A 76-year-old admitted for a urinary tract infection becomes acutely disoriented at night, cannot attend to a simple conversation, and sees insects crawling on the wall. Two weeks ago she was oriented and independent. Which single feature best separates this state from a dementing illness?
- A Presence of visual hallucinations
- B Impairment of attention and arousal that fluctuates over hours ✓
- C Disorientation to time and place
- D Presence of behavioural disturbance
Correct answer: B. Impairment of attention and arousal that fluctuates over hours
Explanation
Delirium is defined by acute onset, fluctuating course, and primary impairment of attention and level of arousal, whereas dementia spares attention until late and progresses over months to years. Visual hallucinations occur in both delirium and dementia with Lewy bodies, disorientation occurs in both conditions, and behavioural disturbance is nonspecific. The abrupt change from baseline two weeks ago is itself decisive against dementia.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.