Experimental spinal cord injury: qualitative and quantitative histopathologic evaluation

This study involved a morphometric analysis of an experimental model of spinal cord injury. The spinal cords of rats were injured by a weight drop at T8 level. Animals were sacrificed 4 weeks after injury, and histopathologic examination of the spinal cords was carried out qualitatively and also quantitatively with the aid of computer-assisted morphometry. Total cross-sectional areas of residual gray and white matter were determined at five regularly spaced intervals through the injured cord segment. The histologic findings were correlated with height of weight-drop and motor recovery in the hind limbs at 4 weeks postinjury. The weight-drop injury was found to produce a longitudinally asymmetrical cavitary defect, which was better assessed by a series of cross-sectional profiles than by a single histologic cross-section through the epicenter (site of maximal impact) of the cord injury. There was a strong correlation between height of weight-drop and amount of residual tissue (gray and white matter) at the epicenter. A correlation was also found between height of weight-drop and a composite of residual tissue evaluated at multiple levels through the injury site. By comparison with cross-sectional morphometry at the epicenter, multiple cross-sections, reflecting volume of residual tissue in the longitudinal extent of injury, showed greater statistical correlation with functional (behavioral) outcome. This "volumetric" assessment of the total region of injury is therefore recommended as preferable to a histopathologic evaluation limited to the epicenter.