Vagus nerve stimulation therapy improves motor function after stroke

1. Individuals with moderate-to-severe arm impairment after ischemic stroke experienced greater improvements in arm function after vagus nerve stimulation therapy as compared to those without.

2. There were no severe adverse events reported as related to the trial device.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Loss of motor function is one of the most common and debilitating chronic sequelae arising from ischemic brain injuries. Prior studies in animal models and two small pilot studies have suggested the possible benefit of vagus nerve stimulation in recovering upper extremity motor function; however, no large scale in-vivo study has been performed thus far. This study assessed the value of vagus nerve stimulation (VNS) when combined with rehabilitation for those with chronic moderate-to-severe arm impairment as a result of a unilateral supratentorial ischemic stroke. The study found a significant improvement in return of upper extremity function in the VNS group compared to the control group in the end of the six-week intervention period. This difference persisted after evaluating patients three months after the end of the trial period. As compared to previous pilot studies in this domain, this study had a large subject pool; furthermore, the randomized control trial structure of the study lends itself to best determining causality. Nevertheless, the subject pool notably lacked diversity and the nature of this intervention (i.e., requiring surgical implantation) likely limited the total number of subjects that would be optimal to include to achieve the most ideal degree of certainty. Further geographic variation was correlated to outcomes which may imply possible confounding. Moreover, the durability of such improvements was not noted beyond 90 days after treatment.

Click to read the study in The Lancet

Relevant Reading: Vagus nerve stimulation paired with upper limb rehabilitation after chronic stroke

In-Depth [randomized controlled trial]: This study was a randomized, triple-blind, placebo-controlled trial. The subject pool consisted of 108 patients in the United States and the United Kingdom between the ages of 22 and 80 years, with a prior unilateral supratentorial ischemic stroke that had taken place 9 months to 10 years before enrollment in the study. All included subjects reported moderate-to-severe motor function loss as graded by the Fugl-Meyer Assessment-Upper Extremity (FMA-UE) scale. Subjects were randomly assigned to vagus nerve stimulation with rehabilitation (n=53) or rehabilitation with sham stimulation (n=55). Subjects underwent surgical operation to implant the stimulator lead to the vagus nerve; the patients’ baseline FMA-UE scores were assessed 1 week after implantation. In-clinic rehabilitation commenced the day after the procedure and occurred three times per week for six total weeks in both groups. During rehabilitation therapy, a 0.8 mA, lasting 0.5 s was applied following each repeated movement while the control group received 0 mA pulses. Improvements from baseline were measured 1 day and 90 days after cessation of therapy. FMA-UE score improvements at post-therapy day 1 were higher in the VNS group (mean change 5.0 [SD 4.4] compared to the control group 2.4 [SD 3.8]). Similar findings were replicated at 90 days.

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