Some patients who appear unconscious know what’s going on

But one in four people with this kind of injury can perform cognitive tasks on command, according to a study published Wednesday in the New England Journal of Medicine. The responses were detected with brain scans that show the patients are conscious but have no motor control.

The findings could influence decisions about whether to continue life support or how caregivers interact with patients who appear unconscious but might be aware of what’s happening around them.

“Knowing someone has more capacity for thinking than they appear to have, the family might read to them more or play music," said Yelena G. Bodien, first author of the study and an investigator for the Spaulding-Harvard Traumatic Brain Injury Model Systems and Massachusetts General Hospital’s Center for Neurotechnology and Neurorecovery. 

“Nurses might talk to them more or be more likely to turn on the TV to give them some stimulation. A clinician or therapist might be more likely to look for signs of behavior that might go undetected."

The precise number of Americans with severe brain injuries who appear unresponsive is uncertain because until recently there was no diagnostic code for the conditions in the International Classification of Diseases system. 

An estimate based on available data suggests the number is around 100,000, according to Nicholas Schiff, a professor of neurology and neuroscience at Weill Cornell Medicine and the study’s senior corresponding author.

The study was funded by a $10 million grant from the James S. McDonnell Foundation that established an international consortium to explore the recovery of consciousness after brain injuries.

Participating researchers at six academic medical centers in the U.S., U.K. and Europe examined 353 adults with brain injuries who were recruited from medical facilities and surrounding communities. The multiphase study spanned nearly two decades from 2006, when the first patients were enrolled, to 2023.

Previous research has shown that some patients with brain injuries who appear to be unconscious can perform cognitive tasks, but this is the first study to systematically examine a large cohort with what are known as “disorders of consciousness."

Patients included in the study were adults ages 18 and older. Approximately 61% were male and 39% female. Their brain injuries were caused by accidents or medical conditions such as stroke or cardiac arrest.

The group included 241 patients with different levels of disorders of consciousness who were physically unresponsive to verbal commands issued bedside. The remaining 112 patients had similarly severe brain injuries but showed a physical response to verbal commands.

The study was done in two phases. Patients were first assessed on a range of neurological functions, including auditory and motor skills. They might, for example, have been asked to respond to questions by making a thumbs-up gesture.

In addition, patients were tested with functional MRI or electroencephalogram—scans that can detect brain activity as a person is acting or thinking. While undergoing fMRI or EEG, patients were asked to think about an activity, such as opening and closing a hand. Then they were told to rest, a sequence repeated multiple times.

“The test is something you can do at home," Schiff said. “You get a stopwatch and hit go with the instruction in your head to imagine playing tennis at the U.S. Open. When it hits 30 seconds, you stop. You rest for 30 seconds. You do this seven more times."

Of the 241 patients who didn’t show a physical response to bedside prompts, 60—or 25%—accurately followed the instructions in the cognitive test, according to the fMRI and EEG data.

“It’s a little higher than we expected," Schiff said. “It means there’s a lot of work to do. We can help some people out there."

In comparison, 43 of the 112 patients who showed a physical response to verbal commands successfully completed the cognitive test, or 38%.

While encouraging, the findings also raise moral and ethical questions about patient rights.

“This information needs to be incorporated in decisions about the use of life-sustaining treatment, goals of care and clinical management," said Robert D. Truog, a professor of medical ethics, anesthesia and pediatrics at Harvard Medical School and Boston Children’s Hospital who wasn’t involved with the study. “But it would also be important to know if these patients want to keep on living this way. I don’t think it’s obvious that everyone would."

The study had several limitations. Each site conducted the research according to its own protocols. Participants included patients whose families had heard about the study and asked to enroll their eligible family member. And patients living near an academic medical center might already have had a high level of care. For these reasons, the rate of “covert cognition" might differ in the general population.

The time and expense involved in the study makes it unlikely it will be repeated soon, and, practically speaking, few patients will have access to the tests used in the study.

“I pasted a couple of pictures on my wall to remind me that we can’t forget about these people," Schiff said. “It has been sufficiently demonstrated that it’s a generalizable phenomenon, whatever the rate. We’ve got to deal with it."