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妇产科超声影像学

早孕期胎儿头面部超声标志物对开放性脊柱裂的预测价值

  • 朱燕彤 1 ,
  • 吴青青 , 1, ,
  • 冯丽 1 ,
  • 熊晓蔚 1 ,
  • 王晶晶 1
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  • 1.100026 北京,首都医科大学附属北京妇产医院 北京妇幼保健院超声科
吴青青,Email:
Wu Qingqing, Email: qingqingwu @ccmu.edu.cn

Copy editor: 吴春凤

收稿日期: 2024-03-14

  网络出版日期: 2025-01-24

基金资助

国家重点研发计划(2022YFC2703301)

版权

版权归中华医学会所有。 未经授权,不得转载、摘编本刊文章,不得使用本刊的版式设计。 除非特别声明,本刊刊出的所有文章不代表中华医学会和本刊编委会的观点。

Predictive value of fetal craniofacial ultrasound markers for open spina bifida in first trimester

  • Yantong Zhu 1 ,
  • Qingqing Wu , 1, ,
  • Li Feng 1 ,
  • Xiaowei Xiong 1 ,
  • Jingjing Wang 1
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  • 1.Department of Ultrasound, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, Beijing 100026, China

Received date: 2024-03-14

  Online published: 2025-01-24

Copyright

Copyright by Chinese Medical Association No content published by the journals of Chinese Medical Association may be reproduced or abridged without authorization. Please do not use or copy the layout and design of the journals without permission. All articles published represent the opinions of the authors, and do not reflect the official policy of the Chinese Medical Association or the Editorial Board, unless this is clearly specified.

摘要

目的

分析早孕期(妊娠11~13+6周)胎儿头面部特征,评估胎儿头面部超声标志对开放性脊柱裂(OSB)的预测价值。

方法

回顾并分析2018年12月至2023年11月在首都医科大学附属北京妇产医院确诊的13例OSB胎儿和60例正常胎儿的医学资料,根据产前超声质量控制标准选取早孕期超声标准切面,在头面部正中矢状切面上评估间脑、中脑、脑干、第四脑室及后颅窝池形态,测量脑干宽度(BSW)及脑干后缘至枕骨距离(BSOB),计算二者的比值,评估额上颌角(FMFA)大小,同时观察定性指标上颌-枕骨线(MO线)与丘脑中脑联合处(J-TM)的关系;在侧脑室横切面上测量计算脉络丛长度与额枕径比值(CP-L/OFD)、脉络丛面积与侧脑室平面脑面积比值(CP-A/HA)。采用t检验或秩和检验比较上述指标的组间差异,使用Lasso回归对指标进行筛选分析,使用逻辑回归建立预测模型,分别绘制各指标及预测模型的受试者操作特征(ROC)曲线,评价各指标对OSB胎儿的预测价值。

结果

在头面部正中矢状面上,60例正常胎儿间脑、中脑呈“8字形”形态,脑干、第四脑室及后颅窝池结构可清晰显示,呈近平行三腔隙,J-TM均位于MO线的上方;13例OSB胎儿间脑及中脑形态扭曲、脑干下移增宽、BSOB变窄,第四脑室受压变小,其中10例(76.9%)第四脑室消失,三腔隙变为两腔隙,11例(84.6%)胎儿的J-TM在MO线下方。相比正常组,OSB组胎儿BSW/BSOB明显增大[1.26(0.79,1.49) vs 0.57(0.52,0.65)],FMFA角度明显缩小[77.60(67.05,84.22)° vs 85.09(80.15,89.03)°],差异具有统计学意义(Z=18.09,P<0.001;Z=6.48,P=0.009)。Lasso回归分析结果显示BSW/BSOB、FMFA及CP-A/HA 3个指标是预测OSB的重要变量,基于此建立回归模型,回归方程为log(P/1-P)=2.043BSW/BSOB-0.026FMFA+1.251CP-A/HA-12.414,ROC曲线分析显示,预测模型曲线下面积为0.928,较其他因素有更高的诊断效能。

结论

妊娠11~13+6周超声筛查常规切面获取的超声指标可有效预测胎儿OSB,其中BSW/BSOB、FMFA及CP-A/HA是预测OSB的重要变量,三者联合对OSB诊断效能更高。

本文引用格式

朱燕彤 , 吴青青 , 冯丽 , 熊晓蔚 , 王晶晶 . 早孕期胎儿头面部超声标志物对开放性脊柱裂的预测价值[J]. 中华医学超声杂志(电子版), 2024 , 21(11) : 1005 -1010 . DOI: 10.3877/cma.j.issn.1672-6448.2024.11.001

Abstract

Objective

To evaluate the predictive value of fetal craniofacial ultrasound markers for open spina bifida (OSB) during early pregnancy (gestational weeks 11-13+6).

