Introduction: The geometry and organization of intranidal vessels underlying flow within cerebral arteriovenous malformations (AVM) is poorly understood. Here, we examine the relationship between intranidal artery characteristics and AVM flow.

Methods: Records of patients with AVMs evaluated at our institution between 2007-2013 were retrospectively reviewed. Patients were included if a surgical specimen of the nidus was available and if flows were obtained before treatment using quantitative magnetic resonance angiography. Specimens were mounted on slides and stained with hematoxylin & eosin and elastic special stain. Intranidal arteries were identified and diameter and cross-sectional area of each artery were measured from digitized images. Total area of the slide studied and magnification used was the same for each patient. AVM volume was determined from digital subtraction angiography. Relationship between vessel diameter, vessel cross-sectional area, AVM volume, and AVM flow was assessed.

Results: 29 patients were included. Cohort characteristics are summarized in the Table. Mean total number of arteries 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 mm2. Linear regression analysis showed that total flow is significantly associated with larger AVM volume (R2=0.28, P=0.007) (Figure 1), but not with the number of arteries 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 areas within each specimen (R2=0.16, P=0.05) (Figure 2).

Conclusions: Total AVM flow is significantly related to the sum of the cross-sectional areas of all arteries within each nidus, rather than to the total number of arteries or mean nidal vessel diameter. This finding suggests that the sum of the cross-sectional areas of intranidal arteries likely determines the permeability of the cerebral AVM nidus.

Patient Care: Our study outlines the relationship between intranidal vessel organization and total AVM flow, which furthers our understanding of AVM hemodynamics and may be used to develop new strategies to treat AVMs.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the relationship between the geometry and organization of intranidal vessels and AVM flow, 2) Understand the histopathology of the cerebral AVM nidus, and 3) Appreciate the use of quantitative magnetic resonance angiography as a clinical and research tool.

References: Kailasnath P and Chaloupka JC. Mathematical modeling of AVM physiology using compartmental network analysis. Neurological Research. 1996;18:361-366.