Coiling for an unruptured saccular aneurysm at the non-branching segment of the distal anterior cerebral artery: Case report and literature review

Abstract

Background

Saccular aneurysms in the non-branching segment of the distal anterior cerebral artery (DACA) are extremely rare. Here, we describe the first case of coil embolization using a simple, non-adjunctive technique for an aneurysm at this rare location.

Case description

A 74-year-old man with an asymptomatic, unruptured aneurysm of the right DACA was followed up annually for 3 years by medical checkup. Endovascular treatment was proposed because of a slight angiographic change in the shape of the aneurysm in the past year. The aneurysm at the non-branching site of the right calloso-marginal artery was 2 mm distal to the origin, and measured 3 mm in height and 3.3 mm in width, with a neck measuring 1.7 mm wide; the calloso-marginal artery diameter was 1.6 mm. The aneurysm was successfully embolized with a simple technique using a Pre-Shaped S Microcatheter and two coils.

Conclusions

The simple, non-adjunctive technique for coil embolization of saccular side-wall type aneurysm in the non-branching segment of the DACA could be performed using the appropriate catheter and a softer coil.

Background

Distal anterior cerebral artery (DACA) aneurysms represent approximately 1.5–9% of all intracranial aneurysms.^1–4 They are prevalent at the bifurcation of the pericallosal and calloso-marginal arteries.³ DACA saccular aneurysms at the non-branching sites are extremely rare.^5–10 Of the five reported surgical cases of DACA saccular aneurysm at the non-branching site, only one involved endovascular treatment using a flow diverter (Table 1).¹⁰ To the best of our knowledge, this is the first report on intra-aneurysmal coil embolization using a single catheter, non-adjunctive technique for an unruptured saccular aneurysm associated with the non-branching site of the DACA.

Table 1.

Details of case reports of distal anterior cerebral artery (DACA) non-branching saccular aneurysms.

Author (year)	Age, years/sex	Status	Location	ICH	Size, mm	Treatment	Outcome
Yabuta et al. (1991)5	43/M	Rupture (+)	A2	Septum pellucidum, bilateral frontal	NI	Clipping	Good recovery
Yoshimoto et al. (1996)6	35–60 (mean 49) M=2, F=1	Rupture (+) = 2, No rupture=1	Pericallosal=1, others NI	NI	NI	Clipping	Good recovery
Yamashita et al. (1997)7	47/M	Rupture (+)	Calloso-marginal	Left frontal lobe	1.5	Clipping	Moderate disability
Yamanaka et al. (1999)8	72/F	Rupture (+)	A2	Left frontal lobe	12	Clipping	Severe disability
Takeuchi et al. (2013)9	87/F	Rupture (+)	A3	Corpus callosum	NI	Clipping	Moderate disability
Nossek et al. (2017)10	57/F	No rupture	A2/3		6.2 (neck 4.2)	Endovascular flow diverter	Good recovery
Present case	74/M	No rupture	Calloso-marginal		3.3 × 3 (neck 1.7)	Endovascular coiling	Good recovery

ICH: intracerebral hemorrhage; NI: no information.

Case presentation

A healthy 74-year-old man was followed up annually over 3 years for an asymptomatic, unruptured aneurysm of the right DACA, appearing to be of the fusiform type (Figure 1(a)). The aneurysm was diagnosed during a medical checkup. The patient had no significant history of infections or head trauma. Due to a slight angiographic change in the aneurysmal shape in the past year (Figure 1(b)), endovascular treatment was proposed. Angiography revealed that the aneurysm, at the non-branching site of the right calloso-marginal artery, was 2 mm distal to the origin and measured 3 mm in height, 3.3 mm in width, the neck was 1.7 mm wide, and the calloso-marginal artery diameter was 1.6 mm (Figure 2). The patient was prescribed aspirin (100 mg/day) and clopidogrel (75 mg/day) for 1 week prior to endovascular treatment.

Figure 1.

Follow-up of the aneurysm in the non-branching segment of the distal anterior cerebral artery. (a) Initial magnetic resonance (MR) angiography (lateral view) showing an aneurysm (arrow) arising on the calloso-marginal artery. Initially, this aneurysm was assumed to be of fusiform type (arrow); (b) MR angiography after 1 year, with a slight change of the aneurysm to the saccular type, was suspected (double arrow).

Figure 2.

