Aneurysms with persistent patency after treatment with the Pipeline Embolization Device

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  • 1 Department of Neurosurgery, Baylor College of Medicine, Houston, Texas;
  • | 2 Department of Neurosurgery, Mayo Clinic, Jacksonville, Florida;
  • | 3 Department of Neurosurgery, UT Southwestern, Dallas, Texas;
  • | 4 Department of Neurosurgery, University of South Florida, Tampa, Florida;
  • | 5 Drexel Neuroscience Institute, Philadelphia, Pennsylvania;
  • | 6 Capital Institute for Neurosciences, Trenton, New Jersey; and
  • | 7 Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts
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The Pipeline Embolization Device (PED) was approved for the treatment of intracranial aneurysms from the petrous to the superior hypophyseal segment of the internal carotid artery. However, since its approval, its use for treatment of intracranial aneurysms in other locations and non-sidewall aneurysms has grown tremendously. The authors report on a cohort of 15 patients with 16 cerebral aneurysms that incorporated an end vessel with no significant distal collaterals, which were treated with the PED. The cohort includes 7 posterior communicating artery aneurysms, 5 ophthalmic artery aneurysms, 1 superior cerebellar artery aneurysm, 1 anterior inferior cerebellar artery aneurysm, and 2 middle cerebral artery aneurysms. None of the aneurysms achieved significant occlusion at the last follow-up evaluation (mean 24 months). Based on these observations, the authors do not recommend the use of flow diverters for the treatment of this subset of cerebral aneurysms.

ABBREVIATIONS

AICA = anterior inferior cerebellar artery; MCA = middle cerebral artery; OphA = ophthalmic artery; PCA = posterior cerebral artery; PCoA = posterior communicating artery; PED = Pipeline Embolization Device; PICA = posterior inferior cerebellar artery; PTA = percutaneous transluminal balloon angioplasty; SCA = superior cerebellar artery.

The Pipeline Embolization Device (PED) was approved for the treatment of intracranial aneurysms from the petrous to the superior hypophyseal segment of the internal carotid artery. However, since its approval, its use for treatment of intracranial aneurysms in other locations and non-sidewall aneurysms has grown tremendously. The authors report on a cohort of 15 patients with 16 cerebral aneurysms that incorporated an end vessel with no significant distal collaterals, which were treated with the PED. The cohort includes 7 posterior communicating artery aneurysms, 5 ophthalmic artery aneurysms, 1 superior cerebellar artery aneurysm, 1 anterior inferior cerebellar artery aneurysm, and 2 middle cerebral artery aneurysms. None of the aneurysms achieved significant occlusion at the last follow-up evaluation (mean 24 months). Based on these observations, the authors do not recommend the use of flow diverters for the treatment of this subset of cerebral aneurysms.

ABBREVIATIONS

AICA = anterior inferior cerebellar artery; MCA = middle cerebral artery; OphA = ophthalmic artery; PCA = posterior cerebral artery; PCoA = posterior communicating artery; PED = Pipeline Embolization Device; PICA = posterior inferior cerebellar artery; PTA = percutaneous transluminal balloon angioplasty; SCA = superior cerebellar artery.

The Pipeline Embolization Device (PED; ev3) was approved by the US FDA for the treatment of intracranial aneurysms from the petrous to the superior hypophyseal segment of the internal carotid artery. However, since its approval in 2011, its use for the treatment of intracranial aneurysms in other locations and non-sidewall aneurysms has grown tremendously. The use of the PED in the treatment of aneurysms beyond its original indications is common and has been well reported in several large, multicenter registries with good results.1,3,6 However, the above studies did not focus on cases in which aneurysm occlusion was not achieved. Although the potential uses for flow diversion are broad, important exceptions to its use may exist. In this study, we report the outcomes of 15 patients with 16 cerebral aneurysms that incorporated an end vessel at the aneurysm neck or dome, which were treated by flow diversion using the PED.

