No differences in effectiveness and safety between pipeline embolization device and stent-assisted coiling for the treatment of communicating segment internal carotid artery aneurysms

Abstract

Background

Aneurysms arising from the communicating segment (C7) of the internal carotid artery (ICA) are one of the most frequent locations of intracranial aneurysms. Stent-assisted coiling (SAC) and flow diversion therapies are both endovascular strategies used for the treatment of ICA aneurysms occurring at the C7 segment.

Objective

The aim of this study is to compare both methods' angiographic and functional outcomes, and procedural complications. To our knowledge, this is the first study to compare both modalities for aneurysms at this location.

Methods

A retrospective review was performed of our prospectively collected database from 2008 until 2017 for patients treated with SAC and from 2013 until 2017 for patients treated with pipeline embolization devices (PEDs).

Results

We identified 35 patients for this cohort with 38 aneurysms; 17 treated with SAC and 21 with PED. Mean age was 59 years, and 30 patients were female (86%). Complete occlusion at last follow-up occurred in 70.6% of patients in the SAC group and in 81% in the PED group (p = 0.45). Posterior communicating artery patency at last follow-up did not differ significantly between the two groups (94.1% vs 85.7%; p = 0.40). Good functional outcome at last follow-up (mRS 0–2) was achieved in 100% and 88.2% of patients, respectively. Additionally, there was no significant difference between the two groups for retreatment rates, procedural hemorrhagic, or thromboembolic complications.

Conclusion

SAC and PED are two equally efficacious modalities for endovascular treatment of ICA aneurysms arising at the communicating segment of the ICA.

Introduction

Endovascular treatments have been increasingly used over the last decade and are now the procedures of choice for selected intracranial aneurysms. These treatments aim to exclude aneurysm from the cerebrovascular circulation distinct mechanisms. Stent-assisted coiling (SAC) was developed as an alternative technique for giant, wide-necked and fusiform aneurysms which are not amenable to traditional endovascular coil embolization. This technique involves packing the intrasaccular lumen of the aneurysm with coils and using a stent to buttress the coil mass and preventing coil protrusion into the parent artery.¹ Recanalization of the aneurysm, however, following coil deployment is a recognized limitation of the technique ranging from 12% to 14.5%.^2,3 Recently, flow diversion technique using special stents, such as the pipeline embolization device (PED), has emerged as an effective treatment for these complex aneurysms, with no reports of recanalization following complete occlusion.⁴ The PED disrupts blood flow into the aneurysm, leading to thrombosis followed by luminal reconstruction of the parent artery by endothelialization of the flow diverter which acts as a scaffold.⁵

The most appropriate endovascular strategy depends on clinical factors and anatomical characteristics of the aneurysm. Since the approval of the PED by the Food and Drug Administration (FDA) in 2011, there has been an increasing use of flow diverter therapy in the US, which has partially displaced the use of SAC techniques.⁶ Despite this trend, there are currently few studies comparing the effectiveness and safety of these two techniques in the medical literature.^7–11 For aneurysms in the communicating segment of the internal carotid artery (ICA), there are no comparison studies. Our study is the first to compare outcomes and complications in patients with aneurysms of the communicating segment of the ICA, treated with SAC or PED.

Methods

Study design

A retrospective review was performed from a prospectively maintained database consisting of patients treated for intracranial aneurysms from a single major academic institution in the United States between January 2008 and March 2017. Institutional Review Board approval was obtained prior to study initiation. Patient informed consent was not sought due to the retrospective nature of this study. Inclusion criteria included a communicating segment ICA aneurysm, which was treated endovascularly with either SAC or PED and at least one follow-up imaging. Patients were recruited consecutively from 2008 to 2015 for SAC treatment, after which no eligible patients were identified secondary to a change in the practice of the department, while patients treated with PED spanned 2013–2017 (Figure 1). A total of 35 eligible patients with 42 treated communicating segment ICA aneurysms were identified, four patients (with 4 communicating segment aneurysms) were excluded as they did not meet eligibility criteria (Figure 2).

Figure 1.

Case frequency over time of SAC and PED procedures at a major academic hospital in the USA. Here it is shown that the transition in practice from SAC to PED occurred after 2013, which is the year when flow diversion was approved in the USA for the treatment of intracranial aneurysms.

Figure 2.

Flowchart of patients included in the present study.