Angiographic description of the aneurysm. Angiogram demonstrates a saccular aneurysm. It was 3 mm in height, 3.3 mm in width, and the neck was 1.7 mm wide. The aneurysm originated at the non-branching site of the right calloso-marginal artery (arrow), and 2 mm distal to the origin of the anterior cerebral artery. The vessel diameter of the calloso-marginal artery was 1.6 mm.

The procedure was performed under general anesthesia, and with systemic heparinization via the transfemoral approach using a biplane flat-panel angiographic unit. A guiding catheter (Launcher 7 Fr × 90 cm Straight; Medtronic, Minneapolis, MN) was introduced into the proximal cervical segment of the right internal carotid artery through an intermediate catheter (4 F Inner Guiding Catheter “Cerulean”; MEDIKIT Co., Ltd. Tokyo, Japan). The intermediate catheter was placed at the petrous segment of the internal carotid artery.

At first, a microcatheter (Echelon pre-shaped 45 angle microcatheter; Covidien, Irvine, CA) was inserted into the neck of the aneurysm by a pull-back technique. However, this was abandoned since the insertion depth of the microcatheter tip was shallow and unstable. Next, we adopted and inserted another microcatheter (Excelsior SL-10 Pre-Shaped S; Stryker Neurovascular, Cork, Ireland) into the aneurysm with a micro guidewire (Traxcess Guidewire Microvention; Terumo, Tustin, CA). The first coil (Target Ultra 360 Detachable Coils, 3 mm × 6 cm; Stryker Neurovascular, Fremont, CA) was inserted for framing. Regardless of the occasional microcatheter kickback, coil embolization was continued while coils were taken in and out, leading to delicate pulling and pushing of the microcatheter while moving the coil in and out (Figure 3(a)). The second coil (Target Nano™ 360 Detachable Coils, 1.5 mm × 2 cm; Stryker Neurovascular, Fremont, CA) was inserted into the first coil. At this stage, the microcatheter kicked-back, and a slight neck remnant was observed. However, we completed the procedure (Figure 3(b)), and an almost complete occlusion was later confirmed (Figure 3(c)). The postoperative volume embolization ratio (VER) was 34.1%. No coil deviation was observed on skull radiography immediately after endovascular therapy, and no neurological abnormalities were evident. Magnetic resonance imaging (MRI) at 7 months after the coil embolization showed obliteration of the aneurysm and preservation of the calloso-marginal artery (Figure 4).

Figure 3.

Embolization of the aneurysm using the simple, non-adjunctive technique. (a) Angiogram and its schema demonstrated the advancement of a single microcatheter (MC), (Excelsior SL-10 Pre-Shaped S; Stryker Neurovascular, Cork, Ireland) to the aneurysm via the intermediate catheter (arrow). Two coils were inserted via the MC. Pre-shaped S MC was suitable for this case because its proximal curvature fit the artery from the parent artery to the neck of the aneurysm. Two supporting points (triangle) of the MC provided stability. MC kickback was occasionally observed; however, coil embolization was continued while coils were taken in and out, pulling and pushing the MC delicately while moving the coil in and out. (b) Right internal carotid artery angiogram just after coil embolization demonstrates residual aneurysm neck. Note the patency of the trunk of the calloso-marginal artery. (c) Final right internal carotid artery angiogram, 15 min after treatment showing nearly complete occlusion of the aneurysm.

Figure 4.

Post coil embolization at month 5. MR angiography shows obstruction of the aneurysm (arrow).

Discussion

The frequency of the non-branching site DACA aneurysm is unknown. Steven et al.⁴ reported that out of the 67 DACA aneurysms diagnosed in 1109 patients, four aneurysms were at the non-branching point; of the four, two were due to trauma and others lacked a shape description, such as saccular or fusiform, and details of dissection. Yoshimoto et al.⁶ described three non-branching saccular DACA aneurysms among 557 saccular intracerebral aneurysms. The incidence, diagnosis, and treatment of non-branching DACA saccular aneurysm are exceedingly rare based on the above reports.^5–10 Endovascular treatment using a flow diverter for a non-branching DACA aneurysm was only reported by Nossek et al.¹⁰ This is the first report of intra-aneurysmal coil embolization for an unruptured saccular aneurysm of the non-branching site of the DACA (Table 1).

