Disorders of consciousness

Disorders of consciousness are organic mental disorders in which there is impairment of the ability to maintain awareness of self and environment and to respond to environmental stimuli. Dysfunction of the cerebral hemispheres or brain stem reticular formation may result in this condition. Consciousness is the state of awareness of self and environment, and responsiveness to external stimulation and inner need. Unconsciousness is a state of unawareness of self and environment or a suspension of those mental activities by which people are made aware of themselves and their environment, coupled always with a diminished responsiveness to environmental stimuli and remain behaviorally unresponsive to all external stimuli. Sleep is a recurrent, reversible physiologic, form of reduced consciousness in which the responsiveness of brain systems responsible for cognitive function is globally reduced, so that the brain does not respond readily to environmental stimuli. A key difference between sleep and coma is that sleep is intrinsically reversible on sufficient stimulation to a normal waking state. In contrast, if patients with pathologic alterations of consciousness can be awakened at all, they rapidly fall back into a sleep-like state when stimulation ceases.