Fluorodeoxyglucose FDG-PET images acquired during baseline (on the left, pre-VNS) and 3 months post vagus nerve stimulation (on the right, post-VNS). After vagus nerve stimulation, the metabolism increased in the right parieto-occipital cortex, thalamus and striatum. Photo: Corazzol et al/PA Wire

A 35-year-old man who had been in a vegetative state for 15 years is showing signs of consciousness after receiving a pioneering treatment based on nerve stimulation.

In the month since a vagus nerve stimulator was put into his chest, the man, who was injured in a car accident, has begun responding to simple orders that had been impossible before.

The findings reported in Current Biology may help to show that by stimulating the vagus nerve "it is possible to improve a patient's presence in the world", according to lead researcher Angela Sirigu of Institut des Sciences Cognitives Marc Jeannerod in Lyon, France.

The researchers say it may challenge the view that a vegetative state which lasts for more than 12 months is irreversible.

"Other scientists have hailed it as "a potentially very exciting finding" but have also urged caution.

After treatment, it was reported the patient could follow an object with his eyes, turn his head on request and his mother said there was an improved ability to stay awake when listening to his therapist reading a book.

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.

The patient, who was picked because he had been lying in a vegetative state for more than a decade with no sign of improvement, also appeared to react to a "threat".

Researchers spotted that he reacted with surprise by opening his eyes wide when the examiner's head suddenly approached his face.

Changes in brain activity may show that he had shifted from being in a vegetative state to being a state of minimal consciousness.

An important signal in distinguishing between these conditions increased significantly in areas of the brain involved in movement, sensation, and awareness, according to the scientists.

Gains were also spotted in the brain's functional connectivity, metabolic activity in both cortical and subcortical regions of the brain.

The researchers are now planning a large collaborative study.

Dr Tom Manly of Cambridge University's MRC Cognition and Brain Sciences Unit, described it as a "potentially very exciting finding".

He added: "It is very important to take into account that the patient moved from a vegetative to a minimally conscious state. That is, consciousness remains severely altered but, in contrast to the vegetative state, there is minimal but definite behavioural evidence of self or environmental awareness.

"The finding is therefore in my view an exciting preliminary indication that prolonged intervention could produce benefits that further work will no doubt address.

"In my view it would be fair to say that this treatment could potentially restore consciousness in some patients in a vegetative state, rather than that it can."

Roland Jones, professor in neuropharmacology at the University of Bath, said: "These results need to be repeated in other patients with long-term vegetative conditions to confirm the findings.

"If they can be, this treatment could complement a growing range of pharmacological approaches (eg: low doses of the anti-anxiety drug, zolpidem) that have been shown to partially reverse vegetative states and restore both motor and cognitive function in some cases."

PA Media