Semilobar holoprosencephaly

Findings

Partial formation of the interhemispheric fissure and falx cerebri in the posterior portions of the brain. Fusion of the frontal lobes. Rudimentary temporal horns of the lateral ventricles. Absent septum pellucidum. Lack of a corpus callosum genu or anterior body. Partial fusion of the thalamus and caudate and hypothalamus are not clearly separated resulting in a small third ventricle.


Diagnosis: Semilobar holoprosencephaly


Key points

There are three types of holoprosencephaly: alobar, semilobar, and lobar.
Semilobar holoprosencephaly represents a congenital brain malformation with severity between alobar and lobar holoprosencephaly.
Clinical findings include microcephaly, macrocephaly, developmental delay, spasticity, or other motor abnormalities.
Imaging findings: Interhemispheric fissure and falx cerebri are partially formed posteriorly, and the anterior portions of the brain are fused and underdeveloped. Septum pellucidum is absent. The splenium of the corpus callosum is present with absence anteriorly of the genu. Anterior extent of corpus callosum formation correlates with remainder of the brain's formation. The hypothalami, caudate, and thalami are partially unseparated resulting in a small 3rd ventricle. Dorsal cysts may be seen, always when the thalami are fused.