Background: Adverse radiation effects (ARE) with increased parenchymal T2 signal change occurs more frequently following radiosurgery for arteriovenous malformation (AVM) than for tumours, suggesting vascular parameters play a role in addition to dosimetry parameters. A prediction model comprising AVM location and 12Gy volume has been reported1. 

     We aimed to test this model on our institutions cohort of AVMs and further define vascular parameters which may predict symptomatic radiation effects.

     102 AVMs have been treated at our institution between 2005 and 2009. 85 patients have at least 12 months complete clinical and radiological follow up and comprise the study group for this study of complications. 

     All treatment plans were based on fused stereotactic MR, CT and angiography. Any new onset headaches, new or worsening seizures or neurological deficit were classed as an adverse event.

     There are 17 children and 68 adults in the study group with a mean age of 34 (range 6 – 74). There were a total of 21(24.7%) patients who suffered adverse effects, with 7 patients with permanent ARE (8.2%). 4 patients developed fixed visual field deficits. 12Gy volume was the most significant predictor of ARE (p<0.001). Application of the postradiosurgery injury expression score did not predict complications in our series (p=0.365). Occipital and parietal locations are the most significant locations (OR 2.77 and 17.061). Speztler-Martin grade and arterial supply, classified as either cortical or deep perforators were not significant factors in the development of complications (p =0.41).

     This is a retrospective study.

     12Gy volume remains the most accurate predictor of ARE. Occipital and parietal location correlates with a higher risk of ARE. 

     With a high percentage of permanent visual field defects in the series, this suggests the optic radiation is a critical radiosensitive structure.