Hemodynamic characteristics associated with cerebral aneurysm formation in patients with carotid occlusion

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The pathogenesis of cerebral aneurysms in patients with internal carotid artery (ICA) occlusion is hypothesized to be hemodynamic. For the first time, the authors quantify the hemodynamic characteristics associated with aneurysm formation in patients with ICA occlusion.


Records of patients with unilateral ICA stenosis or occlusion ≥ 90% who underwent hemodynamic assessment before treatment using quantitative MR angiography were retrospectively reviewed. The patients were classified into 2 groups based on the presence or absence of aneurysms. The hemodynamic parameters of flow volume rate, flow velocity, and wall shear stress (WSS) were measured in each vessel supplying collateral flow—bilateral A1 segments and bilateral posterior communicating arteries—and then compared between the groups.


A total of 36 patients were included (8 with and 28 without aneurysms). The mean flow (72.3 vs 48.9 ml/min, p = 0.10), flow velocity (21.1 vs 12.7 cm/sec, p = 0.006), and WSS (22.0 vs 12.3 dynes/cm2, p = 0.003) were higher in the A1 segment contralateral to the side of the patent ICA in patients with versus without aneurysms. All de novo or growing aneurysms in our cohort were located on the anterior communicating artery (ACoA) or P1 segment.


Flow velocity and WSS are significantly higher across the ACoA in patients who harbor an aneurysm, and de novo or growing aneurysms are often located on collateral vessels. Thus, robust primary collaterals after ICA occlusion may be a contributing factor in cerebral aneurysm formation.

ABBREVIATIONS ACoA = anterior communicating artery; ICA = internal carotid artery; PCoA = posterior communicating artery; QMRA = quantitative MR angiography; WSS = wall shear stress.

Article Information

Correspondence Fady T. Charbel: University of Illinois at Chicago, IL. fcharbel@uic.edu.

INCLUDE WHEN CITING Published online May 4, 2018; DOI: 10.3171/2017.11.JNS171794.

Disclosures Dr. Alaraj: consultant for Cordis-Codman. Dr. Charbel: consultant for Transonic Inc.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Bar graph showing hemodynamic characteristics in patients with versus without aneurysms. The mean flow, flow velocity, and WSS in the A1 segment contralateral to the patent ICA are higher in patients with aneurysms. * and **p ≤ 0.05.

  • View in gallery

    Illustrative cases. A and B: Digital subtraction angiogram (A) and QMRA image (B) obtained in a patient without an aneurysm. The flow in the contralateral A1 segment is 10.8 ml/min and the WSS is 6.0 dynes/cm2. C and D: Images obtained in a patient with an ACoA aneurysm. Digital subtraction angiogram (C). The arrow identifies the aneurysm on the digital subtraction angiogram, left ICA injection, oblique projection. QMRA image (D). The yellow arrow and plane indicate the location of the contralateral A1 segment flow (89.1 ml/min) and WSS (21.7 dynes/cm2) measurements. Figure is available in color online only.


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