【双语病例】Sacral Agenesis 骶骨发育不全来源：双语学影像；本期病例选自AJNR Case of the Week 
Vineet Aggarwal, Bargavee Venkat, Neeti Aggarwal
Indira Gandhi Medical college, Shimla, India 
DescriptionA 12-year-old girl with limb length discrepancy and backache 12岁女孩，双下肢不等长，腰背部疼痛。
LegendsCoronal T2WI (A) demonstrates dural ectasia and thoracolumbar scoliosis. Sagittal T1WI (B) demonstrates a tethered cord due to an intraspinal fatty lesion, with an associated dimple on the overlying skin and dorsal dermal sinus, suggestive of an intraspinal dermoid cyst. Also noted is sacral agenesis confirmed on the volume rendered 3D CT images (C). 冠状位T2WI示硬膜下间隙扩大、脊柱侧弯。 矢状位T1WI示椎管内含脂质的病灶通过窦道与背部皮下相连，局部皮肤略凹陷，病灶性质考虑为皮样囊肿。脊髓圆锥低位，脊髓栓系。 CT三维重建VR图像示骶骨发育不全。
Sacral Agenesis
骶骨发育不全
Sacral agenesis considered a part of caudal regression syndrome. It is a rare sacral developmental abnormality consisting of absence of part or all of the sacrum. 骶骨发育不全是尾部退化综合征的一种，指骶骨部分或完全缺如，是一种罕见的骶骨发育异常。 It is clinically associated with malformation of the hindgut, caudal spinal cord, lower limbs, and the urogenital system. 临床上与后肠、尾部脊髓、下肢、泌尿生殖系统的畸形有关。 Sacral agenesis has an incidence of 1 in 25,000 live births and is associated with maternal diabetes in approximately 25% cases. 骶骨发育不全在全部新生儿中发病率约为1/25000，其中约25%与产妇糖尿病有关。 Renshaw classified sacral agenesis into four types, based on the amount of sacrum remaining and articulation between pelvis and spine. Renshaw按骶骨残余的多少及脊柱、骨盆连接情况将骶骨发育不全分为四型。
Key Diagnostic FeatureDevelopmental malformations of the caudal spinal cord include sacral meningomyelocele, tethered cord, transistional lipoma, and cauda equina syndrome due to stenosis of the dural sac. 尾部脊髓发育异常包括骶脊髓脊膜膨出、脊髓栓系、过渡型脂肪瘤、以及由于硬膜囊狭窄引起的马尾综合征。 As seen on MRI, the position of the conus defines 2 distinct groups of patients with sacral agenesis: 根据MRI上脊髓圆锥的位置，将骶骨发育不全分为2组： In group 1 the conus is absent and the spinal cord ends with a blunted appearance, cranial to the lower border of the L1 vertebra. In this group the sacrum is completely absent. 第一组中，脊髓圆锥缺如，L1水平脊髓末端呈圆钝形。此型中，骶骨为完全缺如。 In group 2 there is a tethered cord and the conus is present below L1. In these patients variable parts of the sacrum are present. 第二组中，脊髓栓系，圆锥位于L1水平以下。此型患者骶骨不同程度部分缺如。
Multiple vertebral anomalies such as fused vertebra, hemivertebra, butterfly vertebra, and diastematomyelia may also be seen. 可合并其他多种脊柱畸形，如椎体融合、半椎体、蝶形椎、脊髓纵裂等。
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