Stand-alone coil embolization of anterior communicating artery aneurysms: Efficacy and technical issues

Abstract

Objective

We report our experience with endovascular coiling of anterior communicating artery aneurysms with special consideration of angiographic and clinical outcomes and periprocedural complications.

Materials and methods

The analysis included treatment results of 28 patients with ruptured and unruptured aneurysms. The aneurysm size ranged from 1.8 to 9.8 mm (mean 5.2, SD 1.7). Clinical examinations with the use of modified Rankin Score and angiographic outcomes were evaluated initially post-embolization and at a minimum follow-up of six months.

Results

Initial post-treatment complete and near-complete aneurysm occlusion was achieved in 27 (96%) cases and incomplete occlusion in one (4%) case. Imaging follow-up, performed in 15 (53.6%) patients, showed no change in the degree of occlusion in 11 (73%), coil compaction in one (7%) and progressive occlusion in three (20%) patients. Three (20%) patients underwent a second coil embolization. The procedure-related severe morbidity and mortality rate was 6.4% (2/31). Coil prolapse was present in one (3.2%) case and intraprocedural aneurysm rupture in three (9.6%) cases. The clinical follow-up evaluation achieved in 19 (67.9%) patients showed no change in 17 (89.5%) patients and improvement in two (10.5%) patients.

Conclusions

Although the efficacy of coil embolization of anterior communicating artery aneurysms is unquestionable and the procedure-related complications are acceptable, they should not be neglected. Further investigations are needed to better understand protective factors, as well as to establish unequivocally appropriate management strategy of these complications.

Introduction

The anterior communicating artery (AComA) is one of the most common sites of intracranial aneurysms.^1,2 The endovascular approach with favorable long-term angiographic outcome offers an acceptable alternative to traditional microsurgical clipping of these aneurysms, although the ability to control and track the therapeutic devices in this specific location is restricted by the vessel tortuosity and the acute angle of the aneurysm.^2–6 Despite its acknowledged effectiveness, the endovascular therapy is not complication free even at high-volume, experienced centers.^7,8 Since the incidence of adverse events is low,⁷ the management strategy is often based on personal, anecdotal experience and a limited number of case series. The aim of the current study is to report our experience with the endovascular coiling of AComA aneurysms with special regard to radiographic and clinical outcomes and procedure-related complications.

Materials and methods

Patient population

Between April 2008 and December 2014, 71 patients harboring AComA aneurysms were treated at our center via endovascular approach. Of these, 28 patients underwent the standard coil embolization (stand-alone coiling). There were 14 (50%) females and 14 (50%) males. The patients’ ages varied from 32 to 72 years (mean 51.8 ± 11.04).

Ten (35.7%) patients of the analyzed group harbored unruptured aneurysms and 18 (64.2%) presented with subarachnoid hemorrhage (SAH). Of these patients, 14 were treated within three days of rupture and in three patients the treatment was postponed to 10–14 days after the onset of symptoms of SAH because of initially delayed diagnosis.

One patient underwent endovascular coiling of the aneurysm remnant eight years after incomplete clip ligation of a ruptured aneurysm. Except for this patient and another one after incomplete microsurgical clipping of an incidentally found aneurysm, the remaining 26 patients included in the present study were treated for the first time via endovascular approach.

For this retrospective study Ethics Committee approval as well as informed patient consents were waived.

Endovascular technique

Since all the aneurysms were depicted by computed tomography (CT) angiography at admission, both conventional and rotational digital subtraction angiographies (DSAs) were performed in every case to evaluate accurately aneurysmal configuration, neck size and aneurysm width and height. All the procedures were performed by experienced interventional radiologists always after neurosurgical consultations. The patients were treated under general anesthesia. Antiplatelet premedication consisting of a 75 mg loading dose of acetylsalicylic acid was performed every single day for five days before coiling in case of patients harboring unruptured aneurysms and several hours before endovascular procedure in patients after SAH. Following selective catheterization of the aneurysm lumen, the aneurysm was compacted with Guglielmi Detachable Coils (GDC; Boston Scientific Corporation, Natick, MA, USA). Remodeling techniques such as balloons or stents were never used. Once it was technically feasible, an attempt was made to achieve complete occlusion in the first treatment session. During the procedures heparinized saline was continuously infused into the arterial line. After embolization, the patient was transferred to the intensive care unit for clinical observation and monitoring of medical parameters. At that time, systemic heparin 15,000 IU for the next 24 hours was administered intravenously to raise the activated partial thromboplastin time two to three times above normal values. Patients with unruptured aneurysms after uncomplicated treatment were typically discharged from the hospital on postoperative day 3. Antiplatelet therapy consisting of 75 mg acetylsalicylic acid was applied postoperatively every day with the intention to be administered for the rest of the patient’s life.

