Arteriovenous malformations (AVMs)

1. What is the pressure in an AVM? Are larger or smaller AVMs more likely to result in hemorrhage?
2. What is the lifelong risk of hemorrhage from an existent AVM?
3. When is bleeding most likely to occur?
4. What is the presentation of an AVM rupture?

Answers:
1. Low pressure. The larger the shunt, the lower the interior pressure. Smaller AVMs are more likely to result in hemorrhage due to higher pressure.
2. 40-50%. First hemorrhage is fatal in 10%.
3. Ages 20-40 years.
4. Hemorrhage (parenchymal, subarachnoid, intraventricular), seizures, headaches.