Mazumdar Avi, Mukherjee Pratik, Miller Jeffrey H, Malde Hiten, McKinstry Robert C
Neuroradiology Section, Mallinckrodt Institute of Radiology, Campus Box 8131, Washington University Medical Center, 510 South Kingshighway Boulevard, St. Louis, MO 63110, USA.
AJNR Am J Neuroradiol. 2003 Jun-Jul;24(6):1057-66.
Wallerian degeneration, the secondary degeneration of axons from cortical and subcortical injury, is associated with poor neurologic outcome. Since diffusion-weighted (DW) imaging is sensitive to early changes of cytotoxic edema, DW imaging may depict the acute injury to descending white matter tracts that precedes Wallerian degeneration; this injury is not visible on conventional CT or MR images in the maturing human brain.
Two neuroradiologists retrospectively analyzed clinical MR images in six children (aged 3 days to 5 months) with DW findings consistent with acute injury of the descending white matter tract due to territorial anterior or middle cerebral artery infarction. In five patients, images were obtained as a part of routine clinical evaluation. The remaining patient was a part of a prospective study of brain injury. Imaging findings were correlated with clinical outcomes.
In all six patients, DW imaging performed 2-8 days after the onset of ischemia depicted injury to the descending white matter tract ipsilateral to the territorial infarct. Conventional MR images of the ipsilateral descending white matter tracts were abnormal in three patients. In all five patients for which follow-up results were available, the presence of DW changes was correlated with persistent neurologic disability.
As shown in this retrospective analysis, DW imaging can depict acute injury to the descending white matter tract in neonates and infants, when conventional MR imaging may show normal findings. These DW findings likely precede the development of Wallerian degeneration, and they may portend a poor clinical outcome.
华勒氏变性是皮质和皮质下损伤后轴突的继发性变性，与不良神经学预后相关。由于扩散加权（DW）成像对细胞毒性水肿的早期变化敏感，DW成像可能描绘出在华勒氏变性之前下行白质束的急性损伤；在成熟的人脑常规CT或MR图像上，这种损伤不可见。
两名神经放射科医生回顾性分析了6例儿童（年龄3天至5个月）的临床MR图像，这些儿童的DW表现与因大脑中动脉供血区梗死导致的下行白质束急性损伤一致。5例患者的图像是作为常规临床评估的一部分获得的。其余1例患者是脑损伤前瞻性研究的一部分。影像学表现与临床预后相关。
所有6例患者在缺血发作后2 - 8天进行的DW成像显示，梗死供血区同侧的下行白质束有损伤。3例患者同侧下行白质束的常规MR图像异常。在有随访结果的所有5例患者中，DW改变的存在与持续性神经功能障碍相关。
如本回顾性分析所示，当常规MR成像可能显示正常结果时，DW成像可描绘新生儿和婴儿下行白质束的急性损伤。这些DW表现可能先于华勒氏变性的发生，并且可能预示不良的临床预后。
