Abstracts

Since its FDA approval in 1997, the VNS, which utilizes intermittent stimulation of the left vagus nerve to reduce the frequency and intensity of seizures, has certainly demonstrated its place as an established treatment for refractory epilepsy patients. The purpose of this study is to evaluate the effects of two VNS parameter settings (low and high) on seizure control, while endeavoring to keep all other patient-related variables constant, specifically concomitant antiepileptic medication/s This is a randomized, double-blind study involving four institutions. The two groups were a low stimulation setting (LSS; n=8) group and a high stimulation setting (HSS; n=5) group comparison for this preliminary report. The LSS group had an output current that set to tolerance, a frequency of 20-Hz, pulse of 500-ms, an on-time of 30-seconds, and an off-time of 10-minutes. The HSS group had an output current set to tolerance, a frequency of 30-Hz, pulse of 500-ms, and an off-time of 1.8-minutes. Patient data was reviewed at 30-, 90-, and 180-day intervals post-activation.. The mean pre-activation seizure frequencies/60-days for the LSS and HSS groups were 16.0 and 43.6, respectively. For the LSS group, the 30-, 90-, and 180-day post-activation mean seizure frequencies were 9.1, 9.1, and 20.4, respectively. For the HSS group, the 30-, 90-, and 180-day post-activation mean seizure frequencies were 17.0, 35.6, and 68 respectively. As a preliminary report, these data show an initial reduction in seizure frequency for both settings up until 90-days post-activation. At 180-days postactivation, both the LSS and HSS groups show an increase in seizure frequency. The low stimulation setting appears equally efficacious to the high setting. This suggests we can use the low frequency stimulation with equal success to the high setting. (Supported by Cyberonics.)