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Posterior Cortical Atrophy — MRCPsych Paper B MCQ

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HardOld Age PsychiatryPosterior Cortical AtrophyMRCPsych Paper B

A 65-year-old man has a 3-year history of progressive difficulty reading, locating objects in front of him, recognising familiar objects and faces, and navigating previously familiar environments. Ophthalmological examination is normal. Episodic memory and language remain relatively preserved. MRI shows disproportionate bilateral occipitoparietal atrophy with relative preservation of the medial temporal lobes. He has no cognitive fluctuations, recurrent formed visual hallucinations, REM sleep behaviour disorder or spontaneous parkinsonism. Which underlying disease most likely accounts for this clinical syndrome?

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Correct answer: D — Alzheimer's disease

The correct answer is **A, Alzheimer's disease**. Progressive alexia, visual agnosia, prosopagnosia and visuospatial disorientation with relatively preserved early memory and language, alongside disproportionate occipitoparietal atrophy sparing the medial temporal lobes, define posterior cortical atrophy (PCA). PCA is a clinico-radiological syndrome rather than a single pathology, but Alzheimer's disease is by far its commonest cause—the primary neuropathological diagnosis in around 94% of autopsied cases in the largest international series. Dementia with Lewy bodies can occasionally produce a PCA phenotype, but the stated absence of fluctuations, formed visual hallucinations, REM sleep behaviour disorder and parkinsonism makes it much less likely. Frontotemporal dementia presents with behavioural change or language-predominant impairment, not posterior visual dysfunction. Vascular dementia requires a compatible vascular lesion burden or stepwise course, absent here. Normal pressure hydrocephalus causes gait disturbance, cognitive slowing and urinary incontinence with ventriculomegaly, not focal posterior cortical atrophy.

Reference: Chapleau M et al. Demographic, clinical, biomarker, and neuropathological correlates of posterior cortical atrophy: an international cohort study and individual participant data meta-analysis. The Lancet Neurology. 2024;23(2):168–177. https://pubmed.ncbi.nlm.nih.gov/38267189/