Objectives and outcomes

This study aims to compare the outcomes of communicating segment (C7) ICA aneurysms, defined according to the Bouthillier et al. classification,¹² treated by either SAC or PED. The primary outcome evaluated was aneurysm occlusion status at the first imaging follow-up. Secondary outcomes were aneurysm occlusion status at last imaging follow-up, functional outcomes at last follow-up, retreatment, and complications rates.

Data collection

Using the aforementioned database, the following information was collected from both cohorts; demographics and risk factors (e.g. age, sex, smoking status, diabetes), clinical presentation (e.g. pre-treatment Modified Rankin Scale (mRS) score, and rupture status at admission), aneurysm characteristics (e.g. location, previous treatment, morphology, maximal diameter, and daughter sac), presence of fetal posterior communicating artery (PComA), as evidenced on pretreatment digital subtraction angiography (DSA) by agenesis or a hypoplastic P1 posterior cerebral artery segment with a diameter less than the PComA diameter (Figure 3),^13,14 treatment details (e.g. number of devices used, adjunctive coil embolization), and angiographic and functional outcomes were recorded.

Figure 3.

Anteroposterior digital subtracted cerebral angiogram of the posterior circulation which evidences a bilateral hypoplastic P1 segment (a) and a right absent P1 segment (b) of the posterior cerebral artery. (Vertical black arrows points to the posterior cerebral artery and the horizontal black arrow points to the superior cerebellar artery).

Procedure details

The type of procedure was determined by the treating interventionalist on an individual patient basis. All patients began dual antiplatelet therapy, clopidogrel 75 mg and aspirin 325 mg daily, 14 days prior to the procedure. Only patients undergoing PED placement had platelet function studies completed, using light test aggregometry performed on the day of the procedure. Platelet aggregation tests >50% of the maximum in 2 runs of 5 µmol/L adenosine diphosphate (ADP) were considered clopidogrel non-responsive. If a patient was deemed a non-responder to clopidogrel, the medication was changed to ticagrelor or prasugrel. Current literature supports this as clopidogrel non-responders have shown to be associated with increased higher rate of thromboembolic complications when compared to responders, and this risk can be mitigated by switching to ticagrelor.¹⁵ Intravenous heparin was administered during the procedure to achieve an activated clotting time greater than 250–300 s. Heparin was discontinued after the procedure. Dual antiplatelet therapy was continued for 3 months after the device placement with aspirin continued indefinitely thereafter.

Imaging follow-up

A DSA-based follow-up imaging protocol was used and aneurysms were classified as either completely occluded (100%), nearly completely occluded (90–100%), or incompletely occluded (<90%) at each follow-up. For final follow-up, we collected available DSA, magnetic resonance angiography (MRA) data, and retreatment procedures.

Statistical methods

Categorical variables are reported as proportions. Continuous variables are reported as mean ± SD or median (Interquartile range (IQR)) as appropriate according to the distribution of the data tested by Shapiro–Wilk test. In each group, categorical variables were compared using the Chi-square (χ²) test and continuous variables were compared using the Mann–Whitney U test. Statistical significance was set to a p-value of less than 0.05. All statistical analyses were performed using the STATA software version 14 (StataCorp, College Station, TX, USA).

Results

Patient demographics

Thirty-five patients (85.7% female with a median age of 60 years) harboring 38 C7 segment aneurysms met the eligibility criteria (Table 1). Sixteen patients (45.7%) had multiple intracranial aneurysms and most patients (88.6%) presented with an mRS score of 0 before treatment.

Table 1.

Patient demographics, aneurysms characteristics and procedure details.

