Purpose/objective: To elucidate how the risks of developing temporary and permanent neurological sequelae from radiosurgery for arteriovenous malformations (AVM) are related to AVM location, the addition of stereotactic magnetic resonance (MR) imaging to angiographic targeting, and prior hemorrhage or neurological deficits.
Materials and methods: We evaluated follow-up imaging and clinical data in 332 AVM patients who received gamma knife radiosurgery at the University of Pittsburgh between 1987 and 1994. All patients had regular clinical or imaging follow-up for a minimum of 2 years (range: 24-96 months, median = 45 months). There were 83 patients with MR-assisted planning, 187 with prior hemorrhages, and 143 with prior neurological deficits.
Results: Symptomatic postradiosurgery sequelae (any neurological problem including headache) developed in 30 (9%) of 332 patients. Symptoms resolved in 58% of patients within 27 months with a significantly greater proportion (p = 0.006) resolving in patients with Dmin < 20 Gy vs. > or = 20 Gy (89 vs. 36%). The 7-year actuarial rate for developing persistent symptomatic sequelae was 3.8%. We first evaluated the relative risks for different locations to construct a postradiosurgery injury expression (PIE) score for AVM location. Multivariate logistic regression analysis of symptomatic postradiosurgery sequelae identified independent significant correlations with PIE location score (p = 0.0007) and 12 Gy volume (p = 0.008), but with none of the other factors tested (p > 0.3), including the addition of MR targeting, average radiation dose in 20 cc, prior hemorrhage, or neurological deficit. We used these results to construct a risk prediction model for symptomatic postradiosurgery sequelae. The risk of radiation necrosis was significantly correlated with PIE score (p < 0.048), but not with 12-Gy volume.
Conclusion: The risks of developing complications from AVM radiosurgery can be predicted according to location with the PIE score, in conjunction with the 12-Gy treatment volume. Further study of factors affecting persistence of these sequelae (progression to radiation necrosis) is needed.