Definition
A brain aneurysm is the bulging of a blood vessel that supplies parts of the brain with blood. Aneurysms are usually congenital and remain unnoticed until they become so large that they press on surrounding tissue or until they tear and lead to life-threatening bleeding. In addition, they can be caused by increased blood pressure during the course of life.
The bulging of a blood vessel in the brain is actually not serious, but the danger is that the wall of the vessel becomes thinner at the same time. At some point, the thinner wall can no longer withstand the pressure of the blood and tears, which too often leads to life-threatening cerebral haemorrhages that can result in a stroke. While the majority of strokes are caused by vascular occlusions, about 10-15% are due to cerebral hemorrhages. Among the cerebral hemorrhages, the aneurysm is one of the most important causes. Since brain aneurysms usually do not cause any symptoms before they rupture, they go unnoticed for a long time and are often diagnosed as random findings.
Frequency
Since an aneurysm can go unnoticed for a long time and is often not diagnosed at all, the study situation regarding the frequency of its occurrence is very vague. In addition, the frequency is also influenced by factors such as age and genetic disposition as well as risk factors such as high blood pressure or smoking. Studies on patients who received vascular imaging of the brain for various reasons showed that about 1-2% of these patients had a brain aneurysm. Studies on autopsied cadavers showed that the frequency is much higher. Thus, 7-10% of the examined cadavers had an aneurysm of one or more vessels of the brain.
Causes of a cerebral artery aneurysm
There are many known causes of aneurysm formation and probably many unknown causes as well. The basic prerequisite for the formation of this life-threatening aneurysm is genetic predisposition. Like other connective tissue weaknesses that are inherited, instabilities of the vessel wall can also be passed on from generation to generation.
However, not everyone with this predisposition will eventually have an aneurysm. Important factors influencing the formation are smoking, high blood pressure and also the influence of various hormones. If an aneurysm has formed, however, blood pressure is a major factor in the further development of the aneurysm.
As the vessel wall sags, it also becomes thinner at the site and can no longer tolerate the pressure built up by the bloodstream as well as a normally thick vessel wall. If the blood pressure is also elevated, the sacculation may progress and the vessel wall may become even thinner. At some point, the wall can no longer withstand the pressure and tears. The so-called rupture of the aneurysm is a life-threatening emergency, as it leads to heavy bleeding into the brain.
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