Endovascular Therapy for Intracranial Giant Cell Arteritis : Systematic Review, Technical Considerations and the Effect of Intra-arterial Calcium Channel Blockers.

BACKGROUND: Giant cell arteritis (GCA) is a systemic vasculitis that may cause ischemic stroke. Rarely, GCA can present with aggressive intracranial stenoses, which are refractory to medical therapy. Endovascular treatment (EVT) is a possible rescue strategy to prevent ischemic complications in intracranial GCA but the safety and efficacy of EVT in this setting are not well-described. METHODS: A systematic literature review was performed to identify case reports and series with individual patient-level data describing EVT for intracranial GCA. The clinical course, therapeutic considerations, and technique of seven endovascular treatments in a single patient from the authors' experience are presented. RESULTS: The literature review identified 9 reports of 19 treatments, including percutaneous transluminal angioplasty (PTA) with or without stenting, in 14 patients (mean age 69.6 ± 6.3 years). Out of 12 patients 8 (66.7%) with sufficient data had > 1 pre-existing cardiovascular risk factor. All patients had infarction on MRI while on glucocorticoids and 7/14 (50%) progressed despite adjuvant immunosuppressive agents. Treatment was PTA alone in 15/19 (78.9%) cases and PTA + stent in 4/19 (21.1%). Repeat treatments were performed in 4/14 (28.6%) of patients (PTA-only). Non-flow limiting dissection was reported in 2/19 (10.5%) of treatments. The indications, technical details, and results of PTA are discussed in a single illustrative case. We report the novel use of intra-arterial calcium channel blocker infusion (verapamil) as adjuvant to PTA and as monotherapy, resulting in immediate improvement in cerebral blood flow. CONCLUSION: Endovascular treatment, including PTA with or without stenting or calcium channel blocker infusion, may be effective therapies in medically refractory GCA with intracranial stenosis.

Endovascular treatment strategy, technique, and outcomes for dural arteriovenous fistulas of the marginal sinus region.

BACKGROUND: Dural arteriovenous fistulas (AVF) of the foramen magnum region (FMR) are technically challenging lesions to treat. Transvenous (TV), transarterial (TA), and surgical approaches have been described, but the optimum treatment strategy is not defined. OBJECTIVE: To report treatment strategies and outcomes for FMR-AVF at a single, high-volume referral center. METHODS: A retrospective review from January 2010 to August 2020 identified patients with FMR-AVF at a single referral center. Angiographic features, treatment (observation, endovascular, surgical), and follow-up of angiographic and clinical results were recorded. The technical aspects of TV embolization are then presented in detail. RESULTS: 29 FMR-AVF were identified in 28 patients. Of these, 24/29 (82.8%) were treated and 5/29 (17.2%) were observed. Treatment was endovascular in 21/24 (87.5%), combined (endovascular+surgical) in 2/24 (8.3%), and surgical in 1/24 (4.2%). Endovascular treatments were 76.2% TV, 14.3% TA, and 9.5% combined TV/TA. Sufficient follow-up data were available for 20/28 (71.4%) with mean follow-up of 16.8 months. No AVF recurrence was seen for TA/TV, combined endovascular/surgical, or surgical groups, and there was one recurrence (7.1%) in the TV group. Symptomatic improvement was seen in all groups: TV (71.4% complete, 28.6% partial), TA (66.7% complete, 33.3% no follow-up), TV+TA (100% partial), endovascular/surgical (100% complete), and surgical (100% partial). Minor non-neurologic complications included 1/14 (7.1%) in the TV group and 1/3 (33.3%) in the TA/TV group. CONCLUSION: Endovascular treatment is safe and effective for most FMR-AVF. TV embolization has a high cure rate with few complications.

Robotics for neuroendovascular intervention: Background and primer.

