Agenesis of the corpus callosum

Case contributed by Alexandra Stanislavsky


21w3d GA. Morphology ultrasound


Neurosonography demonstrates non-visualization of the corpus callosum, dorsal expansion of the 3rd ventricle forming a small interhemispheric cyst, a widened interhemispheric fissure, and colpocephaly with mild dilation of both ventricles (right: 10.5mm left : 11.4mm). Abnormal configuration of pericallosal artery further supports the diagnosis.

MRI performed at 22 weeks GA


The lateral ventricles demonstrate posterior colpocephaly and parallel configuration in keeping with callosal dysgenesis.

Left lateral ventricle measures 11.5 mm and right 9.6 mm. The third ventricle is high riding measuring 2 mm in diameter. The fourth ventricle measures 3 mm in AP diameter.
Overlying CSF spaces are normal for age.

The corpus callosum appears completely absent with no crossing fibers identified.
Left cerebral hemisphere has normal morphology and zonal anatomy.
The right cerebral hemisphere demonstrates irregular cortical contour with associated abnormal parenchymal morphology affecting the medial frontal and parietal regions with sparing of the occipital lobe. These features are in keeping with a widespread cortical migrational abnormality

The cerebellar hemispheres and vermis have normal morphology with normal vermian herniation and lobules.
Normal tegmentovermian angle, retro-cerebellar CSF space, pre-pontine space, and brain stem.  No foci of diffusion on DWI or susceptibility artefact on SWI (the latter not shown here)

Case Discussion

Ultrasound and MRI features of complete callosal agenesis. Note additional finding of a cortical migrational anomaly involving the right cerebral hemisphere on MRI. This is a significant finding in terms of neurodevelopmental prognosis.

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