When people suffer severe brain damage — for example, as a result of car accidents, falls or aneurysms — they can fall into a coma for weeks, with their eyes closed and their bodies unresponsive.
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Some recover, but others enter a mysterious state: their eyes open but with no clear signs of consciousness. Hundreds of thousands of such patients in the United States alone are diagnosed as being in a vegetative state or minimally conscious. They can survive for decades without regaining a connection to the outside world.
These patients pose an agonizing mystery. Could they still be conscious? A large study recently published in The New England Journal of Medicine suggests that a quarter of them are.
Neurologists at six research centers asked 241 unresponsive patients to spend several minutes at a time performing complex cognitive tasks, such as imagining themselves playing tennis. Twenty-five percent of them responded with the same patterns of brain activity seen in healthy people, suggesting they were capable of thinking and were at least somewhat conscious.
Nicholas Schiff, a neurologist at Weill Cornell Medicine in New York City and an author of the study, said it shows that as many as 100,000 patients in the United States alone may have some level of consciousness despite their devastating injuries.
The findings should lead to more sophisticated testing of people with so-called disorders of consciousness and more research into how such patients might communicate, he said: “It’s not okay to know this and do nothing.”
When people lose consciousness after a brain injury, neurologists traditionally diagnose them with a bedside exam. They may ask patients to say something, look left or right, or give a thumbs-up. An unresponsive patient might be diagnosed as being in a vegetative state. A patient who makes only fleeting responses might be diagnosed as minimally conscious.
Beginning in the late 1990s, Schiff and his colleagues performed detailed brain scans of patients with disorders of consciousness. While many had massive damage, others had surprisingly large swaths of intact tissue. Neurologists wondered whether at least some of the patients were still “in there” — and simply couldn’t tell anyone about it.
In a 2006 study, Adrian Owen, then at the Medical Research Council’s Cognitive and Brain Sciences Unit in Cambridge, England, and his colleagues asked a woman diagnosed as being in a vegetative state to imagine playing tennis. In response, regions of her brain became active — the same regions that are activated in undamaged brains.
Early studies left neurologists wondering whether the condition — which Schiff calls cognitive-motor dissociation — was rare.
The experts began collaborating on a study in 2008. They tested 241 patients who did not respond to commands during a traditional exam. They also had healthy volunteers perform the same tasks.
Their analysis revealed that 60 patients showed signs of consciousness on functional MRIs, electrode recordings, or both.
Another team of researchers recently reported that a patient paralyzed by amyotrophic lateral sclerosis, known as Lou Gehrig’s disease, was able to communicate through a brain implant after 30 minutes of training.
Schiff suspects that some people with cognitive-motor dissociation will likely be able to master these implants.
“We have tens of thousands of people like that,” he said. “We should do something about it.”
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