Vascular malformations of the brain
- Lesion
Some brain vessels form abnormally from birth: tangles of arteries and veins or clusters of thin channels that can bleed or cause seizures.
What it is
Brain vascular malformations are developmental errors of vessel formation, not tumours. Arteriovenous malformations connect arteries directly to veins without capillaries, carry high flow and bleed in young adults. Cavernous malformations are clusters of thin-walled sinusoids without brain between them, prone to small repeated bleeds and seizures. Capillary telangiectasias and venous angiomas are usually incidental. Sturge-Weber syndrome adds a leptomeningeal angiomatosis to a facial port-wine stain.
Structure
- AVM gross: a wormlike tangle of vessels on the brain surface or in the parenchyma, often in the middle cerebral artery territory.
- AVM micro: vessels with irregular walls, some arterialised veins with reduplicated elastic lamina, hemosiderin and gliosis between.
- Cavernous micro: channels lined by endothelium with hyalinised walls, thrombi of different ages, calcification and a hemosiderin rim.
Brain vascular malformations compared
| Malformation | Structure | Brain between vessels | Main risk |
|---|---|---|---|
| Arteriovenous malformation | Arteries joined straight to veins, thick and thin walls mixed | Yes, gliotic | Hemorrhage, seizures, steal |
| Cavernous malformation | Back-to-back dilated thin-walled channels | No | Small repeated bleeds, seizures |
| Capillary telangiectasia | Dilated capillaries | Yes, normal | Usually none |
| Venous angioma | Enlarged veins draining normal brain | Yes, normal | Usually none |
Clinical notes
- AVM presents with hemorrhage, seizures or headache; a bruit may be heard.
- Cavernous malformations are often found on MRI as ‘popcorn’ lesions with a dark rim.
Test yourself
Think of the answer, then tap the question to see it.
What separates the vessels of a cavernous malformation from those of an AVM on histology?
In a cavernous malformation the channels are back to back with no brain tissue between them; an AVM has gliotic brain between its vessels.
Which is the most common brain vascular malformation and is usually harmless?
The venous angioma (developmental venous anomaly).
What are the brain findings of Sturge-Weber syndrome?
Leptomeningeal angiomatosis over the cortex with underlying atrophy and calcification, causing seizures, on the side of a facial port-wine stain.
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Cerebral arteriovenous malformation: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.