A connection that shouldn't happen directly: cerebral vascular malformation

Author: Wang Shuo, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

Chairman of the Neurosurgery Branch of the Chinese Medical Association

Reviewer: Wang Jiawei, Chief Physician, Beijing Tongren Hospital, Capital Medical University

Cerebrovascular malformation is a disease in which the cerebral blood vessels develop abnormally. The incidence rate is very low, about 1.1/100,000 to 1.2/100,000, and it is a rare disease. Cerebrovascular malformation can be divided into four categories. The relatively common one is arteriovenous malformation. Here we mainly talk about arteriovenous malformation.

Under normal circumstances, there are arteries and veins in the brain, which are connected by capillary beds, just like water pipes and sewers, and do not communicate directly. However, when cerebrovascular malformations occur, arteries and veins are directly connected, and arterial blood directly enters the veins, causing a series of hemodynamic changes and symptoms.

1. What is the cause of cerebral vascular malformation?

The cause of cerebral vascular malformations is still unclear. It is currently believed that during embryonic development, there may be some conduction pathway disorders during the vascular development period, causing abnormal development of arteries and veins, resulting in direct communication between arteries and veins. With age, vascular malformations can also increase.

Approximately 64% of patients with cerebrovascular malformations will develop the disease before the age of 40. The peak period of onset is young and middle-aged age, with a higher incidence rate among adolescents aged 15-25 years old.

2. What are the symptoms of cerebral vascular malformations?

Under normal circumstances, arterial blood should first reach the capillary bed, which is a decompression bed. During this process, the blood pressure gradually decreases, while releasing the oxygen and nutrients it carries. After the decompression is completed, the blood will then go to the veins.

When cerebral vascular malformation occurs, due to the lack of capillary bed and "decompression bed", arteries and veins communicate directly, and high-pressure arterial blood directly enters the veins, which may cause venous rupture and bleeding.

Therefore, one of the most common symptoms of cerebral vascular malformation is cerebral hemorrhage. About half of the patients will suffer from bleeding due to ruptured venous blood vessels, and the mortality rate of each cerebral hemorrhage is 10%-15%. The symptoms of cerebral hemorrhage are related to the location and amount of bleeding. If the bleeding occurs in the functional area, it will cause corresponding functional insufficiency; if the amount of bleeding is small, the patient may have no symptoms, but the vast majority of patients with cerebral hemorrhage will have headaches. When the amount of bleeding is large, the headache will be very severe, which may lead to coma or even brain herniation, directly endangering the patient's life.

Figure 1 Original copyright image, no permission to reprint

The second symptom of cerebrovascular malformation is epilepsy, commonly known as convulsions or epilepsy. The incidence rate is 40%-60%, manifested as sudden convulsions of the limbs or the whole body, which may be accompanied by unconsciousness and generally last for a short time. The cause may be related to bleeding or blood stealing from vascular malformations. Under normal circumstances, after arterial blood reaches brain cells and releases oxygen and other nutrients, it will flow back to the heart from the veins and then flow to the lungs to absorb oxygen again. In the case of cerebrovascular malformations, arterial blood flows directly into the veins without the process of releasing oxygen, causing ischemia and hypoxia in the surrounding brain tissue, leading to brain cell atrophy and decreased function. At this time, some material changes may occur, causing epilepsy. In addition, bleeding from cerebrovascular malformations can cause yellowing of the surrounding brain tissue, which can also cause epilepsy.

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The third symptom of cerebrovascular malformation is progressive dysfunction, which is also related to blood stealing. Similarly, arterial blood does not release oxygen to brain cells, but flows directly from the veins, causing ischemia and hypoxia in the surrounding brain tissue, especially in the functional area. Long-term ischemia and hypoxia cause progressive dysfunction, which can cause patients to gradually become numb and weak in their limbs; language disorders, such as speaking more and more slowly or not being able to express their ideas; visual field defects and other functional disorders.

The fourth symptom of cerebral vascular malformation is headache. There are no sensory nerves in the brain tissue, so you cannot feel pain. The only part that can actually feel pain is the dura mater where sensory nerves are distributed. Headache may be caused by blood stealing or dilated blood vessels irritating the dura mater.

Figure 3 Original copyright image, no permission to reprint

In addition, some patients may experience intracranial murmurs, and in the dead of night, they can hear a whirring, heart-beating murmur in their brains. Some patients may also experience protruding eyeballs, but this is relatively rare.

Generally speaking, the symptoms of cerebrovascular malformations are mainly cerebral hemorrhage, epilepsy, progressive dysfunction and headache.

3. What tests can be done to detect cerebral vascular malformations?

At present, many examinations can detect vascular malformations, such as CT, MRI, angiography, etc., which can clearly diagnose.

Routine non-invasive examinations, such as magnetic resonance imaging, can basically show arteriovenous malformations and some special signals, such as flow voids caused by rapid blood flow, but smaller malformations may be difficult to detect.

The most basic diagnosis is cerebral angiography. An artery is punctured at the wrist or thigh root, a catheter is inserted into the blood vessel and sent to the corresponding position. After contrast agent is injected, the morphology of the blood vessel is observed to confirm whether there is a vascular malformation.

4. Are cerebral vascular malformations dangerous?

Cerebrovascular malformations generally do not cause great harm unless there is cerebral hemorrhage or epilepsy. However, some larger malformations or malformations prone to bleeding may cause progressive dysfunction near the functional area.

Once cerebral hemorrhage occurs due to cerebrovascular malformation, serious harm may occur. As mentioned earlier, patients with cerebral vascular malformation who suffer cerebral hemorrhage have a mortality rate of approximately 10%-15% and a disability rate of 30%-50%. The closer the bleeding site is to the functional area, the more bleeding there is, and the higher the disability rate.

According to literature reports, only 50% of patients with cerebrovascular malformations may suffer from cerebral hemorrhage. Therefore, surgical intervention is not necessary as soon as a cerebrovascular malformation is discovered. Instead, a pre-treatment assessment is required based on the patient's age, medical history, symptoms, characteristics of the lesion (location, size, structure, and whether there are risk factors for bleeding, such as aneurysms), and patient demands. For cerebrovascular malformations that are prone to bleeding, clinical intervention is generally more active to prevent the occurrence of complications.