Spina bifida: myeloschisis with Chiari II - prenatal diagnosis

Case contributed by Dr Fabien Ho

Presentation

22 year-old prima gravida with standard risk for down syndrome. No peculiar history.

Patient Data

Age: Fetus
Gender: Female

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.

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Case information

rID: 59513
Published: 17th Apr 2018
Last edited: 19th Apr 2018
Inclusion in quiz mode: Included
Institution: CHU de la Reunion

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