Fig. 3

Pathological findings in pneumococcal meningitis. Short illustration of histological abnormalities. The score is based on severity of each lesion and also extensiveness/multifocality of the histological abnomalities. a–c Meningeal inflammation: Little (a), moderate (b) and extensive (c) infiltration of neutrophils in the sub-arachnoid space. d–f Meningeal inflammation components: mainly neutrophils (d), mainly macrophages (e) and mix of neutrophils and macrophages (f) in a late phase case. g–i Infarction: focal small hypoxic-ischemic neuronal injury with eosinophilic neurons (g), focal large established infarct with tissue degeneration and infiltration of inflammatory cells (h) and one of multifocal large infarcts with gliosis in the late phase (i). j–l Haemorrhage: focal small perivascular haemorrhages (j), multifocal parenchymal moderate size haemorrhages (k) and multifocal large haemorrhage (l). m–o Large-medium size meningeal arterial inflammation in the early phase: mild (m, admission day 3) and severe sub-endothelial inflammation with near obstruction of vascular lumen in n (admission day 3). In o (admission day 3), vascular inflammation extends into the tunica media with destruction of elastica layer. p–r Pathological changes of large-medium size arteries in the late phase: broadened tunica intima with formation of connective tissue infiltrated by various quantities of mixed inflammatory cell composed of macrophages, lymphocytes, plasma cells and neutrophils (p, admission day 18), reactive change of artery with thickening of tunica intima with near obstruction of lumen (q, admission day 21), and reactive change of artery with tunica media degeneration and dilation (r, admission day 30). s–u Pathological changes of small brain parenchymal vessels: inflammation (s), total destruction and degeneration (t) and thrombosis (u). v–x Thrombosis and parenchymal infiltration of inflammatory cells: thrombosis of artery with total obstruction (v), parenchymal infiltration of inflammatory cells (w, neutrophils are marked with asterick) and a small abscess in basal ganglia (x)