Aneurysm is a balloon-shaped expansion abnormality that occurs at the bifurcation points of the vessels. The wall of this formation is weaker than normal and cannot withstand the pressure, which may crack and cause brain hemorrhage. On the other hand, Arteriovenous Malformation (AVM) refers to the situation where, due to lack of development in the capillary system, the arteries carrying clean blood establish a connection between the abnormally enlarged vascular bundle and the venous system. Blood passing through the capillary system encounters resistance and slows down its flow, which may cause inadequate nutrition of the surrounding tissue and epileptic seizures.

The similarity between AVM and aneurysm is that both can cause brain hemorrhage. However, there are some fundamental differences between these situations. Due to the deficiency in the vascular wall layers, AVM vessels can bleed above a certain pressure. On the other hand, while the aneurysm shows the characteristics of the vascular wall, although it is weaker than normal, it usually ruptures when a certain pressure threshold is exceeded.

Aneurysm is more common than AVM. For example, in our patient series (2800 aneurysms, around 450 AVM cases were treated with surgery), we observed that aneurysms were encountered approximately six times more frequently than AVMs. Both conditions can lead to similar outcomes with a risk of brain hemorrhage, but they differ in their diagnostic and treatment processes.

Aneurysm and Arteriovenous Malformation (AVM): Diagnosis, Treatment and Prevention

What are Aneurysm and AVM?

Aneurysm is a bubble-shaped structural defect that occurs at the bifurcation points of the vessels. Arteriovenous Malformation (AVM) refers to an abnormal vascular bundle in which the artery directly connects with the vein, as a result of the incomplete development of the capillary system that should be between the artery and the vein. Both involve vascular wall defects that occur due to congenital causes.

In Whom Is It Seen?

Aneurysms and AVMs are generally more common in young men and women. According to autopsy results, aneurysms in the brain vessels are detected at a rate of approximately 10-14%. However, it should not be forgotten that these aneurysms do not bleed throughout their lives. The incidence of aneurysm in children of individuals with a family history of aneurysm is higher than in others. The frequency of aneurysms is also associated with some diseases such as polycystic kidney and aortic stenosis. AVM is less common than aneurysm, but has a higher risk of bleeding.

How is it formed?

Aneurysm develops due to the absence of muscle-like structures and strong vessel walls at the bifurcation points of the brain vessels. Factors such as pressure within the vein, smoking, and arteriosclerosis may cause bubble formation at weak points. Congenital factors are more effective in the development of AVM. Instead of the capillary system, an abnormal vascular bundle emerges, where the artery and vein directly connect.

What are the symptoms?

When thin-walled aneurysms and AVMs cannot withstand the blood pressure inside, they may rupture and cause bleeding. Aneurysm usually shows symptoms by bleeding under the cerebrospinal fluid membrane. An AVM may rupture the brain tissue by bleeding and cause increased intracranial pressure due to a blood clot.

Treatment Methods and Prevention

Treatment varies depending on the condition of the aneurysm and AVM. Suitable aneurysms and AVMs are corrected with microsurgery so that blood does not enter. The aneurysm neck is closed with tiny tongs called clips. Alternative treatments for cases that are not suitable for surgery include stuffing with a ball of wire similar to steel wool and burning with gamma rays (Gamma Knife).

If left untreated, aneurysm and AVM can cause brain bleeding. Aneurysm treatment is usually done early and prevents rebleeding. It is recommended that smokers quit and blood pressure patients receive regular treatment. It is important that those with a family history of aneurysms have regular brain MRI angiography, and follow-up of small aneurysms should not be neglected.