Brain Arteriovenous Malformation (AVM)

Brain AVMs are usually present from birth. They develop before birth, while the blood vessels in the brain are forming, due to an abnormal connection between arteries and veins. In most people, they occur by chance and are not inherited, caused by lifestyle or injury. In a small number of cases, AVMs can be linked to a genetic condition called hereditary haemorrhagic telangiectasia (HHT), where multiple abnormal blood vessels may be present in the body.

Haemorrhage

Bleeding from a brain AVM is the most serious and dangerous presentation. It can cause a sudden, severe headache, loss of consciousness, weakness, difficulty speaking, or seizures. Symptoms depend on where the bleeding occurs in the brain. This is a medical emergency and requires immediate attention.

Seizures

Seizures are a common presenting symptom, especially in AVMs that have not bled. They may affect one part of the body (focal seizures) or the whole body (generalised seizures).

Headache

Headache, sometimes migraine-like, can be associated with brain AVMs, However, headaches are common in the general population and are not always caused by an AVM.

Progressive Neurological Deficit

In some rare cases, a brain AVM can cause slowly worsening symptoms, such as weakness, numbness, or problems with speech or vision. This may happen because the AVM alters normal blood flow in the brain.

Incidental Discovery

Some AVMs are found by chance during brain scans done for unrelated reasons. These are called incidental findings.

Urgent Symptoms

If an AVM ruptures, symptoms usually come on suddenly. These may include a severe headache, rapid worsening of neurological symptoms, or loss of consciousness. This is a medical emergency. Call 000 immediately.

Doctors use several imaging tests to diagnose a brain AVMs, assess the risk of bleeding and help plan the best treatment:

• CT angiography (CTA) – a commonly used scan that is quick, widely available, and effective at showing the presence of an AVM. It involves an injection of contrast dye into a vein.
• MRI (magnetic resonance imaging) – is a non-invasive scan that provides detailed images of the AVM, including the nidus, any associated bleeding, and its relationship to surrounding brain structures. 
• Cerebral angiography (also called digital subtraction angiography or DSA) – a more detailed test. It involves guiding a thin tube (catheter) through the blood vessels and injecting contrast dye. This test provides important information about the feeding arteries, size and location of the nidus, draining veins, and any associated aneurysms. 

Brain AVMs are often graded using the Spetzler-Martin scale (grades 1 to 5). This grading system is based on the size of the AVM, its location in the brain, and the pattern of venous drainage. It helps estimate the risks of surgery and guide treatment decisions, rather than predicting the risk of bleeding.

Treatment decisions are tailored to each individual and depend on factors such as the AVM grade, location, history of bleeding, age, and symptoms. For unruptured AVMs, the balance between bleeding risk and treatment risk must be carefully weighed. At One Brain and Spine, treatment decisions are made by a multidisciplinary team, which may include a neurosurgeon, a neurointerventional specialist, and a radiation oncologist.

Observation

In some cases, especially for large AVMs that are not causing symptoms, monitoring with regular scans may be recommended. This approach may be considered when the risks of treatment are higher than the risk of bleeding. 

Microsurgical Resection

Surgical removal of the AVM can provide a complete and immediate cure. It is most suitable for smaller AVMs in accessible areas of the brain. In some cases, surgery is also performed after bleeding to remove both the clot and the AVM. At One Brain and Spine, our cerebrovascular neurosurgeons perform AVM resection using the latest technologies including intraoperative navigation, neuromonitoring, and intraoperative angiography.

Endovascular Embolisation

This is a minimally invasive procedure where a thin tube is guided through the blood vessels to the AVM. Special materials are injected to block abnormal blood flow. It may be performed before surgery or radiosurgery to make treatment safe rather than as definitive treatment alone.

Stereotactic Radiosurgery (SRS)

Radiosurgery uses focused radiation to gradually close off the AVM over time, usually 2 to 3 years. It is most suitable for small AVMs in deeper or more sensitive areas of the brain. There remains a risk of bleeding until the AVM is fully treated.