Blister-like aneurysms of the internal carotid artery - management considerations

Computational hemodynamic pathophysiology of internal carotid artery blister aneurysms

OBJECTIVE

Blister aneurysms of the internal carotid artery (ICA) are rare and are primarily documented in the literature through small series and case reports. The intraoperative observation of a hemorrhage in the artery wall proximal to the aneurysmal bulge led to the hypothesis that some of these aneurysms might develop in a retrograde manner.

METHODS

We developed software to reconstruct the ICA with and without Type I and II blister aneurysms using patients' imagery as input to simulate hemodynamic conditions before and after their formation. Kinematic blood flow data before and after aneurysm formation were obtained using a finite volume solver. We compared the wall shear stress (WSS) distribution of the arterial wall prior to aneurysm formation.

RESULTS

In two out of four cases, WSS was significantly elevated on the dorsal wall of the supraclinoid segment of the ICA at the distal part of the future site of the aneurysm sac, suggesting that the aneurysm sac may ultimately develop in a retrograde fashion. Once the structural changes have been initiated, WSS gradient (WSSG) was significantly elevated at the proximal and distal boundaries of the bulging aneurysmal pouch. Low WSS and high WSSG at the proximal part of the aneurysm sac seem to contribute to the extension of the proximal intramural hematoma observed during blister aneurysm surgery.

CONCLUSIONS

By enabling assessment of the impact of elevated WSS and its gradient, our computational pipeline supports the hypothesis that the development of blister aneurysms may occur either in a retrograde or anterograde fashion.

Single-Cell RNA Sequencing Reveals the Pathogenic Relevance of Intracranial Atherosclerosis in Blood Blister-Like Aneurysms

Background

Intracranial non-branching site blood blister-like aneurysms (BBA) are extremely rare and vicious. Their etiology remains elusive, and no molecular study has been carried out to reveal its pathogenic relevance to intracranial atherosclerosis. To investigate its transcriptomic landscape and underlying potential pathogenesis, we performed single-cell RNA sequencing with extensive pathological validation.

Methods

In total, 12,245 cells were recovered for single-cell RNA sequencing analysis from 1 BBA and 2 saccular intracranial aneurysms (IAs). Unbiased clustering using Seurat-based pipeline was used for cellular landscape profiling. Cellchat was used to understand intracellular communications. Furthermore, 10 BBAs and 30 IAs were retrospectively collected for pathological validations like scanning electron microscopy, H&E stain, Masson stain, Verhoeff Van Gielson stain, and immunofluorescence.

Results

Single-cell transcriptome profiled 14 total subclusters in 6 major groups, namely, 6 monocyte/macrophage clusters, 2 T&NK clusters, 3 vascular smooth muscle cell (VSMC) clusters, 1 dendritic cell, 1 B cell, and 1 endothelial cell cluster. The only mural cell identified in BBAs was VSMC-2 cluster, while mural cells in IAs comprise most clusters of VSMCs and endothelial cells. Upregulated genes in BBA-derived VSMCs are related to arterial mineralization and atherosclerosis, such as PTX3, SPP1, LOX, etc., whereas vasodilation and physiological regulatory genes such as MGP, ACTA2, and MYL9 were conversely enriched in conventional IA-derived VSMCs. Immune cells in the BBA were predominantly macrophages, with a low fraction of T&NK cells, while conventional IAs had a higher percentage of T&NK. Gene enrichment analysis suggested that macrophages in BBA were highly enriched in lipid metabolism as well as atherosclerosis. Ligand–receptor interaction suggested that secretory phosphoprotein 1 (also known as osteopontin) played a major role in mediating the intracellular communication between VSMC and macrophages, especially in BBA. Pathological experiments corroborate with the bioinformatic findings and further characterized BBAs as a thin-walled thrombotic aneurysm with severe atherosclerotic lesions, where ApoE+ macrophages and OPN+ mural cells are intimately involved in the inflammation process.

Conclusions

The preexisting intracranial atherosclerosis might predispose the parent artery to the pathogenic occurrence of BBAs. These data shed light on the pathophysiology of intracranial aneurysms and might assist in the further resolution of the complexity in aneurysm pathogenesis.

Wrap-Clipping for Patients with Ruptured Blood Blister-Like Aneurysms of the Internal Carotid Artery: Case Series and Literature Review

OBJECTIVE

 Blood blister-like aneurysms (BBAs) of the internal carotid artery (ICA) are challenging to treat. We assessed the clinical and radiologic outcomes in patients with ruptured BBAs of the ICA treated with wrap-clipping.

