Vagus nerve stimulation (VNS) is a type of neuromodulation involving a device that sends electrical impulses to stimulate the vagus nerve. This treatment is done to alter the activity of the nerves. Vagus nerve stimulation(VNS) requires the implantation of a device that sends mild pulses of electrical energy through the vagus nerve in your neck to your brainstem. After it reaches the brainstem, the electrical impulse is discharged to various parts of the brain to alter how the brain cells work.
VNS also works just the way a pacemaker for the heart works, the reason it is sometimes called a “pacemaker for the brain.”
Before we dive into how the Vagus nerve stimulation works, its side effects, and long-term safety, let’s learn what the vagus nerve is. The Vagus nerve is the 10th cranial nerve in the body that carries a considerable amount of indicators from the organs and digestive system to the brain and vice versa.
It majorly forms the parasympathetic nervous system and serves many internal body functions like saliva and mucus production, immune response, orgasm, mood control, heart rate, and muscle sensations.
There is one vagus nerve on both sides of the body. They both begin at the brainstem in the brain and pass through the neck to the chest and abdomen. This links the lungs, neck, heart, and stomach to the brain.
When any part of the vagus nerve is damaged or affected, you might experience the following
- Inflammatory bowel disorders
- Psychiatric disorders
- Hoarseness or loss of voice
- Cardiovascular disorders
There has been proof that vagus nerve stimulation is a promising additional treatment system for anxiety, depression, epilepsy, stress disorder, and inflammatory bowel disease.
VNS is used if a person cannot have surgery or the surgery isn’t working.VNS can also be done as add-on therapy when medications are not sufficient or over bearing. (2). It is used in adults and children above four years of age.
The function of the vagus nerve is altered by stress, anxiety, abdominal surgery, poor lifestyles like overworking, smoking, drinking alcohol, poor nutrition, lack of exercise, sleep, and viral infections
If the vagus nerve gets damaged by any of these, either physical trauma or the growth
of a tumor, it may cause the following symptoms of vagus Nerve Damage
The function of the vagus nerve stimulation is to send mild and consistent electrical charges through the vagus nerve to help control the irregular electrical brain activity that results in seizures.
How Does Vagus Nerve Stimulation Work?
VNS acts by applying steady and mild electrical impulses to the vagus nerve in two different ways:
- Invasive VNS (iVNS) requires surgical implantation of a tiny pulse generator underneath the skin in the left thoracic region. The generator transports sporadic electrical impulses to the brain through the vagus nerve. Studies have shown that electrical impulses exert antiepileptic effects by altering the excitability of nerve cells.
- Transcutaneous VNS(tVNS) procedure is a non-invasive stimulation of the vagus nerve without any invasive surgical procedure. Here, the stimulator is hooked to the auricular concha through the ear clips. This sends electrical impulses to the afferent auricular branch of the vagus nerve.
What condition does the Vagus Nerve Stimulation Treat?
It has been approved by the FDA, for the treatment of epilepsy, inflammatory bowel disease, and psychological disorders like anxiety and depression. (1).
For Use in Epilepsy
Studies have shown that VNS can help control epilepsy by:
Increasing the levels of some important neurotransmitters in the brain that help control seizures
- Increasing blood flow in key brain areas
- Changing the electroencephalogram (EEG) patterns during a seizure( EEG is a test used to measure electrical activities in the brain).
Monitores any sudden increase in the heart rate- 80% of epileptic people usually have an increase in heart rate before a seizure occurs. VNS picks this and immediately sends an extra burst of electrical stimulation to help halt the impending seizure(3)
For Use in Depressio
In July 2015, Vagus nerve stimulation was approved by the FDA for the treatment of severe unipolar and bipolar depression in adults 18 years of age and above who have long-term depression that hasn’t been responding to antidepressant medications. Researchers found that tVNS has remarkably lessened multiple symptoms of depression, including sleep disturbance, psychomotor deceleration, anxiety, and hopelessness.
For use in Cluster Headache
In 2018, vagus nerve stimulation was approved for the acute treatment of migraine. Studies show that using the nVNS for 30 minutes and 60 minutes reduced the pain
level of migraine(4). VNS was also approved for the prevention of cluster headaches in 2019.
When comparing the use of medications to treat migraine and VNS, researchers found that VNS showed significantly low numbers of cluster headaches in a week.
For use in Stroke
After the VNS has been implanted into the chest of the stroke survivor for about a week, a therapist uses a wireless transmitter to send a mild electric pulse to the vagus nerve while physical therapy is on. The stroke survivor carries out specific tasks like shaking hands, flipping a coin, squeezing a ball,holding a cup, etc.
The simultaneous pairing of vagus nerve stimulation with physical exercise increases physical therapy by strengthening neural connections to improve limb functions. ( 5)
While at home practicing rehabilitation exercises, a magnetic activating device can be used to activate the VNS just by swiping over the implant area.
Possible Side Effects and Complications of VNS
We’ve learned that VNS involves the implantation of a pulse generator by use of an invasive surgery. Complications may arise during and after surgery.
Common risks linked to the surgery include:(6)
- damage to the vagus nerve-Manipulating the generator through the skin may disconnect the lead from the generator causing damage to the vagus nerve.
- Injury to blood vessels nearby, especially the carotid artery and jugular vein
- breathing issues
- infection may occur if the surgery wasn’t done properly
- pain at the site
- Possible vocal cord paralysis occurs if the device shifts after implantation.
Common side effects experienced include:(6)
- difficulty swallowing-This may occur when VNS is actively on, which likely could lead to aspiration.
- throat pain
- chest pain
- difficulty breathing-Shortness of breath can occur while actively using VNS. This is why it is contraindicated in patients with obstructivepulmonary disease or asthma.
- Sleep problems
- Tingling in the neck
These side effects mostly happen when the nerve is being stimulated. Generally, they are mild and go away with time(7).
Long-Term Safety of VNS
Vagus nerve stimulation is not a cure. Most people with epilepsy who use VNS notice that their seizures are less severe, happen less often, and have a quicker recovery from each episode. It may take months or years before you notice changes but generally, most people feel wholesome improvements in their quality of life and mood. They experience changes in how they feel especially in people who use VNS for anxiety and depression. Those who use it for epilepsy also said they noticed changes in their behavioral pattern. Research demonstrates that VNS therapy allows progressive, time-dependent, and long-term improvement in depression, seizure control, and mood enhancement. It does not have any neurocognitive adverse effects (8)
For the long-term safety of VNS to be efficient, avoid the following(8)
- Avoid overstimulation- Excessive stimulation of the vagus nerve can be done by overusing the magnet activation frequently.
- Avoid unapproved Uses- The safety and efficacy of VNS have not been approved in conditions like brain surgery, asthma, ulcer, cardiac arrhythmias, and children under the age of 4.
- Do not use it in pregnancy studies have not been concluded.
- Pacemaker Warning signs — Avoid going to places with Pacemaker Warning signs.
- Avoid devices with strong electromagnetic fields-Electromechanical devices with a strong magnetic field can cause the generator to start suddenly. Keep such devices at least 20 centimeters away from your chest
- Avoid blunt trauma to any part of the body below which the lead was implanted can cause damage to the lead.
- Long-term VNS maintenance by the patient is advised as delayed efficacy can occur due to different factors.
In conclusion, VNS is a suitable and safe adjunt therapy for the treatment of epilepsy, depression, and other diseases approved for its use. When used for a long period of time, it could lead to better overall result