Cerebral Arteriovenous Malformations

Abstract

Arteriovenous malformations (AVMs) are vascular abnormalities consisting of fistulous connections of arteries and veins without a normal intervening capillary bed. In the cerebral hemispheres, they frequently occur as cone-shaped lesions with the apex of the cone reaching toward the ventricles. Nearly all AVMs are thought to be congenital. Supratentorial location is the most common (90%). The most common presentation of an AVM is intracerebral hemorrhage (ICH). After ICH, seizure is the second most common presentation. Other presentations of AVMs include headache and focal neurological deficits, which may be related to steal phenomena or other alteration in perfusion in the tissue adjacent to the AVM, such as venous hypertension from arterialization of normal draining veins. In managing unruptured AVMs, it is important to understand the natural history of these vascular malformations. The decision for no treatment or for a single modality or multimodality treatment paradigm also involves being familiar with the outcomes and risks of each treatment modality—microvascular resection, endovascular embolization, and stereotactic radiosurgery. Finally, the patient-related factors, such as age, general medical condition, neurological condition, occupation, and lifestyle must also be taken into consideration before reaching a conclusion. The treatment of AVMs is highly individualized. There is no universal algorithm or protocol to be followed when dealing with these unique problems. The currently used treatments for AVMs include microsurgical resection only, preoperative endovascular embolization followed by microsurgical resection, stereotactic radiosurgery only, preprocedural endovascular embolization followed by radiosurgical treatment, endovascular embolization only, and observation only. The ultimate goal for all of these modalities is cure for the patient; however, the only way to achieve cure is with complete obliteration of the AVM. Microsurgical resection, whenever it can be perfromed safely is the “gold standard” treatment for brain AVMs, and other methods of treatment must be measured against it. There is certainly a well-established role for adjunctive endovascular embolization of some AVMs. Clearly, there are specific situations, such as small deep AVMs in eloquent brain structures, in which microsurgery should not be used as the primary treatment modality; stereotactic radiosurgery and occasionally embolization (if there is reasonable expectation of complete obliteration by embolization) are the preferred treatment options in these cases. We also make a case for observation in patients with large AVMs in or near critical areas of the brain that are not ideal for surgical resection or radiosurgery. Here, the pursuit of treatment may actually be more harmful to the patient than the natural history of the AVM.