A 72-year-old man with a 3-year history of progressive memory loss and difficulty with word-finding is brought to the hospital by his son. Over the past 6 months, he has become increasingly forgetful, misplacing objects and forgetting recent conversations. His wife reports he gets lost in familiar places and has difficulty managing finances. On examination, he is alert and oriented to person and place but not date. His vital signs are stable (BP 128/82, HR 78, RR 16, Temp 37.2°C). Blood glucose is 110 mg/dL, serum electrolytes are normal, and TSH is 2.1 mIU/L. Over the past 24 hours, there has been no acute change in mental status. What is the most likely diagnosis?

Explanation

## Diagnosis: Dementia of the Alzheimer Type ### Clinical Features Supporting Dementia **Key Point:** The insidious onset over 3 years, gradual progression, stable vital signs, normal metabolic parameters, and absence of acute fluctuation are hallmarks of dementia, not delirium. ### Differential Diagnosis: Delirium vs Dementia | Feature | Delirium | Dementia | |---------|----------|----------| | **Onset** | Acute (hours to days) | Insidious (months to years) | | **Course** | Fluctuating, waxing-waning | Steady, progressive decline | | **Consciousness** | Altered (hyperalert or lethargic) | Alert (until late stages) | | **Attention** | Severely impaired | Relatively preserved early | | **Reversibility** | Often reversible | Usually irreversible | | **Vital signs** | Often abnormal | Usually normal | | **Metabolic causes** | Common (infection, drugs, hypoxia) | Absent or unrelated | **High-Yield:** This patient has a **3-year progressive course** with stable vitals, normal labs, and no acute precipitant — this is dementia until proven otherwise. ### Why Alzheimer Type? 1. **Memory loss** (especially recent memory) is the cardinal early feature 2. **Visuospatial dysfunction** (getting lost in familiar places) 3. **Gradual progression** over years 4. **Preserved consciousness** and stable vital signs 5. **Negative workup** (normal glucose, electrolytes, TSH) **Clinical Pearl:** The son's report of a 6-month *acceleration* in forgetfulness does not change the diagnosis — this is typical of Alzheimer disease, which shows variable rates of decline. Absence of acute change rules out delirium. **Mnemonic: DEMENTIA** — Decline (gradual), Episodic memory loss, Memory for recent events worst, Early disorientation to time, Neurodegeneration (progressive), Temporal lobe atrophy (AD), Irreversible (usually), Alert (preserved consciousness). ### Why Not Delirium? - No acute onset (3-year history) - No fluctuation over hours/days - No metabolic derangement (glucose, electrolytes, TSH normal) - No fever or signs of infection - Stable hemodynamics - Alert and oriented to person/place (only disoriented to date, consistent with dementia) ### Why Not Mild Cognitive Impairment? MCI is a prodrome; this patient already has functional decline (cannot manage finances, gets lost) — he has crossed into dementia. [cite:Harrison 21e Ch 383]