Beneficial effects of modest systemic hypothermia on locomotor function and histopathological damage following contusion-induced spinal cord injury in rats

Object. Local spinal cord cooling (LSCC) is associated with beneficial effe cts when applied following ischemic or traumatic spinal cord injury (SCI). However, the clinical application of LSCC is associated with many technical difficulties such as the requirement of special cooling devices, emergency surgery, and complicated postoperative management, if hypothermia is to be considered for future application in the treatment of SCI, alternative app roaches must be developed. The objectives of the present study were to eval uate 1) the relationship between systemic and epidural temperature after SC I; 2) the effects of modest systemic hypothermia on histopathological damag e at 7 and 44 days post-SCI; and 3) the effects of modest systemic hypother mia on locomotor outcome at 44 days post-SCI. Methods. A spinal cord contusion (12.5 mm at T-10) was produced in adult ra ts that had been randomly divided into two groups. Group 1 rats (seven in E xperiment 1; 12 in Experiment 2) received hypothermic treatment (epidural t emperature 32-33 degrees C) 30 minutes postinjury for 4 hours; Group 2 rats (nine in Experiment 1; eight in Experiment 2) received normothermic treatm ent (epidural temperature 37 degrees C) 30 minutes postinjury for 4 hours. Blood pressure, blood gas levels, and temperatures (epidural and rectal) we re monitored throughout the 4-hour treatment period. Twice weekly assessmen t of locomotor function was performed over a 6-week survival period by usin g the Basso-Beattie-Bresnahan locomotor rating scale. Seven (Experiment 1) and 44 (Experiment 2) days after injury, animals were killed, perfused, and their spinal cords were serially sectioned. The area of tissue damage was quantitatively analyzed from 16 longitudinal sections selected from the cen tral core of the spinal cord. Conclusions. The results showed that 1) modest changes in the epidural temp erature of the spinal cord can be produced using systemic hypothermia; 2) m odest systemic hypothermia (32-33(C degrees)) significantly protects agains t locomotor deficits following traumatic SCI; and 3) modest systemic hypoth ermia (32-33 degrees C) reduces the area of tissue damage at both 7 and 44 days postinjury. Although additional research is needed to study the therap eutic window and long-term benefits of systemic hypothermia, these data sup port the possible use of modest systemic hypothermia in the treatment of ac ute SCI.