GRADED HISTOLOGICAL AND LOCOMOTOR OUTCOMES AFTER SPINAL-CORD CONTUSION USING THE NYU WEIGHT-DROP DEVICE VERSUS TRANSECTION

Injury reproducibility is an important characteristic of experimental models of spinal cord injuries (SCI) because it limits the variability in locomotor and anatomical outcome measures. Recently, a more sensit ive locomotor rating scale, the Basso, Beattie, and Bresnahan scale (B BB), was developed but had not been tested on rats with severe SCI com plete transection. Rats had a 10-g rod dropped from heights of 6.25, 1 2.5, 25, and 50 mm onto the exposed cord at T10 using the NYU device. A subset of rats with 25 and 50 mm SCI had subsequent spinal cord tran section (SCI + TX) and mere compared to rats with transection only (TX ) in order to ascertain the dependence of recovery on descending syste ms. After 7-9 weeks of locomotor testing, the percentage of white matt er measured from myelin-stained cross sections through the lesion cent er was significantly different between all the groups with the excepti on of 12.5 vs 25 mm and 25 vs 50 mm groups. Locomotor recovery was gre atest for the 6.25-mm group and least far the 50-mm group and was corr elated positively to the amount of tissue sparing at the lesion center (p < 0.0001). BBB scale sensitivity was sufficient to discriminate si gnificant locomotor differences between the most severe SCI (50 mm) an d complete TX (p < 0.01). Transection following SCI resulted in a drop in locomotor scores and rats were unable to step or support weight wi th their hindlimbs (p < 0.01), suggesting that locomotor recovery depe nds on spared descending systems. The SCI + TX group had a significant ly greater frequency of HL movements during open field testing than th e TX group (p < 0.005). There was also a trend for the SCI + TX group to have higher locomotor scores than the TX group (p > 0.05). Thus, sp ared descending systems appear to modify segmental systems which produ ce greater behavioral improvements than isolated cord systems. (C) 199 6 Academic Press, Inc.