Integrating 2D and 3D Multiplanar Sonography in the Prenatal Diagnosis of Arnold-Chiari Type 2 Malformation

Abstract

Arnold-Chiari type 2 malformation is a congenital deformity characterized by displacement of cerebellar tonsils, parts of the corpus callosum, and the medulla oblongata through the foramen magnum into the spinal canal. Sonographic diagnostic criteria are based on the “lemon sign” of the cephalic pole, enlargement of the lateral ventricle, and abnormalities of the posterior fossa consisting of an anomalous profile of the cerebellar hemispheres (“banana sign”) associated with a reduced or absent cisterna magna. Identification of a large, open neural tube defect is the other hallmark of the prenatal sonographic diagnosis. Multiplanar 3D enhances the definition and the exact extension of the spine defect and has the potential of calculating the amount of cerebellar hemispheres undergoing herniation through the foramen of Magendie and Lutchka, which is one of the main factors in predicting or modifying the postnatal neurosurgery strategy and the subsequent postnatal neurodevelopmental outcome.