Methods

Study Population

Institutional databases at each participating center were searched for cerebral aneurysms associated with end vessels treated with the PED. The clinical data and angiographic images for all patients were retrospectively reviewed. We report the outcomes of 15 patients who underwent treatment with the PED for 16 cerebral aneurysms that incorporated an end vessel (Table 1). Each patient had a minimum of 12 months of angiographic follow-up after treatment. Patients with prior or adjunct treatment of the study aneurysm (coil embolization or clip placement) were included in the study. In this study, an end vessel was defined as a vessel with no significant distal collaterals, such as the ophthalmic artery (OphA) with no external carotid artery supply, fetal posterior cerebral artery (PCA), anterior choroidal artery, middle cerebral artery (MCA), anterior cerebral artery distal to A1, dominant superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), posterior inferior cerebellar artery (PICA), and PCA distal to P1. For OphA aneurysms, a balloon test occlusion was performed across the ostium of the OphA and the neck of the aneurysm. If patients became symptomatic during the balloon test occlusion, the OphA was determined to be an end vessel. DynaCT was performed after each PED placement to ensure good wall apposition. Suboptimal vessel apposition was treated with percutaneous transluminal balloon angioplasty (PTA). The study was approved by the local institutional review board of each participating institution (Baylor College of Medicine, UT Southwestern, University of South Florida, Mayo Clinic, Drexel, and University of Massachusetts).

TABLE 1.

Overview of patients and aneurysms with PED treatment failure

Case No.Age (yrs)Artery LocationAneurysm Size (mm)Neck Size (mm)End VesselCoiling (Y/N)PED Size (mm)PTAFU (mos)
1a71Rt PCoA7 × 118Rt fetal PCANo5 × 25 & 5 × 20No18
1bRt MCA7 × 55Rt M2No3.5 × 14No18
252Lt SCA4 × 33Lt SCANo3.25 × 14No24
331Rt OphA4 × 3.53.5Rt OphANo4 × 14No48
474Lt PCoA9 × 7*6Lt PCoAYes, prior to SAH3.75 × 20No36
572Lt PCoATri-lobed4Lt PCoAYes, same setting4 × 12 (2)No18
668Rt PCoA7 × 54.5 × 14Rt PCoAYes, same setting4.5 × 14No18
754Rt AICA6 × 54Rt AICANo3.5 × 14No24
852Rt PCoA15 × 154 × 25Rt PCoAYes4 × 25Yes12
950Rt OphA4.1Rt OphANo3.75 × 14No12
1078Rt MCA8 × 76Rt M2No3.25 × 20No12
1155Lt OphA4.5 × 4Lt OphANo5 × 20No48
1253Rt OphA4.5 × 4Rt OphAYes4.5 × 14No37
1343Rt PCoA3.5 × 2.52.5Rt PCoAYes4 × 14No12
1465Lt PCoA5 × 4Lt fetal PCANo4.5 × 14No30
1544Lt OphA3 × 5 × 45Lt OphAPreviously clipped3.5 × 20Yes13

FU = follow-up; M2 = second segment of the MCA; SAH = subarachnoid hemorrhage.

All patients were female. All had Raymond scale scores of 3 (no occlusion) and Szikora scale scores of 0 (no stasis of flow after flow diverter placement4,10). Only Cases 9 and 14 underwent clip placement after PED treatment.

Residual aneurysm from prior attempted coil embolization.

Sizes: 3.6 × 2.4 mm, 4 × 4 × 7 mm, and 2.4 mm, originating from the PCoA.

Only dimension available for this aneurysm.

