Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Neuroscience

Supervisor

Allison, David J.

2nd Supervisor

Loh, Eldon

Affiliation

Department of Physical Medicine and Rehabilitation, Schulich School of Medicine and Dentistry

Co-Supervisor

Abstract

This study was the first to assess the feasibility, safety and physiological effects of transcutaneous auricular vagus nerve stimulation (taVNS) in participants with spinal cord injury (SCI). Specifically, we investigated its impact on vagal activity and systemic inflammation. Thirty participants received 60 minutes of active or sham taVNS. Heart rate variability (HRV) was recorded to estimate vagal activity, and fasting blood samples were collected before and after stimulation to measure inflammatory cytokines. Safety was evaluated by monitoring treatment-emergent adverse events (TEAEs). TaVNS was feasible and safe, with 100% of participants completing the 60-minute stimulation and no serious TEAEs reported. Compared to sham, active taVNS significantly increased HRV indices of vagal tone, but did not change levels of pro-inflammatory cytokines. These findings suggest taVNS is a feasible, safe and effective neuromodulation technique for SCI. However, further studies with repeated stimulation are necessary to determine its effect on inflammation following SCI.

Summary for Lay Audience

Spinal cord injury (SCI) disrupts the nervous and immune systems, often leading to long-term inflammation. This ongoing inflammation can slow recovery and contribute to other health issues over time. While anti-inflammatory drugs are available, they can have unwanted side effects, especially with long-term use. This highlights a need for safer, non-drug alternatives for treating inflammation after SCI.

The vagus nerve, part of the parasympathetic nervous system (commonly known as the “rest and digest” system), plays an important role in controlling inflammation. Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive technique that uses mild electrical impulses on the outer ear to stimulate this nerve. This can help tone down inflammation without medication. While taVNS has been shown to reduce inflammation in other conditions, its effects in people with SCI have not yet been studied. This study was the first to investigate whether taVNS is a feasible and safe treatment for activating the body’s natural anti-inflammatory response in people with SCI.

Thirty individuals with SCI participated in this study. They received 60 minutes of either active (real) taVNS or sham treatment, where the device was positioned in a way that did not activate the vagus nerve. Feasibility and safety were evaluated based on how quickly participants were recruited, whether they completed the stimulation session, and if they reported any side effects. Blood samples were collected before and after stimulation to measure inflammation, and heart rate was monitored to measure vagus nerve activity.

Results showed that taVNS was a feasible and safe treatment for people with SCI. All 30 participants were recruited within six months and 100% of participants completed the 60-minute session. No serious side effects were reported. Importantly, active taVNS increased vagus nerve activity compared to the sham treatment. However, 60 minutes of taVNS did not reduce levels of inflammation in the blood. Further research is needed to determine whether long-term use of taVNS can help manage inflammation in people with SCI.

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