Ahead of Print: Validation of the Supplementary AVM Grading Scale

Background: The supplementary grading system for brain arteriovenous malformations (AVM) was introduced in 2010 as a tool for improving preoperative risk prediction and selecting surgical patients.

Objective: To demonstrate, in this multicenter validation study, that supplemented Spetzler-Martin grades have greater predictive accuracy than Spetzler-Martin grades alone.

Methods: Data collected from 1009 AVM patients who underwent AVM resection were used to compare predictive powers of Spetzler-Martin grades (SM) and supplemented Spetzler-Martin grades (SM-Supp). Patients included the original 300 UCSF patients plus those treated thereafter (N=117), and an additional 592 patients from three other centers.

Results: In the combined cohort, the SM-Supp system performed better than SM system alone: AUROC=0.75 (95% CI: 0.71 – 0.78) for SM-Supp and AUROC=0.69 (95% CI: 0.65 – 0.73) for SM (p< 0.001). Stratified analysis fitting models within three different follow-up groupings (<6 months, 6 months – 2 years, and >2 years) demonstrated that the SM-Supp system performed better than SM system for both medium (AUROC=0.71 vs. 0.62, p=0.003) and long follow-up (AUROC=0.69 vs. 0.58, p=0.001). Patients with SM-Supp grades <= 6 had acceptably low surgical risks (0 – 24%), with a significant increase in risk for grades above 6 (39% – 63%).

Conclusion: This study validates the predictive accuracy of the supplementary grading system in a multicenter cohort. SM-Supp grade of 6 is a cut-off or boundary for AVM operability. Supplemented grading is currently the best method of estimating neurological outcomes after AVM surgery, and we recommend it as a starting point in the evaluation of AVM operability.

From: Validation of the Supplemented Spetzler-Martin Grading System for Brain Arteriovenous Malformations in a Multicenter Cohort of 1009 Surgical Patients by Kim et al.

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