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ORIGINAL ARTICLE
Year : 2012  |  Volume : 60  |  Issue : 6  |  Page : 597--603

Endovascular management of giant intracranial aneurysms of the posterior circulation

Uday S Limaye, Akshay Baheti, Rashmi Saraf, Manish Shrivastava, W Siddhartha 
 Department of Interventional Neuroradiology, Seth GS Medical College and KEM Hospital, Parel, Mumbai, India

Correspondence Address:
Uday S Limaye
Department of Radiology, Division of Interventional Neuroradiology, KEM Hospital, Parel, Mumbai
India

Abstract

Background: Large size, and location in posterior circulation, both individually portend high risk in the endovascular management of intracranial aneurysms. Aim: The purpose of this study was to investigate the outcome of endovascular management of giant posterior circulation aneurysms at our centre. Materials and Methods: This is a retrospective analysis of 22 consecutive patients with giant posterior circulation aneurysms, who were managed by endovascular techniques between 1997 and 2009. The aneurysms included: Vertebral-6 (27%), basilar or vertebrobasilar - 7 (32%) and nine posterior cerebral artery (PCA) - 9 (41%). Results: There were 14 males and eight females with a mean age of 37 years. Treatment modalities included: Parent vessel sacrifice (PVS), coil embolization, flow reversal, stent-assisted coiling, and telescopic stent placement. Angiographic cure or stasis was achieved in 21 (95%) patients and no recurrence was observed in 17 of the 18 patients who had follow-up. Complications occurred in 9 (41%) patients, death in 4 and morbidity in 5 (3 with good eventual outcome). Overall, good clinical outcome was noted in 16 (73%) patients. The majority of the poor outcomes were observed in the management of basilar/vertebrobasilar aneurysms and flow reversal. Parent vessel sacrifice showed the best outcomes with stable results. Conclusions: Our results suggest that PVS remains the procedure of choice wherever possible and is relatively safe, particularly for giant vertebral and PCA aneurysms. When PVS is not feasible, stent-assisted coiling is a reasonable and safe option and requires follow-up. Management of basilar or vertebrobasilar aneurysms is complicated and still evolving.



How to cite this article:
Limaye US, Baheti A, Saraf R, Shrivastava M, Siddhartha W. Endovascular management of giant intracranial aneurysms of the posterior circulation.Neurol India 2012;60:597-603


How to cite this URL:
Limaye US, Baheti A, Saraf R, Shrivastava M, Siddhartha W. Endovascular management of giant intracranial aneurysms of the posterior circulation. Neurol India [serial online] 2012 [cited 2022 May 20 ];60:597-603
Available from: https://www.neurologyindia.com/text.asp?2012/60/6/597/105193


Full Text

 Introduction



Intracranial aneurysms measuring >25 mm in their greatest dimension are considered giant aneurysms. [1],[2] They account for ~5% of all intracranial aneurysms and are less common in the posterior circulation. [1],[2] Management of posterior circulation giant aneurysms is challenging due to their complex anatomic and pathophysiological features. Surgical treatment is associated with high mortality and morbidity. [3] Endovascular treatment is considered to be relatively safer. [4],[5],[6] The purpose of this study was to analyze the clinical presentation, management and outcome of the endovascular treatment of giant posterior circulation aneurysms seen at our center over the last 12 years.

 Materials and Methods



This is a retrospective study of 22 patients who underwent endovascular treatment for giant posterior circulation aneurysms at our center between 1997 and 2009. The clinical profile, imaging and angiographic findings of these patients were reviewed. The endovascular treatment performed was analyzed in terms of location of the aneurysm, its morphology, the technique used, angiographic results and complications. Clinical follow-up was performed at one month, three months, six months, one year and yearly thereafter for a maximum of five years. Follow-up magnetic resonance imaging (MRI) was obtained at three months and control angiograms performed at six months.

 Results



Of the 22 patients, 14 were males, and the age ranged from 13 years to 63 years, with a mean age of 37 years. Five patients were in the paediatric age group. The clinical characteristics, investigative findings, treatment options, and outcomes are given in [Table 1],[Table 2] and [Table 3]. Most of the patients presented with features of mass effect: Headaches (18), cranial nerve palsies (5), focal neurological deficits, giddiness or vomiting. Three patients had subarachnoid hemorrhage (SAH).{Table 1}{Table 2}{Table 3}

Angiographic assessment

Giant partially thrombosed (GPT) aneurysms were identified on computed tomography (CT), MRI and angiography. The location of aneurysms was: Posterior cerebral artery (PCA) in 9 (4 on P1 segment and 5 on P2 segment), intradural vertebral artery (VA) in 6 aneurysms, basilar artery (BA) in 6, and one each aneurysm involving vertebrobasilar (VB) junction. All the aneurysms with SAH presentation were VB in location.

