The process of decompaction and myelin removal after C7 ventral root avulsion in the cat

An electron microscopical study was carried out on the ventral horn in orde r to investigate the microvascular changes after C7 ventral root avulsion i n cats. Endothelial cells: At 2 days after avulsion the endothelial cells contained vacuoles filled with fibrous-like substances. After 14 days the endothelia l phagosomes also contained myelin sheath-like and "soap-bubble" structures . Tight junctions between the endothelial cells remained present without ex ception. From 14 up to 90 days, intraluminal debris was observed. Edema and glia: From 2 up to 30 days after avulsion perivascular edema was noted around blood vessels and polymorphonuclear granulocytes were found ma inly in the peri-endothelial space. Eight days after avulsion, the number o f astrocytic processes around the blood vessels and the phagocytic activity of perivascular cells increased. Myelin sheath-like structures were encoun tered in phagosomes of the pericytes. After 14 days the distribution of ast rocytic processes around the blood vessels had stabilized and remained so u ntil day 90 after avulsion. In the same period the phagocytic activity decr eased, and the myelin sheath-like material in the perivascular cell phagoso mes gradually disappeared. The amount of microglial cells around the blood vessels showed an increase after 30 days survival and then stabilized. These results indicate transport of debris from the neuropil across the end othelial cells into the blood vessel lumen after ventral root avulsion.