Treatment of arteriovenous malformations with stereotactic radiosurgery: A review

Abstract

AbstractArteriovenous malformations (AVMs) are vascular anomalies in which blood is shunted from the arterial to the venous system. In general, the annual risk of hemorrhage from an intracranial AVM is 2–3%. The morbidity and mortality rates associated with an initial hemorrhage are 30% and 10%, respectively. Based on these risks, intervention for unruptured AVMs is commonly recommended. Microneurosurgery is regarded by most physicians to be the treatment of choice for small cortical AVMs in noneloquent areas since resection can result in immediate cure. Stereotactic “radiosurgery” (radiation therapy) is commonly recommended for patients with deep AVMs ≤ 15 cm3 (approximately 3 cm in maximum dimension), where the risks of surgery are excessive. AVMs larger than approximately 15 cm3 may be treated with embolization followed by either microneurosurgery or stereotactic radiosurgery. When AVMs have been managed with stereotactic radiosurgery and the size of the lesion is taken into consideration, gamma knives, linear accelerators, and cyclotrons have produced similar angiographic complete obliteration rates. Gamma knives are expensive to purchase and install but are easy to operate. Linear accelerators are the most economical and versatile machines for stereotactic radiosurgery. Although cyclotrons are very expensive to build and operate, they afford maximal sparing of normal tissue when large lesions are irradiated. The complete obliteration rates 1,2, and 3 years following the management of AVMs ≤ 10 cm3 with stereotactic radiosurgery are 40–50%, 70–90%, and 75–95%, respectively. Following the administration of radiosurgery, 2‐year angiographic complete obliteration rates are 88% for AVMs <4 cm3, 75% for AVMs 4–10 cm3, 67% for AVMs 11–25 cm3, and 39% for AVMs 26–70 cm3. Much lower (0‐45%) long‐term complete obliteration rates have been obtained with fractionated photon and neutron beam radiation therapy, apparently due to the administration of inadequate total doses. The crude incidence of complications following the treatment of AVMs with stereotactic radiosurgery is approximately 3%, with no treatment‐related mortality. Patients with AVMs in the brain stem, thalamus, or basal ganglia are at higher risk for complications. In the future, authors should consider reporting the number of patients who undergo follow‐up MRI or CT scans but not angiography and consider presenting complication rates as a function of time in order to allow one to more accurately assess results. © Wiley‐Liss, Inc.