“Two-coil technique” for embolization of small internal carotid artery aneurysms incorporating the origin of the anterior choroidal artery

Abstract

Purpose

The purpose of this article is to evaluate the efficacy, safety and stability of the “two-coil technique.”

Materials and methods

We evaluated a single-center experience by using a two-coil technique, which is a variation of the multiple-microcatheter technique in the treatment of a small internal carotid artery aneurysm with its sac incorporated with the origin of the anterior choroidal artery. Six consecutive patients with small ICA aneurysms with its sac incorporated with origin of the anterior choroidal artery and treated with the two-coil technique were included in this study. We finished the embolization with only two coils introduced via two different microcatheters without any other device assistance in all cases. Embolization status was determined at immediate postoperative and follow-up angiography after six months.

Results

The two-coil technique was technically successful in five of six cases; one case was converted to surgical clipping because of persistent occlusion of the anterior choroidal artery after several attempts. On follow-up study, all five cases showed stable occlusion status without recanalization or residual aneurysm.

Conclusions

The two-coil technique has potential to be used for coiling small aneurysms, particularly where there is an important branch incorporated into the sac or neck of the aneurysm.

Introduction

Even though Kim et al. have reported their experience of successful endovascular management of aneurysms with a branch incorporated into the sac applying with or without various assisted techniques,¹ an aneurysm with an incorporated branching vessel at the sac is generally considered not a good indication for endovascular coiling because of its possibility of the incorporated branch occlusion.² Furthermore, conventional endovascular coiling could be contraindicated when the incorporated branching vessel is too small to be spared with stent assistance and the anticipated clinical consequences of orificial occlusion seem critical. A typical situation is a distal internal carotid artery (ICA) aneurysm with its sac incorporated with the origin of the anterior choroidal artery (AChA).³

We devised a modified technique from the well-known “double microcatheter technique.” The modified technique, coined the “two-coil technique,” facilitates the technical safety of the conventional double-microcatheter technique by taking full advantage of the merits of detachable embolization coils. The basic idea of this modified technique is finishing the embolization procedure using only two coils. The two coils are introduced into the sac through two different microcatheters as we do with the double-microcatheter technique. Different from the double-microcatheter technique,^4–6 the two coils are not detached until the end of the procedure in this modified technique. Since both coils are not detached, they can be removed, repositioned, or exchanged with other type of coils if the result of coil packing is not satisfactory or if there is any flow abnormality of the branching vessel by compromise of the branch os. There would be no difference between the double-microcatheter technique and the current two-coil technique if the procedure could be finished only with two coils. If the packing result is not satisfactory with the two coils, we usually detach one of the coils for additional coil packing in a double-microcatheter technique. In the two-coil technique, however, one of the coils will be retrieved for a different-size coil (usually a longer coil) repeatedly until we can achieve a satisfactory embolization result. Since the coils are not detached, one could stay safe until both of the coils are detached completely.

Since the number of coils is limited to just two, we thought that this technique can effectively be applied in case of a small aneurysm with a critical branching vessel incorporated into its sac. We report this case series to present our endovascular coiling experience of small distal ICA aneurysms with their sacs incorporated with the origin of the AChA applying our modified double-microcatheter technique, the two-coil technique.

Materials and methods

This retrospective study was approved by our institutional review board and informed consent was waived. By review of our neurointerventional procedure database, we identified six consecutive patients with six small ICA aneurysms with sacs incorporated with the origin of the AChA and treated with a two-coil technique as the initial treatment method for endovascular treatment of cerebral aneurysms at our institution between January 2011 and May 2015. There were three men and three women, with a mean age of 49.8 ± 10.0 years (median, 51.5 years; range, 34–64 years). All included cases were incidentally detected unruptured aneurysms. The median of the aneurysm size in maximum dimension was 3.8 mm (range, 3.7–3.9) and that of the neck width was 2.85 mm (range, 2.1–3.5).

Occurrence of any intraprocedural event, such as rupture, thrombosis (acute platelet aggregation, thrombotic occlusion, or distal thromboembolism), and parent or branch artery occlusion was analyzed. Initial occlusion degree was classified as complete (no definite contrast filling with dense packing of aneurysm) or residual (any contrast filling in dome or neck) on the final control angiogram. Technical success, defined as completion of the procedure without any procedural conversion into either endovascular or surgical treatment, was evaluated.

Immediate imaging follow-ups were performed using time-of-flight magnetic resonance angiography (TOF MRA) and diffusion-weighted MR imaging on the day after the procedure to evaluate any ischemic events and the occlusion status of the embolized aneurysm. Clinical follow-up was scheduled one month and six months after discharge, and annually thereafter. Imaging follow-up was performed via TOF MRA six months after discharge and annually or biannually thereafter based on the occlusion status of the coil-embolized aneurysm and patency of the parent and AChA.