Angiographic and clinical analysis

A control angiography was obtained immediately after the embolization and at a minimum follow-up of six months. Anatomic results were evaluated using three-class classification according to Raymond et al. (i.e. complete obliteration, residual neck and residual aneurysm).⁹ The lack of contrast filling within the entire aneurysm and the residual filling in the aneurysm neck were categorized as complete and near-complete occlusion, respectively, whereas incomplete occlusion was defined as any opacification of the aneurysm sac. In cases of complete aneurysm obliteration at control angiogram performed at a minimum of six months after coiling the patient was not followed-up any longer, except for selected cases (e.g. endovascular treatment of accompanying cerebral aneurysms). Recanalization was defined as any increase in aneurysmal filling at follow-up. Once there was enough space for placement of an additional coil, the retreatment was performed.

Regarding clinical evaluation, modified Rankin Scale (mRS) scores were recorded at patient admission to the hospital, at patient discharge from the hospital and during the last angiographic follow-up period. Patients who did not undergo control angiography were interviewed by telephone if it was possible.

Detailed patient characteristics as well as the results are presented in Table 1.

Table 1.

Patient characteristics and treatment results.

No.	Age/sex	Clinical presentation	Aneurysm size (mm)	Dome-to-neck ratio	Instant occlusion	Technical complication	mRS at discharge
1	43/F	SAH (III H-H)	6.2	1.52	Complete	Intraoperative aneurysm rupture	5
2	61/F	SAH (IV H-H)	3.0	1.20	Complete	Coil prolapse into parent artery	5
3	56/F	SAH (III H-H)	4.8	1.34	Complete	None	0
4	44/M	SAH (II H-H)	5.4	1.35	Incomplete	Intraoperative aneurysm rupture	0
5	50/M	SAH (III H-H)	9.8	2.64	Near-complete	None	0
6	43/F	SAH (III H-H)	3.6	1.51	Complete	None	0
7	39/M	SAH (II H-H)	3.2	2.25	Complete	None	0
8	54/M	SAH (II H-H)	7.4	1.47	Complete	None	0
9	59/M	SAH (II H-H)	5.2	1.54	Complete	None	1
10	45/F	SAH (III H-H)	5.9	1.08	Complete	None	3
11	57/F	SAH (III H-H)	3.3	1.03	Complete	None	1
12	34/F	SAH (I H-H)	5.4	1.86	Complete	None	0
13	46/M	SAH (I H-H)	4.9	1.38	Complete	None	0
14	63/M	SAH (III H-H)	6.9	1.18	Complete	None	0
15	42/F	SAH (III H-H)	4.3	1.45	Complete	None	6
16	64/M	SAH (III H-H)	3.9	1.20	Complete	None	0
17	50/M	Incidental	1.8	0.74	Near-complete	None	0
18	55/M	Incidental	5.9	1.47	Complete	None	0
19	32/M	Incidental	4.8	1.40	Near-complete	None	0
20	68/M	Incidental	8.3	1.29	Complete	None	0
21	40/F	Incidental	5.0	1.43	Complete	Catheter-induced vasospasm	0
22	72/M	Incidental	6.0	2.00	Complete	None	0
23	69/F	Incidental	6.4	1.32	Near-complete	Intraoperative aneurysm rupture	6
24	58/F	Incidental	5.9	1.80	Complete	None	0
25	68/F	SAH (I H-H)	4.5	1.45	Complete	None	0
26	40/F	Incidental	2.6	0.80	Near-complete	None	0
27	57/M	SAH (II H-H)	5.7	2.57	Complete	None	0
28	42/F	Incidental	6.5	2.54	Near-complete	None	0

SAH: subarachnoid hemorrhage, H-H: Hunt & Hess grade at the time of treatment; mRS: modified Rankin Score; M: male; F: female.

