Published on Oct 10, 2022 and last reviewed on Oct 14, 2022 - 4 min read
Arteriovenous malformation (AVM) is a tangle of abnormally connected blood vessels. Inside the brain, an AVM poses a risk of spontaneous rupture and bleeding.
Arteriovenous malformations or AVM, is a tangled cluster of arteries and veins (the two types of blood vessels). In almost all cases, it forms during the development of a child inside the uterus. An arteriovenous malformation may develop in any part of the body, including the brain. And there is a risk of rupture producing severe bleeding (hemorrhage). Now, this blood may raise the pressure inside the brain or obstruct normal blood flow, causing stroke or brain damage. With timely medical help, one can get rid of an arteriovenous malformation and avoid the above risks.
It basically involves two different kinds of blood vessels that should not be directly connected but get connected due to some developmental error. In the body, there are arteries which are the vessels that carry the blood from the heart to the rest of the body. Arteries are thick-walled and are designed to carry high-flow and high-pressure blood. Once the blood reaches wherever it is going in the body, the arteries split again and again until, ultimately, they form capillaries. These are tiny microscopic vessels that supply oxygen to all tissues of the body. After the oxygenation has taken place, it’s the veins that take the blood back to the heart from the brain. Veins are very thin-walled and are designed to carry low-pressure slow-flow blood. Hence, the arteries and veins are quite different in the way they are built, and ideally, they should not have direct communication between them.
In an arteriovenous malformation, the arteries and veins are directly connected by a tiny network of very small vessels during the development. This makes the high-pressure blood go straight from the arteries into the vein. There is built-up stress inside the vessels to the point where the weakest part of it ruptures and causes bleeding eventually. Individuals with a family history of arteriovenous malformation and those of the male gender are at a higher risk for this. If the arteriovenous malformation occurs at a very young age and it is of a very high flow, it can cause other troubles such as heart failure.
In the majority of individuals, arteriovenous malformations stay symptom-free until they rupture to cause a bleed. A few of them show the following symptoms:
Pain in the area of the head where an arteriovenous malformation is present.
Numbness, muscle weakness, or paralysis in one part of the body.
Loss of body balance.
Issues with speech or eyesight.
Mental confusion and inability to comprehend things.
In severe arteriovenous malformations involving major blood vessels of the brain, the fluid build-up makes the brain swell up and turn fatal.
Potentially life-threatening bleeding inside the brain is the most dangerous complication. The risk of hemorrhage varies depending on the area of the brain and the size of the arteries involved. A ruptured arteriovenous malformation can be one of the reasons leading to aneurysms (weakening and ballooning up of a blood vessel) and stroke. The large volume of leaked blood and the inflammatory fluid produced in response to bleeding fill up the spaces inside the brain and causes hydrocephalus (enlarged brain with fluid collection). It tends to compress the structures inside the brain against the walls of the skull and cause damage. Apart from that, it may deprive the other parts of the brain of getting adequate oxygen leading to tissue death.
Bleeding from a ruptured arteriovenous malformation is a medical emergency. The affected individual requires urgent medical attention and a quick diagnosis. The doctor reviews the symptoms and medical history along with a physical examination. The following tests are conducted to confirm the diagnosis:
Imaging studies like computed tomography (CT) or magnetic resonance imaging (MRI) to identify the exact location of the bleeding and possible damage to the brain.
Cerebral angiography, where a long thin tube is inserted into an artery in the groin and guided up into the brain. A dye is injected into the artery, and with the help of an x-ray, one can visualize the site of arteriovenous malformation.
The goal of treatment is to try to reduce the risk of bleeding and make it go away altogether. One may attempt the following strategies:
Surgical Removal - The doctor might suggest surgery if one has a high risk of bleeding. One can just remove the arteriovenous malformation surgically so that the risk of bleeding is eliminated. It involves the complete removal of the lesion. However, surgery will be feasible only if the arteriovenous malformation lies in an area that poses minimal risk of damaging the brain tissue.
Stereotactic Radiosurgery - Where radiation is used on the blood vessels till they begin to thicken up and begin to close off so that the arteriovenous malformation shrivels up. Eventually, it disappears over some time.
Endovascular Embolization - Where a very tiny wire is threaded up to the blood vessels inside the body, and one squirts different substances that can plug up the vessels from the inside. This may help to slow down or stop the flow of blood inside an arteriovenous malformation.
