Treatment of true posterior communicating artery aneurysms: Endovascular experience in a single center

Abstract

Background and objective

The true posterior communicating artery (TPCoA) aneurysms are rare and endovascular treatment for such lesions is limited in literature.

Methods

From January 2012 to March 2017, eight TPCoA aneurysms were treated endovascularly and included in our present study. The procedural complication and outcomes were assessed.

Results

Seven of eight aneurysms (87.5%) were ruptured. Stent-assisted coiling was used in one case that a stent was deployed via PCoA-ipsilateral P2 segment. The dual-microcatheter technique was used in one case. The remaining six cases were treated by coiling alone. One patient (12.5%) suffered perioperative complication, of which a coil herniated into parent vessel during the procedure without symptomatic stroke or other adverse event after the procedure. The initial embolization results showed complete occlusion in five cases and residual neck in three. Six patients (75%) had a mean of 15-month angiographic follow-up and two of them revealed recurrence (33.3%). Clinical follow-up was available in seven patients (87.5%) and all patients showed favorable clinical outcome with mRS score 0.

Conclusion

TPCoA aneurysms are rare and challenging lesions with high rupture rate in literatures. Endovascular treatment may be a feasible alternative for TPCoA aneurysms. Primary coiling, as well as adjunctive strategies, such as stent-assisted coiling or dual catheter techniques may be considered. Further study in a larger population is necessary.

Introduction

True posterior communicating artery (TPCoA) aneurysms are defined as aneurysms arising from the PCoA itself rather than the junction of the internal carotid artery (ICA) and the PCoA.^1,2 These aneurysms represent about 1.3% of all intracranial aneurysms and 6.8% of all PCoA aneurysms.¹ Some studies suggest that this subtype of aneurysms is more prone to rupture.^1–3

Some of the authors prefer microsurgical management to endovascular treatment because of difficulty in navigation of microcatheter and potential risk of intraoperative rupture.^1,4–8 However, microsurgical clipping for such lesions also maintains challenges due to anatomic complexity.^3,4,6–10 Although advances in endovascular devices and techniques have revolutionized the management of complex aneurysms, the feasibility and efficacy of these methods in managing TPCoA aneurysms are yet to be determined. In particular, the intrinsic location of the aneurysm neck, the high prevalence of anatomical PComm variants and shear size of the vessel pose unique challenges.

Given the low incidence of TPCoA aneurysms, only limited small endovascular experiences are available in the literature.^11–19 To the best of our knowledge, only 19 total endovascularly treated cases are published in the literature with only six cases followed angiographically. The safety and efficacy of endovascular therapy for TPCoA aneurysm are still unclear based on limited cases. Therefore, in our present study, we demonstrate our experience in endovascular management of eight patients with eight TPCoA aneurysms.

Materials and methods

Patient population

From January 2012 to March 2017, 13 patients with 13 TPCoA aneurysms were diagnosed by digital subtraction angiography (DSA) in our hospital. Twelve aneurysms (92.3%) were ruptured. Of these cases, eight TPCoA aneurysms were treated endovascularly and included in our present study. Approved by the institutional review board, the medical records of these patients were reviewed to collect demographic, clinical, and radiological information. Morphological characteristics, including aneurysm size, neck size, aneurysm shape, size ratio (aneurysm size divided by parent vessel size, SR), and aspect ratio (aneurysm size divided by neck size, AR), were obtained and measured in three-dimensional (3D) angiographic images. Hunt and Hess grade was used for evaluating patients with ruptured aneurysms. Modified Rankin Scale (mRS) scores were collected for all patients before the treatment and discharge. Radiographic results were categorized using Raymond et al.²⁰ scale: complete occlusion, residual neck, and residual aneurysm. A recurrence was defined as any increase in the size of the remnant. The follow-up was performed with angiographic examination, preferably DSA. Clinical outcomes were measured by mRS at time of follow-up angiography or by telephone interview.

