Wide-neck aneurysms: systematic review of the neurosurgical literature with a focus on definition and clinical implications

Benjamin K. Hendricks Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona; and

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James S. Yoon Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona; and

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Kurt Yaeger Department of Neurosurgery, The Mount Sinai Health System, New York, New York

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Christopher P. Kellner Department of Neurosurgery, The Mount Sinai Health System, New York, New York

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J Mocco Department of Neurosurgery, The Mount Sinai Health System, New York, New York

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Reade A. De Leacy Department of Neurosurgery, The Mount Sinai Health System, New York, New York

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Andrew F. Ducruet Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona; and

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Michael T. Lawton Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona; and

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Justin R. Mascitelli Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona; and

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OBJECTIVE

Wide-necked aneurysms (WNAs) are a variably defined subset of cerebral aneurysms that require more advanced endovascular and microsurgical techniques than those required for narrow-necked aneurysms. The neurosurgical literature includes many definitions of WNAs, and a systematic review has not been performed to identify the most commonly used or optimal definition. The purpose of this systematic review was to highlight the most commonly used definition of WNAs.

METHODS

The authors searched PubMed for the years 1998–2017, using the terms “wide neck aneurysm” and “broad neck aneurysm” to identify relevant articles. All results were screened for having a minimum of 30 patients and for clearly stating a definition of WNA. Reference lists for all articles meeting the inclusion criteria were also screened for eligibility.

RESULTS

The search of the neurosurgical literature identified 809 records, of which 686 were excluded (626 with < 30 patients; 60 for lack of a WNA definition), leaving 123 articles for analysis. Twenty-seven unique definitions were identified and condensed into 14 definitions. The most common definition was neck size ≥ 4 mm or dome-to-neck ratio < 2, which was used in 49 articles (39.8%). The second most commonly used definition was neck size ≥ 4 mm, which was used in 26 articles (21.1%). The rest of the definitions included similar parameters with variable thresholds. There was inconsistent reporting of the precise dome measurements used to determine the dome-to-neck ratio. Digital subtraction angiography was the only imaging modality used to study the aneurysm morphology in 87 of 122 articles (71.3%).

CONCLUSIONS

The literature has great variability regarding the definition of a WNA. The most prevalent definition is a neck diameter of ≥ 4 mm or a dome-to-neck ratio of < 2. Whether this is the most appropriate and clinically useful definition is an area for future study.

ABBREVIATIONS

BAC = balloon-assisted coiling; CTA = CT angiography; DSA = digital subtraction angiography; EVT = endovascular therapy; FD = flow diversion; MRA = MR angiography; PED = Pipeline embolization device; SAC = stent-assisted coiling; WEB = Woven EndoBridge; WNA = wide-necked aneurysm; 3DRA = 3D rotational angiography.

OBJECTIVE

Wide-necked aneurysms (WNAs) are a variably defined subset of cerebral aneurysms that require more advanced endovascular and microsurgical techniques than those required for narrow-necked aneurysms. The neurosurgical literature includes many definitions of WNAs, and a systematic review has not been performed to identify the most commonly used or optimal definition. The purpose of this systematic review was to highlight the most commonly used definition of WNAs.

METHODS

The authors searched PubMed for the years 1998–2017, using the terms “wide neck aneurysm” and “broad neck aneurysm” to identify relevant articles. All results were screened for having a minimum of 30 patients and for clearly stating a definition of WNA. Reference lists for all articles meeting the inclusion criteria were also screened for eligibility.

RESULTS

The search of the neurosurgical literature identified 809 records, of which 686 were excluded (626 with < 30 patients; 60 for lack of a WNA definition), leaving 123 articles for analysis. Twenty-seven unique definitions were identified and condensed into 14 definitions. The most common definition was neck size ≥ 4 mm or dome-to-neck ratio < 2, which was used in 49 articles (39.8%). The second most commonly used definition was neck size ≥ 4 mm, which was used in 26 articles (21.1%). The rest of the definitions included similar parameters with variable thresholds. There was inconsistent reporting of the precise dome measurements used to determine the dome-to-neck ratio. Digital subtraction angiography was the only imaging modality used to study the aneurysm morphology in 87 of 122 articles (71.3%).

CONCLUSIONS

The literature has great variability regarding the definition of a WNA. The most prevalent definition is a neck diameter of ≥ 4 mm or a dome-to-neck ratio of < 2. Whether this is the most appropriate and clinically useful definition is an area for future study.

In Brief

The authors performed a systematic review of recent literature for the definition of wide-necked aneurysms (WNAs). The most prevalent definition of a WNA was a neck diameter of ≥ 4 mm or a dome-to-neck ratio of < 2. Whether this definition is the most appropriate definition is a topic of discussion and future research. The use of a standard definition would be beneficial when comparing various WNA studies.

