What is the vagus nerve?

The vagus nerve is the longest of 12 cranial nerves and extends from the brainstem through the chest to the abdomen on each side of the body. It functions as part of the involuntary nervous system that controls unconscious processes in the body, such as regulating heart rhythm, regulating breathing, and digesting food. 

Vasovagal syncope is one of the most common causes of fainting, which originates in the vagus nerve. The body overreacts to certain stimuli, which stimulates the vagus nerve and causes both blood pressure and heart rate to drop. For people who faint easily, such as at any sight of blood, vasovagal syncope is a common cause. In most cases, vasovagal syncope does note require treatment, but you should still consult your doctor if experiencing repeated fainting episodes. 

An overactive vagus nerve can also result in an abnormally low heart rate, or bradycardia. Individuals with an overactive vagus nerve that results in abnormally low heart rate may also be at risk for first-degree heart block. 

Since the vagus nerve operates many routine processes in the body, it’s not a nerve that many people are familiar with by name. In the medical community, however, the vagus nerve is well known and well studied, especially the topic of vagus nerve stimulation and its potential impact on many diseases. 

Vagus nerve stimulation has been used primarily to treat patients with epilepsy who haven’t responded to other treatments. Other studies include vagus nerve stimulation as a potential treatment for headaches, chronic pain, multiple sclerosis, and other diseases. 

In traditional vagus nerve stimulation, a device is implanted in the chest and a wire is connected to the left vagus nerve. The right vagus nerve contains fibers that supply nerves to the heart, so it is not used for vagus nerve stimulation typically. However, an implantable device to stimulate the right vagus nerve as a treatment of heart failure is currently being studied.  

If you experience fainting spells or an abnormally low heart rate, talk to your Oklahoma Heart Hospital physician about whether an overactive vagus nerve may be the cause.