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Case series
Flow diverter stents for unruptured saccular anterior circulation perforating artery aneurysms: safety, efficacy, and short-term follow-up
  1. Anna Luisa Kühn,
  2. Samuel Y Hou,
  3. Mary Perras,
  4. Christopher Brooks,
  5. Matthew J Gounis,
  6. Ajay K Wakhloo,
  7. Ajit S Puri
  1. Division of Neuroimaging and Intervention, Department of Radiology and New England Center for Stroke Research, University of Massachusetts, Worcester, Massachusetts, USA
  1. Correspondence to Dr Ajit S Puri, Division of Neuroimaging and Intervention and New England Center for Stroke Research, Department of Radiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA; ajit.puri{at}umassmemorial.org

Abstract

Background Anterior circulation perforating artery aneurysms including anterior choroidal artery and lenticulostriate artery aneurysms are rare. Injury to these vessels can lead to severe debilitating symptoms.

Objective To present a new approach to treatment using flow diversion technology.

Methods Patients treated with a Pipeline embolization device (PED) for perforator artery aneurysms at our institution between June 2012 and May 2013 were identified and included in our retrospective analysis. We evaluated patient vascular risk factors; family history of aneurysms; aneurysm characteristics; National Institutes of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS) on admission; and angiography follow-up and patient clinical outcome at discharge, 6 months, and 1 year.

Results We included four patients with a mean age of 59.8 years. Two patients had a positive family history of aneurysms. Patient vascular risk factors included smoking, dyslipidemia, and hypertension. All patients presented with a NIHSS and mRS of 0 on admission. Aneurysms were located at the anterior choroidal (n=2) or lenticulostriate artery (n=2) and were treated with a single PED. No periprocedural or postprocedural complications occurred. The patients were discharged with no change in NHISS or mRS score. Six-month and 1-year follow-up angiography showed complete aneurysm occlusion. Mild intimal hyperplasia was seen in 2 cases at 6 months, but was resolved at the 1-year follow-up. No re-treatment was necessary. NIHSS and mRS remained 0 at follow-up time points.

Conclusions Our preliminary results show that flow diversion technology is an effective and safe therapy for complex, hard-to-treat aneurysms in perforating arteries. Larger studies with long-term follow-up are needed to validate our promising results.

  • Aneurysm
  • Device
  • Angiography
  • Technique
  • Flow Diverter
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Introduction

Possible treatments for intracranial aneurysms include surgical and endovascular methods, including coil embolization, stent-assisted coiling, and, more recently, the use of flow diverters. Management decisions on aneurysms arising from less common cerebrovascular locations like anterior circulation perforating arteries such as those from the lenticulostriate artery (LSA) or the anterior choroidal artery (AChA) remain challenging. Information can only rarely be found, and experiences are limited to isolated case reports and small case series. In general, endovascular coiling is now preferred rather than surgical clipping in an increasing number of patients as endovascular treatment has shown to have a better safety profile than the open-surgery approach.1 ,2

However, the main concern about endovascular treatment is its durability. Long-term success of endovascular coiling is about 80–85%. Aneurysm recurrence after coiling occurs in up to 34% of patients1 ,3 and is due to coil compaction within the aneurysm sac or insufficient neck coverage, resulting in suboptimal aneurysm exclusion from the blood circulation. Re-treatment rates range from 4.7% to 10%.4–8 Recurrence rates remain significant despite the use of stents to assist the coiling procedure.9

New devices, termed flow diverters, have been designed for reconstruction of the parent artery and aneurysm occlusion. These devices are self-expanding, tightly meshed tubular implants with a specified pore density that are placed over the aneurysm neck to support intra-aneurysmal blood stasis while maintaining patency of the parent artery. At the same time, these new endovascular flow diversion devices are sufficiently permeable to allow perforators to remain adequately perfused.

