Alobar holoprosencephaly - antenatal

Case contributed by Dr Ammar Haouimi

Presentation

G2P1 at 16 weeks gestation. Routine ultrasound.

Patient Data

Age: 30 years
Gender: Female
Ultrasound

The ultrasound images demonstrate:

  • the supratentorial cerebral parenchyma is replaced by a large central monoventricle with a thin rim of peripheral parenchyma
  • fused thalami
  • absent midline structures (septum pellucidum, corpus callosum, and falx cerebri)
  • hypotelorism
  • small midline structure of the fetal forehead suggestive of a proboscis
Annotated image

Annotated images:

  • white arrow: small midline structure of the fetal forehead suggestive of a proboscis
  • yellow arrow: hypotelorism
  • red arrows: rim of cerebral cortex
  • blue arrows: fused thalami

Case Discussion

Ultrasound findings most consistent with alobar holoprosencephaly

The main differential diagnosis includes:

  • hydranencephaly
    • thalami usually visible and not fused
    • falx cerebri usually present
    • no associated midline facial abnormalities
    • no cortex present, or sometimes small islands of tissue
  • severe hydrocephalus
    • thalami not fused
    • no associated midline facial abnormalities
    • falx cerebri usually present
    • bilateral choroid plexus

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