Corticobasal degeneration — MRCPsych Paper A MCQ

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ModerateNeuropathologyCorticobasal degenerationMRCPsych Paper A

A 67-year-old woman has a 3-year history of progressive asymmetric limb apraxia, rigidity and cortical sensory loss. MRI shows asymmetric frontoparietal atrophy. At postmortem examination, which neuropathological finding would most strongly support corticobasal degeneration as the underlying pathology?

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Correct answer: D — Four-repeat tau-positive astrocytic plaques

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

The correct answer is E. Progressive asymmetric rigidity and apraxia accompanied by cortical sensory loss and asymmetric frontoparietal atrophy constitute a classic corticobasal syndrome. When the underlying disease is corticobasal degeneration, the characteristic neuropathology is a four-repeat tauopathy involving neurons and glia; tau-positive astrocytic plaques are particularly characteristic. Tufted astrocytes (D) are the closest distractor because progressive supranuclear palsy is also a four-repeat tauopathy and can produce corticobasal syndrome, but its characteristic astroglial lesion is the tufted astrocyte. Glial cytoplasmic inclusions (B) indicate multiple system atrophy, while Lewy bodies (A) occur in Parkinson disease and dementia with Lewy bodies. Prion plaques (C) would suggest a prion disease, usually with a more rapidly progressive presentation.

Reference: Koga S, Josephs KA, Aiba I, Yoshida M, Dickson DW. Neuropathology and emerging biomarkers in corticobasal syndrome. Journal of Neurology, Neurosurgery & Psychiatry. 2022;93:919–929. https://jnnp.bmj.com/content/93/9/919