A pacemaker for the brain? - Let's learn about Vagus Nerve Stimulation (VNS) in simple terms

Imagine that a family member, a friend, or you yourself have epilepsy, or you have been suffering from severe depression for a long time. No matter how much medication you take and how many treatments you try, you can't seem to get the condition under control. Doctors have tried everything they can. In such a situation, you may hear about a slightly different, more advanced treatment. That's what we call VNS, or Vagus Nerve Stimulation.

What is vagus nerve stimulation (VNS)?

Simply put, this is a treatment that changes the way nerves function. To be precise, it's like a pacemaker implanted in the heart. That's why some people call it the "pacemaker of the brain."

This treatment involves surgically implanting a small device under the skin of your upper chest. This device has a very thin wire attached to a special nerve called the vagus nerve in your neck. The device then sends very gentle electrical pulses at regular intervals . These signals travel along the vagus nerve to the brainstem. From there, these signals are distributed to different parts of the brain and begin to change the way brain cells function.

Typically, a doctor will consider VNS therapy when all other treatments have failed. It is currently approved worldwide for a limited number of patients with treatment-resistant epilepsy and treatment-resistant depression. It is also approved as an aid in rehabilitation for some patients who have recently had a stroke.

Where is the Vagus Nerve? What does it do?

There are 12 main pairs of nerves that carry electrical signals from our brain to various parts of the body. We call these cranial nerves. The vagus nerve is the tenth (X) of these nerves. This is the longest cranial nerve in our body.

We have two vagus nerves, one on each side of our body. Both start in the brainstem. They then run through the neck, into the chest, and into the abdomen. Simply put, the vagus nerve is part of a major circuit that connects the organs in our neck, heart, lungs, and abdomen to the brain.

What conditions is VNS therapy used for?

Major agencies, such as the US Food and Drug Administration (FDA), have currently approved VNS therapy for three medical conditions. Let's look at this information in a table.

How does this VNS device actually work?

The truth is, scientists are still not 100% sure how exactly this VNS device works, but they do have some good ideas.

• Epilepsy control: When an epileptic seizure occurs, the brain's electrical activity becomes disrupted. VNS stimulation is believed to increase blood flow to important parts of the brain, alter this disrupted electrical pattern, and increase levels of the neurotransmitters ``norepinephrine'' and ``serotonin'' in the brain, which help control epilepsy.
• For depression management: VNS is thought to reduce symptoms of depression by altering the levels of certain neurotransmitters that control our mood.
• For stroke rehabilitation: This stimulation stimulates the motor cortex, the part of the brain that controls the movement of our arms and hands. This makes it easier for the brain to relearn those movements during rehabilitation exercises.

What does it feel like to have the VNS device on your body?

Most of the time, you won't even notice that this device is on. However, some people may feel a slight difference when the stimulation is on.

• A tickling sensation in the throat or neck
• A slight hoarseness of the voice
• A very mild cough

Even if you feel this way, you usually get used to it over time. But if this stimulation bothers you, talk to your doctor right away. He or she can change the settings on the device and reduce the amount of stimulation.

Who should not have VNS treatment?

VNS therapy may not be suitable for people with certain health conditions. If you have any of the following conditions, you may not be a good candidate for VNS.

• If you are pregnant .
• If you have breathing problems such as asthma or sleep apnea .
• If you have active stomach ulcers (peptic ulcer disease) .
• If you have insulin-dependent diabetes mellitus .
• If you only have one vagus nerve (some people are born with it).
• If you have a condition called dysautonomias, which is an abnormal function of the autonomic nervous system.
• If you are already receiving other brain-stimulating treatments .
• If you have heart rhythm abnormalities (heart arrhythmias) or other heart diseases.
If you have a history of mental illness such as schizophrenia or schizoaffective disorder.
• If you have had part of your left vagus nerve removed in a previous surgery.

What happens before and during VNS surgery?

This is not a major, scary surgery. It usually takes about an hour and a half.

Preparing for surgery

Before the surgery, your doctor will perform a complete physical examination. He or she may also perform several blood tests to make sure there are no other health problems that could interfere with the surgery.

How the surgery is performed

On the day of your surgery, you will be given antibiotics to reduce the risk of infection. You will then be given anesthesia. You may only be numbed in the neck and chest area where the surgery will be performed, or you may be given general anesthesia and put to sleep.

The surgeon makes two very small incisions: one on the left side of the neck (to reach the vagus nerve) and the other on the upper left side of the chest.

1. A thin wire with electrodes is inserted through an incision in the neck and carefully wrapped around the vagus nerve.

2. Then the wire is brought under the skin to the incision in the chest.

3. Through an incision in the chest, a battery-like stimulator (pulse generator), a little bigger than a five rupee coin, is inserted and placed in a small space created above the chest muscle.

4. Finally, the wire from the neck is connected to this stimulator.

Once everything is connected, the surgeon will test the device. Set it to a very low setting and run it for about 30-90 seconds to see if the stimulation is working properly. If everything is OK, the incisions will be closed and stitches will be placed.

What happens after the surgery?

Operating and adjusting the device

You will need to see your doctor again 2-4 weeks after surgery. That's when the device will be properly activated. The doctor will use a computer and a special device (programming wand) to customize the settings for your condition. (For example, how long it will be on, how long it will be off, how strong the stimulation will be, etc.).

You can't change these settings, but you will be given a magnet that you can hold in your hand .

• For someone with epilepsy: When a seizure is about to occur, this magnet can be swiped over the device on the chest. This will provide additional stimulation and may stop the seizure or reduce its severity.
• For someone undergoing stroke rehabilitation: When you swipe this magnet before starting exercise, the stimulation will be activated for 30 minutes.
• Temporarily stop the device: If you hold the magnet over the device, the stimulation will stop. When you remove the magnet, it will start working again as programmed by the doctor.

Battery life

The device's battery typically lasts about 6 years (some last from one year to 15 years). When the battery runs low, the entire stimulator must be replaced. This also requires a minor surgery that is performed through a small incision in the chest.

What are the risks and side effects of VNS treatment?

Like any medical treatment, VNS can have some risks and side effects. Most of these are usually not serious and will subside over time.

How long does it take to heal? What are the results?

You can resume normal activities two days (48 hours) after surgery. The stitches are dissolvable, so there is no need to have them cut.

But it takes a while to see results. It may take a year or more to know exactly how much you will benefit from VNS.

• Epilepsy: VNS does not completely cure epilepsy. It does not completely stop seizures. You will need to continue taking your epilepsy medication. The goal of VNS is to reduce the frequency, severity, and duration of seizures. In one study, about 43% of patients had a 50% or greater reduction in seizure frequency over three years.
• Depression: The effectiveness of VNS for depression is still being researched. As such, it is only considered after medications and psychotherapy have failed. In some studies, only 20%-30% of patients have experienced significant improvement.
• Stroke rehabilitation: In one study, patients who underwent rehabilitation exercises with VNS stimulation had significantly improved arm and hand movements compared to those who exercised without VNS.

What time should I see a doctor?

If you have any of the following symptoms, call your doctor immediately.

• Symptoms of an infection:
• If the incision is red, swollen, or painful to the touch.
• If the cut smells bad or pus-like fluid is draining from it.
• If you feel feverish or have a cold.
• Other serious symptoms:
• If the voice continues to be hoarse.
• If the stimulation is painful, causing difficulty breathing or swallowing.
• If you feel very sleepy.
• If the device seems to be not working properly or there is a signal that the battery is low.
• If your medical condition (epilepsy, depression) worsens.