Vagal Nerve Stimulation Encouraging in Stroke Rehab

February 26, 2015

NASHVILLE, TENNESSEE — A preliminary clinical study suggests that vagal nerve stimulation (VNS) as an aid to rehabilitation in stroke patients appears safe and feasible, with some signs of efficacy.

Presenting the 20-patient controlled study here at the International Stroke Conference (ISC) 2015, Jesse Dawson, MD, Glasgow Western Infirmary, United Kingdom, concluded that the results were encouraging and merit further study.

Dr Dawson noted that arm weakness is very common after stroke, affecting about half of patients, and new treatments are urgently required.

He explained that the vagus nerve connects with brainstem structures and activation causes release of pro-neuroplastic mediators, such as acetylcholine, over the cerebral cortex.

"If we time release these neurotransmitters at the specific time of movements during rehabilitation we may drive neuroplasticity for those specific tasks. There is some evidence of efficacy in this regard in preclinical models of stroke," he said.

VNS is already used to treat epilepsy, and the Cyberonics device used in this study has been implanted into 90,000 patients with epilepsy since 1997, Dr Dawson reported. The implantation involves a short surgical procedure (about 1 hour).

The UK VNS Stroke Study included 20 patients with chronic ischemic stroke and moderately severe arm dysfunction (mean Action Research Arm Test score, 33). The mean age was 60 years, and the patients were approximately 2 years post-stroke. Participants were randomly assigned to receive intensive physiotherapy with or without VNS.

Physiotherapy was delivered in three 2-hour sessions each week for 6 weeks. Each session included 300 to 400 movements, and in the VNS group each movement was paired with a 0.5-second burst of stimulation.

No serious adverse events were reported with the vagal nerve stimulation. Minor adverse events included nausea, mild dysphagia, and transient hoarse voice (thought to be related to the surgical implantation).

The main efficacy measure, Upper Extremity Fugl-Meyer (UEFM) score, which measures upper limb function, was numerically improved in the treated group, but this did not reach significance in the intention-to-treat analysis. However, the result did become significant in the per protocol analysis.

Table. Change in UEFM Score

Analysis VNS Group Control Group Difference P Value
Intention-to-treat analysis (n = 20) 8.7 3.0 5.7 .064
Per protocol analysis (n = 19) 9.6 3.0 6.5 .038

 

A US study is now underway to see whether the results can be replicated.

Commenting on the findings, session chair, Kennedy Lees, MD, also from Glasgow Western Infirmary, who was not involved in the study, said it is "an intriguing idea. The numbers are tiny but this is very much something that needs to be progressed further."

The UK VNS Stroke Study was funded by MicroTransponder Inc, which has developed the VNS technology.

International Stroke Conference (ISC) 2015. Presented February 12, 2015. Abstract LB14.

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