Therapeutic Outcomes of Vagus Nerve Stimulation in Intractable Childhood Epilepsy

PURPOSE: VNS has been used as a adjunctive treatment modality in medically intractable epilepsy patients since 1988, and is presently considered a safe and effective mode of treatment. However, its safety and efficacy in pediatric epilepsy patients have not been as well- studied. We the authors have experienced 12 pediatric patients who received VNS implantation, and evaluated the safety and efficacy of the procedure in the pediatric age group. METHODS: 12 patients who received VNS implantation in Yonsei University Medical Center and Sang-gye Paik Hospital Epilepsy Center from June 1999 to April 2004 have been evaluated for clinical symptoms, presence of reduction in seizure frequency, EEG changes and side-effects after VNS implantation. Datas were analyzed retrospectively through review of clinical records, with emphasis on evaluation of effectiveness and safety of the treatment. RESULTS: Mean age of the patients at the time of VNS implantation were 9 years 9 months (+/-60.5 months)(2 year 9 months-17 years 10 months). Mean duration of follow-up was 21.6 months (+/-23.3 months). Five patients out of twelve could be followed-up for more than 12 months. Nine out of twelve patients possessed Lennox-Gastaut syndrome, two were diagnosed as partial seizure with secondary generalization, and one patient had gelastic seizure caused by hypothalamic harmatoma. Eight patients showed more than 50% reduction in seizure frequency compared with baseline 3 months after the implantation, with two patients exhibiting complete seizure ablation. One patient showed a 25% decrease in seizure frequency, and VNS was ineffective in three patients. Among the patients with more than 50% reduction of seizures, two patients respectively showed a 75% and 90% decrease in seizure frequency at 12 months and 24 months post-operatively. One case of hoarseness, one case of dyspnea during sleep, one case of post-operative wound infection and one case of generator malfunction were noted after VNS, but most of these adverse effects improved through manipulation of output current. Wound infection necessitated surgical revision and generator failure required surgical removal of the device. EEG patterns of the two patients with complete seizure ablation exhibited marked improvement of background rhythms and reduction of epileptogenic discharges, but others did not show any significant improvement in their EEG. CONCLUSION: This study showed significant improvement in seizure frequencies among medically intractable pediatric epilepsy patients after VNS, and most of its adverse effects could be controlled without discontinuation of treatment. Therefore, we believe that VNS is a safe and effective treatment modality in pediatric patients with intractable epilepsy, and merits wider implementation for medically intractable epileptic children in the future.ope