Parameter	Result
Number of patients	n = 35
Gender
Female	30 (85.7%)
Age (years)	60 (IQR 52–67)
Smoking history	9 (25.7%)
Diabetes mellitus	1 (2.9%)
Statins therapy	16 (45.7%)
Moderate intensity regimen	11 (68.8%)
High intensity regimen	5 (31.2%)
Multiple intracranial aneurysms	16 (45.7%)
Pretreatment mRS
0	31 (88.6%)
1	3 (8.6%)
2	4 (2.9%)
mRS at last follow-upa	n = 34
0	26 (76.5%)
1–2	6 (17.7%)
5	1 (2.9%)
6b	1 (2.9%)
Number of aneurysms treated	n = 38
Type of treatment
Stent-assisted coiling	17 (44.7%)
Pipeline embolization device (PED)	21 (55.3%)
Adjunctive coil embolization in PED	2 (9.5%)
Aneurysm morphology
Saccular	36 (94.7%)
Fusiform	2 (5.3%)
Daughter sac	10 (26.3%)
Fetal PComA	6 (15.8%)
Maximal diameter, mm	7.8 (IQR 4.6 to 12)
<7	15 (39.5%)
7–9.9	10 (26.3%)
10–19.9	13 (34.2%)
≥20	0 (0%)
Presentation
Ruptured	5 (13.2%)
Unruptured	33 (86.8%)
Previously treated	14 (36.8%)
Coil embolization	10 (71.4%)
Microsurgical clipping	4 (28.6%)
Need for retreatment	5 (13.2%)
Last radiographic follow-up, months (median; IQR)	12.3 (6.2–32.3)
Follow-up occlusion rate
Occluded (100%)	29 (76.3%)
Near completely occluded (90–100%)	7 (18.4%)
Incompletely occluded (<90%)	2 (5.3%)
Post-procedure antiplatelet drug
ASA 325 mg + clopidogrel 75 mg	30 (79.0%)
ASA 325 mg + prasugrel 10 mg	1 (2.6%)
ASA 81 mg + ticagrelor 180 mg	7 (18.4%)
Procedure details	n = 35
Number of PEDs placed	1 (IQR 1 to 1)
1	16 (88.9%)
2	2 (11.1%)
Number of stents placed
1	17 (100%)
Number of coils placed	5 (IQR 2–8)
Intracranial hemorrhagic complicationsc	4 (11.4%)
Thromboembolic complicationsc	2 (5.7%)
Procedural related complications	5 (14.3%)
Femoral pseudoaneurysm	2 (5.7%)
Asymptomatic ICA dissection	1 (2.8%)
Hemodynamic complication: transient  monoparesis of right upper limb	1 (2.8%)
Retroperitoneal bleeding	1 (2.8%)

^aMissing data: 1.

^bThis patient died 1 month after a retreatment with a PED due to a massive right occipital brain hemorrhage.

^cSee complications section in the results for further details.

Seventeen (44.7%) aneurysms were treated with SAC whereas 21 (55.3%) were treated with PED. Thirty-six (94.7%) aneurysms were saccular. Fetal PComA was present in six (15.7%) aneurysms, five (29.4%) in the SAC group and one (4.8%) in the PED group. Five (13.2%) aneurysms presented with rupture at admission.

Procedure details

Eighteen procedures were performed for PED placement and 17 procedures for SAC (Table 1, procedures subsection). We observed a progressive increase in the utilization of PED for these aneurysms with a concurrent decrease in SAC procedures (Figure 1).

Comparison of aneurysms characteristics treated by SAC vs PED

Age, gender, diabetes mellitus status and history of statins treatment were not statistically significantly different between the two groups (Table 2). Smoking was found to be significantly more prevalent in patients with aneurysms treated with SAC (p = 0.02). Aneurysms treated with SAC were significantly larger (8.6 mm; IQR 7–12) than those treated with PED (4.9 mm; IRQ 3.54–11.5) (p = 0.047). There were no differences in presentation status at admission (p = 0.81). Previously treated aneurysms were significantly more likely to be treated with SAC (p = 0.01) and the previous treatment was more likely to be previous coiling (p = 0.01).

Table 2.

Comparison of PED and SAC treatment modalities in C7 segment aneurysms.

