Gene expression profiles of ischemic stroke clots retrieved by mechanical thrombectomy are associated with disease etiology.

BACKGROUND: Determining stroke etiology is crucial for secondary prevention, but intensive workups fail to classify ~30% of strokes that are cryptogenic. OBJECTIVE: To examine the hypothesis that the transcriptomic profiles of clots retrieved during mechanical thrombectomy are unique to strokes of different subtypes. METHODS: We isolated RNA from the clots of 73 patients undergoing mechanical thrombectomy. Samples of sufficient quality were subjected to 100-cycle, paired-end RNAseq, and transcriptomes with less than 10 million unique reads were excluded from analysis. Significant differentially expressed genes (DEGs) between subtypes (defined by the Trial of Org 10 172 in Acute Stroke Treatment) were identified by expression analysis in edgeR. Gene ontology enrichment analysis was used to study the biologic differences between stroke etiologies. RESULTS: In all, 38 clot transcriptomes were analyzed; 6 from large artery atherosclerosis (LAA), 21 from cardioembolism (CE), 5 from strokes of other determined origin, and 6 from cryptogenic strokes. Among all comparisons, there were 816 unique DEGs, 174 of which were shared by at least two comparisons, and 20 of which were shared by all three. Gene ontology analysis showed that CE clots reflected high levels of inflammation, LAA clots had greater oxidoreduction and T-cell processes, and clots of other determined origin were enriched for aberrant platelet and hemoglobin-related processes. Principal component analysis indicated separation between these subtypes and showed cryptogenic samples clustered among several different groups. CONCLUSIONS: Expression profiles of stroke clots were identified between stroke etiologies and reflected different biologic responses. Cryptogenic thrombi may be related to multiple etiologies.

Chromatin architecture around stroke haplotypes provides evidence that genetic risk is conferred through vascular cells.

Introduction: Genome-wide association studies (GWAS) have identified numerous stroke-associated SNPs. To understand how SNPs affect gene expression related to increased stroke risk, we studied epigenetic landscapes surrounding 26 common, validated stroke-associated loci. Methods: We mapped the SNPs to linkage disequilibrium (LD) blocks and examined H3K27ac, H3K4me1, H3K9ac, and H3K4me3 histone marks and transcription-factor binding-sites in pathologically relevant cell types (hematopoietic and vascular cells). Hi-C data were used to identify topologically associated domains (TADs) encompassing the LD blocks and overlapping genes. Results: Fibroblasts, smooth muscle, and endothelial cells showed significant enrichment for enhancer-associated marks within stroke-associated LD blocks. Genes within encompassing TADs reflected vessel homeostasis, cellular turnover, and enzymatic activity. Conclusions: Stroke-associated genetic variants confer risk predominantly through vascular cells rather than hematopoietic cell types.

Previous studies have found several variations in the DNA sequence (known as single nucleotide polymorphisms) linked to higher stroke risk. But the mechanisms behind how they increase risk is unknown. One hypothesis is that they affect non-coding DNA elements (i.e., epigenetics), which in turn drive abnormal changes in gene expression leading to increased stroke risk. To investigate this potential mechanism, we mined publicly available, cell-type specific databases. We searched for overlap between the regions with polymorphisms and regions where DNA transcription machinery bind (i.e., enhancers, transcription factor binding sites). We found that fibroblasts and smooth muscle cells (cells in vessel walls) had more of these DNA elements in regions associated with stroke risk. Bioinformatics analyses of genes that could be affected by changes in these elements were linked to stroke-related mechanisms.

The impact of brain atrophy on the outcomes of mechanical thrombectomy.

