Disease Overview

Malformations are abnormal connections between arteries and veins

• What is a neurovascular malformation (AVM and AVF)

  An arteriovenous malformation (AVM) or dural arteriovenous fistula (AVF) is an abnormal connection between blood vessels or the entanglement of blood vessels that causes shunting of blood from an artery to a vein, bypassing normal tissue and depriving oxygen and nutrients from that area of the brain.

• Causes

  Although most AVMs are congenital and relatively uncommon, the exact etiology or cause of their formation is unknown.

• Symptoms

  A brain arteriovenous malformation may not cause any signs or symptoms until the AVM ruptures, resulting in bleeding in the brain (hemorrhage). In about half of all brain AVMs, hemorrhage is the first sign. But some people with brain AVM may experience signs and symptoms other than bleeding related to the AVM. In people without hemorrhage, signs and symptoms of a brain AVM may include:

  • Seizures
  • Headache or pain in one area of the head
  • Muscle weakness or numbness in one part of the body

  Some people may experience more serious neurological signs and symptoms, depending on the location of the AVM, including:

  • Severe headache
  • Weakness, numbness or paralysis
  • Vision loss
  • Difficulty speaking
  • Confusion or inability to understand others
  • Severe unsteadiness

  Symptoms may begin at any age but usually emerge between ages 10 and 40. Brain AVMs can damage brain tissue over time. The effects slowly build up and often cause symptoms in early adulthood. Once you reach middle age, however, brain AVMs tend to remain stable and are less likely to cause symptoms. Some pregnant women may have worsened symptoms due to changes in blood volume and blood pressure. One severe type of brain AVM, called a vein of Galen defect, causes signs and symptoms that emerge soon or immediately after birth. The major blood vessel involved in this type of brain AVM can cause fluid to build up in the brain, and the head to swell. Signs and symptoms include swollen veins that are visible on the scalp, seizures, failure to thrive, and congestive heart failure.

• Diagnoses

  Due to advances in technology with brain imaging techniques, an increasing numbers of AVM/AVF are detected before rupture.

• Types and Classifications

  Arteriovenous malformation – abnormal tangle of blood vessels where arteries shunt directly into veins with no intervening capillary bed; high pressure. AVMs can form anywhere there are arteries and veins. Brain AVMs can occur on the surface (also called cortical), deep (in the thalamus, basal ganglia, or brainstem), and within the dura (the tough protective covering of the brain).

  Cavernoma – abnormal cluster of enlarged capillaries with no significant feeding arteries or veins; low pressure.

  Venous malformation – abnormal cluster of enlarged veins resembling the spokes of a wheel with no feeding arteries; low pressure, rarely bleeds and usually not treated.

  Capillary telangiectasia – abnormal capillaries with enlarged areas (similar to cavernoma); very low pressure, rarely bleeds and usually not treated.

  Dural AV fistula – direct connection between one or more arteries and veins into a sinus. The veins of the brain drain into venous sinuses (blood-filled areas located in the dura mater) before leaving the skull and traveling to the heart. Dural AV fistulas and carotid-cavernous fistulas (CCF) are the most common.