Description
A healthy 22-year-old individual with no history of alcoholism, in a coma after a road traffic accident
患者22岁，既往体健，无酗酒史。外伤后昏迷。
横断位T2-FLAIR（A,B）示皮层下白质区及放射冠多发高信号，胼胝体压部轻度水肿，呈弥漫性高信号。
横断位DWI（C）示脑室周围白质及胼胝体弥散受限。
横断位T2-GRE序列（D）未见明显出血成分。
矢状位T2WI(E)示胼胝体压部信号异常。
弥漫性轴索损伤
- Diffuse axonal injury (DAI) or shearing injury is an indirect brain injury that affects primarily the white matter.弥漫性轴索损伤（DAI）或剪切伤，是脑白质损伤为主的间接损伤。
- Sudden angular rotation of the head appears the most likely underlying mechanism.其损伤机制是头部的突然旋转。
DAI患者的典型表现为：外伤后哥斯拉昏迷评分（GCS）降低。
- DAI is characterized by usually (80%) nonhemorrhagic white matter lesions mostly sparing the overlying cortex.约80%的DAI典型表现为皮层下白质区非出血性病变。
- The areas most commonly involved in DAI are the subcortical white matter, corpus callosum (especially splenium), corona radiata, internal capsule, and the dorsolateral aspect of the upper brainstem.DAI最常累及的部位：皮层下白质区、胼胝体（尤其是压部）、放射冠、内囊、脑干背外侧。
- FLAIR and DWI are the most useful imaging sequences for nonhemorrhagic DAI, whereas T2*-weighted sequences and SWI are more sensitive for hemorrhagic DAI.FLAIR和DWI序列有助于非出血性DAI的诊断；T2*WI和SWI对小出血灶的检出更敏感。
该病需要与外伤后的脑脂肪栓塞相鉴别：
- Usually there is an associated long bone fracture and a 24–72 hour latency period (rather than immediate) before decreased GCS.一般来说，脑脂肪栓塞多伴有四肢长骨的骨折，在GCS降低前可以有24-72小时的潜伏期。
- Typically associatied with respiratory distress and skin petechiae.典型病例可伴有呼吸困难、皮肤瘀斑。
- DWI will show diffuse punctuate hyperintense foci called a “star field pattern”.DWI示多发散在高信号灶，呈“星空征”。
支持治疗、神经保护。如果病变累及脑干，一般预后很差。