This neurological condition can put the patient’s life at risk.
When an area of the wall of a blood vessel weakens, a so-called cerebral aneurysm appears , a kind of sac that can rupture and cause a cerebral hemorrhage.
In this article we will learn about the different types of cerebral aneurysms, according to three classification criteria: their morphology, their etiology and their size. In addition, we will know where they occur most frequently and what are the risk factors associated with them.
- Recommended article: “Cerebrovascular accident (stroke): types, causes, symptoms and treatment”
Brain aneurysms: what are they?
Brain aneurysms, also called intracranial aneurysms, are specific areas of the walls of blood vessels or arteries, which are weak and cause a kind of sac or balloon to protrude (that is, the walls dilate causing this widening).
That balloon fills with blood and can press on a surrounding nerve or brain tissue. If the sac becomes very full and exerts a lot of pressure, it can break and bleed into the surrounding tissue . This phenomenon is called hemorrhage.
However, it can happen that the aneurysms are so small that they do not bleed or cause problems, as we will see later.
Where do they occur?
Brain aneurysms can appear in any part of the brain. However, most of them appear at the base of the brain ; this area is also called the circle of Willis or the polygon of Willis .
In the circle of Willis there are different areas where the different types of brain aneurysms usually occur. The vast majority (85% of cases) affect the internal carotid artery in that area, also affecting its intracranial branches.
Risk factor’s
There are a number of risk factors that have been related to the appearance of different types of brain aneurysms. These mainly include hypertension (high blood pressure), alcoholism, smoking, substance abuse (especially cocaine), use of contraceptives, and use of anticoagulants.
On the other hand, being older also means a higher risk of developing a brain aneurysm (and a higher risk of unsuccessful surgery, especially after the age of 50). In addition, the fact of presenting a family history of cerebral aneurysm (especially in first-degree relatives) also implies a greater probability of developing one of them.
Higher risk of rupture
Regarding the risk that a brain aneurysm will end up rupturing, a study carried out by the Mayo Clinic (United States) found that its location influences the probability of rupturing or not.
Thus, they found that aneurysms located in the back of the brain have a higher risk of rupturing , compared to those located in the front. On the other hand, having a previous history of aneurysm rupture also increases the probability that one of them will rupture again.
The same study also concluded that when the risk of rupture is very low, it is better not to treat or operate on the aneurysm.
Types of brain aneurysms
There are different types of brain aneurysms , depending on different criteria that we use to classify them.
We will base ourselves on three classification criteria: morphology, etiology and size.
1. According to its morphology
Depending on their shape, we find three types of cerebral aneurysms: the saccular (involves the majority of cases), the dissecting and the fusiform.
1.1. saccular aneurysm
The first of the types of cerebral aneurysms, the saccular aneurysm, is also known as a “berry” aneurysm, and constitutes between 66 and 98% of cerebral aneurysms. Most of these aneurysms are not congenital, that is, they are acquired. They appear especially in people suffering from syphilis, a sexually transmitted disease.
Saccular aneurysm consists of a round bag-shaped blood sac , which is attached at the neck to an artery or branch of a blood vessel. Most saccular aneurysms occur in adults and are located at the base of the brain; On the other hand, most of these types of cerebral aneurysms have their origin in arterial bifurcations.
1.2. dissecting aneurysm
The second type of aneurysm, the dissecting aneurysm, generally appears in the vertebro-basilar system. The vertebrobasilar system includes a group of intracranial arteries that supply three areas of the brain: the hindbrain, the cerebellum, and the brainstem. It is the only system where two different arteries merge continuing into a single artery.
Dissecting brain aneurysms appear more in men than in women. Dissecting aneurysms are usually caused by a blow (or injury) to the head .
1.3. fusiform aneurysm
This type of aneurysm forms through the widening (dilation) of all the walls of the blood vessel (that is, the dilation forms on both sides of the artery). This dilatation has an elongated and tortuous shape; its diameter and length may vary. Thus, they are dilated and tortuous arterial segments.
In fusiform aneurysms there is no defined neck, and the paths it covers are long. Finally, these types of cerebral aneurysms are located especially in the posterior blood circulation.
2. According to its etiology
Depending on the cause, we also find different types of brain aneurysms . Most of them are acquired, and appear as a result of an abnormality or weakness (which is usually innate, yes), in the wall of the arteries. This weakness may or may not lead to aneurysms. However, there are also congenital aneurysms (which appear from birth).
On the other hand, it is true that there are people with genetic abnormalities who end up developing aneurysms; These alterations can be arteriovenous malformations (typical of circulatory disorders), a disease that causes polycystic kidneys or a collagen disease (a component of the skin and bones), among others.
Thus, there are various causes that cause aneurysms, which involve the development of different types of them; however, the most common is vascular injury (vascular trauma), followed by atherosclerosis (accumulation of substances on the walls of the arteries), vasculopathy (blood vessel disorder), and high blood flow.
Other possible causes are infections (they are called mycotic aneurysms, considered rare), traumas, neoplasms (abnormal and uncontrolled mass of tissue) and abuse of addictive substances.
3. According to your size
Depending on the size, we find, broadly speaking, three types of brain aneurysms: small, large and giant .
Small brain aneurysms are usually less than 11 millimeters in diameter; the large ones are between 11 and 25 millimeters in diameter, and the largest aneurysms of all, those considered giant, can be larger than 25 millimeters in diameter. This last type of aneurysms affect more than one artery.
Bibliographic references
- Cantú-Brito, C., Ruiz-Sandoval, J., Chiquete, E., Arauz, A., León-Jiménez, C., Murillo-Bonilla, L., Villarreal-Careaga, J., Barinagarrementería, F., et. to the. (2011). Risk factors, causes and prognosis of the types of cerebrovascular disease in Mexico: Renamevasc Study. Mexican Journal of Neurosciences, 12(5): 224-234.
- Kelly, M. (2007). Stent Reconstruction of Wide-Necked Aneurysms across the circle of Willis. Neurosurgery 61 [ONS Suppl 2].
- National Institute of Neurological Disorders and Stroke (NIH). (2016). Brain aneurysms.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.
