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Vagus nerve stimulation (VNS) is a form of medical treatment that uses electrical stimulation of a nerve in the upper body (the vagus nerve) to alter chemical and electrical activity inside the brain. In order to access this nerve, doctors must surgically implant a stimulating device inside the chest. People with major depression sometimes receive vagus nerve stimulation when the usual treatment options for the disorder fail to produce adequate results. VNS is generally safe, and current evidence indicates that it can ease depression symptoms in at least some affected individuals.

Vagus Nerve Stimulation Basics

Doctors use the term vagus nerve to refer to either one of a pair of nerves that originate at the bottom of the brain and pass through the neck before continuing on to the chest and abdomen. These nerves belong to a larger group of nerves, called cranial nerves, which help control involuntary functions throughout the body. Specific parts of the body at least partially controlled by the vagus nerves include your heart, larynx, tongue, stomach, ears and diaphragm.

Electrical stimulation of the vagus nerve is provided by a small, pacemaker-like device called a pulse generator. During surgery, this device is implanted in the upper left chest in the general vicinity of the heart. After installing the pulse generator, a surgeon will guide a wire attached to the device up through the neck and place it in direct contact with the vagus nerve; this wire carries the electrical current needed to stimulate the nerve. Once the surgical procedure is complete, doctors can fine-tune the electrical output of the pulse generator to fit the specific needs of a given patient. Features of this output that can be adjusted include the on/off cycle used for treatment, the overall strength of the electrical signal, the frequency of the electrical signal, and the duration of each individual pulse. Usually, patients also receive a handheld device that lets them adjust certain aspects of their treatment.

The signal from vagus nerve stimulation travels up the nerve to the brain stem, then continues on into the brain’s interior. Although no one knows for sure, doctors and researchers believe that this stimulation alters the chemical and electrical communications network that connects nerves in the brain called neurons. In turn, alteration of this network can change the ways in which different parts of the brain talk to each other. In the case of treatment-resistant depression, this altered communication helps stop or reduce the effects of mild to severe “down” moods. Typically, doctors consider using VNS when their patients have not received adequate symptom relief from at least four other depression treatments.

Effectiveness of Treatment

Not all studies support the effectiveness of vagus nerve stimulation, the American Association of Neurological Surgeons (AANS) reports. However, a number of studies do support the treatment’s effectiveness, at least for a sizable minority of individuals. For example, the authors of a study review published in 2009 in the journal Experimental Neurology concluded that VNS can produce short-term relief of treatment-resistant depression in significant numbers of people; in addition, they concluded that benefits from the treatment can actually grow over time. Another study, published in 2007 in the journal Acta Neurologica Scandinavica also supports the effectiveness of VNS, but notes that the treatment must be adjusted to meet the needs of each individual patient before it truly produces benefits. The National Institute of Mental Health and the Mayo Clinic both view vagus nerve stimulation as a potential option for people with treatment-resistant depression.

Treatment Considerations

The AANS lists potential side effects of vagus nerve stimulation that include sleeplessness, uncontrolled muscle twitching, an altered speaking voice, neck pain, throat pain, spasming in the voice box or throat, tingling or other abnormal skin sensations, coughing or hoarseness, headaches, nausea, and vomiting. Some people are not typically eligible for a VNS procedure, including individuals with a history of brain damage, asthma or some other breathing problem, heartbeat irregularities, involuntary nervous system dysfunction, ulcers or a fainting disorder called vasovagal syncope. People with a single vagus nerve are also usually excluded as VNS candidates. In addition to these general exclusions, an individual with treatment-resistant depression typically won’t receive vagus nerve stimulation if he or she has suicide-related symptoms, or has a psychiatric history that includes schizophrenia, certain related psychotic conditions or bipolar disorder symptoms that shift rapidly between mania and depression.

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