Correlative analyses of lesion development and functional status after graded spinal cord contusive injuries in the rat.

The development of both histopathological changes and functional deficits was quantitatively assessed after mild, moderate, and severe spinal cord contusive injuries. The cross-sectional area of the spinal cord at the epicenter (region of maximal damage) and the areas of hemorrhage, lesion, and remaining gray and white matter were determined from 15 min to 8 weeks after injury. From 24 h to 8 weeks after injury, functional deficits were quantified using a combined behavioral score (CBS) based on the results from a number of behavioral tests of function. Regression analysis was used to examine the correlations between the amount of residual white matter and both the severity of contusive impact and the functional deficit over time after injury. The area of hemorrhage at 15 min and 24 h was greater in the mild and moderate injury groups than after the severe contusive injury. Significant loss of gray and white matter occurred primarily between 24 h and 1 week after injury along with concomitant increases in the area of lesion. In the mild injury group the rate of lesion development appeared slower than that in the moderate and severe injury groups and significant white matter loss continued to occur between 1 and 4 weeks after injury. Behavioral tests of functional deficit were performed at 24 h and weekly thereafter. The development of stable functional deficits was observed beginning at 3 weeks after injury. There was a significant correlation between residual white matter and the degree of initial injury at 24 h after injury and all subsequent time points. However, a significant correlation between residual white matter and functional deficit, as measured by the CBS, was not observed at 24 h or 1 week but did develop by 4 weeks after injury.