What is a delirium?

Delirium (acute confusional
state) is a common and severe neuropsychiatric syndrome with core features of acute
onset and fluctuating course, attentional deficits and generalized severe
disorganization of behavior. It typically involves other cognitive deficits, changes in
arousal (hyperactive, hypoactive, or mixed), perceptual deficits, altered sleep-wake
cycle, and psychotic features such as hallucinations and delusions. It is often caused
by a disease process 'outside' the brain, such as common forms of infection (UTI,
pneumonia) or by drug effects, particularly anticholinergic or other CNS depressants
(benzodiazapenes and opioids). It can also be caused by virtually any primary disease of
the href="http://en.wikipedia.org/wiki/Central_nervous_system">central nervous
system