Table 1 Definitions of common states of consciousness

Coma [4]

State of unresponsiveness in which the patient lies with eyes closed and cannot be aroused to respond appropriately to stimuli even with vigorous stimulation (no eye opening or adapted motor response even to painful stimuli).

Coma-1a or 1b^a (based on EEG compatibility [1a; e.g., slow unreactive predominant delta] or not [1b; e.g., reactive predominant alpha]). Some authors use a Glasgow coma scale cut-off (e.g., < 8) but this is very misleading since this can include UWS or even MCS patients in whom the ascending reticular activating system (ARAS) is likely to be functional

Unresponsive wakefulness syndrome (UWS) [9]

State of unresponsiveness in which the patient shows spontaneous eye opening without any behavioral evidence of self or environmental awareness

Vegetative state (VS), coma vigil, apallic state, UWS/VS-2a or2b^a (CMS excluded [2a] or not [2b] by functional MRI or EEG)

Minimally conscious state (MCS) [8]

State of severely impaired consciousness with minimal but definite behavioral evidence of self or environmental awareness Distinction between MCS “minus” and “plus” has been proposed [3]

• MCS–minus: visual fixation/pursuit or adapted motor reaction to pain

• MCS-plus: evidence of language processing (e.g., command following, verbalization...)

Cortically Mediated State^a (CMS, in that case CMS-3b as based on behavior alone).

Locked-in syndrome (LIS) [4]

State in which the patient is actually conscious but de-efferented, resulting in paralysis of all four limbs and the lower cranial nerves

De-efferented state, Conscious state-4b^a

Conscious state^b [4]

State of full awareness of the self and one’s relationship to the environment, evidenced by verbal or non-verbal (e.g., purposeful motor behavior) behavior

Exit-MCS (or EMCS) when the patient emerged from MCS, Conscious state-4b^a

Higher-order cortex motor dissociation (HMD) [26]

Comatose, UWS or MCS-minus (clinically defined) patients that show association cortex responses to language stimuli

CMS-3a^a

Cognitive motor dissociation (CMD) [2]

Comatose^c, UWS or MCS-minus clinically defined patients that show MRI or electrophysiologic evidence of command following

Functional locked-in syndrome, Conscious state-4a^a

Communicating-CMD (Com-CMD)

CMD defined patients able to communicate using a brain computer interface (BCI)

Conscious state-4a^a