Coma and clinical states allied to it represent severe or total global reductions of mental function due to structural or physiological impairments of the brain. Coma is characterized by a sustained loss of the capacity of arousal, preventing any expression of potential mental function. The eyes are closed, sleep-wake cycles disappear, and even vigorous stimulation produces no evidence of appropriate psychological response. Stupor describes a state of spontaneous unarousability in which strong external stimuli can transiently restore wakefulness. Stupor implies that evidence of at least a limited degree of appropriate mental activity accompanies the arousal, transient though it may be. The vegetative state is the condition wherein arousal (i.e., sleep-wake cycles) returns or remains but appropriate testing measures elicit no evidence of the person’s cognitive awareness of self or environment. The locked-in state describes a condition in which persons retain or regain arousability and self-awareness but because of extensive bilateral paralysis (i.e., deafferentation) can no longer communicate except in severely limited ways. Brain death describes the irreversible loss of function of all neural structures rostral to the foramen magnum.
- Plum F, Posner JB (1982): The Diagnosis of Stupor and Coma. 3rd rev ed. Philadelphia: FA DavisGoogle Scholar