Aneurysm anatomy is the most vital characteristic when considering treatment options. The surgeon must consider not only the aneurysm’s location but also its morphology, dome size, and neck size. These variables help to determine whether an endovascular or microsurgical approach is optimal and whether advanced techniques are necessary. Wide-necked aneurysms (WNAs) are a vaguely defined subset of cerebral aneurysms that require more advanced endovascular and microsurgical techniques than do narrow-necked aneurysms. From the endovascular standpoint, techniques (e.g., balloon-assisted coiling [BAC], stent-assisted coiling [SAC], and complex neck–support devices) have been developed to prevent coil prolapse into the parent artery. From the microsurgical standpoint, complex clipping techniques are necessary to completely obliterate the aneurysm neck, and revascularization is occasionally needed when clip reconstruction is not possible. The width of the aneurysm neck has been demonstrated to be one of the most important factors in determining the angiographic outcome after endovascular treatment.21

Although numerous studies have assessed the treatment of WNAs, there is no universally accepted definition. Historically, a WNA was first defined in 1994 as an aneurysm with a neck diameter ≥ 4 mm.8 The geometrical features of a WNA that correlated with coiling success led to an expansion of the definition to include aneurysms with a dome-to-neck ratio of < 2 in 1998 and < 1.5 in 2000.6,7 However, these definitions have not been used consistently to define WNAs in the neurosurgical literature. In many instances, the term has been generalized to include any aneurysm requiring adjunctive endovascular techniques, thus giving WNAs a more clinical, rather than objective, definition.19 The various definitions of WNAs have not been systematically reviewed to date. Therefore, we performed a systematic review of the neurosurgical literature to identify the most commonly used definition of WNAs and the most commonly used radiographic modality used to assess them.

Methods

We conducted this systematic review following the PRISMA guidelines for the design and application of the neurosurgical literature search (Fig. 1). A Boolean search of the PubMed database using the term “wide neck aneurysm” or “broad neck aneurysm” retrieved a total of 959 articles. These articles were then filtered by a publication date between January 1, 1998, and December 31, 2017, and an English-language filter, resulting in 786 articles. The total screening group of 786 articles underwent initial evaluation by review of the title and abstract to identify those studies that included 30 or more human subjects, resulting in 173 articles that underwent full-text review by searching the PDF file by keyword search for “wide” and “broad.” This keyword search resulted in 115 articles that clearly defined either wide-necked or broad-necked aneurysms and included 30 or more subjects. In addition, the reference lists of the 173 full-text articles were reviewed, and 23 additional studies were identified to undergo screening. This screening resulted in 10 studies that qualified for full-text evaluation, resulting in 8 additional studies that met criteria for inclusion. During a full-text analysis, we recorded the imaging modality used to measure the aneurysms in each study that included a WNA definition.

FIG. 1.
FIG. 1.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flowchart presenting an overview of the systematic review. Figure is available in color online only.

Results

The systematic neurosurgical literature review yielded 123 articles describing studies that met our criteria (≥ 30 patients and a clearly stated definition of WNA), and these articles were subsequently examined to determine how an aneurysm was designated as wide necked. The classification criteria for WNAs consistently included either measurements of neck diameter or calculation of a dome-to-neck ratio (Table 1). However, the dome-to-neck ratio was not always well defined in the retrieved articles, which resulted in inconsistencies in how the ratios were calculated (e.g., using aneurysm height, width, or maximum diameter). The imaging modalities, from which the measurements of the aneurysms were made prior to intervention, were recorded and are summarized in Table 2. Lastly, the primary treatment modality utilized in each study was recorded, and these modalities are summarized in Table 3.

TABLE 1.

Summary of threshold measurements for WNAs

DefinitionNo. of Studies (n = 123)
ND ≥4 mm or DTN <249
ND ≥4 mm26
ND ≥4 mm or DTN <1.518
DTN <28*
ND ≥4 mm or neck-to-dome ratio >0.76
DTN <14
DTN <1.54*
ND ≥4 mm or DTN <1.63
ND ≥4 mm or DTN <1.21
ND ≥4 mm or DTN <11
DTN <1.81
ND >7 mm1
ND ≥3 mm or DTN <11
ND ≥4 mm but ≤10 mm; dome size ≥4 mm but ≤20 mm; DTN <1.0; parent artery diameter ≥2 mm but ≤5 mm1

DTN = dome-to-neck ratio; ND = neck diameter.

One study included a dome-to-neck ratio of both < 2 and < 1.5 and is counted in both definition categories, resulting in 124 total studies instead of 123.

TABLE 2.

