Vagus Nerve Stimulation (VNS)
What is vagus nerve?
There's one vagus nerve on each side of your body, running from your brainstem through your neck to your chest and abdomen.
The vagus nerve is the tenth cranial nerve or CN X, and interfaces with parasympathetic control of the heart, lungs, and digestive tract. The vagus nerves are paired; however, they are normally referred to in the singular. It is the longest nerve of the autonomic nervous system in the human body. The vagus nerve also has a sympathetic function via the peripheral chemoreceptors.
The vagus nerve supplies motor parasympathetic fibres to all the organs (except the adrenal glands), from the neck down to the second segment of the transverse colon.
The vagus also controls a few skeletal muscles.
Vagus nerve is responsible for such varied tasks as heart rate, gastrointestinal peristalsis, sweating, and quite a few muscle movements in the mouth, including speech (via the recurrent laryngeal nerve). It also has some afferent fibres that innervate the inner (canal) portion of the outer ear (via the auricular branch, also known as Alderman's nerve) and part of the meninges. This explains why a person may cough when tickled on the ear, such as when trying to remove ear wax with a cotton swab.
What is Vagus nerve stimulation?
Vagus nerve stimulation is a procedure that involves implantation of a device that stimulates the vagus nerve with electrical impulses.
There's one vagus nerve on each side of your body, running from your brainstem through your neck to your chest and abdomen.
Brain cells communicate by sending electrical signals in an orderly pattern. In people with epilepsy, this pattern is sometimes disrupted due either to an injury or the person's genetic make-up, causing brain cells to emit signals in an uncontrolled fashion. This creates over-excitement, somewhat like an electrical overload in the brain, leading to seizures. Seizures can be produced by electrical impulses from throughout the brain, called generalized seizures, or from a small area of the brain, called partial seizures.
Most people with epilepsy can control their seizures with medications called anti-convulsant or anti-seizure drugs. About 20% of people with epilepsy do not respond to anti-seizure medications. In some cases, surgery to remove the part of the brain causing the seizures may be used. VNS may be a treatment option for people whose seizures are not controlled by anti-seizure medications and who are not considered good candidates for surgery; for example, if their seizures are produced throughout the brain
Vagus nerve stimulation is most often used to treat epilepsy when other treatments haven't worked. Vagus nerve stimulation is also a treatment for hard-to-treat depression that hasn't responded to typical therapies.
How Is Vagus Nerve Stimulation Done?
In conventional vagus nerve stimulation, a device is surgically implanted under the skin on your chest, and a wire is threaded under your skin connecting the device to the left vagus nerve. The right vagus nerve is not used because it carries fibres that supply nerves to the heart.
When activated, the device sends electrical signals along the vagus nerve to your brainstem, which then sends signals to certain areas in your brain.
New, non-invasive vagus nerve stimulation devices, which do not require surgical implantation, have been approved for use in Europe to treat epilepsy, depression and pain but have not yet been approved for use in the U.S.
What Are the Risks of VNS?
The risks of VNS include injury to the vagus nerve or nearby blood vessels, including the carotid artery and jugular vein. In addition, there are risks associated with any surgical procedure, such as infection, bleeding and an allergic reaction to the anaesthesia.