OBJECTIVE: Pre-existing brain atrophy may affect the outcomes of patients treated with mechanical thrombectomy (MT) for large-vessel-occlusion because it is an indicator of low brain reserve. We performed a systematic literature review to assess the impact of brain atrophy on MT-related clinical outcomes. METHODS: We conducted a systematic search of PubMed, MEDLINE, EMBASE, and Cochrane Library databases from inception to March 2021 using keywords with Boolean operators("brain atrophy"; "atrophy"; "white matter"; and "thrombectomy"). Articles published in English that evaluated the impact of pre-existing brain atrophy on outcomes of MT-treated acute ischemic stroke were eligible for inclusion. RESULTS: Four articles were included. Brain atrophy index was a predictor of mortality (odds ratio [OR]:1.81-1.87, 95% confidence interval [CI]:1.16-2.93) after adjustments for age and white matter lesions. Global cortical atrophy scale was an independent predictor of futile recanalization (OR 1.15, 95% CI 1.08-1.22) in multivariate-adjusted logistic regression. Automated measurement of CSF identified increasing volumes associated with reduced 3-month functional independence and higher modified Rankin scale scores. STandards for ReportIng Vascular changes on Neuroimaging criteria for brain atrophy were associated with unfavorable outcome in ordinal-shift analysis (OR 2.72, 95% CI 1.25-5.91). CONCLUSIONS: The few studies available highlight heterogeneity of neuroimaging methodologies for assessing brain atrophy and difficulty addressing the multiple confounders involved in clinical outcomes. More consistent, accurate investigation is needed before proposing brain atrophy as a possible parameter to improve patient selection for MT. ADVANCES IN KNOWLEDGE: Brain atrophy is associated with many of the clinical confounders frequently present in patients with acute ischemic stroke. Heterogeneity in classification methodologies for brain atrophy and complexity analyzing multiple clinical confounders make it difficult to assess the true impact of this radiological finding on MT-related outcomes.

Mapping access to endovascular stroke care in the USA and implications for transport models.

BACKGROUND: The purpose of this cross-sectional study was to determine the percentage of the US population with 60 min ground or air access to accredited or state-designated endovascular-capable stroke centers (ECCs) and non-endovascular capable stroke centers (NECCs) and the percentage of NECCs with an ECC within a 30 min drive. METHODS: Stroke centers were identified and classified broadly as ECCs or NECCs. Geographic mapping of stroke centers was performed. The population was divided into census blocks, and their centroids were calculated. Fastest air and ground travel times from centroid to nearest ECC and NECC were estimated. RESULTS: Overall, 49.6% of US residents had 60 min ground access to ECCs. Approximately 37.7% (113 million) lack 60 min ground or air access to ECCs. Approximately 84.4% have 60 min access to NECCs. Ground-only access was available to 77.9%. Approximately 738 NECCs (45.4%) had an ECC within a 30 min drive. CONCLUSION: Nearly one-third of the US population lacks 60 min access to endovascular stroke care, but this is highly variable. Transport models and planning of additional centers should be tailored to each state depending on location and proximity of existing facilities.

Use of Walrus balloon-guide catheter through sheathless radial approach for mechanical thrombectomy of right middle cerebral artery occlusion.

The literature demonstrates a favorable first pass effect with balloon-guide catheter (BGC) for mechanical thrombectomy. An 8F BGC is routinely used with femoral access. We present the first video report of 8F BGC advanced through the radial artery using a sheathless technique (video 1). An approximately 70-year-old patient presented with left-sided hemiplegia, neglect, and dysarthria. A CT angiogram demonstrated right M1 occlusion, and the patient underwent urgent mechanical thrombectomy. Radial approach was preferred owing to patient history of anticoagulation. A 6F Sim Select intermediate catheter was used to minimize the step off as the 8F BGC was advanced into the radial artery over an 035 exchange-length Advantage Glidewire. A skin nick over the Glidewire Advantage facilitated the introduction of the 8F BGC into the radial artery. Standard mechanical thrombectomy using a combination of stent retriever and aspiration catheter (Solumbra technique) was performed, and thrombolysis in cerebral infarction 3 recanalization was achieved after a single pass. The National Institutes of Health Scale score improved from 12 to 4, with mild left facial droop, dysarthria, and decreased speech fluency. The patient was discharged from the hospital on postoperative day 2. Ultrasound should be used for immediate assessment of radial artery size and conversion to femoral access without delay if the radial artery is less than 2.5 mm. neurintsurg;14/5/neurintsurg-2021-017985/V1F1V1Video 1.

Treatment of ruptured intracranial aneurysms with the Woven EndoBridge device: a systematic review.