Methods

The medical data of 13 fetuses with OSB and 60 normal fetuses that underwent prenatal examinations at Beijing Obstetrics and Gynecology Hospital, Capital Medical University from December 2018 to November 2023 were retrospectively reviewed and analyzed. Based on prenatal ultrasound quality control standards, standard sections of early pregnancy ultrasound were selected. The mid-sagittal section of the craniofacial region was assessed for morphology of the interbrain,midbrain, brainstem, fourth ventricle, and posterior fossa cistern. Measurements included brain stem width(BSW) and the distance from the brainstem posterior edge to the occipital bone (BSOB). The BS/BSOB ratio was calculated, and the frontomaxillary facial angle (FMFA) was evaluated. Qualitative indicators such as the maxilla-occipital line (MO line) in relation to the junction of the thalamus and midbrain (J-TM) were observed.Measurements on the lateral ventricle transverse section included the ratio of choroid plexus length to occipitofrontal diameter (CP-L/OFD), choroid plexus area, and the ratio of choroid plexus area to lateral ventricle plane brain area(CP-A/HA). The t-test or rank sum test was used to compare the differences in the above indexes. Lasso regression was used to screen the indexes to establish a prediction model. Receiver operating characteristic (ROC) curves of each index and the prediction model were drawn to evaluate the predictive value of each index for OSB in fetuses.

Results

In the mid-sagittal plane of the head and face, the diencephalon and mesencephalon of 60 normal fetuses exhibited an “8-shaped” morphology. The brainstem, fourth ventricle, and posterior fossa structures were clearly visible, appearing as three nearly parallel cavities. The J-TM was located above the MO line. In 13 OSB fetuses,the diencephalon and mesencephalon were distorted, the brain stem was displaced downward and widened, the BSOB was narrowed, and the fourth ventricle was compressed and reduced in size. Among these fetuses, the fourth ventricle disappeared in 10 cases (76.9%), leading to the presence of two cavities. In 11 cases (84.6%), the J-TM was below the MO line. Compared to the normal group, the OSB group showed a statistically significant increase in BSW/BSOB [1.26 (0.79, 1.49) vs 0.57 (0.52, 0.65); Z=18.09, P<0.001] and a statistically significant decrease in the FMFA [77.60° (67.05°, 84.22°) vs 85.09° (80.15°, 89.03°); Z=6.48, P=0.009]. Lasso regression analysis showed that BSW/BSOB, FMFA, and CP-A/HA were significant variables for predicting OSB. Based on these variables, a regression model was established, and the regression equation was log(P/1-P) =2.043BSW/BSOB-0.026FMFA+1.251CP-A/HA-12.414. The ROC curves of each index and the regression model were plotted, and the area under the curve of the predictive model was 0.928, indicating good diagnostic performance compared to other indexes.

Conclusion

Ultrasound markers obtained from routine sections in fetuses at 11-13+6 gestational weeks can effectively predict fetal OSB. BSW/BSOB, FMFA, and CP-A/HA are significant variables for predicting OSB, and their combination provides better diagnostic value for OSB.

