Classification of brain arteriovenous malformation nidus by magnetic resonance imaging

T1 and T2 weighted high field magnetic resonance imaging (MRI), computed tomography (CT) and intraarterial digital subtraction angiography (DSA) were performed in 30 patients with brain arteriovenous malformations. T2 weighted MR sequences proved superior to both CT and intraarterial DSA for displaying the configuration of the nidus, its intrinsic morphology and the state of the surrounding parenchyma. As was evidenced by histologic examination of the nidus in 18 cases, high-signal intensity of the intervening or surrounding parenchyma on T2 weighted images indicates gliosis. Preliminary experience with 5 cases suggests that gliosis of the intervening or surrounding brain parenchyma may make it safer to attempt embolization in these patients. Based on these parameters, we introduce a classification of brain AVM nidus.