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(D)Corpus Callosum Anomalies
Corpus callosum forms from anterior to posterior except for the rostrum, which is formed last. Callosal agenesis may be complete or partial. In partial agenesis, splenium and rostrum are the missing parts. In complete agenesis the entire corpus callosum and the cingulate sulcus and gyrus are absent.
Imaging of complete callosal agenesis (Figure 4) shows high riding third ventricle with spoke-like orientation of gyri around it. Lateral ventricles are widely separated, parallel and non-converging. Colpocephaly (dilated occipital horns) is commonly present and frontal horns may be small and pointed. Lateral ventricles are indented superomedially by the longitudinal white matter bundles (Probst bundles) 1].
Callosal anomalies are associated with other anomalies in 50 per cent of cases. These anomalies include Chiari malformations, heterotopias, lissencephaly, schizencephaly, Dandy-walker malformation, holoprosencephaly and lipomas 6. Association with Aicardi syndrome is reported 7.
Figure : Corpus callosum agenesis:
Corpus callosum forms from anterior to posterior except for the rostrum, which is formed last. Callosal agenesis may be complete or partial. In partial agenesis, splenium and rostrum are the missing parts. In complete agenesis the entire corpus callosum and the cingulate sulcus and gyrus are absent.
Imaging of complete callosal agenesis (Figure 4) shows high riding third ventricle with spoke-like orientation of gyri around it. Lateral ventricles are widely separated, parallel and non-converging. Colpocephaly (dilated occipital horns) is commonly present and frontal horns may be small and pointed. Lateral ventricles are indented superomedially by the longitudinal white matter bundles (Probst bundles) 1].
Callosal anomalies are associated with other anomalies in 50 per cent of cases. These anomalies include Chiari malformations, heterotopias, lissencephaly, schizencephaly, Dandy-walker malformation, holoprosencephaly and lipomas 6. Association with Aicardi syndrome is reported 7.
Figure : Corpus callosum agenesis:
A, Axial CT scan of a patient with corpus callosum agenesis. Note the widely separated, parallel lateral ventricles with colpocephaly (Arrow). Left frontal horn is small and pointed (Curved arrow). Interdigitating gyri are seen (Arrowhead).
B, T1 weighted axial MR image shows classical widely separated, parallel lateral ventricles with colpocephaly. High riding third ventricle open superiorly to interhemispheric fissure is present (Arrow). There is presence of focal nodular heterotopia along lateral wall of frontal horn of left lateral ventricle (Arrowhead). C, Axial true inversion recovery image of a different patient. Prominent occipital horns (Arrows), high riding third ventricle (White dot), irregular interhemispheric fissure and heterotopias (Arrowheads) are visualized. Note that presence of heterotopias is better appreciated on this inversion recovery image.
D, Coronal T2 weighted image. Absence of corpus callosum is clearly visualized and third ventricle is open superior to interhemispheric fissure.
Reference:The Internet Journal of Radiology™ ISSN: 1528-8404
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