Relationship between etiology and covert cognition in the minimally conscious state

D Cruse, S Chennu, C Chatelle, D Fernández-Espejo, T A Bekinschtein, J D Pickard, S Laureys, A M Owen

Research output: Contribution to journalArticlepeer-review

81 Citations (Scopus)


OBJECTIVES: Functional neuroimaging has shown that the absence of externally observable signs of consciousness and cognition in severely brain-injured patients does not necessarily indicate the true absence of such abilities. However, relative to traumatic brain injury, nontraumatic injury is known to be associated with a reduced likelihood of regaining overtly measurable levels of consciousness. We investigated the relationships between etiology and both overt and covert cognitive abilities in a group of patients in the minimally conscious state (MCS).

METHODS: Twenty-three MCS patients (15 traumatic and 8 nontraumatic) completed a motor imagery EEG task in which they were required to imagine movements of their right-hand and toes to command. When successfully performed, these imagined movements appear as distinct sensorimotor modulations, which can be used to determine the presence of reliable command-following. The utility of this task has been demonstrated previously in a group of vegetative state patients.

RESULTS: Consistent and robust responses to command were observed in the EEG of 22% of the MCS patients (5 of 23). Etiology had a significant impact on the ability to successfully complete this task, with 33% of traumatic patients (5 of 15) returning positive EEG outcomes compared with none of the nontraumatic patients (0 of 8).

CONCLUSIONS: The overt behavioral signs of awareness (measured with the Coma Recovery Scale-Revised) exhibited by nontraumatic MCS patients appear to be an accurate reflection of their covert cognitive abilities. In contrast, one-third of a group of traumatically injured patients in the MCS possess a range of high-level cognitive faculties that are not evident from their overt behavior.

Original languageEnglish
Pages (from-to)816-22
Number of pages7
Issue number11
Publication statusPublished - 13 Mar 2012


  • Adolescent
  • Adult
  • Aged
  • Arousal
  • Automatic Data Processing
  • Awareness
  • Brain Injuries
  • Child
  • Cognition
  • Coma
  • Communication
  • Consciousness
  • Electroencephalography
  • Female
  • Hearing
  • Humans
  • Imagination
  • Male
  • Middle Aged
  • Movement
  • Persistent Vegetative State
  • Prognosis
  • Reflex
  • Support Vector Machine
  • Verbal Behavior
  • Vision, Ocular
  • Young Adult


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