Treatment Procedures

All patients were treated with dual antiplatelet therapy consisting of 81 mg or 325 mg of aspirin daily and 75 mg of clopidogrel daily for 7 days prior to the procedure. The degree of P2Y12 receptor inhibition and aspirin response was tested with VerifyNow (Accumetrics) on the day of treatment. An aspirin P2Y12 response unit value ≤ 550 and a clopidogrel response unit value ≤ 220 were considered indicative of an appropriate level of platelet inhibition for treatment. All procedures were performed under general anesthesia. Systemic heparin was used to achieve an activated clotting time of ≥ 250 seconds. To ensure robust proximal support, a triaxial system was used through femoral access in each case. This consisted of a 6-Fr shuttle sheath (Cook Medical) placed in the common carotid artery prior to the bifurcation; a 5-Fr Navien distal access catheter (Covidien Vascular Therapies) placed proximal to the aneurysm; and the delivery microcatheter for the PED.

Results

Across all institutions, 701 PEDs were placed for cerebral aneurysms. We identified 16 aneurysms from 15 patients that fulfilled the study criteria (Table 1). The cohort included 7 posterior communicating artery (PCoA) aneurysms, 5 OphA aneurysms, 1 SCA aneurysm, 1 AICA aneurysm, and 2 MCA aneurysms. All patients were female and had a mean age of 57.5 years (range 31–78 years). Aneurysms were all of a saccular morphology and ranged from 3.5 × 2.5 mm to 15 × 15 mm. PTA was performed in 2 patients (13.3%). All 16 aneurysms remained patent (Raymond scale score of 3) with minimal change in size and shape at last follow-up compared with the pretreatment angiogram. The change in dome size was < 25% in all aneurysms. The mean follow-up was 24 months (range 12–48 months). There was no in-stent stenosis in the cohort. The patient in Case 9 has undergone surgical clipping of her right OphA aneurysm and Case 14 also underwent surgical clipping of her left PCoA aneurysm. The remaining patients are under further conservative surveillance.

Illustrative Cases

Fetal PCA and MCA Aneurysms (Case 1)

A 71-year-old patient presented with 2 aneurysms: a large, unruptured, right fetal PCoA aneurysm along with a wide-necked right MCA aneurysm (Fig. 1A–C). The PCoA aneurysm measured 7 × 11 mm with an 8-mm neck and incorporated the origin of the right fetal PCA. The MCA bifurcation aneurysm measured 7 × 5 mm with a 5-mm neck and incorporated the superior division of the MCA (M2). The MCA aneurysm was treated with a 3.5 × 14–mm PED, and the fetal PCoA aneurysm was treated with 2 overlapping PEDs (5 × 25 mm followed by 5 × 20 mm) in the same setting. The posttreatment DynaCT scan showed good device apposition. The follow-up angiogram at 18 months demonstrated persistent filling into both aneurysms with little change. The fetal PCA and superior MCA division remained patent (Fig. 1D).

FIG. 1.
FIG. 1.

A–C: Cerebral angiogram (anteroposterior [A], lateral [B], and 3D reconstruction [C] views) of the right internal carotid artery showing a large, unruptured, right fetal PCoA aneurysm and a right MCA aneurysm. D: Follow-up cerebral angiogram at 18 months after PED treatment showing persistent filling of both aneurysms and patency of both end vessels. Figure is available in color online only.

SCA Aneurysm (Case 2)

A 52-year-old patient presented with an unruptured, wide-necked left SCA aneurysm measuring 4 × 3 mm with a 3-mm neck involving the origin of the left SCA (Fig. 2A–C). The aneurysm was treated with a 3.25 × 14–mm PED. The posttreatment DynaCT scan showed good device apposition to the walls. The follow-up angiogram at 24 months demonstrated persistent filling of the aneurysm with no significant change, and patency of the left SCA (Fig. 2D).

FIG. 2.
FIG. 2.

A–C: Cerebral angiogram (anteroposterior [A], lateral [B], and 3D reconstruction [C] views) of the left VA injection showing an unruptured left SCA aneurysm. D: Follow-up cerebral angiogram at 24 months showing persistent filling of the aneurysm and robust flow through the left SCA. Figure is available in color online only.