The simultaneous growth of robotic-assisted surgery and telemedicine in recent years has only been accelerated by the recent coronavirus disease 2019 pandemic. Robotic assistance for neurovascular intervention has garnered significant interest due to opportunities for tele-stroke models of care for remote underserved areas. Lessons learned from medical robots in interventional cardiology and neurosurgery have contributed to incremental but vital advances in medical robotics despite important limitations. In this article, we discuss robot types and their clinical justification and ethics, as well as a general overview on available robots in thoracic/abdominal surgery, neurosurgery, and cardiac electrophysiology. We conclude with current clinical research in neuroendovascular intervention and a perspective on future directions.

Endovascular Biopsy of Vertebrobasilar Aneurysm in Patient With Polyarteritis Nodosa.

Background and Purpose: The management of unruptured intracranial aneurysms remains controversial. The decisions to treat are heavily informed by estimated risk of bleeding. However, these estimates are imprecise, and better methods for stratifying the risk or tailoring treatment strategy are badly needed. Here, we demonstrate an initial proof-of-principle concept for endovascular biopsy to identify the key molecular pathways and gene expression changes associated with aneurysm formation. We couple this technique with single cell RNA sequencing (scRNAseq) to develop a roadmap of the pathogenic changes of a dolichoectatic vertebrobasilar aneurysm in a patient with polyarteritis nodosa. Methods: Endovascular biopsy and fluorescence activated cell sorting was used to isolate the viable endothelial cells (ECs) using the established techniques. A single cell RNA sequencing (scRNAseq) was then performed on 24 aneurysmal ECs and 23 patient-matched non-aneurysmal ECs. An integrated panel of bioinformatic tools was applied to determine the differential gene expression, enriched signaling pathways, and cell subpopulations hypothesized to drive disease pathogenesis. Results: We identify a subset of 7 (29%) aneurysm-specific ECs with a distinct gene expression signature not found in the patient-matched control ECs. A gene set enrichment analysis identified these ECs to have increased the expression of genes regulating the leukocyte-endothelial cell adhesion, major histocompatibility complex (MHC) class I, T cell receptor recycling, tumor necrosis factor alpha (TNFα) response, and interferon gamma signaling. A histopathologic analysis of a different intracranial aneurysm that was later resected yielded a diagnosis of polyarteritis nodosa and positive staining for TNFα. Conclusions: We demonstrate feasibility of applying scRNAseq to the endovascular biopsy samples and identify a subpopulation of ECs associated with cerebral aneurysm in polyarteritis nodosa. Endovascular biopsy may be a safe method for deriving insight into the disease pathogenesis and tailoring the personalized treatment approaches to intracranial aneurysms.

Radial artery access for neuroendovascular procedures: safety review and complications.

Although enthusiasm for transradial access for neurointerventional procedures has grown, a unique set of considerations bear emphasis to preserve safety and minimize complications. In the first part of this review series, we reviewed anatomical considerations for safe and easy neuroendovascular procedures from a transradial approach. In this second part of the review series, we aim to (1) summarize evidence for safety of the transradial approach, and (2) explain complications and their management.

Radial artery access anatomy: considerations for neuroendovascular procedures.

Although enthusiasm for transradial access for neurointerventional procedures has grown, a unique set of considerations bear emphasis to preserve safety and minimize complications. In the first part of this review series, we will review important anatomical considerations for safe and easy neuroendovascular procedures from a transradial approach. These include normal and variant radial artery anatomy, the anatomic snuffbox, as well as axillary, brachial, and great vessel arterial anatomy that is imperative for the neuroendovascular surgeon to be intimately familiar prior to pursuing transradial access procedures. In the next part of the review series, we will focus on safety and complications specific to a transradial approach.

Intrasaccular flow disruption (WEB) of a large wide-necked basilar apex aneurysm using PulseRider-assistance.