Endovascular treatment

Treatment modality, such as coiling alone, dual-microcatheter coiling or stent-assisted coiling, is decided by three experienced neurointerventionists after careful evaluation of patients’ clinical condition and vascular anatomical features. Most of the cases included in the present study were ruptured and only one was unruptured. For ruptured TPCoA aneurysms, coiling alone is preferred or dual-microcatheter coiling is considered if the aneurysm neck is unfavorable. Stent-assisted coiling is also considered to be used in aneurysms with unfavorable neck (neck > 4 mm or dome-neck ratio <2) and it is also considered if the vascular anatomic relation is applicable with sufficient vascular diameter and less tortuous arterial course. For some instance, the stent may deploy via ipsilateral P1-PcomA-distal ICA (retrograde stenting) or via PcomA-ipsilateral P2.

Results

Baseline characteristics

The clinical and imaging characteristics of the included cases are presented in Tables 1 and 2. Of the eight patients, there were six women and two men, with a mean age of 48.6 years (range 41–58 years). Two cases had smoking history without hypertension and six patients showed hypertension without smoking. Seven of eight aneurysms (87.5%) were ruptured and six of the ruptured aneurysms were treated within 72 h. The Hunt-Hess grade was 3 in one patient, 2 in two patients and 1 in four patients. Before treatment, mRS score was 4 in two patients, 1 in five patients and 0 in one patient.

Table 1.

The clinical characteristics of the patients with true PCoA aneurysms.

No.	Age	HTN	Smoke	Presentation	Hunt and Hess	Pre-mRS	Treatment strategy	Angiographic result	Complication		mRS at discharge	Angiographic FU/months	mRS at clinical FU/months
Case 1	40–45	Yes	No	SAH within 72 h	2	1	Coiling	RN	No		1	R/3/DSA	0/3
Case 2	50–55	No	Yes	SAH within 8 h	3	4	DMC	RN	No		1	S/6/CTA	0/23
Case 3	40–45	Yes	No	SAH within 22 h	1	4	Coiling	CO	No		0	–	0/20
Case 4	55–60	Yes	No	SAH within 24 h	2	1	Coiling	CO	Coil herniation		1	S/36/DSA	0/36
Case 5	50–55	Yes	No	SAH after 1 month	1	0	Coiling	CO	No		0	R/13.5/DSA	0/13.5
Case 6	50–55	Yes	No	SAH within 6 h	1	1	Coiling	CO	No		1	–	–
Case 7	40–45	No	Yes	Blurred vision 1 month	0	1	SAC	CO	No		0	S/26/DSA	0/26
Case 8	45–50	Yes	No	SAH within 8 h	1	1	Coiling	RN	No		1	S/5.3/DSA	0/5.3

PCoA: posterior communicating artery; F: female; M: male; HTN: hypertension; SAH: subarachnoid hemorrhage; Pre-mRS: modified Rankin Scale before treatment; FU: follow up; DMC: dual-microcatheter coiling; SAC: stent-assisted coiling; CO: complete occlusion; RN: residual neck; R: recurrent; S: stable.

Table 2.

The morphological characteristics of the true PCoA aneurysms.

No.	Location	Aneurysm size, mm	Neck size, mm	SR	AR	Daughter bleb	Dome projection	Ipsilateral P1 segment exist	Multiple aneurysms
Case 1	Left proximal PCoA	6.1	1.9	4.04	3.21	Yes	Superior-posterior	No	No
Case 2	Left proximal PCoA	5.9	2.6	1.63	2.27	No	Superior	No	No
Case 3	Right proximal PCoA	4.6	2.6	2.24	1.77	No	Inferior	Yes	No
Case 4	Left proximal PCoA	5.3	3.2	1.94	1.66	Yes	Inferior	Yes	Yes
Case 5	Left proximal PCoA	6.3	3.1	3.15	2.03	No	Superior-posterior	Yes	No
Case 6	Left proximal PCoA	3.8	2.3	1.77	1.65	Yes	Superior	Yes	No
Case 7	Left distal PCoA	10.5	7.1	4.57	1.48	No	Lateral	Yes	No
Case 8	Right proximal PCoA	2.3	1.7	1.16	1.36	Yes	Superior-posterior	Yes	No

PCoA: posterior communicating artery; SR: size ratio; AR: aspect ratio.

