VAGUS NERVE-STIMULATION FOR TREATMENT OF PARTIAL SEIZURES .1. A CONTROLLED-STUDY OF EFFECT ON SEIZURES

Vagus nerve stimulation (VNS) was shown to reduce seizure frequency in refractory epilepsy patients in two pilot studies. Based on these res ults, a multicenter, prospectively randomized, parallel, double-blind study of patients with refractory partial seizures was initiated. Afte r a 12-week baseline period, identical vagus nerve stimulators were im planted and patients randomized to either a high or low 14-week VNS tr eatment paradigm. The primary objective was to demonstrate that high V NS (therapeutic parameters) was more effective in reducing partial sei zure frequency than was low VNS (less or noneffective parameters). Pat ients continued receiving antiepileptic drugs (AEDs) with plasma conce ntrations held constant throughout the study. We report results of the first 67 patients to exit the 14-week acute phase. After 14 weeks of VNS, 31 patients receiving high VNS experienced a mean seizure frequen cy percentage reduction of 30.9%, which was statistically significant as compared with the mean seizure frequency percentage reduction of 11 .3% in 36 patients receiving low VNS (p = 0.029, t test; p = 0.036, Wi lcoxon rank-sum test). In addition to the significant intragroup p-val ues, mean seizure frequency percentage change reached statistical sign ificance for high VNS (p < 0.001) but not low VNS (p = 0.072) as compa red with baseline. Twelve of 31 (38.7%) patients receiving high VNS ac hieved at least 50% reduction in seizure frequency whereas 7 of 36 (19 .4%) patients receiving low VNS experienced at least 50% reduction aft er 14 weeks. The implant procedure and VNS therapy were well tolerated . Our study confirmed the effectiveness of VNS as treatment for epilep sy patients with refractory partial seizures.