What is the diagnosis?
Middle interhemispheric variant of holoprosencephaly, also known as syntelencephaly.
MRI of this child demonstrates dysmorphic lateral ventricles with absent septum pellucidum. Abnormal bridging grey matter is shown between the hemispheres along the level of the body of the corpus callosum with resultant thinning and irregular shape of the body of corpus callosum. The genu and splenium of the corpus callosum are relatively enlarged.
The majority of the falx appears deficient, particularly anteriorly and the anterior cerebral artery is azygous. The pituitary, optic chiasm and hypothalamus appear normal.
Features in keeping with the middle interhemispheric variant of holoprosencephaly, also known as syntelencephaly.