The mean aneurysm size, neck size, SR, and AR were 5.6 mm (range 2.3–10.5 mm), 3.1 mm (range 1.7–7.1 mm), 2.56 (range 1.16–4.57), and 1.93 (range 1.36–3.21), respectively. Three of the aneurysms showed irregular shape with daughter blebs. All seven ruptured aneurysms were located at proximal segment of PCoA and the unruptured aneurysm (case 7) was originated at distal segment of PCoA.

Procedure and complication

In the present study, one case (case 7, Figure 1) was treated by stent-assisted coiling with stent deployment from the PCoA to ipsilateral P2. The dual-microcatheter technique was used in one case which was embolized by coils via two microcatheters alternately (case 2). The remaining cases were treated with coil alone.

Figure 1.

The left internal carotid artery angiogram showed a 10.5 mm aneurysm arising from the distal segment of left PCoA (a). Left vertebral angiography with carotid compression showed the aneurysm via posterior communicating artery (b). Three-dimensional vascular reconstruction showed the aneurysm (c). The stent-microcatheter was navigated from left ICA-PCoA and delivered into PCA. Another microcatheter was introduced over micro-guidewire from left vertebral artery and navigated into the aneurysm (d). Final angiogram showed the aneurysm was complete occlusion by stent-assisted coiling (e). The white arrows showed the two ends of the stent (f). The aneurysm showed complete occlusion with PCoA patency at 26-month angiographic follow-up (g).

One perioperative complication occurred (12.5%, case 4) with coil herniation to the parent vessel, though no symptomatic stroke resulted. The initial embolization results showed complete occlusion in five cases (cases 3, 4, 5, 6, and 7) and residual neck in three (cases 1, 2, and 8). All of the patients showed good recovery at discharge (mRS 1 in five patients and 0 in three patients).

Outcome

In our study, six patients (75%; cases 1, 2, 4, 5, 7, and 8) had a mean of 15-month angiographic follow-up (range, 3–36 months) and two of them revealed recurrence (33.3%; case 1 and case 5). Angiographic follow-up of these two cases showed coil compactions and both cases displayed an increasing percentage of contrast filling the aneurysmal neck. No retreatment was performed in the cases because of the technical difficulty in endovascular performance and the stable status based on results from additional follow-ups. Clinical follow-up was available in seven patients (87.5%) at a mean of 17.5 months and all patients showed favorable clinical outcome with mRS score 0.

Illustrative cases

Case 7

This 41-year-old man presented with blurred vision and left oculomotor nerve palsy for a month. DSA showed a 10.5 mm unruptured aneurysm arising from the distal segment of left PCoA (Figure 1). The aneurysm neck was 7.1 mm with dome-neck ratio 1.48 and the parent artery diameter was 2.3 mm. Three-dimensional angiography showed that the initiation of the PCoA was less torturous. Therefore, stent-assisted coiling was used in this case. Considering the small size of the parent vessel (PCoA was 2.3 mm), we thought there might be difficulty in navigating two micro-catheters in the PCoA following the same route of ICA-PCoA-PCA. Therefore, after general anesthesia and bilateral femoral sheaths placement, two guiding catheters were introduced respectively into left ICA and left vertebral artery. The stent-microcatheter was navigated from left ICA-PCoA and delivered into PCA. Then, the microcatheter with proper tip shape was introduced over micro-guidewire from left vertebral artery and navigated into the aneurysm. After sufficient coil embolization, an Enterprise stent (Cordis Neurovascular, Miami, FL, USA) was deployed from the P2 segment to the PCoA with post-intervention angiography showing complete occlusion of the aneurysm. Enterprise is a self-expandable and retractable device. This stent could be used in the vessel from 2.5 to 4.5 mm and the PCoA is about 2.3 mm in this case. Post-procedure course was uneventful. The aneurysm showed complete occlusion with PCoA patency at 26-month angiographic follow-up.

