Stent-assisted coil embolization of a recurrent posterior cerebral artery aneurysm following surgical clipping

Abstract

Posterior cerebral artery (PCA) aneurysms are rare, and direct surgery of these is considered difficult. Coil embolization of PCA aneurysms is becoming popular. However, it is difficult to completely obliterate the aneurysm while preserving the flow of the parent artery in large or giant PCA aneurysms with a wide neck with this technique. We report a case of a large and wide-necked PCA aneurysm with multiple recurrences following successful surgical clipping and coil embolization.

A 77-year-old man with a large unruptured right PCA (P2) aneurysm was successfully treated by surgical clipping. Postoperative digital subtraction angiography (DSA) showed complete aneurismal occlusion. Four years afterward, the aneurysm recurred and grew toward the contralateral. Surgical retreatment of this complicated aneurysm was considered difficult, with a substantial risk of complications. Therefore, the aneurysm was treated with an endovascular procedure. Because simple coil embolization was not expected to achieve satisfactory obliteration of the aneurysm with preservation of parent artery patency, we used stent-assisted coil embolization. The patient tolerated the treatment well. On DSA obtained six months after the first endovascular treatment, coil compaction and recanalization of the aneurysm were detected. A second coil embolization was successfully performed without any complications. The aneurysm was stable during the next six-month follow-up. Stent-assisted coil embolization may be feasible and effective for such postoperatively complicated aneurysms.

Introduction

Posterior cerebral artery (PCA) aneurysms are rare and represent approximately 0.7%–3% of all intracranial aneurysms.^1–5 Surgical clipping of PCA aneurysms is technically challenging because they are located deep in the brain and surrounded by the cranial nerves and upper brainstem.¹ Endovascular treatment has progressed and become more refined in recent years, and it is thus becoming the first-line treatment for PCA aneurysms.^1–7 In addition, endovascular treatment is also considered a first-line treatment for aneurysms showing postoperative recurrence, because a second surgical clipping may be technically difficult because of surgical-site adhesions or mechanical obstruction because of the previous clip.⁸ However, if the recurrent aneurysms are large or giant-sized with a wide neck and complicated morphology, it is also difficult for endovascular treatment to obliterate the aneurysm while preserving parent artery patency. We present a case a large recurrent PCA aneurysm treated with stent-assisted coil embolization.

Case presentation

History and examination

A 77-year-old man was referred to our neurosurgical department for treatment of a large aneurysm of the PCA that was discovered incidentally. He had no neurological deficits. Digital subtraction angiography (DSA) demonstrated a 14 × 15-mm wide-necked aneurysm at the P2 segment of the right PCA (Figure 1(a)–(c)). As the aneurysm had a wide neck, it was thought that endovascular embolization would not be able to achieve complete obliteration of the aneurysm with preservation of parent artery patency. Therefore, we planned surgical clipping of this aneurysm.

Figure 1.

Preoperative digital subtraction angiography (DSA) showing a large saccular aneurysm arising from the P2 segment of the right posterior cerebral artery ((a) anteroposterior view, (b) lateral view, (c) three-dimensional DSA). Postoperative computed tomography showing no ischemic or hemorrhagic lesions (d). Postoperative DSA showing complete obliteration of the aneurysm with slight dilatation of the parent vessel (arrow in (e), (f)).

Initial surgical clipping of the aneurysm

Through a right trans-sylvian transchoroidal fissure approach, the parent vessel was reconstructed using two clips, with complete obliteration of the aneurysm in the ambient cistern. Postoperative computed tomography demonstrated no ischemic or hemorrhagic lesions (Figure 1(d)). A postoperative DSA showed complete occlusion of the aneurysm, except for a slight dilatation of the reconstructed segment of the parent artery (Figure 1(e), (f)). The patient was discharged without neurological deficits.

