Elena Zapata-Arriaza, MD
@ElenaZaps
Stereotactic radiosurgery (SRS) has emerged as an alternative to neurosurgery or endovascular treatment for selected brain arteriovenous malformations (bAVM) management. Localization, size or perioperative risk are some of the selection criteria for SRS employment. Hemorrhagic risk of bAVM after SRS is based on single center studies. This study aims to obtain scientific evidence about bAVM hemorrhage rates before and after SRS and identify predictors of pre-post SRS AVM hemorrhage.
Patients with AVM treated with SRS in a single session from 1987 to 2014 were collected for the International Radiosurgery Research Foundation, formed by 8 institutions. For each AVM, Spetzler-Martin(SM) grade, virginia Radiosurgery AVM scale and modified radiosurgery-based AVM score were collected. In terms of SRS variables, margin dose, maximum dose and number of isocenters were analyzed. Radiological follow-up (with magnetic resonance image with/without contrast and computed tomography as alternative) was performed every 6 months for the first 2 years after SRS, and yearly thereafter. If the patient developed new or symptoms worsening, additional neuroimagen was performed.
Among 2320 AVM patients who underwent SRS, deep AVM location, the presence of an AVM-associated arterial aneurysm, and lower SRS margin dose were independent predictors of post-SRS hemorrhage. The post-SRS hemorrhage rate was lower for obliterated versus patent AVMs (6.0 versus 22.3 hemorrhages/1000 person-years). The AVM hemorrhage rate decreased from 15.4 hemorrhages/1000 person-years before SRS to 11.9 after SRS. The post-SRS hemorrhagic rate was higher for SM grade IV-V. The outcomes of the matched ruptured versus unruptured AVM cohorts were similar.
The efficacy of SRS in AVM to prevent the bleeding is limited by the hemorrhagic risk in the latency period, which can range from 6 months to 2 years post-SRS. The management of the AVM must be multidisciplinary, with risk-benefit assessments in each case, counting on the natural history of the pathology itself. In this multidisciplinary management, radiosurgery is used in a specific profile of patients (size <3 cm, high periprocedural risk, deep territory AVM, etc.). The efficacy of this treatment is variable according to the published series and depends on multiple factors (plexal or fistulous AVM, AVM volume, used dosage, etc.). One of the advantages of this study is the identification of predictors that we should take into account when considering this therapeutic option in patients with AVMs, knowing that the deep location, an SM grade of IV-V or the existence of arterial aneurysm should make us evaluate other therapeutic options that are concomitant or prior to SRS. Likewise, the use of SRS reduces the risk of hemorrhage, but this effect is related to the obliteration of the nidus, which generates an area of uncertainty in the latency period of the SRS itself. In short, the management of MAVs should be as multidisciplinary as possible, using all the available evidence to indicate an option or therapeutic combination adjusted to each patient. In the case of the use of SRS, knowing which patients have a higher risk of bleeding will help in decision making.
