Introduction: Embolization reduces flow in cerebral arteriovenous malformations (AVMs) before surgical resection, but changes in pulsatility and resistance indices (PI, RI) are unknown. Here, we measure PI, RI in AVM arterial feeders pre- and post-embolization/surgery.
Methods: Records of patients who underwent AVM embolization and surgical resection at our institution between 2007-2014 and had PI, RI, and flows obtained using quantitative magnetic resonance angiography were retrospectively reviewed. PI = [(systolic - diastolic flow velocity)/mean flow velocity] and RI = [(systolic - diastolic flow velocity)/systolic flow velocity]. Hemodynamic parameters were compared between the feeder and contralateral artery pre- and post-embolization/surgery.
Results: 32 patients with 48 feeder arteries underwent embolization (mean 1.3 sessions). 32 patients with 49 feeder arteries had surgery with/without preoperative embolization. Before any treatment, flow volume rate and mean, systolic, diastolic flow velocities were significantly higher in feeders versus contralateral counterparts (P<0.001 for each parameter), and PI, RI were significantly lower in feeder compared to contralateral vessels (P=0.003, P=0.002). After embolization, flow velocities within feeders were significantly higher than in the normal contralateral vessels, but PI, RI did not change significantly (Table). However, after surgery flow velocities within feeders decreased significantly and PI, RI normalized to match the indices of their contralateral counterparts (Table).
Conclusions: Following partial AVM embolization, PI, RI are unchanged and flow velocities in feeder arteries increase significantly likely due to redistribution of flow through residual nidus. Complete surgical resection results in normalization of PI, RI and a concomitant decrease in flow velocities.
Table: Changes in PI, RI after embolization and surgery.