Brain-damaged patients who are unresponsive may have some awareness

When people suffer a severe brain injury—for example, from a car accident, a fall, or an aneurysm—they can fall into a coma for weeks, with their eyes closed and their body unresponsive.

Some recover, but others enter a mysterious state: eyes open but no clear signs of consciousness. Hundreds of thousands of such patients in the United States alone are diagnosed in a vegetative state or as minimally conscious. They can go decades without regaining a connection to the outside world.

These patients pose a painful conundrum for both their families and the medical professionals who care for them. Even if they can’t communicate, can they still be conscious?

Substantial test published on Wednesday indicate that a quarter of them do.

Teams of neurologists from six research centers asked 241 unresponsive patients to spend several minutes at a time performing complicated cognitive tasks, such as imagining a game of tennis. Twenty-five percent of them responded with the same patterns of brain activity seen in hearty people, suggesting they were able to think and were at least somewhat conscious.

Dr. Nicholas Schiff, a neurologist at Weill Cornell Medicine and an author of the study, said research shows that up to 100,000 patients in the U.S. alone may retain some level of consciousness despite suffering grave injuries.

The results should lead to more advanced studies of people with so-called disorders of consciousness and further research into how these patients might communicate with the outside world, he said: “It’s not OK to know about it and do nothing.”

When people lose consciousness after a brain injury, neurologists traditionally diagnose them with a bedside exam. They might ask patients to speak, look left or right, or give a thumbs-up.

A patient who does not respond at all may be diagnosed as being in a vegetative state. A patient who produces only fleeting responses may be diagnosed as minimally conscious.

Beginning in the tardy 1990s, Dr. Schiff and his colleagues performed detailed scans of the brains of some patients with impaired consciousness. While many of them turned out to have massive damage, others had surprisingly immense areas of intact tissue.

Neurologists wondered if at least some patients were still “in there” — and they simply couldn’t tell anyone.

Several research teams began looking for signs of consciousness. First, they used a technique called functional magnetic resonance imaging to track blood flow through the brain.

In a 2006 study, Adrian Owen, then of the Medical Research Council Cognition and Brain Sciences Unit in Cambridge, England, and his colleagues asked a woman diagnosed with a vegetative state to imagine she was playing tennis.

Areas of her brain lit up in response, imaging scans showed. They were the same areas that lightweight up in undamaged brains.

Early studies left neuroscientists wondering whether such a condition—which Dr. Schiff calls cognitive-motor dissociation—was sporadic. The only way to find out was to conduct a immense study.

Six groups of experts, including Dr. Owen’s and Dr. Schiff’s teams, began collaborating on the study in 2008. To speed it up, they figured out how to record brain activity in patients wearing a cap covered with electrodes. It’s much easier to exploit electrodes to study patients at the bedside than to wheel them into a brain scanner.

Despite this progress, the work was tardy going. The researchers had to get permission from the patients’ families to study them, and then they had to run a standard battery of tests.

To make sure they weren’t fooled by false signals, the researchers tried having the patients perform cognitive tasks for several minutes.

The researchers studied 241 patients who were unresponsive to commands during the customary test. Hearty volunteers also performed the same tasks. The researchers then gave the data to a team of statisticians at the Icahn School of Medicine at Mount Sinai. The team conducted the analysis without knowing which results came from which study group.

Their analysis found that 60 of the patients showed signs of consciousness on functional MRI scans, electrode recordings, or both. The results were published in The Modern England Journal of Medicine.

Dr. Schiff said the results may be biased by the fact that he and his colleagues studied patients an average of eight months after their injuries. Those who survived that long may be more resilient than those who died sooner. And that resilience may have made them more likely to remain conscious.

On the other hand, Dr. Schiff argued, the testing was so demanding that some patients with some awareness probably did not test positive. “We’re probably going to lose people,” he said.

Dr. James Bernat, a neurologist at the Geisel School of Medicine at Dartmouth, who was not involved in the study, said it offers a definitive picture of cognitive-motor dissociation.

“This is without a doubt the largest study ever done” on these patients, he said. “It’s being done by the best people in the best places, so we’re not going to see a better study anytime soon.”

It is possible that people with consciousness disorders may one day benefit from brain implants that have been developed to facilitate people with other conditions communicate.

On Wednesday, another research team reported that a patient paralyzed by amyotrophic lateral sclerosis, known as Lou Gehrig’s disease, was able to communicate through a brain implant after just 30 minutes of training.

Dr. Schiff suspects that some people who suffer from cognitive-motor dissociation will likely be able to cope with these implants.

“We have tens of thousands of people like that,” he said. “We should do something about it.”