Effects of nidus microarchitecture on cerebral arteriovenous malformation hemodynamics

Intranidal vessel geometry and organization underlying flow within cerebral arteriovenous malformations (AVM) is poorly understood. We examine the relationship between intranidal vessel characteristics and AVM flow. Records of patients with AVM evaluated at our institution between 2007 and 2013 were retrospectively reviewed. Patients were included if surgical specimens were available and flows were obtained before treatment using quantitative magnetic resonance angiography. Intranidal vessels were identified and the diameter and cross-sectional area of each vessel were measured from digitized images of specimen slides. The relationship between vessel diameter, vessel cross-sectional area, AVM volume, and AVM flow was assessed. Twenty-nine patients were included. Mean total number of vessels per specimen was 133. Mean total AVM flow was 340 ± 276 mL/min. Mean vessel diameter ranged from 0.18-2.37 mm and mean vessel cross-sectional area ranged from 0.09-9.46 mm(2). Linear regression analysis showed that total flow is significantly associated with larger AVM volume (R(2)=0.28, P=0.007), but not with number of vessels per section of the specimen (P=0.20) or mean vessel diameter (P=0.92). Exponential regression analysis demonstrated that AVM flow is significantly correlated to the sum of the cross-sectional vessel areas within each specimen (R(2)=0.16, P=0.05). Total AVM flow is significantly related to sum of the cross-sectional areas of all vessels within each nidus, rather than to total number of vessels or mean nidal vessel diameter. This finding suggests that the sum of the cross-sectional areas of intranidal vessels likely determines the resistance to flow within a cerebral AVM.