In a rare instance, a 35-year-old man in France who had been in a vegetative state for 15 years has shown signs of consciousness for the first time after neurosurgeons administered a nerve stimulation therapy.
The findings reported in the journal Current Biology showed that vagus nerve stimulation (VNS) -- a treatment already in use for epilepsy and depression -- can help to restore consciousness even after many years in a vegetative state.
The outcome challenges the general belief that disorders of consciousness that persist for longer than 12 months are irreversible, the researchers said.
A vegetative state is when a person is awake but is showing no signs of awareness. A person is considered to be in a permanent vegetative state when it has been more than six months if caused by a non-traumatic brain injury, or more than 12 months if caused by a traumatic brain injury, according to the UK's National Health Service (NHS).
By stimulating the vagus nerve, "it is possible to improve a patient's presence in the world", said Angela Sirigu of Institut des Sciences Cognitives Marc Jeannerod in Lyon, France.
The vagus nerve connects the brain to many other parts of the body, including the gut.
It is known to be important in waking, alertness, and many other essential functions.
To test the ability of VNS to restore consciousness, the researchers wanted to select a difficult case to ensure that any improvements could not be explained by chance.
They looked to a patient who had been lying in a vegetative state for more than a decade with no sign of improvement.
After one month of vagal nerve stimulation, the patient's attention, movements and brain activity significantly improved, the researchers said.
The man began responding to simple orders that had been impossible before. For example, he could follow an object with his eyes and turn his head upon request.
His mother reported an improved ability to stay awake when listening to his therapist reading a book.
After stimulation, the researchers also observed responses to "threat" that had been absent.
For instance, when the examiner's head suddenly approached the patient's face, he reacted with surprise by opening his eyes wide.
After many years in a vegetative state, he had entered a state of minimal consciousness.
Recordings of brain activity also revealed major changes.
The researchers said they are now planning a large collaborative study to confirm and extend the therapeutic potential of VNS for patients in a vegetative or minimally conscious state.
In addition to helping patients, the findings will also advance understanding of "this fascinating capacity of our mind to produce conscious experience", Sirigu said.