Imaging modalities used during qualitative and quantitative analysis of WNAs as reported in 123 articles

Imaging ModalityNo. of Studies (n = 122)
DSA87
DSA & MRA17
DSA, CTA, & MRA10
DSA & CTA6
MRA1
CTA1

only 122 studies are included because intraoperative observation alone was used in one of the 123 studies reviewed.

TABLE 3.

Management modalities reported in a systematic review of WNAs as reported in 123 articles

Treatment ModalityNo. of Studies
Endovascular117
 SAC55
 Primary coiling14
 Flow diverter9
 Coiling vs BAC vs SAC7
 WEB7
 SAC vs stenting6
 BAC vs SAC5
 BAC3
 Coiling vs BAC4
 Coiling vs SAC2
 Onyx embolization2
 Coiling vs flow diverter1
 Coiling vs BAC vs SAC vs stenting1
 pCONus implant1
Microsurgical clipping2
Endovascular/microsurgical4
 Primary coiling & clipping3
 BAC & clipping1

The results of our search for a definition of WNA were consolidated to avoid duplication because the threshold value was not included in all the studies that we examined. We identified 27 unique definitions for WNA that we ultimately condensed into 14 definitions, which are summarized in Table 1. The most common WNA definition was a neck size ≥ 4 mm or dome-to-neck ratio < 2, which was used in 49 (39.8%) of the 123 articles. The second most commonly used definition was neck size ≥ 4 mm, which was used in 26 studies (21.1%). A dome-to-neck ratio was used in 90 studies, and a neck-to-dome ratio was used in 6 studies. Dome-to-neck ratios used for the definition ranged from 1 to < 2 (1, 1.2, 1.5, 1.6, 1.8, and < 2).

Our review determined that the methods used for the evaluation of aneurysm geometrical shape included digital subtraction angiography (DSA), CT angiography (CTA), MR angiography (MRA), and intraoperative observation (Table 2). The most commonly used singular imaging modality was DSA in 87 of 122 studies (71.3%). However, almost all studies (120 of 122, 98.4%) included DSA as an imaging modality, whereas only 1 study each used MRA13 or CTA30 alone. Three-dimensional rotational angiography (3DRA) was also reported in 69 studies (57.5%) and 2D DSA alone was reported in 51 studies (42.5%).

Discussion

Main Findings

This is the first systematic review to assess the most common definition of a WNA. We found a lack of consistency in the neurosurgical literature with regard to the definition of a WNA. The most frequently used definition of a WNA was a neck size of ≥ 4 mm or dome-to-neck ratio of < 2, seen in 49 studies (39.8%). The second most common definition was an absolute neck size of ≥ 4 mm, seen in 26 studies (21.1%); this criterion is included in some way in defining WNAs in 105 of the 123 studies. The WNA definitions using a dome-to-neck ratio varied substantially. Multiple different dome-to-neck thresholds have been suggested. Additionally, several different aneurysm geometrical ratios can be determined: height-to-neck ratio, width-to-neck ratio, and maximum dome diameter–to-neck ratio, all of which were rarely defined in the studies we analyzed. To complicate matters, we found that the height-to-neck ratio is sometimes referred to as the aspect ratio, and the width-to-neck ratio is sometimes referred to as the bottleneck factor.10 The most commonly used dome-to-neck ratio was < 2, which was included in 57 studies (46.3%). Overall, a dome-to-neck ratio in the WNA definition was used in 90 studies (73.2%). There is clearly some variability in the use and reporting of dome-to-neck ratios, which highlights the importance of the need for a unified definition.

It is unclear whether the addition of the dome-to-neck ratio to the absolute value of the neck width is clinically relevant. This measurement is most relevant in the endovascular treatment of a small aneurysm with a neck width that is approximately the same size as the aneurysm dome diameter (a dome-to-neck ratio of 1). In such cases, the aneurysm neck is not close to 4 mm, although adjunctive techniques are usually needed because it is still difficult to prevent coil prolapse from the aneurysm. Interestingly, in a review of 185 patients whose aneurysms were selected for embolization, Brinjikji et al.4 demonstrated that 75% of aneurysms with dome-to-neck ratios > 1.6 and height-to-neck ratios > 1.6 did not require adjunctive techniques, whereas 80% of aneurysms with dome-to-neck ratios < 1.2 and 89% of aneurysms with height-to-neck ratios < 1.2 required adjunctive techniques. Multivariate analysis indicated that the height-to-neck ratio was the most important factor in predicting the need for an adjunctive device. Thus, some measure of the dome-to-neck ratio should likely be a part of the WNA definition. Further research is needed to determine the best measurement and the most precise threshold.

