A closed head injury is a type of traumatic brain injury in which the skull remains unopened. That is, the brain is not exposed, and not objects penetrate the bones of the head.
Even though the injury can have few visible signs, a closed head injury can cause a concussion, bleeding inside the skull and loss of brain tissue. Also, skull fractures can occur even if the skin does not break. Seeking immediate medical attention after any serious blow to the head is essential and can be life-saving.