Introduction

Due to advances in diagnostic imaging technology, angiographic screening, such as computed tomography or magnetic resonance angiography, is increasing. As a result, more cases of unruptured paraclinoid aneurysms requiring treatment are found, despite being benign.Management of such lesions has placed a burden upon even experienced neurosurgeons. These lesions are considered to be more technically difficult for obtaining proximal vascular control compared to those occurring at the skull base. The close relationship with surrounding nervous structures creates a high risk of rupture and direct injury to cranial nerves. However, as advances in microcatheter technology have made endovascular approaches relatively easy and less dangerous, many centers have begun to report favorable results with endovascular coil embolization of paraclinoid aneurysms during the past decades. In the current study, we report our experience with endovascular embolization of paraclinoid aneurysms using detachable coils.

Materials and Methods

We reviewed 78 patients with 86 paraclinoid aneurysms managed by endovascular embolization using detachable platinum coils at our institute from 2005 to 2011. A retrospective review of the medical record was performed. To evaluate clinical outcomes, the Glasgow Outcome Scale (GOS) score was recorded at discharge and at follow-up. Procedure-related morbidity was defined as a neurological deficit lasting more than seven days that was attributable to the coil embolization procedure.

Description of aneurysms

Paraclinoid aneurysms originate from the internal carotid artery between the distal dural ring and the posterior communicating artery, and are designated as clinoid medial, clinoid anterolateral, ophthalmic artery, superior hypophyseal artery and dorsal wall aneurysms.4)5)12) It was also included that aneurysms arise from the distal cavernous ICA and those project into the extra cavernous intradural subarachnoid space. The fundus size of aneurysms was considered to be small if they were within 10mm or smaller in size, large if 11 to 24mm, and giant if 25mm or greater. Fundus-to-neck ratios were regarded to be favorable if greater than two and unfavorable if two or less.

Endovascular procedures

All patients with unruptured aneurysms were pretreated with dual anti-platelet agents (aspirin 100 mg /day and clopidogrel 75 mg /day) for three to seven days prior to the procedure. In patients with acute subarachnoid hemorrhage, 300 mg of clopidogrel was loaded after the procedure through a nasogastric tube. All procedures were performed under general anesthesia with full heparinization (activated clotting time >250-300 seconds). A 6-F guiding catheter (Envoy; Cordis, Miami Lakes, Florida) was introduced via the femoral artery. A microcatheter (SL-10, Boston Scientific, Fremont, CA; Echelon-10, ev3, Irvine, California) was advanced and then placed into the aneurysm using conventional techniques. In the majority of cases, a single or double microcatheter technique was utilized. However, when immediate results were not satisfactory, or evidence of coil herniation was noted, a hypercompliant balloon or self-expandable stent assisted technique was used. Bare platinum coils were used in all patients.

Outcome evaluation and follow-up protocol

Initial pretreatment angiograms were obtained with 3-dimension rotational digital subtraction angiography (DSA) and the fundus size of the aneurysms, including fundus-to-neck ratio, were measured. Immediate post-embolization angiographic results were defined by occlusion grade: complete occlusion (no contrast-filling in aneurysm sac), near-complete (minimal residual contrast filling in the neck without opacification of sac) and partial (any contrast filling in the body, dome, or both in the aneurysm). The routine follow-up protocol included plain skull x-rays at 3, 6, and 12 months, magnetic resonance angiography (MRA) at 6 months, and conventional angiography at 12 months to assess recanalization of the coiled aneurysm. It has been followed up in the case which had unruptured aneurysms of other lesion every year thereafter. If any morphological change was noted on follow-up plain skull x-ray or MRA, we immediately performed conventional angiography regardless of the routine follow-up protocol.

Statistical Analysis

We analyzed the data using SPSS 17.0 (SPSS Inc.,Chicago, IL, USA) for Windows. To assess the relationship between initial occlusion grade and fundus size or fundus-neck ratio, Chi square test was used. P values less than 0.05 were considered statistically significant.

Results

Patient sample and clinical presentation

Seventy-eight patients with 86 paraclinoid aneurysms were evaluated. Thirteen patients (16.7%) were men and 65 (83.3%) were women. Patient age ranged from 23 to 78 years (mean age, 48 years). The clinical presentations of the patients are given in Table 1. Five patients (6.4%) presented with subarachnoid hemorrhage (SAH) from rup tured paraclinoid aneurysms and six patients (7.7%) were found to have coincidental lesions of other ruptured aneurysms; of these, seven were classified as Hunt and Hess Grade II and four as Grade III. These patients were treated within 24 hours of rupture. Four patients (5.1%) presented with visual field defects associated with aneurysm mass effects. Sixty-three patients (80.8%) had incidental paraclinoid aneurysms found by health maintenance exams or on work-up of non- specific symptoms such as eadache.

Anatomical characteristics

Paraclinoid aneurysms were classified as lesions arising from the clinoid and ophthalmic segments of the ICA: clinoid medial (n=37, 43%), ophthalmic (n=18, 21%), superior hypophyseal (n=17, 19.8%), dorsal wall (n=12, 14%), and clinoid anterolateral (n=2, 2.2%) and those are also outlined in Table 1. Nine (11.5%) patients presented with aneurysm multiplicity. Of these, two cases were in the cavernous segment and the remaining six had other aneurysms in contralateral ophthalmic locations like mirroring. The rest one case had an anterior communicating artery aneurysm in the opposite side. Fundus size was small (≤10 mm) in 55 aneurysms (64%), large (11~24 mm) in 29 (33.7%) and giant (≥ 25 mm) in two (2.3%) (range; 5-32 mm). The fundus-toneck ratio was favorable (>2) in 21 aneurysms (24.4%) and unfavorable (≤2) in 65 aneurysms (75.6%).