There are limited data on flow diverter treatment of LSA and AChA aneurysms. In a recent analysis of the International Retrospective Study of Pipeline Embolization Device, posterior communicating artery (PComA) patency was evaluated after flow diverter treatment of internal carotid artery (ICA) aneurysms wherein the device covered the ostium of the PComA.10 Covered PComAs occluded or had reduced flow at the 1-year follow-up in 27% and 18% of cases, respectively. However, none of these patients had clinical sequelae indicating sufficient collateral flow. Included in this series was a single AChA aneurysm, and although not explicitly stated, it is assumed that the AChA remained patent given that there were no adverse outcomes. In a larger series that included 28 AChA aneurysms treated with flow diverters, there were no reported AChA occlusions.11 Perforating arteries such as the AChA and LSA require study since occlusion of these vessels might have significant clinical implications. Therefore, we present our data on four consecutive, unruptured LSA and AChA artery aneurysms that were endovascularly managed with flow diverter technology.

Materials and methods

The retrospective study was approved by the hospital institutional review board.

Patients

We retrospectively included all patients who presented at our institution with perforator artery aneurysms between June 2012 and May 2013. For each patient, demographic data, including vascular risk factors, age, gender, family history, and aneurysm characteristics, were evaluated. Further relevant clinical data were also recorded, including symptoms at presentation, neurological examination at baseline, and neurological outcome based on National Institutes of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS) at discharge and 6 months’ follow-up. Aneurysm size and location were recorded, and pre- and post-treatment imaging was evaluated for the occurrence of thromboembolic events, vessel patency, and aneurysm occlusion. Various therapeutic options, including observation, surgical clipping, and endovascular treatment, were discussed with the patients by our multidisciplinary team of interventional neuroradiologists, cerebrovascular neurosurgeons, and neurologists. Risks and benefits were balanced for all therapeutic options. Endovascular parent vessel reconstruction in all patients included in this study was achieved using a Pipeline embolization device (PED).

Diagnostic procedure and interventional approach

All patients underwent CT scanning of the head and received DSA before intervention. DSA demonstrated the presence of two aneurysms located at the M1 portion involving the LSA and two aneurysms at the AChA. Patients were given 81 mg of aspirin and 75 mg of clopidogrel daily for at least 5 days before the elective procedure. Patients were tested before the procedure to ensure therapeutic antiplatelet effect, defined in our practice by a VerifyNow P2Y12 assay showing at least 50% platelet inhibition or P2Y12 reaction units of <200 with platelet aggregation assay. Dual-antiplatelet therapy was continued for a minimum of 6 months, with aspirin continued life-long.

Diagnostic and interventional procedures were performed by state-of the-art biplane digital angiography (Philips, Allura Biplane FD20/20, Philips Medical, Best, Netherlands). All patients underwent treatment under general anesthesia.

A triaxial system, consisting of an 8F long sheath, 6F Shuttle guide catheter, and an intermediate guide catheter, was placed into the carotid artery. Before placement of the intermediate catheter, a vasodilator was infused slowly to prevent any catheter-related spasm. Apart from the standard projections and the three-dimensional (3D) angiography, magnified views were obtained for the best projection to visualize the distal and proximal aspect of the device. In all cases, the PED was successfully placed via a microcatheter. Angiography control was obtained after placement of the device, at 6 months and at 1 year. In addition cone-beam CT was carried out after placement of the device to ascertain the wall apposition.

The exclusion of the aneurysm and patency of the parent vessel and other surrounding vessels were assessed. Any residual aneurysm was recorded. Both, preoperative and postoperative angiograms were reviewed by a single neurointerventionalist.

Dual antiplatelet therapy was continued for 6 months postoperatively to prevent thromboembolism and stent occlusion. Beyond the 6-month follow-up, patients continued to receive aspirin for life. Two patients received dual anti-platelet therapy for 1 year and only aspirin thereafter.

Results

We identified four patients with mean age of 59.8 years, ranging from 51 to 71 years. Two patients had a family history of aneurysms. Patient vascular risk factors included smoking (three patients), dyslipidemia (two patients), and hypertension (one patient). One patient presented with clinical symptoms of blurred vision. All other patients were asymptomatic. On admission, NIHSS and mRS were 0 in all cases (table 1). All patients were treated with a single PED. All devices were successfully placed over the aneurysm neck, providing complete coverage. All devices were deployed with complete wall apposition. No periprocedural or postprocedural complications occurred.