脊柱裂是一种由胎儿神经管发育异常引起的先天性神经系统畸形,可分为开放性脊柱裂(open spina bif ida,OSB)和闭合性脊柱裂。OSB胎儿由于脑脊液持续渗漏至羊膜腔内,导致蛛网膜下腔压力降低,从而使脑组织向尾端移位,引发阻塞性脑积水。对于OSB,通常在孕中期可以通过识别间接征象[1](如香蕉征和柠檬征)或直接可视化脊柱病变进行诊断。近年来,随着高分辨率超声仪器的发展和技术的进步,超声检查能够准确观察妊娠早期胎儿微小解剖结构[2]。研究表明[3-8],在妊娠11~13+6周时,可以观察到OSB早期间接头面部征象的改变,通过常规筛查切面获取的超声指标可以有效地筛查OSB。本研究旨在评价妊娠11~13+6周所获得头面部超声特征对OSB的临床诊断价值。

资料与方法

一、对象

OSB组:回顾性分析2018年12月至2023年11月在首都医科大学附属北京妇产医院诊断为OSB胎儿13例。孕妇年龄为(32.4±4.7)岁(范围27~43岁)。纳入标准:(1)在妊娠11~13+6周接受胎儿颈项透明层超声检查;(2)胎儿正中矢状切面及侧脑室横切面超声图像符合产前超声筛查指南规定的标准切面;(3)经引产后尸检或随访证实为OSB。
正常组:选取同期与OSB组年龄、孕龄相匹配的60例正常胎儿作为正常组。要求:(1)胎儿早孕期超声图像符合标准切面质量控制标准;(2)胎儿超声孕龄与月经估算孕龄相符;(3)产前超声检查及出生后随访42 d证实胎儿无异常。

二、仪器与方法

1. 仪器及人员配置:采用GEVoluson E8、E10/Samsung WS80A/Philips EPIQ7彩色多普勒超声诊断仪,探头频率为2.0~9.0 MHz。超声检查由接受过系统产前超声诊断技术培训、具有3年以上妇产科超声工作经验的医师完成。
2. 方法:回顾并分析60例正常胎儿及13例OSB胎儿11~13+6周超声检查图像、孕期常规超声检查报告以及妊娠结局等资料。根据英国胎儿医学基金会规范,所有研究对象选取早孕期超声标准头面部正中矢状切面和侧脑室横切面进行评估分析。在头面部正中矢状切面上评估间脑、中脑、脑干、第四脑室及后颅窝池形态,采取平行测量方法,将游标置于内侧缘测量脑干宽度(brain stem width,BSW)及脑干后缘至枕骨距离(brainstem-occipital bone distance,BSOB),并计算BSW/BSOB值,评估额上颌角(frontal maxillary facial angle,FMFA)大小,同时观察上颌-枕骨(maxilla-occipital,MO)线与丘脑-中脑联合处(the junction of the thalamus with the midbrain,J-TM)的位置关系,在侧脑室横切面上测量计算脉络丛长度与额枕径比值(choroid plexus length to occipitofrontal diameter ratio,CP-L/OFD)、脉络丛面积与侧脑室平面脑面积比值(choroid plexus area to lateral ventricle plane brain area ratio,CP-A/HA)。上述参数使用Imagine J软件进行测量,均重复测量3次,取均值为最后结果。

三、统计学分析

采用SPSS 25.0及R v3.6.0统计软件进行统计分析。符合正态分布的计量资料以表示,组间行两独立样本t检验;不符合正态分布的计量资料以MQR)表示,组间采用秩和检验;计数资料以例(%)表示,组间行χ2检验。应用Lasso回归分析各超声指标,筛选与目标变量OSB最相关的参数,使用逻辑回归建立预测模型,绘制各相关参数及回归模型的受试者操作特征(receiver operating characteristic,ROC)曲线,计算曲线下面积(area under the curve,AUC),以评价各参数及回归模型对OSB胎儿的预测价值。P<0.05为差异有统计学意义。

结 果

一、OSB组与正常组一般资料比较

2组孕妇年龄、早孕期超声检查孕龄及颈项透明层厚度比较,差异均无统计学意义(P均>0.05,表1)。
表1 2组研究对象一般资料比较(±s
组别 例数 年龄(岁) 孕龄(周) 颈项透明层厚度(mm)
OSB组 13 32.46±4.72 13.04±0.51 1.70±0.54
对照组 60 31.73±3.70 12.85±0.42 1.64±0.39
t 0.612 1.468 0.471
P 0.543 0.147 0.639

