tVNS and Stroke Rehabilitation: What the Evidence Actually Shows | For Clinicians | Neuromodulation for Rehabilitation

Why This Article?

Stroke remains one of the leading causes of adult disability worldwide. In the UK, prevalence is projected to reach approximately 1.4 million by 2025, with societal costs of £43 billion. Up to 80% of stroke survivors experience limb impairment, and only approximately 20% achieve full upper limb recovery. Many experience a plateau in functional gains within the first 3 to 6 months, leaving a large population of chronic stroke survivors with persistent moderate-to-severe arm and hand weakness.

Post-stroke impairments extend beyond motor function. Post-stroke dysphagia affects 37 to 78% of acute patients, post-stroke depression affects approximately 33% of survivors, and post-stroke cognitive impairment affects 17 to 83% depending on assessment criteria.

Conventional rehabilitation remains the cornerstone of stroke recovery. However, there is a well-recognised unmet need for adjunctive therapies that can enhance neuroplasticity and amplify the effects of rehabilitation, particularly for patients who have plateaued with standard approaches. This is the space that vagus nerve stimulation occupies.

The concept is straightforward: stimulating the vagus nerve during rehabilitation exercises creates a neurochemical environment that enhances the brain's capacity to reorganise and relearn. An implanted VNS system (Vivistim) has already received FDA approval for stroke rehabilitation, establishing that the principle works. Transcutaneous vagus nerve stimulation (tVNS) offers a non-invasive route to the same mechanism.

Anatomical Concepts distributes the tVNS® system in the UK. This article provides clinicians with a thorough overview of the evidence for vagus nerve stimulation in stroke rehabilitation, covering both the established implanted approach and the emerging transcutaneous evidence.

How VNS Enhances Stroke Rehabilitation

The Paired VNS Paradigm

The concept of paired VNS is central to understanding how vagus nerve stimulation enhances stroke rehabilitation. Brief electrical stimulation of the vagus nerve, delivered when a patient performs a rehabilitation movement, creates a time-limited neurochemical window that enhances experience-dependent cortical plasticity. This pairing of stimulation with task-specific practice drives reorganisation of motor networks in a targeted, movement-specific manner.

A critical principle: VNS delivered outside a rehabilitation context shows minimal benefit. The neuroplasticity-enhancing effects are movement-specific and context-dependent. VNS amplifies whatever neural activity is occurring at the time of stimulation, meaning it must be paired with the specific movements and functional tasks the patient is attempting to recover.

Key Neurochemical Mechanisms

Norepinephrine release via the locus coeruleus: Vagal afferents project from the NTS to the locus coeruleus. VNS triggers rapid release of norepinephrine throughout the cortex, enhancing signal-to-noise ratio in active neural circuits and facilitating long-term potentiation (LTP).

Acetylcholine release via the nucleus basalis of Meynert: VNS activates projections to the nucleus basalis, triggering cortical release of acetylcholine. This is essential for cortical map reorganisation and enhances the specificity of plasticity. The combined release of norepinephrine and acetylcholine creates a "synaptic eligibility window" lasting several seconds, during which active neural circuits are primed for strengthening.

BDNF upregulation: A 2026 prospective study of 139 patients (Xue and Ma) demonstrated that taVNS significantly increased serum BDNF levels and decreased S100-beta levels compared to rehabilitation alone, with functional scores positively correlated with BDNF levels.

Anti-inflammatory effects: VNS engages the cholinergic anti-inflammatory pathway, suppressing pro-inflammatory cytokines. Animal studies have demonstrated that taVNS improves white matter remyelination and suppresses neuroinflammatory signalling in ischaemic stroke models (Long et al., 2022).

KEY POINT: VNS enhances stroke rehabilitation through a convergent neurochemical mechanism: simultaneous release of norepinephrine, acetylcholine, and serotonin creates conditions that amplify experience-dependent cortical plasticity during rehabilitation exercises. This is fundamentally different from rTMS or tDCS, which directly stimulate cortical tissue. VNS creates the conditions for the brain to learn more effectively from rehabilitation.

