Vagus nerve stimulation and tech to treat chronic health conditions

Vagus nerve stimulation, function and activation to battle chronic health conditions

There is a growing body of positive evidence to the effectiveness of addressing the vagus nerve in chronic health conditions. Poor vagal tone has been implicated and noted in various diagnoses including irritable bowel syndrome, autoimmune conditions including rheumatoid arthritis and SLE, metabolic conditions including Type 2 diabetes and obesity, and inflammatory conditions including asthma and fibromyalgia. Chiropractors are more aware than most with regard to vagus nerve stimulation and its function.

Let us review and understand the nerve’s pathway, innervation, and the bidirectional flow of information between the viscera and the central nervous system via the “wandering” nerve. We will then dive into methods and tools to measure vagus nerve stimulation activity, and how we can support our patients in practice, to help them achieve more positive health by activating their vagus nerve.

Reviewing the anatomy and physiology of the vagus nerve

The vagus nerve is the 10th cranial nerve, arising from four nuclei in the brainstem:

the dorsal motor nucleus
the solitary tract nucleus
the spinal trigeminal nucleus
the nucleus ambiguus

The left and right roots of the vagus nerve exit from the brainstem at the medulla oblongata, then converge and exit the cranial cavity via the jugular foramen located between the carotid artery and internal jugular vein. It then passes through the neck adjacent to these important blood vessels within the carotid sheath.

Within the neck, there are sensory branches sent to the skin of the ear (auricular branch) and motor branches sent to the pharyngeal and laryngeal muscles which make up the airway and the muscles around the vocal cords. These branches are important when it comes to supporting vagus nerve function and elevating vagal tone.

As it enters the thorax, branches are sent to the pulmonary plexus and carotid plexus. As you may infer, these branches send afferent and efferent signals to and from the lungs and heart, monitoring breath rate, monitoring and regulating inflammation, regulating heart rate via parasympathetic signaling to the heart. The nerve then continues into the abdominal cavity, coursing through the diaphragm alongside the esophagus, to innervate virtually every organ in the abdomen. Branches are sent from the vagus nerve to the stomach, small intestine, large intestine, spleen, kidneys, liver, pancreas and gallbladder.

Functions of the vagus nerve

There is an astounding amount of regulatory information passing through the branches of the vagus nerve, but only 20% of the data passed via vagus is efferent. Approximately 80% of the information passing through the nerve is afferent, signaling to the brain with regard to inflammation levels in the gut, satiety reflexes, blood pressure, and relaying information from the gut microbiome, amongst other functions.

The efferent signals sent via the abdominal branches include but are not limited to regulate digestion, liver detoxification, bile production and release, regulate insulin and pancreatic enzyme release, managing blood pressure via the kidneys, and regulating inflammatory reactions via the spleen and intestinal lymphoid tissue. The majority of the parasympathetic signals to the body are passed via efferent vagus signals, activating the rest, digest and recovery functions of the body.

One of the more important functions of the vagus nerve is control of our inflammatory response in the gut and throughout the body, via the cholinergic anti-inflammatory system. The vagus nerve utilizes the neurotransmitter acetylcholine to regulate TNF-ɑ, IL-1, IL-8, inflammatory cytokine production in the macrophages (Lerman, 2016). When this response is effectively regulated, inflammation is effectively controlled, allowing for recovery of damaged or affected tissues. We all know what can take place when the inflammatory cascade is unregulated.

Conditions associated with vagus nerve dysfunction

Chronically-elevated cytokine levels are known to cause depression, explained by the fact that longer-term cytokine overexpression leads to a reduction in serotonin levels (Felger, 2013; Schiepers, 2005). Dysfunction of the vagus nerve plays an important role in the pathogenesis of depression and post-traumatic stress disorder (PTSD), which also have a strong link to inflammatory bowel diseases and irritable bowel syndrome (Breit, 2018).

Autonomic function is critical in the stress response and exposure to traumatic stress can result in autonomic dysfunction and alterations, allowing for inflammatory dysregulation. Over the longer term, these changes can alter brain circuits involved in the stress response, causing anxiety or PTSD to be diagnosed (Gurel, 2020).

The vagus nerve also can limit histamine release from mast cells using the cholinergic anti-inflammatory system. Parasympathetic nerves express histamine receptors on branches in the lungs, helping to signal with regards to histamine-induced bronchoconstriction — the route of asthmatic reactions and mast cell activation (Hoffman, 2009, 2012).

