Synaptic degenerative changes in human traumatic brain edema. An electron microscopic study of cerebral cortical biopsies.

The cerebral cortex of 9 patients with complicated brain trauma has been examined with the transmission electron microscope to study the distinctive degenerative synaptic changes induced by brain injury and associated vasogenic, moderate or severe, brain edema. The brain injury and the hematogenous edema fluid accumulated in the dilated extracellular space of cerebral cortex neuropil induced swelling and shrinkage of pre- and postsynaptic structures, increased amount of presynaptic axoplasmic granular substance and clumping, enlargement and depletion of synaptic vesicles. In severe brain edema, swollen and shrunken presynaptic endings with discontinuous limiting plasma appeared separated from the postsynaptic structures and detached from glial ensheathment (synaptic disassembly). Post-synaptic shaft dendrites and their spines showed swelling and vacuolization. Fragmen-tation and atrophic changes of spine apparatus were found in the dendritic spines. The clear and dark types of degeneration were observed in most cases examined, in both preand/or postsynaptic structures. Filamentous hypertrophy of presynaptic endings was observed only in two cases. Osmiophylic bodies, necrotic membranes, lipid inclusions and glycogen granules were seen in the synaptic terminals. Disappearance of synaptic densities was evident in some cases. Phagocytosis of isolated presynaptic endings or of the entire synaptic contacts by astrocytes, microglial cells and by non-nervous invading cells, such as monocytes and macrophages, was found.