Large, wide-necked basilar apex aneurysms are difficult to treat. Microsurgical clipping can result in neurologic morbidity and mortality. Endovascular treatment often leaves remnants that need retreatment and/or stent placement with dual antiplatelet therapy. The Woven EndoBridge (WEB) is an intrasaccular flow disruption device that can be used without dual antiplatelet therapy. However, the WEB cannot typically be used in large or giant aneurysms > 10 mm because the largest diameter device is the 11 × 9.6 mm single layer sphere (SLS). We present a case in which we use a PulseRider aneurysm neck reconstruction device in the basilar artery to assist in WEB deployment within a 22 mm basilar apex aneurysm with 14 mm neck, thereby permitting aspirin monotherapy postoperatively.

Combined Use of X-ray Angiography and Intraprocedural MRI Enables Tissue-based Decision Making Regarding Revascularization during Acute Ischemic Stroke Intervention.

Background For patients with acute ischemic stroke undergoing endovascular mechanical thrombectomy with x-ray angiography, the use of adjuncts to maintain vessel patency, such as stents or antiplatelet medications, can increase risk of periprocedural complications. Criteria for using these adjuncts are not well defined. Purpose To evaluate use of MRI to guide critical decision making by using a combined biplane x-ray neuroangiography 3.0-T MRI suite during acute ischemic stroke intervention. Materials and Methods This retrospective observational study evaluated consecutive patients undergoing endovascular intervention for acute ischemic stroke between July 2019 and May 2020 who underwent either angiography with MRI or angiography alone. Cerebral tissue viability was assessed by using MRI as the reference standard. For statistical analysis, Fisher exact test and Student t test were used to compare groups. Results Of 47 patients undergoing acute stroke intervention, 12 patients (median age, 69 years; interquartile range, 60-77 years; nine men) underwent x-ray angiography with MRI whereas the remaining 35 patients (median age, 80 years; interquartile range, 68-86 years; 22 men) underwent angiography alone. MRI results influenced clinical decision making in one of three ways: whether or not to perform initial or additional mechanical thrombectomy, whether or not to place an intracranial stent, and administration of antithrombotic or blood pressure medications. In this initial experience, decision making during endovascular acute stroke intervention in the combined angiography-MRI suite was better informed at MRI, such that therapy was guided in real time by the viability of the at-risk cerebral tissue. Conclusion Integrating intraprocedural 3.0-T MRI into acute ischemic stroke treatment was feasible and guided decisions of whether or not to continue thrombectomy, to place stents, or to administer antithrombotic medication or provide blood pressure medications. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Lev and Leslie-Mazwi in this issue.

Asymptomatic rotational vertebral artery compression in a child due to head positioning for cranial surgery: illustrative case.

BACKGROUND: The authors recently reported a series of children with vertebral artery (VA) compression during head turning who presented with recurrent posterior circulation stroke. Whether VA compression occurs during head positioning for cranial surgery is unknown. OBSERVATIONS: The authors report a case of a child with incidental rotational occlusion of the VA observed during surgical head positioning for treatment of an intracranial arteriovenous fistula. Intraoperative angiography showed dynamic V3 occlusion at the level of C2 with distal reconstitution via a muscular branch "jump" collateral, supplying reduced flow to the V4 segment. She had no clinical history or imaging suggesting acute or prior stroke. Sequential postoperative magnetic resonance imaging scans demonstrated signal abnormality of the left rectus capitus muscle, suggesting ischemic edema. LESSONS: This report demonstrates that rotational VA compression during neurosurgical head positioning can occur in children but may be asymptomatic due to the presence of muscular VA-VA "jump" collaterals and contralateral VA flow. Although unilateral VA compression may be tolerated by children with codominant VAs, diligence when rotating the head away from a dominant VA is prudent during patient positioning to avoid posterior circulation ischemia or thromboembolism.

Delayed-Onset Cranial Nerve Palsy After Transvenous Embolization of Indirect Carotid Cavernous Fistulas.