The Woven EndoBridge (WEB) device is a barrel-shaped nitinol mesh deployed within the aneurysmal sac. The absence of metallic mesh in the aneurysm's parent vessel lumen obviates the need for potent antiplatelet therapy, making this device appealing for acutely ruptured aneurysms not amenable to clipping or coiling. To assess the literature regarding WEB treatment of these aneurysms, we performed a comprehensive systematic search of PubMed, MEDLINE, and EMBASE databases following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Keywords were combined with Boolean operators to increase search sensitivity and specificity ('woven endobridge device' AND 'ruptured'). Nine studies comprising 377 acutely ruptured aneurysms were included. Overall, 82.7% were wide-necked, 85.9% were located in the anterior circulation, and 26.9% of patients presented with poor subarachnoid hemorrhage grade. Intraprocedure and postprocedure complications occurred in 8.4% (95% CI 3.6% to 13.3%) and 1% (95% CI 0% to 2%), respectively. The post-treatment rebleeding rate was 0%. Rates of adequate occlusion (complete occlusion to neck remnant) and retreatment at last follow-up were 84.8% (95% CI 73% to 96.6%) and 4.5% (95% CI 2.2% to 6.8%), respectively. The favorable outcome rate (modified Rankin Scale score 0-2) was 62.2% (95% CI 53% to 71.4%); mortality was 13.6% (95% CI 9.7% to 17.6%). WEB treatment of acutely ruptured aneurysms results in high adequate occlusion rates, low perioperative complication rates, no rebleeding, and low recurrence requiring retreatment. This device is promising for acutely ruptured aneurysms not amenable to clipping or coiling, considering the lower need for antiplatelet regimens during the procedure or follow-up.

Use of N-butyl 2-cyanoacrylate (nBCA) for preoperative tumor embolization.

N-butyl 2-cyanoacrylate (nBCA) is a fast-acting liquid adhesive that polymerizes when it comes in contact with blood anions. We present the principles of nBCA preparation and delivery for tumor embolization of a right convexity meningioma in a patient who presented with a 6-month history of word-finding difficulty and memory loss video 1 Angiography of the middle meningeal artery showed a hairpin turn that was not negotiable with a number of different microwires, including the Synchro-2, Chikai 014 and Balt hybrid 008 wire. Due to the tortuous hairpin turn, the microcatheter position was distal to the tumor blush for the convexity meningioma. Given the distal microcatheter position, we opted for nBCA as the liquid embolic of choice for tumor embolization. The time of polymerization for nBCA may be delayed using glacial acetic acid, which makes nBCA ideal when the microcatheter is in a distal position relative to the target location for embolization. The patient underwent successful embolization using nBCA and was taken for a right frontal craniotomy for resection of the meningioma the next day. The intraoperative blood loss was 100 mL and the postoperative MRI showed gross total resection. The patient had an uncomplicated hospital course and was discharged home on post-procedure day 3. neurintsurg;14/1/neurintsurg-2021-017400/V1F1V1Video 1.

Mechanical thrombectomy versus intravenous alteplase alone in acute isolated posterior cerebral artery occlusion: a systematic review.

BACKGROUND: Acute isolated posterior cerebral artery occlusions (aPCAOs) were excluded or under-represented in major randomized trials of mechanical thrombectomy (MT). The benefit of MT in comparison to intravenous tissue plasminogen activator (alteplase; IV-tPA) alone in these patients remains controversial and uncertain. METHODS: We performed a systematic search of PubMed, MEDLINE, and EMBASE databases for articles comparing MT with or without bridging IV-tPA and IV-tPA alone for aPCAO using keywords ('posterior cerebral artery', 'thrombolysis' and 'thrombectomy') with Boolean operators. Extracted data from patients reported in the studies were pooled into groups (MT vs IV-tPA alone) for comparison. Estimated rates for favorable outcome (modified Rankin scale score 0-2), symptomatic intracranial hemorrhage (sICH), and mortality were extracted. RESULTS: Seven articles (201 MT patients, 64 IV-tPA) were included, all retrospective. There was no statistically significant difference between pooled groups in median age, median presentation National Institutes of Health Stroke Scale (NIHSS) score, PCAO segment, and median time from symptom onset to puncture or needle. The recanalization rate was significantly higher in the MT group than the IV-tPA group (85.6% vs 53.1%, p<0.00001). Odds ratios for favorable outcome (OR 1.5, 95% CI 0.8 to 2.5), sICH (OR 1.1, 95% CI 0.2 to 5.5), and mortality (OR 1.4, 95% CI 0.5 to 3.6) did not significantly favor any modality. CONCLUSIONS: We found no significant differences in odds of favorable outcome, sICH, and mortality in MT and IV-tPA in comparable aPCAO patients, despite superior MT recanalization rates. Equipoise remains regarding the optimal treatment modality for these patients.

