A 45-year-old woman presents with optic neuritis followed months later by bilateral leg weakness and loss of bladder control. MRI shows periventricular white matter lesions with ovoid plaques perpendicular to the lateral ventricles (Dawson fingers). Histology of an active plaque would show:

• A Perivascular lymphocytic infiltrate, reactive astrogliosis, and loss of myelin with relative axonal preservation ✓
• B Axonal degeneration with preservation of myelin sheaths
• C Amyloid plaques and neurofibrillary tangles
• D Granulomatous inflammation with Langhans giant cells

Explanation

Multiple sclerosis (MS) plaques are characterized by perivascular T-cell and macrophage infiltration, selective loss of myelin sheaths with relative preservation of axons (initially), and reactive astrogliosis. Active plaques show ongoing myelin destruction with foamy macrophages laden with myelin debris at the edges. Chronic plaques show dense astrocytic scarring (sclerosis) and eventual axonal loss contributing to irreversible disability. This pattern distinguishes MS from primary axonopathies.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.