The location of the ruptured aneurysm is significant in regard to survival time. In women older than 20, the most common location is along the internal carotid artery. Two hypotheses explain the development of intracranial aneurysms. A cause-effect relationship between rupture and head trauma has been investigated, but only weak associations have been made. It is difficult to make a claim that head trauma precipitated rupture of an aneurysm, because rupture may have been part of the natural course.
Rupture is often a catastrophic, terminal event in the natural history of a berry aneurysm.
If the aneurysm is located in the anterior half of the circle of Willis, subarachnoid hemorrhage will be basal, extending into the interpeduncular fossa and over the convexities of the frontal and parietal lobes, causing meningeal irritation with cortical edema. If the aneurysmal sac is embedded in the cortex, there may be intracerebral or intraventricular hemorrhage leading to obstruction of the aqueduct by blood, with subsequent hydrocephalus. Accumulation of a large localized hematoma or hydrocephalus will produce increased mass effect, possibly with herniations and ischemia.3 Subdural hemorrhages may occur if there is dissection of an intracerebral hematoma through the leptomeninges. The underlying mechanism is not known but may be due to vasospasm, pressure effects from hematomas, concomitant atherosclerosis, hypotension, or local tamponade. Exertion has been linked to aneurysm rupture but is not present in every case.