A skull fracture is a break in one or more of the bones in the skull cause by a head injury. Isolated skull fractures are not very serious injuries, but the presence of a skull fracture may indicate that significant enough impact occurred to cause brain trauma, which is quite serious. Broken fragments of skull can lacerate or bruise the brain or damage blood vessels. If the fracture occurs over a major blood vessel, significant bleeding can occur within the skull, so head injury patients with skull fracture have many more intracranial hematomas (especially epidural hematomas) than those without fractures. Another complication of skull fractures is dissection of cerebral arteries, which can limit blood flow to the brain. However, the bone fracture helps dissipate energy from a blow, so less force is transmitted to the brain, so having a skull fracture is not a good predicter of intracranial injury.