Why the Ear? The Anatomy Behind tVNS

The auricular branch of the vagus nerve (ABVN) provides the anatomical basis for transcutaneous stimulation. The cadaver dissection study by Peuker and Filler (2002) established that the cymba conchae has 100% vagal innervation, compared with approximately 45% at the tragus. The fMRI study by Frangos et al. (2015) confirmed that cymba conchae stimulation activates the NTS, locus coeruleus, dorsal raphe, amygdala, and nucleus accumbens.

This anatomical precision matters enormously: stimulation at the wrong site simply does not activate the brainstem pathways that drive the therapeutic effect.

The Implanted VNS Evidence: Proof of Principle

The implanted VNS evidence is critical context because it establishes beyond reasonable doubt that paired VNS + rehabilitation works for stroke recovery.

The Pivotal VNS-REHAB Trial (Dawson et al., 2021, The Lancet)

This randomised, triple-blind, sham-controlled trial across 19 stroke rehabilitation services in the UK and USA enrolled 108 participants with moderate-to-severe arm weakness at least 9 months after ischaemic stroke.

FMA-UE improvement: 5.0 points (VNS) vs 2.4 points (control), p=0.0014
Clinically meaningful response (≥6 FMA-UE points at 90 days): 47% VNS vs 24% control, p=0.0098
Long-term follow-up showed sustained benefits at 1 to 3 years, with 66% achieving clinically meaningful improvements at 1 year

In August 2021, the FDA approved the Vivistim Paired VNS System for stroke rehabilitation, the first neuromodulation device approved specifically for this indication.

KEY POINT: The implanted VNS evidence establishes the principle that vagal neuromodulation paired with rehabilitation enhances motor recovery after stroke. The question for transcutaneous VNS is whether a non-invasive approach can achieve comparable benefits.

The Transcutaneous VNS Evidence

Upper Limb Motor Recovery

Multiple RCTs have now examined taVNS for upper limb motor recovery after stroke:

Redgrave et al. (2018, Sheffield, UK): The first published study of taVNS paired with upper limb rehabilitation. 13 chronic stroke participants achieved a mean FMA-UE improvement of 17.1 points with 92% attendance and no serious adverse events. This uncontrolled feasibility study led to the design of the TRICEPS trial.

Wu et al. (2020, China): Randomised pilot of 21 subacute stroke patients. FMA-UE, WMFT, and FIM scores were significantly higher in the taVNS group, with improvements maintained at 12-week follow-up.

Wang et al. (2024, China): Double-blinded RCT of 40 subacute stroke patients. The taVNS group showed significant improvements in FMA-UE and ARAT, with neurophysiological evidence of enhanced cortical activation.

Badran et al. (2023, USA) MAAVNS pilot: This tested whether pairing matters for transcutaneous VNS. Using a closed-loop EMG-triggered system, 20 chronic stroke survivors received either movement-paired or continuous unpaired taVNS.

Paired (MAAVNS): FMA-UE improvement of 5.00 ± 1.02 (Cohen's d = 0.63)
Unpaired: FMA-UE improvement of 3.14 ± 0.63 (Cohen's d = 0.30)
The paired group achieved larger effects with fewer total stimulation pulses

Xue and Ma (2026, China): The largest single-centre study (n=139). taVNS showed significantly superior outcomes across all measures: FMA-UE, ARAT, MBI, BDNF increase, and S100-beta decrease.

Gait and Lower Limb Recovery

Wang et al. (2024, China): The largest lower limb study (n=169) showed that combining taVNS with tDCS produced the most pronounced improvements in gait, balance, and lower limb function.

Post-Stroke Dysphagia

Wang et al. (2022, China): The first RCT for taVNS in post-stroke dysphagia. 40 acute stroke patients showed significantly larger improvements in swallowing assessments, persisting at least 4 weeks after treatment ended.

Post-Stroke Depression

Liu et al. (2024, China): Double-blind RCT of 80 patients. taVNS showed significant reduction in depression scores with improvements in activities of daily living, supported by biomarker evidence.

