Holoprosencephaly

Listed are the pathologies that closely resemble each other, and these pathologies are the favourite questions in final FRCR part A exam.

HOLOPROSENCEPHALY

	Alobar	Semilobar	Lobar
1	Most severe form	‘intermediate’ severity	Least severe form
2	Falx absent	Falx partially formed	All 3 including the corpus callosum may be nearly NORMAL
3	3rd ventricle absent	Rudimentary 3rd ventricle
4	Fusion of cerebral hemispheres, thalami & single lateral ventricle	Variable cleavage of thalami, lateral ventricles & cerebral hemispheres
5	Absent corpus callosum Absent olfactory nerves / optic nerves	Partially formed occipital horns Minimally developed temporal horns	Paired cerebral hemispheres Paired lateral ventricles Single fused frontal horn Dysplastic frontal lobe Thalami are separated
6	Absent septum pellucidum
7	A/w Midline facial abnormality, eg Cyclopia, Hypertelorism
Septo-optic dysplasia
1	Part of the holoprosencephaly spectrum
2	Cranial nerve 2 hypoplasia PLUS Absent septum pellucidum
3	Hypothalamic-pituitary dysfunction (60%)
4	A/w Schizencephaly, Seizure, Chiari II malformation
5	Risk factors: Maternal DM, CMV infection, Drug (Quinidine, Anti-epileptic, Illicit drugs)