Zonisamide decreases cortical excitability in patients with idiopathic generalized epilepsy

Objective To evaluate changes in cortical excitability after long-term zonisamide (ZNS) administration. Methods Fifteen drug-naïve idiopathic generalized epilepsy (IGE) patients (8 male, mean age 24.9 years) were enrolled. The transcranial magnetic stimulation (TMS) parameters obtained using two Magstim 200 stimulators were resting motor threshold (RMT), motor evoked potential (MEP) amplitudes, cortical silent period (CSP), intracortical inhibition (ICI), and intracortical facilitation (ICF). TMS parameters were compared before and after ZNS administration. Results All patients were administered ZNS monotherapy (200 mg/day) for 8 weeks. No patient reported seizures during the study period. After ZNS treatment MEP amplitudes were significantly reduced in right (−34.2%) and left hemispheres (−37.0%) (Wilcoxon’s signed rank test after Bonferroni’s correction for multiple comparisons, P < 0.05). Mean RMT, CSP, and ICI/ICF were not changed by ZNS (P > 0.05). Conclusions These findings suggest that ZNS decreases cortical excitability in patients with IGE and a MEP amplitude is a useful TMS parameter for evaluating changes in cortical excitability induced by ZNS. Significance The findings in this study are helpful to understand how ZNS affects the excitability of the motor cortex in patients with IGE.