Reassessment of the Normal Fetal Cisterna Magna during Gestation and an Alternative Approach to the Definition of Cisterna Magna Dilatation

Abstract

Introduction: Cisterna magna (CM) measurement constitutes part of the sonographic assessment of the posterior fossa. CM enlargement (ECM) is defined as a measurement exceeding 10 mm, although it has previously been noted that the CM varies in size with gestation. Existing data do not appear to reflect observations regarding CM biometry within our population and this study was therefore undertaken in order to re-evaluate CM biometry. Materials and Methods: Data from 4,750 normal pregnancies between 15 and 32 weeks of gestation were collected and used to construct a reference range for the CM. Results: Regression analysis was used to model CM across gestational age and thereby define the upper limits for normal CM measurements across gestation. The CM increases with gestation. These data suggest that a 10-mm cut-off underestimates ECM, notably in the gestational age period below 24 weeks, whilst overestimating isolated ECM beyond this. Differences in CM measurements between genders were confirmed (p < 0.0001). Conclusions: Defining ECM based upon a cut-off of 10 mm across all gestations may be inappropriate given the variation observed with gestational age. More accurate identification of fetuses with, in particular, isolated ECM may facilitate more precise evaluation of the clinical significance of this finding.

A Systematic Review of Methodology Used in Studies Aimed at Creating Charts of Fetal Brain Structures

“…Excluded studies and reasons for exclusion are reported in Table S3 . Finally, 42 studies, reported between January 1970 and 2021, met the inclusion criteria, and these provided data for 45,626 fetuses, included in the final analysis ( Table 1 ) [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ]. The median sample size of participating fetuses was 372.5 (range: 50 to 8313; 25th percentile: 175.8; 75th percentile: 709.3).…”

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

“…30 Previous studies have reported this definition to be inaccurate, and it has been shown to vary with gestational age. 31,32 The cisterna magna is a fluid-filled space that is normally continuous with the subarachnoid space of the entire PF, between the foramen magnum and the tentorium cerebelli. We measured the cross-sectional area of the entire fluidfilled space in the midsagittal section (CMS) and the ratio between the vermian cross-sectional area and the CMS.…”

Outcome of isolated enlarged cisterna magna identified in utero: experience at a single medical center in mainland China

“…To obtain more precise, we further analyzed the influence of IECM according to the depth of the fossa. Richard suggested that defining an ECM based on a cutoff width of 10 mm for all gestations might be inappropriate because of variations among gestational ages. More accurate identification of fetuses with ECM, particularly IECM, may allow more precise evaluation of the clinical significance of the finding.…”