Arteriovenous Malformations: Causes, Symptoms, Diagnosis, and Treatment

An irregular blood vessel network connecting arteries and veins known as an arteriovenous malformation (AVM) impairs normal blood flow and oxygen delivery.

The brain receives oxygen-rich blood from the heart through arteries. The oxygen-depleted blood is returned to the heart and lungs through veins.

The surrounding tissues may not receive adequate oxygen when an AVM interferes with this crucial process. Additionally, the abnormally twisted blood arteries that make up the AVM are prone to deterioration and rupture. If the AVM ruptures in the brain, it may result in brain bleeding (haemorrhage), a stroke, or permanent brain damage.

AVMs have an unknown cause. They don't often get passed down via families.

Brain AVM: Causes

AVM in the brain has no known etiology. The majority of brain AVMs, according to researchers, are present before birth and develop throughout fetal development, but they can also emerge later in life. Some persons with hereditary hemorrhagic telangiectasia (HHT), commonly known as Osler-Weber-Rendu syndrome, experience brain AVMs. The formation of blood vessels throughout the body, including the brain, is impacted by HHT.

Normally, the heart uses arteries to deliver oxygen-rich blood to the brain. The arteries reduce blood flow by routing it via a series of networks of blood vessels that get smaller and smaller until they reach the smallest blood vessels (capillaries). Through their flimsy, porous walls, the capillaries gradually provide the surrounding brain tissue with oxygen.

The blood that needs more oxygen travels through smaller blood vessels before entering larger veins, which carry it back to the heart and lungs.

An AVM's arteries and veins lack this supportive system of capillaries and smaller blood vessels. Instead, blood bypasses the surrounding tissues and travels swiftly and straight from the arteries to the veins.

Brain AVM: Symptoms

The location of an AVM affects the symptoms it causes. Frequently, after bleeding has started, the first symptoms and indications show up. Signs and symptoms other than bleeding include −

• Decrease of neurological function over time

• Headaches

• nausea and diarrhea

• Seizures

• Consciousness loss

• Additional warning signs and symptoms could be −

• Skeletally frail

• Having a body part paralyzed

• Loss of coordination that may lead to gait issues

• Difficulties completing things that demand planning

• Weakening of the lower body parts

• Backache

• Dizziness

• Visual issues such as losing some of your field of vision, having trouble controlling your eye motions, or having an optic nerve edema

• Issues with language comprehension or speech

• Unusual feelings including tingling, numbness, or sharp pain

• Alzheimer's or memory loss

• Hallucinations

• Confusion

There may be issues with learning or conduct in kids and teenagers.

Symptoms of one type of AVM known as a vein of Galen defect start to show up at or soon after birth. There is a vein of Galen defects deep into the brain. An example of a sign is −

• A fluid build-up in the brain called hydrocephalus that results in an enlarged head

• Scalp veins that are enlarged

• Seizures

• Failing to flourish

• Enlarged heart disease

Brain AVM: Risk Factors

A family history of AVMs can incredibly rarely raise your risk. However, the majority of AVM types are not hereditary.

Your risk of AVM may be increased by some inherited disorders. These include Osler-Weber-Rendu syndrome and hereditary hemorrhagic telangiectasia (HHT).

Brain AVM: Diagnosis

Your doctor will analyze your symptoms and do a physical exam to determine whether you have an AVM.

He or she might keep an ear out for a bruit. Blood flowing through an AVM's arteries and veins at an extremely high rate produces a whooshing sound known as a bruit. It has the sound of water gushing through a little pipe. Bruit may disrupt sleep, cause emotional anguish, or interfere with hearing.

AVM is frequently diagnosed using the following procedures −

• Brain angiography − This procedure, which is also known as arteriography, involves injecting a contrast agent, a particular dye, into an artery. To make blood vessels easier to see on X-rays, the dye enhances their structural details.

• Computer-aided imaging (CT) − CT scans, which make images of the head, brain, or spinal cord using X-rays, can assist identify bleeding.

• Imaging with magnetic resonance (MRI) − An MRI produces precise images of the tissues using strong magnets and radio waves. These tissues can undergo minute alterations that an MRI can detect.

• Angiograms using magnetic resonance (MRA) − The pattern, speed, and distance of blood flow through vascular anomalies are all captured by an MRA.

Brain AVM: Treatment

AVM treatment is based on the location of the abnormality, your symptoms, general health, and the danger of the procedure. An AVM may be periodically imaged in order to check for changes or issues. Other AVMs need to be treated. If an AVM requires therapy, it must be determined, among other things, whether the AVM −

• is a bleed

• causes symptoms besides bleeding

• at a region of the brain where treatment can be administered without risk

Medication can help with symptoms like back pain, headaches, and seizures.

Surgery is the major AVM treatment. If you have a high risk of bleeding, your doctor might advise surgery. The AVM might be entirely removed through surgery. When the AVM is in a location where it can be surgically removed without significantly damaging the brain structures, this treatment is typically employed.

In an operation known as endovascular embolization, the AVM is reached by the surgeon threading a catheter through the arteries. The AVM is then partially closed with a chemical to limit blood flow. Additionally, this could be carried out prior to radiosurgery or brain surgery to assist lower the chance of problems.

Brain AVM: Complications

The walls of the arteries and veins that are damaged by an AVM are subjected to intense pressure, which makes them thin or weak. The AVM could rupture as a result, causing brain bleeding.

• A brain AVM bleeding risk of 2% to 3% per year is present. If an AVM has already ruptured or if it is one of the particular forms, there may be an increased risk of bleeding.

• Because they don't result in significant brain damage or other outward indications or symptoms, some haemorrhages connected to AVMs go unnoticed. However, bleeding episodes that could be fatal could happen.

• About 2% of all hemorrhagic strokes each year are caused by brain AVMs. They are frequently the source of brain bleeding in children and young adults.

• Less oxygen reaches brain tissue. Blood bypasses the capillary network in the brain when there is an AVM, instead traveling straight from arteries to veins. Because the altered course is devoid of channels of smaller blood arteries, blood flows fast across it.

The oxygen in the swiftly moving blood cannot be readily absorbed by the brain tissue nearby. Brain tissues may get fully depleted of oxygen or at least become weaker. This causes symptoms resembling a stroke, such as speech difficulties, numbness, weakness, vision loss, or extreme unsteadiness.

Conclusion

AVM cannot be prevented but avoiding the risk factors and timely diagnoses will help in preventing the complication.