Fig. 8

SLYM is illustrated as a distinctive meningeal layer in the classical literature. (A) Reproduced sketch from Nabeshima et al., 1975 [20]. The sketch is based on examination of the meningeal region in studies of multiple mammals (mice, rats, chinchillas, rabbits, cats and Macaque monkeys) by electron microscopy and freeze-fracturing. Meningeal layers have been color-coded for clarity, without changing the original sketch. SLYM layer is already indicated as an intermedial layer between the arachnoid (ABC and ARLlayers) and pia, resting on top of a pial vessel (PBV). (B) Light microscopy image of a thin section stained with toluidine of meninges in the Norwegian landrace pig from Orlin et al., 1991 [21]. Orlin et al., compared this section to the sketch in the Nabeshima publication and the original labels and lines have not been changed. (C) Confocal cross-section of a pial vessel from this study is included to compare the structural details with our observations. The sketch below illustrates that SLYM forms the roof of the pial perivascular spaces