METHODS

 From November 2016 to January 2020, the clinical and radiologic data of patients with subarachnoid hemorrhage (SAH) caused by ICA BBAs who underwent wrap-clipping were retrospectively analyzed. The clinical outcomes were evaluated according to the modified Rankin Scale (mRS). Radiologic follow-up examinations included digital subtraction angiography (DSA), computed tomography angiography (CTA), and magnetic resonance angiography (MRA).

RESULTS

 Seven patients were enrolled in this study. All BBAs were wrap-clipped successfully, including two BBAs that exhibited intraoperative bleeding and required balloon-assistance during surgery. All patients had favorable clinical outcomes during follow-up. Among the six patients who completed the radiologic follow-up visit, one patient presented ICA occlusion at the 6-month DSA follow-up, but no neurologic dysfunction was noted. We did not observe the progression of ICA stenosis in other patients.

CONCLUSION

 All BBAs in this study were wrap-clipped successfully and completely occluded. Wrap-clipping is effective for BBAs of the ICA and has favorable clinical outcomes. A multicenter study with a large sample size and a longer radiologic follow-up is necessary.

Current Knowledge of and Perspectives about the Pathogenesis of Blood Blister-like Aneurysms of the Internal Carotid Artery: A Review of the Literature

Blood blister-like aneurysms (BBAs) are rare and usually appear at nonbranching sites in the supraclinoid portion of the internal carotid artery (ICA). Because it is difficult to obtain histological specimens of the aneurysm wall and because experimental models are challenging to establish, the pathogenesis of BBAs remains uncertain. In this paper, we reviewed the diagnostic, radiological, and pathophysiological characteristics of patients with BBAs. We also summarized the existing evidence and potential mechanisms related to the causes of BBAs. Current evidence indicates that atherosclerosis and dissection are the main prerequisites for the formation of BBAs. Hemodynamics may play a role in the process of BBA formation due to the unique vascular anatomy of the supraclinoid ICA. Further research on histopathology and hemodynamics is warranted in this field.

Blister aneurysms of the internal carotid artery: Surgical treatment and management outcome from a single center experience

OBJECTIVE

Blood-blister aneurysms (BBAs) of the internal carotid artery (ICA) are rare entities, but clinically important cause of subarachnoid hemorrhage (SAH). Several surgical and endovascular strategies have been attempted for these heterogeneous lesions. In this study, the authors analyzed the treatment strategy and outcomes in a series of cases of ICA blister aneurysms treated microsurgically.

PATIENTS AND METHODS

We retrospectively reviewed 15 consecutive cases of patients harboring ruptured BBAs, microsurgically treated at our institution between 2014 and 2018. We performed an analysis of the clinical and surgical aspects, as well as post-operative angiograms and outcomes.

RESULTS

Fifteen patients were identified; 9 (60%) were female. The mean age of presentation was 43,8 years. Most patients presented in good clinical conditions (Hunt-Hess 1-3 = 86%). The most common Fisher grade at presentation was 3 (60% of cases). All patients underwent digital subtraction angiography (DSA), revealing broad-based aneurysms at non-branching sites on the dorsal wall of the ICA. Intraoperatively, BBAs were confirmed in all cases. The lesions were approached through pterional (11-73%) or lateral supraorbital (4-27%) craniotomy. Direct clipping was performed in all but one lesion, in which case the clip-wrapping technique was used. Final angiographic control revealed complete occlusion in 14 cases. One patient required reoperation due to residual aneurysm filling. At discharge, a good outcome (Glasgow Outcome Scale [GOS] 4 or 5) was observed in 12 (80%) patients. Three patients were discharged with a GOS of 3.

CONCLUSION

Blood-blister-type aneurysms are rare and challenging lesions. Preoperative knowledge and careful surgical planning can prevent poor clinical outcomes. Surgical treatment remains an effective and safe option in this context.

Outcome of a Blood Blister-Like Aneurysm Treated by Clip-Reinforced Wrapping Technique Using Y-Shaped Temporalis Fascia for Perforator Protection

BACKGROUND

The optimal approach of blood blister-like aneurysms (BBAs) is debated. Wrapping has been reported to be an effective strategy, but artificial materials have often been used. In addition, perforator protection is difficult using this technique. In this case, we report a ruptured BBA of the left internal carotid artery (ICA) treated with a clip-reinforced wrapping technique using Y-shaped autologous temporalis fascia to protect the posterior communicating artery (PComA). The outcome was favorable.

