Lövblad K O, Bassetti C
Departments of Neuroradiology, University of Bern, Switzerland.
Stroke. 2000 Feb;31(2):539-42. doi: 10.1161/01.str.31.2.539.
BACKGROUND; Traditionally the diagnosis of brain death is established on the basis of a combination of clinical signs and paraclinical methods. Diffusion-weighted MRI is a new method sensitive to cerebral ischemia. Its value in brain death has not been demonstrated until now.
A patient was referred to MRI with suspicion of a brain stem stroke. Echo-planar whole-brain, multislice, diffusion-weighted MRI was performed in addition to conventional sequences and MR angiography sequences. In addition to the extensive bilateral hyperintensities observed on T2-weighted images, diffusion-weighted MRI showed diffuse hyperintensities involving both hemispheres as well as a severe drop in the apparent diffusion coefficient in both affected hemispheres. There was also transtentorial herniation with compression of the brain stem as well as absence of flow voids on the T2-weighted images and absence of intracranial vessels on MR angiography. On the basis of the clinical and imaging findings, it was concluded that the patient was in a state of brain death. The patient died the same day.
With the use of new fast techniques such as diffusion-weighted imaging, now MRI can not only display anatomic changes associated with severe brain suffering but can also demonstrate ultrastructural changes secondary to brain death and differentiate them from edematous changes seen on T2-weighted images.
背景；传统上，脑死亡的诊断是基于临床体征和辅助检查方法的综合判断。扩散加权磁共振成像（Diffusion-weighted MRI）是一种对脑缺血敏感的新方法。到目前为止，其在脑死亡中的价值尚未得到证实。
一名因疑似脑干卒中被转诊至磁共振成像检查的患者。除了常规序列和磁共振血管造影序列外，还进行了回波平面全脑多层扩散加权磁共振成像检查。除了在T2加权图像上观察到广泛的双侧高信号外，扩散加权磁共振成像显示双侧大脑半球均有弥漫性高信号，且两个受累半球的表观扩散系数严重下降。还存在小脑幕切迹疝伴脑干受压，T2加权图像上无血流空洞，磁共振血管造影显示颅内血管缺失。根据临床和影像学表现，得出该患者处于脑死亡状态的结论。患者于同日死亡。
通过使用扩散加权成像等新的快速技术，现在磁共振成像不仅可以显示与严重脑损伤相关的解剖学变化，还可以显示脑死亡继发的超微结构变化，并将其与T2加权图像上的水肿变化区分开来。
