Pipeline embolization device for posterior circulation aneurysm

Pipeline embolization device for posterior circulation aneurysm

The use of the pipeline embolization device (PED) for posterior circulation aneurysms remains controversial. In a meta-analysis, Liang et al., from the Beijing Tiantan Hospital and Beijing Tsinghua Changgung Hospital, aimed to explore the safety and efficacy of PED for these aneurysms. Meta regression was used to identify predictors for incomplete aneurysm occlusion and procedure-related complications.

PubMedWeb of Science, and OVID databases were searched to identify all published references evaluating the treatment effect of PED for posterior circulation aneurysms. Only studies written in English, reporting original data, and including more than 10 cases were considered for inclusion. Patient demographics, aneurysm characteristics, angiographic, and clinical outcomes were extracted. A random effects model was adopted to pool the obliteration rates and complications rates across selected studies. Finally, they conducted meta-regression analysis to identify the predictors of the angiographic outcomes.

12 studies, including 358 patients with 365 aneurysms were included. The pooled complete aneurysm obliteration rate was 82% (95% confidence interval [CI], 73%-90%) and the pooled procedure-related complication rate was 18% (95% CI, 14%-22%). Increasing age predicted incomplete obliteration of aneurysms after PED treatment in these patients (P=0.01).

PED is an alternative to treat intracranial aneurysms of the posterior circulation, achieving high complete occlusion rates, but less effective in senile patients. However, the risk of procedure-related complications is not negligible. Further larger and long-term follow-up studies are needed before definitive conclusions might be drawn 1).

From November 2015 to November 2016, 35 patients with 38 posterior circulation aneurysms were treated with the PED in this retrospective study. We evaluated the angiographic and clinical outcomes of these aneurysms at last follow-up, and made a comparison between anterior (n = 163) and posterior circulation (n = 38) aneurysms regarding the technical nuances, occlusion rate, complications rate, and time to occlusion to explore whether we should rationalize the use of the PED for these aneurysms.

With a median follow-up time of 5.5 months, complete occlusion was achieved in 33 aneurysms (91.7%). Aneurysms with stenosis parent artery tended to have lower occlusion rate (P = 0.064; odds ratio, 0.074; 90% confidence interval, 0.001-1.781), and V4 segment aneurysms tended to occlude themselves much faster than vertebrobasilar junction aneurysms (median, 148 vs. 246 days, respectively; P = 0.076). The periprocedural complication rate was 10.8%, and no major adverse events occurred. Compared with anterior circulation aneurysms, shorter procedure time (116.0 vs. 135.4 minutes, P = 0.012) and higher occlusion rate (91.4% vs. 72.8%, P = 0.023) were achieved for posterior circulation aneurysms. Besides, technical event rate (8.1% vs. 14.1%, P = 0.424) and complication rate (10.8% vs. 18.4%, P = 0.338) tended to be lower. Survival analysis indicated a shorter interval to complete occlusion for V4 segment aneurysms compared with anterior circulation (148 vs. 191 days, respectively; P = 0.047).

PED has a favorable performance at posterior circulation, and it is rational to expand the indication to include these aneurysms. However, a case-control study is still needed to further expatiate whether the PED has advantages over traditional endovascular treatment 2).

In 2018, a retrospective review of prospectively maintained databases at 8 academic institutions was performed for the years 2009 to 2016 to identify patients with posterior circulation aneurysms treated with PED placement.

A total of 129 consecutive patients underwent 129 procedures to treat 131 aneurysms; 29 dissecting, 53 fusiform, and 49 saccular lesions were included. At a median follow-up of 11 months, complete and near-complete occlusion was recorded in 78.1%. Dissecting aneurysms had the highest occlusion rate and fusiform the lowest. Major complications were most frequent in fusiform aneurysms, whereas minor complications occurred most commonly in saccular aneurysms. In patients with saccular aneurysms, clopidogrel responders had a lower complication rate than did clopidogrel nonresponders. The majority of dissecting aneurysms were treated in the immediate or acute phase following subarachnoid hemorrhage, a circumstance that contributed to the highest mortality rate in those aneurysms.

