Recent research co-led by specialists at Mass General Brigham reveals that brain imaging can identify signs of consciousness in some brain-injured patients who appear unresponsive.
The study involved 241 participants with severe brain injuries who did not react to simple commands. These individuals were evaluated using functional MRI (fMRI), electroencephalography (EEG), or both techniques while responding to instructions like “imagine opening and closing your hand.” Following the command, subjects heard, “stop imagining opening and closing your hand” after 15-30 seconds. The results indicated that 25% of the participants—60 in total—were covertly following these commands over different time frames. Researchers noted that these individuals exhibited a phenomenon known as cognitive motor dissociation, suggesting they can understand language, remember instructions, and maintain focus even though they seem unresponsive. This indicates their cognitive capabilities surpass their ability to move.
“Some patients with severe brain injury appear not to process their surrounding environment. Yet, advanced methods like task-driven fMRI and EEG allow us to detect brain activity that implies otherwise,” explained lead author Yelena Bodien, PhD, an investigator in the Spaulding-Harvard Traumatic Brain Injury Model Systems and the Center for Neurotechnology and Neurorecovery at Massachusetts General Hospital. “These findings raise essential ethical, clinical, and scientific inquiries—like how we can tap into this hidden cognitive potential to create a communication system and encourage further recovery?”
Following a significant brain injury, individuals may end up with various consciousness disorders, including coma, vegetative states, or minimally conscious states. Since the first evidence of cognitive motor dissociation in patients with such disorders emerged nearly two decades ago, global centers have reported this condition occurring in about 15% to 20% of unresponsive patients. However, the current study suggests that this could be observed in 25% or potentially more. Cognitive motor dissociation was predominantly found in participants evaluated through both fMRI and EEG, indicating that using different testing methods may help ensure consciousness is accurately detected.
Data for this study was collected over approximately 15 years from participants across six sites in the United States, United Kingdom, and Europe. Each location developed and rigorously validated their techniques to minimize any chances of misleading positive results. Some participants were recruited from the intensive care unit shortly after suffering severe brain injuries due to trauma such as car accidents, strokes, or cardiac arrests. Others were included months or even years post-injury and were living in nursing homes or at home.
In addition to the 241 participants who didn’t respond to basic commands, researchers also studied 112 individuals who did. This second group was expected to perform well on the fMRI and EEG tests. However, in 62% of these cases, no brain responses indicating they were covertly obeying instructions were found. The authors suggest this discrepancy might reflect the complexity of the fMRI and EEG tasks and the high-level cognitive skills needed to successfully carry them out.
Understanding that a patient is cognitively aware and has more abilities than initially visible can significantly impact their clinical care. “Families have expressed that when a positive test result revealing cognitive motor dissociation is communicated to the patient’s medical team, it changes how the team engages with their loved one,” Bodien noted. “Suddenly, the team becomes more attuned to subtle behavioral cues that could indicate voluntary control, speaks directly to the patient, or plays music in the room. Conversely, failing to recognize cognitive motor dissociation can lead to serious repercussions, such as premature withdrawal of life support, missed signs of awareness, and insufficient access to rehabilitation services.”
“We find that this stark separation between preserved cognitive abilities and the lack of behavioral evidence thereof is not unusual. I believe we now bear an ethical responsibility to engage with these patients and assist them in reconnecting with the world,” commented senior author Nicholas Schiff, MD, the Jerold B. Katz Professor of Neurology and Neuroscience in the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine and administrative lead of the consortium. “Our focus for the past twenty years has been to create a sustained effort that benefits patients with consciousness disorders through rigorous medical research, technological advancement, and improved clinical systems.”
One limitation of the study was the lack of standardized testing; each site had its own approach, leading to data variability. Furthermore, many participants were recruited because family members heard about the study and contacted researchers. This recruitment method hampers the researchers’ ability to establish the overall prevalence of cognitive motor dissociation. There currently aren’t any professional guidelines about how to evaluate cognitive motor dissociation, and most centers lack the capacity to conduct this testing; improving clinical translation will be crucial for future research efforts.
“To advance in this field, we need to fine-tune our assessment tools and create systems for methodical and practical evaluation of unresponsive patients so that testing becomes more widely available,” said Bodien. “The Emerging Consciousness Program at Mass General Hospital provides these evaluations clinically; however, in other locations, patients might have to join a research study for similar testing. While we understand that cognitive motor dissociation is relatively common, we require further resources and infrastructure to enhance recognition of this condition and ensure adequate support for patients and their families.”
The researchers also noted that these findings may encourage the exploration of specific interventions aimed at fostering effective communication, such as brain-computer interfaces.
