Deep brain stimulation with electrical pulses may offer hope for patients trapped in a minimally conscious state.
The electrodes were placed at specific points in the brain
Treatment of a 38-year-old man with a severe brain injury enabled him to use words and gestures, chew and swallow and drink from a cup, say US doctors.
Before the stimulation, done through electrodes implanted in his brain, he could only make slight eye or finger movements, the team report in Nature.
Experts said more studies were needed to assess which patients may benefit.
Deep brain stimulation is already used in the treatment of tremors associated with Parkinson's disease.
The procedure involves electrodes implanted with millimetre accuracy to specific areas of the brain.
The man involved in the study was badly beaten six years ago, leaving him severely brain injured and in a minimally conscious state, in which patients show intermittent signs of awareness.
Over a period of six months the researchers alternated periods of electrical stimulation with fake stimulation to assess whether it was having an effect.
Within 48 hours of the first stimulation, the patient was able to keep his eyes open, turn his head, and utter words.
After several treatments he is now able to perform complex tasks such as brushing his hair, although with difficulty due to severe immobility caused by his condition.
And he can chew and swallow his food where before he needed a feeding tube.
Further tests on 12 patients have gained FDA approval. The researchers say if these results are replicated, it could change the standard of care for such patients, most of whom have to be cared for in long-term nursing facilities.
Dr Ali Rezai, the neurosurgeon at Cleveland Clinic's Center for Neurological Restoration who carried out the procedure said the changes in the man had been "remarkable and sustained".
Study leader, Dr Nicholas Schiff, associate professor of neurology and neuroscience at Weill Cornell added: "The work challenges the existing practice of early treatment discontinuation and also changes the approach to assessment and evaluation."
His mother, who does not wish to be identified said it had been very hard for her to see her son lying in the nursing home, unable to communicate with them.
"I'll never forget the words the doctor said to us: 'if your son recovers from this in the next 72 hours, and we don't know if he will, he will be a vegetable for the rest of his life.'
"Now, my son can eat, express himself and let us know if he is in pain. He enjoys a quality of life we never thought possible.
"And the most important part is he can say 'I love you mommy'."
Professor Paul Matthews, an expert in clinical neurosciences at Imperial College London, said the study offered hope.
"The causes and severity of brain injury vary between minimally conscious state patients," he said.
"More experience with the approach is needed to understand which patients may be expected to benefit."
Professor Tipu Aziz, expert in neurosurgery at the University of Oxford, added there had been cases of patients recovering spontaneously after being in a minimally conscious state for a long time and no firm conclusions could be made.
"Much more needs to be done into the research of the best management of such patients but there is little funding to do so."