Vagus Nerve Stimulation for the Treatment of Epilepsy

Abstract

Vagus nerve stimulation (VNS) was the first neuromodulation device approved for treatment of epilepsy. In more than 20 years of study, VNS has consistently demonstrated efficacy in treating epilepsy. After 2 years, approximately 50% of patients experience at least 50% reduced seizure frequency. Adverse events with VNS treatment are rare and include surgical adverse events (including infection, vocal cord paresis, and so forth) and stimulation side effects (hoarseness, voice change, and cough). Future developments in VNS, including closed-loop and noninvasive stimulation, may reduce side effects or increase efficacy of VNS.

Keywords: Epilepsy; Epilepsy surgery; Neuromodulation; Seizures; Vagus nerve stimulator.

Figure 1. AspireSR® Vagus Nerve Stimulator:

VNS system consists of implanted pulse generator surgically implanted beneath clavicle and lead wrapped around left vagus nerve. (Courtesy of LivaNova, Inc. Houston, TX).

Figure 2. VNS Seizure freedom rate and responder rate from systematic literature review.

This data, from 2869 patients across 78 studies, shows increases in both responder rate and seizure freedom rate over time. At last follow-up 60% of patients achieved responder status to VNS and 8% of patients were seizure free. N = 650, 405, 1503, 876, and 326 patients at each follow-up period, respectively. VNS, vagus nerve stimulation. (From Englot DJ, Rolston JD, Wright CW, et al. Rates and predictors of seizure freedom with vagus nerve stimulation for intractable epilepsy. Neurosurgery. 2015;79(3):345–353; with permission.)

Figure 3. Quality of life metrics for patients with VNS.

(A) When examined individually, multiple metrics of QOL show improvement in patients with VNS as rated subjectively by the treating physician. (B) Overall across all 7 subject QOL metrics there was no trend towards improvement over time with increased time of treatment. For A and B, no significant trends over time were observed (F < 11, p > 0.05 per metric, Bonferroni corrected). N = 4666 (0 – 4 months), 3277 (4 – 12 months), 3182 (12 – 24 months), and 1194 (24 – 48 months) patients. QOL, quality of life; VNS, vagus nerve stimulation. (From Englot DJ, Hassnain KH, Rolston JD, et al. Quality-of-life metrics with vagus nerve stimulation for epilepsy from provider survey data. Epilepsy Behav. 2017;66:4–9; with permission.)

Figure 4. Seizure outcomes after VNS treatment in patients with PTE vs. patients with non postraumatic epilepsy.

The median percent seizure frequency decrease (A) and the responder rates (B) are seen with VNS therapy at 3, 6, 12, and 24 months. Over time, the data shows a trend towards improved seizure outcomes in PTE versus non-PTE patients. When examining Engel outcomes clasess very little difference is found when comparing PTE and non-PTE patients at 3 months after VNS implantation (C). 24 months after VNS (D), patients with PTE exhibit Engel Class III more frequently and Engel Class IV–V less frequently, when compared with non-PTE patients. The number of patients is 254, 158, 154, and 71 for those with PTE and 1449, 975, 878, and 364 for those with non-PTE at 3, 6, 12, and 24 months, respectively. (From Englot DJ, Rolston JD, Wang DD, et al. Efficacy of vagus nerve stimulation in posttraumatic versus nontraumatic epilepsy. J Neurosurg. 2012;117(5):970–977; with permission.)