摘    要： 目的调查新生大鼠缺氧缺血脑白质和灰质损伤的组织学和磁共振（MR）影像的变化。方法7日龄Wistar鼠（n=24）随机分为假手术组和实验组（右颈动脉结扎＋吸入8％氧1．5h）。在缺氧前、缺氧最后5-10分钟、缺氧后1h和24h行头部MR扫描获得吧和表面弥散系数（ADC）。结果1．5h缺氧将结束时，在缺氧缺血半球皮质下白质和顶部灰质可见ADC明显降低和他增高；缺氧缺血后1h，皮质下白质和顶部灰质ADC部分恢复，他持续增高，而缺氧缺血后24h，T2进一步增高。与灰白质类似的MRI改变相反，组织学检查显示：缺血半球白质不可逆细胞损伤发生早于灰质。在缺氧缺血后1h，缺血半球皮质下白质可见神经纤维稀疏或紊乱，并可见TUNEL阳性细胞增加，而在缺血半球顶部灰质区未见明显细胞损伤或TUNEL阳性细胞增加，到缺氧缺血后24h，灰白质均可见明显的损伤。结论在目前的新生鼠脑缺氧缺血模型，吧和ADC均能发现急性缺氧缺血脑白质和灰质水肿或损伤，但它们不能区分白质和灰质不同的病理变化，组织学上新生鼠脑白质比灰质更易遭受缺氧缺血损害。

 
关 键 词： 缺氧缺血  白质损伤  磁共振影像（MRI）  细胞凋亡

Histological and magnetic resonance imaging changes in cerebral gray and white matter damage following hypoxia-ischemia in neonatal rats
 
Affiliation: Department of Pediatff~s, The Second Clinical College, China Medical University, Shenyang 110004, China
 
Abstract: Objective To investigate changes of histology and magnetic resonance ( MR) imaging in the cerebral gray and white matter damage in neonatal rats following an episode of hypoxia-ischemia. Methods Seven days old Wistar rats ( n = 24 ) were subjected to either sham procedures or cerebral hypoxia-ischemia (HI, right carotid artery occlusion +8% oxygen for 1.5 h). Maps of T2 and the Apparent Diffusion Coefficient (ADC) of water were acquired prior to cerebral HI, within last 5-10 min of HI and at 1 h or 24 h after HI. Results Near the end of HI, ADC decreased and T2 increased in both parietal cortical gray and subcortical white matter of HI hemisphere. One hour after HI, ADC partially recovered but T2 remained increased and then increased further at 24 h post HI. In contrast to the similar MR responses in white and gray matter, histological evidence for irreversible cell damage occurred in white matter earlier than in gray matter within the HI hemisphere. At 1 h post HI, rarefied or disrupted nerve fibers and TUNEL-positive cells increasing were observed within subcortical white matter of HI hemisphere whereas neurons within the cortical gray matter appeared normal. By 24 h post HI, damage was apparent in both white and gray matter. Conclusions ADC and T2 can detect acute cerebral edema or damage following HI in both gray and white matter, but it can't distinguish the early irreversible histological tissue injury in white and gray matter
 
Keywords: Hypoxia-ischemia  White matter injury  MRI  Apoptosis