Considerations and Literature Review for Treating Subarachnoid Hemorrhage due to Blood Blister-Like Aneurysms.

Objective: Subarachnoid hemorrhage (SAH) due to blood blister-like aneurysm (BBA) is rare but very risky during treatment. Moreover, there is no established treatment method. In this study, we performed endovascular treatment (EVT) as the first-line treatment on patients with SAH during the subacute phase, and cases were analyzed in this series. Methods: Patients with SAH due to BBA who visited our hospital between April 2021 and March 2023 were enrolled in this study. We waited as long as possible during the acute phase and performed EVT during the subacute phase. We performed stent-assisted coiling (SAC) as the first-line treatment and performed DSA approximately 6 months after treatment. Results: Ninety-six patients with SAH visited our hospital during the study period and six had SAH due to BBAs. There were two males and four females aged 56.2 ± 14.6 years. We performed SAC in five patients, and one died owing to rebleeding before treatment. Two patients received treatments because of rebleeding. One patient died on the day after rebleeding, whereas the other experienced rebleeding and treatments twice and achieved a good outcome. Four patients had good outcomes (modified Rankin scale [mRS]: 0). The surviving patients achieved complete occlusion at follow-up DSA. However, two patients had poor outcomes (mRS: 6). Conclusion: Patients with SAH due to BBA treated in the subacute phase may achieve good outcomes; however, there is a risk of rebleeding during the waiting period, which often causes poor outcomes.

Advantages of 3D High-Resolution Vessel Wall Imaging in a Patient With Blood Blister-Like Aneurysm: A Case Report and Literature Review.

Blood blister-like aneurysms (BBAs) are rare and challenging intracranial aneurysms. They pose significant diagnostic and surgical risks due to their delicate walls. Accounting for a small percentage of intracranial aneurysms, BBAs are pathologically pseudoaneurysms, often resulting from arterial dissection, with a high tendency to rupture. This report underscores the critical nature of BBAs by reviewing a case in which subarachnoid hemorrhage caused by a BBA rupture was difficult to diagnose with conventional imaging. We highlight the efficacy of three-dimensional (3D) high-resolution vessel wall imaging (VWI) in discerning the subtle vascular abnormality of BBAs. The integration of the black-blood imaging technique within VWI provides superior contrast between the aneurysm and surrounding tissues, facilitating clearer visualization of the aneurysmal wall. The use of 3D T1-weighted imaging provides intricate details of the vessel wall including its contrast enhancement, which is crucial for a comprehensive assessment of a ruptured aneurysm. This case is consistent with the existing literature, supporting the role of VWI in the identification of ruptured BBAs, an area with limited but growing information on its diagnostic value. VWI is precise and accurate in the preoperative diagnosis of BBAs, emphasizing its potential to improve patient management and outcomes, especially in conditions with high risks of morbidity and mortality.

Compatibility of the semijailing technique with extremely soft i-ED coils for ruptured blood blister-like and dissecting aneurysms: patient series.

BACKGROUND: Optimal treatment options for ruptured blood blister-like aneurysms (BBAs) and dissecting aneurysms (DAs) have not yet been established. Endovascular treatment may achieve vessel reconstruction with the preservation of antegrade blood flow; however, securing curative hemostasis at the fragile rupture point remains a major concern. OBSERVATIONS: Two ruptured BBAs and two ruptured DAs treated by stent-assisted coiling with the semijailing technique in the last 2 years are described herein. The devices used were braided stents and i-ED coils, which are new low-memory shape and extremely soft coils. Neither rebleeding nor ischemic complications were observed. All patients had a favorable outcome and showed no recurrence after treatment. LESSONS: All aneurysms were treated without ischemic complications or rebleeding. The good compatibility of braided stents and the new concept coils in stent-assisted coiling by the semijailing technique provides insight into these intractable hemorrhagic vascular pathologies.

Willis covered stent in the treatment of a recurrent blood blister-like aneurysm after pipeline implementation: A case report.

