The Sub-microscopic Pathology of Brain Extracellular Space in Some Neuropathological Conditions. A Review

Abstract

The enlargement and content of perivascular and extracellular spaces in experimental and human material have been reviewed. The human edematous cerebral cortex associated to vascular anomaly, congenital hydrocephalus, brain trauma, and brain tumors were examined by transmission electron microscopy, using cortical biopsies of frontal, parietal, and temporal cortex. In congenital hydrocephalus, the pre-existing extracellular space that features immature cerebral cortex appears notably enlarged and occupied by electron transparent, non-proteinaceous interstitial edema fluid, due to the abnormal accumulation of non-circulating cerebrospinal fluid. In severe human brain trauma associated to subdural or estradural hematomas and brain tumors, the distended extracellular space contains either electron lucid non-proteinaceous edema fluid, and electron dense proteinaceous edema fluid, fibrinoid material, exosomes or extracellular vesicles, extracellular mitochondria, hemorrhagic foci, and non-nervous invading cells, such as phagocytic astrocytes, macrophages, microglia, and monocytes. In brain tumors, the widened extracellular space shows mainly electron dense proteinaceous edema fluid, and bundles of fibrinoid material and extracellular vesicles.