Table 1

Patient data and aneurysm characteristics

The postprocedural NIHSS and mRS scores at discharge and 6 months were 0 in all cases at both times. All patients tolerated the procedure well and were able to perform all previous activities.

Angiography results

Immediate control angiography after PED placement showed good flow within the parent artery and significantly reduced (n=4) flow, flow stasis, within the aneurysms. No vasospasm or distal emboli were noted. Six-month angiography was available for all patients (100%) and 1-year follow-up was available for two patients (50%). Six-month angiography showed no opacification of the aneurysms in any patient. No significant intimal hyperplasia or in-stent stenosis was seen. Two patients (50%) showed mild intimal hyperplasia at the proximal end of the stent. One-year control angiography (n=2) demonstrated stable occlusion of the aneurysms. The intimal hyperplasia noted in the two patients had resolved completely on the 1-year angiogram. There was no evidence of in-stent thrombosis/stenosis or distal thromboembolic events.

Aspirin and clopidogrel was continued for an additional 6 months in the two cases where mild intimal hyperplasia was seen at the 6-month angiography. There was no evidence of perforator artery occlusion (table 2). Below is a listing of pertinent findings for each case:

Table 2

Summary of treatment, outcome, and follow-up results

Case 1: A 51-year-old woman with first-degree family history of aneurysmal subarachnoid hemorrhage underwent screening MR angiography that showed a left-sided LSA aneurysm measuring 4.0×3.0 mm on diagnostic angiography (figure 1A) and 3D angiography (figure 1B). The patient's NIHSS and mRS scores were 0 on admission. The 2.75×12 mm Pipeline device was successfully delivered and placed over the aneurysm neck; angiography after device placement showed the device was adequately positioned over the aneurysm neck with proper vessel wall adherence. There was no evidence of acute thrombus formation/distal emboli or vasospasm. Contrast injection showed significant inflow reduction and stagnation of contrast within the aneurysm sac throughout the venous phase on DSA images and on cone-beam CT (figure 1C, D). In addition, DSA confirmed perforator artery patency. The patient tolerated the procedure well and was discharged with a NIHSS and mRS score of 0. Six-month follow-up angiography showed complete occlusion of the aneurysm lumen without compromise of perforator artery perfusion (figure 1E). No intimal hyperplasia was seen. The patient continued to do well; NIHSS and mRS scores remained 0.

Figure 1

A 51-year-old woman with an incidentally discovered left-sided lenticulostriate artery (LSA) aneurysm (A, arrow) where the LSA originates from the base of the aneurysm (B, three-dimensional angiography, arrow). After device placement, angiography (C, arrow) and contrast-enhanced cone-beam CT shows residual contrast within the aneurysm sac (D, arrow). Six-month follow-up angiography (E) and contrast-enhanced cone-beam CT (F) showed complete occlusion of the aneurysm lumen without compromise of perforator artery perfusion.

Case 2: A 61-year-old woman received clinical investigation for complaints of blurry vision. NIHSS and mRS were 0 at the time of admission. The patient was diagnosed with a left-sided AChA aneurysm of 3.3×4.5 mm in size (figure 2A, B). A 3.0×10 mm PED was successfully placed across the aneurysm neck (figure 2C). Follow-up angiography immediately after device placement showed contrast stagnation within the aneurysm lumen throughout the venous phase (figure 2D). The device was well apposed to the vessel wall. No acute thrombus formation/distal emboli or vasospasm was seen. The patient was discharged and returned to performing all previous activities (NIHSS and mRS 0). Six-month and 1-year follow-up angiography and cone-beam CT showed complete aneurysm occlusion with patent perforator arteries (figure 2E–G).

Figure 2

A 61-year-old woman was diagnosed with a left-sided anterior choroidal artery (AChA) aneurysm on DSA (A, arrow) and rotational angiography (B). The Pipeline device was successfully placed across the aneurysm neck (C) with control angiography showing contrast stagnation (D, arrow). One-year follow-up angiography showed complete aneurysm occlusion with patent perforator arteries (E, arrow points to patent AChA). Contrast-enhanced cone-beam CT shows (F, G) no intimal hyperplasia.