Blood blister-like aneurysms (BBAs) are fragile and difficult to treat. However, the optimal treatment has yet to be determined. Pipeline embolization devices and Willis covered stent implementation are still controversial strategies for treating BBA. Herein, we report a case of recurrent BBA successfully treated with a Willis covered stent. A long-term follow-up angiography after the procedure indicated complete occlusion of the aneurysm. This case demonstrates the safety and efficacy of applying the Wills cover stent in the treatment of recurrent BBA after Pipeline implantation.

Long-Term Outcomes of Ruptured Blood Blister-Like Aneurysms with Multiple (≥2) Overlapping Stents and Coiling: A Single-Center Experience.

OBJECTIVE: To evaluate the long-term feasibility of multiple overlapping stents (≥2) with or without coiling for treating blood blister-like aneurysms (BBAs). METHODS: BBAs treated with stent-assisted coiling or stent-only therapy wasincluded. BBAs with atypical anatomical locations, other endovascular or surgical techniques performed, and delayed treatment (>48 hours) were excluded. Medical records of patients and procedures were retrospectively reviewed. RESULTS: Seventeen patients with BBAs were identified, and 15 were treated with stent-assisted coiling and 2 with stent-only therapy. Triple overlapping stents were performed in seven patients, double stents in nine, and a single stent with coiling in 1. One patient experienced in-stent fibrin formation and received intra-arterial tirofiban. Complementary treatment was required in four patients. Three patients were initially treated with double (3/9) and 1 with triple stents (1/7). Three recurred in the acute period (≤6 weeks) and 1 recurred 14 months after treatment. Three of 17 patients with Hunt Hess grade 5 died early. Thirteen patients were available for long-term angiographic follow-up (13.8 ± 8.9 months). Final angiography showed complete aneurysm occlusion in all patients without in-stent stenosis or perforating vessel occlusion. Clinical follow-up data were available for all 14 surviving patients (66.8 ± 40.9 months). Eight patients had favorable outcomes, five had unfavorable outcomes, and 1 died of a subarachnoid hemorrhage-unrelated cause. Delayed infarct or hemorrhage was not documented. CONCLUSIONS: Even in the era of flow diverter stents, the use of multiple overlapping stents with or without coiling can be a feasible alternative for treating ruptured BBAs.

Flow Diverter Device-Assisted Coiling Treatment for Cerebral Blister Aneurysm: A Single-Center Study.

Although endovascular treatment is a promising approach, blood blister-like aneurysms (BBAs) still present treatment challenges. This study aimed to assess the effectiveness and safety of flow diverter device-assisted coiling (FDDAC) for the treatment of BBAs, which are broad based and friable with a high rebleeding risk. Eight patients (five females and three males) who presented with subarachnoid hemorrhages (SAH) due to BBA ruptures between May 2020 and May 2022 were retrospectively enrolled. All patients were treated by flow diverter device (Tubridge) adjunctive coil embolization using a semi-deploying technique. The demographic information, angiographic data, interval between admission and treatment, materials, therapy, clinical outcomes (including periprocedural and intraprocedural mortality and morbidity), and follow-up results of all patients were reviewed. The mean age of the patients with BBAs was 48.5 years (range 31-62 years); aneurysm sizes ranged from 2.2 × 1.7 mm to 4.6 × 3.2 mm, and the median Hunt-Hess score was 3. All aneurysms were completely closed at follow-up, and all 8 patients had excellent clinical outcomes (modified Rankin scores = 0-2) at discharge. Angiograms showed complete aneurysm occlusion after 6 months to 1 year. In addition, there were no cases of re-rupture, re-treatment, or recurrence of the aneurysms. FDDAC is safe to use in patients with BBAs and provides an alternative treatment option for this disease.

Endovascular Treatment of Ruptured Blood Blister-like Aneurysms Using the LVIS EVO Stents.

