Fetal Medicine Unit, Di Venere and Sarcone Hospitals, ASL BA, Bari, Italy.
Department of Clinical Science and Community Health, University of Milan, Milan, Italy.
Am J Obstet Gynecol MFM. 2019 May;1(2):173-181. doi: 10.1016/j.ajogmf.2019.06.004. Epub 2019 Jun 13.
The role of the first-trimester scan has expanded from aneuploidy screening to the diagnosis of fetal malformations. Abnormal appearance of the posterior brain at 11-14 weeks gestation is a marker of cerebral anomalies; in fact an increased amount of fluid, particularly when the choroid plexus of the fourth ventricle is not visible and only 2 brain spaces instead of 3 are seen, may indicate the presence of cystic or cyst-like posterior fossa anomalies, such as Blake's pouch cyst or Dandy-Walker malformation.
The purpose of this study was to assess the role of ultrasound scanning in the identification of cystic posterior fossa anomalies at 11-14 weeks gestation.
A prospective cohort study of fetuses with cystic appearance of the posterior fossa at 11-14 weeks gestation was performed. In all cases and in a control group of 40 normal fetuses, the brainstem-tentorium angle was also measured. The presence or absence of cystic posterior anomalies was determined at birth or at postmortem evaluation.
In the period 2014-2018, 32 fetuses with an increased brainstem-occipital bone distance and/or failure to visualize the choroid plexus of fourth ventricle (2 brain spaces) were seen. Of these, 18 fetuses were terminated in the first trimester because of associated anomalies and were excluded from the study because of unavailable autoptic findings. The remaining 14 fetuses eventually were found to have a Dandy-Walker malformation in 4 cases, a Blake's pouch cyst in 8 cases, and normal brain anatomy in 2 cases. Two brain spaces were seen in all cases with Dandy-Walker malformation and in 2 of 8 cases with Blake's pouch cyst. Both brainstem-occipital bone measurement and brainstem-tentorium angle were significantly different in fetuses with Dandy-Walker malformation, Blake's pouch cyst, and control subjects (P<.0001). The brainstem-occipital bone z-scores of fetuses with Dandy-Walker malformation and Blake's pouch cyst were always +3 or more and +1.7 or more, respectively. The brainstem-tentorium angle z-scores were always -5 or less and -0.1 or less, respectively.
Our study confirms that sonography of the posterior brain at 11-14 weeks gestation allows the identification of cystic posterior fossa anomalies. A large brainstem-occipital bone predicts Dandy-Walker malformation or Blake's pouch cyst. The presence of 2 brain spaces and a small brainstem-tentorium angle are correlated significantly with the presence of Dandy-Walker malformation.
早孕期超声检查的作用已从筛查非整倍体扩展到胎儿畸形的诊断。11-14 孕周时后颅窝异常外观是脑畸形的标志物；事实上，当第四脑室脉络丛不可见且仅可见 2 个脑间隙而不是 3 个脑间隙时，可能表明存在囊性或囊样后颅窝异常，如 Blake 袋囊肿或 Dandy-Walker 畸形。
本研究旨在评估 11-14 孕周超声检查在识别囊性后颅窝畸形中的作用。
对 11-14 孕周时后颅窝囊性表现的胎儿进行前瞻性队列研究。在所有病例和 40 例正常胎儿的对照组中，还测量了脑干-天幕角。在出生或尸检时确定是否存在囊性后颅窝异常。
在 2014 年至 2018 年期间，发现 32 例后颅窝脑干-枕骨距离增加和/或第四脑室脉络丛不可见（2 个脑间隙）的胎儿。其中，18 例因伴发畸形而在早孕期终止妊娠，由于无法获得尸检结果，这些病例被排除在研究之外。其余 14 例胎儿最终发现 4 例为 Dandy-Walker 畸形，8 例为 Blake 袋囊肿，2 例为正常脑解剖。所有 Dandy-Walker 畸形和 8 例 Blake 袋囊肿中均可见 2 个脑间隙。Dandy-Walker 畸形、Blake 袋囊肿和对照组胎儿的脑干-枕骨测量值和脑干-天幕角均有显著差异（P<.0001）。Dandy-Walker 畸形和 Blake 袋囊肿胎儿的脑干-枕骨 z 评分均为+3 或更高和+1.7 或更高。脑干-天幕角 z 评分均为-5 或更低和-0.1 或更低。
本研究证实，11-14 孕周时的后颅窝超声检查可识别囊性后颅窝畸形。大的脑干-枕骨提示 Dandy-Walker 畸形或 Blake 袋囊肿。存在 2 个脑间隙和小的脑干-天幕角与 Dandy-Walker 畸形的存在显著相关。
