The vagus nerve is the longest and most complex of the 12 cranial nerves that emerge directly from the brain. It wanders down from the head, through the neck and chest, into the abdomen. Since the vagus nerve extends into many organs, damage can cause an array of health issues. Luckily, the vagus nerve has some ability to heal itself under the right circumstances.
What is the vagus nerve?
The vagus nerve, also known as cranial nerve X, emerges directly from the brainstem and extends throughout the body. It passes through the neck and chest into the abdomen. Along the way, the vagus nerve connects to the pharynx, larynx, esophagus, lungs, heart, and most of the digestive tract. Through these connections, it helps regulate unconscious body functions like heart rate, digestion, breathing, and more.
The vagus nerve is paired, meaning there are actually two vagus nerves. One runs down each side of the body. Together, they form the vagus nerve system.
Functions
The vagus nerve controls many unconscious processes, including:
- Heart rate
- Digestion
- Swallowing
- Sweating
- Speech
- Breathing
It also helps regulate the immune system and inflammation through connections with the spleen, liver, and gut. Additionally, most of the muscles responsible for vocalization are innervated by the vagus nerve.
Anatomy
The vagus nerve originates in the medulla oblongata region of the brainstem. It exits the skull through the jugular foramen along with the glossopharyngeal nerve (CN IX) and accessory nerve (CN XI).
Once in the neck, the vagus nerve gives off several branches:
- Pharyngeal branch – Controls muscles in the pharynx for swallowing
- Superior laryngeal branch – Provides general and taste sensation to the larynx
- Recurrent laryngeal branch – Innervates larynx muscles
- Cardiac branches – Help control the heart
As the vagus nerve continues into the chest, it forms the posterior vagal trunk at the level of the subclavian artery on each side. It then contributes to the esophageal plexus around the esophagus.
In the abdomen, the vagus branches extensively to innervate much of the digestive system. This includes the stomach, small intestine, liver, gallbladder, pancreas, and more. The left and right vagus nerves come close together to form the celiac plexus before terminating.
What causes vagus nerve damage?
Since the vagus nerve extends through so much of the body, it can become damaged in many ways. Some potential causes of vagus nerve injury include:
Surgery complications
Any surgery in the neck, chest, or abdomen carries a risk of damaging the vagus nerve. Some operations like carotid endarterectomy, antrectomy, and esophagectomy have a higher risk. But even routine procedures like thyroid surgery or lung biopsy can sometimes injure it accidentally.
Trauma
Severe trauma to the neck or torso may damage the vagus nerve. Penetrating injuries like gunshots or stabbings pose the greatest danger. But damage can also result from blunt force trauma, like that sustained in a car accident.
Stroke
A stroke affecting the parts of the brainstem that give rise to the vagus nerves may injure them. This most often results from occlusion of the vertebral or posterior inferior cerebellar arteries.
Radiation
Radiation treatment for head, neck, or chest cancer may damage the vagus nerve. This can occur during treatment or result from scar tissue formation afterwards.
Viral infections
Viruses like herpes simplex, varicella-zoster, and Epstein-Barr can sometimes infect the vagus nerve. This may cause temporary dysfunction or longer lasting nerve damage.
Autoimmune disorders
Rare autoimmune conditions like polyarteritis nodosa and Churg-Strauss syndrome can cause inflammation and damage to the vagus nerve.
Diabetes
Long-standing and poorly controlled diabetes may result in vagus neuropathy. High blood glucose levels are thought to injure the nerve over time.
Signs and symptoms
Signs and symptoms of vagus nerve damage vary depending on where the injury occurs along the nerve pathway. They may include:
Swallowing difficulties
Damage to the pharyngeal branch can make swallowing hard. Food or liquids may go down the “wrong pipe,” causing coughing or choking. This symptom sometimes improves with therapy.
Hoarse, breathy voice
Hoarseness and voice changes result from injury to the recurrent laryngeal nerve. This makes it harder to tighten the vocal cords and control volume.
Slow heart rate
Impaired vagal signaling often leads to low resting heart rate and related issues like fainting. But rapid heart rates may also occur.
Gastroparesis
Gastroparesis refers to delayed emptying of the stomach contents into the small intestine. Nausea, early satiety, and stomach pain may accompany it.
Erratic blood pressure
Damage affecting the cardiorespiratory signals carried by the vagus nerve can make blood pressure rise and fall unpredictably.
Trouble breathing
Since the vagus nerve controls some breathing muscles, injury to it may lead to shortness of breath or difficulty taking deep breaths.
Diagnosis
Diagnosing vagus nerve damage begins with a full medical history and physical exam. The doctor will ask about symptoms and thoroughly examine the head, neck, and torso for signs of injury.
Tests that may help confirm the diagnosis include:
- Barium swallow: This imaging test evaluates swallowing function.
- Laryngoscopy: Examination of the voice box shows vocal cord movement.
- Esophagogastroduodenoscopy (EGD): A tiny camera inserted through the mouth checks for stomach motility issues.
- Electrocardiogram (EKG): Measures electrical activity of the heart, which the vagus nerve controls.
- Tilt table test: Changes in heart rate and blood pressure are monitored while moving from lying to standing.
