"Waxing and waning" level of consciousness with acute onset. Reversible.- Rapid ↓ in attention span and level of arousal.

Characterized by:- disorganized thinking- hallucinations (often visual)- misperceptions- disturbance in sleep-wake cycle- cognitive dysfunction- agitation

- Usually 2° to other illness (eg, CNS disease, infection, trauma, substance abuse/withdrawal, metabolic/electrolyte disturbances, hemorrhage, urinary/fecal retention).- May be caused by medications (eg, anticholinergics), especially in the elderly.

- Most common presentation of altered mental status in inpatient setting, especially in the intensive care unit and with prolonged hospital stays.

- EEG may show diffuse slowing.

Treatment is aimed at identifying and addressing underlying condition. Use antipsychotics acutely as needed. Avoid benzodiazepines.