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Parkinson disease dementia — MRCPsych Paper A MCQ

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ModerateNeuropathologyParkinson disease dementiaMRCPsych Paper A

A 73-year-old man developed idiopathic Parkinson disease 12 years ago. He now has progressive dementia accompanied by recurrent visual hallucinations. Which neuropathological finding is most likely to underlie his cognitive syndrome?

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Correct answer: B — Widespread neocortical Lewy bodies and Lewy neurites containing alpha-synuclein

The correct answer is B. Dementia beginning many years after established Parkinson disease is Parkinson disease dementia. Its defining substrate is Lewy body disease, with alpha-synuclein-positive Lewy bodies and Lewy neurites extending into limbic and neocortical regions; recurrent visual hallucinations are also characteristic of the Lewy body spectrum. Alzheimer-type amyloid and tau pathology can coexist and modify severity, but isolated Alzheimer pathology is not the best answer. CAG-expanded huntingtin inclusions with caudate atrophy indicate Huntington disease. Prion deposition with thalamic neuronal loss suggests a prion disorder, while perivenular demyelination is characteristic of multiple sclerosis.

Reference: Irwin DJ, Hurtig HI. The Contribution of Tau, Amyloid-Beta and Alpha-Synuclein Pathology to Dementia in Lewy Body Disorders. J Alzheimers Dis Parkinsonism. 2018;8(4):444. https://pubmed.ncbi.nlm.nih.gov/30473927/