Figure 2. CNS Pattern of Neuronal Loss and Inflammation in PERM.

Tissue damage and inflammation predominantly affected GlyR-rich CNS regions, following a pallido-nigro-dentato-bulbar-spinal degeneration pattern: globus pallidus and hypothalamus (A), substantia nigra and nuclei within the medulla oblongata and reticular formation (B), cerebellar dentate nucleus (C), and the ventral and dorsal horn of the spinal cord (D). Neuronal loss and gliosis with chromatolytic neurons, single vacuolized neurons, and axonal spheroids (first column with details in boxes; H&E) were detected particularly in GlyR dense areas (second column with details and controls [CO] in boxes; GlyR immunohistochemistry [IHC]). Neuronal GlyR (mAb4a) expression was reduced in the ventral and dorsal horn of the spinal cord, compared with 2 age-matched controls (D, showing one control; see details in Figure 3, C and D). Inflammatory infiltrates were spatially and quantitatively (cells per mm²) visualized by overlaying density maps of IHC with leucocyte common antigen (LCA) and respective H&E-stained sections (third column). QuPath Version 0.3.2 was used to perform positive cell detection of LCA/CD45-positive immune cells. Gaussian-weighted density maps were produced to visualize and quantify positive cells with color codes. These areas showed the highest average amount of immune cells per mm² (including focal maximum): medulla oblongata, 16.06 (115, close to nucleus ambiguus); spinal cord, 14.32 (49, dorsal horn); basal ganglia, 12.99 (139, globus pallidus); pons, 12.32 (179, nuclei in tegmentum and basis); cerebellum, 11.71 (101, dentate nucleus); mesencephalon, 5.33 (74, medial substantia nigra); and lateral substantia nigra, (37). HLA-DR⁺ microglial activation was prominent in affected regions and correlated well with tissue damage and LCA positivity (fourth column). Scale bars: 2 mm. PERM = progressive encephalomyelitis with rigidity and myoclonus.