X-irradiation of the contusion site improves locomotor and histological outcomes in spinal cord-injured rats

We have determined whether X-irradiation of the injury site can oppose tiss ue loss and improve recovery of locomotor function following contusion inju ry of the spinal cord. Contusion injury was produced in rats at the level o f T10 with a weight drop device. Localized X-irradiation (20 Gy) of the inj ury site was performed at 20 min and 1, 2, 4, 7, and 17 days postinjury. Lo comotor recovery was then determined with the 21-point Basso, Beattie, and Bresnahan (BBB) scale. X-irradiation enhanced recovery of locomotor functio n during a subsequent 6-week observation period when administered 20 min an d I or 2 days following contusion injury (final BBB score similar to7-8). X -irradiation at 4-17 days postinjury did not significantly affect final loc omotor scores compared with unirradiated rats (final BBB score similar to2) , in marked contrast to previous studies where X-irradiation applied only a t 17-18 days benefitted transection injury. The extent of recovery was dire ctly related to measurements of sparing of spinal cord tissue at the contus ion center. Because the treatment time window occurred earlier in contusion than reported for transection injury, the results suggest that contusion i njury rapidly initiates underlying radiation-sensitive processes that occur only following a delay of several weeks after transection injury. Further optimization of X-ray treatment may lead to a useful therapeutic modality f or use in spinal cord contusion injury. (C) 2001 Academic Press.