AICA Aneurysm (Case 7)

A 54-year-old patient presented with an unruptured, wide-necked right AICA aneurysm measuring 6 × 5 mm with a 4-mm neck incorporating the origin of the right AICA. The aneurysm was treated with a 3.5 × 14–mm PED at an outside facility. Reportedly, the posttreatment DynaCT scan showed good device apposition and no posttreatment angioplasty was performed. The follow-up angiogram at 24 months demonstrated persistent filling of the entire aneurysm and patency of the right AICA (Fig. 3).

FIG. 3.
FIG. 3.

Cerebral angiogram (anteroposterior view [left] and magnified anteroposterior view [right]) of left vertebral artery injection showing a right AICA aneurysm at 24 months after PED treatment with persistent filling.

OphA Aneurysm (Case 3)

A 31-year-old patient had an incidental right OphA aneurysm that measured 4 × 3.5 mm and involved the origin of the right OphA (Fig. 4A–C). Balloon test occlusion with the balloon placed across the OphA origin prior to initial aneurysm treatment was reported to result in visual loss in the patient's right eye. The aneurysm was treated with a 4 × 14–mm PED and posttreatment DynaCT showed good device apposition. The follow-up angiogram at 48 months showed persistent aneurysm filling and patency of the OphA (Fig. 4D).

FIG. 4.
FIG. 4.

A–C: Cerebral angiogram (anteroposterior [A], lateral [B], and 3D reconstruction [C] views) of the right internal carotid artery injection showing an unruptured right OphA aneurysm. The large OphA originates from the base of the aneurysm. D: Follow-up cerebral angiogram (3D reconstruction of the right ICA injection) at 48 months showing persistent filling of the aneurysm and OphA. Figure is available in color online only.

Discussion

Treatment of cerebral aneurysms that incorporate the origin of end vessels deserves special attention because of a higher treatment risk.13 Occlusion at the ostium in vessels with collaterals will likely be asymptomatic because of collateral supply; however, injury or occlusion of an end vessel with no distal collaterals is more likely to result in strokes and clinical deficits. These aneurysms are traditionally treated with microsurgery to avoid compromise of the end vessel.7 More recently, balloon- and stent-assisted techniques have made treatment safer by reducing the risk of coil herniation into the end vessel lumen. With the advent of flow diversion, the concept of a potential definitive treatment and preservation of the end vessel is attractive. However, our results suggest that flow diversion for aneurysms incorporating end vessels at the neck or dome may be ineffective and may not lead to meaningful aneurysm occlusion.

In this study, an end vessel is defined as a vascular branch with no or poor distal collaterals. In these cases, the aneurysm and end vessel shared a common origin; the vessel arose from either the neck or dome. The distal flow demand on end vessels will likely maintain flow across the ostium after placement of the flow diverter because of the persistent pressure gradient. This differs from vessels with significant distal collaterals that provide competitive flow and neutralize the pressure gradient across the ostium after placement of the flow diverter, leading to potential occlusion of the aneurysm and the vessel.2,5 Therefore, in the presence of distal flow demand, the part of the aneurysm incorporating or close to the origin of the end vessel will remain patent, as observed in all our cases. In fact, the flow through the end vessel and the flow pattern within the aneurysm may remain unchanged. The persistent flow pattern within the aneurysm prevents its thrombosis or collapse even at the dome site after prolonged follow-up as noted in all our cases. Flow diverter treatment can be graded by the traditional Raymond scale, or by a more specific grading scale described by Szikora et al.4,10 According to this scale, all aneurysms in our cohort had Grade 0 occlusion (no change in endoaneurysmal flow) initially after the device placement and at last follow-up.

This concept has been published previously with PCoA aneurysms associated with a fetal PCA as the end vessel, at our institutions and others.9,11 The fetal PCA, an end vessel, has constant anterograde flow to the distal territories and thus the PED does not generate flow stasis in the aneurysm. Conversely, a typical PCoA has competitive flow through the ipsilateral P1 segment, such that the PED can slow the flow through the PCoA or even cause gradual vessel occlusion.12 We believe the same concept can be applied to other end vessels.8 The caliber of the vessel does not appear to matter as long as it is an end vessel with no distal collaterals, because the phenomenon occurs in cerebral vessels of different sizes.

