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INTRACEREBRAL ANEURYSMS
Frequently asked questions/answers prepared by:
Gary L. Bernardini, M.D., Ph.D.
Department of Neurology and Neuroscience
The New York Hospital/Cornell University Medical Center
1300 York Avenue
NY, NY 10021
1. What is an intracerebral aneursym?
An intracerebral aneurysm is a small, thin walled
outpouching or dilatation of one of the large blood
vessels that supply the brain. Aneurysms pose a risk to
health from the potential for rupture and subsequent
bleeding into the substance of the brain and/or the
fluid-filled spaces that surround the brain (the
subarachnoid space). These so-called saccular or berry
aneurysms occur at the bifurcation of the large blood
vessels at the base of the brain.
2. What causes aneuryms?
Intracerebral aneurysms can result from trauma,
infection, or neoplastic disease. Most aneurysms,
however, result from a developmental abnormality of the
inside lining or intima of an artery with abnormal
thinning of the vessel at the site of origin. It appears
there may be a genetic predisposition to the development
of intracerebral aneurysms; the existence in some
families runs as high as 10%, approximately 10 times
higher than that found in the general population. There
are several other causes of intracerebral aneurysms. For
example, they can result from infected embolic material
from a bacterial infection on one of the heart valves
being deposited on one of the arteries in the brain
(mycotic aneuryms).
3. Who is at greatest risk for aneurymal rupture?
Aneurysmal rupture leads to subarachnoid
hemorrhage (SAH) and occurs most often in patients
between 40 and 60 years of age with approximately equal
sex distribution. Cigarette smoking and excess alcohol
use have been shown to increase the risk of rupture.
Likewise, the existence of intracerebral aneurysms is
associated with other diseases such as polycystic kidney
disease, coarctation of the aorta, and fibromuscular
hyperplasia. Other factors such as high blood pressure
seem to be less important since aneurysms often occur in
persons with normal blood pressure. Pregnancy has not
been associated with an increased incidence of aneurysmal
rupture.
4. What are the symptoms of intracerebral aneurysmal
rupture?
Prior to rupture, saccular aneurysms are usually
asymptomatic. However, an expanding aneurysm can have a
"mass" effect causing problems with double vision, loss
of vision, numbness in the face, an enlarged pupil size,
or a drooping eyelid. Usually patients who have an
aneurysm rupture experience sudden onset of a severe
headache, often described as "the worst headache of my
life", frequently accompanied by transient loss of
consciousness and sometimes vomiting. A stiff neck often
follows. Rupture of an aneurysm usually occur while the
person is active rather than during sleep. Occasionally,
patients experience a warning or "sentinel" headache
which is attributed to a smaller leakage of blood usually
preceding a major bleed by several hours to days later.
These milder headaches are often associated with nausea
and vomiting and are often mistaken for migraine
headaches.
5. What kind of tests do I need to determine if I have
an aneurysm?
Carotid and vertebral angiography is the only
definitve means of demonstrating an intracerebral
aneurysm, while a CT scan of the head will confirm the
presence of blood within the brain or subarachnoid space
if an aneurysm has ruptured. Lumbar puncture is
sometimes used to evaluate for the presence of blood in
the cerebrospinal fluid if the results of the CT scan are
equivocal. More recently, non-invasive studies using
magnetic resonance imaging (MRI) and magnetic resonance
angiography (MRA) have shown promise in detection of
aneurysms. However, the intracerebral angiogram remains
the test of choice.
6. I have an intracerebral aneurysm. What is the risk
of death from rupture?
If rupture occurs, only approximately half of the
patients survive. The best predictor of risk of rupture
is the size of the aneurysm. Most aneurysms that rupture
have a diameter equal to or greater than 10mm (about
half an inch) but rupture also occurs with aneurysms of
smaller size. A guide to prognosis is provided by the
neurologic grade (Hunt and Hess Grades I-V) of the
patient determined by his/her level of consciousness and
neurologic deficits when first examined upon arrival to
the hospital. In a large study of survival of patients
from aneurysm rupture, a Grade of I-II (awake with slight
to moderately severe headache and neck stiffness)
predicted a low mortality (4%) and an independent life
(up to 90%) at follow-up whereas Grades IV-V (stupor with
neurological deficits to deep coma) predicted
increasingly higher mortality rates (up to 46%) and
decreased independent functioning (only about 30%).
7. What are the most serious complications associated
with aneurysmal rupture?
The developement of cerebral vasospasm,
rebleeding from the aneurysm, swelling of the ventricles
in the brain (hydrocephalus), and seizures may occur
after rupture of an intracerebral aneurysm. Cerebral
vasospasm after aneurysmal subarachnoid hemorrhage
usually occurd within the first 14 days of rupture and is
a major cause of morbidity and mortality in survivors of
the bleed. Its incidence has varied in different
studies between approximately 20 to 80% of all patients
with SAH and its occurence is related to the amount of
subarachnoid blood in the brain. Other complications
including rebleeding from an aneurysm and hydrocephalus
also contribute to the overall morbidity and mortality.
In addition, dangerous cardiac arrhythmias may develop in
the acute period following a bleed.
8. What are the risks of surgical repair?
The timing of surgery is now recognized as an
important factor in the prevention of complications
associated with aneurysmal rupture. Successful early
surgical clipping of a ruptured aneurysm (within the
first 5 days of a bleed) helps to prevent the occurence
of rebleeding, likely to be an even more catastrophic
event when it occurs, and permits the safe treatment of
cerebral ischemia due to vasospasm. High morbidity and
mortality may occur even in low-risk patients treated
with delayed operation because preoperative complications
have time to develop. However, such patients operated on
within the first 5 days of a bleed usually recover with
no or mild neurological deficit and mortality is less
than 5%.
9. What are my chances of recovery?
As stated above, patients in Grades I-III can be
operated on safely within 72 hours with good results. In
one study of 145 patients with Hunt & Hess Grades I-III,
81% (117 patients) made a good recovery. The morbidity
was 12% (17patients) and the mortality 7% (11 patients).
The most common cause of unfavorable outcome was surgical
complications. Other factors contributing to a worse
outcome correlated with a higher age, worse Grade, and
more severe SAH on CT scan.
10. What is the treatment for unruptured aneurysms?
The management of asymptomatic aneurysms
discovered incidentally remains controversial. A recent
study followed 142 patients with unruptured aneurysms for
a period of 14 years and found an average annual rupture
incidence of 1.4%. The cummulative rate of bleeding from
the aneurysms was 10% at 10 years, 26% at 20 years, and
32% at 30 years after the diagnosis. The surgical
clipping of an intact and accesible aneurysm is usually
a procedure of low risks without the future development
of postoperative ischemia or vasospasm, which are often
encountered with the clipping of ruptured aneurysms
(leading to risk of death or disability). Surgery is
usually recommended for large accessible aneurysms; but
with small ones (with a proportionally lower chance of
rupture) you should discuss the ratio of risk to benefit
with your physicians.
11. How can I get more information on this subject?
Your neurologist or neurosurgeon should be your
primary resource. A FAQ like this one is very general in
nature, and details about your own situation may result
in the possibility that the general guidelines do not
apply.
For additional reading, large bookstores carry
rather comprehensive reference works (like the one from
the Mayo clinic). If you have access to MedLine, you
can download abstracts from the primary medical literature.
You will find additional pointers on the Aneurysm
Information Project Home Page that will guide you to
other useful resources like the Aneurysm Victims' Support
Group.