Elsevier

World Neurosurgery

Volume 78, Issue 5, November 2012, Pages 462-468
World Neurosurgery

Peer-Review Report
Hemodynamic Analysis of Growing Intracranial Aneurysms Arising from a Posterior Inferior Cerebellar Artery

https://doi.org/10.1016/j.wneu.2011.09.023Get rights and content

Objective

The role of hemodynamics in the growth of intracranial aneurysms is not completely clear. We present a hemodynamic study with two adjacent unruptured aneurysms arising from one parent artery but growing in different ways. This study aimed to investigate whether there were differences in hemodynamic characteristics between the two growing aneurysms.

Methods

A 62-year-old female patient presented with six unruptured intracranial aneurysms. Catheter angiography at 6-month intervals revealed that two aneurysms located adjacently at the right posterior inferior cerebellar artery were growing over a 1-year period. Three-dimensional aneurysm geometries were acquired via rotational angiography. Computational fluid dynamic simulations were conducted on the 3D aneurysm geometries under patient-specific pulsatile flow conditions that were measured by magnetic resonance velocimetry.

Results

The proximal multilobular aneurysm demonstrated high flow and physiological levels of wall shear stress (WSS) in the region of growth, whereas the distal rounded aneurysm had low flow and low WSS in the growing sac.

Conclusion

Growing aneurysms can have heterogeneous hemodynamic and morphologic characteristics and different growing patterns. Growing regions of an aneurysm could be exposed to either high WSS at the inflow zone or low WSS and high oscillatory shear in the aneurysm sac.

Introduction

Hemodynamics is thought to influence the initiation, growth, and rupture of intracranial aneurysms (16). Although there seems to be general consensus that high wall shear stress (WSS) results in the initiation of intracranial aneurysms (13, 14, 15, 16), the hemodynamic conditions that drive the growth of aneurysms after initiation are still not completely clear. High WSS has been postulated to account for aneurysm progression from the distal neck where flow impinges (6, 8), whereas low WSS has been associated with aneurysm growth in the dome (1, 18, 19).

We present a hemodynamic study of two adjacent aneurysms originating from one parent artery but growing in different ways. Longitudinal data sets of 3D rotational angiography were used to reconstruct accurate geometries of the aneurysms and adjacent arteries. The purpose of this study was to determine whether there were differences in the hemodynamic characteristics of the two growing aneurysms.

Section snippets

Case Presentation

A 62-year-old hypertensive female patient presented with vertigo. Computed tomographic imaging showed no evidence of hemorrhage but the presence of multiple intracranial aneurysms. Magnetic resonance (MR) angiography performed in April 2009 revealed six intracranial aneurysms: two in the right middle cerebral artery, two adjacent ones in the right posterior inferior cerebellar artery (PICA), one in the left middle cerebral artery, and one at the tip of the basilar artery (Figure 1). The two

Results

Figure 4A shows reconstructed 3D models of the PICA aneurysm complex from the three angiographs: the baseline and two follow-ups. To clearly visualize the regions of aneurysm growth, we overlapped three models by aligning the VA to achieve accurate matching, because this parent artery experienced no change over the observation period (Figure 4B). Clearly, the proximal aneurysm (Aneurysm 1) grew slightly on the superior side, whereas the distal aneurysm (Aneurysm 2) showed enlargement of the

Discussion

The purpose of this study was to determine whether there were differences in the hemodynamics of two adjacent aneurysms that presented different morphologic and vascular characteristics and were growing in different ways. One aneurysm (Aneurysm 1), which was multilobular in shape, already had three prominent protrusions (lobes) with an atherosclerotic wall. During the examination period, it was seen to grow on a fourth bleb. The other aneurysm (Aneurysm 2) was reddish, thin walled, and round.

Conclusions

We have shown two growing aneurysms with different hemodynamic characteristics and growing patterns: a proximal multilobular aneurysm was growing a bleb near the inflow zone with high local velocity and physiological levels of WSS, whereas a distal rounded aneurysm was growing the entire sac featuring low and unstable intra-aneurysmal flow, with low WSS and higher OSI. Thus, growing aneurysms may have heterogeneous hemodynamic, morphologic, and vascular characteristics associated with different

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    Conflict of interest statement: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. H. M. receives grants from the National Institutes of Health.

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