Figure 1: Chronic-active MS plaque in the cerebellar white matter and mechanisms of MS pathology (A) Luxol fast blue with periodic acid-Schiff's (LFB-PAS) histochemistry stain of cerebellar white matter in a secondary-progressive MS patient. Higher magnification shows the different pathological regions involving neurodegeneration (Ai-Aiii); (Ai) plaque core shows complete loss of myelin; (Aii) Dirty-appearing white matter (DAWM) shows demyelination with LFB pallor (arrowheads) with differential staining of infiltrating macrophages (arrows); (Aiii) Normalappearing white matter (NAWM) shows intact myelin integrity. (B) Bielschowsky histochemistry of a serial section of cerebellum from the same patient. (Bi) Plaque core shows complete loss of axons demonstrated by lack of silver staining; (Bii) DAWM shows axonal damage (arrowheads) with infiltrating macrophages (arrow), (Biii) NAWM shows less axonal damage compared to DAWM (arrowheads) with macrophages (arrow); scale bar for low magnification = 5mm; scale bar for high magnification = 50m