The modality used to measure aneurysm geometrics was not consistent across the studies analyzed. In the studies we reviewed, CTA, MRA, 2D DSA, and 3DRA were used to differing degrees to measure the aneurysms. DSA was the dominant imaging modality and was used in 120 (98.4%) of 122 studies that included imaging modalities. Of these 120 studies, 69 (57.5%) also used 3DRA. DSA alone was used in 87 (71.3%) of 122 studies. This finding is important because the modality of measurement impacts the aneurysm dimensions. Brinjikji et al.3 compared 2D DSA and 3DRA specifically for measuring dome-to-neck ratios in 180 patients with 205 aneurysms. They demonstrated a statistically significant (p < 0.0001) inconsistency in dome-to-neck ratio measurements between 2D DSA and 3DRA. The 3DRA studies provided an overall higher mean dome-to-neck ratio. Therefore, the authors considered 3DRA not as accurate as 2D DSA in identifying aneurysms as wide necked, presumably because of a postprocessing error. This study indicates that 2D DSA may be superior to 3DRA for measuring WNAs.

We attempted to provide a comprehensive evaluation of the existing literature discussing the definition of a WNA; however, this study possesses innate selection bias as a result of the 30-patient sample size requirement. The study also did not provide any indication of the importance or impact of any single literature article and therefore may bias the results toward the definition that achieved more importance by frequency of adoption alone.

Geometrical Analysis

The most prevalent geometrical criteria for the definition of a WNA include neck diameter, dome-to-neck ratio, and aspect ratio. To ensure consistency within the neurosurgical literature regarding these topics, we must accurately define each of these entities. Dome diameter, dome height, and neck width are frequently used measurements.10,18 Neck width, also referred to as neck diameter, is defined as the maximal aneurysm neck width measured in millimeters (Fig. 2A).8,10,18 The measurement of neck width originally defined a WNA, and this measurement has a consistent geometrical definition in the neurosurgical literature.4,5,8,19,20,22,28

FIG. 2.
FIG. 2.

A: The most frequent component of a WNA definition in the neurosurgical literature is neck width (N) ≥ 4 mm. B: The dome-to-neck (DTN) ratio of a WNA (most commonly < 2) is the maximal dome diameter (either dome width [W] or dome height [H]) relative to the neck width (N). C: Aneurysms can meet both geometrical definitions if they possess a neck width (N) ≥ 4 mm and a DTN ratio < 2. Copyright Barrow Neurological Institute. Published with permission. Figure is available in color online only.

The dome-to-neck ratio is most commonly defined as the maximal aneurysm dome width–to-neck diameter,18 as originally proposed in 1998.7 Although commonly referred to in the neurosurgical literature, this feature is seldom precisely defined. Figure 2B demonstrates the dome-to-neck ratio and illustrates the most commonly used ratio of < 2. The height-to-neck ratio is not as thoroughly explored in published reports. However, it does have demonstrated importance during the planning of endovascular therapy (EVT).4 Originally introduced in 1999 as a geometrical feature relevant to the definition of WNAs, this aspect ratio was defined as the aneurysm depth, also referred to as its height, divided by the neck width of the aneurysm.29 This definition has been maintained throughout the neurosurgical literature whenever the term has been defined.4,10 Figure 2C demonstrates an aneurysm that meets both the neck diameter and the dome-to-neck ratio criteria for identifying a WNA. Finally, the aneurysm dome-to-neck ratio has infrequently been referred to as the bottleneck factor.10

Treatment of WNAs

WNAs are more difficult to treat than narrow-necked aneurysms. In the case of microsurgical clipping, a wide aneurysm neck may obscure perforator anatomy, may make clip placement more difficult, and may require a more complex clip construction, such as multiple clip techniques and tandem clipping. In the case of EVT, coils may prolapse from the aneurysm into the parent vessel, which can lead to thromboembolic complications. Several EVT techniques have been developed to address WNAs, including BAC, SAC, flow diversion (FD), intrasaccular devices, and complex aneurysm neck–support devices.

Although only a few studies have examined the results of microsurgical clipping of WNAs, numerous studies have examined their endovascular treatment. These series have demonstrated that EVT of WNAs is efficacious when augmented by advanced endovascular techniques. BAC, in which a balloon is temporarily inflated in the parent artery during coiling, has been used the longest for the treatment of WNAs. A review of nearly 5000 patients demonstrated that BAC has a similar safety profile to that of stand-alone coiling, while providing better initial and follow-up aneurysm occlusion rates.25 However, this conclusion is debatable, as some authors have suggested a higher complication rate with BAC than with conventional coiling.26 In SAC, a stent is placed in the parent artery to permanently act as a scaffold for the coils within the aneurysm. In a meta-analysis of 2566 patients, in comparison with stand-alone coiling, SAC was demonstrated to have a lower initial aneurysm occlusion rate (57.6% vs 68.7%) but also a lower recurrence rate (16.2% vs 34.4%), as well as a higher progressive thrombosis rate (37.5% vs 19.4%).11 A systematic review of SAC demonstrated similar results: a 71.9% complete occlusion rate at the last follow-up, a 13.2% recanalization rate, and a 5.3% risk of delayed in-stent thrombosis.16 In 2017, Fiorella et al.9 performed a review of more than 5000 patients with wide-necked bifurcation aneurysms and found higher rates of complete and adequate aneurysm occlusion when surgical clipping was used versus conventional ETV techniques (stand-alone coiling, BAC, and SAC), but they also found higher rates of complications. In the case of ruptured aneurysms, the safety profile of BAC appears to be similar to that of stand-alone coiling,20 but the safety profile of SAC may be worse because of the use of dual antiplatelet therapy.24 There are minimal data comparing surgical clipping to EVT for ruptured WNAs.

