Healthcare (Commonwealth Union) – Finding from a global study co-led by investigators from Weill Cornell Medicine and NewYork-Presbyterian have revealed that in an unexpected development, patients with severe brain injuries often exhibit clear signs of cognitive activity on brain scans when asked to perform complex mental tasks, even if they are unable to move or speak.
Published on August 14 in the New England Journal of Medicine, this research represents the largest examination of cognitive-motor dissociation, a condition where cognitive function appears to be preserved despite severe motor impairment. The study, involving 241 patients in comas or vegetative states who could not respond visibly to commands, found that about 25 percent of them showed sustained cognitive activity on electroencephalography (EEG) or functional magnetic resonance imaging (fMRI) scans. Testing was conducted with consent from surrogates at six academic medical centers, part of a broader consortium involved in the research.
“We find that this kind of sharp dissociation of retained cognitive capabilities and no behavioral evidence of them is not uncommon,” stated the study corresponding author Dr. Nicholas Schiff, the Jerold B. Katz Professor of Neurology and Neuroscience in the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine, who is a neurologist at NewYork-Presbyterian/Weill Cornell Medical Center as well as the administrative lead of the consortium. “I think we now have an ethical obligation to engage with these patients, to try to help them connect to the world.”
Patients in the study were assessed at NewYork-Presbyterian/Weill Cornell Medical Center, NewYork-Presbyterian/Columbia University Irving Medical Center, The Rockefeller University Hospital, and Massachusetts General Hospital in the U.S., as well as at medical centers affiliated with the University of Cambridge, the University of Liege, and the University of Paris. The Icahn School of Medicine at Mount Sinai acted as the central hub for the study and performed the statistical analysis of the patient data.
Researchers indicated that cognitive-motor dissociation is believed to be similar to the well-known “locked-in” syndrome, where an otherwise functional brain is isolated, typically due to strokes or degeneration of motor neurons as seen in amyotrophic lateral sclerosis. This condition is also observed in patients with extensive brain damage who appear largely or completely unaware of their environment.
For the study, researchers included 353 adults with “disorders of consciousness,” often resulting from severe traumatic brain injuries or interruptions in oxygen supply to the brain due to strokes or heart attacks. Most participants were receiving care at home or in long-term care facilities, with a median time since injury of approximately eight months.
The researchers repeatedly asked each patient to perform a series of continuous motor tasks (e.g., “keep wiggling your toes”) and motor-related cognitive tasks (“keep imagining wiggling your toes”) in multiple sessions of 15 to 30 seconds each, separated by equal rest periods. The protocols used were carefully designed and validated to minimize the risk of false positives.
Out of the 241 patients who were unable to follow commands at the bedside, 25% were able to complete cognitive tasks that involved matching patterns of brain activity, as measured by EEG and/or fMRI, similar to those observed in healthy individuals responding to the same commands.
In contrast, a larger percentage (38%) of the 112 patients who showed motor responses to spoken commands at the bedside successfully performed these cognitive tasks. However, most of these patient controls did not exhibit cognitive performance. This further separation highlights that the mental imagery tasks measured by fMRI and EEG require sustained cognitive resources, such as short-term memory, that are not needed for following bedside commands or basic communication. The fact that a quarter of the motor-unresponsive patients with cognitive-motor dissociation completed these tasks suggests that many patients who appear unconscious might actually be aware and capable of cognitive function, the researchers noted.
Having greater insights to brain injury patients and possible coma recovery stages may help a neuroscientist focused on recovery pursue research with greater information. Hence the findings will likely provide valuable information.
