He emerged from the car accident alive but alone, there and not there: a young man whose eyes opened yet whose brain seemed shut down. For five years, he lay mute and immobile beneath a diagnosis — “vegetative state” — that all but ruled out the possibility of thought, much less recovery.

But in recent months at a clinic in Liege, Belgium, the patient, now 29, showed traces of brain activity in response to commands from doctors. Now, according to a new report, he has begun to communicate: In response to simple questions, like “Do you have any brothers?” he showed distinct traces of activity on a brain imaging machine that represented either “yes” or “no.”

Experts said Wednesday that the finding could alter the way some severe head injuries were diagnosed — and could raise troubling ethical questions about whether to consult severely disabled patients on their care.

The new report, posted online by The New England Journal of Medicine, does not suggest that most apparently unresponsive patients can communicate or are likely to recover.

The hidden ability displayed by the young accident victim is rare, the study suggested.

Nor does the finding apply to victims of severe oxygen depletion, like Terri Schiavo, the Florida woman who became unresponsive after her heart stopped and was taken off life support in 2005 during an explosive controversy over patients’ rights.

Moreover, experts said the new test was not ready for wide use as a diagnostic tool; serious technical challenges remain to be worked out.

Still, the experts agreed that the new study exposed the limits of the current bedside test for diagnosing mental state: checking whether patients’ eyes can track objects, and carefully looking for any signs — eye blinks, finger twitches — in response to questions or commands.

In the new paper, Belgian and English researchers studied 54 patients living in states of persistent unconsciousness. Of these, 23 had a diagnosis of “vegetative state,” meaning they were not able to signal any response to commands or questions.

In 2006, the same research group reported that one of the 23 “vegetative” patients showed on imaging tests that her brain was responding to commands. When doctors asked her to think of playing tennis, areas of her motor cortex leapt to life. When asked to think of being in her house, spatial areas in the brain became active.

In the current experiment, the researchers found that three other patients showed similar responses. To open a channel of communication, they instructed one of them, the 29-year-old man, to associate thoughts about tennis with “yes” and thoughts about being in his house with “no.”

They then asked questions, repeating the procedure numerous times, switching the associations — tennis with yes, then with no — to make sure the patient was in fact making conscious choices.

“We asked basic biographical questions, like ‘Is your father’s name Thomas?’ and ‘Have you ever been to the United States?’” said Adrian Owen, a neuroscientist at the Medical Research Council in Cambridge, England, who developed the method and was a co-author of the paper. “We then checked whether the answers were correct. They were.”

Findings raise troubling issues, some experts say

Some neurologists cautioned that new findings on severe brain injuries might further confound troubled families.

In an editorial accompanying the new report in The New England Journal of Medicine, Harvard University neurologist Allan Ropper wrote: “It will now be difficult for physicians to tell families confidently that their unresponsive loved ones are not ‘in there somewhere.’” Even where a patient has shown purposeful brain response, “we cannot be certain whether we are interacting with a sentient, much less competent, person.”

Bioethicist Arthur Caplan said the study will complicate decisions about sustaining life. “The more these measures of consciousness get complex and fine-tuned, the harder it is to write a recipe about them” he said.

— Los Angeles Times