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。

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.