Most people with AVMs have no symptoms. Often, they are found when patients are screened for another condition, and an AVM becomes visible on a CT scan or an MRI.
Symptoms do occur in about 12 percent of people with AVMs. These are typically seen between the ages of 10 and 30 and can include:
- sudden and severe headaches or seizures
- muscle weakness or paralysis
- numbness and tingling
- problems with vision, language use, coordination, or memory
Most of these problems results from direct hemorrhage from AVM or seizures caused by the AVM. Some of these problems result from the "steal effect."
In these cases, a very large AVM with a high blood flow will “steal” blood from other areas of the brain, causing decreased function in those areas. Symptoms from the steal effect are rare however.