Closed-loop vagal nerve stimulation for intractable epilepsy: A single-center experience

A new class of heart-rate sensing, closed-loop vagal nerve stimulator (VNS) devices for refractory epilepsy may improve seizure control by using pre-ictal autonomic changes as an indicator for stimulation. We compared our experience with closed- versus open-loop stimulator implantation at a single institution.

We conducted a retrospective chart review of consecutive VNS implantations performed from 2004 to 2018. Bivariate and multivariable analyses were performed to compare changes in seizure frequency and clinical outcomes (Engel score) with closed- versus open-loop devices. Covariates included age, duration of seizure history, prior epilepsy surgery, depression, Lennox Gastaut Syndrome (LGS), tonic seizures, multiple seizure types, genetic etiology, and VNS settings. We examined early (9-month) and late (24-month) outcomes.

Seventy subjects received open-loop devices, and thirty-one received closed-loop devices. At a median of 8.5 months, there was a greater reduction of seizure frequency after use of closed-loop devices (median 75% [IQR 10-89%]) versus open-loop (50% [0-78%], p < 0.05), confirmed in multivariable analysis (odds ratio 2.72 [95% CI 1.02 - 7.4]). Similarly, Engel outcomes were better after closed-loop compared to open-loop confirmed in the multivariable analysis at the early timepoint (OR 0.26 [95% CI 0.09 - 0.69]). These differences did not persist at a median of 24.5 months.

This retrospective single-center study suggests the use of closed-loop VNS devices is associated with greater seizure reduction and more favorable clinical outcomes than open-loop devices at 9-months though not at 24-months. Expansion of this study to other centers is warranted to increase the generalizability of our study.