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# Brain arteriovenous malformation

A tangle of abnormal blood vessels in the brain that links arteries directly to veins. It can bleed and is a common cause of brain hemorrhage in young people.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Middle cerebral artery](https://durgical.com/en/anatomy/middle-cerebral-artery/)
- [Circle of Willis](https://durgical.com/en/anatomy/cerebral-arterial-circle/)
- [Anterior cerebral artery](https://durgical.com/en/anatomy/anterior-cerebral-artery/)
- [Posterior cerebral artery](https://durgical.com/en/anatomy/posterior-cerebral-artery/)
- [Internal carotid artery](https://durgical.com/en/anatomy/internal-carotid-artery/)
- [Superior sagittal sinus](https://durgical.com/en/anatomy/superior-sagittal-sinus/)
- [Transverse sinus](https://durgical.com/en/anatomy/transverse-sinus/)
- [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/)
- [Parietal lobe](https://durgical.com/en/anatomy/superior-parietal-lobule/)
- [Temporal lobe](https://durgical.com/en/anatomy/middle-temporal-gyrus/)
- [Occipital lobe](https://durgical.com/en/anatomy/superior-occipital-gyri/)

## Why it happens

- [Hemorrhage: petechiae, purpura, ecchymosis, hematoma, and what blood loss does](https://durgical.com/en/general-pathology/hemorrhage-petechiae-purpura-ecchymosis-hematoma-and-what-blood-loss-does/)
- [Flow, pressure and resistance: Poiseuille and turbulent flow](https://durgical.com/en/physiology/flow-pressure-and-resistance-poiseuille-and-turbulent-flow/)
- [Blood vessels: artery, vein and capillary layers](https://durgical.com/en/histology/blood-vessels-artery-vein-and-capillary-layers/)

## What it is

A congenital vascular lesion in which arteries connect directly to veins through a tangle of abnormal vessels (the nidus) without a capillary bed. The high-flow, high-pressure shunt can rupture and cause intracerebral hemorrhage, or cause seizures and headache.

## Who gets it

Found in roughly 1 in 1,000 to 2,000 people, often diagnosed between ages 20 and 40. It is one of the leading causes of non-traumatic intracerebral hemorrhage in children and young adults. Many are now found incidentally on brain imaging done for other reasons.

## Causes

- Abnormal development of the vascular network during embryonic life; most are sporadic
- Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu), often with multiple malformations
- Somatic variants in vascular signalling genes (mainly KRAS) found in the vessel cells of many sporadic AVMs

## Risk factors

- Previous rupture (the strongest predictor of new bleeding)
- Deep location or deep venous drainage only
- Associated aneurysms on feeding arteries
- Hereditary hemorrhagic telangiectasia

## Pathophysiology

Without capillaries, arterial blood flows straight into thin-walled draining veins at high pressure. The veins dilate and may rupture, producing parenchymal hemorrhage, and less often subarachnoid or intraventricular bleeding. The high-flow shunt can also "steal" blood from surrounding brain, and the abnormal tissue irritates the cortex, causing seizures. Most occur in the cerebral hemispheres, often fed by branches of the [middle cerebral artery](https://durgical.com/en/anatomy/middle-cerebral-artery/).

## Classification

- Spetzler-Martin grade (I to V): size of the nidus (6 cm), eloquence of nearby brain, and presence of deep venous drainage; higher grades carry higher surgical risk
- Ruptured or unruptured
- Related lesions: cavernous malformation, developmental venous anomaly, dural arteriovenous fistula, vein of Galen malformation in infants

## Symptoms and signs

- Sudden severe headache with vomiting, focal deficits or loss of consciousness when it bleeds
- Seizures (the second most common presentation)
- Chronic headache
- Progressive focal deficits from steal or mass effect
- Pulsating noise in the head (bruit) in some patients
- Heart failure and enlarged head in newborns with vein of Galen malformation

## Red flags

- Sudden, worst-ever headache, vomiting or neck stiffness (hemorrhage)
- Drop in consciousness or new focal weakness
- First seizure or a seizure that does not stop
- Signs of raised intracranial pressure or hydrocephalus

## Diagnosis

**Clinical**
Suspected in a young person with intracerebral hemorrhage without hypertension, or with a first seizure. Neurological examination and Glasgow Coma Scale guide urgency.

