Fig. 1

Classification of consciousness by three dimensions. Patients are categorized along three dimensions: overt cognition (X-axis) assessed with the CRS-R or CAP, motor function (Y-axis) evaluated with the CRS-R during bedside behavioral evaluations, and covert cognition (Z-axis) that cannot be detected by behavioral evaluations and is assessed through fMRI and EEG. Levels of consciousness, as indicated by overt cognition, range from “coma and VS/UWS,” MCS minus (absence of language function), MCS plus (presence of language function), PTCS, and “CLIS, LIS, to full recovery” of consciousness. These levels are further differentiated by motor function. In cases of coma, VS/UWS, and MCS minus, patients demonstrating active responses on fMRI or EEG can be diagnosed with CMD. If patients exhibit fMRI and EEG responses within the association cortex during passive language or music stimuli, they are considered in this approach of visualizing conscious states to have HMD status. Patients lacking behavioral evidence of language ability (coma, VS, and MCS−) are classified as TN in the absence of fMRI or EEG responses. Patients with behavioral evidence of language capability (MCS+, PTCS, CLIS, LIS, and full recovery) are classified as FN if there are no corresponding fMRI or EEG responses, and as TP if such responses are present. VS: vegetative state; UWS: unresponsive wakefulness syndrome; MCS: minimally conscious state; PTCS: post-traumatic confusional state; CLIS: complete locked-in syndrome; LIS: locked-in syndrome with preservation of minimal motor function; CRS-R: Coma Recovery Scale-Revised; CAP: Confusion Assessment Protocol; CMD: Cognitive motor dissociation; HMD: Higher-order cortex motor dissociation; TN: true negatives; FN: false negatives; TP: true positives; fMRI: functional MRI; EEG: electroencephalographic. Adapted from Edlow et al. [52]