Holoprosencephaly: Embryology, Spectrum, and Fetal Imaging
A practical radiology review of Holoprosencephaly: Embryology, Spectrum, and Fetal Imaging, focused on imaging findings, differential diagnosis, reporting points, and...
RadPhrases Editorial Team1 min read
A practical radiology review of Holoprosencephaly: Embryology, Spectrum, and Fetal Imaging, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.
Embryology & Mechanism
- Ventral induction failure → incomplete prosencephalon cleavage (≈5th GW)
- !Continuum — not discrete categories
- Aprosencephaly/atelencephaly = formation defects
- Classic HPE (alobar→semilobar→lobar) = cleavage defects
- 》Middle Interhemispheric variant of HPE=MIH (syntelencephaly) = posterior frontal/parietal non-separation
Epidemiology / Etiology
- Most common forebrain–face malformation
- Severe forms largely lost in utero
- Trisomy 13 most classic; many syndromic associations
- SHH pathway central; multifactorial “multi-hit” model
- Teratogens: maternal DM (↑ risk), EtOH, RA etc.
Morphologic Spectrum (Key Imaging)
- Alobar — monoventricle, fused thalami, absent falx/CC/CSP + dorsal cyst
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