“This is very big for the field,” said Dr. Nicholas Schiff, a professor of neurology and neuroscience at Weill Cornell Medical College in New York. “The understanding that, as the brain recovers, one in seven people could be conscious and aware, very much aware, of what’s being said about them, and that this applies every day, in every I.C.U. — it’s gigantic.” The finding, he added, “should change practice requirements around the world.”
Other doctors said it was still too early to predict the impact of the new technique. “This approach is not ready to be incorporated into standard practice at this time, as we are just not able to reliably predict outcomes early after injury,” said Dr. Flora Hammond, chair of physical medicine and rehabilitation at Indiana University School of Medicine.
In the new analysis, researchers at Columbia University and New York University tracked 104 unresponsive patients in Columbia’s neurological I.C.U., taking EEG recordings from each in the first few days after injury. The brain injuries had a variety of causes, including blows to the head, heart attack and internal bleeding. During each EEG recording, the researchers gave the patients instructions through headphones, including, “Begin opening and closing your right hand,” and “Stop opening and closing your right hand.”
The researchers fed the EEG data into a machine-learning algorithm, which compared the brain activity following each command to resting-state activity, looking for distinct and consistent differences — the chatter of motor signals, filtered from the background noise. And in 16 patients, hidden activity became evident. Previous research, in patients who had been unresponsive for years, had found that a subset showed hidden brain function. The new study is the first to use this approach to examine a large number of patients just after the injury.
“Somewhat to our surprise, we found that about 15 percent of patients who were not responding at all had this brain activation in response to the commands,” said Dr. Jan Claassen, medical director of the neurological I.C.U. at Columbia and the lead author of the paper. “It suggests that there’s some remnant of consciousness there. However, we don’t know if the patients really understood what we were saying. We only know the brain reacted.”
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