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Disorders of consciousness may be divided into processes that affect either arousal or content of consciousness, or a combination of both. Arousal behaviors include wakefulness and basic alerting. Anatomically, neurons responsible for these arousal functions reside in the reticular activating system, a collection of neurons scattered through the midbrain, pons, and medulla. The neuronal structures responsible for the content of consciousness reside in the cerebral cortex. Content of consciousness includes self-awareness, language, reasoning, spatial relationship integration, emotions, and the myriad complex integration processes that make us human. One simplistic model holds that dementia is failure of the content portions of consciousness with relatively preserved alerting functions. Delirium is arousal system dysfunction with the content of consciousness affected as well. Coma is failure of both arousal and content functions. Psychiatric disorders and altered mental states may share features such as hallucinations or delusion. Some distinctions between the different states are summarized in Table 168-1.
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Mental status is the clinical state of emotional and intellectual functioning of the individual. The mental status evaluation may be divided into six areas (Table 168-2). Testing the mental status is done both formally and informally in patient evaluation by emergency physicians.1 Assessment of higher mental or cognitive functions requires specific tests. Screening tests are described in the Diagnosis subsections under Delirium, Dementia, and Coma.
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Delirium, acute confusional state, acute cognitive impairment, acute encephalopathy, altered mental status, and other synonyms all refer to a transient disorder with impairment of attention and cognition. The patient has difficulty focusing, shifting, or sustaining attention. Confusion ...