In general, the decision rests on the size of the aneurysm, but uncertainty still exists. In one study, for example, the risk of rupture for aneurysms between 10 and 25 mm was quite low -- slightly less than 1% per year for both groups. Aneurysms over 25 mm, however, had a 6% chance of rupturing within a year. Studies have reported that in general, the risk for rupture is between .05 - 2% a year, but recent evidence suggests that the risks may be even less. In one study, even people with a history of subarachnoid hemorrhage had only a 0.5% annual risk for recurrence when aneurysms were small.
Aneurysms can often cause symptoms, however, even if they do not rupture. Patients should discuss their particular risk factors carefully with their doctors. Individuals with arteriovenous malformation, a condition caused by abnormal associations between arteries and veins, should be monitored for the development of aneurysm.
Clipping the Aneurysm. The standard surgical procedure for treating a ruptured aneurysm is to place a clip across the neck of the aneurysm, which blocks off bleeding. It is usually performed within the first three days. Getting to the aneurysm is often extremely difficult. Deep cooling of the body to stop circulation may be used to allow more time for the operation. Procedures that remove large portions of the bone in the skull are being developed to allow fast access. There is a relatively high risk for newly formed aneurysms, particularly after 9 years. Patients may want to discuss follow-up angiography to detect any new aneurysms 9 or 10 years after the procedure.
Transcatheter Embolization for Sealing off the Aneurysm. Transcatheter embolization is a new technique for ruptured and unruptured aneurysms that is proving to be effective, although it is still investigative. The surgeon threads a thin tube through the artery leading to the aneurysm through which materials are passed to plug or obstruct the aneurysm. In one version of this procedure, the following occurs:
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