Endovascular treatment

Endovascular treatment was performed in all patients, with the aim of achieving alleviation of the symptoms and controlling further aneurysmal growth, possible future bleed and mass effect due to the aneurysm. Parent vessel sacrifice (PVS) was done in 13 patients, all having vertebral or PCA aneurysms [Figure 1]. Five giant BA/VB aneurysms were treated using flow reversal or flow diversion techniques. Flow reversal technique was used in the initial years (till 2004). Later on, telescoping stents were used to treat two patients with basilar aneurysms. In one of these patients, it was carried out as a staged procedure in two sessions. Besides these procedures, 1 patient with giant intradural VA aneurysm was treated by stent-assisted coiling [Figure 2] and 1 patient with PCA aneurysm was treated with selective coiling of the aneurysm with preservation of the parent vessel. Angiographic outcome at the end of the procedure was angiographic cure or stasis in the aneurysm in 21 (95%) patients.{Figure 1}{Figure 2}

Complications

There were 4 deaths and 5 had morbidity. Out of these nine patients with complications, 4 had midbasilar aneurysms managed by flow reversal technique. Two of these patients had good reformation up to the posterior inferior cerebellar artery (PICA) on angiography but died in the post-operative period because of brainstem ischemic stroke. Of the remaining two patients, one improved after adequate post-operative blood pressure maintenance with good outcome while the other patient remained in locked-in state [Figure 3]. On of the patients with patient VA developed progressive cranial nerve deficits and eventually expired. Of the 3 patients with PCA aneurysms, there was one death due to rebleed from small residue, while another patient had transient deterioration due to increased mass effect after occlusion with eventual good recovery. The third patient developed neurodeficit due to a perforator infarct with eventual good recovery. One patient with giant midbasilar aneurysm managed with telescoping stents developed posterior circulation stroke due to acute thrombosis of the stent. There was good reformation through both the PCoAs. He recovered partially with moderate persistent deficit. Of the 5 patients with morbidities, 3 had good eventual outcome, one had moderate permanent neurodeficit while one was in locked in state.{Figure 3}

Follow-up

Follow-up imaging was done in 18 patients (follow-up one month to five years) and 17 (94%) had stable occlusion of the aneurysm, while one patient treated by stent-assisted coiling had mild recanalization and coil compaction on check angiogram, but is clinically asymptomatic for three years since.

 Discussion



Giant intracranial aneurysms are less common in the posterior circulation, accounting for 6.1-6.9% of the posterior circulation aneurysms. [5],[7] The pathophysiology of giant intracranial aneurysms (aneurysmal vasculopathy) is complex, and is related to repeated subacute or chronic dissections and intramural hematomas, thrombus formation, recanalization and further bleeding. [8],[9] Triggering of various inflammatory mechanisms and proliferation of vasa vasorum play a role. [10],[11],[12] Advanced age, hypertension, tobacco use, coarctation, arteriovenous malformations, connective tissue disorders and vasculitis are also factors associated with aneurysm formation and rupture. [1],[13],[14] It has also been observed that aneurysms in the paediatric group tend to be larger, more complex and are more likely to be located in the posterior circulation. [15]

A slight male preponderance is reported in many series, [16],[17],[18] similar was the observation in our series. Some series report an equal gender ratio, [19],[20] while some reported a slight female preponderance. [1],[7],[21] The mean age of presentation is 36-44 [16],[17],[18],[19],[20],[21] and in our series, the mean age was 37 years. Headache and mass effect are the usual presenting symptoms. [16],[18],[19],[20] Hemorrhage is observed in 19-20% of patients. [6],[12],[17] In our study, 41% had PCA aneurysms, 32% had BA/VB aneurysms while 27% had VA aneurysms. In a series on large and giant (≥15 mm) aneurysms by van Rooij et al., [7] majority of the posterior circulation aneurysms involved the basilar artery (66%), followed by PICA, VA and PCA.

Endovascular management of giant posterior circulation aneurysms is a formidable challenge, and associated with a significantly higher proportion of worse clinical outcomes. [22] Treatment decisions are based on the aneurysmal location, size and collateral circulation. The endovascular treatment options include PVS, selective coiling while sparing the parent artery, flow reversal, stent-assisted coiling and flow diversion. Location of the aneurysm is an important determinant of the treatment strategy. Aneurysms involving only the intradural VA can safely be managed with occlusion and PVS if there is good support from the contralateral VA. If the collateral support is not adequate, the artery needs to be preserved and stent-assisted coiling or flow diversion are the preferred treatment strategies. In this study, there were six such patients, of which five were treated with PVS and one with stent-assisted coiling as it was the dominant VA. There was one death after PVS while the rest the patients had good outcomes.

