SPR Unknown # 100 -- FINAL
Publication Date: 2013-11-06
Fetal MRI shows agenesis of corpus callosum with parallel lateral ventricles and central extension of the interhemispheric fissure. Additional findings include subependymal heterotopias, cyst at left foramen of Luschka, and a coloboma of the right eye. Post-natal MRI of the infant confirmed these findings.
The corpus callosum is made up of commissural fibers that connect the cerebral hemispheres. The callosum consists of rostrum, genu, body and splenium from anterior to posterior. Partial agenesis/dysgenesis of the corpus callosum is typified by presence of genu and anterior body with absence of the posterior body. This pattern of posterior body absence is often found in patients with myelomeningocele/Chiari 2 malformation. Localized absence of the anterior or central corpus callosum is often associated with lobar forms of holoprosencephaly
- Gyri radiating towards the third ventricle.
- Inversion of the cingulate gyrus.
- Probst bundles: White matter tracts that would have normally crossed in the corpus callosum run in anteroposterior direction medial to the lateral ventricles.
- High riding third ventricle.
- Colpocephaly: Enlarged occipital horns. Parallel running lateral ventricles on axial view. Lateral ventricles pointing superiorly. Viking helmet or trident shape.
- Meandering anterior cerebral artery
- Diffusion tractography has been used in prenatal and post-natal MRI to demonstrate non-crossing of fibers.
Heterotopias are a form of migration anomaly with ectopic gray matter abnormally located within the white matter due to failure of migration of fetal neurons to the cerebral cortex. Subependymal heterotopias are usually nodular collections of gray matter located along the lining of the lateral ventricles. Subcortical heterotopias are located in the cerebral white matter either as islands of gray matter or as extensions of the cortex. Band heterotopias form two layers of cortex separated by white matter.
Coloboma of the eye is deficiency of ocular tissue. Optic disc coloboma has defect at the site of insertion of optic nerve. Choroidoretinal coloboma has a defect in the choroid, retina or both which can be partial or complete. Abnormal shape of the globe is seen in coloboma and there may be an associated cyst behind the globe.