What the Meta-Analyses Tell Us

Gao et al. (2023, JNNP): 7 RCTs, 263 participants. Medium effect size for motor function (g=0.432). Larger effects for taVNS devices, acute/subacute phase, and higher weekly intervention frequency.

Wei et al. (2023): 8 RCTs, 266 patients. VNS enhanced upper extremity function via FMA-UE (SMD=0.73, p < 0.00001) and WMFT (SMD=0.82, p < 0.00001).

Li et al. (2025): 4 taVNS-specific RCTs, 129 participants. Overall effect SMD=1.28 (p < 0.0001). However, at 3-month follow-up, effects were not sustained (p=0.12). This is an important finding that needs further investigation.

KEY POINT: The meta-analytic evidence consistently supports taVNS combined with rehabilitation for improving motor function after stroke, with medium to large effect sizes. However, the evidence base is largely from small, single-centre studies, predominantly from China, and long-term durability is uncertain.

The Pairing Question: An Honest Discussion

A key distinction must be addressed transparently.

Implanted Vivistim uses precisely paired stimulation: a 0.5-second VNS burst is triggered at the exact moment the patient performs a high-quality movement. This precise temporal pairing is believed to be critical for maximising neuroplasticity.

Standard taVNS is typically delivered continuously or on a duty cycle (e.g., 30 seconds on / 30 seconds off) during or before rehabilitation sessions. It is NOT precisely paired with individual movements.

The Badran et al. (2023) MAAVNS pilot provides the first evidence that pairing matters for transcutaneous delivery too. However, even unpaired continuous taVNS has shown positive results in multiple RCTs, suggesting that it may still enhance the overall neuroplasticity-promoting environment during rehabilitation. Closed-loop taVNS systems are under active development.

The TRICEPS Trial: What to Watch For

The TRICEPS trial is the most important ongoing trial for the UK. It is a multicentre RCT across 15 to 19 NHS stroke centres, enrolling 243 participants with chronic stroke arm weakness (6 months to 10 years). Participants receive taVNS or sham with home-based rehabilitation for 12 weeks. Led by Sheffield Teaching Hospitals and funded by the NIHR, results are expected July 2026.

If positive, this could transform stroke rehabilitation in the UK by making vagal neuromodulation accessible at scale without surgical implantation.

How Does tVNS Compare with Other Neuromodulation?

Feature	rTMS	tDCS	taVNS
Mechanism	Direct cortical stimulation	Subthreshold cortical modulation	Neuromodulatory (NE, ACh, 5-HT release)
Evidence for stroke motor recovery	Moderate-high	Low-moderate	Low-moderate (emerging)
FDA/CE approval for stroke	No	No	Yes (implanted VNS only, FDA)
Cost	High (>£20,000)	Low (~£500 to 2,000)	Low-moderate (~£2,000 to 4,000)
Home use potential	No	Limited	Yes
Seizure risk	Small but present	Minimal	No known risk

Key distinction: rTMS and tDCS directly modulate cortical excitability. taVNS operates through a fundamentally different mechanism: it increases neuromodulatory tone to enhance the brain's capacity for experience-dependent plasticity. The approaches are not mutually exclusive; one study showed additive benefits when combining taVNS with tDCS.

Stimulation Parameters

Parameter	taVNS Range Across Stroke Studies
Frequency	20 to 30 Hz (most commonly 25 Hz)
Pulse width	100 to 500 µs (most commonly 200 to 300 µs)
Intensity	Titrated to sensory threshold, typically 0.1 to 5 mA
Delivery mode	Continuous or duty cycle (30s on/30s off)
Session duration	20 to 60 minutes
Schedule	5 days per week
Treatment duration	3 to 12 weeks
Site	Left cymba conchae

Safety Profile in Stroke Patients

taVNS has a favourable safety profile in stroke patients. Across the trials reviewed, no serious device-related adverse events were reported.

