Vagus nerve stimulation (VNS) has been approved as an add-on therapy for epilepsy by the U.S. Food and Drug Administration in adults and children ages four and older.
What is VNS?
Dravet syndrome is a rare and severe type of epilepsy that begins in infancy. Symptoms, which include seizures accompanied by fever, start in the first year of life. These seizures are thought to be caused by overactive signaling in the brain.
The vagus nerve runs from the base of the brain to the chest and abdomen, with one branch running on each side of the body.
In vagus nerve stimulation, a device is surgically implanted into the chest like a pacemaker. A wire from the device is wrapped around the left vagus nerve. When activated, the device sends an electrical signal from the vagus nerve to the brain. Stimulation by the device is thought to regulate signaling in the brain, reducing the overactive signaling that causes seizures.
A recent review published in the scientific journal Seizure summarized the findings of several studies of VNS therapy in patients with Dravet syndrome. Of 68 patients, about 53 percent showed at least a 50 percent reduction in seizures in response to treatment.
The procedure to implant the VNS device usually takes one to two hours. It may be performed by numbing only the area where the device will be implanted, or under general anesthesia, which usually requires an overnight hospital stay.
A small incision is made near the left collarbone to implant the device, which is about the size of a stopwatch. A second small incision is made on the neck, to connect the device to the vagus nerve.
The device is turned on a few weeks after surgery. It is programmed to deliver electrical stimulation to the vagus nerve at various times and with various intensities. The simulation usually begins at a low level and is increased based on symptoms and effectiveness.
Patients are also given a magnet, which they or their caregivers can use to activate the VNS device if they sense the start of a seizure. Additional stimulation at the beginning of a seizure may reduce the severity and length of the episode.
The side effects of VNS are usually mild and may include a sore throat, coughing, difficulty swallowing, or hoarseness when speaking.
Not everyone will respond to VNS therapy. If no improvement is seen after two years, the device may be switched off or removed.
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