BACKGROUND: Carotid cavernous fistulas (CCF) often present with diplopia secondary to cranial nerve palsy (CNP). Immediate development of postoperative CNP has been described in the literature. This study described delayed-onset of CNP after complete and reconfirmed obliteration of the CCF and resolution of initial CNP. METHODS: A retrospective analysis was performed on patients with indirect CCF between 1987 and 2006 at 4 academic endovascular centers. Details of the endovascular procedures, embolic agents used, and complications were studied. Partial or complete obliteration was determined. Immediate and delayed cranial nerve palsies were independently assessed. RESULTS: A total of 267 patients with symptomatic indirect CCF underwent transvenous endovascular treatment. Four patients (1.5%) developed delayed abducens nerve (VI) palsy after complete resolution of presenting symptoms after embolization. Delayed presentation ranged between 3 and 13 months after complete resolution of initial double vision and cranial nerve palsies. Transvenous coil embolization through the inferior petrosal sinus was performed in all 4 affected patients. All had follow-up angiography confirming durable closure of their CCF. MRI did not show new mass lesions or abnormal soft tissue enhancement. In all 4 patients, their abducens nerve (VI) palsy remained. CONCLUSIONS: Delayed CNP can develop despite complete endovascular obliteration of the CCF. The cause of delayed CNP is not yet determined, but may represent fibrosis and ischemia. Long-term follow-up is needed even after complete neurological and radiological recovery is attained in the immediate perioperative period.

Cerebral arteriovenous fistulae.

Dural arteriovenous fistulae (dAVFs) are diverse, complex lesions that share the common feature of arteriovenous shunting without an intervening nidus. In this chapter, the ensuing discussion is organized by dAVF location, followed by further consideration of less common, distinct types of dAVFs-carotid cavernous fistulae, pial arteriovenous fistulae, and vein of Galen malformations. For each lesion type, epidemiology, clinical presentation, imaging findings, classification considerations, and treatment options are discussed.

"And do no harm": Complications in interventional neuroradiology.

Complications are an unfortunate reality in the field of interventional neuroradiology. While complications cannot be eliminated entirely, their occurrence and severity can be mitigated by the competency achieved through training, knowledge of cerebrovascular anatomy and pathology, and well-conceived and executed plans crafted in conjunction with a multidisciplinary team. Frequent communication among the team throughout the entire process of care is vital. In the ensuing chapter, an overview is provided of the most common complication types-nontarget embolization and hemorrhage-followed by practical considerations for their management. Finally, the chapter concludes with a brief consideration of the emotional management for the patient, their loved ones, and the involved practitioners.

Brain Arteriovenous Malformation Recurrence After Apparent Microsurgical Cure: Increased Risk in Children Who Present With Arteriovenous Malformation Rupture.

BACKGROUND AND PURPOSE: Do children have an increased risk for brain arteriovenous malformation (AVM) recurrence compared with adults and does this risk vary depending on initial presentation with AVM rupture? METHODS: We retrospectively studied 115 patients initially presenting with brain AVM under age 25 years who underwent complete surgical resection of the AVM as documented by digital subtraction angiography (DSA) and had delayed follow-up DSA to evaluate for AVM recurrence after apparent initial cure. RESULTS: The mean time from baseline DSA to follow-up DSA was 2.3 years, ranging from 0 to 15 years. Twelve patients (10.4% of the 115 patient cohort and 16.7% of 72 patients with hemorrhage at initial presentation) demonstrated AVM recurrence on follow-up DSA. All patients with recurrence initially presented with intracranial hemorrhage, and intracranial hemorrhage was a significant predictor of recurrence (log rank P=0.037). Among patients with initial hemorrhage, the 5-year recurrence rate was 17.8% (95% CI, 8.3%-35.7%). All recurrences occurred in patients who were children at the time of their initial presentation; the oldest was 15 years of age at the time of initial AVM surgery. The 5-year recurrence rate for children (0-18 years of age) with an initial presentation of hemorrhage was 21.4% (95% CI, 10.1%-41.9%). Using Cox regression, we found the risk of AVM recurrence decreased by 14% per each year increase in age at the time of initial surgical resection (hazard ratio=0.86 [95% CI, 0.75-0.99]; P=0.031). CONCLUSIONS: There is a high rate of recurrence of apparently cured brain AVMs in children who initially present with AVM rupture. Imaging follow-up is warranted to prevent re-rupture.

