Vagus Nerve Stimulation (VNS) therapy is a medical treatment that delivers mild electrical pulses to the vagus nerve. This therapy involves implanting a small device that sends signals to this nerve, a major pathway connecting the brain and various body organs. VNS is approved for treating specific forms of epilepsy and for individuals with depression that has not responded to other treatments.
What is VNS Therapy
VNS therapy involves a system with three main components: a pulse generator, a lead wire, and electrodes. The pulse generator is a small, battery-powered device typically implanted under the skin in the upper left chest, usually below the collarbone. A thin lead wire extends from this generator, threaded under the skin to the left side of the neck. There, its electrodes are wrapped around the left vagus nerve. The device is programmed to deliver regular, mild electrical pulses to the vagus nerve at set intervals throughout the day.
How VNS Affects Depression
The vagus nerve serves as a communication route between the brain and various parts of the body. When the VNS device stimulates the vagus nerve, it sends electrical impulses to the brainstem. These signals then disperse to different areas of the brain, influencing how brain cells function. This stimulation is believed to impact brain regions involved in mood regulation, such as the prefrontal cortex, anterior cingulate, and limbic system, which often show dysregulation in depression.
VNS may help normalize brain metabolism in these areas. The therapy is also thought to influence the release of neurotransmitters, like serotonin and norepinephrine, which play roles in mood and emotional responses. VNS may also increase blood flow in key brain areas and affect neural circuits linked to depressive symptoms.
Receiving VNS Implantation
VNS therapy is considered for individuals with treatment-resistant depression who have not found adequate relief from multiple prior therapies, such as various antidepressant medications or electroconvulsive therapy. The surgical procedure to implant the VNS device is performed under general anesthesia, typically taking one to two hours. It is often an outpatient procedure or may involve a short overnight hospital stay.
During surgery, two small incisions are made: one in the upper left chest for the pulse generator and another on the left side of the neck to access the vagus nerve. The generator is placed into a small pocket under the skin in the chest. The lead wire is then tunneled under the skin from the chest to the neck, where its electrodes are wrapped around the left vagus nerve. After the device is implanted and the incisions are closed, the VNS device is activated by a healthcare professional within two weeks. The stimulation settings are initially set at a low level and are gradually adjusted over several months to find the optimal therapeutic effect for each individual.
Living with VNS and Its Effects
After VNS implantation, patients typically experience a gradual onset of therapeutic effects, with noticeable improvements in depressive symptoms often taking several months to appear. A response, defined as a 50% reduction in symptom severity, may be observed in a significant percentage of patients after 3 to 12 months, with efficacy potentially increasing over time. Response rates have been reported to increase from around 37% at 3 months to 53% after one year in some studies.
Common side effects include voice changes or hoarseness, coughing, throat discomfort, or shortness of breath. These side effects are generally mild and often occur only when the stimulator is actively delivering pulses, typically diminishing over time as the body adjusts to the therapy. Ongoing monitoring and adjustments of the device settings by a healthcare provider are necessary to optimize treatment and manage any side effects. The device battery will eventually require replacement surgery, typically every five to ten years.