Regrowth of the aneurysm, first stent-assisted coil embolization and second coil embolization

After four years of uneventful postoperative course, follow-up DSA demonstrated aneurysmal regrowth at the previously reconstructed parent vessel (Figure 2(a), (b)). A second clipping was deemed technically difficult and accompanied by considerable risks. Taking into consideration the complicated morphology of the aneurysm and its wide neck, neither simple endovascular coil embolization nor a balloon-assisted technique were likely to achieve successful obliteration of the aneurysm while preserving parent artery patency. Stent-assisted coil embolization was considered suitable for this type of recurrent aneurysm with complicated morphology. The patient was premedicated with daily doses of 100 mg of aspirin and 75 mg of clopidogrel starting from seven days before the procedure. Under local anesthesia, a 5F shuttle guiding sheath (Cook Medical, Bloomington, IN, USA) was placed in the left vertebral artery. Although it was difficult to navigate a microcatheter into the distal PCA because of the tortuosity of the parent artery and the wide neck, we were able to maneuver an Excelsior XT-27 microcatheter (Stryker, Fremont, CA, USA) into the right distal PCA across the aneurysmal orifice using a 0.016-inch GT wire (Terumo, Tokyo, Japan). A 2.5 × 20 mm Neuroform stent (Stryker, Fremont, CA, USA) was positioned around the aneurysmal orifice through the XT-27 microcatheter. At stent deployment, the stent moved proximally, with microcatheter kickback as a result of parent artery tortuosity. Consequently, the distal end of the Neuroform stent was positioned immediately distal to the aneurysmal orifice. An Excelsior SL-10 microcatheter (Stryker, Fremont, CA, USA) was navigated into the aneurysm with a 0.012-inch GT wire (Terumo, Tokyo, Japan) using the trans-cell technique. The aneurysm was occluded with coils (Target helical coils: 7 mm × 20 cm, 6 mm × 20 cm; × 2, 5 mm × 15 cm, 4 mm × 15 cm; Stryker, Kalamazoo, MI, USA; the total length of the deposited coils was 90 cm), with preservation of PCA patency (Figure 2(c), (d)). The postoperative course was uneventful, and the patient was discharged one week postoperatively. A follow-up DSA obtained six months after the first endovascular treatment demonstrated aneurysmal recanalization, with compaction of the coils (Figure 2(e)). Therefore, a second coil embolization was scheduled. Under local anesthesia, a 5F shuttle guiding sheath was placed in the left vertebral artery. An Excelsior SL-10 microcatheter was navigated into the right PCA aneurysm with a 0.014-inch Synchro microguidewire (Stryker, Fremont, CA, USA) using the trans-cell technique through the previously deployed stent strut. We performed additional coil deliveries (Target 360 coils: 12 mm × 45 cm; × 2; Target helical coils: 8 mm × 30 cm; × 4, 6 mm × 20 cm; × 2, 4 mm × 15 cm; the total length of the deposited coils was 265 cm). Satisfactory occlusion of the recanalized aneurysm was achieved, with preservation of parent artery patency (Figure 2(f)). The postoperative course was uneventful, and there was no recurrence of the aneurysm six months after the second coil embolization.

Figure 2.

A follow-up digital subtraction angiography (DSA) obtained four years after the surgical clipping showing regrowth of the aneurysm extending toward the opposite side of the previous dome ((a) anteroposterior view, (b) three-dimensional (3D) DSA). Stent-assisted coil embolization with a Neuroform stent and Target coils achieved satisfactory obliteration of the aneurysm, with relatively loose packing on the orifice side ((c) anteroposterior view, (d) 3D DSA). The arrows indicate the markers of the Neuroform stent. A DSA obtained six months after the first stent-assisted coil embolization showed coil compaction and aneurysmal recanalization (e). A second embolization with Target coils achieved complete obliteration of the aneurysm (f).

