Combination of decompressive craniectomy and mild hypothermia ameliorates infarction volume after permanent focal ischemia in rats

Background and Purpose-Both hypothermia and decompressive craniectomy (DC) have been shown to reduce ischemic injury in experimental middle cerebral a rtery (MCA) infarction. This study was designed to evaluate the effect of c ombined 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 degreesC) was induced 1 hour after MCAO for 5 hours; normothermia was maintained in group B. After 6 hours of survi val, 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 p erformed I 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 g roup F (control). Infarction size and neurological performance after 24 hou rs 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%; gro up B, 20.2 +/- 2.6%; P < 0.01). Twenty-four hours after MCAO, infarction si ze 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 s ignificantly reduced and neurological performance was significantly improve d in animals treated by DC (group C, 11.8 +/- 3.4; P < 0.001). Combined hyp othermia 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 neu rological outcome in MCA infarction in rats. Temporary mild hypothermia del ays infarct evolution but does not significantly reduce definite infarction size or improve neurological outcome. Combined hypothermia and DC yield si gnificant additional benefit.