Wall shear stress on ruptured and unruptured intracranial aneurysms at the internal carotid artery.

BACKGROUND AND PURPOSE Hemodynamics is often recognized as one of the major factors in aneurysm rupture. Flow impingement, greater pressure, and abnormal wall shear stress are all indications for aneurysm rupture. Characterizing wall shear stress for intracranial aneurysms at similar anatomic locations may help in understanding its role. MATERIALS AND METHODS Twenty-six intracranial aneurysms at the paraclinoid and superclinoid segments of the internal carotid artery from 25 patients between July 2006 and July 2007 were studied retrospectively. Among them, 8 aneurysms were ruptured and 18 were unruptured. Computational fluid dynamics was used to determine the wall shear distribution. Morphologic and hemodynamic variables was analyzed by using the Mann-Whitney rank sum test. RESULTS Wall shear stress was qualitatively the same throughout the cardiac cycle; thus, only wall shear stress at the end of diastole was compared. Both ruptured and unruptured aneurysms have similar maximal wall shear stress (26 versus 23 N/m(2)), and mean wall shear stress is shown to be a function of the aneurysm area. Ruptured aneurysms also have a greater portion of aneurysm under low wall shear stress (27% versus 11% for unruptured aneurysms, P = .03). CONCLUSION For intracranial aneurysms at the internal carotid artery, an area of low wall shear is associated with aneurysm rupture.