"Hidden Consciousness" Offers Hope for Unresponsive Victims of Brain Trauma

"This raises the possibility of some preservation of consciousness." 

brain, consciousness

Within the first few days of a traumatic brain injury, doctors and families are forced to make crucial decisions about the health of a patient — even when they’re showing no signs of waking up. But within just four days of injury, there are ways to detect “hidden consciousness,” suggests a team of scientists at the Columbia University Medical Center. If it’s there, it could be a very good sign.

When a patient is in a coma or other vegetative state, there’s a few ways to search for consciousness, even if the patient isn’t able to directly communicate. One of these methods is to ask the patient to perform basic commands, like opening or closing fingers while taking an MRI of their brain. Another method, demonstrated in a paper published Wednesday in the New England Journal of Medicine is to use electroencephalography (EEG) in conjunction with a new machine learning algorithm trained to hunt for clues.

When neurologist Jan Claassen, M.D.,Ph.D. and his team applied this technique to 104 unresponsive patients, they picked up tiny echoes of consciousness in 15 percent of them. Those signs of “hidden consciousness” could be strong indicators that these patients will recover, if given enough time.

“Many patients in the ICU do not show movements on commands, and this is then interpreted as unconsciousness,” Claassen tells Inverse. “Some of these patients have brain activation in response to those same commands. This raises the possibility of some preservation of consciousness.”

What the Algorithm Is Looking For

Claassen’s team’s work is based on an algorithm that looks for a unique neural signature denoting cognitive-motor dissociation. It searches for evidence that someone can recognize a verbal command but can’t translate that command into a physical action that allows an outsider to know they’re still conscious. A 2016 analysis estimated that this is the case in 15 percent of chronically unresponsive patients, based on data obtained months or years after the injury.

human brain on white background

Right now, Claassen notes that these signs of consciousness are usually found using MRI images or EEG. His algorithm opts for the EEG method and is intended for use at bedside in the early days of injury, when critical decisions need to be made quickly.

“EEG is an attractive approach as the patient does not have to leave the ICU to be tested,” he explains. “In very sick patients, every transport out of the ICU needs to be justified.”

Knowing the status of a patient’s internal life can help determine whether to transfer them, but it can also help inform families who have to make serious decisions about continuing or ending care. In the paper, they note that responsiveness during the period right after injury “may have an effect on decisions regarding the withdrawal of life-sustaining therapies.”

In other words, signs of consciousness in that early period can influence whether families decide to keep a loved one on life support or not.

Signs of Hidden Consciousness

To test the algorithm, Claassen and his team gave verbal commands to 104 unresponsive patients who had sustained brain injuries within the last three to 10 days. After a median of four days of monitoring, the algorithm found a unique signature suggesting that 15 percent of patients (16 people) were registering the commands but unable to physically respond.

Those signals turned out to be a good sign for how well the patients recovered from their injuries. Fifty percent of those patients had progressed to actually responding physically to the commands before they were discharged from the hospital. A year later, 44 percent of patients that had showed signs of hidden consciousness could function independently for eight hours per day.

Importantly, patients who didn’t show signs of hidden consciousness early on still recovered — they just showed less robust, less rapid signs of recovery than those who did show early signs of consciousness. A year later, 14 percent of the patients who didn’t show signs of hidden consciousness early on were able to function for eight hours per day.

That, says Claassen, suggests early signs of consciousness could be a good early indicator for how serious a brain injury will turn out to be.

“We do not know if patients completely understand the commands, but it likely reflects less extensive injury and is associated with recovery,” Claassen says.

Still, Claassen notes that this study is small. His group is testing the idea out at other medical centers, and in patients with different types of brain injuries. But the hope is that his method, given further testing, could become a standard part of clinical practice.

If his results pan out, it could be a good sign for those who are secretly clinging to consciousness. If the signs are there, it might just take the right algorithm to find them.

Abstract:

Background: Brain activation in response to spoken motor commands can be detected by electroencephalography (EEG) in clinically unresponsive patients. The prevalence and prognostic importance of a dissociation between commanded motor behavior and brain activation in the first few days after brain injury are not well understood.

Methods: We studied a prospective, consecutive series of patients in a single intensive care unit who had acute brain injury from a variety of causes and who were unresponsive to spoken commands, including some patients with the ability to localize painful stimuli or to fixate on or track visual stimuli. Machine learning was applied to EEG recordings to detect brain activation in response to commands that patients move their hands. The functional outcome at 12 months was determined with the Glasgow Outcome Scale–Extended (GOS-E; levels range from 1 to 8, with higher levels indicating better outcomes).

Results: A total of 16 of 104 unresponsive patients (15%) had brain activation detected by EEG at a median of 4 days after injury. The condition in 8 of these 16 patients (50%) and in 23 of 88 patients (26%) without brain activation improved such that they were able to follow commands before discharge. At 12 months, 7 of 16 patients (44%) with brain activation and 12 of 84 patients (14%) without brain activation had a GOS-E level of 4 or higher, denoting the ability to function independently for 8 hours (odds ratio, 4.6; 95% confidence interval, 1.2 to 17.1).

Conclusion: A dissociation between the absence of behavioral responses to motor commands and the evidence of brain activation in response to these commands in EEG recordings was found in 15% of patients in a consecutive series of patients with acute brain injury. (Supported by the Dana Foundation and the James S. McDonnell Foundation.)