Case 3: A 56-year-old woman presented to the emergency department with sudden onset of a thunderclap headache. MRI showed no subarachnoid hemorrhage; however, a 3 mm right AChA aneurysm was discovered. Diagnostic 3D angiography showed a 3.0×2.3 mm aneurysm of the right AChA with the origin of the AChA arising from the base of the aneurysm (figure 3A, B). Admission mRS and NIHSS were both 0. A 4.25×12 mm PED was positioned across the neck of the aneurysm in the right internal carotid artery. Control angiography showed contrast stasis in the dome of the aneurysm (figure 3C). Follow-up angiography at 6 months after treatment showed complete obliteration of the AChA aneurysm with patent AChA and mild intimal hyperplasia within the treated segment (figure 3D) that had resolved at the 1-year follow-up (figure 3E, F). There were no periprocedural adverse events and the mRS and NIHSS were 0 at clinical follow-up.

Figure 3

A 56-year-old woman has an incidentally discovered right anterior choroidal artery (AChA) aneurysm with the AChA originating from the aneurysm base (A and B, arrow). A Pipeline device was positioned across the neck of the aneurysm in the right internal carotid artery distal to the origin of the ophthalmic artery with contrast stasis within the dome (C, arrow). Follow-up angiography at 6 months after treatment showed complete obliteration of the AChA aneurysm with patent AChA (D, arrow) and mild intimal hyperplasia within the treated segment. At one year follow-up, contrast enhanced cone-beam CT shows durable aneurysm exclusion and patent AChA (E, arrow) and resolution of mild intimal hyperplasia (F).

Case 4: A 71-year-old woman with first-degree family history of aneurysmal subarachnoid hemorrhage underwent screening MR angiography that showed five aneurysms. DSA disclosed: (1) 4 mm right superior hypophyseal artery aneurysm, (2) 3 mm right ophthalmic artery aneurysm, (3) 1.2 mm right middle cerebral artery (MCA) bifurcation aneurysm, (4) 2.3 mm left LSA aneurysm (figure 4A), (5) 3 mm right cavernous segment aneurysm, and (6) An irregular, 4 mm basilar tip aneurysm. The basilar tip aneurysm was treated with coiling and in a separate session the right superior hypohyseal and ophthalmic artery aneurysms were treated with a single PED. 3D angiography showed the origin of the LSA from the base of the aneurysm (figure 4B). The left LSA aneurysm was treated with a 2.5×10 mm PED, with minimal contrast stasis along the dome of the aneurysm (figure 3C). Cone-beam CT demonstrated excellent apposition to the MCA (figure 4D). Follow-up angiography at 6-months after treatment of the left LSA aneurysm showed complete obliteration of the aneurysm and patency of the MCA as well as the LSAs (figure 4E, F).

Figure 4

A 71-year-old woman has an incidentally found left lenticulostriate artery (LSA) aneurysm (A, arrow) with an LSA perforator originating at the base of the aneurysm (B, arrow). The aneurysm was treated with a Pipeline device with minimal contrast stasis along the dome of the aneurysm (C). Cone-beam CT showed proper positioning of the Pipeline embolization device and excellent wall apposition (D). Follow-up angiography and contrast-enhanced cone-beam CT at 6-months showed complete obliteration of the aneurysm and patency of the LSAs (E, F).

Discussion

Anterior circulation perforating artery aneurysms are rare. AChA aneurysms comprise 2–5% of the intracranial aneurysms,12 ,13 and fewer than 60 cases of true LSA aneurysms have been reported.14 ,15 Owing to the small number of angiographically detected LSA aneurysms, the natural history of these aneurysms is unclear.16–18

A few reports described the size of ruptured LSA aneurysms as significantly smaller than the typical size at which berry aneurysms would be expected to rupture.19–21 The unique location and its hemodynamic stress may also play an important role in the risk of rupture at smaller sizes.16 Despite the small size of such aneurysms, rupture results in a poor outcome, and thus treatment of incidentally detected aneurysms is reasonable.22 Most reported LSA aneurysms have been treated by craniotomy and clipping, and this certainly is an option for these lesions depending on the anatomy, with a small risk of perforator infarction (reviewed by Vargas et al15). Catheterization and coiling of these small aneurysms carries a risk of intraoperative aneurysm rupture and of thromboembolic occlusion of the perforator arteries, especially at the neck of the aneurysm, from where these vessels usually arise.

