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| Ischemic lesions on MRI and histological outcomes after different transient periods of focal ischemia in rabbits |
| WANG Zhi-hong, LIU Huai-jun, SHI Zhao-xia, QIN Rui-ping, WANG Cang-hai |
| Second Hospital of Hebei Medical University, Shijiazhuang 050000, China |
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Abstract Objective: To investigate the time course of ischemic changes on MRI(including DWI and T2WI) after different brief periods of focal brain ischemia in rabbits and to evaluate the histopathological outcomes in the regions of DWI abnormalities. Methods: Thirty rabbits were subjected to 7 minutes(n=10); 30 minutes(n=10) short time obliteration of middle cerebral arterial occlusion and sham operation(n=10). MRI(including DWI and T2WI) were performed during and before occlusion; 5min after occlusion and at 0.5, 2, 6, 12, 24, 48 and 72 hours of reperfusion. After the last MRI study at 72 hours of reperfusion, the brains were evaluated by histopathology. Results: No MRI abnormalities were observed in the sham-operated rabbits. In the 7-minute and 30-minute groups, the perfusion deficits and DWI hyperintensities that occurred during occlusion disappeared shortly after reperfusion. The DWI and T2WI results remained normal in the 7-minute group, whereas secondary DWI hyperintensity and T2WI abnormalities developed at the 6~12 hour observation point in the 30-minute group. Histological examinations demonstrated neuronal necrosis in the two groups, but the number of necrotic neurons was significantly higher in the 30-minute group than in the 7-minute group(P<0.001). Conclusions: Transient or permanent resolution of initial DWI lesions after reperfusion depends on the duration of ischemia. Transient resolution of DWI lesions was associated with widespread neuronal necrosis; moreover, permanent resolution of DWI lesions did not necessarily indicate complete salvage of brain tissue from ischemic injury. These results may help to explain the neurological deficits in some patients who have normal DWI results after cerebral ischemia and cognitive deficits in some patients who experienced transient ischemic attacks.
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Received: 18 November 2009
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Corresponding Authors:
LIU Huai-jun
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2010, Vol. 21 