In FD, a stent with higher metal coverage of the aneurysm neck is placed in the parent artery, with or without adjunctive aneurysm coiling. FD followed SAC as the next major form of EVT for WNAs. The Pipeline embolization device (PED) has received US Food and Drug Administration approval for the treatment of WNAs of the internal carotid artery from the petrous to the superior hypophyseal segments,1 and it has been used off-label in other areas of the brain. A meta-analysis of 10 studies using the PED in 414 patients demonstrated, at 6 months, an 82.9% occlusion rate, a 6.3% intracranial vascular complication rate, and a 1.5% mortality rate.12 The Flow Diversion in Intracranial Aneurysm Treatment trial was terminated prematurely in 2015 upon meeting a predefined safety boundary based on clinical outcomes.23 Multiple additional studies are currently underway, and further prospective study is necessary to determine the role of FD in WNA treatment. However, FD is not without complications, as shown by a recent systematic review that demonstrated an overall complication rate of 17%, with increased complications in patients with subarachnoid hemorrhage.31 The most recent endovascular devices developed in the United States include the Woven EndoBridge (WEB) (Sequent Medical), which is an intrasaccular device, and novel aneurysm neck–support devices such as the PulseRider (Pulsar Vascular, Inc.). Additional devices with a less established clinical role and neurosurgical literature presence include the Medina Embolization Device (Medtronic plc),27 the Barrel vascular reconstruction device (Medtronic plc),17 the pCONus Bifurcation Aneurysm Implant (phenox, GmbH), the eCLIPs device (Evasc Neurovascular Enterprises),14 and the Luna Aneurysm Embolization System (Nfocus Neuromedical, Inc.).

Numerous studies have examined the use of the WEB device for wide-necked bifurcation aneurysms, with complete aneurysm occlusion reported in 79%–94% of patients, but follow-up has been limited.2,5,22 Complication rates associated with the use of the WEB device ranged from 11% to 34% in a systematic review of 4 studies, and these most commonly involved thromboembolic events (7%–18% incidence).2 Device-related problems during deployment and intraoperative rupture (< 2%) were described but rarely encountered.2 The PulseRider device is an aneurysm neck–supporting device that is placed in the parent artery of a bifurcation aneurysm. In a small prospective series of 34 patients, the Raymond I or II aneurysm occlusion rate was 82.4%, initially progressing to 87.9% at 6 months.28 However, the overall neurosurgical literature lacks long-term outcome data for this device. The intraprocedural complication rate in this series was 8.8% (3 cases), with 1 case of intraprocedural rupture, 1 case of thrombus formation, and 1 case of femoral vessel dissection, none of which resulted in a negative outcome. Postprocedural neurosurgical complications were limited to 6 patients and included 1 case of aneurysm recurrence, with symptomatic mass effect, and 2 cases of ischemic sequelae (5.8%).28 Therefore, these recent EVT developments provide promising results overall regarding efficacy and safety, although additional prospective study is required to determine long-term utility.

The systematic analysis of the literature for WNAs included a specific analysis of treatment modalities reported within each study, summarized in Table 3. The results reflected the overall predominance of use for the WNA phraseology within the endovascular literature and the sparse adoption within the open cerebrovascular literature. The majority of endovascular publications were in the setting of SAC (55 of 117; 47%). This is likely due to this being a well-established strategy for the treatment of WNAs, whereas devices such as the WEB and FD are growing topics of research and clinical outcome analysis.

Implications of the Lack of a Standard WNA Definition

The incidence of WNA is highly dependent on subtle changes in the definition, as exemplified by Pierot et al.,20 who studied 768 patients with ruptured aneurysms, of which 114 (14.8%) were classified as WNAs based on neck size alone. When the dome-to-neck ratio alone is used to define a WNA, the incidence ranges from 33.7% to 84.4%, depending on the dome-to-neck ratio (1.5 vs 2) and on the imaging modality used for analysis.3 However, a post hoc analysis of data from the Barrow Ruptured Aneurysm Trial indicates that WNAs, as defined by a neck size ≥ 4 mm and a dome-to-neck ratio < 2, results in a 54.1% incidence of WNAs.15 The implications of this finding highlight the need for a universal definition.