In the largest series till 2018, fusiform aneurysms were found to have the lowest occlusion rate and the highest frequency of major complications. Dissecting aneurysms, frequently treated in the setting of subarachnoid hemorrhage, occluded most often and had a low complication rate. Saccular aneurysms were associated with predominantly minor complications, particularly in clopidogrel nonresponders 3).

In 2015, a case series publication of Albuquerque et al. stated that patient selection is essential for safe and effective PED treatment of posterior circulation aneurysms. The PED is equally effective in achieving aneurysm obliteration with an acceptable risk profile as it is in the anterior circulation. Dolichoectatic aneurysms were not included in this treatment cohort. PED may be a preferable alternative to open surgical treatment of posterior circulation aneurysms 4).



Liang F, Zhang Y, Yan P, Ma C, Liang S, Jiang C. Outcomes and complications after the use of the pipeline embolization device in the treatment of intracranial aneurysms of the posterior circulation: A systematic review and meta-analysis. World Neurosurg. 2019 Apr 5. pii: S1878-8750(19)30972-6. doi: 10.1016/j.wneu.2019.03.291. [Epub ahead of print] PubMed PMID: 30959253.

Liang F, Zhang Y, Guo F, Zhang Y, Yan P, Liang S, Jiang Y, Jiang P, Jiang C. Use of Pipeline Embolization Device for Posterior Circulation Aneurysms: Single-Center Experiences with Comparison with Anterior Circulation Aneurysms. World Neurosurg. 2018 Apr;112:e683-e690. doi: 10.1016/j.wneu.2018.01.129. Epub 2018 Feb 2. PubMed PMID: 29410337.

Griessenauer CJ, Ogilvy CS, Adeeb N, Dmytriw AA, Foreman PM, Shallwani H, Limbucci N, Mangiafico S, Kumar A, Michelozzi C, Krings T, Pereira VM, Matouk CC, Harrigan MR, Shakir HJ, Siddiqui AH, Levy EI, Renieri L, Marotta TR, Cognard C, Thomas AJ. Pipeline embolization of posterior circulation aneurysms: a multicenter study of 131 aneurysms. J Neurosurg. 2018 Apr 1:1-13. doi: 10.3171/2017.9.JNS171376. [Epub ahead of print] PubMed PMID: 29726768.

Albuquerque FC, Park MS, Abla AA, Crowley RW, Ducruet AF, McDougall CG. A reappraisal of the Pipeline embolization device for the treatment of posterior circulation aneurysms. J Neurointerv Surg. 2015 Sep;7(9):641-5. doi: 10.1136/neurintsurg-2014-011340. Epub 2014 Aug 4. PubMed PMID: 25092926.

NSQIP unruptured aneurysm scale

NSQIP unruptured aneurysm scale

Data on patients who underwent surgical clipping of an unruptured aneurysm were extracted from the prospective National Surgical Quality Improvement Program registry (NSQIP; 2007-2014); NSQIP does not systematically collect data on patients undergoing intracranial endovascularinterventionMultivariable logistic regression evaluated predictors of any 30-day adverse event; variables screened included patient demographicscomorbiditiesfunctional status, preoperative laboratory values, aneurysm location/complexity, and operative time. A predictive scale was constructed based on statistically significant independent predictors, which was validated using both NSQIP (2015-2016) and the Nationwide Inpatient Sample (NIS; 2002-2011).

The NSQIP unruptured aneurysm scale was proposed: 1 point was assigned for a bleeding disorder; 2 points for age 51-60 years, cardiac disease, diabetes mellitus, morbid obesity, anemia (hematocrit < 36%), operative time 240-330 minutes; 3 points for leukocytosis (white blood cell count > 12,000/μL) and operative time > 330 minutes; and 4 points for age > 60 years. An increased score was predictive of postoperative stroke or coma (NSQIP: p = 0.002, C-statistic = 0.70; NIS: p < 0.001, C-statistic = 0.61), a medical complication (NSQIP: p = 0.01, C-statistic = 0.71; NIS: p < 0.001, C-statistic = 0.64), and a nonroutine discharge (NSQIP: p < 0.001, C-statistic = 0.75; NIS: p < 0.001, C-statistic = 0.66) in both validation populations. Greater score was also predictive of increased odds of any adverse event, a major complication, and an extended hospitalization in both validation populations (p ≤ 0.03).

