Vagus nerve stimulation is already used to help people with epilepsy and depression. This cranial nerve runs from the brain to other parts of the body, including the heart, lungs and gut; vagus means "wandering" in Latin.
The study results challenge ideas that consciousness disorders lasting longer than 12 months are irreversible, the researchers believe.
Vagus nerve activity is "important for arousal, alertness and the fight-or-flight response," wrote Dr. Angela Sirigu in an email. She is an author of the study and neuroscientist at the Institut des Sciences Cognitives Marc Jeannerod in Lyon, France.
Sirigu and her colleagues decided to test the ability of vagus nerve stimulation to restore consciousness in a patient in a vegetative state. Patients in a vegetative state show no evidence of consciousness, mental function or motor function. Unlike a coma, a vegetative state
includes intermittent periods of eye opening; this seemingly hopeful sign, though, is not a normal waking, just a random physiological occurrence.
Vagus nerve stimulation begins with a surgeon implanting a device in the chest and threading a wire under the skin. This wire joins the vagus nerve and the device, which sends electrical signals along the nerve to the brain stem (where the spinal cord and brain connect) and in turn this transmits impulses to certain areas in the brain.
Stimulating the vagus nerve activates "a natural physiological mechanism," wrote Sirigu in an email.
Sirigu and her colleagues selected the man, who had been in a vegetative state for 15 years "showing no sign of change since his car accident," she wrote. "We therefore put ourselves in a difficult challenge by selecting a patient with the worst outcome."
The reason for that choice is that if any changes occurred in the patient after vagus nerve stimulation, then "these could not be the result of chance," she added.
After a single month of stimulation, the patient's attention, movements and brain activity signifi