Congenital malformation of the brain
Cranial fissures are more likely to occur in the midline of the skull, and can occur at the top and base of the skull. They are more common in the occipital region, but can also be seen in the frontal region; those at the base of the skull can bulge from the root of the nose, nasal cavity, nasopharyngeal cavity, or eye sockets. In some cases, they can bulge to the side. Hidden cranial fissures have no mass on the surface. Cystic cranial fissures can be divided into meningocele or meningoencephalocele, the latter of which contains tissue in the cyst, or partially dilated ventricles. In this case, the head is often small, and the bulging part is particularly large. The base of the mass may be large or small.