Assessment of fetal midbrain and hindbrain in mid-sagittal cranial plane by three-dimensional multiplanar sonography. Part 2: application of nomograms to fetuses with posterior fossa malformations.
OBJECTIVE
To apply fetal midbrain (MB) and hindbrain (HB) nomograms, developed using three-dimensional multiplanar sonographic reconstruction (3D-MPR) in the mid-sagittal cranial plane, to fetuses with known posterior fossa malformations.


METHODS
In this retrospective study we examined sonographic volumes obtained by sagittal acquisition in 43 fetuses diagnosed with posterior fossa abnormalities and evaluated in the mid-sagittal cranial plane, using 3D-MPR, the following: MB parameters tectal length (TL) and anteroposterior midbrain diameter (APMD), and HB parameters anteroposterior pons diameter (APPD), superoinferior vermian diameter (SIVD) and anteroposterior vermian diameter (APVD). Fetuses were grouped, according to malformation, into eight categories: cobblestone malformation complex (CMC, n = 3), Chiari-II malformation (C-II, n = 7), pontocerebellar hypoplasia (PCH, n = 2), rhombencephalosynapsis (RES, n = 4), Dandy-Walker malformation (n = 8), vermian dysgenesis (VD, n = 7), persistent Blake's pouch cyst (n = 6) and megacisterna magna (n = 6). In each case and for each subgroup, the MB-HB biometric parameters and their z-scores were evaluated with reference to our new nomograms.


RESULTS
The new MB-HB nomograms were able to identify the brainstem and vermian anomalies and differentiate fetuses with MB-HB malformations from those with isolated enlarged posterior fossa cerebrospinal fluid spaces. Use of the nomograms enabled detection of an elongated tectum in fetuses with CMC, C-II and RES, and a flattened pontine belly in cases of CMC, PCH and VD. In the fetuses with VD, the nomograms enabled division into three distinctive groups: (1) those with small SIVD and APVD, (2) those with normal SIVD but small APVD, and (3) those with small SIVD but normal APVD.


CONCLUSIONS
Application of our new reference data, that for the first time include the MB, enables accurate diagnosis of brain malformations affecting the MB and HB and makes possible novel characterization of previously described features of posterior fossa anomalies.
Unit of Fetal Neurology and Prenatal Diagnosis, Department of Obstetrics and Gynecology, Wolfson Medical Center, Holon, Israel, affiliated with the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Obstetrics and Gynecology, Bnai Zion Medical Center, Haifa, Israel.
Z
Z
Leibovitz
C
C
Shkolnik
K Krajden
KK
Haratz
G
G
Malinger
I
I
Shapiro
T
T
Lerman-Sagie
D001139:Arnold-Chiari Malformation / Q000000981:diagnostic imaging / Q000196:embryology / Q000473:pathology; D002526:Cerebellar Diseases / Q000000981:diagnostic imaging / Q000196:embryology / Q000473:pathology; D003388:Cranial Fossa, Posterior / Q000002:abnormalities*; D003616:Dandy-Walker Syndrome / Q000000981:diagnostic imaging / Q000196:embryology / Q000473:pathology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008636:Mesencephalon / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000196:embryology; D009421:Nervous System Malformations / Q000000981:diagnostic imaging*; D049451:Nomograms; D009929:Organ Size; D012189:Retrospective Studies; D012249:Rhombencephalon / Q000002:abnormalities* / Q000000981:diagnostic imaging; D016216:Ultrasonography, Prenatal / Q000379:methods
3D ultrasound; CNS malformations; hindbrain; midbrain; nomogram; pons; posterior fossa malformations; vermis