Variable	Treatment modality		p-value
	SAC	PED
	17 (44.7%)	21 (55.3%)
Age at time of treatment
Years, median (IQR)a	58 (IQR 52–64)	61 (IQR 54–67)	0.43
Female gender	15 (88.2%)	17 (80.1%)	0.54
Smoking history	7 (41.2%)	2 (9.5%)	0.02
Diabetes mellitus	0 (0%)	1 (4.8%)	0.36
Statins treatment	10 (58.8%)	9 (42.9%)	0.32
Aneurysm morphology
Saccular	17 (100%)	19 (90.5%)	0.19
Fusiform	0 (0%)	2 (9.5%)
Maximal diameter
millimeters, median (IQR)a	8.6 (IQR 7–12)	4.9 (IQR 3.54–11.5)	0.047
Daughter sac	5 (29.4%)	5 (23.8%)	0.69
Fetal PComA	5 (29.4%)	1 (4.8%)	0.04
Presentation
Ruptured	2 (11.8%)	3 (14.3%)	0.81
Unruptured	15 (88.2%)	18 (85.7%)
Multiple aneurysms	7 (41.2%)	12 (57.1%)	0.32
Previously treated	10 (58.8%)	4 (19.1%)	0.01
Coiling	9 (90%)	1 (25%)	0.01
Clipping	1 (10%)	3 (75%)
Outcomes
First imaging follow-up
Elapsed time to first imaging follow-up (months)	6.1 (IQR 5–7.9)	6.23 (IQR 3.7–6.6)	0.36
Aneurysm complete occlusion at first follow-up	14 (82.4%)	15 (71.4%)	0.43
Occlusion status classification
Occluded (100%)	14 (82.4%)	15 (71.4%)	0.06
Near completely occluded (90–100%)	3 (17.6%)	1 (4.8%)
Incompletely occluded (<90%)	0 (0%)	5 (23.8%)
Last imaging follow-up
Elapsed time to last imaging follow-up (months)	27 (IQR 12–41.9)	8.3 (IQR 6–15)	0.01
Aneurysm complete occlusion at last follow-up	12 (70.6%)	17 (81.0%)	0.45
Occlusion status classification
Occluded (100%)	12 (70.6%)	17 (81.0%)	0.15
Near completely occluded (90–100%)	5 (29.4%)	2 (9.5%)
Incompletely occluded (<90%)	0 (0%)	2 (9.5%)
PComA patency at last imaging follow-up	16 (94.1%)	18 (85.7%)	0.40
Retreatment	2 (11.8%)	3 (14.3%)	0.81
mRS on last follow-upb	n = 17	n = 18
≤2	17 (100%)	15 (88.2%)	0.14
>2	0 (0%)	2 (11.8%)
Intracranial hemorrhagic complications	1 (5.9%)	3 (16.7%)	0.31
Thromboembolic complications	0 (0%)	2 (11.1%)	0.15
Other procedural related complications	1 (5.9%)	4 (22.2%)	0.17

Bold values: p-value < 0.05.

Categorical variable (%); p-value: χ² test.

^aMedian (IQR); p-value: Mann–Whitney test.

^bMissing data: 1.

Angiographic and functional outcomes of aneurysms treated by either SAC or PED

The median time for the first imaging follow-up was 6.1 and 6.23 months in the SCA and PED cohorts, respectively (p = 0.36). Complete occlusion was achieved in 82.4% of aneurysms in the SAC cohort and 71.4% for the PED cohort, but this was not statistically significant (p = 0.43) (Table 2).

The median duration to last imaging follow-up was shorter (8.3 months) for aneurysms treated with PED compared to aneurysms treated with SAC (27 months) (p = 0.01). At last imaging follow-up aneurysm occlusion status was evaluated with DSA in 22 (57.9%) and with MRA in 11 (42.1%). Complete occlusion at last imaging follow up was noted in 70.6% and 81% for the SAC and PED groups respectively (p =  0.45). Aneurysmal neck recanalization was identified in two aneurysms in the SAC cases cohort and in none of the PED cases at last follow-up. At last follow up imaging the PComA was patent in 94.1% and 85.7% of cases of SAC and PED therapy respectively (p = 0.40).

In an analysis of functional outcomes at last clinical follow-up, we found that there was good functional outcome (defined as an mRS ≤ 2) in 100% of the SAC group and 88.2% for the PED group (p = 0.14).

Complications of aneurysms treated by either SAC or PED

Intracranial hemorrhagic complications were observed in 11.4%, thromboembolic complications in 5.7% and other procedural related complications in 14.3% of aneurysms treated.

The rate of intracranial hemorrhagic, thromboembolic, and other procedural related complications was 5.9%, 0%, and 5.9% and 16.7%, 11.1%, and 22.2% for the SAC and PED cohorts, respectively, and were not significantly different (Table 2).

All four hemorrhagic complications reported occurred in non-ruptured aneurysms. The single intracranial hemorrhage in the SAC cohort was a small and asymptomatic right temporoparietal subarachnoid hemorrhage (SAH) which was treated conservatively. In the PED cohort one patient had extravasation detected intra-procedurally, which was controlled with Onyx and an external ventricular drain (EVD) but suffered a second frontal hemorrhage on removal of the EVD but made a complete recovery. A second patient had a delayed (23 days post procedure) right occipital hemorrhage with transient visual disturbance which resolved. A third patient in the PED cohort presented with an acute subdural hematoma 1 day after following elective PED procedure which was treated with urgent craniotomy. The post-operative course was complicated by complete occlusion of the ICA, while off antiplatelet therapy, but underwent successful emergent thrombectomy. The patient suffered persistent aphasia and right sided weakness. The final patient in the PED cohort was noted to have an intraprocedure thrombosis which was treated with eptifibatide, heparin, and a balloon assisted technique. On post-operative day 1, the patient presented with anomia and right monoparesis which progressively improved until discharge leaving persistent mild residual weakness.

