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Unruptured internal carotid artery bifurcation aneurysms: general features and overall results after modern treatment

  • Clinical Article - Vascular
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Abstract

Background

Internal carotid artery bifurcation aneurysms (ICAbifAs) present unique challenges to endovascular and surgical operators, and little is known about their natural history. We reviewed our institution’s experience with ICAbifAs studying outcomes of surgical and endovascular management and natural history.

Methods

Consecutive patients with unruptured ICAbifAs evaluated and/or treated over an 8-year interval were studied. Baseline demographics, neurovascular risk factors, aneurysm location and size, clinical presentation, treatment recommendations, and outcomes were prospectively collected and retrospectively analyzed. Continuous variables were compared with Student’s t test and categorical variables with Chi-square tests.

Results

Fifty-nine patients with 61 unruptured ICAbifAs were included. Seven aneurysms were treated surgically (11.5 %), 22 underwent endovascular treatment (36 %), and 32 were managed conservatively (52.5 %). In the surgical group, short- and long-term complete aneurysm occlusion rates were 100 % with no cases of perioperative or long-term permanent morbidity or treatment-related mortality. In the endovascular group, two patients (11.7 %) with giant aneurysms had perioperative thromboembolic events with transient morbidity. There was one case of aneurysm rupture at follow-up in a giant aneurysm treated with partial coil embolization. Complete/near-complete occlusion rates were 63 %. There was one case of aneurysm rupture after 114 aneurysm-years of follow-up in the conservative management group (0.89 %/year), but no ruptures were observed in small aneurysms selected for conservative management.

Conclusions

Unruptured small ICAbifAs have a benign natural history. In patients selected for treatment, excellent results can be achieved in the vast majority of patients with judicious use of endovascular and surgical therapy.

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Acknowledgments

The study was approved by the Mayo Clinic Institutional Review Board (IRB# 15–009699).

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Authors and Affiliations

  1. Department of Neurologic Surgery, Mayo Medical School, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA

    Biagia La Pira, Anthony M. Burrows, Harry J. Cloft & Giuseppe Lanzino

  2. Department of Radiology, Mayo Medical School, Mayo Clinic, Rochester, MN, USA

    Waleed Brinjikji, Harry J. Cloft, Roanna L. Vine & Giuseppe Lanzino

Authors
  1. Biagia La Pira
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  2. Waleed Brinjikji
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  3. Anthony M. Burrows
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  4. Harry J. Cloft
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  5. Roanna L. Vine
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  6. Giuseppe Lanzino
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Corresponding author

Correspondence to Giuseppe Lanzino.

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Funding

No funding was received for this research.

Conflict of interest

Drs. La Pira, Brinjikji, Burrows, and Cloft as well as Ms. Vine certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. Dr. Lanzino reports being a consultant for Covidien/Medtronic.

Ethical approval

For this type of study, formal consent is not required.

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Comments

Internal carotid artery bifurcation aneurysms are infrequent. Therefore, in most of the large prospective observational studies, these aneurysms are typically underrepresented and there is generally scarce information about the natural history and the outcome of this very challenging pathology. As for other aneurysms, the risk of aneurysmal rupture without intervention should be weighed against the risk of microsurgical clipping or endovascular treatment. In case of internal carotid artery bifurcation aneurysms, the literature data are occasional and not conclusive.

In this superb study, the authors present a prospectively collected and retrospectively analyzed cohort of unruptured internal carotid artery bifurcation aneurysms providing an original snapshot of the current treatment paradigm and overall result. The results are very important for the neurosurgical community in order to establish a treatment algorithm considering the newer endovascular available endovascular techniques.

As is well known, the internal carotid artery bifurcation aneurysms represent a challenge for both the endovascular and the microsurgical treatment. The presence of important perforating vessels, sometimes like a basket over the aneurysmal dome, and the very high allocation in the Circle of Willis offer the need of personalized solutions.

The incidence in the authors’ single institution was 61 patients of 1253 patients of unruptured intracranial aneurysms. The 5 % incidence accompanied by the evidence of a significantly younger age and a higher rate of smoking and aneurysm multiplicity in a large series is a new unpublished information, which provides a new perspective in the neurovascular field. Moreover, the overall results were very good for all treatment modalities, without mortality or permanent severe disability. Nevertheless, the seven patients treated by microsurgery scored better results as the endovascular cohort, with a higher aneurysm occlusion rate (100 vs. 60 %) and minor recurrence rate. Due the low statistical power, these data should be considered with caution, even if this reflects our daily clinical experience.

Overall, the authors deliver, through this well-written, thoughtfully constructed manuscript, a meaningful contribution to the literature in the challenging field of the unruptured internal carotid artery bifurcation aneurysm. The conclusions corroborate our personal experience in the field and encourage cerebrovascular neurosurgeons and neuroradiologists to approach unruptured internal carotid artery bifurcation aneurysms with the following arguments:

1. The treatment of unruptured internal carotid artery bifurcation aneurysms is safe and effective;

2. The treatment should be performed in younger patients or patients with known risk factors for development or rupture (smoking, familiarity, aneurysm multiplicity).

3. In the presence of very small aneurysms (<3 mm), the conservative treatment should be considered.

4. The endovascular treatment leads to a high rate of incomplete occlusions. However, no SAH was observed in the follow-up period;

5. Microsurgical clipping remains a valuable treatment option particularly for younger patients

6. Newer endovascular tools such as flow diverters have improved treatment options.

In the presence of a contralateral ICA occlusion, the authors suggest the treatment also of very small aneurysms. This point is still controversial, because of the vulnerability through the mechanical treatment and/or vasospasm may allow a functional occlusion of the only working carotid artery.

An interesting point for further research in the field is the analysis of the aneurysmal internal flow characteristics and the morphological irregularity of the aneurysmal wall (i.e., the presence of a daughter sac, a bottleneck shape, etc.) in order to identify further risk factors and to select more objectively the cohort that needs treatment.

Alex Alfieri

Lehel Török

Neuruppin, Germany

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La Pira, B., Brinjikji, W., Burrows, A.M. et al. Unruptured internal carotid artery bifurcation aneurysms: general features and overall results after modern treatment. Acta Neurochir 158, 2053–2059 (2016). https://doi.org/10.1007/s00701-016-2958-2

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  • DOI: https://doi.org/10.1007/s00701-016-2958-2

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