Common, mild and transient:

Skin irritation/redness at electrode site (< 15%)
Headache (< 5%)
Fatigue, tingling at stimulation site

Stroke-specific considerations:

Most studies stimulate the left ear
Li et al. (2022) included haemorrhagic stroke patients without safety concerns, though most evidence is from ischaemic stroke
Cardiac monitoring is prudent in patients with arrhythmias
Standard contraindications apply: implanted cardiac devices, pregnancy, active ear infection

Regulatory and Access Context

Vivistim (implanted VNS): FDA-approved (August 2021) for chronic ischaemic stroke upper limb rehabilitation.

The tVNS® E device (tVNS Technologies GmbH, Germany) holds Class IIa certification under EU-MDR 2017/745. CE-marked indications include epilepsy, depression, chronic migraine, and Prader-Willi syndrome. Stroke rehabilitation is not a specific CE-marked indication but falls within the scope of clinical use for neurological conditions.

NICE has not published specific guidance on VNS for stroke rehabilitation. The TRICEPS trial results could inform future NICE deliberations.

What We Don't Yet Know

Whether taVNS achieves the same magnitude of benefit as implanted VNS. No head-to-head comparison exists.

Optimal parameters. No standardisation across stroke studies.

Long-term durability. The Li et al. (2025) meta-analysis found benefits were not sustained at 3-month follow-up, contrasting with implanted VNS data showing sustained improvements at 1 to 3 years.

Whether pairing is essential. The MAAVNS data suggest it helps, but even unpaired delivery has shown benefit.

Which stroke patients benefit most. Time since stroke, lesion location, severity, and stroke type likely influence response.

Western population replication. The TRICEPS trial is critical for this.

Practical Guidance for Clinicians

Candidate Selection

Adults with upper limb motor impairment following ischaemic stroke who have plateaued with standard rehabilitation
Consider for subacute or chronic stroke
Patients willing to engage in structured rehabilitation exercises alongside stimulation
Absence of cardiac pacemakers or implanted devices

Treatment Initiation

Based on the literature: 25 Hz, 200 to 300 µs pulse width, intensity titrated to sensory threshold, delivered during rehabilitation exercises
Session duration: 30 to 60 minutes
Schedule: 5 days per week for minimum 4 to 6 weeks (longer may be preferable)
Stimulation should be concurrent with goal-directed, task-specific rehabilitation practice
High-intensity repetitive task practice (300+ repetitions per session) appears to be important

What to Tell Patients

VNS paired with rehabilitation is an FDA-approved approach for stroke recovery (using an implanted device). The transcutaneous approach offers a non-invasive alternative.
Multiple trials show that taVNS combined with rehabilitation can improve arm and hand function beyond rehabilitation alone.
Engagement in rehabilitation exercises during stimulation is essential.
The device is well-tolerated, with side effects limited to mild skin irritation.
A large UK NHS trial (TRICEPS) is underway and will provide more definitive evidence.

Conclusion

The most honest summary is this: vagus nerve stimulation paired with rehabilitation represents one of the most exciting developments in stroke recovery in recent years. The principle is established by the implanted VNS evidence (Dawson et al., 2021, The Lancet), which led to FDA approval.

Transcutaneous auricular VNS offers a non-invasive, accessible, and cost-effective route to the same mechanism. Multiple RCTs and meta-analyses demonstrate positive effects on upper limb motor recovery, with emerging evidence for dysphagia, depression, and cognitive outcomes. The effect sizes are promising and the safety profile is consistently favourable.

The evidence is at an earlier stage than for the implanted approach. Most taVNS stroke studies are small, predominantly from Chinese single-centre designs, and the question of long-term durability is unresolved. The distinction between precisely paired and continuous stimulation delivery is an important methodological consideration.

The TRICEPS trial, with results expected in July 2026 from 15 to 19 NHS sites, will be critically important. If positive, it could transform the landscape of stroke rehabilitation in the UK by making vagal neuromodulation accessible at scale without surgical implantation.

For stroke survivors who have plateaued with conventional rehabilitation, tVNS represents a legitimate, evidence-supported adjunctive therapy that can be delivered alongside structured exercises. The mechanistic rationale is strong, the safety profile is favourable, and the clinical evidence, while emerging, is consistently positive.

