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A subarachnoid hemorrhage (SAH) occurs when
a cerebral aneurysm, an
outpouching of a cerebral artery, ruptures, causing bleeding
into the subarachnoid
space. It is estimated that approximately 10 to 15 million
Americans have some
type of an intracranial aneurysm. Most of these aneurysms are
small, do not
rupture throughout the person's life, and are identified only
at the time of autopsy.
However, each year in the United States, 30,000 people have a
subarachnoid
hemorrhage due to the rupture of a major cerebral aneurysm.
Despite significant advances in diagnostic and surgical
techniques, the prognosis
for patients with a subarachnoid hemorrhage is poor. The
combined morbidity and
mortality rate for subarachnoid hemorrhage is between 60 and
70%. Thus, only
about one-third of persons who have a SAH will survive the
event in a functional
state without major disability. The economic and personal
costs of acute care and
rehabilitation for those with SAH are enormous.
SAH occurs most often in people between 35 and 60 years of
age, with a peak
mean age of 50. SAH is more prevalent in women than in men,
with a ratio of 3
women to 2 men. Approximately 15-20% of individuals with
cerebral aneurysms
have more than one aneurysm.