Background Vagus nerve stimulation (VNS) is an approved treatment for medically intractable epilepsy. The effect of this therapy on body weight is unclear. Hypothetically, VNS could cause weight loss by engaging vagal afferents from the gastrointestinal tract mediating satiety. We performed a retrospective analysis of body weight changes over a period of up to 2 years since VNS implantation.
Patients and Methods We studied 21 patients 35±12 years old, 13M/8F, who received Cyberonics VNS Therapy System for medically intractable epilepsy at the Harborview Medical Center, Seattle, WA between April 1998 and May 2004. The average duration of follow up was 613.1±389.1 days. The study had 80% power with type I error of 0.05 to detect 5% weight change. Data was analyzed with repeated measures ANOVA.
Results Weight change relative to baseline at 30, 60, 120, 360, 480, and 720 days was (mean±+S.D.) -0.17±2.33%, +0.33±2.64%, -0.32±3.56%, +1.09±5.97%, +1.06±7.47%, and +0.33±3.69%, respectively. At all time points these differences failed to reach statistical significance. (figure)
Conclusions Vagal nerve stimulation with parameters typically used in treatment of patients with epilepsy failed to produce clinically significant weight changes. A prospective controlled study will be required to exclude the possibility that VNS counteracts weight-related effects of anti-seizure drugs.