Background and purpose: Both hypothermia and decompressive craniectomy (DC) have been shown to reduce ischemic injury in experimental middle cerebral artery (MCA) infarction. This study was designed to evaluate the effect of combined DC and hypothermia on infarction size and neurological outcome in a rat model of MCA occlusion (MCAO).
Methods: MCAO was performed in 72 Wistar rats assigned to groups A through F. In group A, mild hypothermia (32 degrees C) was induced 1 hour after MCAO for 5 hours; normothermia was maintained in group B. After 6 hours of survival, infarction size was calculated for animals of groups A and B. In group C, DC alone was performed 4 hours after MCAO; hypothermia without DC was performed 1 hour after MCAO and maintained for 5 hours in group D. Combined DC and hypothermia were performed in group E. No therapy was performed in group F (control). Infarction size and neurological performance after 24 hours were used as study end points (groups C through F).
Results: Permanent postischemic hypothermia significantly reduced infarction size 6 hours after MCAO compared with controls (group A, 6.6+/-2.4%; group B, 20.2+/-2.6%; P<0.01). Twenty-four hours after MCAO, infarction size was not significantly reduced by hypothermia alone (group D, 21.9+/-3.6%). Compared with controls (group F, 23.3+/-3.3%), infarction size was significantly reduced and neurological performance was significantly improved in animals treated by DC (group C, 11.8+/-3.4; P<0.001). Combined hypothermia and DC resulted in additional reduction of infarction size (group E, 9.1+/-2.4%) and improved neurological score (P<0.01).
Conclusions: Early DC significantly reduces infarction size and improves neurological outcome in MCA infarction in rats. Temporary mild hypothermia delays infarct evolution but does not significantly reduce definite infarction size or improve neurological outcome. Combined hypothermia and DC yield significant additional benefit.