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Table of Contents    
Year : 2020  |  Volume : 68  |  Issue : 1  |  Page : 116-117

Flow Diversion for Giant Intracranial Aneurysms: Problem or Panacea?

1 Department of Neurological Surgery, Jaslok Hospital and Research Centre, Mumbai, Maharashtra, India
2 Department of Neurological Surgery, Manipal Hospital, Bengaluru, Karnataka, India

Date of Web Publication28-Feb-2020

Correspondence Address:
Dr. Sudheer Ambekar
Department of Neurological Surgery, Jaslok Hospital and Research Centre, 15, Dr. Deshmukh Marg, Mumbai - 400 026, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.279685

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How to cite this article:
Ambekar S, Pandey P. Flow Diversion for Giant Intracranial Aneurysms: Problem or Panacea?. Neurol India 2020;68:116-7

How to cite this URL:
Ambekar S, Pandey P. Flow Diversion for Giant Intracranial Aneurysms: Problem or Panacea?. Neurol India [serial online] 2020 [cited 2020 Apr 4];68:116-7. Available from:

Although giant intracranial aneurysms (GIAs) represent only 2–7% of all IAs, they are one of the most difficult lesions to treat.[1] Large sizes (>2.5 cm) causing mass effect, the presence of calcification, thrombus, their incorporation of parent, and/or branch arteries make treatment challenging. The surgical techniques that are used in the management of GIAs include microsurgical clip reconstruction, parent artery ligation, and trapping with bypass.

With the advent of endovascular surgery, an increasing number of aneurysms are being treated endovascularly each year and with equivalent results as those with surgery. However, the results of simple coiling and balloon/stent-assisted coiling for GIAs have not been encouraging with a high incidence of morbidity (17.2%), mortality (7.7%), and recanalization (27%).[2] The introduction of flow-diverting devices provided another tool in the armamentarium for treatment of the GIAs. The Pipeline embolization device (PED, ev3/Covidien, Plymouth, MN, USA), a braided, tubular, bimetallic endoluminal implant composed of 48 individual microfilaments prepared using 25% platinum and 75% cobalt chromium, provides 30~35% metal coverage of the inner surface of the target vessel. Because of the low porosity (0.02–0.05 mm2) of this device, hemodynamic flow from the parent vessel cannot enter the aneurysm and sufficient scaffolding is provided to support neointimal regeneration of the neck. It received CE (Conformité Européene) mark approval in 2008 for the embolization of cerebral aneurysms and received US Food and Drug Association approval in 2011 for the treatment of large and giant wide-neck aneurysms in the internal carotid artery, from the petrous to the superior hypophyseal segments.[3]

In the present study titled “A Systematic Review of Pipeline Embolization Device for Giant Intracranial Aneurysms,” the authors performed a systematic review of all GIAs treated with PED. Not surprisingly, the cumulative mortality rate for anterior circulation GIAs was 9.1%; however, that for posterior circulation GIAs was 94.4%. Complete aneurysm occlusion was achieved in 57.5% cases at follow-up. Certain limitations of the study should be noted. The very high mortality rate of 94.4% for posterior circulation aneurysms does not indicate the true mortality rate due to selection bias. The vertebrobasilar group was not subtyped based on the type of aneurysm (fusiform or saccular) and location. In the International Retrospective Study of the Pipeline Embolization Device (IntrePED), 7.3% of the aneurysms treated were ≥25 mm. The mortality rate was significantly higher in patients with giant aneurysms compared with those with large and small aneurysms (9.6% versus 5.0% versus 1.8%, respectively, P < 0.01). Although the overall post-treatment rupture rate was <1%, three out of five aneurysms that ruptured following flow diversion were GIAs. The overall neurologic morbidity and mortality in posterior circulation giant aneurysms was 40%.[4] In a meta-analysis, Brinjikji et al. found an overall postoperative rupture rate of 4%, with an early rupture rate of 3% and a significantly higher rupture rate in large and giant aneurysms.[5] Using coils along with PED has been suggested to improve occlusion rates and reduce the incidence of post-treatment rupture. Given these results, treatment of giant aneurysms with flow diverting devices should be considered with caution.

The pathophysiology of aneurysm wall and perianeurysmal wall changes following flow diversion has not been completely understood. GIAs differ from other saccular aneurysms in that they often are thrombosed, cause mass effect over the surrounding structures, and might lead to perianeurysmal inflammatory reaction. Rapid thrombosis of a giant aneurysm following flow diversion may lead to perianeurysmal inflammatory reaction and increase in the mass effect. In a series of 17 patients with unruptured aneurysms treated with flow diversion, neurologic worsening was observed in 41% of the patients.[6] With coils, the inflammatory reaction occurs in 18% of the patients, but is often asymptomatic.[7] Parent artery sacrifice has also been reported to produce inflammatory reaction, however, surgical clipping does not, possibly due to puncture of the aneurysm wall during surgery. This inflammatory reaction is less often seen with cavernous carotid aneurysms because of their extradural location, thus explaining excellent results following flow diversion of these lesions. One of the proposed mechanisms for this reaction is the release of proinflammatory mediators (inflammasome, caspase 1, IL1β, and NF-κB) due to endothelial wall ischemia resulting from thrombosis of the aneurysm. Steroids have been used in such patients with limited success.[6]

To conclude, the pathophysiological changes following flow diversion of GIAs have not been completely understood. Flow-diverting devices should be used with utmost caution and appropriate case selection in the treatment of GIAs. Microsurgical techniques still have a significant role in the management of these challenging lesions.

  References Top

Battaglia R, Pasqualin A, Da Pian R. Italian cooperative study on giant intracranial aneurysms: 1. Study design and clinical data. Acta Neurochir Suppl 1988;42:49-52.  Back to cited text no. 1
Parkinson RJ, Eddleman CS, Batjer HH, Bendok BR. Giant intracranial aneurysms: Endovascular challenges. Neurosurgery 2008;62 (6 Suppl 3):1336-45.  Back to cited text no. 2
Becske T, Kallmes DF, Saatci I, McDougall CG, Szikora I, Lanzino G, et al. Pipeline for uncoilable or failed aneurysms: Results from a multicenter clinical trial. Radiology 2013;267:858-68.  Back to cited text no. 3
Kallmes DF, Hanel R, Lopes D, Boccardi E, Bonafnafora I, Lanzino G, G, urysms: anialretrospective study of the pipeline embolization device: A multicenter aneurysm treatment study. Am J Neuroradiol 2015;36:108-15.  Back to cited text no. 4
Brinjikji W, Murad MH, Lanzino G, Cloft HJ, Kallmes DF. Endovascular treatment of intracranial aneurysms with flow diverters: A meta-analysis. Stroke J Cereb Circ 2013;44:442-7.  Back to cited text no. 5
Berge J, Tourdias T, Moreau JF, Barreau X, Dousset V. Perianeurysmal brain inflammation after flow-diversion treatment. AJNR Am J Neuroradiol 2011;32:1930-4.  Back to cited text no. 6
Fanning NF, Willinsky RA, Brugge KG ter. Wall enhancement, edema, and hydrocephalus after endovascular coil occlusion of intradural cerebral aneurysms. J Neurosurg 2008;108:1074-86.  Back to cited text no. 7


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