Objective: Diffuse arteriovenous malformations (AVM) have non-compact niduses, irregular margins, and intervening brain parenchyma. Deep perforating arteries often contribute to the ragged border of these diffuse AVMs. We hypothesized that diffuseness and deep perforator supply increase the difficulties and risks associated with microsurgical AVM resection.
Methods: Diffuseness was quantified using computer-generated outlines of AVMs on angiograms, contour plots with varying image intensities, and calculations of nidus area-intensity profiles. Diffuse AVMs had nonlinear area-intensity profiles with high transition intensities ([I*] greater than 0.5). A consecutive series of 304 patients who were treated with microsurgical AVM resection over a period of 7.8 years was analyzed, along with quantification of diffuseness in a subset of 103 consecutive patients. Neurological outcomes were assessed by using the Modified Rankin Scale, and logistic regression analysis was used to identify predictors of deterioration and poor outcome at late follow-up evaluation.
Results: Diffuse niduses were observed in 25% of patients, and 18% of patients had deep perforating artery supply. Patients with compact AVMs were more likely to have good outcomes or overall improvement (88 and 87%, respectively) than patients with diffuse AVMs (65 and 54%, respectively) (P = 0.008 and P < 0.001, respectively). Similarly, absence of deep perforator supply was associated with good outcomes or improvement in 85 and 78% of patients, respectively, compared with 63 and 64% of patients, respectively, in patients with deep perforator supply (P < 0.001 and P = 0.028, respectively). By logistic regression analysis, diffuseness and deep perforator supply were both associated with significant increases in surgical risk.
Conclusion: Diffuseness and deep perforating artery supply are subtle features of an AVM that predict worse outcomes after microsurgical resection. Diffuseness makes surgical planes more difficult to determine and follow, whereas deep perforators are friable, poorly visualized, and located in eloquent white matter tracts. The Spetzler-Martin grading scale does not directly account for these two features; however, they should be considered carefully when making treatment recommendations to patients with AVMs.