Patients with coils placed either in the same setting or prior to PED placement were also included (Table 1). Of the 16 aneurysms, 6 had coils placed (2 of which were placed during the same setting) and all aneurysms that underwent coil embolization also had treatment failure (Raymond Score 3) at last follow-up. While the coil placement may have provided some dome protection in these cases, it appears to have little effect on the long-term complete occlusion of these aneurysms with flow diversion.

Another reason flow diversion is ineffective in these particular cases is that the neck of the aneurysm (from the proximal aneurysm/parent-vessel interface to the distal aneurysm/end-vessel interface) is not covered by the flow diverter in its entirety, especially at the distal end, thus allowing endoleaks and persistent flow into the aneurysm, preventing its obliteration. All patients in the cohort either had posttreatment DynaCT showing good wall apposition or had PTA, and therefore it is unlikely that a persistent flow between the device and the parent vessel was a contributing factor. There was also no deviation from a routine antiplatelet regimen in the treating facilities. Clopidogrel was administered for 6 months; aspirin dose was reduced to 81 mg at 6 months and was maintained in all patients at last follow-up. Thus, persistent patency of the aneurysms was not likely to be related to dual antiplatelet therapy. Finally, although persistence of these aneurysms was a common denominator in all cases, none of these aneurysms ruptured during their follow-up evaluation and the natural history of similar cases is still unknown.

Ultimately, 2 patients underwent further treatment by surgical clip placement. The MCA aneurysms, the SCA aneurysm, the OphA aneurysms, and the fetal PCoA aneurysms without coil embolizations could have been treated by surgical clip placement, but the AICA aneurysm and the fetal PCoA aneurysms with previous coil embolizations would have been more difficult for surgery. Assisted coil embolization would be suboptimal in these cases, as it would be difficult to achieve adequate aneurysm obliteration and end-vessel preservation. At the time of treatment with flow diversion, we believed that flow diversion could potentially offer a definitive cure to these complex aneurysms with preservation of the end vessel.

The main limitation of our study was the small number of patients, although we demonstrate here that the observation of persistent aneurysm patency of this subset of aneurysms that incorporate an end vessel is a phenomenon observed at multiple institutions. The minimum follow-up of 12 months and a mean follow-up of 24 months should represent sufficient time to assess aneurysm occlusion, as most studies with flow diversion use a 1-year angiographic result to define success or failure.

Based on our observations, we do not recommend the use of flow diversion for treatment of aneurysms incorporating an end vessel. While the use of flow diverters in off-label cases is growing, we would like to raise concerns about the use of these devices in similar cases as it appears ineffective for complete aneurysm occlusion. It also increases the level of complexity for future backup treatment strategies such as surgical clip reconstruction or other endovascular therapies.

Acknowledgments

We thank Ms. Joanna Brooks of the Baylor College of Medicine for her editorial assistance.

References

  • 1

    Becske T, Kallmes DF, Saatci I, McDougall CG, Szikora I, Lanzino G, et al. : Pipeline for uncoilable or failed aneurysms: results from a multicenter clinical trial. Radiology 267:858868, 2013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Brinjikji W, Lanzino G, Cloft HJ, Kallmes DF: Patency of the posterior communicating artery after flow diversion treatment of internal carotid artery aneurysms. Clin Neurol Neurosurg 120:8488, 2014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Kallmes DF, Hanel R, Lopes D, Boccardi E, Bonafé A, Cekirge S, et al. : International retrospective study of the Pipeline embolization device: a multicenter aneurysm treatment study. AJNR Am J Neuroradiol 36:108115, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Kamran M, Yarnold J, Grunwald IQ, Byrne JV: Assessment of angiographic outcomes after flow diversion treatment of intracranial aneurysms: a new grading schema. Neuroradiology 53:501508, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Kan P, Duckworth E, Puri A, Velat G, Wakhloo A: Treatment failure of fetal posterior communicating artery aneurysms with the Pipeline embolization device. J Neurointerv Surg [epub ahead of print] 2015

