Anatomy
The human skull is anatomically divided into two parts: the neurocranium, formed by eight cranial bones that houses and protect the brain—and the facial skeleton (viscerocranium) composed of fourteen bones, not including the three ossicles of the inner ear. The term skull fracture typically means fractures to the neurocranium, while fractures of the facial portion of the skull are facial fractures, or if the jaw is fractured, a mandibular fracture.The eight cranial bones  are separated by sutures : one frontal bone, two parietal bones, two temporal bones, one occipital bone, one sphenoid bone, and one ethmoid bone.The bones of the skull are in three layers: the hard compact layer of the external table (lamina externa), the diploë (a spongy layer of red bone marrow in the middle, and the compact layer of the inner table (Lamina interna).Skull thickness is variable, depending on location. Thus the traumatic impact required to cause a fracture depends on the impact site. The skull is thick at the glabella, the external occipital protuberance, the mastoid processes, and the external angular process of the frontal bone.
Basilar fractures have characteristic signs: blood in the sinuses; cerebrospinal fluid rhinorrhea (CSF leaking from the nose) or from the ears (cerebrospinal fluid otorrhea); periorbital ecchymosis  often called raccoon eyes (bruising of the orbits of the eyes that result from blood collecting there as it leaks from the fracture site); and retroauricular ecchymosis known as "Battles sign" (bruising over the mastoid process). Growing fracture
A growing skull fracture (GSF) also known as a craniocerebral erosion or leptomeningeal cyst due to the usual development of a cystic mass filled with cerebrospinal fluid is a rare complication of head injury usually associated with linear skull fractures of the parietal bone in children under 3. It has been reported in older children in atypical regions of the skull such as the basioccipital and the base of the skull base and in association with other types of skull fractures. It is characterized by a diastatic enlargement of the fracture.Various factors are associated with the development of a GSF. The primary causative factor is a tear in the dura mater. The skull fracture enlarges due, in part, to the rapid physiologic growth of the brain that occurs in young children, and brain cerebrospinal fluid (CSF) pulsations in the underlying leptomeningeal cystic mass. Cranial burst fracture
A cranial burst skull fracture, usually occurring with severe injuries in infants less than 1 year of age, is a closed, diastatic skull fracture with cerebral extrusion beyond the outer table of the skull under the intact scalp.Acute scalp swelling is associated with this type of fracture.