Single-center series of boys with recurrent strokes and rotational vertebral arteriopathy.

OBJECTIVE: To describe a pediatric stroke syndrome with chronic focal vertebral arteriopathy adjacent to cervical abnormalities. METHODS: At a single pediatric stroke center, we identified consecutive children with stroke and vertebral arteriopathy of the V3 segment with adjacent cervical bony or soft tissue abnormalities. We abstracted clinical presentation, treatment, and follow-up data from medical charts. RESULTS: From 2005 to 2019, 10 children (all boys, ages 6-16 years) presented with posterior circulation strokes and vertebral arteriopathy with adjacent cervical pathology. Two children had bony abnormalities: one had a congenital arcuate foramen and one had os odontoideum with cervical instability. In children without bony pathology, vertebral artery narrowing during contralateral head rotation was visualized by digital subtraction angiography. Eight boys had recurrent ischemic events despite anti-thrombotic treatment (including 5 with multiple recurrences) and were treated surgically to prevent additional stroke. Procedures included vertebral artery decompression (n = 6), endovascular stent and spinal fusion (n = 1), and vertebral artery endovascular occlusion (n = 1). In boys treated with decompression, cervical soft tissue abnormalities (ruptured atlantoaxial bursa, ruptured joint capsule, or connective tissue scarring) were directly visualized during open surgery. No other etiology for stroke or dissection was found in any of the cases. Two boys without recurrent stroke were treated with activity restriction and antithrombotics. At a median follow-up of 51 months (range 17-84), there have been no additional recurrences. CONCLUSIONS: Children with V3 segmental vertebral arteriopathy frequently have stroke recurrence despite antithrombotics. Cervical bone imaging and angiography with neck rotation can identify underlying pathology.

The effect of preoperative embolization and flow dynamics on resection of brain arteriovenous malformations.

OBJECTIVE: Preoperative embolization of brain arteriovenous malformations (AVMs) is performed to facilitate resection, although its impact on surgical performance has not been clearly defined. The authors tested for associations between embolization and surgical performance metrics. METHODS: The authors analyzed AVM cases resected by one neurosurgeon from 2006 to 2017. They tested whether cases with and without embolization differed from one another with respect to patient and AVM characteristics using t-tests for continuous variables and Fisher's exact tests for categorical variables. They used simple and multivariable regression models to test whether surgical outcomes (blood loss, resection time, surgical clip usage, and modified Rankin Scale [mRS] score) were associated with embolization. Additional regression analyses integrated the peak arterial afferent contrast normalized for the size of the region of interest (Cmax/ROI) into models as an additional predictor. RESULTS: The authors included 319 patients, of whom 151 (47%) had preoperative embolization. Embolized AVMs tended to be larger (38% with diameter > 3 cm vs 19%, p = 0.001), less likely to have hemorrhaged (48% vs 63%, p = 0.013), or be diffuse (19% vs 29%, p = 0.045). Embolized AVMs were more likely to have both superficial and deep venous drainage and less likely to have exclusively deep drainage (32% vs 17% and 12% vs 23%, respectively; p = 0.002). In multivariable analysis, embolization was not a significant predictor of blood loss or mRS score changes, but did predict longer operating times (+29 minutes, 95% CI 2-56 minutes; p = 0.034) and increased clip usage (OR 2.61, 95% CI 1.45-4.71; p = 0.001). Cmax/ROI was not a significant predictor, although cases with large Cmax/ROI tended to have longer procedure times (+25 minutes per doubling of Cmax/ROI, 95% CI 0-50 minutes; p = 0.051). CONCLUSIONS: In this series, preoperative embolization was associated with longer median resection times and had no association with intraoperative blood loss or mRS score changes.

