Vagus nerve stimulation for intractable epilepsy: outcomes in children and adults

Objectives. Vagus nerve stimulation (VNS) is an accepted treatment for medically intractable epilepsy. However, predictive factors associated with responsiveness to VNS remained unclear. We therefore sought to identify predictive factors that influence responsiveness to VNS in both children and adults. Materials and Methods. We evaluated a retrospective series of 31 patients who underwent VNS for intractable epilepsy at Asan Medical Center from 1998 to 2006. Eighteen patients were younger than 18 years, while 13 patients were aged 18 years or older. We assessed mean seizure frequency, the number of antiepileptic drugs each patient was taking, seizure type, etiology, age at seizure onset, age at implantation, and duration of epilepsy. Results. Forty-three percent of all patients had a seizure reduction of more than 50%. Ten (59%) children had a 50% reduction in their seizures, while three adults (23%) had such a response. Two factors were significantly different between responders and non-responders: age at implantation and age of seizure onset. In a logistic regression analysis, however, no factors were independently associated with the response to VNS. Transient hoarseness and cough were observed in eight of all patients and wound infection and generator failure in one patient each. Conclusions. These results suggest that VNS may be a more effective treatment in children with intractable epilepsy than in adults. It remains difficult to predict which patients will respond to VNS therapy.