CASE DESCRIPTION

A 48-year-old woman was admitted for subarachnoid hemorrhage. Digital subtraction angiography (DSA) revealed a BBA located opposite the PComA origin. A frontotemporal craniotomy was performed. The temporalis fascia was isolated from the temporalis muscle, and then tailored into a Y shape for the PComA to pass through. The diseased segment and the BBA were then wrapped by the Y-shaped temporalis fascia circumferentially. Two clips were applied to the fascia to reinforce the wrapping to fit snugly enough around the parent artery subsequently. DSA and computed tomography angiography scan postoperation showed that the BBA had not recurred, the supraclinoid segment of the left ICA had reconstructed well, and the PComA was unobstructed. The patient recovered without any sequelae during the 1-year follow-up period.

CONCLUSIONS

A clip-reinforced wrapping technique using Y-shaped temporalis fascia may be an effective method for treating BBAs located opposite the PComA origin. Long-term follow-up and large sample size studies, however, are necessary to validate this approach.

Evaluation of Enterprise Stent-Assisted Coiling and Telescoping Stent Technique as Treatment of Supraclinoid Blister Aneurysms of the Internal Carotid Artery

BACKGROUND

Supraclinoid blister aneurysms (BAs) of the internal carotid artery are uncommon and deadly, and appropriate treatment is controversial. Endovascular reconstruction may allow treatment through aneurysm isolation. We report a single-institution experience in the use of Enterprise stent-assisted coiling (ESAC) for treating BAs to appraise the safety and efficacy of this technique.

METHODS

Patients treated with ESAC for a BA at our institution between 2013 and 2016 were retrospectively included in this study. Patients' aneurysm characteristics, progression status, aneurysm occlusion on follow-up angiography, and modified Rankin Scale (mRS) score were recorded and analyzed. Occlusion rates and neurologic outcomes were compared between patients treated with a single stent and those treated with multiple telescoping stents.

RESULTS

Forty-four patients were included (17 males; average age, 47.3 years), and ESAC was successfully performed in all patients. Immediate postprocedure angiography revealed complete occlusion in 23 patients (52.3%), residual neck in 15 (34.1%), and residual aneurysm in 6 (13.6%). Twenty patients (45.5%) suffered perioperative cerebral vasospasm, and 3 (6.8%) died of secondary ischemic stroke. The duration of follow-up ranged from 2.5 to 27 months (mean, 11.59 ± 5.76 months). One patient with recurrence was treated with additional coiling, and another patient was treated with a covered stent. The use of telescoping stents was associated with a better complete aneurysm occlusion rate compared with the use of single stents (84.4% [27 of 34] vs. 44.4% [4 of 9]; P = 0.04). Follow-up mRS score was ≤1 for 32 of 41 patients (78.4%).

CONCLUSIONS

ESAC to treat BAs is safe, effective, and provides good clinical outcomes. ESAC with telescoping stents has a higher follow-up complete occlusion rate compared with ESAC with single stents.

Treatment of ruptured blood blister aneurysms using primary flow-diverter stenting with considerations for adjunctive coiling: A single-centre experience and literature review

Objective The objective of this article is to conduct a single-centre evaluation and quick literature review of the effectiveness of primary flow-diverter (FD) treatment of ruptured blood blister aneurysms (BBAs), with additional relevance of adjunctive coiling. Methods Patients presenting with subarachnoid haemorrhage (SAH) due to ruptured BBAs and subsequently treated with FDs were retrospectively selected from June 2010 to January 2017. Treatment techniques, angiographic data on occlusion rates and procedural success as well as clinical outcomes using the modified Rankin Scale (mRS) were collated. Cross-reference of results were made with available literature. Results Thirteen patients harbouring 14 BBAs were recruited. Of the 14 aneurysms, five (35.7%) showed immediate complete occlusion after the procedure (four of these five patients had adjunctive coiling). All of the aneurysms showed complete occlusion by the six- to nine-month control diagnostic angiogram. No rebleed or retreatment was experienced. Twelve of 13 (92%) patients had an mRS score of 0-1 at the last clinical follow-up. From the pooled data of the literature review, eventual aneurysm occlusion was achieved in 48/56 patients, with five patients requiring further endovascular treatment. In the clinical follow-up period, an mRS of 0-2 was recorded for 83.3% (45/54) of patients. Conclusion Endovascular reconstruction of BBAs using FD treatment is an effective method with good final clinical outcomes. Adjunctive use of coiling achieves higher incidence of immediate complete occlusion of BBAs.