二、OSB组与正常组头面部超声指标比较

在头面部正中矢状切面,60例正常胎儿间脑、中脑呈“8字形”形态,脑干、第四脑室及后颅窝池结构可清晰显示,呈近平行三腔隙,J-TM均位于MO线的上方。13例OSB胎儿间脑及中脑形态扭曲、脑干下移增宽、BSOB变窄,第四脑室受压变小,其中10例(76.9%)第四脑室消失,三腔隙变为两腔隙,11例(84.6%)胎儿的J-TM在MO线下方。相比正常组,OSB组胎儿BSW/BSOB明显增大,FMFA角度明显缩小,差异均具有统计学意义(P均<0.05,图1表2)。
图1 正常及开放性脊柱裂(OSB)胎儿头面部正中矢状切面声像图。图a为正常胎儿,黄色箭头为丘脑中脑联合处(J-TM),可见其位于上颌骨-枕骨(MO)线之上;图b示OSB胎儿第四脑室受压消失,只显示两腔隙,J-TM位于MO线之下

注:TH为间脑,M为中脑,BS为脑干,IT为颅内透明层,CM为后颅窝池,测量1为BS宽度,测量2为脑干后缘至枕骨距离

表2 OSB组与正常组胎儿头面部超声指标比较
超声指标 OSB组(n=13) 正常组(n=60) 统计值 P
BSW(mm,x¯±s 2.71±0.61 2.34±0.31 t=2.32 0.037
BSOB(mm,x¯±s 2.54±1.02 3.91±0.62 t=-4.71 <0.001
BSW/BSOB[MQR)] 1.26(0.79,1.49) 0.57(0.52,0.65) Z=18.09 <0.001
FMFA[°,MQR)] 77.60(67.05,84.22) 85.09(80.15,89.03) Z=6.48 0.009
CP-L/OFD[MQR)] 0.66(0.55,0.69) 0.54(0.50,0.57) Z=11.09 0.003
CP-A/HA(x¯±s 3.34±0.73 2.68±0.41 t=3.14 0.008
J-TM在MO线下方[例(%)] 11(84.6) 0(0) χ 2=94.64 <0.001
在侧脑室横切面,大多数OSB胎儿的脉络丛充满侧脑室,呈“干脑征”,相比正常组,OSB组CP-L/OFD、CP-A/HA明显增大,差异均具有统计学意义(P均<0.05,图2表2)。
图2 正常及开放性脊柱裂(OSB)胎儿侧脑室横切面超声声像图。图a:正常组胎儿,脉络丛大小形态正常,周围有脑脊液;图b:OSB组胎儿,脉络丛占据侧脑室的比重增加,呈现“干脑征”。测量并比较2组脉络丛长径(CP-L)和额枕径(OFD)、脉络丛面积(CP-A)和侧脑室平面脑面积

三、OSB预测模型的构建与验证

以OSB为目标变量,BSW/BSOB、FMFA、CP-L/OFD、CP-A/HA、MO线与J-TM位置关系为因变量,对其行Lasso回归,入选最优模型共3个参数:BSW/BSOB、FMFA和CP-A/HA,作为预测OSB的重要变量(图3)。使用逻辑回归构建OSB的预测模型:log(P/1-P)=2.043BSW/BSOB-0.026FMFA+1.251CP-A/HA-12.414,分别绘制3个相关参数及预测模型的ROC曲线(图4),结果显示预测模型的AUC为0.928,相较于其他因素有较好的预测效能(表3)。
图3 Lasso回归分析图。图a是Lasso系数路径图,显示了在Lasso算法中,不同的参数(λ)取值对应的特征系数变化情况。图b是Lasso正则化路径图,显示不同的正则化参数(λ)取值对应的模型拟合效果
图4 开放性脊柱裂胎儿风险预测模型及各相关因素的受试者操作特征曲线

注:BSW/BSOB为脑干宽度与脑干后缘至枕骨距离的比值,FMFA为额上颌角,CP-A/HA为脉络丛面积与侧脑室平面脑面积的比值

表3 各相关参数及预测模型对开放性脊柱裂的预测价值
指标 AUC 95%CI 敏感度(%) 特异度(%) 最佳截断值
BSW/BSOB 0.880 0.758~1 76.9 98.3 0.88
CP-A/HA 0.803 0.635~0.970 69.2 90.1 3.14
FMFA(°) 0.737 0.569~0.904 53.8 91.7 77.70
预测模型 0.928 0.827~1 92.3 85.3 0.92

