Presentation
22 year-old prima gravida with standard risk for down syndrome. No peculiar history.
Patient Data
No obvious abnormal findings.
-A sharp eye may doubt on the skull shape and frontal bones.
-Both choroid plexuses largely fill both lateral ventricles, which is a normal finding. (Choroid plexuses not filling lateral ventricles in first-trimester US is predictive of ventriculomegaly at later stages).
-A shap eye may doubt on the spine shape.
Morphology of other organs otherwise normal at this stage (not shown).
Skull shape abnormal with flattening of frontal bones : "lemon"-shaped skull = lemon sign
Ventriculomegaly
Elongated and curved cerebellum, due to ptosis through foramen magnum : "banana"-shaped cerebellum = banana sign
Spine anomaly with spina bifida aperta, dural sac is exposed to amniotic fluid, no CSF nor cord outpouching : myeloschisis.
Lemon, banana + spina bifida = Chiari II malformation.
Abnormal angle at lumbo-sacral junction with excessive flexion of the spine.
Unilateral clubfoot, as a consequence of spina bifida.
Ruling out underlying Meckel-Gruber syndrome : absence of postaxial polydactyly, absence of cystic or hyperechoic kidneys.
Case Discussion
Typical findings of a chiari II malformation.
Most spina bifida are linked to folate B9 vitamin deficiency. However ruling out a syndromic condition is of paramount importance for the next pregnancy and genetic counseling. Some spina bifida are part of a spine dysostosis, or larger defects of the caudal pole, or a ciliopathy such as the classical Meckel Gruber syndrome.
Dr S. De Gery and Dr T.Abossolo also significantly contributed to this case.