Abstracts

Rationale: Vagus nerve stimulation (VNS) is approved for adjunctive use in medically refractory partial onset seizures. VNS is a unique form of neurostimulation with programmed intermittent stimulation in addition to on-demand mode stimulation able to be activated by a magnet. Randomized controlled trials demonstrated efficacy with the VNS that improves over time. This study sought to characterize post-marketing magnet use and efficacy over a 2 year time course. Methods: The sponsor-maintained post-marketing data base for patients with VNS was queried to yield a constant cohort of 513 initial patients with partial seizures including simple partial and complex partial seizures. Data was obtained from treating physicians of patients with VNS through surveyed information from multiple providers over 3 months, 1 year, and 2 years time. Data on magnet use included the individual who applied the magnet, and a rating of effective use at the same intervals. Individuals applying the magnet to induce activation of the VNS included the patient, caregiver, family member, or other individual and could include more than 1 person. Not all of the patients reporting magnet use rated its effectiveness. The rating of the efficacy of magnet use was reported as always, most times, some of the time, seldom, and never effective. Results: 513 patients in the cohort of patients with partial seizures included simple partial seizures and complex partial seizures. At baseline evaluation, 326 (63.5%) patients reported magnet use at 3 months, 323 (63.0%) at 1 year, and 330 (64.3%) at 2 years. Magnet-activated VNS stimulation was delivered by patients, caregivers, family members, and other individuals in 129, 70, 126, and 16 @ 3 months; 171, 88, 161, and 17 @ 1 year; and 188, 87, 179, and 22 persons respectively @ 2 years. Detailed information was not available regarding the number of activations per individual producing magnet activated VNS. Never-the-less, the overall percentages of individuals (i.e., patient, caregiver, etc.) activating the VNS did not change appreciably over 2 years. The application of the magnet was reported as always, most, some, seldom, and never effective by 27 (11.3%), 49 (20.6%), 109 (45.8%), 26 (10.9%), and 27 (11.3%) of 238 patients @ 3 months; 28 (9.5%), 78 (26.4%), 137 (46.4%), 34 (11.5%), and 18 (6.1%) of 295 patients @ 1 year; and 32 (10.0%), 81 (25%), 151 (46.6%), 42 (13.0%), and 18 (5.5%) of 324 patients at 2 years, respectively. Conclusions: More than 60% of patients report magnet activation of their VNS during a 2 year period. Over a 2 year period, it was common for other individuals besides the patient to activate the VNS through magnet application at least once. In this post-marketing report, it appears that at least 75% report at least some benefit from the use of the magnet at the 3 month, 1 year, and 2 year time intervals measured. The results suggest that patients and their families or caregivers should also be educated on magnet use. Similar to reports with intermittent VNS from RCTs, magnet ratings of efficacy do not decline over a 2 year span.