Alobar holoprosencephaly

Q: What is the diagnosis? show answer

A: Alobar holoprosencephaly.

Q: What three types of holoprosencephaly are recognised (list them in order of increasing severity)? show answer

A: Lobar, semilobar and alobar (most severe).

Q: What are the main differentials, and what features enable you to make the distinction between these entities? show answer

A: 1. Semilobar holoprosencephaly: partial separation into hemispheres; rudimentary occipital and temporal horns. 2. Hydranencephaly: thalami are often visible and are not fused; not associated with midline facial abnormalities; no cortex present, or sometimes small islands of tissue; falx usually present. 3. Severe hydrocephalus: falx usually present; bilateral choroid plexus present; thalami not fused; not associated with midline facial abnormalities.

Q: What configurations can the cortex present in alobar holoprosencephaly take? show answer

A: 1. Pancake: cerebral tissue is confined to the anterior basicranium. 2. Cup: cerebral tissue lines variable amounts of the anterior cranium with a dorsal cyst present posteriorly (this case). 3. Ball: a complete rim of tissue surrounds the monoventricle without dorsal cyst.

Q: What additional abnormalities are visible (there are three anteriorly and one posteriorly)? show answer

A: 1. bony defect in the occipital bone with an occipital meningiocele. 2. cleft lip and palate. 3. under-developed nose 4. hypoteloresim.