Extensive white matter changes after stereotactic radiosurgery for brain arteriovenous malformations: a prognostic sign for obliteration?

OBJECTIVE: Perinidal high-signal-intensity changes on T2-weighted magnetic resonance imaging can be seen surrounding radiosurgically treated brain arteriovenous malformations (AVM). Occasionally, these signal intensity changes develop far beyond the irradiated volume. A retrospective analysis of both the pre- and postradiosurgery magnetic resonance imaging and angiographic studies was performed to analyze the cause of these extensive perinidal white matter changes.
METHODS: The pre- and postradiosurgical magnetic resonance imaging and angiographic studies of 30 patients with T2 high-signal-intensity changes surrounding a brain AVM were analyzed retrospectively. Patients were divided into 2 groups on the basis of the extension of the signal intensity changes within or beyond the 10-Gy isodose area. The angiographic analysis was focused on the venous drainage pattern (deep versus superficial), venous stenosis, and the number of draining veins before and after radiosurgery. In addition, the obliteration rate was determined for the 2 subgroups.
RESULTS: Fourteen patients (47%) showed high-signal-intensity changes far beyond the 10-Gy isodose area. A single draining vein was more often present in these patients with extensive T2 hyperintensity signal changes than in the other group. Obliteration was achieved in 12 (88%) of 14 patients with extensive signal intensity changes, as opposed to 8 (50%) of 16 patients in the other group.
CONCLUSION: High-signal-intensity changes after radiosurgery for brain AVMs, far beyond the 10-Gy isodose area on T2-weighted images, are especially seen in brain AVMs draining through a single vein. The higher occlusion rate of brain AVMs under these circumstances is well appreciated.