By: Catherine Joachin
Photo Credit: The Defeating Epilepsy Foundation
Cranial nerve X
Cranial nerve X, also known as the vagus nerve or vagal nerves, is the main component of the parasympathetic nervous system, which regulates involuntary functions that allow the body to relax. This nerve relays information from the throat, ear and internal organs to the brain, and controls digestion, heart rate, blood pressure, mood, immune system (Cleveland Clinic, 2026).
Structure and Function
The vagus nerve is the tenth and longest of the twelve cranial nerves, originating in the medulla oblongata, leaving the skull through a large opening known as the jugular foramen and terminating in the lower digestive track (Kenny & Bordoni, 2022). It travels through and connects with the neck, chest, heart, lung, abdomen and digestive tract (Cleveland Clinic, 2026).
The medulla oblongata contains the four nuclei associated with the vagus nerve. The spinal trigeminal nucleus receives information relating to touch, pain and temperature (Patel, Jozsa & Das, 2024). The solitary nucleus receives sensory information from internal organs (Breit & al., 2018). The nucleus ambiguus sends out motor signals to control the muscles of the larynx, pharynx and soft palate responsible for speaking and swallowing (Kenny & Bordoni, 2022). Lastly, most parasympathetic fibres emerge from the dorsal vagal motor nucleus, however parasympathetic fibres travelling to the hearth originate from the nucleus ambiguus (Kenny & Bordoni, 2022).
These nuclei allow the vagus nerve to oversee key bodily functions, such as:
• Swallowing and speaking
• Heart rate, blood pressure and breathing
• Muscle contractions and gland secretion
• Taste sensation
• Touch, pain and temperature
• Digestion
• Immune system
• Mood
• Urine output
(Cleveland Clinic, 2026; Patel, Jozsa & Das, 2024)
Vagus nerve dysfunction
Damage to the vagus nerve can lead to various symptoms, including:
• Difficulty swallowing
• Impaired gag reflex
• Hoarseness or loss of voice
• Loss of appetite
• Nausea and vomiting
• Changes to heart rate
• Dizziness or fainting
• Uvular deviation
• Acid reflux
• Abdominal pain or bloating
(Cleveland Clinic, 2026; Kenny & Bordoni, 2022)
Given that the vagus nerve supplies many organs, damage may also contribute to abnormalities in heart rate, gastrointestinal problems as well as depression and anxiety in people with chronic obstructive pulmonary disease or congestive heart failure (Kenny & Bordoni, 2022).
Vagus nerve stimulation
Vagus nerve stimulation (VNS) is an adjunctive treatment approach for medically refractory epilepsy, approved for children and adults aged 4 and older (Mayo Clinic, 2024). This therapy is a form of neuromodulation that uses a device to regulate central nervous system activity (Kenny & Bordoni, 2022).
Conventionally, this device is a small pulse generator surgically implanted under the skin of the chest that sends mild electrical signals to the left vagus nerve through attached wire (Mayo Clinic, 2024). Although there is also a vagus nerve on the right side of the body, it usually contains more cardiac branches, making it more susceptible to heart-related complications (Kenny & Bordoni, 2022).
A key limitation of vagus nerve stimulation is that it is not cure for epilepsy ; it only reduces the frequency, length and intensity of seizures, meaning that most patients will need to continue taking anticonvulsant medication after the procedure (Cleveland Clinic, 2025). That said, patients that have undergone VNS have reported seizure reduction of 50% and higher (Mayo Clinic, 2024).
Clinical applications of VNS go beyond epilepsy treatment. The United States Food and Drug Administration (FDA) has also approved the use of vagus nerve stimulation for the treatment of major depression and to assist in stroke recovery (Mayo Clinic, 2024). VNS is currently being investigated as a potential treatment of other conditions including Alzheimer’s disease and inflammatory bowel syndrome, however further research is needed to draw meaningful conclusions about its efficacy (Cleveland Clinic, 2025; Mayo Clinic, 2024).
Conclusion
The vagus nerve is a key structure of the parasympathetic nervous system, overseeing important automatic bodily processes. It passes through the neck, throat and abdomen, and connects to many areas of the brain involved in seizure activity. As a result, electrical stimulation of this nerve provides relief through a means to modulate abnormal brain activity responsible for seizures.
References
Breit, S., Kupferberg, A., Rogler, G., & Hasler, G. (2018, March 13). Vagus nerve as modulator of the brain-gut axis in psychiatric and inflammatory disorders. Frontiers in psychiatry. https://pmc.ncbi.nlm.nih.gov/articles/PMC5859128/
Kenny, B. J., & Bordoni, B. (2022, November 7). Neuroanatomy, cranial nerve 10 (vagus nerve). StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK537171/
Mayo Foundation for Medical Education and Research. (2024, December 20). Vagus nerve stimulation. Mayo Clinic. https://www.mayoclinic.org/tests-procedures/vagus-nervestimulation/about/pac-20384565
Patel, N. M., Jozsa, F., & Das, J. M. (2024, September 10). Neuroanatomy, spinal trigeminal nucleus. StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK539729/
Vagus nerve: What it is, function, Location & Conditions. (2026, April 13). Cleveland Clinic. https://my.clevelandclinic.org/health/body/22279-vagus-nerve
Vagus nerve stimulation (VNS): What it is, uses & side effects. Cleveland Clinic. (2025, November 21). https://my.clevelandclinic.org/health/treatments/17598-vagus-nervestimulation
