SEVERE CONTROLLED CORTICAL IMPACT IN RATS - ASSESSMENT OF CEREBRAL EDEMA, BLOOD-FLOW, AND CONTUSION VOLUME

Controlled cortical impact (CCI) is a contemporary model of experiment al cerebral contusion. We examined the cerebrovascular and neuropathol ogic effects of a severe CCI in rats. The utility of magnetic resonanc e imaging (MRI) for the assessment of contusion volume after severe CC I was also established. Severe CCI(3.0 mm depth, 4 m/sec velocity) to the left (L) parietal cortex was produced in anesthetized (isoflurane/ N2O/O-2), intubated, and mechanically ventilated male Sprague-Dawley r ats (n = 58). Physiologic parameters were controlled. The time coure o f alterations in edema [L-R% brain water (% BW) in 3-mm coronal sectio ns through injured and contralateral hemispheres, wet-dry weight] was evaluated at 2 h, 24 h, 48 h, and 7 days posttrauma. Local cerebral bl ood flow (ICBF, measured in 8 structures in each hemisphere by autorad iography) was evaluated at 2 h, 24 h, and 7 days. Contusion volume (me asured by histology and image analysis) was assessed at 14 days and me asured in 6 rats by both MRI and histology. The survival rate after se vere CCI was 96.2%. The L-R difference in % BW increased to 1.69 +/- 0 .18% at 2 h, 3.00 +/- 0.08% at 24 h, 2.69 +/- 0.09% at 48 h, and 0.94 +/- 0.21% at 7 days. These values all differed from the control (p < 0 .05). The % BW was greater at 24 h and 48 h than at 2 h and 7 days (p < 0.05). Marked reductions in lCBF were limited to structures in the i njured hemisphere and were observed in the parietal cortex (2 and 24 h ), subcortical white matter (2 and 24 h), and hippocampus (2 h), (p < 0.05) vs control rats. In the contusion core, ICBF was 19.4 +/- 8.8 mL 100 g(-1) min(-1) at 24 h (p = 0.011 vs normal). Necrosis was seen in large portions of the parietal cortex and subcortical white matter, a nd portions of the hippocampus and thalamus. Contusion volume was 47.8 +/- 9.2 mm(3), which represented 14.4 +/- 2.1% of the traumatized hem isphere. Estimates of contusion volume by MRI and histology were close ly correlated (r = 0.941, p < 0.017). Severe CCI in rats is accompanie d by contusion, reproducible edema, and marked hypoperfusion, involvin g over 14% of the injured hemisphere, and can be produced with minimal mortality. T-2-weighted MRI successfully and noninvasively identifies contusion volume in this model.