Subaracnoid Hemorrhage Non-traumatic

General Information Subarachnoid hemorrhage (SAH) affects approximately 30,000 individuals per year in the United States, with an annual incidence of 1 per 10,000. In most populations primary non-traumatic SAH accounts for 5 to 9% of all strokes. SAH as the result of aneurysms is about 10 to 11 per 100,000 populations in Western Countries, with somewhat higher frequencies in the United States and Finland and among the Asian countries, Japan. It is lower in New Zealand and the other Scandinavian countries. Intracranial aneurysms are uncommon in children, being found in association with coarctation of the aorta or hypertension due to renal disease. In adults, intracranial aneurysms occur with a frequency of 2%, so that 2 to 3 million Americans have aneurysms. More than 90% of these aneurysms are small, less than 10 mm, and remain asymptomatic throughout the patient's life. The annual risk of rupture of an asymptomatic aneurysm is approximately 0.7%. Important risk factors for rupture are increasing size, prior SAH from a separate aneurysms, and basilar apex and posterior communicating artery location. At all ages the presence of an aneurysm tends to parallel the height of the blood pressure. This is clearly demonstrated by the sudden change in sex ratio after the age of 50. Up until 50 the ratio of females to males with aneurysm is 3:2. Over 50 it rises to 10:1. This is believed to be due to the better long-term survival of females with significant hypertension, leading to the development of aneurysms in the 50 to 70 age group. The annual incidence of aneurysmal subarachnoid hemorrhage increases linearly with age, from less than 1 per 100,000 before the age of 20 years to about 23 per 100,000 after the age of 60. The median age of onset of the first subarachnoid hemorrhage is 50 to 60 years. Women are affected more often than men. The rate of rupture of saccular aneurysm is estimated at approximately 1 to 2% per year. Aneurysms in general increase in size with time. It appears the primary determining