通过测量胎儿颅脑3个常规筛查横切面上外侧裂平台角度，探讨胎儿大脑皮层发育异常筛查中外侧裂平台角度的截断值。

收集2018年6月至2020年7月到深圳市妇幼保健院进行常规超声检查且孕周范围在23~28⁺⁶周的180例正常单胎孕妇（正常组）和3例异常病例（异常组）。所有病例都在3个常规颅脑筛查横切面（丘脑水平横切面、侧脑室水平横切面和小脑水平横切面）上测量外侧裂平台角度。外侧裂平台角度测量为脑中线与外侧裂平台线相交的夹角。采用非参数检验比较3个切面测值是否有差异。采用组内相关系数（ICC）评价重测一致性或观察者一致性。

在3个切面上正常组所有病例的外侧裂平台角度都>0°，而异常组的3个病例外侧裂角度均<0°。丘脑水平横切面和侧脑室水平横切面上外侧裂平台角度比较（8.28°±3.00° vs 7.98°±2.86°），差异无统计学意义（P>0.05）；但小脑水平横切面上外侧裂平台角度（10.20°±3.46°）大于丘脑水平横切面和侧脑室水平横切面外侧裂平台角度，差异均具有统计学意义（H=-87.458、-103.208，P均<0.05）。重测一致性和观察者间一致性ICC分别为0.971（95%CI：0.945~0.984）、0.936（95%CI：0.819~0.979）。

3个横切面上正常的外侧裂平台角度在23~28⁺⁶周相对稳定，0°可能是评估外侧裂异常的较好截断值，可在丘脑水平横切面测量外侧裂平台角度来评价外侧裂发育情况。

To evaluate the sylvian fissure plateau by sylvian fissure plateau angle (SFPA) and explore the cut-off value of the SFPA in screening for fetal cortical developmental abnormalities.

From June 2018 to July 2020, a prospective ultrasound evaluation was conducted on 180 normal and 3 abnormal singleton pregnant women at 23-28 weeks of gestation in Shenzhen Maternity and Child Healthcare Hospital. All cases were assessed in three axial planes of the fetal brain (transthalamic, transventricular, and transcerebellar) using transabdominal two-dimensional images. The SFPA of all cases was measured between the brain midline (BM) and a line drawn along the sylvian fissure plateau. Non-parametric test was used to compare the differences of the measured SFPA values on the three axial planes. Intraclass correlation coefficient (ICC) was used for assessing the intra- and inter-observer repeatability of the SFPA measurements.

The SFPA in normal cases in the transthalamic, transventricular, and transcerebellar planes were all greater than 0°, while in abnormal cases they were smaller than 0°. However, there was no major difference in the angles measured on the transthalamic and transventricular planes (8.28°±3.00° vs 7.98°±2.86°, P>0.05). There was a major difference in the SFPA on the transcerebellar plane (10.20°±3.46°) and transthalamic/transventricular plane (H=-87.458 and -103.208, respectively, P<0.05). The intra- and inter-observer ICC were excellent at 0.971 (95% confidence interval [CI]: 0.945-0.984) and 0.936 (95%CI: 0.819-0.979), respectively.

The SFPA of normal cases in the three axial views are stable at 23-28⁺⁶weeks of gestation and 0° may be a good cut-off value for evaluating abnormal SFPA. We recommend the SFPA on the transthalamic plane to be used to evaluate the sylvian fissure in clinical work.