研究中孕期胎儿第四脑室形态与大小在鉴别颅后窝异常诊断中的临床应用价值。

根据笔者既往建立并报道的第四脑室正常值测量数据作为第四脑室大小的评价指标，结合胎儿颅脑异常的超声图像、第四脑室形态与大小测值，对2013年1月至2017年12月四川省妇幼保健院产前超声诊断为颅后窝异常58例单胎胎儿的临床资料进行分组研究。第1组，第四脑室增大24例；第2组，第四脑室缩小或消失7例；第3组，第四脑室形态与测值正常27例。总结3组颅后窝异常胎儿临床结局。

第1组24例胎儿中Dandy-Walker畸形15例，超声形态与测值：以第4脑室横径增大为主，横径测值均位于同孕周两倍标准差之上；交通性脑积水9例；超声形态与测值：第四脑室横径、前后径、周长及面积均位于同孕周胎儿两倍标准差之上。第2组7例胎儿中Arnold-ChiariⅡ畸形3例，菱脑融合3例，Joubert综合征1例；超声形态与测值：第四脑室横径、前后径、周长、面积均位于同孕周两倍标准差之下。第3组27例胎儿中后颅窝池增宽10例，颅后窝蛛网膜囊肿3例，第四脑室以上部位梗阻导致脑积水8例，永存Blake陷窝囊肿6例；超声形态与测值：第四脑室横径、前后径、周长及面积均在正常范围内。临床结局：3组58例产前诊断颅后窝异常的胎儿超声或（和）磁共振检查后29例孕妇选择终止妊娠在外院引产，19例孕妇继续妊娠至胎儿正常出生。产后磁共振成像，引产后尸检证实产前超声诊断与产后检查结果均符合。

第四脑室形态与大小测值在产前超声评价颅后窝异常中有重要价值。第四脑室增大、减小甚至消失是颅后窝严重畸形的线索，是预后不良的指标之一。更大样本量，更广孕周范围的研究有可能进一步证实本研究得出的结论。

To assess the value of the shape and size of the fourth ventricle in evaluating fetal posterior fossa abnormalities in the second trimester.

Based on ultrasound images, the size of the fourth ventricle was measured, the shape of the fourth ventricle was described, and the data of the fourth ventricle was compared with the previously established normal range. A study was then performed on the clinical data of 58 singleton cases with fetal posterior fossa abnormalities from January 2013 to December 2017 at the Maternal and Child Health Hospital of Sichuan Province. The cases were divided into three groups: group 1, 24 cases with increased fourth ventricle; group 2, 7 with decreased or vanished fourth ventricle; and group 3, 27 with normal fourth ventricle. The pregnancy outcomes of all cases were summarized.

In group 1, there were 15 cases of Dandy-Walker malformation, the transverse diameter of the fourth ventricle was increased, and the transverse diameters were all double standard deviation (2SD) above the value for the same gestational age; there were 9 cases of communicating hydrocephalus, the transverse and anteroposterior diameters, perimeter, and area were all 2SD above the values for the same gestational age. In group 2, 3 had Arnold-Chiari malformationⅡ, 1 had Joubert syndrome, and 3 had rhombencephalosynapsis; the transverse and anteroposterior diameter, perimeter, and area with decreased or vanished fourth ventricle were all 2SD less than the values for the gestational age. In group 3, 10 cases had increased posterior cranial fossa, 3 had posterior cranium arachnoid cyst, 8 had hydrocephalus caused by obstruction above the fourth ventricle, and 6 had Blake's porch cyst; the transverse and anteroposterior diameter, perimeter, and area were all in the normal ranges. In three groups of 58 patients with prenatal diagnosis of posterior fossa abnormalities, after ultrasound or (and) magnetic resonance examination (MRI), 29 pregnant women chose to terminate the pregnancy, and 19 continued to be pregnant until the normal birth of the fetus. Postpartum MRI and autopsy after induction of labor indicated that prenatal ultrasound diagnosis and postnatal examination results were consistent.

The assessment of the size and shape of the fourth ventricle has important value in prenatal ultrasound evaluation of posterior fossa diseases. It is suggested that increased, decreased, or vanished fourth ventricle are not only important diagnostic evidence but also prognostic indicators for posterior fossa diseases. However, our findings still need to further confirmed by multi-center studies with larger samples and wider ranges of gestational weeks.