Covert Brain Complexity in the Intensive Care Unit

Early detection of consciousness in critically ill patients with severe brain injuries has a profound impact on prognostication and decisions about whether to continue or limit life-sustaining therapy. The current state-of-the-art protocol to detect signs of consciousness includes standardized behavioral assessments, task-based functional magnetic resonance imaging (fMRI), and task-based electroencephalography (EEG). However, this approach has limited diagnostic sensitivity because auditory pathways may be disrupted, and conscious patients may lack attention, language, or other cognitive functions required to perform a task. Transcranial magnetic stimulation EEG (TMS-EEG) has the potential to overcome these limitations by directly perturbing the cerebral cortex to compute the perturbational complexity index, a neural correlate of consciousness. To date, TMS-EEG studies have focused on patients in the subacute or chronic stage of recovery from severe brain injury. Here, we report the proof-of-concept application of TMS-EEG for a critically ill patient in the acute stage of brain injury recovery. We show that TMS-EEG is feasible to perform as part of a multimodal protocol in the intensive care unit and that TMS-EEG may detect signs of consciousness that elude current state-of-the-art assessments.