Vagal Nerve Stimulation

Definition

Vagal nerve stimulation is a treatment for epilepsy in which an electrode is implanted in the neck to deliver electrical impulses to the vagus nerve.


Purpose

Vagal nerve stimulation is an alternative to medication or surgical removal of brain tissue in controlling epileptic seizures. The seizures of epilepsy are caused by uncontrolled electrical discharges spreading through the brain. Anti-seizure drugs interrupt this process by reducing the sensitivity of individual brain cells to stimulation. Brain surgery for epilepsy either removes the portion of the brain where seizures originate, or cuts nerve fibers to prevent the nerve impulses that occur during a seizure from spreading to other parts of the brain. Vagal nerve stimulation uses a different approach; it provides intermittent electrical stimulation to a nerve outside the brain—the vagus, or tenth cranial nerve, which influences certain patterns of brain activity.

The vagus nerve is a major connection between the brain and the rest of the body. It carries sensory information from the body to the brain, and motor commands from the brain to the body. The vagus is involved in complex control loops between these destinations; its precise pathways and mechanisms are still not fully understood. It is also not known how stimulation of the vagus nerve works to reduce seizure activity—it may stimulate inhibitory pathways that prevent the brain's electrical activity from getting out of control, interrupt some feedback loops that worsen seizures, or act in some other fashion.

Vagal nerve stimulation has been effective in reducing seizure frequency in patients whose seizures are not controlled by drugs, and who are either not candidates for other types of brain surgery or who have chosen not to undergo these procedures.

Demographics

Epilepsy affects about 1% of people in the general worldwide population. Approximately 40% of patients do not respond well to medications, however, and so may be candidates for surgical treatment. Vagus nerve stimulation was first performed in the United States in 1988 and received final approval by the United States Food and Drug Administration (FDA) in July 1997. Approximately 10,000 people worldwide have had stimulators implanted as of 2003; about a fifth of these patients are children 12 years old and younger.


Vagal stimulation physiologic challenge News


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