Holoprosencephaly

Etiology: cleavage failure – lateral: cerebral hemispheres and transverse: diencephalon and telencephalon, is continuum frin alobar (severe) -> semilobar – lobar (mild), abnormality of ventral induction with failure of cleavage of brain into 2 hemispheres, lobation of hemisphere occurs posterior to anterior – posterior brain can be separated but anterior brain still fused
Imaging:
— Alobar: severe craniofacial anomalies, monoventricle with holosphere: often midline dorsal cyst, absent midline structures (septum pellucidum, falx cerebri, interhemispheric fissure, corpus callosum), fused thalami and basal ganglia
— Semilobar: variable craniofacial anomalies, rudimentary ventricles with occipital and temporal horns, absent septum pellucidum, partial midline structures (posterior falx cerebri, interhemispheric fissure, splenium of corpus callosum present), partially separated thalami and basal ganglia, separation of occipital lobes
— Lobar: absent or mild craniofacial anomalies, squared off frontal horns of lateral ventricles, absent septum pellucidum, present midline structures (well-formed falx cerebri, interhemispheric fissure with mild inferior frontal fusion, body and splenium of corpus callosum present), separated thalami and basal ganglia, partial frontal lobe fusion with occipital/temporal/parietal lobes well formed, azygous anterior cerebral artery
— Septo-optic dysplasia: hypoplastic optic nerves/chiasm, hypoplasia / absence septum pellucidum
— Associations: hypothalamic – pituitary dysfunction in 60-70%, ectopic posterior pituitary gland, migrational anomalies – schizencephaly / gray matter heterotopia, overlap with lobar holoprosencephaly, white matter atrophy -> ventriculomegaly, corpus callosal agenesis, Chiari II malformation, cephaloceles
DDX:
Complications:
Treatment:
Clinical: alobar holoprosencephaly usually do not survive long after birth