Conclusions

This is the first systematic review to analyze the definitions of WNA, which are highly variable. The most prevalent definition of a WNA is a neck diameter of ≥ 4 mm or a dome-to-neck ratio of < 2. Whether this definition is the most appropriate definition is a topic of discussion and future research. The use of a standard definition would be beneficial when comparing various WNA studies.

Acknowledgments

We thank the staff of Neuroscience Publications at Barrow Neurological Institute for assistance with manuscript preparation.

Disclosures

Dr. Kellner has an educational grant from Penumbra, Inc; he has research support from Siemens Corp. Dr. Ducruet is a consultant and Pipeline proctor for Medtronic. Dr. Mascitelli has received funding from The Bee Foundation for wide-neck aneurysm research, which is unrelated to this review article. Dr. Mocco is a consultant for Rebound Medical, LLC, EndoStream Medical, Ltd., Synchron, Inc., and Cerebrotech Medical Systems, Inc.; he is also an investor in, or possesses ownership in, Apama Medical, Inc., Stroke Project, Inc., EndoStream Medical, Ltd., Synchron, Inc., Cerebrotech Medical Systems, Inc., NeurVana Medical, LLC, and NeuroTechnology Investors, LLC.

Author Contributions

Conception and design: Mascitelli, Hendricks. Acquisition of data: Hendricks, Yoon. Analysis and interpretation of data: Mascitelli, Hendricks, Yoon. Drafting the article: Mascitelli, Hendricks. Critically revising the article: Mascitelli, Hendricks, Yaeger, Kellner, Mocco, De Leacy, Ducruet, Lawton. Reviewed submitted version of manuscript: all authors. Administrative/technical/material support: Hendricks. Study supervision: Mascitelli.

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    Mühl-Benninghaus R, Simgen A, Reith W, Yilmaz U: The Barrel stent: new treatment option for stent-assisted coiling of wide-necked bifurcation aneurysms—results of a single-center study. J Neurointerv Surg 9:12191222, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Parlea L, Fahrig R, Holdsworth DW, Lownie SP: An analysis of the geometry of saccular intracranial aneurysms. AJNR Am J Neuroradiol 20:10791089, 1999

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Peterson E, Hanak B, Morton R, Osbun JW, Levitt MR, Kim LJ: Are aneurysms treated with balloon-assisted coiling and stent-assisted coiling different? Morphological analysis of 113 unruptured wide-necked aneurysms treated with adjunctive devices. Neurosurgery 75:145151, 2014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Pierot L, Cognard C, Anxionnat R, Ricolfi F: Remodeling technique for endovascular treatment of ruptured intracranial aneurysms had a higher rate of adequate postoperative occlusion than did conventional coil embolization with comparable safety. Radiology 258:546553, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21

    Pierot L, Cognard C, Spelle L, Moret J: Safety and efficacy of balloon remodeling technique during endovascular treatment of intracranial aneurysms: critical review of the literature. AJNR Am J Neuroradiol 33:1215, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22

    Pierot L, Moret J, Turjman F, Herbreteau D, Raoult H, Barreau X, et al.: WEB treatment of intracranial aneurysms: clinical and anatomic results in the French Observatory. AJNR Am J Neuroradiol 37:655659, 2016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    Raymond J, Gentric JC, Darsaut TE, Iancu D, Chagnon M, Weill A, et al.: Flow diversion in the treatment of aneurysms: a randomized care trial and registry. J Neurosurg 127:454462, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Ryu CW, Park S, Shin HS, Koh JS: Complications in stent-assisted endovascular therapy of ruptured intracranial aneurysms and relevance to antiplatelet administration: a systematic review. AJNR Am J Neuroradiol 36:16821688, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 25

    Shapiro M, Babb J, Becske T, Nelson PK: Safety and efficacy of adjunctive balloon remodeling during endovascular treatment of intracranial aneurysms: a literature review. AJNR Am J Neuroradiol 29:17771781, 2008

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 26

    Sluzewski M, van Rooij WJ, Beute GN, Nijssen PC: Balloon-assisted coil embolization of intracranial aneurysms: incidence, complications, and angiography results. J Neurosurg 105:396399, 2006

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27

    Sourour NA, Vande Perre S, Maria FD, Papagiannaki C, Gabrieli J, Pistocchi S, et al.: Medina® embolization device for the treatment of intracranial aneurysms: safety and angiographic effectiveness at 6 months. Neurosurgery 82:155162, 2018