An Image-Based Workflow for Objective Vessel Wall Enhancement Quantification in Intracranial Aneurysms.

BACKGROUND: VWE in contrast-enhanced magnetic resonance imaging (MRI) is a potential biomarker for the evaluation of IA. The common practice to identify IAs with VWE is mainly based on a visual inspection of MR images, which is subject to errors and inconsistencies. Here, we develop and validate a tool for the visualization, quantification and objective identification of regions with VWE. METHODS: N = 41 3D T1-MRI and 3D TOF-MRA IA images from 38 patients were obtained and co-registered. A contrast-enhanced MRI was normalized by the enhancement intensity of the pituitary stalk and signal intensities were mapped onto the surface of IA models generated from segmented MRA. N = 30 IAs were used to identify the optimal signal intensity value to distinguish the enhancing and non-enhancing regions (marked by an experienced neuroradiologist). The remaining IAs (n = 11) were used to validate the threshold. We tested if the enhancement area ratio (EAR-ratio of the enhancing area to the IA surface-area) could identify high risk aneurysms as identified by the ISUIA clinical score. RESULTS: A normalized intensity of 0.276 was the optimal threshold to delineate enhancing regions, with a validation accuracy of 81.7%. In comparing the overlap between the identified enhancement regions against those marked by the neuroradiologist, our method had a dice coefficient of 71.1%. An EAR of 23% was able to discriminate high-risk cases with an AUC of 0.7. CONCLUSIONS: We developed and validated a pipeline for the visualization and objective identification of VWE regions that could potentially help evaluation of IAs become more reliable and consistent.

Isolation of RNA from Acute Ischemic Stroke Clots Retrieved by Mechanical Thrombectomy.

Mechanical thrombectomy (MT) for large vessel acute ischemic stroke (AIS) has enabled biologic analyses of resected clots. While clot histology has been well-studied, little is known about gene expression within the tissue, which could shed light on stroke pathophysiology. In this methodological study, we develop a pipeline for obtaining useful RNA from AIS clots. A total of 73 clot samples retrieved by MT were collected and stored in RNALater and in 10% phosphate-buffered formalin. RNA was extracted from all samples using a modified Chemagen magnetic bead extraction protocol on the PerkinElmer Chemagic 360. RNA was interrogated by UV-Vis absorption and electrophoretic quality control analysis. All samples with sufficient volume underwent traditional qPCR analysis and samples with sufficient RNA quality were subjected to next-generation RNA sequencing on the Illumina NovaSeq platform. Whole blood RNA samples from three patients were used as controls, and H&E-stained histological sections of the clots were used to assess clot cellular makeup. Isolated mRNA was eluted into a volume of 140 µL and had a concentration ranging from 0.01 ng/µL to 46 ng/µL. Most mRNA samples were partially degraded, with RNA integrity numbers ranging from 0 to 9.5. The majority of samples (71/73) underwent qPCR analysis, which showed linear relationships between the expression of three housekeeping genes (GAPDH, GPI, and HPRT1) across all samples. Of these, 48 samples were used for RNA sequencing, which had moderate quality based on MultiQC evaluation (on average, ~35 M reads were sequenced). Analysis of clot histology showed that more acellular samples yielded RNA of lower quantity and quality. We obtained useful mRNA from AIS clot samples stored in RNALater. qPCR analysis could be performed in almost all cases, while sequencing data could only be performed in approximately two-thirds of the samples. Acellular clots tended to have lower RNA quantity and quality.

