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A quarter of patients left unresponsive after a severe brain injury can still perform cognitive tasks, a study suggests.
The syndrome known as cognitive motor dissociation (CMD) can happen when a person in a coma or vegetative state appears unresponsive, but still shows brain activity related to intentional thinking.
To detect if patients were following instructions, researchers analysed brain imaging scans called functional magnetic resonance imaging (fMRI), as well as a test that records the electrical activity in the brain, known as electroencephalography (EEG).
Examples of the commands used were “imagine opening and closing your hand” and “imagine playing tennis”.
These results bring up critical ethical, clinical, and scientific questions, such as how can we harness that unseen cognitive capacity to establish a system of communication and promote further recovery— Lead author Yelena Bodien
Using data from six sites across the UK, US and Europe, the study found cognitive motor dissociation was detected in 60 of the 241 patients.
Of the group, 11 had been assessed with fMRI, 13 with EEG only, and 36 with both techniques.
Lead author Yelena Bodien, an investigator for the Spaulding-Harvard Traumatic Brain Injury Model Systems and Massachusetts General Hospital’s Centre for Neurotechnology and Neurorecovery, in the US, said: “Some patients with severe brain injury do not appear to be processing their external world.
“However, when they are assessed with advanced techniques such as task-based fMRI and EEG, we can detect brain activity that suggests otherwise.
“These results bring up critical ethical, clinical, and scientific questions, such as how can we harness that unseen cognitive capacity to establish a system of communication and promote further recovery?”
I think we now have an ethical obligation to engage with these patients, to try to help them connect to the world— Nicholas Schiff, Weill Cornell Medicine
Nicholas Schiff, the Jerold B. Katz Professor of neurology and neuroscience at the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine, in the US, added: “We find that this kind of sharp dissociation of retained cognitive capabilities and no behavioural evidence of them is not uncommon.
“I think we now have an ethical obligation to engage with these patients, to try to help them connect to the world.
“What we need here is what we in our consortium have been trying to get started for 20 years: a sustained effort to benefit patients who have disorders of consciousness with systematic medical research, technology development, and better clinical infrastructure.”
Ms Bodien added: “Families have told us that once a positive test result revealing cognitive motor dissociation is shared with the patients’ clinical team, it can change the way that the team interacts with their loved one.
“Suddenly, the team is paying more attention to subtle behavioural signs that could be under volitional control, or speaking to the patient, or playing music in the room.
“On the other hand, failing to detect cognitive motor dissociation can have serious consequences, including premature withdrawal of life support, missed signs of awareness and lack of access to intensive rehabilitation.”
Researchers noted that a limitation of the study was that each patient was tested in their own way, which could lead to variability in the data.
Many of the patients included in the study were enrolled after their loved ones approached the research team.
Ms Bodien added: “To continue our progress in this field, we need to validate our tools and to develop approaches for systematically and pragmatically assessing unresponsive patients so that the testing is more accessible.
“We know that cognitive motor dissociation is not uncommon, but resources and infrastructure are required to optimise detection of this condition and provide adequate support to patients and their families.”
