Durability of antidepressant response to vagus nerve stimulation (VNS)

Abstract

This study characterized the durability of improvement in patients who responded early or late while receiving vagus nerve stimulation (VNS). In both a pilot and pivotal study, patients were identified who had at least a 50% reduction in symptom scores 3 months (early responders) or 12 months (late responders) after starting VNS. Probabilities were determined for maintenance of response at 12-month and 24-month time-points. Consistency of improvement throughout the 24-month study period was evaluated, testing for change in serial depression ratings. In the pilot study, 30.5%, 23.7% and 45.8% were early responders, later responders, and non-responders, respectively. These rates were 14.6%, 19.5%, and 65.9% in the pivotal trial. The potential confound of alterations in antidepressant treatment was examined in the pivotal trial. In the pilot study, 72.2% and 61.1% of early responders (n=18) were responders at 12 and 24 months, respectively; 78.8% of late responders (n=14) were responders at 24 months. In the pivotal trial, of early responders (n=30), 63.3% and 76.7% maintained response at 12 and 24 months, respectively; of late responders (n=40), 65.0% maintained response at 24 months. Early and late responders had fewer changes in medication than non-responders across the pivotal study period. In both studies, analyses of serial depression ratings showed stable improvement in early and late responders. These samples had exceptional levels of chronicity and treatment resistance. Yet patients who showed substantial clinical benefit maintained the improvement at remarkably high rates. This durability of benefit was not attributable to alterations in other treatments.

Induction of c-Fos and ΔFosB Immunoreactivity in Rat Brain by Vagal Nerve Stimulation

“…After 12 months of VNS, both response and remission rates were about double those at 3 months. In this cohort, it was found that if patients responded beneficially to VNS after either 3 or 12 months of treatment, then efficacy was maintained for up to 24 months (Sackeim et al, 2007).…”

Introduction of Vagus Nerve Stimulation Into a Maintenance Electroconvulsive Therapy Regimen

“…It is instructive to note, however, that many responders in the VNS clinical trials maintained their initial positive response through 24 months. 49 Although remission of depressive symptoms has not been associated with an increase in manic symptoms, this possibility in the future cannot be ruled out.…”

Deep Brain Stimulation for Treatment-Resistant Depression

“…Open-label long-term response and remission rates were higher (27% response rate and 16% remission rate after 12 months of stimulation) and statistically significantly greater than 12-month naturalistic outcomes in a nonrandomized treatment-as-usual comparison group not receiving VNS (13% response rate, 7% remission rate) (31)(32)(33). In longer-term follow-up studies, 21%-50% of patients who responded to VNS failed to maintain at least a 40% decrease in baseline depression severity over 1-2 years (34,35). In an open-label European cohort, 56% of patients who had responded during 1 year of VNS relapsed within the next year (36).…”