Related Literature

Peuker ET, Filler TJ. The nerve supply of the human auricle. Clin Anat. 2002;15(1):35-37.
Frangos E, Ellrich J, Komisaruk BR. Non-invasive access to the vagus nerve central projections via electrical stimulation of the external ear: fMRI evidence in humans. Brain Stimul. 2015;8(3):624-636.
Kimberley TJ, et al. Vagus nerve stimulation paired with upper limb rehabilitation after chronic stroke: a blinded randomized pilot study. Stroke. 2018;49(11):2789-2792.
Redgrave JN, et al. Transcutaneous auricular vagus nerve stimulation with concurrent upper limb repetitive task practice for poststroke motor recovery: a pilot study. J Stroke Cerebrovasc Dis. 2018;27(7):1998-2005.
Wu D, et al. Effect and safety of transcutaneous auricular vagus nerve stimulation on recovery of upper limb motor function in subacute ischemic stroke patients. Neural Plast. 2020;2020:8841752.
Dawson J, et al. Vagus nerve stimulation paired with rehabilitation for upper limb motor function after ischaemic stroke (VNS-REHAB). Lancet. 2021;397(10284):1545-1553.
Li JN, et al. Efficacy and safety of transcutaneous auricular vagus nerve stimulation combined with conventional rehabilitation training in acute stroke patients. Neural Regen Res. 2022;17(8):1809-1813.
Long L, et al. Transcutaneous auricular vagus nerve stimulation promotes white matter repair and improves dysphagia symptoms in cerebral ischemia model rats. Front Behav Neurosci. 2022;16:811419.
Wang Y, et al. Effect of transcutaneous auricular vagus nerve stimulation on post-stroke dysphagia. J Neurol. 2022;270(2):995-1003.
Badran BW, et al. Motor activated auricular vagus nerve stimulation as a potential neuromodulation approach for post-stroke motor rehabilitation: a pilot study. Neurorehabil Neural Repair. 2023;37(6):374-383.
Gao Y, et al. Vagus nerve stimulation paired with rehabilitation for motor function, mental health and activities of daily living after stroke: a systematic review and meta-analysis. J Neurol Neurosurg Psychiatry. 2023;94(4):257-266.
Wei T, et al. Efficacy and safety of vagus nerve stimulation on upper extremity motor function in patients with stroke: a meta-analysis. NeuroRehabilitation. 2023;53(3):253-267.
Liu C, et al. Transcutaneous auricular vagus nerve stimulation for post-stroke depression. J Affect Disord. 2024;354:82-88.
Wang MH, et al. Transcutaneous auricular vagus nerve stimulation with task-oriented training improves upper extremity function in patients with subacute stroke. Front Neurosci. 2024;18:1346634.
Wang L, et al. Efficacy of combined tVNS and tDCS on gait in 169 subacute stroke patients. J Rehabil Med. 2024;56:jrm40348.
Li HL, et al. Effects of transcutaneous auricular vagus nerve stimulation with rehabilitation on the recovery of upper extremity function after stroke: a systematic review and meta-analysis. Neural Plast. 2025;2025:9927826.
Li SY, et al. Task-specific cortical mechanisms of taVNS-paired task-oriented training for post-stroke upper extremity dysfunction. Front Hum Neurosci. 2025;19:1652612.
Francisco GE, et al. Long-term outcomes of vagus nerve stimulation paired with upper extremity rehabilitation after stroke. Stroke. 2025.
Xue R, Ma J. Efficacy of transcutaneous auricular vagus nerve stimulation in treating patients with post-stroke motor disorders. Front Neurol. 2026;17:1711146.
Kizil OD, et al. Effects of taVNS added to robotic rehabilitation in patients with ischemic stroke. BMC Neurol. 2026;26(1).
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Review current as of April 2026. Based on evidence available up to and including early 2026. The TRICEPS trial results (expected July 2026) will significantly update the evidence landscape for taVNS in UK stroke rehabilitation.