Introduction

 Since introduction of Guglielmi detachable coils (GDCs) to treat intracranial aneurysms, the number of patients undergoing endovascular treatment has rapidly increased and coil embolization is an effective treatment of option for selected intracranial aneurysms. Despite the advances of endovascular coil embolization, there are still embolization failure, residual sac and regrowth of the aneurysm. Therefore, incompletely or near completely obliterated coiled aneurysms should be regularly monitored and managed aggressively to save the patients against rerupture and associated complications. The present study was performed to review our surgical experiences of recurrent coiled aneurysms and demonstrate microsurgical technique and methods of safe coil removal.

Patients and Methods

Between May 2007 and May 2010, we treated 62 patients with acute ruptured intracranial aneurysms by GDC embolization at our hospital. Among them, six patients (9.6%) showed recurrence during follow-up treatment (mean 9.5 months), who revealed near complete obliteration initially (>90% occlusion) and underwent microsurgical clipping (Table 1). Computerized tomographic angiogram (CTA) was performed soon after microsurgical clipping for the evaluation. We retrospectively reviewed the medical records, radiographic images, operative reports and videos, and clinical follow-up data to determine the clinical outcomes and the factors to select the treatment modality. The patients who require surgical intervention as a result of complications arising from endovascular procedure were excluded.

Clinical outcomes were assessed using the Glasgow Outcome Scale (GOS) score at the time of the latest follow-up evaluations and radiologic outcome was by digital subtraction angiography (DSA) or CTA annually postoperatively. Good outcomes were defined as a final GOS of 5 or 4 and poor outcomes as a final GOS score of less than 4. The width and height of the aneurysm neck were measured before the endovascular procedure. Regrowing width and height of the aneurysm neck were measured before the microsurgical clipping. We routinely record every operation and reviewed intraoperative videos, paying particular attention to microsurgical technique for the coil removal.

Results

There were four female and two male patients with mean age 46.6 years (range 27 to 63). The location of the aneurysms were the internal carotid artery (ICA)–posterior communicating artery junction in three, the dorsal ICA in one, and the vertebral artery-posteroinferior cerebellar artery (PICA) bifurcation in two. The mean aneurysm diameter was 11.1 mm (range 3~21.3 mm) including three large aneurysms (diameter 13.2~21.3 mm) and three small aneurysms (diameter 3~8.7 mm). All six patients were initially deemed complete and near complete (90~99%) occlusion by coiling. Four of these patients had angiographic recurrence of their aneurysms on routine surveillance angiography. One patient presented with recurrent severe eyeball pain that was disappeared after coiling and recurred with pulsatile mass effect to the adjacent dura of reopened large coiled aneurysm (Fig. 1), had early microsurgical clipping two months after coiling. One patient had repeated subarachnoid hemorrhage 21 months after coiling (Fig. 2). Five patients had clipped later than six months. Causes of surgical intervention were rebleeding (n=1), severe eyeball pain (n=1), and coil compaction and regrowing aneurysmal sac (n=4) (Table. 2). All six patients were not possible to recoiling treatment, because one case was higher ratio of remnant neck width/height and another five cases have high risk of adjacent parent vessel occlusion such as posterior communicating artery or PICA.

Microsurgical Treatment and Coil Removal

A pterional approach was used to treat four anterior circulation aneurysms and retrosigmoid approach was applied to the PICA aneurysms. One patient with recurrent orbital pain performed microsurgical clipping two months after coiling. Other five aneurysms were operated more than six months after coiling (range 7 to 26 months). Clipping without removal of coil was performed in two patients, partial removal in two, and complete removal in two. Coil extrusion was found in one ruptured and one coil compaction case. Partial removal of the coils was attempted to save the attached cranial nerve, small perforators and preserve parent arteries. In one patient, the clip was applied completely across the neck with strands of coil between the clip blades. Removal of the coils during surgery was performed more easily in the early surgery(< 2 mos) patients and ICA aneurysm patients. In cases of PICA aneurysm, it is not easy to remove coil in the small aneurysmal sac and in between the lower cranial nerves, then coil removal was not attempted (Fig. 3). Treatment of the proximal ICA aneurysm requires intradural anterior clinoidectomy and exposure of the dural ring to allow proximal control of the aneurysm. There was one intraoperative rupture among six cases which occurred despite temporary clipping, however, clinical outcome was good after permanent clipping and removal of the coil. All patients had good outcomes without any morbidity. Postoperative CTA revealed good architecture of the vessels with less coil artifact in all cases. It is not necessarily to perform an four vessel transfemoral angiography to precise view of the clip and aneurysm.

