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Difficulty: MediumDiagnostic Workup and Test Sequencing

A 74-year-old retired accountant is accompanied to the geriatrics clinic by his son. The family is concerned because the patient has been repeatedly misplacing household items, forgetting recent conversations, and recently got lost while driving a familiar route to the grocery store. These changes have evolved gradually over the past 14 months. The patient feels fine and dismisses the concerns, attributing them to normal aging. Medical history is significant for well-controlled type 2 diabetes mellitus and osteoarthritis. Vital signs are within normal limits. General physical and detailed neurological examinations show no focal deficits, resting tremors, or gait abnormalities. His score on the Montreal Cognitive Assessment is 20/30, with prominent point deductions on delayed recall and visuospatial tasks. Which of the following diagnostic investigations should be ordered concurrently as part of the initial routine evaluation for this patient's cognitive decline? (Select all that apply)

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

Answer

The initial routine diagnostic workup for new-onset cognitive impairment should concurrently include a serum vitamin B12 level, a serum thyroid-stimulating hormone (TSH) level, and structural neuroimaging (such as an MRI of the brain).
In the initial evaluation of any patient presenting with cognitive impairment and suspected dementia, standard of care mandates ruling out reversible, metabolic, and structural etiologies. This core battery of tests concurrently includes serum vitamin B12, thyroid-stimulating hormone (TSH), and structural brain imaging (with MRI being preferred over CT due to higher sensitivity for cerebrovascular disease and regional atrophy). Addressing abnormalities in B12 or TSH can halt or reverse cognitive decline, while an MRI rules out potentially treatable structural causes such as subdural hematomas, normal pressure hydrocephalus, or tumors.

Step-by-Step Solution

1
Identify the primary clinical syndrome from the patient's history and objective findings.
The patient has a 14-month history of progressive memory loss and functional impairment (getting lost) with a Montreal Cognitive Assessment score of 20/30, establishing a major neurocognitive disorder (dementia).
Confirming the presence of cognitive decline dictates the need for a comprehensive diagnostic evaluation.
2
Determine the standard goals of the initial diagnostic workup for dementia.
The primary goal is to identify common, potentially reversible causes of cognitive decline and rule out occult structural brain lesions.
A small but significant percentage of dementia cases are partially or fully reversible if an underlying metabolic, endocrine, or structural abnormality is addressed.
3
Select the guideline-recommended concurrent baseline tests.
Standard guidelines require checking vitamin B12 and TSH levels, along with obtaining a structural neuroimaging study (MRI or non-contrast CT of the brain).
These tests efficiently and safely screen for thyroid dysfunction, vitamin deficiencies, and structural pathology (e.g., strokes, tumors, normal pressure hydrocephalus) without exposing the patient to unnecessary radiation or invasive procedures prematurely.

Key Concept

The initial diagnostic evaluation of a patient with suspected dementia must include screening for reversible causes (using TSH and vitamin B12 levels) and structural neuroimaging (MRI or non-contrast CT of the brain) to rule out mass lesions or cerebrovascular disease.
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Diagnostic Workup and Test Sequencing

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