Cerebral AVMs are a concern to the stroke neurologist because of their propensity to present as an intracerebral hemorrhage. The connections of arteries directly to veins without the intervention of a high resistance capillary network alter normal cerebral hemodynamics. How the long term changes in vessel characteristics including vascular remodeling respond to the abnormal physics caused by AVMS is not fully understood.
Using quantitative magnetic resonance angiography (QMRA), Alaraj et al. estimated the wall shear stress (WSS), the force of blood against the cerebrovascular endothelium, in the patients with AVMs before and after treatment. In a cohort of 21 patients undergoing embolization of their AVM, the investigators demonstrated that the WSS was increased in the feeder arteries of the AVM compared to the normal contralateral vessel prior to the procedure. After embolization, the WSS fell to levels comparable to the contralateral vessels.
Additionally, in a subset of 17 patients who underwent resection of the AVM after embolization further reduction of the WSS was demonstrated. The mean WSS forces after surgical receptions demonstrated a trend to be lower than the mean on the contralateral normal vessel, but this did not achieve statistical significance.
Given that WSS has been implicated as a stimulus for vessel remodeling and vessel diameter, noninvasive measurement of WSS using QMRA may represent an intriguing method to monitor the efficacy of treatment for cerebral AVMs. Further, this study is important in that it is contrast to the only other study of WSS in AVMs which found identical WSS in the AVM feeders and normal contralateral vessels. The authors contend that their use of QMRA is more accurate than the TCD used in the 1995 study.