Introduction: Radiation-induced changes (RICs) are the most common complication of stereotactic radiosurgery (SRS) for brain arteriovenous malformations (AVMs), and they appear as perinidal T2-weighted hyperintensities on magnetic resonance imaging, with or without associated neurological symptoms. The aim of this systematic review and meta-analysis is to determine the rates of RIC after AVM SRS and identify risk factors.
Methods: A literature review was performed using PubMed and MEDLINE to identify studies reporting RIC in AVM patients treated with SRS. RICs were classified as radiologic (any neuroimaging evidence), symptomatic (any associated neurological deterioration, regardless of duration), and permanent (neurological decline without recovery). Baseline, treatment, and outcomes data were extracted for statistical analysis.
Results: Based on pooled data from 51 studies, the overall rates of radiologic, symptomatic, and permanent RIC after AVM SRS were 35.5% (1143/3222 patients, 32 studies), 9.2% (499/5447 patients, 46 studies), and 3.8% (202/5272 patients, 39 studies), respectively. Radiologic RIC was significantly associated with lack of prior AVM rupture (odds ratio [OR] = 0.57; 95% confidence interval [CI]: 0.47-0.69; P < .001) and treatment with repeat SRS (OR = 6.19; 95% CI: 2.42-15.85; P < .001). Symptomatic RIC was significantly associated with deep AVM location (OR = 0.38; 95% CI: 0.21-0.67; P < .001).
Conclusions: Approximately 1 in 3 patients with AVMs treated with SRS develop radiologically evident RIC, and of those with radiologic RIC, 1 in 4 develop neurological symptoms. Lack of prior AVM hemorrhage and repeat SRS are risk factors for radiologic RIC, and deep nidus location is a risk factor for symptomatic RIC.
Patient Care: SRS is an effective treatment option for brain AVMs, particularly those that are small- to medium-sized located in deep or eloquent brain regions. RIC is the earliest and most frequently observed complication following SRS for AVMs. Knowing the rates of RIC formation following SRS and identifying AVM features and treatment characteristics that are associated with symptomatic RIC formation will help guide management to reduce the rate of adverse outcomes. In addition, long term follow-up is crucial in patients with AVMs treated with SRS as certain types of RIC (e.g. cyst formation) have latency periods of several years.
Learning Objectives: By the conclusion of this session, participants should be able to:
1. Define radiologic, symptomatic, and permanent RIC and quote the approximate rates of their formation following AVM SRS.
2. Identify risk factors for the formation of RIC following SRS for AVMs.
3. Describe management strategies for the treatment of RIC.
4. Provide a pathophysiologic explanation for RIC.