The mechanism of spinal cord cavitation follwing spinal cord transection. Part 2. Electron microscopic observations.

The authors report their findings by electron microscopy after microsurgical subpial spinal cord transection in dogs. After cord transection, conspicuous myelin microcysts are formed in a background of otherwise intact cord tisue at a distance of 1 to 2 mm from the cut end of the cord, both proximal and distal to the transection, Seen through the electron microscope, the microcysts iss a myelin sac distended by fluid under pressure, containing a swollen axon filled with excessive axoplasmic organelles; that is, a terminal club. Later the microcysts and terminal clubs rupture. The large spaces within the microcysts are opened to heretofore small extracellular spaces and the spinal cord tissues are destroyed. Thus, microcysts are precursors of large cavitites seen at the ends of transcreted cord stumps. The formation of microcysts and their subsequent rupture, which leads to cord cavitation, is interpreted as an inherent response of cord tissue to injury, and the result of an abortive attempt at cord regeneration.