Holoprosencephaly vs Anencephaly
How to tell Holoprosencephaly and Anencephaly apart when a board question makes them look alike.
Holoprosencephaly is failed forebrain separation; anencephaly is failed anterior neuropore closure.
Side by side
Holoprosencephaly is failed forebrain division, associated with midline facial defects, cyclopia, cleft lip/palate, and trisomy 13.
Anencephaly is failed anterior neuropore closure causing absent cranial vault/forebrain, elevated AFP, and polyhydramnios.
Holoprosencephaly is failed forebrain division, associated with midline facial defects, cyclopia, cleft lip/palate, and trisomy 13.
Anencephaly is failed anterior neuropore closure causing absent cranial vault/forebrain, elevated AFP, and polyhydramnios.
The repair move
Before naming the answer, force the stem through the separator: Holoprosencephaly is failed forebrain separation; anencephaly is failed anterior neuropore closure.
Try a free question
CoreA newborn with trisomy 13 has midline facial defects (cyclopia with a single midline eye, proboscis), microcephaly, cleft lip/palate, and seizures. Brain MRI shows failure of separation of the cerebral hemispheres with a single ventricle and fused thalami. Which condition is most likely?
Show answer and explanation
Answer: A. Holoprosencephaly. Holoprosencephaly is failed division of the embryonic forebrain (prosencephalon) into right and left hemispheres. Severity ranges from alobar (single ventricle, fused thalami, severe facial defects with cyclopia, proboscis) to semilobar to lobar (milder). Strongly associated with trisomy 13 (Patau syndrome) and Sonic Hedgehog signaling disruption.
Why the other choices are tempting
- B. Anencephaly is failed anterior neuropore closure with ABSENT cranial vault and forebrain.
- C. Hydranencephaly is destruction of cerebral hemispheres with CSF replacing brain (intact skull).
- D. Schizencephaly is a cleft extending from the cortex to the ventricle.
- E. Lissencephaly is smooth brain from neuronal migration failure.
Flashcards
Tap a card to flip it.
What clue supports Holoprosencephaly?
Choose Holoprosencephaly when the stem gives this pattern: Holoprosencephaly is failed forebrain division, associated with midline facial defects, cyclopia, cleft lip/palate, and trisomy 13.
What clue supports Anencephaly?
Choose Anencephaly when the stem gives this contrasting pattern: Anencephaly is failed anterior neuropore closure causing absent cranial vault/forebrain, elevated AFP, and polyhydramnios.
Quick answers
What is the fastest way to tell Holoprosencephaly from Anencephaly?
Holoprosencephaly is failed forebrain separation; anencephaly is failed anterior neuropore closure.
What is the key clue for Holoprosencephaly?
Holoprosencephaly is failed forebrain division, associated with midline facial defects, cyclopia, cleft lip/palate, and trisomy 13.
What is the key clue for Anencephaly?
Anencephaly is failed anterior neuropore closure causing absent cranial vault/forebrain, elevated AFP, and polyhydramnios.