Abstracts

Rationale: Vagus nerve stimulation (VNS) therapy was finally approved as a formal treatment for patients with medically refractory epilepsy by the Japan Ministry of Health, Labour and Welfare in 2010. It is also fortunate for the Japanese population because VNS is fully covered by health insurance and is indicated for both localization related epilepsy and generalized epilepsy. Then the number of cases has been gradually increasing in Japan. Early response by VNS was examined in patients who underwent implantation of VNS Therapy^TM System at our epilepsy center.Methods: Twenty-two patients underwent implantation of the device and started VNS therapy from December 2010 through May 2011 in our institute. All cases took full preoperative work-up including long-term video-EEG monitoring, and were not considered candidates for cranial surgery. Demipulse Model 103 Generator and PerenniaDURA Model 303 Lead were implanted in all cases.Results: Nine cases were female and 13 cases were male patients. The youngest case started VNS at the age of 6, and the oldest case was 56 years old. The mean age was 30 years old. Twelve patients had localization related epilepsy and 10 patients suffered generalized epilepsy. Four cases (18%) finished cranial surgery before VNS and showed recurrence or residue of seizure events. In patients followed up for more than a month, 10 cases (59%) demonstrated more than 50% seizure reduction, and 5 cases (29%) showed less than 50% seizure reduction. Non-responders in terms of seizure frequency were 2 cases (12%). Two cases experienced freedom from seizure events by VNS. One patient showed transient vocal cord paralysis.Conclusions: Seizure reduction by VNS is gradual and its efficacy is usually judged one to two years after the beginning of VNS. However, early response less than half a year has been obviously demonstrated in our cases. Therefore VNS is actively recommended hereafter as a palliative option for patients with medically refractory epilepsy unless cranial surgery is indicated.