Comparison of effectiveness and outcomes among different thrombectomy techniques in acute basilar artery occlusion: a dual-center experience.

OBJECTIVE: Acute basilar artery occlusion (BAO) is a rare large-vessel occlusion associated with high morbidity and mortality. Modern thrombectomy with stent retrievers and large-bore aspiration catheters is highly effective in achieving recanalization, but a direct comparison of different techniques for acute BAO has not been performed. Therefore, the authors sought to compare the technical effectiveness and clinical outcomes of stent retriever-assisted aspiration (SRA), aspiration alone (AA), and a stent retriever with or without manual aspiration (SR) for treatment of patients presenting with acute BAO and to evaluate predictors of clinical outcome in their cohort. METHODS: A retrospective analysis of databases of large-vessel occlusion treated with endovascular intervention at two US endovascular neurosurgery centers was conducted. Patients ≥ 18 years of age with acute BAO treated between January 2013 and December 2020 with stent retrievers or large-bore aspiration catheters were included in the study. Demographic information, procedural details, angiographic results, and clinical outcomes were extracted for analysis. RESULTS: Eighty-three patients (median age 67 years [IQR 58-76 years]) were included in the study; 33 patients (39.8%) were female. The median admission National Institutes of Health Stroke Scale (NIHSS) score was 16 (IQR 10-21). Intravenous alteplase was administered to 26 patients (31.3%). The median time from symptom onset to groin or wrist puncture was 256 minutes (IQR 157.5-363.0 minutes). Overall, successful recanalization was achieved in 74 patients (89.2%). The SRA technique had a significantly higher rate of modified first-pass effect (mFPE; 55% vs 31.8%, p = 0.032) but not true first-pass effect (FPE; 45% vs 34.9%, p = 0.346) than non-SRA techniques. Good outcome (modified Rankin Scale [mRS] score 0-2) was not significantly different among the three techniques. Poor outcome (mRS score 3-6) was associated with a higher median admission NIHSS score (12.5 vs 19, p = 0.007), a higher rate of adjunctive therapy usage (9% vs 0%, p < 0.001), and a higher rate of intraprocedural complications (10.7% vs 14.5%, p = 0.006). The admission NIHSS score significantly predicted good outcome (OR 0.98, 95% CI 0.97-0.099; p = 0.032). Incomplete recanalization after thrombectomy significantly predicted mortality (OR 1.68, 95% CI 1.18-2.39; p = 0.005). CONCLUSIONS: The evaluated techniques resulted in high recanalization rates. The SRA technique was associated with a higher rate of mFPE than AA and SR, but the clinical outcomes were similar. A lower admission NIHSS score predicted a better prognosis for patients, whereas incomplete recanalization after thrombectomy predicted mortality.

Placement of Left Subclavian Origin Stent for Subclavian Steal Syndrome.

Subclavian steal syndrome is characterized by the vertebral artery flow inversion as a result of a stenotic lesion in the origin of the subclavian artery. Subclavian origin stenting is an important armamentarium of neurointerventional surgeons. A 79-year-old patient presented with left arm claudication and dizziness while exercising, alongside upper extremity coolness at rest. Examination revealed blood pressure difference of 15 mm Hg in the left arm when compared with the right, with Doppler ultrasonography demonstrating reversal of flow in the left vertebral artery. Aortic arch run with pigtail catheter demonstrated the extent of stenosis and served as a roadmap for stent deployment. Placement of a long sheath across the subclavian stenosis into the aortic arch allowed atraumatic delivery and precise deployment of the covered stent (Video 1). No neurologic deficits were reported postoperatively, with Doppler ultrasonography revealing anterograde flow in the left vertebral artery demonstrating resolution of subclavian steal syndrome.

Radial first or patient first: a case series and meta-analysis of transradial versus transfemoral access for acute ischemic stroke intervention.

