Coma
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document in english
medical studies
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date published 23/08/2007
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SummaryConsciousness, the awareness of self and environment, requires both arousal and mental content; the anatomic substrate includes both reticular activating system and cerebral cortex. Coma is a state of unconsciousness that differs from syncope in being sustained and from sleep in being less easily reversed. Cerebral oxygen uptake (cerebral metabolic rate of oxygen [CMRO2]) is normal in sleep or actually increases during the rapid eye movement stage, but CMRO2 is abnormally reduced in coma.
Table of Contents- Consciousness, the awareness of self and environment, requires both arousal and mental content; the anatomic substrate includes both reticular activating system and cerebral cortex
- Coma is clinically defined by the neurologic examination, especially responses to external stimuli
- Fever may imply infection or heat stroke; hypothermia may occur with cold exposure (especially in alcoholics),
- In their classic monograph, Plum and Posner (1980) divided the causes of coma into supra- and infratentorial structural lesions and diffuse or metabolic diseases
- Flexor postures generally imply a more rostral lesion and have a better prognosis than extensor posturing, but the pattern of response may vary with different stimuli, or there may be flexion of one arm and extension of the other
- Pupillary abnormalities in coma may reflect an imbalance between input from the parasympathetic and sympathetic nervous systems or lesions of both
- With few exceptions, metabolic disease does not cause unequal or unreactive pupils
- The EEG may also reveal asymmetries or evidence of clinically unsuspected seizure activity
- During the downward course of transtentorial herniation, there may be hemiparesis ipsilateral to the cerebral lesion, attributed to compression of the contralateral midbrain peduncle against the tentorial edge (Kernohan notch).
- The clinical picture of pontine hemorrhage (i.e., sudden coma, pinpoint but reactive pupils, and no eye movement) is characteristic, but if the sequence of signs in a comatose patient is unknown
- VEGETATIVE STATE
- BRAIN DEATH
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