Blood blister-like aneurysms (BBAs) are rare cerebrovascular lesions that face serious challenges in surgical as well as endovascular treatment. In this paper, we present our experience in treating BBAs using the LVIS EVO stents. A total of 10 patients (mean age of 56.1 years) with 13 BBAs, who were admitted to our university hospital between April 2020 and November 2021 with a subarachnoid hemorrhage (SAH) due to aneurysm rupture, were treated using the LVIS EVO stents. Treatment of the BBAs consisted of stent-assisted coiling in four patients and stenting in six patients. The aneurysms were located within ICA (84.6%), VA (7.7%), and MCA (7.7%). Placement of the LVIS EVO stents was successful in all patients. No technical complications were observed. One in-stent thrombotic event occurred during the procedure. MRA for one-year follow-up was performed in nine patients. One patient died (Hunt and Hess Grade IV). LVIS EVO stents may be a beneficial treatment option for BBAs, as they provide high occlusion rates. However, the long-term efficacy remains uncertain.

Microsurgical treatment of blood blister-like aneurysms: efficacy of clip-on-wrapping with autologous dura mater.

OBJECTIVE: To present a consecutive 20-year series of blood blister-like aneurysms (BBAs) to show that clip-on-wrapping with a Y-shaped autologous dura mater enables treatment of BBAs with a low complication rate and a satisfactory curative result. METHODS: A retrospective review was performed from patients with BBAs of the internal carotid artery (ICA) at the Affiliated Hospital of Qingdao University from 1999 to 2019. Diagnosis and treatment options were analyzed. Outcome was assessed using the modified Rankin scale (mRS). RESULTS: A total of 30 patients with BBAs of the ICA were included. Among these patients, 20 patients underwent microsurgical treatment (15 patients were treated by clip-on-wrapping with a Y-shaped autologous dura mater), the other 10 patients underwent endovascular treatment. All patients presented with subarachnoid hemorrhage (SAH). Four angiograms were initially negative. For all patients, intraoperative rupture occurred in five cases, but no postoperative aneurysm rupture occurred in this series. Three cases with clinical or radiologic cerebral infarctions were observed. The outcome was favorable in 26 patients. CONCLUSIONS: Clip-reinforced wrapping technique using a Y-shaped autologous dura mater may be an effective method for treating BBAs.

Clip-reinforced wrapping using the Y-shaped temporalis fascia technique for intracranial aneurysms.

Objectives: This study aims to identify the effectiveness of the clip-reinforced wrapping using the Y-shaped temporalis fascia (CRYST) technique for treating intracranial aneurysms (IAs). Methods: We retrospectively reviewed five patients with ruptured IAs treated using the CRYST technique from July 2016 to May 2021. Three patients had blood blister-like aneurysms (BBAs) (one with intraoperative rupture), and two had anterior communicating artery (AcoA) aneurysms (one with intraoperative rupture). All patients had intraoperative indocyanine green angiography, and digital subtraction angiography (DSA) was reviewed 10-14 days after surgery. At 1 year postoperatively, three patients (two BBAs and one AcoA aneurysm) underwent DSA and two patients (one BBA and one AcoA aneurysm) underwent computed tomographic angiography (CTA). Results: Two aneurysms ruptured intraoperatively during the clipping, and no severe complications occurred. No patients had neurological deficits after surgery, and they had good outcomes. Four DSAs showed no aneurysms and no significant stenosis of the parent artery 10-14 days after surgery. One patient had mild stenosis of the parent artery on DSA 10 days after surgery; the stenosis improved on DSA 1 year after surgery. No other aneurysms recurred, and parent arteries were clear on CTA or DSA 1 year after surgery. Conclusions: Combining our accumulated experience in the work and literature, we described the CRYST technique to treat intractable IAs with specific morphologies and irregular wall structures in our patients. All outcomes and follow-up results were favorable.

A propensity score-matched study on the short-term outcome of ruptured blood blister-like aneurysm treated by microsurgery or endovascular surgery: a single-center study of 155 cases.

