20 Chapter 1 Inac�ve Ac�ve Preac�ve Schema�c PLP HLA-DR Chronic Ac�ve (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k) (l) Figure 3. Characterisation of white matter MS lesions. MS lesions are characterised mainly on the presence of activated microglia/macrophages, marked by HLA-DR staining (i-l), demarcated by the dotted lines, and the preence of myelin, marked by PLP staining (e-h). Pre-active lesions (a,e,i) are microglial clusters (arrow) in the normal appearing white matter (NAWM). Active lesions (b,f,j) are characterised on absence of myelin and the presence of high numbers of activated microglia/macrophages. Chronic active lesions (c,g,k) have a demarcated rim of activated microglia/macrophages around a centre of inactivity marked by loss of myelin. In inactive lesions (d,h,l) activity subsides and the area is left with a plaque with no myelin, and astroglial scarring. lesions there are almost no signs of inflammatory cells. Then there is some evidence that some lesions show signs of remyelination where oligodendrocyte precursor cells remyelinate naked axons, although the new myelin has other characteristics such as thinner sheaths170. In the grey matter of the brain MS lesions are classified based on their anatomical location rather than on their degree of inflammation due to the lack of apparent neuroinflammation that is present in the cortex of the brain171 (Figure 4). Lesions that comprise both the white and grey matter are classified as leukocortical lesions (type I), sometimes the white matter of these lesions show clear signs of inflammation which gradually decreases when crossing to the grey matter172. Lesions that are purely within the grey matter are classified as intracortical lesions (type II)172. Areas of demyelination along the outer border of the cortex area are classified as subpial lesions (type III) and are the most commonly observed172. Lesions that extend from the surface of the brain to the border of the white and grey matter are classified as transcortical (type IV)2,172. I Grey ma�er White ma�er II III IV Figure 4. Grey matter lesions in MS. Lesions are classified by their location and spread in the grey matter. Type I comprises both white and grey matter. Type II lesions are surrounded by grey matter. Type III lesions are subpially located along the grey matter. Type IV lesions comprise the whole width of the grey matter but do not cross into the white matter2.
RkJQdWJsaXNoZXIy MTk4NDMw