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Suspected mixed Alzheimer’s and vascular dementia — MSRA MCQ

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HardMRISuspected mixed Alzheimer’s and vascular dementiaMSRA

A 74-year-old woman is assessed in a memory clinic after 18 months of progressive cognitive decline affecting medication management, finances and cooking. Her husband describes early impairment of recent memory, followed by two noticeable stepwise deteriorations. She has hypertension, type 2 diabetes and atrial fibrillation. There is no acute fluctuation in attention, depressive illness, alcohol excess or offending medication. FBC, U&Es, calcium, LFTs, TSH, vitamin B12 and folate are normal. Specialist assessment confirms cognitive impairment, with disproportionate deficits in executive function and processing speed as well as episodic memory. Examination shows mildly slowed gait but no parkinsonism, visual hallucinations, fluctuating cognition or features of REM sleep behaviour disorder. A CT head performed 3 years ago after a fall showed an old lacunar infarct. The clinician suspects mixed Alzheimer’s and vascular dementia; clarifying the subtype would affect diagnosis and management. She has no contraindication to MRI. What is the most appropriate next investigation to assist subtype diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Arrange structural MRI brain to assess for vascular pathology and assist subtype diagnosis

Explanation lettering: B = shown as A · D = shown as B · E = shown as C · C = shown as D · A = shown as E

Structural MRI brain is the preferred investigation. Cognitive decline has been confirmed and reversible causes have been excluded. Although vascular disease is plausible because of her vascular risk factors, lacunar infarct, executive dysfunction and stepwise deterioration, the prominent episodic-memory impairment means that mixed Alzheimer’s and vascular dementia remains possible. The subtype is therefore uncertain and establishing it would change diagnostic formulation and management. NICE recommends MRI when vascular dementia is suspected but the dementia subtype is uncertain; CT is used if MRI is unavailable or contraindicated. A is incorrect because vascular lesion burden and a stepwise history alone do not establish vascular dementia, particularly where mixed pathology is possible. B is plausible because CT can identify established infarction and is an alternative when MRI cannot be performed, but she can undergo MRI. C is reserved for uncertainty where Alzheimer’s disease is suspected after appropriate initial assessment; it is not the first-choice test for suspected vascular pathology. D is used when dementia with Lewy bodies is suspected; the absent core clinical features make this inappropriate here.

Reference: Dementia: assessment, management and support for people living with dementia and their carers (NG97) – Recommendations (2018) — https://www.nice.org.uk/guidance/NG97/chapter/recommendations Dementia: assessment, management and support for people living with dementia and their carers (NG97) – Further tests for vascular dementia (2018) — https://www.nice.org.uk/guidance/NG97/chapter/recommendations