Vagus Nerve Stimulation
The vagus nerve is one of 12 pairs of cranial nerves that run from the brainstem, through the neck, and down to the chest and abdomen. The longest of the cranial nerves, it is involved in sensory functions in the ears and tongue, as well as motor functions in the voice box, diaphragm, stomach and heart. The vagus nerve also is connected to both motor and sensory functions in the sinuses and esophagus, and is involved in areas of the brain that control mood, sleep and other functions.
Vagus nerve stimulation (VNS) is a brain stimulation therapy used to treat depression, epilepsy and other disorders. VNS works by sending mild pulses of electricity at regular intervals to the brain via the vagus nerve through a pulse generator. This device, which is about the size of a stopwatch, is surgically implanted in the upper left side of the chest. A lead wire connected to the generator is then threaded under the skin to the neck where it is attached to the vagus nerve on the left side.
The pulse generator typically is activated about two to four weeks following implantation1a. It is programmed at the doctor’s office using a hand-held computer, software and programming wand. The amount of stimulation varies according to the patient and can be adjusted over time. The device also can be temporarily deactivated by the patient by placing a magnet over the generator if side effects, such as hoarseness or coughing, become intolerable. The generator reactivates when the magnet is removed.
VNS was approved by the Food and Drug Administration as a seizure treatment for epilepsy. It may be recommended for patients who have tried two or more anti-epileptic drugs but not achieved adequate control of seizures, or for those who have not responded to medications and are not candidates for brain surgery1b. VNS is used in conjunction with anti-epilepsy drugs, not in place of them. It can take up to two years for VNS to have an effect on epilepsy seizures1b. If VNS is helpful, patients with epilepsy may then be able to gradually decrease their dosages of anti-epilepsy drugs.
The objective of undergoing VNS for epilepsy is to decrease the frequency, length and intensity of seizures, and potentially reduce the recovery time following a seizure.
While it is not successful in all people, it has been shown to:
- Decrease the severity or duration of seizures.
- Improve recovery following seizures.
- Enhance mood and sense of well-being.
- Improve attentiveness, memory and cognitive abilities.
- Decrease visits to the emergency room.
In addition to treating epilepsy, VNS also has been approved as a treatment option in certain circumstances for those with severe depression. Patients may be candidates for VNS if their severe or recurrent illness has lasted two years or longer, and if their depression has not responded to four or more other treatments2. However, VNS treatment for depression remains controversial since studies testing its effectiveness have produced mixed results.
VNS Implantation – fourth paragraph
1b http://www.aans.org/Patient%20Information/Conditions%20and%20Treatments/Vagus%20Nerve%20Stimulation.aspx
Epilepsy – first paragraph
http://www.nimh.nih.gov/health/topics/brain-stimulation-therapies/brain-stimulation-therapies.shtml
Vagus nerve stimulation – third paragraph
http://www.nimh.nih.gov/health/topics/brain-stimulation-therapies/brain-stimulation-therapies.shtml
General References
http://www.webmd.com/epilepsy/guide/vagus-nerve-stimulation-vns?print=true
http://www.mayoclinic.com/health/vagus-nerve-stimulation/MY00183
http://www.epilepsyfoundation.org/resources/medical/vagus-nerve-stimulation-therapy.cfm
http://emedicine.medscape.com/article/1186123-overview