Treating blood blister-like aneurysms (BBA) is a major neurosurgical challenge. Whether endovascular repair serves as a better strategy than microsurgery remains controversial. We aim to perform a propensity score-matched (PSM) retrospective study to analyze the short-term outcome in BBA patients who received microsurgery and endovascular treatment. One hundred fifty-five eligible patients with internal carotid artery BBA were retrospectively collected with demographic and angiographic baseline in a single center. Three-month outcome and adverse events were set as outcome endpoints. PSM was used to match the microsurgery and endovascular group. Matching effect was evaluated by distribution variation analysis and love plot. The outcome of neurosurgery and endovascular treatment was then compared before and after PSM. Better WFNS levels (p = .017) and modified Fisher grade (p = .027) were noted in endovascular group before matching. Other baseline including angiographic features were comparable between two groups. Before matching, the 3-month outcome of endovascular repair surgery was more favorable than microsurgery (p < .0001). The occurrence of adverse events was also higher in the microsurgery group (p = .0079). In PSM-adjusted groups, the superior outcome effect of endovascular treatment still existed but with a reduced significance (p = .004). Similar trend was also observed in the adverse event rate (p = .038). Fatality rate was comparable between two adjusted groups regardless of PSM adjustment. Endovascular surgery of BBAs exhibits overall more favorable short-term outcome regardless of PSM matching. Microsurgery does not cause a higher fatality rate, hence it could be considered a salvage plan for those high-grade BBA patients.

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.

Application of the Willis Covered Stent in the Treatment of Blood Blister-Like Aneurysms: A Single-Center Experience.

Objective: To evaluate the effectiveness of the Willis covered stent (WCS) in the treatment of ruptured blood blister-like aneurysms (BBAs) of the internal carotid artery (ICA). Method: The clinical data of 16 patients consecutively treated with WCSs from December 2015 to January 2019 were retrospectively analyzed. Clinical data and angiographic findings were analyzed by two experienced neuroradiologists and neurosurgeons, including age, sex, Hunt and Hess (H&H) grade at admission, modified Rankin scale (mRS) score, aneurysm size, and location, the diameter of the patent artery in proximal and distal ends, stent size, rate of aneurysm occlusion, procedure-related complications, and follow-up. Results: All the 16 patients (five males, 11 females) with ICA BBAs underwent WCS deployment successfully. The median age was 49 years (range, 29-72). All patients had complete aneurysm occlusion on immediate postoperative angiography. Anterior choroidal artery (AChA) was occluded in one patient accidentally while no obvious neurological dysfunction was observed. However, this patient underwent subarachnoid hemorrhage 1 day after the treatment; endoleak and aneurysm recurred, and the patient died 10 days later. Therefore, the effective rate of WCS treatment was 93.8% (15/16), and procedure-related complications rate was 6.3% (1/16). Moreover, one patient was urgently treated because of accidental aneurysm rupture after anesthesia, and external ventricular drainage was then performed postoperatively. Another patient developed coma and hemiplegia 3 days after treatment, with emergency angiography showing in-stent thrombosis and ICA occlusion which was recanalized with arterial rt-PA thrombolysis; the patient recovered completely. The clinical follow-up period was 3-30 months in 14 patients. The mRS scores were 0 in 12 patients (85.7%) and 4 in 1 case (7.1%), while 1 patient (7.1%) died 6 months postoperatively for unknown reasons. Angiographic follow-up was performed in 13 patients, and no recurrence was observed. However, ICA occlusion without neurological deficit was observed in one patient. Conclusion: Based on careful preoperative evaluation, appropriate WCS size selection, and precise surgical operation, WCSs may provide an alternative and effective solution for blood BBAs via aneurysm isolation and ICA reconstruction immediately; However, further follow-up studies with larger samples are required.

Case Series of Endovascular Therapy for Blood Blister-Like Aneurysm in Acute Phase.

Objective: Blood blister-like aneurysms (BBAs) of the internal carotid artery are highly challenging to treat due to their variable morphology and tendency for rupture and regrowth. Here, we report a single-institution experience of endovascular therapy (EVT) for BBA treatment. Methods: We retrospectively reviewed patients with ruptured BBA from 2006 to 2019. All patients in whom BBA was treated with EVT were included. Patients' aneurysmal characteristics, progression status, aneurysm occlusion on follow-up angiography, and modified Rankin Scale (mRS) score were recorded. Results: A total of 11 patients (5 women and 6 men) with the mean age of 46 ± 10 years were included in this study. As initial treatment, 9 patients were treated with stent-assisted coiling (SAC). Immediate angiographic results showed that 2 cases were body filling, 4 were neck remnant, and 3 were complete obliteration. Perioperative ischemic complications were not observed. On postoperative day 1, 2 patients suffered from rerupture, and their prognoses were poor. Retreatments were performed in 5 patients. Parent artery occlusion (PAO) was performed in 6 patients including 2 initial treatments and 4 retreatments. Symptomatic infarction developed in 2 patients. In 3 patients, bypass in combination with PAO was performed. Clinical data revealed discharge mRS scores of 0-2 and 3-6 in 4 and 7 patients, respectively. Conclusion: SAC is effective for the management of BBA. Careful follow-up and response are necessary after treatment with SAC.