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Nelson PK, Lylyk P, Szikora I, Wetzel SG, Wanke I, Fiorella D: The Pipeline embolization device for the intracranial treatment of aneurysms trial. AJNR Am J Neuroradiol 32:3440, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    O'Shaughnessy BA, Getch CC, Bendok BR, Batjer HH: Surgical management of unruptured posterior carotid artery wall aneurysms. Neurosurg Focus 15:1 E9, 2003

  • 8

    Puffer RC, Kallmes DF, Cloft HJ, Lanzino G: Patency of the ophthalmic artery after flow diversion treatment of paraclinoid aneurysms. J Neurosurg 116:892896, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Saatci I, Yavuz K, Ozer C, Geyik S, Cekirge HS: Treatment of intracranial aneurysms using the Pipeline flow-diverter embolization device: a single-center experience with long-term follow-up results. AJNR Am J Neuroradiol 33:14361446, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Szikora I, Berentei Z, Kulcsar Z, Marosfoi M, Vajda ZS, Lee W, et al. : Treatment of intracranial aneurysms by functional reconstruction of the parent artery: the Budapest experience with the Pipeline embolization device. AJNR Am J Neuroradiol 31:11391147, 2010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Tsang AC, Fung AM, Tsang FC, Leung GK, Lee R, Lui WM: Failure of flow diverter treatment of intracranial aneurysms related to the fetal-type posterior communicating artery. Neurointervention 10:6066, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Vedantam A, Rao VY, Shaltoni HM, Mawad ME: Incidence and clinical implications of carotid branch occlusion following treatment of internal carotid artery aneurysms with the Pipeline embolization device. Neurosurgery 76:173178, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Zada G, Breault J, Liu CY, Khalessi AA, Larsen DW, Teitelbaum GP, et al. : Internal carotid artery aneurysms occurring at the origin of fetal variant posterior cerebral arteries: surgical and endovascular experience. Neurosurgery 63:1 Suppl 1 ONS55ONS62, 2008

    • Search Google Scholar
    • Export Citation

Disclosures

Dr. Kan has served as a consultant to Stryker Neurovascular and Medtronic Covidien. Dr. Tawk has direct stock ownership in Blockade Medical and Medtronic. Dr. Welch has served as a consultant to Covidien. Dr. Puri has served as a consultant to Covidien, Stryker, and Codman; has direct stock ownership in InNeuroCo; and has received support of non–study-related clinical or research effort from Covidien and Stryker.

Author Contributions

Conception and design: Kan. Acquisition of data: all authors. Analysis and interpretation of data: Kan, Srinivasan, Mbabuike, Mokin, Mitchell, Duckworth. Drafting the article: Kan, Srinivasan. Critically revising the article: Kan, Srinivasan, Mbabuike, Tawk, Mokin, Duckworth. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Kan. Statistical analysis: Kan. Study supervision: Kan.

Contributor Notes

INCLUDE WHEN CITING Published online September 16, 2016; DOI: 10.3171/2016.6.JNS16402.

Correspondence Peter Kan, Department of Neurosurgery, Baylor College of Medicine, 7200 Cambridge St., Ste. 9A, Houston, TX 77030. email: peter.kan@bcm.edu.
  • View in gallery

    A–C: Cerebral angiogram (anteroposterior [A], lateral [B], and 3D reconstruction [C] views) of the right internal carotid artery showing a large, unruptured, right fetal PCoA aneurysm and a right MCA aneurysm. D: Follow-up cerebral angiogram at 18 months after PED treatment showing persistent filling of both aneurysms and patency of both end vessels. Figure is available in color online only.

  • View in gallery

    A–C: Cerebral angiogram (anteroposterior [A], lateral [B], and 3D reconstruction [C] views) of the left VA injection showing an unruptured left SCA aneurysm. D: Follow-up cerebral angiogram at 24 months showing persistent filling of the aneurysm and robust flow through the left SCA. Figure is available in color online only.