Discussion

The endovascular treatment of the intracranial aneurysm is relatively simple and elegant against microsurgical treatment, then the incidence of endovascular therapy is very sharply increased. However, endovascular coiling may be a less durable because of residual sac, compaction and recanalization and regrowth.5) In the Cerebral Aneurysm Rerupture After Treatment (CARAT) study of 1010 patients showed that annual retreatment rates among coiled patients were 13.3%, 4.5%, and 1.1% during the first, second and later years, respectively. In contrast, the retreatment rate among clipped patients was 2.6% during the first year and none in later years.6) Rerupture rates among all patients with aneurysms during a mean follow-up period of four years were 1.1% in patients with complete obliteration, 2.9% for patients with 91 to 99% obliteration, 5.9% for patients with 70 to 90% occlusion, and 17.6% for patients with less than 70% occlusion.2) The risk of recurrent subarachnoid hemorrhage during long term follow-up was higher with coiling than clipping.2)10) Large complex aneurysm, younger age and incomplete occlusion have been reported more risk for coil compaction and recanalization.2) Microsurgical clipping of previously coiled aneurysms requires several points to result good outcomes. Enough coil free space at the neck of the aneurysm is most important to successful clipping. Veznedaroglu et al.13) suggested that clippable aneurysm have compaction heights beneath the coils greater than twice the neck width. However, all of our recurrent aneurysms had height of regrowing lumen less than twice the neck width. So it is not so critical. Sometimes there is no sufficient space to clip. In those cases, temporary clipping or trapping of the parent artery and partial removal of the coil at the dome will be helpful to space the neck of the aneurysm. Configuration of the regrowing sac to the parent artery and the site of initiation of the perforating arteries are also considered to perform the clipping. Surgical timing is also another point of issue. Some authors recommend waiting until coil compaction has progressed sufficiently to have the neck free space of coils.4) This may be one of several good strategies, but there are some risks of rupture during the waiting period. In early surgery within two months of coiling as in one of our cases, the coils can be removed easily without any damage to the wall of the aneurysm because there is no adhesion or scar between the aneurysm wall and the coils. For safe removal of the coils, coils should be removed after temporary or permanent clipping of the aneurysm.12) Coils should be cut with stronger microscissors and maden several pieces to easy removal because some long stretched coils have tension to the aneurysm neck. There are more difficulties in surgical treatment of the aneurysms that have been coiled months or years earlier. Coil compaction seems to have degenerative changes on the aneurysm wall resulting it transparent and thin. Intra-aneurysmal thrombosis between the coils and adhesion between the coils and the aneurysm wall make the aneurysm less mobile. Coils should not be extracted because of the risk of tearing the aneurysm neck or injuring the adjacent perforators.3) Removal of the coils perform at the dome of the aneurysm and it is not necessary to remove all the coils. Coils should be cut several pieces inside the aneurysm and removed in small piece of coils without tracking the coils. Extruding coils adhere to the perforators and cranial nerves and make those structures more vulnerable to dissection during surgery.

In complex or giant coiled aneurysm, especially posterior circulation aneurysm, bypass and aneurysm occlusion reported more favorable results than clip reconstruction with coil removal and thrombectomy.12) Because it has significant risks, such as incomplete proximal and distal control, back-bleeding during the repair, adherent branch arteries or perforators to the require dissection difficulty reconstructing the neck after transecting the aneurysm, and dense scarring of the coils to the neck.14) There are some discrepancy whether recoiling or clipping on the recurrent coiled aneurysms. With the ontinuous improvement of the endovascular armamentarium and skills, a higher success rate of aneurysm obliteration has been reported. Some neurointerventional clinicians favor recoiling first and clipping those aneurysms that cannot be coiled,1)7)8)11) but some neurosurgeons favor clipping first and coiling those aneurysms that are unfavorable for open microsurgery.9) However, the goal should be an tailored treatment to every individuals based on the patient, neurointerventional clinician and neurosurgeon with the idea being to prevent recurrent subarachnoid hemorrhage and protect the patient longterm.

Conclusion

Surgeon should keep in mind that coiled aneurysms are more rigid and easily ruptured at the thinned aneurysm neck than the dome. Proximal control of the parent vessels and temporary clipping during dissection of the perforators are always necessarily. Coils should not be removed if they are inside the parent artery or adherent to the adjacent perforators or cranial nerves or extruded in the eloquent brain, such as hypothalamus and brainstem. Complete or partial removal of the coils would be very helpful at the followed radiological work-up.

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