Demyelinating Neuropathology

The pathology of multiple sclerosis — active vs chronic plaques — and its fulminant variants
Antibody-mediated demyelination (NMOSD, MOGAD) and how it differs from MS on tissue
PML and other secondary / metabolic demyelination (osmotic demyelination, B₁₂, Marchiafava-Bignami)
The classic inherited leukodystrophies and their diagnostic buzzwords

The neuropathology view. Clinical diagnosis and treatment of MS/NMOSD live in the Demyelinating / Neuroimmunology notes; the inherited white-matter diseases are covered in Leukodystrophies.

Plaque	Histology	Stains
Active	Hypercellular; sheets of foamy macrophages full of myelin debris; perivascular lymphocytes; relative axonal sparing	LFB⁺ debris in macrophages; CD68⁺; axons preserved (neurofilament)
Chronic active (smoldering)	Gliotic center, rim of iron-laden macrophages/microglia at the expanding edge	Rim macrophages CD68⁺; iron stain rim⁺
Chronic inactive	Sharply demarcated, hypocellular, dense astrogliosis, oligodendrocyte and axon loss	LFB pale (myelin lost); GFAP⁺ gliosis
Shadow plaque	Partial remyelination — thin myelin, blurred border	LFB pale-but-present

Variant	Pathology	Buzzword
Marburg	Massive, destructive demyelination with axonal loss & edema	Fulminant, often fatal
Baló concentric sclerosis	Alternating rings of preserved and lost myelin	“Onion-bulb / tree-ring” on MRI
Tumefactive demyelination	Large solitary lesion mimicking tumor; macrophages, Creutzfeldt-Peters cells (reactive astrocytes with fragmented nuclei), open ring enhancement	Don't call it glioma — look for the macrophage sheet
ADEM	Perivenular (“sleeves of Virchow-Robin”) demyelination & inflammation; monophasic, post-infectious/vaccinal	Perivenular vs confluent (MS)

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