What Is a Hemorrhagic Stroke?

7. Types of AVMs

A true AVM, the most common type, consists of a network of abnormal blood vessels directly connecting arteries and veins. Other types include venous malformation, where the abnormality affects only the veins, and occult or cryptic or cavernous AVM, a vascular malformation that doesn't actively shunt large amounts of blood but may bleed and produce seizures. Hemangiomas are unusual blood vessel structures on the brain surface, facial structures, or skin, and dural fistulas are abnormal networks of blood vessels that only involve the covering of the brain, the dura mater.