本期病例选自AJNR Case of the Week，转自：双语学影像。
Description:
A 34-year-old man with a new-onset seizure.
34岁男性，新发癫痫。
下图依次为A、B、C、D。
Legends:
Bone-eliminated brain CT angiography (A, B) revealed a huge left middle cerebral artery (MCA)aneurysm with a tortuous channel (arrows).3D reconstruction (C) showed bothsides of the aneurysm connected to the MCA branches (arrows). Conventional angiography (D) confirmed an irregular, dilated, serpiginous,partially thrombosed arterial vascular channel originating from the left M2 segment (arrow)
去骨的脑部CTA（A,B）示左侧大脑中动脉巨大动脉瘤，走形迂曲。三维重建图像（C）显示：动脉瘤的两端与大脑中动脉相连（箭头）。血管造影（D）证实 ：左侧大脑中动脉M2段血管迂曲扩张，形态不规则，部分瘤壁可见血栓形成。
（小编：A图和B图，是CTA还是MRA？傻傻分不清楚。可原文中说的就是CTA）
Giant Serpentine Aneurysm
巨大蛇形动脉瘤
Giant serpentine aneursyms are uncommon (< 0.1%),="" fusiform,="" partially="" thrombosed="" aneurysms="" with="" a="" separate="" outflow="" tract="" to="" normal="" distal="" cerebral="" vessels="" and,="" possibly,="" they="" result="" from="" repeated="" dissection="" of="" an="" intrinsic="" abnormal="" vessel="" wall="" with="" intramural="">
巨大蛇形动脉瘤临床少见（＜0.1%），常呈纺锤形，部分瘤壁可见血栓形成，动脉瘤可通过单独流出道与远端正常血管相连。其病因可能与血管壁本身病变所致的反复壁间血肿有关。
Fifty percent occur in the MCA, 18% in the PCA, 15% in the vertebral artery or vertebrobasilar junction, 13% in the ICA, and 3% in the ACA.
约50%的巨大蛇形动脉瘤发生于大脑中动脉，18%发生于大脑后动脉，15%发生于椎动脉或椎-基底动脉交界处，13%发生于颈内动脉，3%发生于大脑前动脉。
Clinical Presentation:
Mostly related to mass effect and, less frequently, to distal ischemia by distal emboli or flow impairment. Common symptoms include headache, nausea/vomiting, hemiparesis, dysphasia/aphasia, and seizure.
临床症状主要是病变的占位效应，部分病例因为病变远端血栓形成或血流异常引起缺血症状。常见症状包括：头疼、恶性/呕吐、轻偏瘫、吞咽困难/失语、癫痫等。
Key Diagnostic Features:
CT: Well-circumscribed extra-axial heterogeneous mass lesion with surrounding edema, occasionally with thin peripheral rim calcifications. Intense homogeneous enhancement of the serpiginous vascular lumen and peripheral rim enhancement of the aneurysm wall.
CT：轴外不均质肿块，边界清楚，周边可见水肿，偶尔可见薄壁周边钙化。增强扫描，蛇形管腔内明显不均匀强化，血管壁外缘强化。
MRI: Heterogeneous hyperintense signal on T1W, heterogeneous signal on T2W,perilesional a central or excentric irregular flow void on spin-echo sequences representing the patent arterial lumen. No consistent pattern for contrast-enhancement.
MRI:T1WI呈不均匀高信号，T2WI信号不均匀，SE序列可见偏心性流空信号，提示管腔内部分通畅。增强扫描强化方式不一。
Angiography: A partially thrombosed sac greater than 25 mm in diameter, with a tortuous centra or excentrical vascular channel following a wavy and sinusoidal course.There, long segmental involvement with a separate inflow and outflow zonesdifferentiates them from saccular aneurysms.
血管造影：瘤体直径大于25mm，部分瘤壁可见血栓，病灶内可见迂曲的血管通道。病灶累及范围较大以及有独立的流入道和流出道，这是该病与囊性动脉瘤的主要鉴别点。
DDx:
Cerebral arteriovenous fistula. Normal arteries on both sides are the diagnostic clue, in contrast to AVFs, where the dilated vascular pouch has a venous origin.
主要与脑动静脉瘘相鉴别。病灶两侧正常的动脉血管是主要的诊断线索，而动静脉瘘的囊状扩张的血管多为静脉血管。
Rx:
Surgical bypass with obliteration and endovascular occlusion are the main treatment options.
主要治疗方法包括外科搭桥血管闭塞术、血管内闭塞术。
Reconstructive techniques with flow diverter stents have been used, but with higher rates of in-stent thrombosis.
血流导向支架血管重建技术已逐渐在临床使用，但支架内血栓形成的风险较大。
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