Aymard et al. treated 21 VB aneurysm patients with unilateral or bilateral VA occlusion, and concluded that it is a safe and effective treatment for proximal aneurysms of the VB circulation. [23] Leibowitz et al. performed PVS in 13 patients of VB giant aneurysms and concluded that PVS is a useful therapeutic option and patients with aneurysms involving only one VA have better clinical outcomes than those with aneurysms involving BA or both Vas, as complete thrombosis cannot be achieved in the latter. [24] Gao et al. performed stent-assisted coiling in 72 large or giant aneurysms (≥15 mm), including 15 posterior circulation aneurysms (all VB), with only four complications. [25] Follow-up angiograms obtained in 59 aneurysms revealed recanalization in 17 patients (28.8%), of which 15 were re-embolized, while the remaining two had a mild stable re-growth in the aneurysm neck and were not retreated. They concluded that stent-assisted coiling is a safe and feasible treatment option. Wakhloo et al. studied stent-assisted treatment of 30 aneurysms including eight posterior circulation aneurysms treated with stent-assisted coiling. [26] They concluded that stent-assisted coiling is an attractive option with a stable long-term outcome. However, recanalization was observed up to 3 years after the initial obliteration, emphasizing the need for long-term follow-up.

Endovascular treatment of GPT aneurysms of the basilar territory is technically challenging and associated with high mortality and morbidity. Flow reversal was attempted in the initial years. Later on, with the availability of stents, stent-assisted coiling was done or telescoping stents were used. Flow diverters have revolutionized the management of these aneurysms. Although long-term results are not yet available, various studies demonstrated complete occlusion rates of approximately 93% using the Pipeline embolization device. [27],[28],[29] Due to the non-availability of flow diverters during the study period, there was no patient managed by true flow diversion reported in this series. A total of five patients with GPT aneurysms of the VB territory were managed by flow reversal, of which two died, one developed locked-in syndrome and one, after initial deterioration, eventually improved with good blood pressure control. These results demonstrate a high rate of complications, inspite of good angiographic reformation of the cerebellar arteries via the PCoAs. Sluzewski et al., in their study of six patients with giant VB aneurysms managed with flow reversal, reported 50% mortality. [30] They emphasized that the presence of two large PCoAs predicted good functional outcome, along with the clinical condition of the patient and the degree of brainstem compression and oedema at the time of presentation. Steinberg et al. demonstrated that patients with two large (>1 mm) PCoAs had better outcomes. [31] Boet et al. reported two patients with giant BA aneurysms managed by flow reversal technique with a 50% mortality rate. [32] They concluded that although flow reversal is a good treatment option for these lesions due to a high surgical risk, persistent incomplete aneurysmal thrombosis following flow-reversal should lead to the consideration of alternate treatment strategies.

Telescoping stents were used in recent patients with the intent of flow diversion and reduction in the inflow of blood into the aneurysm with induction of thrombosis. In this study, two patients with BA aneurysms were treated by telescopic stenting. One of them had a successful outcome while the other developed stent thrombosis and aneurysmal occlusion and neurodeficits. There were no deaths. However, study of a larger group of such patients is needed to establish the safety of the procedure. Wakhloo et al. reported six patients treated with stenting, including two posterior circulation aneurysms, with all six patients improving with no significant complications. [26]

Amongst the posterior circulation aneurysms, PCA territory is established to have more favorable prognosis as compared to other sites, [22],[33] and can safely be treated with PVS as long as adequate collaterals are present. In this study, there were nine patients with PCA aneurysms, of which eight were treated with PVS, while one patient was treated with selective coiling of the aneurysm due to lack of adequate collaterals. Two patients treated with PVS developed focal neurological deficit with good eventual recovery, while the patient treated with selective coiling died due to aneurysmal rebleed from a small residue. Hallacq et al. performed PVS in nine patients of P2 aneurysms, with none developing a neurological deficit. [20] They suggested that various potential collateral vessels to the distal PCA made P2 occlusion safe, as the aneurysm occurs distal to the origin of the perforating branches arising from P1. The authors did not use test occlusion when the planned occlusion involved the distal P2 segment. Ciceri et al. treated five patients of giant PCA aneurysms with PVS without BTO. [21] However, unlike the observations made by Hallacq et al., [20] in their series, one patient having a P2-P3 junction giant aneurysm developed PCA territory stroke. They concluded that giant PCA aneurysms can be effectively treated by PVS, but a thorough knowledge of the PCA segmental anatomy is crucial to select the appropriate site of occlusion. Overall, the risk of homonymous hemianopia after PVS ranges from 0-33%. [20],[21],[34],[35] In our series, two of the eight patients treated with PVS developed the same.

Coil embolization without PVS has been a modality of treatment of giant aneurysms. It has a low initial rate of complete occlusion (10-69%) but a high rate of recanalization of 56-90% due to coil compaction and aneurysmal regrowth. [6],[19],[36],[37],[38],[39],[40],[41],[42] van Rooij et al., in their study of coiling in very large and giant aneurysms in 44 patients (with 19 patients being additionally coiled at least once during follow-up), stated that coiling may be considered a staged treatment in many patients. [40] They concluded that long-term imaging follow-up and additional coiling when necessary is safe and effective in preventing rebleeds.

The drawback of this study is the relatively small cohort of 22 patients, although this remains the largest such cohort comprehensively analyzed. The increasing experience in the treatment of these aneurysms, rapidly evolving treatment strategies and the introduction of various newer techniques have lead to safer endovascular management of these aneurysms over time, as is evidenced by our experience.

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