Statistical analysis

Quantitative variables were expressed as mean ± standard deviation. The unpaired t-test and chi-square test were used to compare the ruptured and unruptured aneurysms. The pre- and post-treatment mRS scores were assessed by the non-parametric Wilcoxon test. Statistical significance was set at p < 0.05.

Results

Angiographic results and retreatment

The aneurysm size ranged from 1.8 to 9.8 mm (mean 5.2 ± 1.7). There were seven aneurysms with narrow necks and 21 wide-neck aneurysms, defined as these with a maximal aneurysm neck diameter ≥ 4 mm and/or dome-to-neck ratio < 1.5.

There was no significant difference between the unruptured group and the ruptured group in terms of aneurysm size (5.3 ± 1.89 vs. 5.18 ± 1.7,p = 0.866), maximal aneurysm neck width (3.75 ± 1.17 vs. 3.71 ± 0.99, p = 0.92) and dome-to-neck ratio (1.48 ± 0.53 vs. 1.56 ± 0.47, p = 0.697).

Instant post-embolization angiogram revealed a complete aneurysm occlusion in 21 (75%) cases. A near-complete aneurysm occlusion was performed in six cases (21%), and incomplete occlusion in one (4%) patient. The primary inadequate occlusion of aneurysms resulted from intraprocedural aneurysm rupture in two cases, massive vasospasm associated with SAH in one case and difficulties of accessing the aneurysm for coiling in the patient who had undergone previous clipping. The three remaining aneurysms were not amenable to complete embolization as the residual spaces were smaller than 2 mm and it was impossible to occlude them with the shortest available coil.

Angiographic follow-up was achieved in 15 (53.6%) patients and ranged from six to 38 months, with a mean of 17.7 months. In 11 (73%) cases no change in the degree of occlusion at initial angiographic follow-up was observed. Recanalization rate was 7% (1/15). In three (20%) cases progressive occlusion was revealed (Figure 1). The illustrative example of complete angiographic occlusion of an AcomA aneurysm is presented in Figure 2. There was one (6.6%) patient with incomplete and three (20%) patients with near-complete angiographic occlusion at initial angiographic follow-up. Of these, three (20%) were retreated by endovascular coil embolization therapy without any procedure-related complications, whereas the remaining one patient was followed with angiography.

Figure 1.

Angiographic results of endovascular coiling of anterior communicating aneurysms achieved at minimum six-month follow-up.

Figure 2.

58-year-old female patient presented with unruptured anterior communicating artery (AComA) aneurysm. A: Working projection of the aneurysm. B: Control angiography showed the complete occlusion of the aneurysm with the preservation of AComA. C: Follow-up angiogram showed that there is no evidence of recanalization after 20 months.

Clinical results and complications

Adverse events such as intraoperative aneurysmal rupture, coil protrusion or catheter-induced vasospasm related to endovascular coiling were encountered in five (16.1%) of the 31 procedures. The complication rate in the unruptured group was not significantly higher than that in the ruptured group (p = 0.726). The procedure-related severe morbidity and mortality rate of 6.4% (2/31) was associated exclusively with events of intraprocedural bleeding of aneurysm. In one patient who initially presented with SAH perforation of the aneurysm occurred during insertion of the last seventh coil. Total occlusion of the lesion was achieved and the completion angiogram was within normal limits. Urgently performed CT scan revealed massive intraventricular hemorrhage and an ipsilateral anterior cerebral artery infarction. The patient developed a hemiplegia and stayed bedridden. Another patient with initially unruptured aneurysm suffered from microcatheter-induced intraoperative aneurysm perforation. Although near-complete occlusion was immediately achieved, the patient experienced massive intraventricular hemorrhage with poor clinical outcome and subsequent death.

Except for these two cases above, one patient experienced intraprocedural aneurysm rupture without any adverse neurological consequences. The other clinically silent complication was catheter-induced vasospasm that withdrew after local administration of a vasodilator.