The NSQIP unruptured aneurysm scale may augment the risk stratification of patients undergoing microsurgical clipping of unruptured cerebral aneurysm1).


Dasenbrock HH, Rudy RF, Smith TR, Gormley WB, Patel NJ, Frerichs KU, Aziz-Sultan MA, Du R. Adverse events after clipping of unruptured intracranial aneurysms: the NSQIP unruptured aneurysm scale. J Neurosurg. 2019 Mar 15:1-10. doi: 10.3171/2018.12.JNS182873. [Epub ahead of print] PubMed PMID: 30875693.

Small intracranial aneurysm

Small intracranial aneurysm


Small intracranial aneurysm size: 3-4 mm.

Of 26 studies, 5, 10, and 8 described the growth rate of aneurysms 3 mm and smaller, 5 mm and smaller, and 7 mm and smaller, respectively, whereas rupture rates were reported in 7, 11, and 13 studies for aneurysms 3 mm and smaller, 5 mm and smaller, and 7 mm and smaller, respectively. The annualized growth rate was less than 3% in all but 1 study for all 3 size categories. The annualized rupture rate was 0%, less than 0.5%, and less than 1% for the 3 size categories, respectively. Strength of evidence was very low quality for growth rates and low quality for rupture rates.

Poor-quality evidence suggests that small UIAs have low growth and rupture rates and very small UIAs have little or no risk for rupture 1).

The annual rupture rate of small (3-4 mm) unruptured intracranial aneurysms (UIA) is 0.36% per year, however, the proportion of small ruptured aneurysms < 5 mm is 35%. This discrepancy is explained by the hypothesis that most acute subarachnoid hemorrhage (SAH) is from recently formed, unscreened aneurysms, but this hypothesis is without definitive proof.

Ikawa et al., aimed to clarify the actual number of screened, ruptured small aneurysms and risk factors for rupture.

The Unruptured Cerebral Aneurysm Study Japan, a project of the Japan Neurosurgical Society, was designed to clarify the natural course of UIAs. From January 2001 through March 2004, 6697 UIAs among 5720 patients were prospectively registered. At registration, 2839 patients (49.6%) had 3132 (46.8%) small UCAs of 3-4 mm. The registered, treated, and rupture numbers of these small aneurysms and the annual rupture rate were investigated. The rate was assessed per aneurysm. The characteristics of patients and aneurysms were compared to those of larger unruptured aneurysms (≥ 5 mm). Cumulative rates of SAH were estimated per aneurysm. Risk factors underwent univariate and multivariate analysis.

Treatment and rupture numbers of small UCAs were 1132 (37.1% of all treated aneurysms) and 23 (20.7% of all ruptured aneurysms), respectively. The registered, treated, rupture number, and annual rupture rates were 1658 (24.8%), 495 (16.2%), 11 (9.9%), and 0.30%, respectively, among 3-mm aneurysms, and 1474 (22.0%), 637 (20.9%), 12 (10.8%), and 0.45%, respectively, among 4-mm aneurysms. Multivariate risk-factor analysis revealed that a screening brain checkup (hazard ratio [HR] 4.1, 95% confidence interval [CI] 1.2-14.4), history of SAH (HR 10.8, 95% CI 2.3-51.1), uncontrolled hypertension (HR 5.2, 95% CI 1.8-15.3), and location on the anterior communicating artery (ACoA; HR 5.0, 95% CI 1.6-15.5) were independent predictors of rupture.

Although the annual rupture rate of small aneurysms was low, the actual number of ruptures was not low. Small aneurysms that ruptured during follow-up could be detected, screened, and managed based on each risk factor. Possible selection criteria for treating small UCAs include a history of SAH, uncontrolled hypertension, location on the ACoA, and young patients. Further large prospective and longitudinal trials are needed.Clinical trial registration no.: C000000418 (https://www.umin.ac.jp/ctr2).

