The arteries carry blood rich with oxygen from the lungs, and the veins carry blood back to the heart for recirculation. Each vessel is normally separate and travels in its own pathway. In an AVM, the blood vessels are tangled together and do not travel in their own path. Much like a small ball of string, the vessels are wrapped around each other. An AVM is something a person is born with and usually is not detected until the age of 20 to 50 years.
Symptoms begin as the person ages and the vessels become thickened.
Eventually the vessels may leak or even rupture. The symptoms the person experiences are due to this leakage of blood into the surrounding brain tissue. Often the headache is due to a rupture of the vessels and may cause an intraparenchymal, subarachnoid or intraventricular hemmorhage. The headache is sudden and severe and may be accompanied by nausea and vomiting. The person may experience dizziness and may even lose consciousness.