脊髓圆锥末端尾侧椎体骨化中心计数筛查闭合性脊柱裂及脊髓拴系综合征

Counting of fetal caudal vertebral body ossification center below terminal conus medullaris in the screening of the closed spine bifida and tethered cord syndrome

目的探讨产前超声筛查中计数脊髓圆锥末端尾侧椎体骨化中心计数(number of ossification centers,OCN)对闭合性脊柱裂及脊髓拴系综合征的筛查意义。方法选择2013年1月至2020年12月于南方医科大学附属深圳妇幼保健院、广西壮族自治区妇幼保健院和厦门市妇幼保健院17~41孕周正常胎儿961例(正常组)和产后证实的闭合性脊柱裂或脊髓拴系综合征胎儿140例(异常组),在胎儿尾侧脊柱正中矢状切面上计数OCN。随机抽取50例正常胎儿行两观察者间的重复性检验。统计并比较两组胎儿N的差异。绘制ROC曲线并计算截断值。结果正常组中OCN随着孕周稍增加。17~20周时,绝大多数胎儿OCN在5~7之间;20周以上的胎儿中,99.9%的胎儿OCN≥6,97.1%的胎儿OCN≥7。异常组中93.0%的胎儿OCN<7,82.8%的胎儿OCN<6。除17~20周的亚组外,其他胎龄亚组正常组与异常组间OCN的差异有统计学意义(P<0.05)。以6.5为截断值时,OCN预测脊髓拴系综合征及闭合性脊柱裂的敏感性和特异性分别为94.3%和93.0%。结论计数脊髓圆锥末端尾侧椎体骨化中心个数是筛查脊髓圆锥位置的简便方法。绝大部分20周以上的正常胎儿OCN>6,当检查中发现OCN≤6时,应行进一步脊柱评估和检查。

Objective To assess the significance of counting the number of caudal vertebral ossification centers(OCN)below fetal terminal conus medullaris in the screening for closed spina bifida and tethered cord syndrome(TCS).Methods The OCN was counted in 961 normal fetuses(normal group)between 17 and 41 gestational weeks and in 140 fetuses with closed spina bifida or tethered cord syndrome(abnormal group)from Jan.2013 to Dec.2020 in Affiliated Shenzhen Maternity&Child Healthcare Hospital,Southern Medical University,Women and Children′s Hospital,School of Medicine,Xiamen University and Maternity and Child Health Care of Guangxi Zhuang Autonomous Region.The OCN was counted in the dorsal mid-sagittal section of fetal caudal spine.The reliability and agreement test were evaluated by intraclass correlation coefficients in another 50 normal fetuses.The OCN was compared between two groups.ROC curve and the cut-off value were constructed and calculated.Results In normal group,the N increased with the growing of gestational age.In the subgroup of 17-20 weeks,the OCN ranged from 5 to 7 in most fetuses.In the others subgroups,the OCN was equal to or greater than 6 in 99.9%cases and more than 6 in 97.1%cases.In abnormal group,OCN was less than 7 in 93.0%fetuses and less than 6 in 82.8%cases.There were statistical differences between the two groups except for the subgroup of 17-20 gestational weeks(P<0.05).With the cut-off value of 6.5,the specificity and sensitivity were 93.0%and 94.3%respectively for predicting the presence of closed spinal dysraphism or TCS.Conclusions OCN is a simple way to evaluate the position of conus medullaris and to screen for the skin-covered spine dysraphism or TSC.OCN is more than 6 in most normal fetuses.Further evaluation of spine is required in fetuses with N less than or equal to 6.