Callosal agenesis
absence of a well-defined cingulate sulcus, resulting in near-continuous radiation of mesial surface sulci to the third ventricle. Associated findings on the sagittal image in this case are hypoplasia of the fornix, as well as prominence of both the anterior commissure and massa intermedia of the thalamus.
The coronal image shows eversion of the cingulate gyri and continuation of the interhemispheric fissure all the way to the roof of the third ventricle. The frontal horns show characteristic morphology, as they are indented by the everted cingulate gyri and the bundles of Probst, representing the uncrossed callosal fibers. Dysmorphic configuration of the temporal horns of the lateral ventricles is due to hypoplasia of the hippocampus bilaterally, a common association.
T1-weighted images show the widely separated frontal horns and the obliquely oriented bundles of Probst. Note markedly dilated atria of the lateral ventricles (colpocephaly) and hypoplasia of the parietal white matter.
T2-weighted images show the widely separated frontal horns and the obliquely oriented bundles of Probst. Note markedly dilated atria of the lateral ventricles (colpocephaly) and hypoplasia of the parietal white matter.
