Clinic
A23-year-old man with back pain.
临床
M，23Y，背痛。
Imaging/影像
MRI/T2WI/TRA/SAG
Diagnosis
Dorsal Arachnoid Web.
Figure Caption
Arachnoid web is an intradural extramedullary transverse band of arachnoid tissue that extends to the dorsal surface of the spinal cord, causing mass effect and dorsal indentation (arrow in A).The focal dorsal indentation of the upper thoracic spinal cord is demonstratedon sagittal MRI as the classic “scalpel sign” (arrow in B)because of the resemblance to a scalpel with its blade pointing posteriorly.The arachnoid web may represent incomplete or disrupted formation of arachnoid cyst or may actually represent walls of collapsed arachnoid cyst.
诊断
背侧蛛网膜网格/束带*
讨论
蛛网膜网是一种位于髓外硬膜下横行束带状蛛网膜组织，向背侧脊髓表面延伸导致占位效应及脊髓压痕（图A箭）。上胸段脊髓背侧局部压痕在失状面MRI上表现为典型的“手术刀征”（图B箭），看起来像一个刀锋向后的手术刀。该病可能是由于蛛网膜囊肿发育不全或中断所致，也有可能是蛛网膜囊肿收缩之后形成的残留壁。
补充病例(参考文献AJNR, 2013, 34: 1104-1110)
C． CT myelogram demonstrates the scalpel sign with the characteristic focal dorsal indentation of the upper thoracic spinal cord. An insert of a scalpel shows how the dorsal indentation relates to the pointed edge of the blade.
D．Intraoperative image after opening of the dura demonstrates anintradural white arachnoid band (between arrowheads) passing transversely across and compressing the dorsal surface of the spinal cord.
E. Intraoperative image of the cord after the band of arachnoid tissue has been cut.
C.CT脊髓造影示上胸段脊髓背侧典型的局部脊髓压痕-“手术刀征”。图片中插入的手术刀示背侧压痕类似刀锋缘。
D．打开硬膜后的术中照片示硬膜下的白色蛛网膜束带（箭头间）横向穿过并压迫脊髓背侧表面。
E.蛛网膜束带被切除后的术中脊髓照片。
参考文献
1、M.A. Reardon, et，al.Dorsal Thoracic Arachnoid Web and the“Scalpel Sign”: A Distinct Clinical-Radiologic Entity[J],AJNR, 2013, 34: 1104-1110.(AJNR免费全文)
2、Paramore CG.Dorsal arachnoid web with spinal cord compression: variant of an arachnoid cyst? Report of two cases[2]. J Neurosurg. 2000 Oct;93(2Suppl):287-90.
*说明
由于笔者尚未查阅到国内相关文献，但根据解剖及影像学表现，我们将“web”暂译为“网格”或“束带”，如有不当，欢迎指正~
编译：欧光乾（四川医科大学附属第二医院）
校审：唐光才（四川医科大学附属第一医院）
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