Arteriovenous Malformations

What is a brain AVM?

A brain arteriovenous malformation (AVM) is an abnormal tangle of blood vessels that connects arteries and veins in the brain, bypassing the normal capillary system. Blood is shunted at high pressure from arteries directly into veins, which can weaken vessel walls over time.

AVMs are usually congenital (present from birth) and are found in approximately 0.1% of the population. They can occur anywhere in the brain or spine but are most commonly found in the cerebral hemispheres.

Symptoms

Many AVMs are found incidentally on brain imaging. When symptoms do occur, they may include:

• Haemorrhage (bleeding) — the most serious presentation, occurring in approximately 2–4% of cases per year
• Seizures — a common presentation, particularly for unruptured AVMs
• Headaches
• Focal neurological deficits — weakness, visual disturbance, or speech difficulties
• Pulsatile tinnitus

Treatment options

Treatment of AVMs is complex and requires careful multidisciplinary discussion. Options include:

• Observation — for incidentally found, asymptomatic, low-grade AVMs
• Endovascular embolisation — catheter-based injection of embolic agents to reduce blood flow, often used in combination with other treatments
• Neurosurgical resection — surgical removal, particularly for superficial, accessible AVMs
• Stereotactic radiosurgery — focused radiation to obliterate the AVM, effective for smaller lesions
• Combined (multimodal) treatment — the most common approach for complex AVMs

Grading

AVMs are graded using the Spetzler-Martin scale (I–V), which considers size, location (eloquent vs non-eloquent cortex), and venous drainage pattern. Higher grades carry greater treatment risk, and management is tailored accordingly.

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