Arteriovenous Malformations

Neurointerventional Radiology Procedures

Arteriovenous Malformations (AVM)

EMBOLIZATION OF VASCULAR LESIONS

There are many abnormalities of the blood vessels that affect the brain, head, neck, and spine. These include arteriovenous malformations (abnormal vessels forming a connection between the arteries and veins of the brain, spinal cord, or surrounding structures), dural arteriovenous fistulas (direct connections between the arteries and one of the large draining veins contained in the covering of the brain, without any abnormal vessels in between), traumatic vascular lesions (holes in vessels with bleeding or an expanding clot, fistulas between the arteries and veins of the head and neck, or tears in the lining of the vessels), carotid-cavernous fistulas (direct connections between the carotid artery and a surrounding vein [cavernous sinus] behind the eye), spinal vascular malformations (abnormal vessels forming abnormal connections between the arteries and veins of the spinal cord, its coverings, the bones or the spine, and/or the surrounding structures), and extracranial vascular malformations (abnormal vessels forming abnormal connections between the arteries and veins of the structures of the head and neck).

These lesions can be very difficult to treat. When surgery is planned, a catheter can be placed into an artery (usually in the leg, similar to an angiogram of the heart) and a smaller catheter is then threaded through to the artery or arteries supplying the lesion. Material is then injected to block off the blood supply to the lesion; this is called embolization. There are many different materials available, depending on the location and size of the vessels to be blocked off. Sometimes, embolization is performed before radiation therapy for an arteriovenous malformation. In other instances, surgery is not possible and embolization is performed to cure the lesion. In these cases, a catheter may also be placed into the veins draining the lesion for embolization of the veins. In the case of carotid-cavernous fistulas, traumatic arteriovenous fistulas, and certain holes in the walls of major vessels, material may be injected to try to plug the hole or the fistula. Occasionally, a stent (a metal tube designed to hold a vessel open) may be used as well. In some cases, it may be necessary to block a major artery (such as a carotid artery) to treat the problem. If this is necessary, a small balloon attached to a catheter is placed in the vessel and blown up to stop the blood flow temporarily (test occlusion). The patient is examined constantly to see if they tolerate this or develop any symptoms (such as those of a stroke). It there are no symptoms, the artery is blocked by injection of material (permanent occlusion). Depending on the circumstances, the patient may be able to go home the next day or may be kept for observation.

Figure 1: AP angiograms demonstrate a large arteriovenous malformation of the left parietal region. The film on the left demonstrates the feeding arteries from the middle cerebral artery system with a large draining vein medially to the sagittal sinus. The film on the right demonstrates several large feeding vessels from the posterior cerebral artery on the left side.

Figure 2: The AVM of the patient shown in Figure 1 after endovascular embolization using N-butyl-cyanoacryalate glue for part of the AVM. As can be seen, the AP angiogram on the carotid circulation (left) shows a greatly diminished arterial to venous shunt. As well, the film of the right demonstrates decreased filling from the posterior cerebral supply to the AVM.

Figure 3: AP angiograms following surgical resection of the large AVM of the patient shown in Figures 1 and 2. Preoperative embolization made the operation safer with a minimum of blood loss at the time of operation. As can be seen on the carotid injection (left film), there is no arterial to venous shunting. The vertebral injection (right film) shows no AV shunting. The patient made an excellent recovery from surgery with no neurologic deficits.