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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1．5 h)。在缺氧前、缺氧最后5-10分钟、缺氧后1 h和24 h行头部MR扫描获得12和表面弥散系数(ADC)。结果 1．5 h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T2增高;缺氧缺血后1 h,皮质下白质和顶部灰质ADC部分恢复,T2持续增高,而缺氧缺血后24 h,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1 h,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24 h,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,T2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。
Objective To investigate the changes of histopathology and magnetic resonance (MR) images in neonatal rats with hypoxic-ischemic white matter and gray matter damage. Methods 7-day-old Wistar rats (n = 24) were randomly divided into sham operation group and experimental group (right carotid artery ligation + inhalation of 8% oxygen for 1.5 h). Prior to hypoxia, hypoxia last 5-10 minutes, 1 h and 24 h after hypoxia line head MR scan obtained 12 and surface diffusion coefficient (ADC). Results At the end of 1.5 h hypoxia, the ADC of hypodermic white matter and the top gray matter of the hypoxic-ischemic hemisphere was obviously decreased and T2 was increased. The ADC of the subcortical white matter and the top gray matter partly recovered 1 h after hypoxia-ischemia, and T2 Continued to increase, and 24 h after hypoxia-ischemia, T2 further increased. In contrast to similar MRI changes of gray matter, histological examination showed that ischemic hemisphere white matter irreversible cell injury occurred earlier than gray matter. At 1 h after hypoxia and ischemia, nerve fibers were sparse or disordered in the subcortical white matter of ischemic hemisphere, and TUNEL-positive cells were found to be increased. However, no obvious cell injury or TUNEL-positive cells were found in the top gray matter area of the ischemic hemisphere, 24 h after oxygen ischemia, visible white matter were significantly damaged. Conclusions In the current neonatal model of hypoxic-ischemic brain injury, both T2 and ADC can detect edema or injury of white matter and gray matter of acute hypoxic-ischemic brain. However, they can not distinguish the different pathological changes of white matter and gray matter. Histologically, White matter is more vulnerable to hypoxic-ischemic damage than gray matter.