BACKGROUND: Few studies have compared technical success and effectiveness of transradial access (TRA) versus transfemoral access (TFA) for mechanical thrombectomy (MT) for acute ischemic stroke (AIS). We compared the two approaches for technical success, effectiveness, and outcomes. METHODS: We retrospectively compared TRA with TFA for AIS MT at our institute. We additionally performed a systematic review and meta-analysis of studies describing the use of TRA alone or in comparison with TFA for MT. Primary outcomes included rate of successful reperfusion (thrombolysis in cerebral infarction (TICI) >2b), number of passes, access-site complications, and 3- month mortality and favorable functional outcomes (modified Rankin Scale (mRS) score 0-2). RESULTS: A total of 222 consecutive patients (TRA=93, TFA=129) were included in our case series. The rate of successful reperfusion was significantly higher for the TFA cohort (91.4% vs 79.6%, P=0.01) with lower mean number of passes (1.8±1.2 vs 2.4±1.6, P=0.014). Three-month mortality in the TFA group was lower (22.1% vs 40.9% for the TRA cohort (P=0.004), with a higher rate of favorable functional outcomes (51.3% vs 34.1%, P=0.015). A meta-analysis of 10 studies showed significant heterogeneity in rates of successful reperfusion (57.1% to 95.6%, heterogeneity=67.55%, P=0.001). None of the previous comparative studies reported 3-month mortality and functional outcomes. CONCLUSIONS: This case series demonstrate a higher successful reperfusion rate, fewer passes, lower 3-month mortality, and improved 3-month functional outcomes with TFA. The systematic review highlights the inadequacy of existing evidence. Prospective comparative studies are needed before a 'radial-first' approach can be adopted for stroke intervention.

Complete flow control using transient concurrent rapid ventricular pacing or intravenous adenosine and afferent arterial balloon occlusion during transvenous embolization of cerebral arteriovenous malformations: case series.

BACKGROUND: There are no reports that describe complete flow control using concurrent transient rapid ventricular pacing or intravenous (IV) adenosine and afferent arterial balloon flow arrest to aid transvenous embolization of cerebral arteriovenous malformations (AVM). We describe our experience with the use of this technique in patients undergoing transvenous AVM embolization. METHODS: Consecutive patients in whom transvenous embolization was attempted at our institute between January 2017 and July 2019 were included. Anatomical AVM features, number of embolization stages, technique of concurrent transient rapid ventricular pacing and afferent arterial balloon flow arrest, complications, and clinical and radiological outcomes were recorded and tabulated. RESULTS: Transvenous AVM embolization was attempted in 12 patients but abandoned in two patients for technical reasons. Complete embolization was achieved in 10 patients, five of whom had infratentorial AVMs. All 10 had a single primary draining vein. Rapid ventricular pacing was used in nine cases; IV adenosine injection was used in one case to achieve cardiac standstill. Complete AVM nidus obliteration was achieved with excellent neurologic outcome in nine cases, with transvenous embolization alone in two cases, and with staged transarterial followed by transvenous embolization in the others. Two patients developed hemorrhagic complications intraprocedurally. One patient was managed conservatively and the other operatively with AVM excision and hematoma evacuation; both made an excellent recovery without any neurologic deficits at 3 months. CONCLUSION: Complete flow control using concurrent transient rapid ventricular pacing with afferent arterial balloon flow arrest technique is safe and feasible for transvenous embolization of select AVMs.

The Use of Antiplatelet Agents and Heparin in the 24-Hour Postintravenous Alteplase Window for Neurointervention.

BACKGROUND: Intravenous (IV) alteplase with mechanical thrombectomy has been found to be superior to alteplase alone in select patients with intracranial large vessel occlusion. Current guidelines discourage the use of antiplatelet agents or heparin for 24 h following alteplase. However, their use is often necessary in certain circumstances during thrombectomy procedures. OBJECTIVE: To study the safety and outcomes in patients who received blood thinning medications for thrombectomy after IV Tissue-Type plasminogen activator (tPA). METHODS: This is a multicenter retrospective review of the use of antiplatelet agents and/or heparin in patients within 24 h following tPA administration. Patient demographics, comorbidities, bleeding complications, and discharge outcomes were collected. RESULTS: A series of 88 patients at 9 centers received antiplatelet medications and/or heparin anticoagulation following IV alteplase for revascularization procedures requiring stenting. The mean National Institutes of Health Stroke Scale (NIHSS) on admission was 14.6. Reasons for use of a stent included internal carotid artery occlusion in 74% of patients. Thrombolysis in cerebral infarction (TICI) 2b-3 revascularization was accomplished in 90% of patients. The rate of symptomatic intracranial hemorrhage (sICH) was 8%; this was not significantly different than the sICH rate for a matched group of patients not receiving antiplatelets or heparin during the same time frame. Functional independence at 90 d (modified Rankin Scale 0-2) was seen in 57.8% of patients. All-cause mortality was 12%. CONCLUSION: The use of antiplatelet agents and heparin for stroke interventions following IV alteplase appears to be safe without significant increased risk of hemorrhagic complications in this group of patients when compared to control data and randomized controlled trials.

