Vermian Biometric Parameters in the Normal and Abnormal Fetal Posterior Fossa

Abstract

Objectives The purposes of this study were to describe a 3‐dimensional sonographic technique for evaluation of the fetal vermis and to compare vermian biometric parameters in fetuses with a normal and an abnormal posterior fossa. Methods A prospective study was conducted from 2006 through 2008 on 12 fetuses with an abnormal posterior fossa and 73 healthy control fetuses from 18 to 35 weeks' gestation. Three‐dimensional scans of the fetal head were performed in the axial plane, using static volume contrast imaging in the C‐plane. The vermian perimeter, cross‐sectional area, and superoinferior diameter were measured and compared between abnormal and normal fetuses using the Wilcoxon nonparametric test. Linear regression analysis was used to describe trends of the vermis during gestation. The z scores for perimeter, cross‐sectional area, and superoinferior diameter measurements in the abnormal posterior fossa group in each 2‐week interval were calculated. Results Twelve fetuses with an abnormal posterior fossa were recruited: 3 with a Blake pouch cyst, 1 vermian cyst, 1 enlarged cisterna magna, 2 Dandy‐Walker malformation, 4 partial vermian agenesis, and 1 hemicerebellar hypoplasia. The vermian cross‐sectional area was reduced significantly in the fetuses with an abnormal posterior fossa compared with the control fetuses starting at 18 to 19 weeks' gestation (P = .01); the mean vermian superoinferior diameter was lower only from 22 to 23 weeks (P = .01); and the mean vermian perimeter was decreased from 28–29 weeks' gestation (P = .03). Linear regression analysis of the parameters showed that fetuses with an abnormal posterior fossa had a statistically significantly lower growth rate than control fetuses during gestation (P < .001). Conclusions Measurements of the cross‐sectional area were more useful than those of the perimeter and superoinferior diameter in distinguishing between fetuses with a normal and an abnormal posterior fossa during the early stages of gestation.

Cerebellar vermis area versus perimeter

“…Also perimeter estimate would be (3.14 Â 22) ¼ 69 mm. This latter perimeter estimate is more in keeping with Figure 5B and also with work by Bertucci [2] who reports on vermis perimeter.…”

“…Figure 5B shows CV ''area'' to range from about 35 to 63 mm 2 . This graphed ''area'' is significantly smaller than expected when doing a rough arithmetic calculation that uses their reported CV length as a reference to determine expected area.…”

Normal Fetal Posterior Fossa in MR Imaging: New Biometric Data and Possible Clinical Significance

“…1,11,22 Therefore, the exact diagnosis and accurate prognosis given to the soon-to-be parents are crucial for the their understanding of the consequences of these malformations. The establishment of a diagnosis of PF malformation is based on several parameters, including anatomy, morphology, and biometry.…”

“…Formerly, normal biometric data were taken mainly from studies of PF biometry in ultrasonographic imaging. [8][9][10][11][12] However, MR imaging has advantages over sonography when assessing fetal PF, such as better accuracy when evaluating the vermis and better contrast resolution, which enable evaluation of the brain stem. 13,14 Therefore, during the past 2 decades, MR imaging has become an important tool to prenatally evaluate the morphology of the PF, and many studies have been published to supply valid MR imaging biometric data.…”

Endoscopic third ventriculostomy is a safe and effective procedure for the treatment of Blake's pouch cyst

“…hemispheres and vermis, the choroid plexus of the fourth ventricle, the subarachnoid cisterns of the posterior fossa, and the surrounding meningeal structures [10][11][12] . Considering clinical aspects, DWC cysts are often related to other developmental anomalies and very commonly involve hydrocephalus, with greater motor rather than cognitive impairment in most cases 8,9,13 .…”