Teenager with developmental delay

MRI of semilobar holoprosencephaly
Axial (above), coronal (below left) and sagittal (below right) T1 MRI without contrast of the brain shows fusion of the frontal lobes, partial development of the posterior falx and occipital horns and separation of the occipital lobes, absent septum pellucidum, and hypoplasia of the corpus callosum.

The diagnosis was semilobar holoprosencephaly.