讨 论

对于OSB的超声筛查,通常在孕中期直接可视化脊柱病变或通过识别间接征象(如香蕉征和柠檬征)进行诊断,在大多数情况下,在妊娠早期直接观察脊柱缺陷比较困难,但由于脑脊液渗漏和颅内负压,脑组织向尾侧移位而引起头面部结构变化,通过常规超声筛查切面观察间接头面部征象的改变也可以有效地筛查OSB[9],达到早发现、早诊断、早干预的目的。
本组13例OSB胎儿中,有3例在早孕期检查时因脊柱异常怀疑OSB,孕妇选择继续妊娠,中孕期超声检查发现典型颅脑改变、脊柱排列不规则、受累脊柱后方的强回声线及其表面皮肤光带和软组织连续性中断而明确诊断;10例胎儿早孕期仅见颅内结构异常而未见明显脊柱异常,后于中孕期确诊。本研究结果显示早孕期的5种头面部超声标志在OSB组和正常组间差异有统计学意义。OSB组胎儿BSW增宽、BSOB减小、BSW/BSOB增大,与以往的研究报道一致[10-13]。此改变的原因是OSB胎儿脑脊液渗漏到羊膜腔中,脑干和小脑向椎管内移位,后脑向下移位,脑干增宽,第四脑室受压变小甚至消失。该病理改变除了导致颅后窝结构异常,同时由于脑结构的尾侧位移,也导致额骨的发育受到破坏,额骨后缩,使FMFA减小。本组OSB胎儿的FMFA明显小于正常胎儿,与既往报道一致[14-15]。OSB胎儿由于脑脊液渗漏,脉络丛占据侧脑室的比重增加,呈现“干脑征”,其可以量化为CP-L/OFD、CP-A/HA[16],本研究结果显示OSB组中这两个指标明显增大。除上述定量指标外,定性指标更为直观[17],本研究13例OSB胎儿中有10例(76.9%)第四脑室受压消失,由脑干、第四脑室及后颅窝池结构形成的近平行三腔隙变为两腔隙。正常组胎儿的J-TM均位于MO线的上方,OSB组中有11例(84.6%)胎儿的J-TM在MO线下方,可以看出定性指标特异度较高,适合日常筛查OSB,与既往研究结论一致[18]
本研究回顾性分析OSB胎儿早孕期头面部超声特征,基于早孕期超声筛查的头面部正中矢状切面和侧脑室切面选择了5个超声标志,以便于评估测量且无需额外增加切面。按照产前超声筛查指南[19]对研究对象进行质量控制,符合标准切面规范的图像才被纳入测量分析。这是因为早孕期颅面部结构精细,易受测量切面的影响而变化,所以对研究对象图像进行质量控制筛选对于后续指标测量具有重要意义。既往多数研究主要探讨各超声标志在病例组和正常组之间的差异,并未比较各指标的诊断效能。这与OSB发病率低,样本量较少有关。本研究采用Lasso回归进行变量筛选原因在于,Lasso回归是一种特征选择方法,它倾向于将目标变量影响较小的变量的系数收缩至零,从而识别出对目标变量具有较大影响的重要变量,增加模型的解释性和预测准确度[20]。结果显示,BSW/BSOB、FMFA和CP-A/HA 3个变量被选入了最优模型中,表明它们对OSB的预测更具重要性。构建预测模型,绘制ROC曲线,结果显示这三个超声标志在OSB筛查中表现出较高的敏感度和特异度,而联合指标构建的预测模型对OSB的诊断效能更高,因此,它们能够有效地用于早孕期超声筛查胎儿OSB。
综上所述,BSW/BSOB、FMFA和CP-A/HA对早期诊断OSB更有价值;进一步将该3个指标联合建立的预测模型,对于OSB具有更高的诊断效能。作为一项单中心回顾性病例对照研究,本研究样本量有限,因此研究结论具有一定的局限性。后续尚需扩大样本量,获取更详尽完善的数据进一步验证本结论,以提高OSB的早期检出率。
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