H M Bramlett, E J Green, W D Dietrich, R Busto, M Y Globus, M D Ginsberg

The purpose of this study was to determine the degree of sensorimotor and cognitive protection conferred by posttraumatic brain hypothermia. Baseline measurements were taken on sensorimotor tasks involving forelimb placing and beam-walking, as well as on a spatial navigational task utilizing the water maze. Twenty-four hours after the last baseline measurements, normothermic (37 degrees C) animals were subjected to a fluid percussion pulse (1.9-2.4 atm) over the right parietal sensorimotor cortex. Following trauma, brain temperature was maintained for 3 h at either normothermic (37 degrees C, group TBI-N, n = 12) or hypothermic levels (30 degrees C, group TBI-H, n = 11). Shams (n = 10) underwent all surgical procedures including posttraumatic brain injury (TBI) temperature manipulation, but were not subjected to the fluid percussive pulse. Beam-walking and forelimb placing measures were begun 24 h post-TBI and continued for 2 weeks. Animals were tested on the water maze task for 2 days beginning 24 h post-TBI. TBI produced substantial deficits in contralateral limb placing, which recovered over approximately one week. Hypothermia provided partial protection from these deficits, with TBI-H animals exhibiting intermediate scores that differed from both sham and TBI-N animals (p < 0.03). In the water maze, there was a distinction between groups in the ability to navigate 48 h after TBI. TBI-N animals performed significantly worse than sham and TBI-H animals (both p < 0.01), whereas there was no significant difference between the scores of sham and TBI-H animals. The present data demonstrate that moderate postinjury brain hypothermia can provide protection from sensorimotor and cognitive behavioral deficits as well as neuropathology in a model of traumatic brain injury associated with early neuronal and microvascular injury.