Endovascular procedure

Patients received dual antiplatelet medications (aspirin 100 mg, qd; clopidogrel 75 mg, qd) at least five days prior to the procedure. Following general anesthesia and placement of a 6-Fr. Envoy guiding catheter (Cordis, Miami Lakes, FL, USA), a bolus of heparin was administered to achieve the activated clotting time twice that of the baseline (60–70 IU/kg). An additional dose (1000 IU/h) of heparin was given if the procedure was prolonged.

After a pre- or steam-shaped microcatheter was navigated into the aneurysm sac, the first (framing) coil was introduced. When about one-third of the total length of the coil was inserted, we placed another microcatheter for the second (finishing) coil. In some situations two microcatheters were placed in the parent artery near the aneurysm sac prior to advancing the first microcatheter into the sac, followed by inserting the second microcatheter in the sac. In the selection or shaping of the second microcatheter tip, the action or performance of the first microcatheter tip was considered for better shaping and placement of the second microcatheter tip. Both microcatheters were inserted in parallel fashion via a single hemostatic valve (Guardian; Zerusa Limited, Galway, Ireland).⁷

With the first coil partially inserted, one or two loops of the second coil were inserted into the frame coil mesh to guide the successive introduction of the rest of the first coil. The remaining portion of the first coil was then packed into the sac. Finally, the main part of the second coil was packed into the sac to complete the procedure. When the packing status seemed insufficient, the second coil was replaced with a longer one. In some cases, replacement of both coils was needed to achieve satisfactory coiling results. On the completion of packing, we detached the coils after confirming the patency of the AChA on control angiography obtained 10 to 15 minutes after placement. If any flow abnormality in the AChA was noted, the coils were adjusted or removed. If any thrombosis was suspected at the coil-parent artery interface, an intravenous loading dose (0.4 µg/kg/min for 30 minutes) of tirofiban (Aggrastat; Merck, West Point, PA, USA) was administered before removal of the coils. If there was partial or no response to tirofiban, the coils were removed.

If the technique turned out not to be feasible, we considered other embolization techniques or aborted the procedure.

Results

Immediate post-procedure results

A summary of the six patients with aneurysms treated with the two-coil technique is shown in Table 1. The two-coil technique procedure was technically successful in five of six cases (Figure 1), the exception being patient No. 5 of Table 1. In the failed case, we decided to convert to surgical clipping we could not pack the coils in the sac without occlusion of the AChA orifice even after several attempts of coil repositioning (Figure 2).

Table 1.

Summary of the six patients with an aneurysm treated with the “two-coil technique.”

Patient no.	Age (years)	Sex	Aneurysm size (mm)	Aneurysm neck (mm)	Number of coils tried	Size of the coils packed in the sac (diameter × length)	Immediate angiography	Complication	F/U MR angiography
1	51	F	3.9	2.9	4	3 mm × 6 cm, 2 mm × 6 cm	Neck remnant	None	Occluded
2	34	F	3.7	3.5	3	4 mm × 7 cm, 2 mm × 4 cm	Complete	None	Occluded
3	52	M	3.8	3.2	2	3.5 mm × 7.5 cm, 2 mm × 8 cm	Complete	Transient amnesia due to microembolism	Occluded
4	64	F	3.8	2.8	4	3 mm × 4 cm, 1.5 mm × 2 cm	Complete	None	Occluded on DSA
5	54	M	3.7	2.4	3	NA	Aborted and switched to clipping	None	NA
6	44	M	3.8	2.1	5	2.5 mm × 4 cm, 1.5 mm × 4 cm	Complete	None	Occluded

F: female; M: male; F/U: follow-up; AChA: anterior choroidal artery; MR: magnetic resonance; DSA: digital subtraction angiography; NA: not applicable.

Figure 1.

A 44-year-old man treated using the “two-coil technique” for incidentally detected unruptured aneurysm at the origin of the AChA (case 6). (a) Three-dimensional (3D) ICA angiography shows a small but lobulated aneurysm at the origin of the AChA, which arises from the waist of the sac near the neck. (b) A schema illustrating the final coil packing status while the origin of the branch is not compromised. (c) Control angiography shows complete occlusion of the aneurysm sac with good preservation of the AChA, which runs posterior to the shadow of the distal ICA in this image. (d) Time-of-flight MR angiography confirmed good patency of the branching vessel and complete occlusion status of the coiled aneurysm. AChA: anterior choroidal artery; ICA: internal carotid artery; MR: magnetic resonance.

Figure 2.

A 44-year-old man who received the “two-coil technique” for incidentally detected unruptured aneurysm at the origin of the AChA (case 5). (a) Initial 3D angiogram shows a small but lobulated aneurysm. At the posterolateral aspect of the sac there is a tiny bleb while the AChA originated from the medial aspect of the aneurysmal waist near the neck. (b) With the use of two microcatheters, several attempts of coil packing were performed. However, the preservation of the AChA patency was not possible even after multiple repositioning of the coils. The AChA is occluded on this image. The procedure was aborted and elective clipping was performed. (c) Post-clipping 3D angiography shows complete isolation of the aneurysm sac with good preservation of the AChA. AChA: anterior choroidal artery; ICA: internal carotid artery; MR: magnetic resonance; 3D: three-dimensional.

