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Delirium on Dementia Recognition — MRCPsych Paper B MCQ

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ModerateOld Age PsychiatryDelirium on Dementia RecognitionMRCPsych Paper B

A 75-year-old man with established Alzheimer's disease is admitted to hospital following an abrupt change in his mental state. Over the preceding 24 hours, he has alternated between drowsiness and restlessness, has been unable to sustain attention, and has reported seeing unfamiliar people in the room. His family confirms that these symptoms are new and that his cognition had previously been stable for several months. Neurological examination shows no focal deficit. Which clinical condition best explains this presentation?

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Correct answer: D — Delirium superimposed on dementia

The correct answer is delirium superimposed on dementia. The decisive features are the abrupt onset over 24 hours, impaired attention, fluctuating arousal and new visual hallucinations in a person whose baseline dementia had been stable. NICE identifies changes over hours or days in cognition and perception as indicators of delirium; pre-existing dementia substantially increases vulnerability. Alzheimer's disease usually progresses gradually rather than producing an abrupt attentional disturbance. Visual hallucinations and cognitive fluctuation can occur in dementia with Lewy bodies, but that is a chronic neurodegenerative syndrome rather than a new 24-hour change. Stroke is less likely without a focal neurological deficit, although it remains a potential precipitant requiring assessment. Depression does not usually cause acute fluctuation in attention or arousal. The underlying cause of the delirium should be sought and treated urgently.

Reference: NICE. Delirium: prevention, diagnosis and management in hospital and long-term care (CG103), sections 1.3 and 1.6. Updated 2023. https://www.nice.org.uk/guidance/cg103/chapter/Recommendations