Demyelinating Diseases USMLE Step 1 Practice Question
A 45-year-old woman with multiple sclerosis presents with acute severe vertigo, horizontal nystagmus, and intention tremor. Vital signs show BP 128/82, HR 88, RR 16, Temp 37.2°C, SpO2 98% on room air. MRI brain reveals a new T2/FLAIR hyperintense lesion in the right cerebellar hemisphere with no contrast enhancement. CSF oligoclonal bands are positive. She denies fever or recent infections. High-dose intravenous methylprednisolone is initiated. Which pathophysiologic mechanism best explains demyelination in her lesion?
Answer choices
- AToxic accumulation of myelin breakdown products
- BPrimary axonal degeneration with secondary demyelination
- CIschemic necrosis from vascular occlusion
- DImmune-mediated demyelination with preserved axonsCorrect answer
- EViral-induced cytolysis of oligodendrocytes
- FComplement-mediated astrocyte destruction by anti-aquaporin-4 antibodies
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