What are the viking helmet and car racing signs?
The viking helmet appearance refers to the lateral ventricles in coronal projection in patients with dysgenesis of the corpus callosum. The cingulate gyrus is everted into narrowed and elongated frontal horns. The racing car sign refers to widely spaced lateral ventricles due to agenesis of the corpus callosum with intervening Probst bundles. Appearances on axial MRI or CT are reminiscent of a formula one car seen from above, with the tires represented by the widely spaced frontal horns, and the dilated trigones (colpocephaly).
MRI study shows:
- a complete absence of the corpus callosum
- absent cingulate sulcus with the medial hemispheric sulci seen reaching the third ventricle in a radial fashion
- dilated high riding third ventricle
- parallel configuration of the lateral ventricles
On axial views, the ventricles appear similar to a racing car, and in coronal views, they appear similar to a viking helmet or a moose head.