A Modified Radiosurgery-Based Arteriovenous Malformation Grading Scale and Its Correlation With Outcomes

Purpose The Pittsburgh radiosurgery-based arteriovenous malformation (AVM) grading scale was developed to predict patient outcomes after radiosurgery and was later modified with location as a two-tiered variable (deep vs. other). The purpose of this study was to test the modified radiosurgery-based AVM score in a separate set of AVM patients managed with radiosurgery. Methods and Materials The AVM score is calculated as follows: AVM score = (0.1)(volume, cc) + (0.02)(age, years) + (0.5)(location; frontal/temporal/parietal/occipital/intraventricular/corpus callosum/cerebellar = 0, basal ganglia/thalamus/brainstem = 1). Testing of the modified system was performed on 293 patients having AVM radiosurgery from 1992 to 2004 at the University of Pittsburgh with dose planning based on a combination of stereotactic angiography and MRI. The median patient age was 38 years, the median AVM volume was 3.3 cc, and 57 patients (19%) had deep AVMs. The median modified AVM score was 1.25. The median patient follow-up was 39 months. Results The modified AVM scale correlated with the percentage of patients with AVM obliteration without new deficits (≤1.00, 62%; 1.01–1.50, 51%; 1.51–2.00, 53%; and >2.00, 32%; F = 11.002, R2 = 0.8117, p = 0.001). Linear regression also showed a statistically significant correlation between outcome and dose prescribed to the margin ( F = 25.815, p