Baumeister L A, Hertzberg B S, McNally P J, Kliewer M A, Bowie J D
Department of Radiology, Duke University Medical Center, Durham, NC 27710.
Radiology. 1994 Aug;192(2):333-6. doi: 10.1148/radiology.192.2.8029392.
To define the normal appearance of the fetal fourth ventricle throughout gestation and ascertain an expected frequency of depiction at different gestational ages.
Three hundred ten consecutive second- and third-trimester fetuses were studied with ultrasound. The posterior fossa was examined to document the size and appearance of the fourth ventricle.
The fourth ventricle was seen in 221 of the 310 fetuses (71.3%) and was most consistently demonstrated in the middle of the second trimester. At this stage of gestation, the fourth ventricle was almost always seen when the anatomic features of the posterior fossa were identified. The mean anteroposterior dimension of the fourth ventricle was 3.5 mm +/- 1.3 (standard deviation), and the mean width was 3.9 mm +/- 1.7.
The fetal fourth ventricle can be seen in most fetuses beginning in the middle of the second trimester and increases in size with advancing gestation. It can be difficult to depict before the middle of the second trimester and late in the third trimester.
明确整个孕期胎儿第四脑室的正常表现，并确定不同孕周时其显示的预期频率。
对310例连续的孕中期和孕晚期胎儿进行超声检查。检查后颅窝以记录第四脑室的大小和表现。
310例胎儿中有221例（71.3%）可见第四脑室，且在孕中期最常显示。在这个孕周阶段，当识别出后颅窝的解剖特征时，几乎总能看到第四脑室。第四脑室的平均前后径为3.5毫米±1.3（标准差），平均宽度为3.9毫米±1.7。
从孕中期开始，大多数胎儿可显示第四脑室，且随着孕周增加其大小会增大。在孕中期之前和孕晚期后期可能难以显示。
