A new approach to assess self-awareness in patients who do not regain full consciousness after a coma, the result of a collaboration between the École normale supérieure – PSL (Paris), the University of Liège (GIGA Consciousness) and the Brain Center (CHU de Liège).
The new study conducted jointly by the University of Liège and the École normale supérieure – PSL shows that heart-brain interactions, measured using electroencephalography (EEG), constitute a new diagnostic route for patients with disturbances of consciousness. This study is published in the Journal of Neuroscience.
Catherine Tallon-Baudry (Department of Cognitive Studies, ENS, CNRS) explains: “ The scientific community already knew that in healthy participants, the brain’s response to the beating of the heart is linked to the perception, body and consciousness of self. We now show that we can also obtain clinically meaningful information if we probe this interaction in patients with impaired consciousness. Over the past several decades, several significant improvements have been made to the diagnosis of these patients, but measuring self-awareness in these patients who cannot communicate remains a great challenge.
For their study, the researchers included 68 patients with impaired consciousness. 55 patients suffered from the minimal state of consciousness and exhibited fluctuating but consistent signs of consciousness but were unable to communicate, and 13 patients were in an unresponsive wakeful state (formerly called a vegetative state) and showed no signs behavioral awareness. These patients were diagnosed using the Revised Coma Recovery Scale, a standardized clinical test to assess conscious behavior.
“ As these patients have suffered severe brain damage, they may be unable to show behavioral signs of consciousness. Therefore, we also based our diagnosis on the metabolism of the brain as a probe of consciousness. It is a cutting-edge neuroimaging technique that improves the diagnosis of patients with impaired consciousness. These very informative images can only be acquired in specialized medical research centers ”, explains Jitka Annen (GIGA Consciousness, ULiège).
The researchers recorded brain activity in the resting state (that is, without a specific task or stimulation). They selected segments of the EEG just after a heartbeat and segments at random time points (i.e. unrelated to a heartbeat). They then used machine learning algorithms to classify (or diagnose) patients into the two diagnostic groups.
Diego Candia-Rivera (Department of Cognitive Studies, ENS) specifies: “ The segments of the EEG not related to heartbeats were informative to predict whether a patient was conscious or not, but the segments of the EEG related to heartbeats. heartbeats were more precise in this regard. Our results indicate that the potential evoked by the heartbeat may give us additional evidence of the presence of consciousness. “
Importantly, the responses evoked by the heartbeats were more consistent with the diagnosis based on brain metabolism than the diagnosis based on behavioral assessment. It therefore appears that the evoked heart rate response can be used to measure a prospect of (recovery of) self-awareness that is not successfully assessed using behavioral tools.
“ The next challenge is to translate our results into clinical applications so that all patients with impaired consciousness can benefit from a better diagnosis using widely available bedside assessment technologies ,” concludes Steven Laureys, manager. of the GIGA Consciousness research unit at ULiège and of the Center du Cerveau at the CHU de Liège.
Neural responses to heartbeats detect residual signs of consciousness during resting state in post-comatose patients , Diego Candia-Rivera, Jitka Annen, Olivia Gosseries, Charlotte Martial, Aurore Thibaut, Steven Laureys, Catherine Tallon-Baudry, Journal of Neuroscience.
Provided by Liege University