In a patient with known dementia, which observation should most urgently prompt reevaluation for delirium?

• A. Gradual decline over years.
• B. Sudden onset of agitation and fluctuating attention.
• C. Stable mood.
• D. Consistent cognitive function.

Answer: (B)

Delirium is an abrupt, often reversible disturbance of awareness and attention that tends to fluctuate over hours to days. In someone who already has dementia, the presence of a sudden change signals a superimposed delirium and requires urgent assessment to identify and treat reversible causes such as infection, dehydration, medication changes, or metabolic problems. The observation described—sudden onset of agitation with fluctuating attention—best fits this pattern because it shows an acute, fluctuating change from the patient’s usual function, which differentiates delirium from the slower, progressive course of dementia itself.

Gradual decline over years reflects the typical progression of dementia rather than an acute confusional state. Stable mood and consistent cognitive function imply no new, acute change in mental status at that moment, which is less suggestive of delirium. If you notice sudden, fluctuating changes in attention or consciousness in a patient with dementia, that should prompt immediate reevaluation for delirium and its underlying cause.