Vagus nerve stimulation for seizures

It is agreed that 1% of the general population is afflicted with epilepsy a nd close to 30% of epilepsy patients are intractable to medications. In spi te of a recent increase in the number of new medications that are available on the market, many patients continue to have seizures or their seizures a re controlled at the expense of intolerable side effects. Resection epileps y surgery is an alternative; however, not every intractable patient is a go od candidate for this surgery. Additionally, it is only offered to a small fraction of these patients due to the lack of an adequate number of compreh ensive epilepsy programs and financial support for such surgeries. Vague ne rve stimulation (VNS) is a novel adjunctive therapy that has recently becom e commercially available for intractable epilepsy. It is indicated as an ad d-on treatment for seizures of partial onset with or without secondary gene ralization in patients 12 years of age or older. The VNS system is comprise d of a battery generator that delivers regular intermittent electrical stim uli programmed via menu-driven software and an interrogating wand. The gene rator is implanted in the left upper chest and connected to the left cervic al vague nerve via a pair of semi-circular helical electrodes wound around the vagus nerve and wires tunneled under the skin. Surgery is normally comp leted within 2 h under general anesthesia and the patient can go home withi n a few hours postoperatively. Experiments in humans began in 1988 with two single-blind pilot studies that demonstrated the feasibility and safety of this unconventional therapy. Following these studies, two multicenter, act ive-control, parallel, double-blind protocols showed a statistically signif icant reduction in partial onset seizures with reasonable and well-tolerate d side effects. Adverse events related to VNS included voice alteration and a tingling sensation in the throat during stimulation only and a decrease in intensity over several weeks. Coughing during stimulation occurred norma lly when therapy was initiated and shortness of breath occurred mainly duri ng exertion. Long-term follow-up suggests that reduction in seizure frequen cy and intensity is maintained over time. VNS is a novel adjunctive antiepi lepsy therapy that offers patients a better-tolerated option than medicatio ns in general and that is less invasive and extensive than resection surger y. Its efficacy may compare to novel potent anti-epilepsy drugs; however, V NS does not replace resection epilepsy surgery in selected patients in whom chances of seizure-free results are high (70-90%). (C) 2000 IMSS. Publishe d by Elsevier Science Inc.