- CT or MRI scans: Provides images of the vagus nerve pathway to reveal any damage.
Nerve conduction studies
Nerve conduction velocity (NCV) tests are often done to confirm vagus nerve problems. Small electrodes placed along the nerve pathway measure how fast electrical impulses travel. Slow conduction velocities indicate nerve damage.
Does the vagus nerve heal itself?
The vagus nerve can regenerate and repair some damage through a process called neuroplasticity. But full recovery requires supportive care and often takes significant time.
Neuroplasticity
Neuroplasticity refers to the ability of nervous system cells to adjust their activities and reorganize themselves. It allows nerves to form new connections, remap circuits, and heal after injury.
Through neuroplastic processes, undamaged portions of the vagus nerve may be able to rewire themselves to take over functions lost due to an injury. Nerve regeneration is also possible in some cases.
Factors affecting healing
How well the vagus nerve can heal itself depends on several factors:
- Location: Lower parts of the nerve have better regeneration ability than higher sections.
- Severity: Mild injuries recover better than severe damage or complete nerve transections.
- Age: Younger individuals have greater healing potential.
- Time: Quicker treatment after injury gives the best chance of recovery.
- Comorbidities: Good health supports nerve regeneration.
Axon regeneration
When a nerve is injured, severed axon fibers may regenerate if the cell bodies of neurons remain intact. Damaged peripheral nerves like the vagus have robust regenerative abilities compared to central nervous system nerves.
However, axons regrow slowly, at a rate of only about 1 mm per day. Regenerating axons must traverse long distances to reconnect the entire vagus nerve, which can take months. And axons may not always reinnervate normal target tissues accurately.
Time course
Mild injuries to the vagus nerve may heal in a matter of weeks. But recovery from significant damage often takes many months. And some severe injuries may result in lasting impairment.
Regular checkups help monitor the status of nerve regeneration. Improvement in symptoms provides a good sign that the vagus nerve is slowly repairing itself.
Treatment
Treating vagus nerve damage focuses on supporting its natural healing processes and managing symptoms. Approaches may include:
Vagus nerve stimulation
Electrical stimulation from an implanted vagus nerve stimulator device enhances nerve activity. This helps strengthen neural connections and reorganize nerve pathways. It may also accelerate axon regeneration.
Physical therapy
Physical therapy provides exercises to improve swallowing, breathing, and voice function. This helps retrain the damaged nerve.
Medications
Drugs that increase gut motility can treat digestive problems from vagal injury. Other medications target heart rate abnormalities and low blood pressure.
Surgery
Severely injured parts of the vagus nerve may be surgically repaired using grafts to bridge the gap. But outcomes are often poor.
| Treatment | Purpose |
|---|---|
| Vagus nerve stimulation | Enhances nerve activity and regeneration |
| Physical therapy | Retrains nerve for swallowing and voice |
| Medications | Improve heart rate, digestion, blood pressure |
| Surgery | Repair severely damaged sections |
Prognosis
The outlook for recovering from vagus nerve damage depends greatly on the severity of the initial injury. Mild injuries have an excellent prognosis. But significant trauma or complete nerve transection can lead to permanent impairments.
With optimal treatment, most people see gradual improvements in symptoms over 6 to 12 months as the nerve regrows. But full recovery may take 2 years or longer.
Recovery factors
Factors that improve the chances of making a full recovery include:
- Younger age
- Otherwise good health
- Prompt treatment after injury
- No comorbidities impairing healing
- Good nerve regeneration ability in the damaged area
Even with partial recovery, symptoms may still improve significantly and be managed with ongoing therapy.
Potential complications
Complications that may prevent full recovery include:
- Misdirected axon regrowth
- Formation of painful nerve scar tissue (neuroma)
- Permanent loss of larynx function
- Chronic gut motility problems
- Heart rhythm abnormalities
Prevention
It’s not always possible to prevent vagus nerve damage. But these steps may lower the risks:
- Get regular medical care to manage conditions like diabetes
- Treat infections quickly to prevent nerve inflammation
- Wear seatbelts and avoid risky behaviors to prevent trauma
- Ask about risks to the vagus nerve before surgery
- Follow dosage limits if prescribed nerve-toxic drugs like antibiotics
Pre-surgery planning
Before any major surgery in the head, neck or chest, talk to the doctor about risks to the vagus nerves. Knowing the nerve pathway can help avoid accidental damage during procedures.
Newer techniques like nerve monitoring during surgery may also reduce injury risk. This allows nerves to be identified and protected.
Outlook
Mild injuries to the vagus often heal well with time and conservative treatment. But significant nerve damage may result in impaired functioning that requires ongoing management. Still, recovery is possible in many cases thanks to the nerve’s natural regeneration abilities.
Prompt evaluation of possible vagus nerve trauma allows early intervention to optimize healing. Staying healthy, treating medical conditions, and avoiding re-injury also gives the vagus nerve its best chance at self-repair.
Key points
- The vagus nerve can regenerate after mild-moderate injury due to neuroplasticity.
- But severe damage may lead to permanent impairments.
- Quick treatment, good health, youth, and lower injury location improve recovery odds.
- Symptoms may gradually improve over months as regeneration occurs.
- Therapy and stimulation can aid healing, but outcomes vary.