsy patients. METHODS: Twenty-four drug-naїve focal epilepsy patients (15 males; overall mean age 29.8 years) were enrolled. The transcranial magnetic stimulation parameters obtained using two Magstim 200 stimulators were the resting motor threshold, amplitude of the motor-evoked potential (MEP), cortical silent period, short intracortical inhibition, and intracortical facilitation. These five transcranial magnetic stimulation parameters were measured before and after ZNS, and the findings were compared. RESULTS: All 24 patients were treated with ZNS monotherapy (200-300 mg/day) for 8-12 weeks. After ZNS, MEP amplitudes decreased (-36.9%) significantly in epileptic hemispheres (paired t-test with Bonferroni's correction for multiple comparisons, p<0.05), whereas the mean resting motor threshold, cortical silent period, short intracortical inhibition, and intracortical facilitation were unchanged (p>0.05). ZNS did not affect cortical excitability in nonepileptic hemispheres. CONCLUSIONS: These findings suggest that ZNS decreases cortical excitability only in the epileptic hemispheres of focal epilepsy patients. MEP amplitudes may be useful for evaluating ZNS-induced changes in cortical excitability.