Potential symptoms and conditions associated with low vagal tone and targets for therapy include, but are not limited to:

Obesity and weight gain (Karason, 1999)
Irritable bowel syndrome (Coss-Adame, 2014)
Depression (Felger, 2013) and anxiety (Breit, 2018)
Chronic fatigue syndrome (Vanelzakker, 2013)
Fibromyalgia (Martins, 2021)
Tachycardia (Buschman, 2006)
Gastroparesis (Lindeboom, 2004)
Gastric reflux and heartburn (Goyal, 2008)
Autoimmune diseases (Bellocchi, 2022)
Long COVID (Proal, 2021)

Many of our patients are dealing with these conditions without any assessment of the root causes or pathophysiology of these conditions. A well-functioning vagus nerve is heavily involved in the optimal function of our organs and the control of inflammation, making it a perfect target for therapy when these conditions have been diagnosed.

Targeting the vagus nerve for therapy

Vagal tone is best assessed by heart rate variability (HRV), a direct sign of vagus innervation to the heart and a sign of resilience toward stress and sympathetic innervation to the heart.

Measurement of HRV can be very beneficial to the assessment of vagus nerve dysfunction. Patients can use wearable technologies to track this number throughout the day or night to learn more about their resilience and vagus nerve function. Once they are ready to make positive changes, activation via vagus nerve stimulation can begin.

Exercises and therapies to support optimal vagus nerve function can be provided quite easily in the chiropractic office setting. Most of the therapies can be focused on a few branches of the vagus nerve that have specific functions:

The auricular branch of vagus relays sensory information from the skin of the auricle and can be targeted with sensory-focused therapies including acupuncture and acupressure (Wang, 2022).
The pharyngeal branches of vagus send motor signals to the pharyngeal musculature at the back of the throat, preserving airway integrity, maintaining the gag reflex, and allowing for swallowing to occur effectively. Gargling with salt water and triggering the gag reflex are effective exercises to support tonality in the vagus nerve.
The laryngeal branches of vagus send motor impulses to the laryngeal musculature, also preserving airway integrity, as well as creating tension at the level of the vocal cords. Humming, chanting and singing are wonderful exercises to support vagus nerve function.
The diaphragm — although there is no direct branch of vagus nerve that innervates the diaphragm, slow, deep, diaphragmatic breathing has been shown to be the most effective way to support vagus nerve function in acute and chronic stress circumstances. This is due to the intimate relationship between the vagus nerve, the esophagus, the lungs and the diaphragm directly. Slow, deep, diaphragmatic breathing exercises prescribed to patients dealing with chronic health diagnoses will surely support vagus nerve function and allow for a shift from sympathetic to parasympathetic.

New technologies

In circumstances where these exercises are just not strong enough, there are new technologies being developed that can support electrical vagus nerve stimulation to improve function.

Vagus nerve stimulation is a growing area of research and therapy for nearly all of the conditions for which vagus nerve dysfunction has been identified, listed above. Many of the associated conditions have been positively affected by transcutaneous electrical stimulation of the vagus nerve at the auricle and cervical region along the cervical trunk of the vagus nerve.

Devices that apply stimulation to the cervical region appear to be more effective, and have been cleared by European regulators, the FDA, and Health Canada for the treatment of migraine headache (Hawkins, 2017), cluster headache and hemicrania continua, as well as emergency use authorization for breathing difficulties related to asthma and SARS CoV-2 infection.

Devices stimulating the cervical trunk of the vagus nerve appear to be more effective as stimulation of these fibers provides access to a greater quantity of fibers along the vagus nerve. Stimulation to the auricular branch fibers on the ear only provides access to 1% of the vagus nerve fibers found in the cervical trunk.

Some cervical trunk devices have even been shown to significantly improve cognitive performance under sleep deprivation stress, and are used by the U.S. Air Force for their pilots (McIntire, 2021).

A promising future for vagus nerve stimulation

As the research continues to show promising effects, it is exciting to be at the forefront, and be able to bring these tools and therapies to our patients. Seeing our patients thrive, and helping them to achieve more, will only support our goal of allowing people to function at the best of their ability.

Vagus nerve stimulation is the latest and one of the most effective ways for chiropractors to support our patients both in practice as well as in their daily lives.

NAVAZ HABIB, DC, is the author of “Activate Your Vagus Nerve” and the director of Health Upgraded, an online functional health clinic, located in Toronto, Ontario, Canada. For more info on vagus nerve stimulation go to GammeCore.com or ElectroCore.com.