The vagus nerve has the most extensive distribution of all the cranial nerves. It's actually two nerves, which both run from the brain stem and branch out through the neck and down each side of the body, across the abdomen and to the main organs.
As a result, the remarkably complex circuitry that makes up the entire vagus nerve has a role in myriad bodily functions, including breathing, maintaining digestive function, and monitoring the heart beat to keep it in a regular rhythm. When we're hungry or feel our chest tighten, it's the vagus nerve relaying that message. The vagus nerve also relays sensory information from the ear, tongue, throat, windpipe and voice box.
Like the nerve itself, vagus nerve disorders are often also called 10th cranial nerve disorders. These disorders can have a variety of different impacts that are as complex as the nerve itself, though some effects are more common than others.
For example, if the vagus nerve is stimulated, or if it is compressed, the result is usually clammy, cool skin, unconsciousness, and/or nausea. This is because when stimulated, the vagus nerve causes the heart to slow down and blood pressure levels to drop. While this might appear to be detrimental in many cases, the vagus nerve is sometimes stimulated to treat people suffering from severe depression or epilepsy [source: Tian].
What is vagus nerve stimulation?