Retreatments

Two patients (11.8%) who underwent SAC required additional coil placement due to recanalization of the aneurysm. For the PED group, three patients (14.3%) required retreatment with an additional PED placement following evidence of incomplete occlusion on imaging at a mean of 8.43 months. Retreatment in the PED group was performed in mean of 11.2 months after the first procedure. No statistically significant differences between the rates of retreatment was evidenced between the two treatment modalities (p = 0.81) (Table 2). One patient who underwent a PED retreatment died 1 month after the second procedure due to a massive occipital hemorrhage (Table 1).

Discussion

This single center study has evidenced an institutional shift in practice in terms of the preferred endovascular treatment for communicating segment ICA aneurysms, as the use of PED has become predominant (Figure 1). Crobeddu et al. reported a decrease in the use of SAC from 14.7% to 6.9% (p = 0.04) in their cohort over a 4 year period which began when PED initially became available.⁶ We speculate that technical advantages of flow-diversion techniques over SAC may be responsible for these findings which include avoidance of accessing the aneurysm sac and thus reducing the risk of iatrogenic rupture during coil placement, particularly for smaller aneurysms; multiple aneurysms located nearby can be treated in a single procedure (as evidenced in three of our patients) (Figure 4); the ability to remodel an entire vessel thus preventing aneurysm recanalization and de novo aneurysms formation in the setting of a dysplastic parent vessel.⁷ These advantages have led to increase use of flow-diverting strategies with a concurrent decrease in SAC interventions.^6,16

Figure 4.

Lateral digital subtracted cerebral angiogram of the right internal carotid artery which evidences two aneurysms in near proximity to the PComA (vertical white arrows) and a third aneurysm in the ophthalmic segment (horizontal white arrow). Multiple neighboring aneurysms may be treated with a single PED deployed across the parent artery.

Despite the described theoretical advantages, very few studies comparing these two techniques have been reported in the literature. Adeeb et al. conducted a study that compared outcomes in ophthalmic ICA segment aneurysms treated with either SAC and PED and found no differences in occlusion rates and functional outcomes at last follow-up.⁷ In another study performed by Zhang et al. in which a propensity score analysis was done to compare the safety and efficacy of flow diverters to SAC in large and giant aneurysms,¹¹ a significantly higher aneurysm occlusion rate was achieved with flow-diverting therapy at 6 months angiographic follow-up, while hemorrhagic and ischemic complications were similar between the groups.

To the best of our knowledge, our study is the first to compare the outcomes of flow-diverting techniques and SAC for aneurysms located in the communicating segment of the ICA. We demonstrated that there were no significant differences in functional outcomes, aneurysm occlusion status at first and last imaging follow-up, intracranial hemorrhagic and thromboembolic complications between these treatment modalities.

Additionally, we also sought to evaluate any potential effect that fetal PComA might have on occlusion rates. Previous studies have reported incomplete occlusion when it is present, particularly with flow-diversion therapy and recommend microsurgical clipping as a preferred therapy in such cases.^13,17–20 In our sample, more patients with a fetal PComA were treated with SAC (n = 5) than with PED (n = 1) (p = 0.04). This difference, however, was at least partially due to temporal effects, with flow diversion technology not available when the fetal PComA cases were treated. The single patient with a fetal PComA treated with PED had complete occlusion of the aneurysm. Interestingly, this patient’s aneurysm was a recurrence of a previously clipped C7 aneurysm (Figure 5). For those patients with fetal PComA treated with SAC, three patients demonstrated complete occlusion at last imaging follow-up, and only two had persistence of the aneurysm with a Raymond–Roy grade of 2. Nevertheless, the presence of fetal PComA for patients treated with SAC was not associated with increased risk of incomplete occlusion (p = 0.53).

Figure 5.

Lateral digital subtracted cerebral angiogram (DSA) of the internal carotid artery (a) and three-dimensional DSA (b) reconstruction which shows a recurrence of a previously clipped aneurysm in the communicating segment with a fetal PComA.