Reduced M2 macrophages and adventitia collagen dampen the structural integrity of blood blister-like aneurysms and induce preoperative rerupture.

OBJECTIVE: Blood blister-like aneurysms (BBAs) are extremely rare aneurysms. They are predisposed to preoperative rerupture with a high case-fatality rate. Here, we attempt to interrogate the distinct clinicopathology and the histological basis underlying its clinical rerupture. METHODS: Three middle meningeal arteries, 11 BBA (5 reruptured, 6 non-rerupture) and 19 saccular aneurysm samples were obtained for histopathological investigation. Three reruptured BBAs, 3 non-reruptured BBAs and 6 saccular (3 ruptured, 3 unruptured) aneurysms were obtained for quantitative flow cytometry analysis. RESULTS: Compared with true saccular aneurysms, the BBA aneurysm wall lacks arterial stroma cells including CD31+ endothelial cells and α-SMA + smooth muscle cells. Only fibroblasts and adventitial collagen were observed in the BBA aneurysm wall. Meanwhile, BBAs were enriched with infiltrated inflammatory cells, especially polarized macrophages. Based on the rerupture status, those reruptured BBAs showed drastically reduced fibroblasts and adventitia collagen. Moreover, M2-polarized macrophages were observed dominant in BBAs and exhibit repairing cellular functions based on their interplays with arterial fibroblasts. Reduced M2 macrophages and arterial tissue repairing modulation may be responsible for the decreasing collagen synthesis and fibrosis repairment, which potentially dampens the aneurysm integrity and induces BBA aneurysm reruputre. CONCLUSIONS: BBAs poses histopathological features of occult pseudoaneurysms or dissecting aneurysms. Reduced M2 macrophages and adventitia collagen may dampen the structural integrity of BBAs and induce preoperative rerupture.

Willis covered stent treatment for blood blister-like aneurysm: A meta-analysis of efficacy and safety.

Background: Blood blister-like aneurysm (BBA) is a rare and special type of intracranial aneurysm with extremely high rates of rupture, morbidity, mortality, and recurrence. Willis Covered Stent (WCS) is a new device that is specifically designed for the treatment of intracranial complex aneurysms. However, the efficacy and safety of WCS treatment for BBA remain controversial. Thus, a high level of evidence is required to prove the efficacy and safety of WCS treatment. Methods: A systematic literature review was performed using a comprehensive literary search in Medline, Embase, and Web of Science databases to identify studies related to WCS treatment for BBA. A meta-analysis was then conducted to incorporate the efficacy and safety outcomes, including intraoperative situation, post-operative situation, and follow-up data. Results: Eight non-comparative studies containing 104 patients with 106 BBAs met the inclusion criteria. In the intraoperative situation, the technical success rate was 99.5% [95% confidence interval (CI), 0.958, 1.000], the complete occlusion rate was 98.2% (95% CI, 0.925, 1.000), and the side branch occlusion rate was 4.1% (95% CI, 0.001, 0.114). Vasospasm and dissection occurred in 9.2% (95% CI, 0.000, 0.261) and 0.1% (95% CI, 0.000, 0.032) of the patients, respectively. In the post-operative situation, the rebleed and mortality rates were 2.2% (95% CI, 0.000, 0.074) and 1.5% (95% CI, 0.000, 0.062), respectively. In the follow-up data, recurrence and parent artery stenosis occurred in 0.3% (95% CI, 0.000, 0.042) and 9.1% (95% CI, 0.032, 0.168) of the patients, respectively. Ultimately, 95.7% (95% CI, 0.889, 0.997) of the patients had a good outcome. Conclusions: Willis Covered Stent could be effectively and safely applied for BBA treatment. The results provide a reference for clinical trials in the future. Well-designed prospective cohort studies must be conducted for verification.

