VNS-REHAB
(2021)Objective
To evaluate whether vagus nerve stimulation (VNS) paired with rehabilitation improves upper limb motor function after chronic ischemic stroke.
Study Summary
Intervention
Patients with chronic stroke and moderate-severe upper limb impairment were randomized to receive either implanted VNS paired with task-specific rehab or sham stimulation with rehab, over 6 weeks of in-clinic therapy followed by home-based therapy.
Inclusion Criteria
Adults with unilateral upper limb weakness from ischemic stroke occurring 9 months to 10 years prior, with moderate-to-severe arm impairment (Fugl-Meyer upper extremity score 20–50).
Study Design
Arms: VNS + rehab vs. sham stimulation + rehab.
Patients per Arm: VNS: 53, Sham: 55
Outcome
Bottom Line
Vagus Nerve Stimulation (VNS) paired with intensive rehabilitation resulted in clinically meaningful and statistically significant improvements in arm impairment and function for individuals with chronic ischemic stroke compared to rehabilitation with a sham VNS device. The rate of clinically meaningful response was approximately doubled with active VNS.
Major Points
- Pivotal FDA-registration trial for VNS paired with rehabilitation in chronic stroke: 108 patients with moderate-severe arm weakness (≥9 months post-ischemic stroke) across 19 UK/US centers.
- First rigorous triple-blind, sham-controlled neuromodulation trial in stroke rehabilitation — all patients received VNS implant; active (0.8 mA) vs sham (0 mA) stimulation during rehab movements.
- Primary outcome: FMA-UE score improved significantly more with active VNS (+5.0 vs +2.4 points, P=0.001) — a 2.6-point between-group difference immediately after 6 weeks of in-clinic therapy.
- Clinically meaningful response (≥6 point FMA-UE improvement) nearly doubled at 90 days: 47% VNS vs 24% sham (P=0.01) — NNT of ~4 for a meaningful motor recovery response.
- WMFT functional score significantly better with VNS at 90 days (P<0.0001) — translating impairment-level gains into real-world functional improvement.
- Excellent safety profile: only 1 serious adverse event (vocal cord palsy that resolved, in the control group) — the VNS implant itself added minimal surgical risk.
- Led to FDA approval (2021) of the Vivistim system — first FDA-approved neuromodulation device for stroke rehabilitation, marking a paradigm shift in chronic stroke treatment.
- Mechanism: VNS during movement is thought to release neuromodulators (acetylcholine, norepinephrine) that enhance synaptic plasticity, pairing neural activity with rehabilitative movements.
- All participants in the chronic phase (median 3+ years post-stroke) — demonstrating that neuroplasticity can be enhanced even years after stroke, challenging the conventional 'recovery plateau' concept.
- 1-year follow-up data (2025 publication) showed sustained and even improved gains — the VNS benefit was durable, not a transient stimulation effect.
Study Design
- Study Type
- Pivotal, randomised, triple-blind, sham-controlled device trial
- Randomization
- Yes
- Blinding
- Triple-blind (participants, outcomes assessors, and treating therapists)
- Sample Size
- 108
- Follow-up
- 90 days after completion of the 6-week in-clinic therapy
- Centers
- 19
- Countries
- United Kingdom, United States
Primary Outcome
Definition: Change in Fugl-Meyer Assessment-Upper Extremity (FMA-UE) score from baseline to the first day after completion of the 6-week in-clinic therapy.
| Control | Intervention | HR/OR | P-value |
|---|---|---|---|
| +2.4 points (SD 3.8) | +5.0 points (SD 4.4) | - (1.03 to 4.2 (for the between-group difference)) | 0.001 |
Limitations & Criticisms
- Narrow eligibility (FMA-UE 20–50, no severe spasticity/sensory loss) excludes the majority of chronic stroke patients with arm weakness — the most impaired patients who need help most are excluded.
- Durability beyond 90 days not established by this trial — though 1-year follow-up (2025) subsequently showed sustained gains.
- Small sample size (n=108) limits subgroup analyses and precision of treatment effect estimates.
- Predominantly male population (64–65%) — results may not fully represent the female stroke population.
- Industry-sponsored by MicroTransponder Inc. (VNS device manufacturer) — inherent conflict of interest in a pivotal FDA-registration trial.
- Requires surgical implantation of a VNS device — invasive procedure with inherent risks (vocal cord palsy, infection, hardware complications) not applicable to all patients.
- Cost of VNS device, surgical implantation, and intensive 6-week rehabilitation program creates significant access barriers — likely limited to well-resourced centers.
- The sham control group still received 6 weeks of intensive rehabilitation (18 sessions) and improved (+2.4 FMA-UE points) — the incremental VNS benefit (+2.6 points) may not justify the cost and surgical risk for all patients.
- Ischemic stroke only — excludes hemorrhagic stroke patients who may also benefit from neuromodulation-enhanced rehabilitation.
Citation
Lancet. 2021 April 24; 397(10284): 1545-1553.