Aneurysms in the distal posterior inferior cerebellar artery (PICA) are occasionally unrelated to branching.^11,12 In general, the aneurysm arises from arterial bifurcation because of hemodynamic stress and resulting vessel wall degenerative changes.^6,13 Horiuchi et al.¹¹ reported that hemodynamic stress and congenital factors may be involved in branchless aneurysm formation at the distal PICA. Mizutani et al.¹³ classified intracranial non-atherosclerotic aneurysms unrelated to branching zones into four types based on their pathological features. Of these, saccular aneurysms associated with non-branching sites are classified as Type 4. Internal elastic lamina (IEL) degeneration causes saccular bifurcation aneurysm, whereas the Type 4 aneurysm arises in areas with minimally disrupted IEL without intimal thickening, In addition, Type 4 aneurysms have a dome formed from fragile connective tissue or adventitia, and lack IEL. Hence, a Type 4 aneurysm tends to rupture before growth. Takeuchi et al.⁹ surgically demonstrated that the pathological findings of the resected ruptured aneurysm arising in the non-branching segment of the DACA (A3) correspond to those of Type 4. Another reported case of a distal middle cerebral artery ruptured saccular aneurysm was classified as Type 4¹⁴ as the aneurysmal wall lacked IEL and was composed primarily of actin-positive and calponin/desmin-negative alpha-smooth muscle spindle cells. There was also strong, positive immunoreactivity for matrix metalloproteinases (MMPs) 1, 2, and 9 in the spindle cells of the aneurysmal wall. It was speculated that matrix MMPs contribute to the development of saccular aneurysm in the arterial trunk, unrelated to branching zones.

In our case, we initially believed that the aneurysm was fusiform shaped. In the past year, a slight change toward a saccular shape was suspected. Yabuta et al.⁵ reported a subarachnoid hemorrhage due to a ruptured fusiform aneurysm of the non-branching DACA (A2) on initial angiography that had changed to the saccular type on day 19. They performed clipping of the aneurysm on the day after treatment, and hematoxylin-eosin staining of the resected aneurysm showed a ruptured saccular aneurysm. These morphological changes suggest a fragile dome wall. We based our diagnosis and treatment on the above reports because our case was suspected of belonging to the Type 4 Mizutani et al. classification.

To the best of our knowledge, this is the first report of the use of a simple coiling, non-adjunctive technique for a non-branching site aneurysm of the DACA. The calloso-marginal artery was small (diameter 1.6 mm) and its angle was acute, ruling out the suitability of the balloon remodeling technique. In recent years, stent-assisted coil embolization (SACE) has been increasingly used. However, SACE can be technically challenging in case of small vessels (≤2 mm diameter).¹⁵ SACE requires two microcatheters when employing the jailing technique or trans-cell techniques in small vessels. Even with the trans-cell technique, we expected difficulty with placement of the microcatheter through the stent cell. There are some reports of the off-label use of a flow diverter in distal cerebral circulation.^10,16–18 Puri et al.¹⁸ and Bender et al.¹⁷ reported the efficiency and safety of using the flow diverter (Pipeline) for small vessels with diameters less than 2.5 mm and 2 mm, respectively.

Nossek et al.¹⁰ reported the first case of flow diverter use in a non-branching DACA aneurysm with less than 2 mm diameter of the parent artery. However, the use of flow diverters is currently strictly limited in Japan. In May 2018, a low-profile flow diverter stent, Conformité Européene (CE), was approved to be used with a 0.017-inch microcatheter,^19,20 thus expanding the potential of the treatment for small peripheral vessel aneurysms. During our treatment, we used an intermediate catheter distally, for microcatheter stabilization, which allowed a Pre-Shaped S Microcatheter to fit the curvature of the parent artery to the neck of the aneurysm (Figure 3). Microcatheter kickback occasionally occurred during coil insertion and made microcatheter control difficult. Therefore, we inserted a small soft coil to prevent kickback of the microcatheter. When embolizing such distal and side-wall type aneurysms using the present technique, it may be important to use a soft coil to fit a microcatheter gently. In other words, treatment will depend on the behavior of the microcatheter and the coil. Finally, we completed treatment with incomplete occlusion (Figure 3(b)). The embolization of incomplete occlusion for such side-wall type aneurysms is acceptable (Figure 3(c), Figure 4).

Conclusion

We successfully performed coil embolization for a saccular side-wall type aneurysm in the non-branching segment of the DACA using a single catheter and a softer coil.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

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

ORCID iD

Kazushi Maeda https://orcid.org/0000-0002-1792-7131