Distinguish delirium from dementia on mental status exam features.

• A. Dementia is acute and fluctuating with impaired attention.
• B. Delirium is acute and fluctuating with impaired attention and consciousness; dementia is chronic, progressive with memory impairment, but attention relatively preserved early.
• C. Delirium is chronic and progressive.
• D. Dementia presents with fluctuating levels of consciousness.

Answer: (B)

Distinguishing delirium from dementia on the mental status exam hinges on onset, course, and level of alertness. Delirium is an acute condition that comes on suddenly and fluctuates over hours to days. It classically features impaired attention and often a disturbance in consciousness or arousal; patients may be disoriented, distractible, or have perceptual disturbances. In contrast, dementia progresses slowly and chronically, with primary problems in memory and other cognitive domains that worsen over months to years. Attention is typically relatively preserved in the early stages of dementia, with orientation and memory slipping as the disease advances.

The best description therefore links delirium to an abrupt onset and fluctuating attention and consciousness, while describing dementia as a long-standing, progressive syndrome with memory impairment and relatively preserved attention early on. This aligns with how the mental status exam would present each condition: delirium shows acute changes and fluctuating awareness; dementia shows a gradual, sustained decline with memory issues and Attention that is intact early.