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Table 1 Definitions of common states of consciousness

From: Uncovering Consciousness in Unresponsive ICU Patients: Technical, Medical and Ethical Considerations

  Definition Other terminologies similar or very close
Behaviorally defined states
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 1ba (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 or2ba (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 Statea (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-4ba
Conscious stateb [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-4ba
Brain functional imaging defined states (e.g., fMRI, fEEG, fNIRS, fPET, fMEG)
Higher-order cortex motor dissociation (HMD) [26] Comatose, UWS or MCS-minus (clinically defined) patients that show association cortex responses to language stimuli CMS-3aa
Cognitive motor dissociation (CMD) [2] Comatosec, UWS or MCS-minus clinically defined patients that show MRI or electrophysiologic evidence of command following Functional locked-in syndrome, Conscious state-4aa
Communicating-CMD (Com-CMD) CMD defined patients able to communicate using a brain computer interface (BCI) Conscious state-4aa
  1. fMRI functional magnetic resonance imaging, fEEG functional electroencephalography, fNIRS function near-infrared spectroscopy, fPET functional positron emission tomography, fMEG functional magnetoencephalography
  2. aTerminology recently proposed by Naccache [50] ranging from 1 to 4 and, taking into account both behavioral (“b”) and brain functional imaging (“a”) evidence. Note that as a consequence, the Cortically Mediated State (CMS) and the Conscious state appear both in the behaviorally and the brain functional imaging sections of this table
  3. bNote that as there is no consensus definition of consciousness yet, provided here is a pragmatic operational definition that would match the currently most commonly used definitions. It corresponds to the access consciousness, using the subjective report criterion
  4. cThe original description actually did not include the comatose state but was included here since the absence of eye opening cannot rule out the possibility of CMD