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 28

    Spiotta AM, Derdeyn CP, Tateshima S, Mocco J, Crowley RW, Liu KC, et al.: Results of the ANSWER trial using the PulseRider for the treatment of broad-necked, bifurcation aneurysms. Neurosurgery 81:5665, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29

    Ujiie H, Tachibana H, Hiramatsu O, Hazel AL, Matsumoto T, Ogasawara Y, et al.: Effects of size and shape (aspect ratio) on the hemodynamics of saccular aneurysms: a possible index for surgical treatment of intracranial aneurysms. Neurosurgery 45:119130, 1999

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 30

    Zenteno M, Modenesi Freitas JM, Aburto-Murrieta Y, Koppe G, Machado E, Lee A: Balloon-expandable stenting with and without coiling for wide-neck and complex aneurysms. Surg Neurol 66:603610, 2006

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 31

    Zhou G, Su M, Yin YL, Li MH: Complications associated with the use of flow-diverting devices for cerebral aneurysms: a systematic review and meta-analysis. Neurosurg Focus 42(6):E17, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • Collapse
  • Expand

Diagram from Kondziolka et al. (pp 1–2).

  • FIG. 1.

    Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flowchart presenting an overview of the systematic review. Figure is available in color online only.

  • FIG. 2.

    A: The most frequent component of a WNA definition in the neurosurgical literature is neck width (N) ≥ 4 mm. B: The dome-to-neck (DTN) ratio of a WNA (most commonly < 2) is the maximal dome diameter (either dome width [W] or dome height [H]) relative to the neck width (N). C: Aneurysms can meet both geometrical definitions if they possess a neck width (N) ≥ 4 mm and a DTN ratio < 2. Copyright Barrow Neurological Institute. Published with permission. Figure is available in color online only.

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    Alderazi YJ, Shastri D, Kass-Hout T, Prestigiacomo CJ, Gandhi CD: Flow diverters for intracranial aneurysms. Stroke Res Treat 2014:415653, 2014

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    Armoiry X, Turjman F, Hartmann DJ, Sivan-Hoffmann R, Riva R, Labeyrie PE, et al.: Endovascular treatment of intracranial aneurysms with the WEB device: a systematic review of clinical outcomes. AJNR Am J Neuroradiol 37:868872, 2016

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  • 3

    Brinjikji W, Cloft H, Lanzino G, Kallmes DF: Comparison of 2D digital subtraction angiography and 3D rotational angiography in the evaluation of dome-to-neck ratio. AJNR Am J Neuroradiol 30:831834, 2009

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  • 4

    Brinjikji W, Cloft HJ, Kallmes DF: Difficult aneurysms for endovascular treatment: overwide or undertall? AJNR Am J Neuroradiol 30:15131517, 2009

  • 5

    Clajus C, Strasilla C, Fiebig T, Sychra V, Fiorella D, Klisch J: Initial and mid-term results from 108 consecutive patients with cerebral aneurysms treated with the WEB device. J Neurointerv Surg 9:411417, 2017

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    Cloft HJ, Joseph GJ, Tong FC, Goldstein JH, Dion JE: Use of three-dimensional Guglielmi detachable coils in the treatment of wide-necked cerebral aneurysms. AJNR Am J Neuroradiol 21:13121314, 2000

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  • 7

    Debrun GM, Aletich VA, Kehrli P, Misra M, Ausman JI, Charbel F: Selection of cerebral aneurysms for treatment using Guglielmi detachable coils: the preliminary University of Illinois at Chicago experience. Neurosurgery 43:12811297, 1998

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    Fernandez Zubillaga A, Guglielmi G, Viñuela F, Duckwiler GR: Endovascular occlusion of intracranial aneurysms with electrically detachable coils: correlation of aneurysm neck size and treatment results. AJNR Am J Neuroradiol 15:815820, 1994

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  • 9

    Fiorella D, Arthur AS, Chiacchierini R, Emery E, Molyneux A, Pierot L: How safe and effective are existing treatments for wide-necked bifurcation aneurysms? Literature-based objective performance criteria for safety and effectiveness. J Neurointerv Surg 9:11971201, 2017

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  • 10

    Hoh BL, Sistrom CL, Firment CS, Fautheree GL, Velat GJ, Whiting JH, et al.: Bottleneck factor and height-width ratio: association with ruptured aneurysms in patients with multiple cerebral aneurysms. Neurosurgery 61:716723, 2007

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  • 11

    Hong Y, Wang YJ, Deng Z, Wu Q, Zhang JM: Stent-assisted coiling versus coiling in treatment of intracranial aneurysm: a systematic review and meta-analysis. PLoS One 9:e82311, 2014

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  • 12

    Leung GK, Tsang AC, Lui WM: Pipeline embolization device for intracranial aneurysm: a systematic review. Clin Neuroradiol 22:295303, 2012

