探讨胎儿小脑延髓池（枕大池）增宽病例的产前超声诊断价值。

回顾性收集2017年10月至2019年10月北京协和医院因产前筛查发现小脑延髓池增宽（＞10 mm）的进行系统超声检查的胎儿73例，所有病例均在超声检查后行胎儿颅脑MRI检查，并对检查结果进行对比，计算超声诊断符合率。

73例胎儿小脑延髓池增宽胎儿经胎儿颅脑MRI检查最终提示Dandy-Walker畸形4例，小脑蚓部发育不良2例，小脑发育不良4例，颅后窝蛛网膜囊肿8例，Blake's囊肿1例，单纯小脑延髓池增宽54例。与胎儿颅脑MRI检查结果比较，产前超声诊断颅后窝异常的符合率为84.9%（64/73）。本组中MRI诊断合并其他颅内异常者17例（23.3%，17/73），其中超声诊断13例（76.5%，13/17）。

与MRI相比，超声对胎儿小脑延髓池增宽相关疾病的诊断准确率较高。对于Dandy-Walker畸形、小脑发育不良等相对较严重的疾病，超声声像图特点典型，不易漏误诊，对于小脑蚓部发育不良、Blake's囊肿、颅后窝蛛网膜囊肿等疾病需仔细鉴别。

To evaluate the diagnostic value of prenatal ultrasound in fetuses with cerebellomedullary cistern (cisterna magna) dilatation.

Seventy-three fetuses with cisterna magna dilatation (＞10 mm) detected in prenatal ultrasound screening from October 2017 to October 2019 at Peking Union Medical College Hospital, Chinese Academy of Medical Sciences were included. All cases underwent fetal cranial MRI after ultrasound examination, and the examination results were compared to calculate the concordance rate between ultrasound and MRI.

Of the 73 fetuses diagnosed with cisterna magna dilatation by ultrasound, MRI suggested Dandy-Walker malformation in four cases, cerebellar vermis hypoplasia in two, cerebellar hypoplasia in four, posterior fossa arachnoid cyst in eight, Blake's pouch cyst in one, and cisterna magna dilation in 54. Compared with MRI, the diagnostic accuracy of prenatal ultrasound for posterior fossa abnormality was 84.9% (64/73). In this group of patients, 17 patients (23.3%, 17/73) were found to be complicated with other intracranial abnormalities by MRI, including 13 cases (76.5%, 13/17) detected by ultrasound.

Ultrasound has a high diagnostic accuracy for related disorders with fetal cisterna magna dilatation compared with MRI. Major malformations such as Dandy-Walker malformation and cerebellum dysplasia have typical sonographic features and are not easily misdiagnosed, and causion should be taken for disorders such as cerebellar vermis hypoplasia, Blake's pouch cyst, and posterior fossa arachnoid cyst.