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Difficulty: HardDiagnostic Workup and Test Sequencing

A 73-year-old male retired postal worker is brought to the clinic by his son due to a 14-month history of progressive memory decline. The son reports that the patient repeatedly asks the same questions, has gotten lost twice while driving to a familiar local grocery store, and recently made several significant errors while balancing his checkbook. The patient has a history of well-controlled hypertension and osteoarthritis. He takes lisinopril and occasional acetaminophen. Vital signs are normal. Physical and detailed neurological examinations reveal no focal deficits, resting tremor, or gait abnormalities. He scores 19/30 on the Montreal Cognitive Assessment (MoCA), losing points primarily on delayed recall, visuospatial drawing, and attention. Which of the following tests are indicated as part of the routine initial diagnostic workup for this patient's cognitive decline? (Select all that apply)

  1. Serum thyroid-stimulating hormone (TSH) levelAnswer
  2. Serum vitamin B12 levelAnswer
  3. Magnetic resonance imaging (MRI) of the brainAnswer
  4. D
    Apolipoprotein E (APOE) genotyping
  5. E
    Fluorodeoxyglucose-positron emission tomography (FDG-PET) scan of the brain
  6. F
    Cerebrospinal fluid (CSF) analysis for amyloid-beta and tau proteins

Answer

The correct initial diagnostic evaluation includes a serum TSH level, a serum vitamin B12 level, and an MRI of the brain.
The initial evaluation of a patient with objective cognitive impairment requires assessing for reversible causes and ruling out structural brain lesions. Standard medical guidelines mandate routine laboratory testing with serum vitamin B12 and TSH levels, as deficiencies in these domains can independently mimic or exacerbate neurocognitive disorders. Additionally, structural neuroimaging, preferably an MRI of the brain (or non-contrast CT if MRI is contraindicated), is indicated for all patients with new-onset cognitive decline. This imaging evaluates for cerebrovascular disease, tumors, subdural hematomas, and normal pressure hydrocephalus, while establishing a baseline of regional cerebral atrophy.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and assessment scores.
The patient demonstrates an insidious, progressive cognitive decline impairing instrumental activities of daily living, consistent with a major neurocognitive disorder (dementia), likely Alzheimer disease.
Establishing the clinical syndrome is necessary before determining the appropriate diagnostic algorithms.
2
Identify the guideline-directed initial diagnostic workup for new-onset dementia.
Current guidelines mandate evaluating for reversible metabolic/endocrine causes and ruling out structural brain pathology.
Certain treatable conditions can mimic or exacerbate neurocognitive decline and must be excluded.
3
Select the specific modalities that fulfill the preliminary workup criteria.
Serum B12 and TSH are the standard initial laboratory tests. MRI of the brain is the preferred structural imaging modality.
These tests provide a high-yield, non-invasive foundation for the diagnosis without prematurely exposing the patient to unnecessary advanced imaging or invasive procedures.

Key Concept

Standard initial diagnostic workup for cognitive impairment and dementia
Estimated Time:1m 0s
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Topics

Diagnostic Workup and Test Sequencing

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