What is an arteriovenous malformation (AVM)?

An AVM is an abnormal tangle of vessels (the nidus) where arteries connect directly to veins without a capillary network. This creates a high-flow shunt that can contribute to venous dilation and risk of rupture/bleeding.

When is treatment needed?

Treatment is individualized based on hemorrhage history, symptoms, anatomy, and overall risk profile. Prior hemorrhage, aneurysm-related features, medically refractory seizures, or accessible low-grade AVMs are common reasons to discuss treatment, while observation may be preferred for high-risk unruptured lesions.

What are the main treatment options?

Options include endovascular embolization, microsurgical resection, stereotactic radiosurgery (SRS), or combined multimodality strategies—selected based on AVM grade, size, location, venous drainage, and patient-specific factors.

✓ PATIENT EDUCATION

Brain Arteriovenous Malformations (AVM)

Q: You’ve been diagnosed with an AVM — what does that mean?

A brain AVM is a congenital vascular anomaly (present from birth). It is not cancer, but it carries a risk of intracranial hemorrhage. Each AVM is assessed individually based on size, location, venous drainage and other risk features.

Q: How is an AVM diagnosed?

Evaluation commonly includes brain MRI and, when appropriate, CTA. Digital subtraction angiography (DSA) is the gold standard because it characterizes arterial feeders, fistulas, venous drainage patterns, and can detect intranidal aneurysms.

Q: When is it an emergency?

Seek urgent care for sudden severe headache, new weakness or numbness, a new seizure, sudden confusion, or loss of consciousness, as these may indicate hemorrhage or acute neurological injury.

Arteriovenous malformations (AVM) are congenital vascular anomalies in which arteries connect directly to veins without an intervening capillary bed. This “shortcut” creates a high-flow circulation and increases the risk of intracranial hemorrhage.

The Neuroknife team specializes in diagnosis, individualized risk stratification, and comprehensive AVM treatment using a tailored combination of microsurgery, endovascular embolization, and stereotactic radiosurgery—aligned with leading international standards and academic protocols (Harvard, Mayo Clinic, UCSF).

Annual hemorrhage risk: 1–2% Higher after prior rupture Patient-specific risk modifiers Surgery and/or embolization when appropriate

You’ve been diagnosed with an AVM — what does that mean?

An AVM is a congenital vascular anomaly—meaning you are born with it. It is not cancer. The primary concern, however, is intracranial hemorrhage.

Each AVM must be evaluated on its own terms: size, location, venous drainage pattern, presence of an intranidal aneurysm, prior hemorrhage, and other individualized features.

What is an arteriovenous malformation?

It is an abnormal “tangle of vessels” (the nidus) in which arteries connect directly to veins without a capillary network, leading to:

high-flow hemodynamics
venous dilation
risk of rupture and hemorrhage

Why does an AVM form? Causes & genetic considerations

Most AVMs are congenital (present from birth). Unlike cavernous malformations, AVMs typically do not follow a clear inherited genetic pattern.

Features that can increase hemorrhage risk include:

Prior hemorrhage (the strongest predictor of future bleeding)
Intranidal aneurysm
Deep anatomical location
Exclusive deep venous drainage
Venous outflow stenosis
Small nidus size (potentially associated with higher intranidal pressure)

Symptoms & hemorrhage risk

AVMs may be entirely asymptomatic or present with:

Hemorrhage (rupture) — the most common first presentation
Seizures
Headache, focal or migraine-like
Neurologic deficits

Annual hemorrhage risk

~1–2% per year for unruptured AVMs without high-risk features
~5–10% per year when high-risk features are present
>10% per year after a prior hemorrhage

Lifetime cumulative hemorrhage risk can be approximated by: 1 – (1 – R)^L where R = annual risk and L = years of life expectancy.

How is an AVM diagnosed?

A complete AVM workup commonly includes:

Brain MRI — defines the nidus and detects prior hemorrhage
CTA — rapid vascular imaging
DSA (digital subtraction angiography) — the gold standard:
- Characterizes arterial feeders
- Identifies fistulas and venous drainage patterns
- Detects intranidal aneurysms

When is treatment necessary?

The decision is individualized and based on hemorrhage risk, age, Spetzler–Martin grade, symptoms, and anatomical accessibility.

Common indications for treatment

Prior hemorrhage
Intranidal aneurysm
Seizures not adequately controlled with medication
New or progressive neurologic symptoms
Low-grade AVMs (Spetzler–Martin I–III)

When observation may be preferred

High-grade, unruptured AVMs (Spetzler–Martin IV–V)
Patients with a high procedural/surgical risk profile

Treatment options

1) Endovascular embolization

Flow reduction or cure in selected cases
Preoperative adjunct to improve microsurgical safety
Treatment of an intranidal aneurysm or high-risk weak point

2) Microsurgical AVM resection

The definitive option for many low-grade AVMs.

Immediate eradication of the nidus
Eliminates future hemorrhage risk once confirmed cured

3) Stereotactic radiosurgery (SRS)

Best suited for small to medium AVMs
Gradual obliteration over ~2–3 years

4) Combined (multimodality) therapy

Many AVMs require a staged combination of embolization plus microsurgery or SRS, to achieve safer and more effective durable treatment.

What should I expect in the hospital?

Pre-treatment DSA and high-resolution MRI planning
Neuronavigation and advanced microsurgical technique where indicated
Observation in a high-dependency unit or ICU for 24–48 hours when appropriate
Stepwise return to activity with individualized guidance

Recovery & long-term prognosis

Prognosis depends on:

Spetzler–Martin grade
Whether hemorrhage has occurred
Success in achieving complete nidus obliteration
Any neurologic deficits present before treatment

Daily life & restrictions

Avoid activities with a meaningful risk of head injury
Optimize blood pressure control
Driving restrictions may apply in patients with seizures
Regular exercise is often acceptable in stable AVMs, with individualized guidance

When is it an emergency?

Sudden, severe “worst headache of life”
New weakness on one side, numbness, gait instability
A new seizure
Sudden confusion or loss of consciousness

What should I ask my neurosurgeon?

Need a second opinion for an AVM?

The Neuroknife team provides comprehensive review, individualized risk stratification, and advanced treatment pathways in microsurgery, embolization, and stereotactic radiosurgery.

Send us your imaging for review