Can stimulating the vagus nerve be an effective treatment for spinal cord injury recovery?
The vagus nerve is an extremely versatile nerve that plays a role in many of our major involuntary body functions.
This article will explore how spinal cord injury affects the vagus nerve and explain why electrical stimulation of the vagus nerve can boost recovery outlook.
Let’s get started!
What is the Vagus Nerve?
The vagus nerve is the largest of the twelve pairs of cranial nerves that stem from the brain.
“Vagus” means wanderer in Latin, which perfectly embodies the way the nerve affects various organs and essential body functions.
Primary functions of the vagus nerve include:
- Decreasing heart rate, blood pressure, and breathing
- Reducing inflammation
- Improving motivation
- Boosting plasticity
- Reducing depression and anxiety
- Relaying messages between the gut and brain
The vagus nerve plays a significant role in regulating your parasympathetic nervous system, which is responsible for your ‘rest and digest’ or relaxation functions.
It branches off in many different directions and innervates the throat, larynx (voice box), heart, tongue, external ears, lungs, and gastrointestinal tract.
When the vagus nerve is stimulated, its tone increases. High vagal tone allows you to relax by decreasing alertness, slowing down your heart rate, speeding up digestion, and relaxing your bladder and bowel muscles.
What Happens to the Vagus Nerve After Spinal Cord Injury?
The vagus nerve is not directly affected by spinal cord injury because it is not part of the spinal column.
The cranial nerves are located above the spinal cord and branch out separately.
However, many organs and muscles are dually innervated by sensory neurons from the spinal cord and vagus nerve.
Throughout the day, your body switches off between a state of “rest and digest” (parasympathetic response) and “fight or flight” (sympathetic response).
After a spinal cord injury (typically at level T6 and higher), people often experience autonomic dysreflexia. This is when the body overreacts when stimulated in areas below your level of injury.
Your “fight or flight” response is activated, causing a spike in blood pressure, sweating, and anxiety.
Autonomic dysreflexia can cause your stress and relaxation responses to get mixed up.
Can Vagus Nerve Stimulation Promote Spinal Cord Injury Recovery?
Vagus nerve stimulation (VNS) involves using a biomedical device that transmits mild electrical currents to the brain via the vagus nerve.
While it won’t treat your spinal cord injury, VNS can boost your mental and physical health so that your body is in the best condition to pursue recovery.
Clinical trials on animal models of spinal cord injury have shown that electrical stimulation of the vagus nerve helps with recovery.
While there are limited human studies on the effectiveness of VNS for spinal cord injury, VNS is an FDA-approved treatment for depression (a condition commonly experienced after SCI).
By lowering heart rate, blood pressure, inflammation, and increasing deep breathing, VNS can reduce stress and depression.
Additionally, it increases the release of neurotransmitters like norepinephrine, serotonin, and dopamine to improve motivation, mood, and reward perception.
Side Effects of Vagus Nerve Stimulation
Because the vagus nerve affects so many body functions, it comes with many potential side effects.
Side effects of vagus nerve stimulation include:
- Voice changes or hoarseness
- Sore throat
- Shortness of breath
- Changes in heart rate, breathing
- Stomach discomfort
- Difficulties swallowing
The Importance of the Vagus Nerve After Spinal Cord Injury
The vagus nerve helps regulate the autonomic nervous system, which is crucial after a spinal cord injury.
Vagus nerve stimulation can help improve mental and physical health, which helps keep secondary complications like depression in check.
Health is holistic, and by adjusting physical factors like heart rate, blood pressure, and digestion, spinal cord injury patients can feel more relaxed and motivated to work on recovery.
Featured image: ©iStock.com/Ergin Yalcin