Final post-procedural control angiography showed occlusion of the aneurysm sac in four cases and a minimal neck remnant in one case. MRA was obtained the day after the procedure in all patients except one who had a cardiac pacemaker. MRA did not show any residual filling in the imaged patients. The remaining one patient who was not imaged was asymptomatic post-procedure.

A periprocedural complication occurred in one patient presenting thromboembolic event. The patient complained of transient amnesia after embolization and showed several microembolic dots in the left medial temporal lobe on the diffusion-weighted MR imaging obtained subsequently. His symptom improved without any residual sequelae within a few hours. There was no case of complication associated with obstruction or stenosis of the AChA.

Follow-up results

Of the six aneurysms, all underwent follow-up MRA at six months after coil embolization except the patient with a cardiac pacemaker. We followed this patient with conventional angiography. All six cases showed stable occlusion without recanalization or residual aneurysm.

Discussion

The detachable coil system now is a well-established innovative technology for the management of both ruptured and unruptured cerebral aneurysms because the coil can be repositioned repeatedly until it is appropriately placed within the aneurysm sac.⁸ However, once the coil is detached, the operator can no longer control it. In some cases, there is passive movement of the detached coil loops due to insertion of successive coils. With this motion there always is a possibility of unsatisfactory repositioning of the already detached coil loops that we can do little to reverse or overcome. If the loops herniate into the parent artery, a self-expanding stent can be inserted to resolve the condition.^6,9 However, if the herniated or moved coil loops are compromising the origin of the branching vessel, which is incorporated into the neck or sac of the aneurysm, the non-detached coil must be retrieved. Since there is a possibility of movement of the already detached coil loops, retrieval of the non-detached coil does not always guarantee the patency of the compromised branch vessel. Several ideas have been attempted to overcome limitations of current detachable coil technology. Those ideas focus on adjusting the detachment point at the end of coil insertion using a coil long enough to pack the sac.^10–13

In contrast to hard-to-realize ideas, our two-coil technique was based on a simple idea modified from the double-microcatheter technique.^5,6,14 Our method is based on the coils not being detached until the end of the procedure so that any coil can be removed or repositioned at any given time until one could achieve a satisfactory embolization result. Although our experience was limited to the use of two coils via two microcatheters, it might be feasible to use more than two coils if the parent artery and guiding catheter inner diameter were larger enough for more than two microcatheters.

With our accumulating experience with this technique and the relative ease with which it can be performed, it may be possible to expand its indication. Applying this technique to the treatment of small aneurysms, which could be treated with two to three coils, also may enhance its effectiveness and safety. If the case is not a complicated one, we can detach one of the coils for successive coil insertion as we have done using the conventional multiple microcatheter technique. Currently, we prefer using two microcatheters for non-assisted coiling because the plurality of the microcatheters could add versatility to our procedure.^15,16

We prefer placing the second microcatheter when the first two or three loops of the framing coil are deployed because the presence of the second microcatheter tip in the sac or neck from the beginning may hinder ideal coil frame formation. However, from time to time, we needed to place the second microcatheter and insert the second coil partially to enhance the stability of the framing. We believe that the second microcatheter and coil could be placed and inserted following complete insertion of the framing coil at the individual operator’s discretion.

Coil size could be chosen as we have in our regular coiling procedure (Table 1). We prefer a coil having a sufficient diameter and length as the first coil for this technique. The second coil is used as the finishing coil like a regular coiling procedure. Then it becomes rather easier for us to adjust the second coil length. If there is more space to fill, then switch the second one to a longer one. If the branching vessel patency cannot be guaranteed, then remove the coil and switch to a shorter one while recreating the frame coil. Since the technique does not allow use of any third coil, we cannot deny a higher chance of lower packing density than in a regular situation.

Since our study was performed retrospectively, as a limitation of our study we could overestimate the success rate since there could be cases requiring more coils after insertion of two coils. Because of our case enrollment scheme, those cases were not included. Second, our study included a relatively small number of patients. Therefore, a study with a large number of patients is needed to verify our results. Third, because of the lack of X-ray angiography for long-term imaging follow-up, the long-term efficacy of this technique was not evaluated. However, we believe that TOF MRA is a reliable follow-up tool.¹⁷

Conclusions

The two-coil technique can be used as a technical variation of the multiple microcatheter technique for non-assisted coiling of small aneurysms with the AChA incorporated into the sac or neck of the aneurysms, which otherwise are regarded as non-coilable lesions.

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: a grant (HO13C0006) from Osong Innovation Center funded by the Ministry of Health and Welfare, the Republic of Korea.