Application of the Willis covered stent in the treatment of internal carotid artery blood blister-like aneurysms.

The optimal treatment for blood blister-like aneurysm (BBA) has not yet been determined, and BBA has a high recurrence rate after stent-assisted embolization. The purpose of the present study was to evaluate the safety and feasibility of patients with BBA rupture in the acute phase or patients with BBA who have recurrence after stent-assisted coil embolization. Eight patients (8 women, mean age 50.3 ± 3.7 years) who presented with ruptured BBA or recurrence BBA that had been treated by stent-assisted embolization (5 patients after primary treatment of stent-assisted embolization) were retrospectively reviewed. Clinical follow-up was performed at 1 year after endovascular treatment. All patients were successfully treated with the WCS, and immediate postoperative angiography showed that the aneurysms were completely isolated. The ophthalmic artery was covered by WCS in one patient; however, this patient did not show any clinical visual field or vision symptoms. Procedure-related complications such as aneurysm rupture, vasospasm, acute thrombosis, or thromboembolism did not occur in any case. All patients were followed up for 1 year after endovascular treatment, and they were in good condition without recurrence. One patient developed delayed bleeding at the right temporal lobe. All patients had good clinical prognosis (modified Rankin Scale score ≤ 2). WCS implantation may be a safe and feasible strategy for patients with BBA rupture in the acute phase and patients with BBA who have recurrence after stent-assisted coil embolization and is a promising option worth exploring.

Endovascular treatment of blood blister-like aneurysms of internal carotid artery: Stent-assisted coiling and pipeline flow diversion.

OBJECTIVE: To report the stent-assisted coil embolization and flow diversion treatments of blood-blister-like aneurysms based on the theory of acute dissection of the internal carotid artery. PATIENTS AND METHODS: From July 2016 through July 2020, 27 patients presenting with subarachnoid hemorrhage (SAH) due to rupture of internal carotid artery blood blister-like aneurysms were subjected to endovascular treatment with stent-assisted coiling or Pipeline flow diversion. Clinical outcomes were evaluated using modified Rankin Scale score (mRS). RESULTS: A proximal stenosis caused by angiopathology adjacent to aneurysms were found on internal carotid artery angiograms in all 27 cases. The angiopathology combining with the aneurysms implement that acute dissection of the supraclinoid segment of the internal carotid artery indicated the pathogenesis of blood blister-like aneurysm formation. All aneurysms were treated successfully with alleviation of the adjacent angiopathology after stenting on angiograms. During 1-12 months, mean 3.5 months, complete aneurysm obliteration without adjacent stenosis were found in 25(92.6%) patients. Two (7.4%) cases of recanalization were retreated with complete obliteration at 1 week and 3 months after initial treatment. Clinical mRS 0 and 1 outcomes were observed in 23(85.2%) patients, mRS 2 in 3(11.1%) patients and mRS 6 in 1(3.7%) not related to aneurysm treatment during follow-up. CONCLUSIONS: Acute focal dissection of supraclinoid segment of internal carotid artery underlies the development of blood blister-like aneurysm. Stent-assisted coiling and flow diversion treatments constitute appropriate treatment based on the arterial dissection pathology.

Lesion Trapping with High-Flow Bypass for Ruptured Internal Carotid Artery Blood Blister-Like Aneurysm Has Little Impact on the Anterior Choroidal Artery Flow: Case Series and Literature Review.

