1. Head trauma is the most common cause. Traumatic SAH (tSAH) usually occurs near the site of a skull fracture or intracerebral contusion.[17] It usually happens in the setting of other forms of traumatic brain injury and has been linked with a poorer prognosis. It is unclear, however, if this is a direct result of the SAH or whether the presence of subarachnoid blood is simply an indicator of severity of the head injury and the prognosis is determined by other associated mechanisms.[19]