There was also one case of neurological deterioration not related to the embolization procedure. The patient expired as a consequence of delayed cerebral ischemia associated with SAH.

Another patient in acute phase of SAH underwent endovascular coiling complicated by coil protrusion into the parent artery. As there was no flow-limiting stenosis at post-procedure angiography, it was decided to leave the herniated coil in place. Control angiogram performed 13 days later showed total arterial patency at the level of the coil displacement (Figure 3). The patient improved from mRS grade 5 to 4 during the 48-month follow-up.

Figure 3.

61-year-old female patient presented with ruptured anterior communicating artery aneurysm. A: Nonsubtracted projection revealed prolapsed coil into parent artery. B: Control angiography performed 13 days after coiling showed no evidence of parent vessel stenosis.

The preoperative mRS score was 0 in 10 patients, 1 in three patients, 2 in six patients, and 4 in eight patients. The mRS score evaluated at discharge from hospital is presented in Table 1. Excluding the patient who expired from complications associated with SAH, the statistical analysis showed a significant difference between preoperative mRS scores and mRS scores assessed at discharge from the hospital (0.78 ± 1.76 vs. 1.85 ± 1.79, p = 0.007).

Clinical follow-up was achieved in 19 (67.9%) patients and performed at 6–60 months (mean 23.7 months) after coiling. The analysis showed no change in clinical status in 17 (89.5%) patients. None of the patients deteriorated. Following intensive rehabilitation in two (10.5%) patients, who were initially after SAH, the neurological disability decreased from 5 to 0 mRS and from 5 to 2 mRS, respectively.

Discussion

Since the introduction of Guglielmi detachable coils in 1991, endovascular therapy has been increasingly common and in many centers, including our institution, embolization is currently a first-line treatment of all intracranial aneurysms.^3,10,11 In the next 20 years an evolution in the coiling technology occurred.¹² At that time, subsequent guide catheters and microcatheters had been introduced to the clinical practice and at present more than eight sorts of catheters and 10 sorts of microcatheters are available on the market.^12,13 Each guide catheter or microcatheter has its pros and cons, especially in terms of size, flexibility, shapeability, visibility on fluoroscopy, steerability, as well as operator preferences and the optimal guide catheter or microcatheter may vary depending on the situation.^12,13 As far as coils are concerned, numerous coils varying in size, shape, design, stiffness, presence or absence of “bioactive” material, and detachment systems have been developed to increase packing density in an effort to reduce recanalization rates.¹³ A randomized, controlled trial performed in 2011 showed that augmentation of platinum coils with bioactive materials may lower the recanalization rate.¹⁴ Moreover, to support deployed coils adjunctive devices, such as balloons and self-expanding stents, are applied and they are mainly used in the endovascular treatment of wide-necked intracranial aneurysms that are difficult to treat with coiling alone.¹³

Regarding the AComA aneurysms, the mean rate of immediate and long-term complete and near-complete angiographic occlusion following endovascular coiling is reported to be 88% and 85%, respectively.³ The higher initial complete and near-complete obliteration rate of 96.4% achieved in the current study results from the fact that we attempt to occlude aneurysms totally, only if it is technically possible. This is particularly important in the setting of patients after SAH because the degree of initial aneurysm occlusion is a strong predictor of the risk of subsequent rupture, as demonstrated in the Cerebral Aneurysm Rerupture After Treatment (CARAT) study.¹⁵ Moreover, the initial obliteration degree affects aneurysmal recurrence.¹⁶ According to some authors, however, the aggressiveness of coiling to achieve tighter packing may lead to higher rate of intraoperative rupture (IOR), which is thought to be the most feared adverse event of the endovascular aneurysm repair.^17,18

