Use of the Modified Rankin Scale to assess outcome after arteriovenous malformation radiosurgery

OBJECTIVE: To present the results of arteriovenous malformation (AVM) radiosurgery using the Modified Rankin Scale (MRS) as the primary outcome measure and to analyze whether previous AVM rupture or other factors have an effect on outcomes after AVM radiosurgery. METHODS: We reviewed outcomes after AVM radiosurgery for 243 patients from 1990 and 2001. The mean follow-up after radiosurgery was 65 months. RESULTS: Forty-one patients (17%) sustained a decline in MRS (median -2) after AVM radiosurgery. We noted a decline in MRS in 4% of patients 1 year after radiosurgery, 8% of patients at 3 years after radiosurgery, and 15% of patients at 7 years after radiosurgery. The radiosurgery-based AVM score correlated with a decline in MRS after AVM radiosurgery in multivariate testing (odds ratio 2.1; 95% CI 1.2 to 3.6; p < 0.01). CONCLUSIONS: Previous AVM rupture did not influence neurologic deterioration after AVM radiosurgery. The radiosurgery-based AVM score predicted the chance of a worse MRS after radiosurgery.