  • View in gallery

    Cerebral angiogram (anteroposterior view [left] and magnified anteroposterior view [right]) of left vertebral artery injection showing a right AICA aneurysm at 24 months after PED treatment with persistent filling.

  • View in gallery

    A–C: Cerebral angiogram (anteroposterior [A], lateral [B], and 3D reconstruction [C] views) of the right internal carotid artery injection showing an unruptured right OphA aneurysm. The large OphA originates from the base of the aneurysm. D: Follow-up cerebral angiogram (3D reconstruction of the right ICA injection) at 48 months showing persistent filling of the aneurysm and OphA. Figure is available in color online only.

  • 1

    Becske T, Kallmes DF, Saatci I, McDougall CG, Szikora I, Lanzino G, et al. : Pipeline for uncoilable or failed aneurysms: results from a multicenter clinical trial. Radiology 267:858868, 2013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Brinjikji W, Lanzino G, Cloft HJ, Kallmes DF: Patency of the posterior communicating artery after flow diversion treatment of internal carotid artery aneurysms. Clin Neurol Neurosurg 120:8488, 2014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Kallmes DF, Hanel R, Lopes D, Boccardi E, Bonafé A, Cekirge S, et al. : International retrospective study of the Pipeline embolization device: a multicenter aneurysm treatment study. AJNR Am J Neuroradiol 36:108115, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Kamran M, Yarnold J, Grunwald IQ, Byrne JV: Assessment of angiographic outcomes after flow diversion treatment of intracranial aneurysms: a new grading schema. Neuroradiology 53:501508, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Kan P, Duckworth E, Puri A, Velat G, Wakhloo A: Treatment failure of fetal posterior communicating artery aneurysms with the Pipeline embolization device. J Neurointerv Surg [epub ahead of print] 2015

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Nelson PK, Lylyk P, Szikora I, Wetzel SG, Wanke I, Fiorella D: The Pipeline embolization device for the intracranial treatment of aneurysms trial. AJNR Am J Neuroradiol 32:3440, 2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    O'Shaughnessy BA, Getch CC, Bendok BR, Batjer HH: Surgical management of unruptured posterior carotid artery wall aneurysms. Neurosurg Focus 15:1 E9, 2003

  • 8

    Puffer RC, Kallmes DF, Cloft HJ, Lanzino G: Patency of the ophthalmic artery after flow diversion treatment of paraclinoid aneurysms. J Neurosurg 116:892896, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Saatci I, Yavuz K, Ozer C, Geyik S, Cekirge HS: Treatment of intracranial aneurysms using the Pipeline flow-diverter embolization device: a single-center experience with long-term follow-up results. AJNR Am J Neuroradiol 33:14361446, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Szikora I, Berentei Z, Kulcsar Z, Marosfoi M, Vajda ZS, Lee W, et al. : Treatment of intracranial aneurysms by functional reconstruction of the parent artery: the Budapest experience with the Pipeline embolization device. AJNR Am J Neuroradiol 31:11391147, 2010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Tsang AC, Fung AM, Tsang FC, Leung GK, Lee R, Lui WM: Failure of flow diverter treatment of intracranial aneurysms related to the fetal-type posterior communicating artery. Neurointervention 10:6066, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Vedantam A, Rao VY, Shaltoni HM, Mawad ME: Incidence and clinical implications of carotid branch occlusion following treatment of internal carotid artery aneurysms with the Pipeline embolization device. Neurosurgery 76:173178, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Zada G, Breault J, Liu CY, Khalessi AA, Larsen DW, Teitelbaum GP, et al. : Internal carotid artery aneurysms occurring at the origin of fetal variant posterior cerebral arteries: surgical and endovascular experience. Neurosurgery 63:1 Suppl 1 ONS55ONS62, 2008

    • Search Google Scholar
    • Export Citation

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