Vagus nerve stimulation is a medical procedure that delivers electrical impulses to the vagus nerve. Currently, it is used for some types of intractable epilepsy and depression that does not respond to the treatment. Some countries also allow its use for the treatment of chronic pain.
The vagus nerve is the tenth cranial nerve and arises from the medulla and carries both afferent and efferent fibers to regulate the function of various organs, glands, and involuntary muscles throughout the body.
The main functions where the vagus nerve is involved are speech vocalization, swallowing, heart rate and respiration. In addition, it also controls gastric secretion and intestinal motility.
The exact mechanism of how vagus nerve stimulation helps is not clear. The proposed mechanisms include an anti-inflammatory effect and changes in monoamines.
There is ongoing research going on possible uses of vagus nerve stimulation especially in the treatment of migraines and fibromyalgia.
Conventional stimulation required a surgically implanted device but new noninvasive vagus nerve stimulation devices that don’t require surgical implantation are being used.
Indications of Vagus nerve stimulation
Epilepsy
Vagal nerve stimulation can be considered as an option for treatment in cases where epilepsy has not fully responded to anti-epileptic drugs. The patient should be more than 4 years old and should have focal or partial epilepsy.
Depression
Similarly, the stimulation of vagus nerve can be used in depression which is resistant to drug treatment, counseling (psychotherapy) and electroconvulsive therapy.
This therapy is approved only for adults. Standard antiepileptic medicines should be continued.
Other Possible Indications in Future
Currently, the following conditions are being studied for treatment by vagus nerve stimulation
- Headaches
- Rheumatoid arthritis
- Inflammatory bowel disease
- Bipolar disorder
- Obesity
- Alzheimer’s disease.
Risks of Vagus Nerve Stimulation
Risks due to Surgical Procedure
- Incision site pain
- Infection
- Difficult swallowing
- Paralysis of the vocal cords
Effects due to vagus nerve stimulation
- Hoarseness
- Throat pain
- Cough
- Headaches
- Shortness of breath
- Difficulty in swallowing
- Paraesthesia
- Inability to sleep
Most of the side effects for most of the people are tolerable and fade in the majority of the cases. But these can bother some people as long as the implant is kept.
Overview of Procedure and Follow-up
The device consists of a matchbox side pulse generator that runs on a battery and lead wires which are connected to the vagus nerve on one side and pulse generator on the other side.
Implantation of the device is usually done as an out-patient procedure.
The pulse generator is surgically placed under the skin below the person’s collarbone. Lead wires from the generator are tunneled up to the patient’s neck and wrapped around the left vagus nerve at the carotid sheath through a second incision.
The left vagus is chosen for stimulation than right as the right vagus nerve plays a role in cardiac functions and stimulation could lead to negative effects on the heart.
The dose of the pulse administered can be adjusted via a magnetic wand for the current, frequency, pulse width, and duty cycle.
Transcutaneous vagus nerve stimulation involves wearable devices that do not require surgery and target auricular branch of the vagus nerve.
Prognosis
Vagus nerve does not entirely stop the seizures or make the patient drug free. Moreover, it can take months to years of stimulation to see a significant reduction in the frequency of the seizures.
Vagus nerve stimulation can also reduce recovery time after a seizure.
References
- Morris GL, Gloss D, Buchhalter J, et al. Evidence-based guideline update: Vagus nerve stimulation for the treatment of epilepsy. Neurology. 2013;81:1453–1459.
- De Ferrari GM, Crijns HJGM, Borggrefe M, et al. Chronic vagus nerve stimulation: A new and promising therapeutic approach for chronic heart failure. Eur Heart J. 2011;32:847–855.
- George MS, Rush AJ, Sackeim HA, Marangell LB. Vagus nerve stimulation (VNS): Utility in neuropsychiatric disorders. Int J Neuropsychopharmacol. 2003;6:73–83.
- Krahl SE, Senanayake SS, Pekary AE, Sattin A. Vagus nerve stimulation (VNS) is effective in a rat model of antidepressant action. J Psychiatr Res. 2004;38:237–240.