Electron microscopy of astrocyte changes and subtypes in traumatic human edematous cerebral cortex: a review.

The astrocyte subtypes in moderate and severe human brain trauma complicated with subdural hematoma or hygroma are described. Clear and dense edematous and hypertrophic reactive astrocytes are distinguished in severe vasogenic brain edema. Swollen perineuronal astrocytes appear compressing and indenting dark, degenerated pyramidal and nonpyramidal nerve cells. Glycogen-depleted and glycogen-rich astrocytes also are seen. Reactive hypertrophic astrocytes exhibit increased amounts of dilated smooth and rough endoplasmic reticulum, microtubules, and gliofilaments. Perisynaptic astrocyte ensheathments of neuropil synaptic contacts are lost, and the perivascular astrocyte end-feet appear dissociated from the capillary basement membrane. The interastrocytary gap junctions appear fragmented.