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A 78-year-old male with a history of mild cognitive impairment is brought to the psychiatric consultation service by his daughter, who reports that over the past 2 days he has become confused, agitated, and unable to recognize family members. She states he was at his baseline cognitive function 3 days ago, managing his finances and having coherent phone conversations. On examination, he is disoriented to time and place, his attention fluctuates markedly over the 30-minute interview, at times he is lucid and conversational, then minutes later he is picking at his bedsheets and mumbling incoherently. He reports seeing 'children playing in the corner' of his room. His sleep-wake cycle is severely disrupted, with agitation peaking in the evening. Vital signs show a temperature of 101.2°F and heart rate of 104 bpm. His daughter asks whether his dementia has suddenly worsened. What is the most likely explanation for this acute change?
Explanation
Delirium versus dementia differentiation is a critical clinical skill. The key differentiators are: (1) onset. Delirium is acute (hours to days), dementia is insidious (months to years); (2) attention. Delirium causes fluctuating, impaired attention, while dementia typically preserves attention until late stages; (3) course. Delirium fluctuates throughout the day (often worse at night), dementia is relatively stable day to day; (4) reversibility. Delirium is potentially reversible by treating the underlying cause. Always look for vital sign abnormalities, new medications, infections, or metabolic derangements when an elderly patient acutely decompensates.
Key Takeaway
Acute cognitive deterioration over hours to days with fluctuating attention, visual hallucinations, and vital sign abnormalities in an elderly patient is delirium until proven otherwise, even when pre-existing cognitive impairment is present.