Abstracts

RATIONALE: Vagus nerve stimulation (VNS) is increasingly used as adjuvant therapy for medically refractory seizures. Intermittent stimulation helps prevent seizures in a substantial number of patients. For patients that continue to have seizures, placing a magnet over the stimulator at the onset of a seizure is used to try to abort or shorten the seizure, although published data is limited on magnet efficacy. We present data on clinical experience of magnet use with vagus nerve stimulation. METHODS: 36 patients underwent implantation of a vagus nerve stimulator for medically intractable seizures at the University of Michigan and had seizures of sufficient duration to allow opportunity for magnet use. Their devices were activated 2 weeks after surgery, and stimulation parameters were gradually titrated up as tolerated. Magnet-induced stimulation was set 0.25mA higher than the intermittent stimulation settings. Patients and their caregivers were encouraged to use a magnet at the onset of a seizure whenever possible. Patients were excluded if adequate follow up was not yet available (10), or if they had become aura and seizure free after implantation (2). RESULTS: The 24 patients included in this study ranged in age from 9-57 years. 10(42%) were female. 18(75%) had focal epilepsy, 2(8%)had primary generalized epilepsy, and 4(17%)had symptomatic generalized epilepsy. 5 had undergone prior focal resection and one had corpus callosotomy. At latest follow-up, 9(38%) experienced abrupt cessation of at least 50% of their seizures, 9(38%) experienced shorter seizures, 5(21%) experienced decreased seizure intensity, and 4(17%) reported reduced postictal symptoms when the magnet was used. 1(4%) reported no effect. Side effects occurring during stimulation included coughing, and voice changes. CONCLUSIONS: In this series, many patients were able to abruptly terminate their seizures with magnet use. A majority was able to shorten the seizure, decrease seizure intensity, or reduce postictal period. The utility of on-demand magnet use may be under-appreciated. An increased sense of control may contribute to improved quality of life for patients with medically refractory seizures.