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Appearance of the fetal posterior fossa at 11 + 3 to 13 + 6 gestational weeks on transabdominal ultrasound examination
Author(s) -
Egle D.,
Strobl I.,
WeiskopfSchwendinger V.,
Grubinger E.,
Kraxner F.,
MutzDehbalaie I. S.,
Strasak A.,
Scheier M.
Publication year - 2011
Publication title -
ultrasound in obstetrics and gynecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.202
H-Index - 141
eISSN - 1469-0705
pISSN - 0960-7692
DOI - 10.1002/uog.8957
Subject(s) - medicine , cisterna magna , fetus , ultrasound , gestational age , fourth ventricle , posterior fossa , fetal head , posterior cranial fossa , crown rump length , nuclear medicine , anatomy , pregnancy , radiology , first trimester , cerebrospinal fluid , biology , genetics
Abstract Objectives To describe the sonographic appearance of the structures of the posterior cranial fossa in fetuses at 11 + 3 to 13 + 6 weeks of pregnancy and to determine whether abnormal findings of the brain and spine can be detected by sonography at this time. Methods This was a prospective study including 692 fetuses whose mothers attended Innsbruck Medical University Hospital for first‐trimester sonography. In 3% ( n = 21) of cases, measurement was prevented by fetal position. Of the remaining 671 cases, in 604 there was either a normal anomaly scan at 20 weeks or delivery of a healthy child and in these cases the transcerebellar diameter (TCD) and the anteroposterior diameter of the cisterna magna (CM), measured at 11 + 3 to 13 + 6 weeks, were analyzed. In 502 fetuses, the anteroposterior diameter of the fourth ventricle (4V) was also measured. In 25 fetuses, intra‐ and interobserver repeatability was calculated. Results We observed a linear correlation between crown–rump length (CRL) and CM (CM = 0.0536 × CRL − 1.4701; R 2 = 0.688), TCD (TCD = 0.1482 × CRL − 1.2083; R 2 = 0.701) and 4V (4V = 0.0181 × CRL + 0.9186; R 2 = 0.118). In three patients with posterior fossa cysts, measurements significantly exceeded the reference values. One fetus with spina bifida had an obliterated CM and the posterior border of the 4V could not be visualized. Conclusions Transabdominal sonographic assessment of the posterior fossa is feasible in the first trimester. Measurements of the 4V, the CM and the TCD performed at this time are reliable. The established reference values assist in detecting fetal anomalies. However, findings must be interpreted carefully, as some supposed malformations might be merely delayed development of brain structures. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.