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I. DSM IV Diagnostic Criteria

A. Disturbance of consciousness with reduced ability to focus, sustain or shift attention

B. The change in cognition or perceptual disturbance is not due to dementia.

C. The disturbance develops over a short period of time (hours to days) and fluctuates during the course of the day.

D. There is clinical evidence that the disturbance is caused by a general medical condition and/or substance use or withdrawal.

II. Clinical Features

A. The disorder is characterized by impairments of consciousness, awareness of environment, attention and concentration. Many patients are disoriented and display disorganized thinking. A fluctuating clinical presentation is the hallmark of the disorder, and the patient may have moments of lucidity during the course of the day.

B. Perceptual disturbances may take the form of misinterpretations, illusions or frank hallucinations. The hallucinations are most commonly visual in nature, but other sensory modalities can also be misperceived.

C. Sleep-wake cycle disturbances are common, and psychomotor agitation can be severe, resulting in pulling out IV's and catheters, falling, and combative behavior. The quietly delirious patient may reduce fluid and food intake without overtly displaying agitated behavior.

D. Failure to report use of medications or substance abuse is a common cause of withdrawal in hospitalized patients. Infection and medication interaction or toxicity is a common cause of in the elderly.

E. is associated with increased morbidity and mortality because injuries may occur when the patient is delirious and agitated and unrecognized may result in permanent cognitive impairment.

F. The incidence of in hospitalized patients is 10-15%, with higher rates in the elderly. Other patients at risk include those with known CNS disorders, substance abusers, and HIV positive patients.

III. Classification

A. due to a general medical condition (specify which condition)

B. due to substance intoxication (specify which substance)

C. due to a substance withdrawal (specify which substance)

D. due to a multiple etiologies (specify which conditions)

E. not otherwise specified (unknown etiology or due to other causes such as sensory deprivation)

IV. Differential Diagnosis

A. Dementia

1. Dementia is the most common disorder that must be