From September 2000 to January, 2004, 540 aneurysms (446 patients) were registered. Four hundred forty-eight unruptured aneurysms <5 mm in size (374 patients) have been followed up for a mean of 41.0 months (1306.5 person-years) to date.

Sonobe et al., calculated the average annual rupture rate of small unruptured aneurysms and also investigated risk factors that contribute to rupture and enlargement of these aneurysms.

The average annual risks of rupture associated with small unruptured aneurysms were 0.54% overall, 0.34% for single aneurysms, and 0.95% for multiple aneurysms. Patient <50 years of age (P=0.046; hazard ratio, 5.23; 95% CI, 1.03 to 26.52), aneurysm diameter of >or=4.0 mm (P=0.023; hazard ratio, 5.86; 95% CI, 1.27 to 26.95), hypertension (P=0.023; hazard ratio, 7.93; 95% CI, 1.33 to 47.42), and aneurysm multiplicity (P=0.0048; hazard ratio, 4.87; 95% CI, 1.62 to 14.65) were found to be significant predictive factors for rupture of small aneurysms.

The annual rupture rate associated with small unruptured aneurysms is quite low. Careful attention should be paid to the treatment indications for single-type unruptured aneurysms <5 mm. If the patient is <50 years of age, has hypertension, and multiple aneurysms with diameters of >or=4 mm, treatment should be considered to prevent future aneurysmal rupture 3).


Endovascular treatment of small intracranial aneurysms has historically been technically challenging and has been associated with high rates of complications and intraprocedural rupture.

A retrospective cohort study was performed to include all patients who underwent coiling of an intracranial aneurysm between 2005 and 2012. Small aneurysms were defined as any aneurysm 4.0 mm or smaller in all dimensions. The primary outcome was a composite outcome of the occurrence of an intraoperative aneurysm rupture or a perioperative thromboembolic event. The secondary outcome of interest was aneurysm recurrence.

483 patients were treated using endovascular techniques; 85 (17.6%) of these patients had small aneurysms. In the small aneurysm group, there was only one (1.2%) intraoperative rupture, three (3.5%) perioperative thromboembolic events, and 11 (12.9%) incidents of aneurysm recurrence. Both the primary and secondary outcomes of interest were similar in patients presenting with small or large aneurysms. Small aneurysm size was not a risk factor for either the composite primary outcome or aneurysm recurrence in multivariate analysis.

Treatment of small intracranial aneurysms via conventional endovascular coiling techniques is not inferior to endovascular treatment of larger aneurysms based on this single institution experience. While technically challenging, such aneurysms may be treated safely and effectively with acceptable rates of complications and recurrence 4).



Malhotra A, Wu X, Forman HP, Grossetta Nardini HK, Matouk CC, Gandhi D, Moore C, Sanelli P. Growth and Rupture Risk of Small Unruptured Intracranial Aneurysms: A Systematic Review. Ann Intern Med. 2017 Jul 4;167(1):26-33. doi: 10.7326/M17-0246. Epub 2017 Jun 6. Review. PubMed PMID: 28586893.

Ikawa F, Morita A, Tominari S, Nakayama T, Shiokawa Y, Date I, Nozaki K, Miyamoto S, Kayama T, Arai H; Japan Neurosurgical Society for UCAS Japan Investigators. Rupture risk of small unruptured cerebral aneurysms. J Neurosurg. 2019 Jan 25:1-10. doi: 10.3171/2018.9.JNS181736. [Epub ahead of print] PubMed PMID: 30684948.

Sonobe M, Yamazaki T, Yonekura M, Kikuchi H. Small unruptured intracranial aneurysm verification study: SUAVe study, Japan. Stroke. 2010 Sep;41(9):1969-77. doi: 10.1161/STROKEAHA.110.585059. Epub 2010 Jul 29. PubMed PMID: 20671254.

Stetler WR Jr, Wilson TJ, Al-Holou WN, Chaudhary N, Gemmete JJ, Thompson BG, Pandey AS. Conventional endovascular treatment of small intracranial aneurysms is not associated with additional risks compared with treatment of larger aneurysms. J Neurointerv Surg. 2014 Mar 12. doi: 10.1136/neurintsurg-2014-011133. [Epub ahead of print] PubMed PMID: 24623836.
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