Endovascular Treatment of Ruptured Blister-Like Aneurysms: A Systematic Review and Meta-Analysis with Focus on Deconstructive versus Reconstructive and Flow-Diverter Treatments

BACKGROUND AND PURPOSE

Various endovascular techniques have been applied to treat blister-like aneurysms. We performed a systematic review to evaluate endovascular treatment for ruptured blister-like aneurysms.

MATERIALS AND METHODS

We performed a comprehensive literature search and subgroup analyses to compare deconstructive versus reconstructive techniques and flow diversion versus other reconstructive options.

RESULTS

Thirty-one studies with 265 procedures for ruptured blister-like aneurysms were included. Endovascular treatment was associated with a 72.8% (95% CI, 64.2%-81.5%) mid- to long-term occlusion rate and a 19.3% (95% CI, 13.6%-25.1%) retreatment rate. Mid- to long-term neurologic outcome was good in 76.2% (95% CI, 68.9%-8.4%) of patients. Two hundred forty procedures (90.6%) were reconstructive techniques (coiling, stent-assisted coiling, overlapped stent placement, flow diversion) and 25 treatments (9.4%) were deconstructive. Deconstructive techniques had higher rates of initial complete occlusion than reconstructive techniques (77.3% versus 33.0%, P = .0003) but a higher risk for perioperative stroke (29.1% versus 5.0%, P = .04). There was no difference in good mid- to long-term neurologic outcome between groups, with 76.2% for the reconstructive group versus 79.9% for the deconstructive group (P = .30). Of 240 reconstructive procedures, 62 (25.8%) involved flow-diverter stents, with higher rates of mid- to long-term complete occlusion than other reconstructive techniques (90.8% versus 67.9%, P = .03) and a lower rate of retreatment (6.6% versus 30.7%, P < .0001).

CONCLUSIONS

Endovascular treatment of ruptured blister-like aneurysms is associated with high rates of complete occlusion and good mid- to long-term neurologic outcomes in most patients. Deconstructive techniques are associated with higher occlusion rates but a higher risk of perioperative ischemic stroke. In the reconstructive group, flow diversion carries a higher level of complete occlusion and similar clinical outcomes.

Morphological aspects of blister aneurysms and nuances for surgical treatment

OBJECT

Blister aneurysms of the supraclinoid part of the internal carotid artery (ICA) are known for their high morbidity and mortality rates related to treatment, regardless of whether the treatment is surgical or endovascular. However, this grim prognosis is based on results that indiscriminately group all blister aneurysms together without taking into account the heterogeneous appearance of these lesions. The goal of this study was 2-fold: to determine whether different blister aneurysm morphologies present different pitfalls, which would then require different surgical strategies, as well as to determine whether there are identifiable subgroups of these types of aneurysms based on morphology.

METHODS

The authors reviewed the charts, cerebral catheter angiograms, surgical reports, and intraoperative videos of all ICA blister aneurysms treated surgically at the Centre Hospitalier de l'Université de Montréal from 2005 to 2012 to investigate whether there was a relationship between morphology and pitfalls, and whether different surgical strategies had been used according to these pitfalls. During this review process the authors noted 4 distinct morphological aspects. These 4 aspects led to a review of the English and French literature on blister aneurysms in which imaging was available, to determine whether other cases could also be classified into the same 4 subgroups based on these morphological aspects.

RESULTS

The retrospective review of the authors' series of 10 patients allowed a division into 4 distinct subtypes: Type I (classic), Type II (berry-like), Type III (longitudinal), and Type IV (circumferential). These subtypes may at times be progressive stages in the arterial anomaly, and could represent a continuum. Each subtype described in this paper presented its own pitfalls and required specific surgical adaptations. Upon reviewing the literature the authors retained 35 studies involving a total of 61 cases of blister aneurysms, and all cases were able to be classified into 1 of these 4 distinct subtypes.

CONCLUSIONS

Although they share some common characteristics, blister aneurysms may be divided into distinct subtypes, suggestive of a continuum. Such a classification with a detailed description of each type of blister aneurysm would allow for better recognition to anticipate complications during intervention and better assess the different treatment strategies according to the subtypes.