Relationship of clinical presentation and angiographic findings in patients with indirect cavernous carotid fistulae.

INTRODUCTION: Indirect cavernous carotid fistulae (ICCFs) can present with insidious, non-specific symptoms and prove difficult to diagnose. This study evaluates associations among ICCF symptoms and angiographic findings. METHODS: A retrospective analysis was performed of prospectively maintained records at four medical centers to identify patients with ICCFs evaluated with angiography. Patient demographics, symptoms, and angiographic findings were tabulated. Univariate and multivariate analyses were conducted to identify associations among these variables. RESULTS: Records sufficient for review existed for 267 patients evaluated with angiography. Patients were most commonly women, in the sixth or seventh decade of life, and had symptoms for months before a definitive diagnosis. The most common symptoms included proptosis, diplopia, cranial nerve palsy, and chemosis. Cortical venous reflux was most common in patients with chemosis, orbital pain, or bruit. Intracranial hemorrhage was associated with cortical reflux and bilateral inferior petrosal sinus occlusion. Patients with loss of symptoms demonstrated higher rates of inferior petrosal sinus occlusion and a trend towards rupture. CONCLUSION: A high index of suspicion is needed to promptly diagnose patients with ICCFs. High risk features are more common in the setting of chemosis, orbital pain, bruit, or spontaneous loss of symptoms. Patients with such symptoms warrant expedited angiographic evaluation.

Long-Term Outcomes of Endovascular Treatment of Indirect Carotid Cavernous Fistulae: Superior Efficacy, Safety, and Durability of Transvenous Coiling Over Other Techniques.

BACKGROUND: Endovascular surgery is the first-line treatment for indirect cavernous carotid fistulae (CCFs). This study compares multiple treatment techniques. OBJECTIVE: To compare endovascular techniques for indirect CCF treatment. METHODS: Retrospective analysis was performed of prospectively maintained records at 4 centers, identifying patients undergoing indirect CCF embolization. Demographics, symptoms, and lesion characteristics were recorded. Medical records were reviewed for changes in symptoms, delayed complications, and angiographically proven recurrence. Univariate and multivariate analyses were performed to identify impacts of the above characteristics on outcomes. RESULTS: Sufficient records were available for 267 patients treated between January 1987 and December 2016. Obliteration was achieved in 86.5% patients, occurring in 86.9% of exclusively transvenous treatments and 79.5% of other treatments. Obliteration rates were highest following transvenous embolization using coils compared to all other materials (likelihood ratio [LR] 5.0, P = .024). Complications were less common with coil embolization compared to other materials (LR 0.070, P < .001). Embolization with liquid embolics resulted in higher complication rates (LR 10.2, P = .002), although risk was reduced when used in conjunction with coils. Angiographically confirmed recurrence was more common following embolization with polyvinyl alcohol (LR 9.9, P = .004) and when multiple embolic agents were used (LR 6.6, P = .018). Delayed development of symptoms following embolization was less common following embolization with coils (LR 0.20, P = .030) and more common following embolization with liquids (LR 6.5, P = .014). CONCLUSION: To treat indirect CCFs, transvenous coil embolization is the safest and most effective technique. Liquid embolics are less effective and have more complications and should be carefully considered only in extenuating circumstances.

Improved procedural safety following protocol changes for selective ophthalmic arterial infusion of chemotherapy for treatment of ocular retinoblastoma.

Purpose The aim was to evaluate the impact of protocol changes in selective ophthalmic arterial infusion (SOAI) for treatment of retinoblastoma (Rb). Methods A retrospective review was completed of 35 patients with Rb who were treated with SOAI between March 2010 and January 2017. Treatment details were tabulated for each SOAI session. SOAI protocol was changed in June 2015, and differences before and after this change were evaluated using two-tail chi-square tests and independent sample t-tests to note any differences in technical complications, need for enucleation, and other outcome variables Results 125 SOAI sessions occurred. No technical complications occurred during the study. Two complications (1.6%) occurred in the postoperative setting. Both complications occurred prior to the change in protocol. Comparing the complication rates between the two protocols showed no significant difference (2.2% versus 0.0%; p = 0.505); 29 of 43 (67.4%) eyes had their vision preserved overall. Conclusions SOAI is an effective treatment for Rb. The refined protocol described herein was associated with fewer complications.