Review and Monitoring - Even after completing the treatment, one needs regular follow-ups with the doctor to check for recurrence. This includes periodic imaging studies and more.
Sometimes, the safest thing to do in a very big arteriovenous malformation or one that is located in a very sensitive part of the brain is to just monitor it. Because the risk of treating the arteriovenous malformation might have more side effects and be more dangerous than leaving it alone, the doctor may recommend regular check-ups and imaging studies to assess the progress. With modern advancements improving surgical precision, removing arteriovenous malformations are more successful than before. Early medical intervention gives the best results in such a condition.
AVMs can be managed or cured by microsurgical resection, endovascular embolization, stereotactic radiosurgery, or sclerotherapy. Small AVM treatment with surgery has a cent percent success rate with less than 15 % complications, and radiosurgery has a success rate of 70 % and complication rates of less than 10 %.
AVMs are serious medical conditions that remain fairly asymptomatic until a bleeding event exposes their occurrence, primarily in the brain or spinal cord. Unmanaged bleeding can cause serious neurological damage and even prove fatal.
AVM affects around 1 in 2000 individuals and remains asymptomatic. People can live relatively normal lives, albeit with a risk of spontaneous bleeding within the brain and causing a stroke. With the advancements in treatment modalities, life expectancies have rocketed significantly.
AVMs are vascular deformities. Hence, anything that can cause vascular changes should be avoided, like
- Strenuous activities (may raise blood pressure).
- Heavy lifting.
- Taking blood thinner medications (like Warfarin).
- Avoid alcohol intake.
- Avoid nicotine-containing products and illegal drugs.
Microsurgical resection is considered the gold standard for AVM treatment. Small AVMs (up to 3 cm) can be completely resected in more than 94 % of the cases, with a good prognosis in more than 90 % of surgeries. According to a study, surgical resections of small AVMs are up to 100 % successful with less than 15 % complication.
AVMs, directly, are not inherited, but a familial history may increase the risk of developing AVMs. Certain heritable diseases like hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome), an autosomal dominant disorder, can increase the risk of vascular malformation.
AVMs hide asymptomatically until a bleeding event exposes them. A burst AVM is an emergent medical situation as a burst lesion causes severe hemorrhage (bleeding) in the brain or spinal cord, stroke, and brain damage which can progress to coma or death.
Surgical resection is the gold standard of AVM repair, where the surgeon clips the vascular malformation using high-powered microscopic vision and carefully removes it from the brain. Another surgical procedure, endovascular embolization, uses a catheter inserted into the leg or wrist artery and threaded to the AVM location, where an embolizing agent is injected to block the feeding artery to the AVM. Precisely focused radiation may also be implemented to destroy the AVM (stereotactic radiosurgery).
Dormant, benign AVMs do not cause any personality or behavioral changes. However, a diagnosis of such a paramount can cause emotional duress in the individual. About 1 in 5 patients may experience depression. Additionally, a bleeding AVM can cause brain injury leading to emotional and mood changes.
AVMs are not included in the disabilities by the social security administration. However, complications arising from a ruptured AVM can induce changes that may qualify the individual for benefits but under a different disability.
AVMs develop within the brain and spinal cord, and any rupture from the malformation causes intracranial hemorrhage, which can cause damage to the brain. AVM ruptures can cause a stroke leading to paralysis, coma, or even death.
It is possible to survive an AVM rupture only with immediate medical attention via open cranial surgery. The probability of neurological deficit after a rupture is about 20 % and about 35 % for complete recovery.
AVMs are not tumors but rather vascular developmental defects. AVMs are a tangle of blood vessels that reduces blood flow to a part of the brain. However, some hypervascularized tumors may be misdiagnosed initially as AVMs.
AVMs are congenital vascular developmental defects (an entanglement of blood vessels) that reduce blood flow to a brain portion and may rupture, causing cranial hemorrhage and subsequent complications. Aneurysms, on the other hand, is a segment in the blood vessel that has thinned out and ballooned, which may keep enlarging with a tendency to spontaneously rupture.
Angiographic studies have confirmed that AVM resection does not completely rule out the possibility of bleeding. AVMs have been known to regrow, especially in children, which is attributed to forces rooting for vasculature changes.
Last reviewed at:
14 Oct 2022 - 4 min read
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