Interhemispheric fissure sign of dysgenesis of the corpus callosum.

Failure to develop of the corpus callosum and the neighboring midline structures results in abnormal proximity between the interhemispheric fissure (IHF) and the third ventricle. We have called this finding the IHF sign of dysgenesis of the corpus callosum (DCC). In a retrospective study of 39 cases the presence of the IHF sign was assessed in conjunction with the other well recognized CT manifestations of the disorder. These are: (a) lateral ventricles: pointing of the frontal horns, disproportionate enlargement of the occipital horns and separation of bodies of the lateral ventricles; (b) third ventricle: enlargement, elevation and anterior displacement; and (c) interventricular foramen: enlargement. We found that the IHF sign was present concurrently with the other CT signs of DCC in all 35 cases (100%) where the quality of the CT scans permitted its satisfactory evaluation; in the remaining four the sign could not be assessed because of the unsatisfactory quality of the CT scans. Our study confirms that the IHF sign is an additional reliable CT feature of DCC.