**Tests**
Coagulation, blood count and type and screen before procedures. Electroencephalography in patients with seizures.

**Imaging**
Non-contrast CT shows acute hemorrhage. MRI and MR or CT angiography show the nidus and its relation to eloquent brain. Digital subtraction catheter angiography is the gold standard: it defines feeding arteries, the nidus, draining veins and associated aneurysms.

## Differential diagnosis

- Hypertensive intracerebral hemorrhage
- Ruptured saccular aneurysm (subarachnoid hemorrhage)
- Cavernous malformation
- Hemorrhagic brain tumour (glioblastoma, metastasis)
- Cerebral venous thrombosis with hemorrhagic infarct
- Moyamoya disease

## Goal of treatment

Stabilize acute hemorrhage, control seizures, and eliminate the malformation completely when the benefit outweighs the risk, to prevent future bleeding.

## Treatment

**Acute**
Emergency care of intracerebral hemorrhage: airway, blood pressure control, reversal of anticoagulation, treatment of raised intracranial pressure and hydrocephalus, and evacuation of a large hematoma.

**Surgical**
Microsurgical resection of the nidus, preferred for low-grade (Spetzler-Martin I-II) accessible lesions; it offers immediate cure.

**Procedure**
Endovascular embolization with liquid agents, usually before surgery or radiosurgery to reduce flow, and stereotactic radiosurgery for small deep lesions, which closes the nidus over 1 to 3 years.

**Medical**
Antiseizure drugs for patients with seizures and analgesics for headache.

**Follow-up**
Conservative observation for many unruptured lesions, with blood pressure control, follow-up imaging after radiosurgery to confirm obliteration, and neurological checks after treatment.

## Complications

- Intracerebral, intraventricular or subarachnoid hemorrhage
- Epilepsy
- Permanent neurological deficits
- Hydrocephalus
- Treatment complications: stroke, radiation injury, re-bleeding before complete obliteration

## Prognosis

Unruptured malformations bleed at about 2 to 4% per year, higher after a first rupture. Each hemorrhage carries a significant risk of death or disability. Complete obliteration essentially eliminates the bleeding risk.

## Test yourself

Think of the answer, then tap the question to see it.

## What structure is missing between arteries and veins in an arteriovenous malformation?

The capillary bed; arteries drain directly into veins through a nidus.

## What is the most common presentation of a brain AVM?

Intracerebral hemorrhage, followed by seizures.

## Which study is the gold standard to define an AVM?

Digital subtraction catheter angiography.

## Which three features make up the Spetzler-Martin grade?

Nidus size, eloquence of adjacent brain and presence of deep venous drainage.

## Which hereditary disorder is associated with multiple brain AVMs?

Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome).

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## Related conditions

- [Intracerebral haemorrhage](https://durgical.com/en/conditions/intracerebral-haemorrhage/)
- [Subarachnoid haemorrhage](https://durgical.com/en/conditions/subarachnoid-haemorrhage/)
- [Epilepsy and seizures](https://durgical.com/en/conditions/epilepsy-and-seizures/)
- [Status epilepticus](https://durgical.com/en/conditions/status-epilepticus/)
- [Ischaemic stroke](https://durgical.com/en/conditions/ischaemic-stroke/)
- [Migraine](https://durgical.com/en/conditions/migraine/)
- [Raised intracranial pressure and brain herniation](https://durgical.com/en/conditions/raised-intracranial-pressure-and-brain-herniation/)
- [Cerebral venous sinus thrombosis](https://durgical.com/en/conditions/cerebral-venous-sinus-thrombosis/)
- [Sturge–Weber syndrome](https://durgical.com/en/conditions/sturge-weber-syndrome/)
- [Hydrocephalus](https://durgical.com/en/conditions/hydrocephalus/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Cerebral arteriovenous malformation: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000779.htm) (MedlinePlus (U.S. National Library of Medicine), 2026).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/brain-arteriovenous-malformation/