#Traumatic insanity# may follow injury to any part of the brain, and it may come on either immediately or after an interval. It may or may not be associated with epilepsy. Any form of insanity may occur, either as a direct result of the trauma, or from the resistance of the brain being lowered by the injury in a patient predisposed to insanity. When insanity follows as a direct consequence of injury, the organic lesion is usually a superficial one, and the disturbance of brain function is generally due to reflex irritation of the dura mater (Duret). These facts possibly explain the immediate improvement which occasionally follows the opening of the skull at the point of injury and removal of the exciting cause. Cases occurring within a few days of the injury usually recover within a month or two. The later the condition is in developing the less obvious is the relationship between the trauma and the insanity, and therefore the worse is the prognosis. _Meningitis_, _sinus thrombosis_, and _cerebral abscess_ may follow upon any form of head injury attended with infection. The clinical features--save for the history of a trauma--correspond so closely with those of the same conditions occurring apart from injury, that they are most conveniently considered together (p. 374). CHAPTER XIII INJURIES OF THE SKULL Contusions--FRACTURES--Of the vault: _Varieties_--Of the Base: _Anterior fossa_--_Middle fossa_--_Posterior fossa_. The bones of the skull may be contused or fractured. These injuries are not in themselves serious: their clinical importance is derived from the injury to the intra-cranial contents with which they are liable to be associated. #Contusion# of the skull may result from a fall, a blow, or a gun-shot injury. In the majority of cases the damage to soft parts--scalp, meningeal vessels, or brain--overshadows the osseous lesion, which of itself is comparatively unimportant. FRACTURES OF THE SKULL While it is convenient to consider separately fractures of the vault and fractures of the base of the skull, it is to be borne in mind that it is not uncommon for a fracture to involve both the vault and the base. Fractures in either situation may be simple or compound. FRACTURES OF THE VAULT