  • 13

    Li M, Zhu Y, Song H, Gu B, Lu H, Li Y, et al.: Subarachnoid hemorrhage in patients with good clinical grade: accuracy of 3.0-T MR angiography for detection and characterization. Radiology 284:191199, 2017

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  • 14

    Marotta TR, Riina HA, McDougall I, Ricci DR, Killer-Oberpfalzer M: Physiological remodeling of bifurcation aneurysms: preclinical results of the eCLIPs device. J Neurosurg 128:475481, 2018

    • Crossref
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  • 15

    Mascitelli JR, Lawton MT, Hendricks BK, Nakaji P, Zabramski JM, Spetzler RF: Analysis of wide-neck aneurysms in the Barrow Ruptured Aneurysm Trial. Neurosurgery [epub ahead of print], 2018

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  • 16

    McLaughlin N, McArthur DL, Martin NA: Use of stent-assisted coil embolization for the treatment of wide-necked aneurysms: a systematic review. Surg Neurol Int 4:43, 2013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17

    Mühl-Benninghaus R, Simgen A, Reith W, Yilmaz U: The Barrel stent: new treatment option for stent-assisted coiling of wide-necked bifurcation aneurysms—results of a single-center study. J Neurointerv Surg 9:12191222, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Parlea L, Fahrig R, Holdsworth DW, Lownie SP: An analysis of the geometry of saccular intracranial aneurysms. AJNR Am J Neuroradiol 20:10791089, 1999

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Peterson E, Hanak B, Morton R, Osbun JW, Levitt MR, Kim LJ: Are aneurysms treated with balloon-assisted coiling and stent-assisted coiling different? Morphological analysis of 113 unruptured wide-necked aneurysms treated with adjunctive devices. Neurosurgery 75:145151, 2014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Pierot L, Cognard C, Anxionnat R, Ricolfi F: Remodeling technique for endovascular treatment of ruptured intracranial aneurysms had a higher rate of adequate postoperative occlusion than did conventional coil embolization with comparable safety. Radiology 258:546553, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21

    Pierot L, Cognard C, Spelle L, Moret J: Safety and efficacy of balloon remodeling technique during endovascular treatment of intracranial aneurysms: critical review of the literature. AJNR Am J Neuroradiol 33:1215, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22

    Pierot L, Moret J, Turjman F, Herbreteau D, Raoult H, Barreau X, et al.: WEB treatment of intracranial aneurysms: clinical and anatomic results in the French Observatory. AJNR Am J Neuroradiol 37:655659, 2016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    Raymond J, Gentric JC, Darsaut TE, Iancu D, Chagnon M, Weill A, et al.: Flow diversion in the treatment of aneurysms: a randomized care trial and registry. J Neurosurg 127:454462, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Ryu CW, Park S, Shin HS, Koh JS: Complications in stent-assisted endovascular therapy of ruptured intracranial aneurysms and relevance to antiplatelet administration: a systematic review. AJNR Am J Neuroradiol 36:16821688, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 25

    Shapiro M, Babb J, Becske T, Nelson PK: Safety and efficacy of adjunctive balloon remodeling during endovascular treatment of intracranial aneurysms: a literature review. AJNR Am J Neuroradiol 29:17771781, 2008

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 26

    Sluzewski M, van Rooij WJ, Beute GN, Nijssen PC: Balloon-assisted coil embolization of intracranial aneurysms: incidence, complications, and angiography results. J Neurosurg 105:396399, 2006

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27

    Sourour NA, Vande Perre S, Maria FD, Papagiannaki C, Gabrieli J, Pistocchi S, et al.: Medina® embolization device for the treatment of intracranial aneurysms: safety and angiographic effectiveness at 6 months. Neurosurgery 82:155162, 2018

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 28

    Spiotta AM, Derdeyn CP, Tateshima S, Mocco J, Crowley RW, Liu KC, et al.: Results of the ANSWER trial using the PulseRider for the treatment of broad-necked, bifurcation aneurysms. Neurosurgery 81:5665, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29

    Ujiie H, Tachibana H, Hiramatsu O, Hazel AL, Matsumoto T, Ogasawara Y, et al.: Effects of size and shape (aspect ratio) on the hemodynamics of saccular aneurysms: a possible index for surgical treatment of intracranial aneurysms. Neurosurgery 45:119130, 1999

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 30

    Zenteno M, Modenesi Freitas JM, Aburto-Murrieta Y, Koppe G, Machado E, Lee A: Balloon-expandable stenting with and without coiling for wide-neck and complex aneurysms. Surg Neurol 66:603610, 2006

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 31

    Zhou G, Su M, Yin YL, Li MH: Complications associated with the use of flow-diverting devices for cerebral aneurysms: a systematic review and meta-analysis. Neurosurg Focus 42(6):E17, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

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