Discussion

Aneurysms of the PCA are rare and challenging to treat.^{1, 6} PCA aneurysms tend to have the following characteristics: a higher incidence of large and giant aneurysms, occurring in younger patients, comorbidity with another vascular abnormality, and most are located at the P2 segment.⁶ The most common clinical presentation of PCA aneurysms is subarachnoid hemorrhage. In cases of large or giant aneurysms of the PCA, symptoms of mass effect on the surrounding brain parenchyma and cranial nerves occur.¹ Surgical clipping of PCA aneurysms may be technically difficult because of their deep location in the brain and the complex anatomy; therefore, surgical procedures may involve potential risk for morbidity and mortality. On the other hand, endovascular coil embolization could be safer and less invasive than surgical clipping; it is, therefore becoming the first line of treatment for PCA aneurysms.

Postoperative aneurysm remnants are found in 4%–8% patients who undergo angiography after surgical clipping.⁹ Reoperation of the recurrent aneurysms following surgical clipping is often technically difficult, and it is associated with an increased risk of complications because of surgical-site adhesions or the interference of previous clips.⁸ Endovascular coil embolization is safer and more effective in such cases, as endovascular treatment is unlikely to be affected by previous surgery.^8,9

In general, endovascular coil embolization is considered an inferior option to surgical clipping for treating large or giant aneurysms with a wide neck.¹ Surgical clipping of large or giant aneurysms with a wide neck may also be associated with the risk of certain complications such as cerebral infarction in the parent artery territory. In addition, surgical clipping of large or giant aneurysms with multiple clipping methods may be associated with a risk of aneurysm regrowth because of the abnormalities of the reconstructed vascular wall. In recent years, intracranial stents for wide-necked aneurysms have extended the indications of endovascular treatment.¹⁰ Stent-assisted coil embolization may be suitable for treating wide-necked aneurysms, because stents allow denser aneurysm packing with increased neck coverage, and may also improve treatment durability through a combination of flow diversion with parent vessel straightening, and fibroelastic tissue formation along the aneurysm neck.¹¹ The present case report shows the feasibility of endovascular treatment for complex recurrent aneurysms after surgical clipping of a large PCA aneurysm. The initial surgical clipping of the large PCA aneurysm, which used a multiple clipping technique, has initially achieved successful obliteration of the aneurysm with preservation of parent artery patency. Four years after clipping, however, the aneurysm recurred with growth toward the opposite side of the previous dome. The lesion was not deemed amenable to treatment with re-clipping or simple coil embolization. Parent artery occlusion was considered associated with a considerable risk of cerebral infarction in the PCA territory.^1,2 Therefore, we decided to treat the aneurysm using stent-assisted coil embolization, so as to preserve parent artery patency.

In the present case, navigation of the microcatheter into the distal PCA was difficult because of the narrow and tortuous parent artery and the broad base of the aneurysmal orifice. In addition, stent malpositioning might occur easily in the case of a narrow and tortuous parent artery. Stent length and the positioning of its distal end should be carefully decided, because microcatheter kickback may occur with the deployment of a Neuroform stent. With regard to the navigation of the microcatheter into the aneurysmal lumen, the trans-cell approach was used in this case because the narrow lumen of the parent artery prevented the use of the jailing technique, which requires the navigation of two catheters simultaneously. In the first coil embolization, dense packing of the aneurysmal orifice was intentionally avoided so as to preserve parent artery patency. Because coil compaction and recanalization of the aneurysm occurred following the first coil embolization, a second coil embolization was necessary. During the second coil embolization, the previously deployed stent allowed an effective scaffold to be formed, enlargement of the diameter, and the straightening of the parent vessel, thus achieving denser packing of the aneurysm. The results of the present case suggest that staged coil embolizations following stent placement could be a treatment option for such complicated aneurysms.

Conclusions

We describe a case of a wide-necked, recurrent large aneurysm of PCA following successful surgical clipping. Stent-assisted coil embolization could be effective for such complicated recurrent PCA aneurysms. To obliterate such an aneurysm, it is important to precisely understand the anatomical features of the aneurysm and make careful decisions regarding treatment strategy.

Conflict of interest

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

Funding

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