Figure 4. Coronal cerebral T2-weighted magnetic resonance images. A: Patient I-1 from Family 3. Dashed arrow shows severe hypogenesis of the corpus callosum with small amount of remnant tissue localized at the virtual connection between the genu and the body of the corpus callosum; arrow head shows the atrophic optic chiasm. B: Normal MRI images. Dashed arrow shows normal corpus callosum and arrow head shows normal optic chiasm. C: Patient I-1 from Family 3. Dashed arrow shows lateral callosal bundles of Probst, which are hemispheric connection fibers that did not cross the midline and that are seen in callosal dysgenesis. Superomedial margins of the lateral ventricles are indented by the Probst bundles. Arrow head shows remnants of the corpus callosum. Lower arrow shows normal posterior commissure. D: Normal MRI image with dashed arrow pointing normal corpus callosum.