Estimation of intra-arterial chemotherapy distribution to the retina in pediatric retinoblastoma patients using quantitative digital subtraction angiography.

Background and purpose The purpose of this article is to estimate the distribution of superselective intra-arterial chemotherapy (IAC) delivery to ocular target tissue using quantitative digital subtraction angiography (qDSA). Materials and methods From March 2010 to January 2016, 50 ophthalmic artery contrast DSAs obtained immediately prior to IAC infusions in 22 patients were analyzed. This study was conducted under a retrospective review IRB (no. 10-01862). Parametric color-coded DSAs (iFlow, Siemens Medical) were post-processed (MATLAB, The Mathworks Inc.) using two methods: two box regions of interest (pre-retina and globe) and four custom regions of interest (ROIs-ophthalmic artery, choroid, supraclinoid internal carotid artery (ICA), cavernous ICA). Mean interobserver reliability of custom ROI selection is presented as a 95% confidence interval of interclass correlation, and fractional chemotherapy delivery to selected ROIs as means ± standard deviation in this study. Results The estimated fraction of chemotherapy delivered to the globe with the first method was 79.5%. Percentage regional delivery using the second method was as follows: ophthalmic artery, 85.8%; choroid, 60.5%; supraclinoid ICA, 14.2%. The cavernous ICA ROI (encompassing distal catheter and potential reflux) gave a signal equivalent to 9.3% of total delivery. Conclusion Parametric color-coded qDSA can estimate the fraction of IAC delivered to the retina and other orbital structures in ocular retinoblastoma patients. This information can inform delivery location and dosing strategies on a patient-specific basis.

Endovascular Biopsy: In Vivo Cerebral Aneurysm Endothelial Cell Sampling and Gene Expression Analysis.

There is limited data describing endothelial cell (EC) gene expression between aneurysms and arteries partly because of risks associated with surgical tissue collection. Endovascular biopsy (EB) is a lower risk alternative to conventional surgical methods, though no such efforts have been attempted for aneurysms. We sought (1) to establish the feasibility of EB to isolate viable ECs by fluorescence-activated cell sorting (FACS), (2) to characterize the differences in gene expression by anatomic location and rupture status using single-cell qPCR, and (3) to demonstrate the utility of unsupervised clustering algorithms to identify cell subpopulations. EB was performed in 10 patients (5 ruptured, 5 non-ruptured). FACS was used to isolate the ECs and single-cell qPCR was used to quantify the expression of 48 genes. Linear mixed models and exploratory multilevel component analysis (MCA) and self-organizing maps (SOMs) were performed to identify possible subpopulations of cells. ECs were collected from all aneurysms and there were no adverse events. A total of 437 ECs was collected, 94 (22%) of which were aneurysmal cells and 319 (73%) demonstrated EC-specific gene expression. Ruptured aneurysm cells, relative controls, yielded a median p value of 0.40 with five genes (10%) with p values < 0.05. The five genes (TIE1, ENG, VEGFA, MMP2, and VWF) demonstrated uniformly reduced expression relative the remaining ECs. MCA and SOM analyses identified a population of outlying cells characterized by cell marker gene expression profiles different from endothelial cells. After removal of these cells, no cell clustering based on genetic co-expressivity was found to differentiate aneurysm cells from control cells. Endovascular sampling is a reliable method for cell collection for brain aneurysm gene analysis and may serve as a technique to further vascular molecular research. There is utility in combining mixed and clustering methods, despite no specific subpopulation identified in this trial.