Delirium (acute confusional state)

Delirium is a functional brain disorder characterized by disturbances of consciousness, attention, and cognition. The term ‘acute confusional state’ is often used synonymously with ‘delirium’. Delirium may be associated with a range of associated clinical features including increased or decreased psychomotor activity (hyperactive and hypoactive variants), hallucinations and delusions, and efferent sympathetic hyperactivity. Delirium with pronounced psychomotor and sympathetic hyperactivity is more often seen in younger patients with alcohol or substance intoxication/withdrawal (delirium tremens), but no cause is specific to a clinical subtype. Delirium is distinguished from dementia (with which it may coexist, as dementia is a major risk factor for delirium) by its speed of onset (over hours or days) and reversibility with correction of the underlying cause. In some patients, however, delirium may be followed by long-term cognitive impairment, suggesting that the pathophysiology of delirium overlaps with that of dementia.