Fig. 1

Pathological findings of the AM (× 400) in a representative case of hyperplastic AM (a), and non-hyperplastic AM (b). The arachnoid membrane includes a barrier cell layer beside the dura matter (white arrow). The fibroblast cells increased and localized beside the inner layer (black arrow). The membrane thickness was measured as the black bar. Immunostaining of the AM (× 400); Macrophages were stained with CD68 (c), CD86 (d), and/or CD206 (e). The number of positive cells for CD68, CD86, and CD206 staining were counted (black arrow). AM: arachnoid membrane