Motor function changes in the rat following severe spinal cord injury - Does treatment with moderate systemic hypothermia improve functional outcome?

Systemic hypothermia exerts neuroprotective effects following trauma and is chemia caused by vascular occlusion in the brain. In the spinal cord simila r effects have been demonstrated following ischemia after aortic occlusion. We have previously presented protective effects on several morphological p arameters in the early period after the injury, using an established spinal cord compression injury model and systemic hypothermia. In the present stu dy we have evaluated the effects on motor function following severe spinal cord compression trauma and treatment with moderate systemic hypothermia. Thirty Sprague Dawley rats were randomized into three groups: In group 1 (n = 4), the animals underwent a hypothermic procedure, including a 2 h hypot hermic period with a body temperature of 30 degrees C, following the initia l laminectomy. In group 2 (n = 12) a 50 g compression was applied to the sp inal cords for 5 min, after which the animals were kept under normothermic anesthesia for 3 h. In group 3 (n = 14), the animals underwent the same tra uma procedure as in group 2 and the same hypothermic procedure as in group 1. The animals were allowed to survive for 14 days, during which the motor function was recorded. This degree of trauma results in a non-reversible paraplegia, and the addit ion of systemic hypothermia as described above did not alter the neurologic al recovery as measured by two different methods of recording the motor fun ction up to two weeks after injury. All animals survived in group 1. Howeve r, the mortality rates in group 2 were 25% and in group 3, 50%, respectivel y, which mirrors the severity of the trauma. The application of systemic hypothermia and the lack of experimental therap eutic success highlight the difficulties of transferring experimental benef icial neuroprotective effects to a clinically useful treatment method. In t his experimental set-up the effects of the severe primary injury may oversh adow the effects of the secondary injury mechanisms, which limits the thera peutic possibilities of systemic hypothermic treatment.