Alobar holoprosencephaly: prenatal ultrasound 1st trimester

Case contributed by Fabien Ho
Diagnosis certain


Routine 1st trimester echography. Non relevant past history.

Patient Data

Age: 15 WG
Gender: Unknown

Normal skull shape, normal posterior fossa and cerebellum for 15 weeks of pregnancy.

No midline falx, fused thalami, single ventricle with a single choroid plexus.

3D examination of the face is consistent with unfused maxillary buds (facial cleft).

Case Discussion

Typical findings of holoprosencephaly in its alobar form as it's supposed to be imaged in the first trimester. 

Holoprosencephaly may be associated to other midline defects and may be part of an aneuploidy such a trisomy 13 (Patau's syndrome).

Lack of prosencephalus division at a later stage either leads to semilobar holoprosencephaly or lobar prolosencephaly. The latter may be a challenging differential diagnosis to septal agenesis.


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