Fig. 3

Neuroimaging and histopathology of Case 2. a T1 axial post-contrast image shows diffuse meningeal enhancement. b T1 post-contrast sagittal image shows possible enhancement along right optic nerve sheath (arrow). c Histologic section of meninges, with arachnoid portion on the left and dura on the right. A chronic inflammatory infiltrate is concentrated in the leptomeninges (H&E stain, original magnification, ×100). d Higher magnification exhibits a mixed chronic inflammatory infiltrate, including abundant plasma cells (p), as well as lymphocytes (l) and macrophages (m) (H&E stain, original magnification, ×400). e IgG4 immunostain highlights numerous plasma cells (original magnification, ×100). f Higher magnification reveals >40 IgG4-positive plasma cells per high-power field, comprising about 40 % of the total plasma cell population (original magnification, ×400)