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Y-Stent Coiling of Basilar Bifurcation Aneurysms Induces a Dynamic Angular Vascular Remodeling With Alteration of the Apical Wall Shear Stress Pattern

Gao, Bulang MD, PhD; Baharoglu, Merih I. MD; Cohen, Alex D. MD; Malek, Adel M. MD, PhD

doi: 10.1227/NEU.0b013e3182846d9f
Research-Human-Clinical Studies

BACKGROUND: Although wide-necked basilar bifurcation aneurysms are treated with Y-stent coiling, the effect of this intervention on vessel configuration and hemodynamics is unknown.

OBJECTIVE: To investigate the immediate and delayed effects of Y-stenting using self-expanding microstents on basilar bifurcation architecture and hemodynamics.

METHODS: Fifteen patients underwent basilar Y-stent coiling and imaging with rotational angiography. Vascular angles were measured between proximal P1 segments of the posterior cerebral arteries (α) and between the basilar artery and each P1 segment (β1,2) in the anteroposterior and γ1,2 sagittal planes. Patient-specific computational fluid dynamic analysis was used to estimate wall shear stress (WSS) changes with treatment.

RESULTS: In the anteroposterior plane, Y-stenting significantly decreased angle α and increased β angles immediately after stent coiling (P < .05 and P < .01, respectively) in a continued dynamic remodeling that progressed further in later months; sagittal γ angles also decreased (P < .0001). This novel stent-induced geometric progressive remodeling resulted in effective straightening and narrowing of the basilar bifurcation angle α (150.0 degrees vs 113 degrees, P < .0001) with significant correlation (r = 0.39, P < .05) between pretreatment proximal P1 angles and maximal angular change. Computational fluid dynamic analysis showed the angular remodeling led to significant narrowing of the WSS interpeak at the apex, redirecting high WSS away from the neck transition zone with native vessel toward the inert coil mass.

CONCLUSION: Y-configuration stent coiling induced immediate and, more significantly, a previously undefined delayed cerebrovascular remodeling. This progressive stent-induced angular remodeling alters perianeurysmal hemodynamics, independent of the flow-diverting properties of stent struts, thus shifting the balance of hemodynamic forces affecting aneurysm development and evolution.

ABBREVIATIONS: BA, basilar artery bifurcation

CFD, computational fluid dynamics

3-D–RA, 3-dimensional rotational angiography

ICA, internal carotid artery

IEL, internal elastic lamina

WSS, wall shear stress

Cerebrovascular and Endovascular Division, Department of Neurosurgery, Tufts Medical Center and Tufts University School of Medicine, Boston, Massachusetts

Correspondence: Adel M. Malek, MD, PhD, Department of Neurosurgery, Tufts Medical Center, 800 Washington Street, #178, Proger 7, Boston, MA 02111. E-mail:

Received October 10, 2011

Accepted December 11, 2012

Copyright © by the Congress of Neurological Surgeons