OBJECTIVE: To examine the relationship between trap location and cerebral infarction in the anterior choroidal artery (AChA) region and associated risks in ruptured internal carotid artery blood blister-like aneurysm (BLA) treatment with high-flow bypass and lesion trapping. METHODS: We included 26 patients diagnosed with BLAs and treated with high-flow bypass and trapping. We examined clinical characteristics including age, aneurysm trap location, final prognosis, cerebral infarction on postoperative magnetic resonance imaging, and modified Rankin Scale score at discharge. We also searched the literature for similar studies. RESULTS: The modified Rankin Scale score at discharge was 0-2 in 20 patients, 3-5 in 2 patients, and 6 in 2 patients. In 19/26 patients (73.1%), the trapped segment was between the posterior communicating (PcomA) and the ophthalmic arteries. In 2 patients (7.7%), the trapped segment included the PcomA and the AChA; in 4 patients (15.4%), the trapped segment was within the PcomA. In these patients, the PcomA was occluded, and blood from the high-flow bypass flowed out to the AChA alone. No patient showed cerebral infarction. Our systematic review identified 70 patients. Of all 96 patients, 12 had AChA cerebral infarction; however, the infarction affected the prognosis of only 2 patients. CONCLUSIONS: When treating BLAs with high-flow bypass and lesion trapping, the frequency of AChA cerebral infarction is low even when the PcomA is occluded, leaving the AChA as the only outflow vessel during high-flow bypass. However, PcomA occlusion may be associated with risks when treating patients with advanced arteriosclerosis near C1-2.

The formation mechanism of acute dissection of blood blister-like aneurysm and its implication of endovascular treatment.

BACKGROUND: Acute mural dissection of the anterior wall of the internal carotid artery which may contribute to the development of blood blister-like aneurysms (BBLAs) was postulated, and stenting or flow diversion treatment across the soi-disant aneurysm was reported in this study. METHODS: From December 2016 to December 2018, 8 patients presenting with subarachnoid hemorrhage (SAH) due to BBLA were subjected to endovascular treatment with stent-assisted coiling. Clinical outcomes were evaluated using a clinical outcome score scale. RESULTS: Based on angiograms, pathologic change involving the supraclinoid segments of the internal carotid artery (ICA) adjacent to BBLA was found in all patients. This pathologic change meant a focal dissection of the supraclinoid segment of the ICA which constituted the pathogenesis of BBLAs. Closed-cell, open-cell, and braided stents were used in 1, 1, and 6 patients, respectively. Complete obliteration was achieved following endovascular treatment among all 8 patients harboring BBLA. One re-bleeding successive to a closed-cell stent across the aneurysmal neck was observed. Follow-up angiograms revealed stable complete exclusion of all BBLAs from the parent vessel at 3 to 8 months. All patients had a favorable clinical outcome score of 0-1. CONCLUSIONS: Acute dissection of a focal point of the intracranial vessels underlies the development of BBLAs. Open-cell and braided-cell stent-assisted coiling may constitute appropriate treatment due to good apposition against the vascular walls. Adjunctive coils may facilitate immediate complete occlusion of BBLAs.

Usefulness of 3D High-resolution Vessel Wall MRI in Diffuse Nonaneurysmal SAH Patients.

PURPOSE: In 15-20% of patients with nontraumatic diffuse subarachnoid hemorrhage (SAH), the initial conventional angiography does not reveal a causative vascular abnormality, such as intracranial aneurysm. In this study, we evaluated clinical utility of 3D high-resolution vessel wall magnetic resonance imaging (HR-VWI) in patients with diffuse nonaneurysmal SAH. METHODS: A total of 17 patients with diffuse nonaneurysmal SAH were included in this retrospective study. We characterized demographics and HR-VWI findings and reviewed the clinical management and outcomes. RESULTS: Of the patients 14 (14/17; 82.4%,) showed abnormal findings on HR-VWI, including 5 with intracranial dissections (29.4%), 3 with blood blister-like aneurysm (17.6%), 1 with ruptured fusiform aneurysm (5.9%), and 5 with focal nodular wall enhancement without unclassified pathology (29.4%). Of these patients were treated with endovascular management. Most patients (16/17) had a favorable modified Rankin scale scores of 0-2 on discharge. CONCLUSION: The 3D HR-VWI revealed various hidden pathologies, such as intracranial arterial dissection, blood blister-like aneurysm, and fusiform aneurysm in patients with diffuse nonaneurysmal SAH. In addition, 3D HR-VWI had an impact on the management of SAH. The 3D HR-VWI can be a complementary diagnostic method for patients with diffuse nonaneurysmal SAH in a research or clinical setting.