Initial and follow-up degrees of occlusion

Of 86 treated aneurysms, the immediate post procedural angiogram demonstrated complete occlusion in 73 aneurysms (84.9%), near-complete occlusion in eight aneurysms (9.3%) and partial occlusion in five aneurysms (5.8%, Table 2). There were no significant differences in the initial occlusion rates according to the fundus size (p=0.096) or the fundus-to-neck ratio (p=0.497) of the aneurysms. we obtained angiographic follow-up in 46 cases. Angiographic follow-up ranged from six to 25 months (mean, 11.9 months). Four of 86 paraclinoid aneurysms required more than one session of endovascular treatment (4.7%). Among four patients, two giants aneurysms had major recanalization. The other two large aneurysms were minor recanalization, but we did not get dense packing. Increased size in these two large aneurysms was found in the six months angiographic follow-up, and re-embolizations were performed despite minor recanalizations.

Procedural complications

Of the 78 patients, there were two (2.6%) procedural complications. One patient had a large fundus aneurysm (12 mm) with a broad neck in the left cavernous sinus. She suffered from visual field defects secondary to aneurysm mass effect. After endovascular embolization, aggravation of the mass effect occurred, leading to blurred vision. The visual acuity did not recover despite steroid therapy. One thromboembolism (1.28%) occurred, and the patient had permanent left hemiparesis after five days since the operation.

Clinical outcomes

According to the Glasgow Outcome Scale, 76 patients treated by endovascular coil embolization had good recovery (97.44%). One patient who had blurred vision had moderate disability and did not return to work. The patient who had right middle cerebral artery territory infarction after embolization had suffered from severe disability (Left hemiparesis, motor grade : GIII/GIII) and it was permanent neurologic deficit. There was no mortality case.

Discussion

Paraclinoid aneurysms account for approximately 11 to 20% of all intracranial aneurysms.10)11) The number of diagnoses is increasing due to advances in neuroimaging modalities and increased health maintenance exams. Paraclinoid aneurysms are much more frequently found in

women, with a female-to-male predominance as high as 9:1.3)9)21) These lesions present with much larger sizes than other aneurysmal lesions.1) There is a high incidence of multiple aneurysms in the contralateral paraclinoid carotid artery in some reports.6)16) Many paraclinoid

aneurysms are found incidentally due to rupture of an associated lesion.8)19) Similar to previously published reports, in the current study, 65 of the 78 patients (83.3%) were women. Nine (11.5%) patients who had multiple aneurysms had these located in the contralateral carotid artery. Sixty-three patients (80.8%) were incidentally found to have paraclinoid aneurysms. There is debate as to the proper therapy for these lesions. Because of the complex topographical anatomic relationships between dural structures and the bony anatomy, the approach of paraclinoid aneurysms remains a great challenge for vascular neurosurgeons with regard to the use of skull base approaches and resection of the anterior clinoid process. Additionally, asymptomatic paraclinoid aneurysms without extension above the distal dural ring are treated conservatively, because of a low risk for life-threatening problems.13) Some Japanese groups argue that endovascular therapies for anterior wall paraclinoid aneurysms, true ophthalmic lesions and carotid cavernous lesions are associated with lower rates of complete obliteration than direct surgery.Conversely, Tadashi N et al. recommended direct clipping as the treatment of choice for patients with a mass effect on the optic nerve if there was not partial thrombosis or calcification of the aneurysmal wall even though optic nerve injury is one of the most common complications after surgical treatment of paraclinoid aneurysms.2)17) The debate regarding appropriate treatment of these lesions is ongoing. The sizes and shapes of lesions seem to be unrelated to therapeutic results. The current study found no differences in initial occlusion rates according to fundus size (p=0.096) or the fundus-to-neck ratios (p=0.497) of the aneurysms. There were two procedural complications (2.6%) among 86 procedures. The morbidity rate (2.6%) in the current study was very low when compared to reports of surgical intervention. De Jesús et al. reported a 16% permanent morbidity using direct surgical treatment for paraclinoid aneurysms.7) Oh et al. announced a 14.8% permanent decreased visual acuity after microsurgical clipping.14) Son et al. gained the better clinical outcome (4.2%, permanent morbidity) after an ipsilateral pterional approach with extradural anterior clinoidectomy.15) Interestingly, the recanalization rate (3.49%) of the current study was low compared to other lesions (25~40%) after endovascular treatment.18)20) The wall shear stress in paraclinoid aneurysms may be less than in other lesions. The hemodynamics of paraclinoid aneurysms are characterized by relatively strong wall shear stress. This benefit should be considered when deciding on treatment modalities.
The limitations of the current study include a lack of comparison groups and randomized multicenter case control series. Further research to elucidate clear indications for endovascular approaches for these lesions is required.

Conclusion

Endovascular treatment for paraclinoid aneurysms is relatively easy and safe method compared to the microsurgical approach and it has less complications. Also, the recanalization rate of our results in paraclinoid aneurysms showed low rates than other lesions. Our results suggest that endovascular treatment of paraclinoid aneurysms is a safe and effective therapeutic alternative to direct surgery.

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