IOR is demonstrated during angiography as contrast medium extravasation and confirmed by brain CT. The overall incidence of IOR ranges between 2% and 5%¹⁷ and this complication may happen not only when coils are packed inside an aneurysm but also during advancement of a catheter into an aneurysm dome.^3,19 Aneurysms that have already bled, small aneurysms and those located in the AComA are likely to be at higher risk for IOR.¹⁷ In the present study the overall IOR rate of 9.7% (3/31) is comparatively high. It should be noted, however, that the percentage of IOR caused by coil perforations was only 3.2% (1/31) despite our tendency to achieve complete obliteration of coiled aneurysms. On the other hand, we always leave the residual contrast filling in the aneurysm neck if there is not enough space to safely insert an additional coil. Thus, we attempt not to allow the aneurysm to be overpacked with coils. Moreover, we also keep in mind that in case of incompletely occluded aneurysm there is always a possibility of progressive thrombosis leading to complete obliteration. It is demonstrated that aneurysms <10 mm in size with small neck diameters (≤4 mm) and initial high packing density (>30%) are especially prone to this favorable phenomenon.²⁰ Unfortunately, the trend of progressive thrombosis of incompletely treated aneurysms is not common in AComA compared with other locations.¹¹

Prevention seems to be the key for reducing morbidity and mortality related to IOR. In addition to avoiding overpacking aneurysms, careful control of microcatheters and coils may also potentially lower the risk of IOR.⁶ However, it should always be kept in mind that despite increasing clinical experiences, the endovascular treatment still has an inherent risk of IOR.¹⁸ One should remember that the instant placement of additional coils, which is acknowledged to be the treatment of choice in case of IOR, may not prevent a massive intracranial hemorrhage with severe neurological consequences leading sometimes to patient death, as was shown in our study.²¹

Another technical complication of aneurysm coiling that cannot be negligible is coil material displacement into the parent artery. The herniated coils may cause thromboembolic incidents with the variety of negative clinical consequences.²² As wide-neck intracranial aneurysms are particularly susceptible to this complication, they are commonly treated with the use of the above-mentioned advanced adjuvant devices, such as balloons and stents.²³ Apparently, the careful technique of coil insertion into the aneurysm sac also plays a role in decreasing the incidence of coil prolapse.²² Although there is no standard management strategy for this potentially serious complication, it is widely agreed that in case of a significant degree of coil displacement, i.e. stretching, fracture and distal migration, radical treatment in the form of salvage stent fixation, endovascular retrieval or microsurgical coil removal should be employed.^22,24 It is not insignificant, however, that extraction and mechanical stabilization of intravascular coils harbor a certain risk of complications that may sometimes outweigh the expected benefits.^11,24 Johnson et al. described four cases of coil prolapse during AComA aneurysm embolization procedures.¹¹ In one patient an attempt to secure the coil with stent reconstruction ended fatally. The three remaining patients with coil protrusions were left without intervention and there was no negative long-term sequelae.¹¹ Similarly, Finitsis et al. did not retrieve the prolapsed coil into the AComA and to decrease the risk of intravascular thrombosis they put the patient into anticoagulation with favorable clinical outcome.¹⁰ We also decided to treat the patient harboring a protruded coil conservatively, although, our strategy was based on only a few reported cases of coil herniation during endovascular repair of AcomA aneurysms. We expected that a small amount of protruded coil would be incorporated into the vessel wall by endothelialization with no clinical consequences, as reported by Ding et al.²⁴ In our case of coil prolapse the control angiography performed 13 days after the procedure did not reveal any flow-limiting stenosis. Since the patient was initially after SAH she underwent intensive rehabilitation and improved from mRS grade 5 to 2 within the 48-month clinical follow-up.

Thus, this study agrees with others and proposes that in the setting of minor coil displacements that may be classified as protrusion or prolapse, without angiographic evidence of flow limitation or thrombus accumulation, conservative treatment with antiplatelet and anticoagulation therapy is likely to be most appropriate.

The limitation of the current study is its retrospective and observational character. Moreover, there are a limited number of the cases, a disproportion between ruptured and unruptured aneurysms and a patient-selection bias, as all the cases reported in this series were from a single institution.

Conclusions

The efficacy of coil embolization of AComA aneurysms is satisfactory. Although the procedure-related adverse events are acceptable, they should not be neglected even at experienced centers.

Further investigations are needed to better understand protective factors, as well as to establish unequivocally appropriate management strategy of accompanying complications with the ultimate aim of minimizing the risk of patient injury.

Acknowledgment

This study was conducted and written with ethical adherence by all authors.

Funding

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

Conflict of interest

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