Surgical clipping of aneurysms can result in significant ischemic complications depending on the supplied area. The AChA, which originates at the C7 level of the ICA supplies the area of the optic tract, cerebral peduncle, and internal capsule. Occlusion of the vessel commonly results in AChA syndrome, consisting of hemianopsia, contralateral hemiparesis, and hemianesthesia.13 The most common complication after neurosurgical clipping of these aneurysms has been reported to be acute ischemic stroke.23 Morbidity and mortality rates range from 5% to 50%.24 ,25 The LSAs arise from the MCA and supply part of the basal ganglia and internal capsule. Occlusion of these arteries results in lacunar stroke. Obviously, the goal of successful aneurysm treatment in this delicate brain territory also focuses on minimizing the procedural and postprocedural risk of ischemic complications.

Based on the results of our cases, LSA and AChA aneurysms can be treated with flow-diverting devices with excellent clinical outcomes. No ischemic complications were noted. In a retrospective, surgically treated case series by Cho et al in 200826 on a total of 53 cases the authors found postoperative infarcts in the AChA distribution in seven of 27 patients with unruptured aneurysms (25.9%). Friedman et al24 concluded from his study using craniotomy and clipping in 51 patients with AChA aneurysms that such treatment carries a significant risk of debilitating ischemic complications and that patients are at extremely high risk of a stroke.

Temporary artery occlusion during endovascular coil embolization may also result in postoperative complications, such as those described by Kim et al.27 The authors found intraprocedural temporary AChA occlusion in five of 37 cases (13.5%), resulting in transient contralateral hemiparesis in two cases (5.4%).

The concept of flow diversion emerges from intrasaccular aneurysm occlusion by excluding the aneurysm from the circulation without selective catheterization and major intrasaccular aneurysm manipulation. In addition, flow diverters reduce intra-aneurysmal flow by decreasing fluid momentum transfer into the aneurysm sac, which then leads to thrombus formation and subsequent exclusion from the intracranial circulation.28 However, experimental studies have shown that the porous mesh of the diverter does not provide sufficient resistance to pressure-driven flow in perforators that would ultimately lead to their occlusion.29–32 Clinical experience indicated a perforator infarction rate of 3% after flow diversion treatment, with strong prevalence in the posterior circulation.33 Although we could find no reports of flow diverter treatment for LSA aneurysms, a few studies have included AChA aneurysms, with no reported occlusion of the AChA.10 ,11 ,34 As in our case, the curative reconstruction that is induced by the flow diverter typically does not occur immediately but evolves over a period of weeks to months owing to flow alternation into the aneurysm sac and remodeling of the parent vessel over the endoprosthesis.35 ,36 All our patients showed complete aneurysm occlusion at 6-months’ follow-up as well as patency of the perforating arteries.

The PED used in this study is indicated for the treatment of large (>10 mm) aneurysms of the ICA from the petrous to the superior hypophyseal segments.37 There are numerous reports of deploying this and other similar devices in the anterior circulation at the level of, and beyond, the circle of Willis.11 ,34 ,38–46 Use of the PED for AChA and LSA aneurysms reported here is off-label. These preliminary data presented in a small number of patients with rare LSA and AChA aneurysms indicated that complete occlusion with preservation of the perforating arteries using flow diverter treatment is possible.

Conclusion

Endovascular reconstruction with flow diverters represents a fundamental paradigm shift in the technique of neurointerventional aneurysm treatment.

We show that the treatment of LSA and AChA aneurysms with the PED is effective and safe during a short-term observation. Larger studies with long-term follow-up are required to validate these promising results.

Acknowledgments

We thank Ms Mary Howk for her help with the editing of the manuscript.

References

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Footnotes

  • Contributors Study design: ASP. Data collection: ALK, MP, CB. Interpretation of data: ALK, SYH, AKW, ASP. Literature research: ALK, ASP. Drafting first manuscript version: ALK, SYH, ASP. Revision of manuscript for important intellectual content: MP, CB, MJG, AKW. Approval of final manuscript: all authors.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval Hospital institutional review board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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