Discussion

TPCoA aneurysms, as aneurysms originating from PCoA itself, are extremely rare.¹ The literature on endovascular management of such lesions is limited and the angiographic follow-up rate is considerably lower (Table 3).^11–19 We retrospectively reviewed a series of eight TPCoA aneurysms in our database to assess the safety and efficacy of endovascular treatment in such cases. In this study, most of the treated TPCoA aneurysms were ruptured (7/8, 85.7%). Endovascular treatment is a feasible alternative for TPCoA aneurysms with careful evaluation before the procedure. Adjunctive techniques, such as stent-assisted coiling, could be considered for elective cases.

Table 3.

The published cases of true PCoA aneurysm under endovascular treatment.

Author(s) and Reference no.	Sample size	Rupture/ unrupture	Operation	Complication	Angiographic outcome	Clinical outcome
Kubo et al.16	1	1/0	1 coiling	None	3-month DSA/ complete obliteration	Full recovery
Meguro et al.15	1	1/0	1 coiling	Multiple cerebral infarctions caused by vasospasm	7-month DSA/ complete obliteration	Full recovery
Park et al.14	1	0/1	1 coiling	None	12-month DSA/ stable	mRS 0
Guo et al.11	3	3/0	2 coiling	None	–	–
Munarriz et al.12	1	0/1	1 coiling	None	6-month MRA/ stable	Marked improvement
Almeida-Perez et al.17	1	0/1	1 coiling	None	–	–
Yang et al.13	9	9/0	8 coiling/ 1 SAC	None	–	GOS five in all cases
Mitsuhashi et al.18	1	1/0	1 PAO	None	1-month DSA/ complete obliteration	Well recovery
Yang et al.19	1	1/0	1 SAC	None	9-month DSA/ stable	mRS 0
Total	19	16/3	15 coiling/ 2 SAC/ 1 PAO	1 ischemic event	6 cases had FU with stable or complete occlusion	15 cases had FU with favorable outcome

SAC: stent-assisted coiling; PAO: parent artery occlusion; FU: follow-up.

PCoA aneurysms, traditionally arising at the junction of ICA and PCoA, account for approximately 25% of all intracranial aneurysms.³ It is reported that PCoA aneurysms are more likely to rupture than aneurysms at other locations.^3,21 For the TPCoA aneurysms, the rupture risk is reported to be even higher (44 of 49, 89.8%).^2,3 Consistent with the limited literature, seven of eight cases (85.7%) in our study were ruptured. Successful and effective managements of these patients are crucial in preventing against re-rupture and subsequent mortality.

Nowadays, endovascular treatment has been widely used in management of intracranial aneurysms and such strategy in managing TPCoA aneurysms is reported in a few case studies.^11–19 Munarriz et al.¹² reported a case of successful endovascular coiling of a TPCoA aneurysm with subsequent angiographic stability. Another report from Guo et al.¹¹ showed three such aneurysms, of which two were treated endovascularly without complications. However, the angiographic outcomes were unknown from their data. Parent artery occlusion with coils was also reported as an endovascular alternative in a case report.¹⁸ A study¹³ with nine ruptured TPCoA aneurysms was published. In their study, seven cases were completely embolized and two cases were near-completely occluded after initial treatment. All the patients showed good clinical outcome; however, their angiographic outcomes were unknown. In addition, the group reported a case treated by stent-assisted coiling though no details or images were available for reference and guidance.