The PComA and other arterial side branch occlusion is also a potential issue, particularly for patients with flow-diverters (which have a lower porosity and higher surface area of coverage than the conventional stents), which cover the ostium of the branches. While PComA occlusion with PED ranges between 27.3% to 53.3% of the cases this was not clinically significant in most cases.^21,22 In our study, we found a low rate of PComA occlusion for both cohorts (1 (5.9%) for SAC and 3 (14.3%) for PED), which were all asymptomatic (p = 0.40) and is likely explained by porosity and pore density of flow-diverting stents which preserve small branches, allow collateral supply to develop and allows the flow-demand for normal tissue perfusion to generate a pressure gradient sufficient to maintain anterograde flow through the flow-diverter wall.^5,23

The cost of endovascular interventions may also influence which technique is used and while the cost of an individual PED is higher compared to traditional devices (coils and self-expanding stents), the number of devices used per procedure is lower, resulting in a net decreased cost.⁸ In our study, we observed a median number of coils used in SAC of five, with a single stent in each case. For the PED group, only two cases (11.1%) required more than a single PED. Colby et al. performed a cost analysis of aneurysms treated by SAC and PED and found that treating aneurysms with SAC was more expensive on average by $5700.⁹ Another study performed by el-Chalouhi et al. also demonstrated that the initial treatment of large and giant aneurysms by flow diversion with PED is economically favorable compared to SAC, with savings of $6500 on average.²⁴

A factor that also comes into play is that the procedure fluoroscopy times may be shorter with flow diversion, particularly when there are multiple neighboring aneurysms that can be treated with a single device (Figure 4). In a study performed by Miller et al. there was evidence of a significant total shorter fluoroscopy time in the flow diversion group vs the SAC group for the treatment of paraclinoid segment ICA aneurysms (48 vs 69 minutes; p = 0.003).²⁵ It is worth mention that procedural time is also influenced by the physician's experience and that there is learning curve.²⁶ Reduction of procedural times will not only impact in the immediate costs of the procedure itself, but also will decrease the potential long-term risks of radiation exposure including carcinogenesis.²⁵

Aneurysms treated with flow diverters are less likely to require further intervention when compared to SAC due to their high rate of occlusion and minimal risk of recanalization once occlusion is achieved.²⁴ In our study, recanalization of a previously occluded aneurysm was recorded in two cases (11.8%) in the SAC group and none for the PED group (p = 0.10). Interestingly, in our case series we found a higher grade of re-treatment for the PED group (14.3%) compared to stent-coiling (11.8%) however, this was also not statistically significant (p = 0.81). Retreatments in the PED group (n = 3) consisted in placing additional PED, and for the SAC (n = 2), the placement of additional coils.

Interestingly, there was no evidence of rebleeding from ruptured aneurysms while placed on dual antiplatelet agents in this study (including for SAC and PED cohorts). Safety of dual antiplatelet regimens in acute SAH is still a controversial topic as it may increase the risk of bleeding; however, new evidence has supported the safety of this therapy in this setting. A recent study performed by Nagahama et al. found that the use of dual antiplatelet therapy was not associated with increased risk of hemorrhagic complications in patients with aneurysmal SAH and that there was a significantly lower risk of clinical vasospasm and delayed cerebral ischemia.²⁷

As the last point to remark, aneurysms in the PComA segment were predominantly found in the female gender (85.7%). Previous case series have suggested that there are gender differences in brain aneurysm location. A study performed by Ghods et al. found that women harbored aneurysms more frequently at the ICA, particularly at the PComA segment, in contrast to men who presented aneurysms more commonly at the anterior cerebral artery.²⁸ The lack of endothelial protection by the decline in estrogen at locations of hemodynamic stress may explain why females are more prone to aneurysms at the ICA.²⁸

Limitations

We acknowledge that our study is limited by its retrospective nature with all the inherent bias of this study design. While it is the largest study of its kind, it is comprised of a small sample size which diminishes the power to detect differences between groups. Discrepancies in the number of cases in each group, smoking status, aneurysm size, previous treatment (coiling), presence of fetal PComA and the length of follow-up can also be noted. Follow-up was significantly longer in the SAC cohort compared to the PED group. Longer follow-up periods in the PED group may show improved angiographic occlusion as one of the mechanisms of action of flow diverter therapies is the endothelialization of the device struts which occurs in a delayed fashion, and thus further studies with longer follow-up are warranted.

Conclusion

SAC and flow diversion therapy with the PED were equally effective in the treatment of communicating segment aneurysms of the ICA. There were no significant differences in terms of procedural complications and angiographic and functional outcomes.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Conflict of interest

Luis C Ascanio and Georgios A Maragkos have received a Medtronic Research Fellowship support grant. The rest of the authors have no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.