coma
n. a profound state of unconsciousness due to dysfunction of the ascending reticular activating system, cerebral cortex, and other brain areas critical to alertness and cognition. A person in a coma is unaware of the self or environment, does not engage in any voluntary activity, and does not respond to light, sound, touch, or other stimuli. He or she cannot be roused, his or her eyes remain closed, and normal sleep and wake cycles cease. Causes are numerous but commonly include head injury or other trauma, blockage or rupture of cerebral blood vessels, infection, oxygen deprivation (from cardiac arrest, hypoxia, etc.), severe drug or alcohol intoxication, seizures, strokes, tumors, and metabolic disturbances and other disorders. Comas typically last 10 to 14 days, with affected individuals often progressing to a minimally conscious state or a vegetative state. Prognosis depends on the severity and site of neurological damage as well
as the cause and duration of the coma. The Glasgow Coma Scale is the most commonly used instrument for assessing the severity of consciousness deficits, but others include the Grady Coma Scale, the Full Outline of Unresponsiveness Score, and the Wessex Head Injury Matrix. Electroencephalography and somatosensory potentials also are regarded as useful tools for exploring residual brain activity and providing information for recovery. —comatose
adj.