Introduction Epilepsy is among the most common disorder encountered by neurologists in their day-to-day practice. While the majority of seizures can be readily controlled with anti-epileptic drug (AED) therapy, there remains a small subset of patients who are refractory to AEDs. In these patients even polytherapy with three or more frontline AEDs does not achieve adequate seizure control. In the past the medical community had little to offer these medically intractable epilepsy patients whose quality of life was severely affected by ongoing chronic seizures. In the last decade nonpharmacological treatment options of vagus nerve stimulation (VNS) and responsive neurostimulation (RNS) have provided new ammunition in the fight against epilepsy. These options for medically refractory epilepsy shall be discussed in this article. Vagus Nerve Stimulator (VNS) The vagus nerve stimulator (VNS) (manufactured by Cyberonics Inc, Houston, Tx) gained FDA approval in 1997 for the adjunctive treatment of patients over 12 years of age with medically intractable partial onset seizure disorder. Traditionally these are patients who have failed at least 3 frontline AEDs. VNS is a simple device consisting of 2 electrodes, an externally programmable pulse generator and a battery pack. The stimulating electrode is implanted around the midcervical portion of the left vagus nerve while the impulse generator along with the battery pack is implanted in a subcutaneous pocket in the left infraclavicular region. The left vagus nerve is the preferred site of stimulation due to the higher risks of cardiac arrhythmias with right vagus nerve stimulation. This is on account of the fact that the right vagus nerve innervates the sinoatrial node and thus influences heart rate and rhythm. The pulse generator is programmed externally through the skin via a magnetic wand. Different parameters of stimulation can be programmed such as current strength, pulse width, pulse train frequency, current on and off times as well as magnet current strength.
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