As reported in the literature, microsurgical clipping for TPCoA aneurysms is traditionally preferred.^1,4 However, the neurovascular anatomy of the PCoA is complex.^3,4,9,10 The perforating arteries arising from PCoA supply the optic chiasm, oculomotor nerve, anterior thalamus, hypothalamus, and internal capsule. Therefore, care must be taken to avoid compromising the blood flow to PCoA during clipping of such lesions. Additionally, the oculomotor nerve typically comes laterally to PCoA and preservation of such nerve is also important.^10,22 Thus, microsurgical clipping of TPCoA aneurysms is still full of challenges and the potential risk of microsurgical clipping should be evaluated carefully.^{5,6,8,9,23,24} Endovascular treatment should be considered as an alternative in aneurysms not amenable to microsurgical clipping, patients with high anesthesia/surgical risk or in cases with endovascularly favorable anatomy. A thorough understanding of aneurysm location and configuration is essential in successful treatment of these lesions. With the aid of 3D rotational angiography, preoperative aneurysm anatomy could be accurately evaluated, making it ideal for microcatheter navigation and embolization. Other authors noted the difficulty in navigating the microcatheter into these aneurysms, especially those with inferior dome configuration which lend themselves to higher intraoperative rupture risk.^1,12 In our series, the microcatheter could be successfully introduced after appropriately tip shaping and no intraoperative rupture occurred in our cases. As with any other location, wide-neck aneurysms can be challenging and require adjunctive techniques such as stent-assisted coiling or dual microcatheter guidance. However, for TPCoA aneurysms, the vascular anatomic relationship is much more complex and those techniques may not be applicable to every case. Therefore, it may be difficult to achieve dense packing for some of the cases and therefore the risk of coil herniation may be higher as demonstrated in our series. Subsequently, the recurrence rate of TPCoA aneurysm without complete occlusion or dense packing will be higher. That may be the reason why the recurrence rate was 33.3% in our study. No retreatment was performed in our two recurrent cases because of the technical difficulty in endovascular performance and the stable status based on results from additional follow-ups. Importantly, in ruptured cased with SAH-treated endovascularly, there was no re-rupture events and 87.5% of these patients had a favorable clinical outcome. Therefore, endovascular treatment is still an effective therapy for patients with TPCoA aneurysms.

Young et al.²⁵ reported two PCoA aneurysms treated with retrograde stent placement from the terminal ICA to PCoA. Yang et al.¹⁹ showed a stent-assisted coiling case with the proximal end of the stent protruded into the fetal PCA. It seems to be a good alternative for TPCoA aneurysms treatment. However, as the author indicated, such technique should be reserved for those cases with specific vascular anatomy. In our study, we demonstrated a case treated by stent-assisted coiling. Although this endovascular strategy is successful for our case, some anatomic requirements in P1, P2, PCoA, and ICA were needed before stent-assisted coiling. Briefly, in order to deploy the stent, the micro-catheter needs to be navigated via the PCoA. In some circumstances, the origin curve of the PCoA is too sharp to navigate the micro-catheter. Therefore, the vascular anatomy needs to be considered before the stent-assisted coiling. What’s more, the new stent device, such as Neuroform Atlas or LVIS Jr., may be a better choice for stent-assisted coiling of wide necked TPCoA aneurysm. The procedure may be much easier as the newer devices could be delivered through a lower profile micro-catheter.²⁶ Meanwhile, most of the TPCoA aneurysms are ruptured and anti-platelet medication may increase potential risk of hemorrhage in treatment with stent. The safety and efficacy of this treatment strategy need to be assessed with larger population.

The main limitation of present study is that the sample size is small. Although, the efficacy of endovascular treatment of TPCoA aneurysms could not be concluded with such limited angiographic follow-up data, endovascular treatment may be still effective in preventing re-rupture of ruptured TPCoA aneurysm and 87.5% patients showed favorable clinical outcome. The rupture risk of TPCoA aneurysms should be also validated by a larger sample study. There are some other limitations, such as retrospective design, selection bias, treatment bias and lack of a comparison group of surgical clipping. Multicenter and high-volume analysis of embolization treatment for TPCoA aneurysm is still needed in the future.

Conclusion

TPCoA aneurysms are rare and challenging lesions with high rupture rate in literatures. Endovascular treatment may be a feasible alternative for TPCoA aneurysms. Primary coiling, as well as adjunctive strategies, such as stent-assisted coiling or dual catheter techniques may be considered. Further study in a larger population is necessary.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors disclosed receipt of the following financial support for the research, authorship and/or publication of this article: supported by National Key Research and Development Plan of China (grant number: 2016YFC1300800), the National Natural Science Foundation of China (grant numbers: 81801156, 81801158, 81471167 and 81671139), the Special Research Project for Capital Health Development (grant number: 2018-4-1077) and Beijing Hospitals Authority Youth Programme, code: QML20190503.