Quantifying consciousness

In 1974, Teasdale and Jennett's Glasgow coma scale (GCS) was published in The Lancet. 1 Teasdale G Jennett B Assessment of coma and impaired consciousness. A practical scale. Lancet. 1974; 2: 81-84 Summary PubMed Scopus (9736) Google Scholar This standardised bedside tool to quantify consciousness became a medical classic. Despite its indisputable worldwide success it has also been criticised. Several investigators disagree that scoring eye opening is sufficiently indicative of activity in brainstem arousal systems and have proposed coma scales that include brainstem reflexes, such as the comprehensive level of consciousness scale, the clinical neurologic assessment tool, the Bouzarth coma scale, and the Maryland coma scale. 2 Laureys S Majerus S Moonen G Assessing consciousness in critically ill patients. in: Vincent JL Yearbook of Intensive Care and Emergency Medicine. Springer-Verlag, Heidelberg2002: 715-727 Google Scholar None of these scales have known widespread use because they generally are more complex than the Glasgow coma scale. A simpler system, the Glasgow Liège scale, 3 Born JD Albert A Hans P Bonnal J Relative prognostic value of best motor response and brain stem reflexes in patients with severe head injury. Neurosurgery. 1985; 16: 595-601 Crossref PubMed Scopus (80) Google Scholar combined the Glasgow coma scale with five brainstem reflexes but also failed to convince the medical community outside its country of origin. Another shortcoming of the Glasgow coma scale is that the increasing use of intubation has rendered its verbal component immeasurable in many patients in coma. A Swedish team, therefore, developed the reaction level scale, which does not include a verbal response criterion but combines different responses into an ordinal eight-graded scale. 2 Laureys S Majerus S Moonen G Assessing consciousness in critically ill patients. in: Vincent JL Yearbook of Intensive Care and Emergency Medicine. Springer-Verlag, Heidelberg2002: 715-727 Google Scholar Outside of Sweden, however, the use of this scale remains very limited. The Glasgow coma scale also lacks reliability when assessing patients progressively recovering from their coma and entering a vegetative or minimally conscious state. For these patients, more sensitive scales are the coma recovery scale-revised, sensory modality assessment and rehabilitation technique, or Wessex head injury matrix. 4 Majerus S Gill-Thwaites H Andrews K Laureys S Behavioral evaluation of consciousness in severe brain damage. in: Laureys S The boundaries of consciousness: neurobiology and neuropathology. Elsevier, Amsterdam2005: 397-413 Crossref Scopus (193) Google Scholar These scales, however, are not adapted for use in acute settings.