V. Subarachnoid Hemorrhage and Intracranial Aneurysms
Aneurysms are abnormal localized dilatations in arteries. The most common non-traumatic cause of clinically significant subarachnoid hemorrhage is rupture of a berry aneurysm.
A. Characteristics of berry aneurysms (saccular or congenital aneurysms; most common type)
1. Prevalence: Aneurysms occur in about 1-5% of the population (most of these are asymptomatic).
2. Structure: The walls are composed of adventitia and intima only; the muscular and elastic coats are absent.
3. Most common sites: In adults, aneurysms most commonly occur at bifurcations of vessels at the base of the brain, especially in the anterior circulation
4. Sequelae: Rupture is the most common sequel, with subarachnoid hemorrhage occurring most often. In addition, aneurysm enlargement may exert local pressure on adjacent structures. |