Hanstock C C, Faden A I, Bendall M R, Vink R
Department of Molecular Sciences, James Cook University, Townsville, Queensland, Australia.
Stroke. 1994 Apr;25(4):843-8. doi: 10.1161/01.str.25.4.843.
Diffusion-weighted magnetic resonance imaging (MRI) has been shown to be particularly effective in detecting early (0 to 4 hours) pathophysiological changes in localized brain regions after cerebral ischemia. The present study sought to establish whether diffusion-weighted MRI would be similarly effective in predicting outcome after traumatic brain injury.
Diffusion-weighted MRI images and T2-weighted MRI images were obtained over 4 hours after either moderate fluid percussion-induced traumatic brain injury or unilateral carotid ligation in rats.
Diffusion-weighted MRI images of traumatic brain injury demonstrated focal regions of image hypointensity as early as 1 hour after trauma. The relative diffusion coefficient in these hypointense regions was significantly increased (P < .005) by 4 hours after trauma compared with the noninjured hemisphere, but only in the transverse plane in the x direction. In contrast, induction of diffuse, nonfocal ischemia by unilateral carotid ligation resulted in scattered regions of hyperintensity with a significant (P < .001) decrease in relative diffusion coefficient as early as 1 hour after ligation compared with the noninjured hemisphere. This decrease exhibited no directionality.
We conclude that traumatic brain injury results in an increased water diffusion distance with the directionality indicative of bulk flow of extracellular fluid toward the lateral ventricles (vasogenic edema). In contrast, the decreased water diffusion distance with no apparent directionality observed in ischemia is most likely indicative of cytotoxic edema. Diffusion-weighted MRI therefore has the potential to differentiate cases of traumatic brain injury with no focal ischemia from those instances of traumatic brain injury in which focal ischemia is a complication.
扩散加权磁共振成像（MRI）已被证明在检测脑缺血后局部脑区的早期（0至4小时）病理生理变化方面特别有效。本研究旨在确定扩散加权MRI在预测创伤性脑损伤后的预后方面是否同样有效。
在大鼠中度液体冲击诱导的创伤性脑损伤或单侧颈动脉结扎后4小时内获取扩散加权MRI图像和T2加权MRI图像。
创伤性脑损伤的扩散加权MRI图像早在创伤后1小时就显示出图像低信号的局灶区域。与未受伤的半球相比，这些低信号区域的相对扩散系数在创伤后4小时显著增加（P <.005），但仅在x方向的横断面中如此。相比之下，单侧颈动脉结扎诱导的弥漫性、非局灶性缺血导致散在的高信号区域，与未受伤的半球相比，早在结扎后1小时相对扩散系数就显著降低（P <.001）。这种降低没有方向性。
我们得出结论，创伤性脑损伤导致水扩散距离增加，其方向性表明细胞外液向侧脑室的大量流动（血管源性水肿）。相比之下，在缺血中观察到的水扩散距离降低且无明显方向性最可能表明细胞毒性水肿。因此，扩散加权MRI有可能区分无局灶性缺血的创伤性脑损伤病例与局灶性缺血作为并发症的创伤性脑损伤病例。