Safety and feasibility of ulnar artery access for neuroangiography and neurointervention: a case series.

BACKGROUND: Radial access has become popular among neurointerventionalists because it has favorable risk profiles compared with femoral access. Difficulties in accessing or navigating the radial artery have been viewed as a reason to convert to femoral access, but ulnar artery access may prevent complications associated with transfemoral procedures. OBJECTIVE: To evaluate the safety and feasibility of ulnar access for neurointerventions and diagnostic neuroangiographic procedures. METHODS: Consecutive patients who underwent diagnostic angiography or neurointerventional procedures via ulnar access between July 1, 2019 and April 15, 2020 were included. Data recorded were demographics, procedure indication, devices, technique, and complications. Descriptive analysis was performed. RESULTS: Ulnar artery access was obtained for 21 procedures in 18 patients (mean age 70.3±7.8 years; nine men). Procedures included 13 diagnostic angiograms and eight neurointerventions (3 left middle meningeal artery embolization, 1 of which was aborted; 2 carotid artery stenting; 2 angioplasty; 1 mechanical thrombectomy for in-stent thrombosis). A right-sided approach with ultrasound guidance was used for all cases except one. Indications included small caliber radial artery (n=9), radial artery occlusion (n=10), and radial artery preservation for potential bypass (n=2). A 5-French slender sheath was used for diagnostic angiography; a 6-French slender sheath was used for neurointerventions. No case required conversion to femoral access. Two patients had minor hematomas after the procedure; one other had ulnar artery occlusion on 30-day ultrasonography. CONCLUSION: Ulnar access is safe and feasible for diagnostic and interventional neuroangiographic procedures. It provides a useful alternative to radial access, potentially avoiding complications associated with femoral access.

Transradial access for flow diversion of intracranial aneurysms: Case series.

BACKGROUND: Transradial access for neurointerventions offers advantages of fewer access-site complications, reduced procedure time, and greater patient comfort over transfemoral access. Data about transradial access for flow diversion are limited. We share our early experience with transradial access for flow diversion in a relatively large case series. METHODS: Consecutive patients who underwent Pipeline embolization device (Medtronic) deployment via transradial access were included in the study, irrespective of location and laterality of the intracranial aneurysm. The cases were performed between July 2016 and October 2019. Demographics, aneurysm characteristics, and procedure-related details (including catheter systems used) were recorded and statistically evaluated. RESULTS: Thirty-five transradial flow diversion procedures were attempted in 32 patients, of which 33 procedures were successful. In two cases involving left common carotid artery and internal carotid artery access, guide catheter herniation into the aortic arch led to abandonment of transradial access in favor of transfemoral access. The most common aneurysm locations in the transradial access procedures were the posterior communicating artery (n = 7), ophthalmic artery (n = 7), and superior hypophyseal artery (n = 7). Most transradial access procedures (66.7%) were performed using a biaxial catheter system. 6-French Benchmark (Penumbra) and Phenom 27 (Medtronic) were the most commonly utilized guide- and microcatheters, respectively. One patient had intraprocedural subarachnoid hemorrhage. No access-site complications occurred. CONCLUSION: This study demonstrates safety and feasibility of transradial access for Pipeline embolization device deployment and shows the versatility of this approach for different catheter systems. Tortuosity and acute angulation of the left common carotid artery and internal carotid artery were associated with approach failure.

Sovereign immunity and its implications for neurosurgery.

The proportion of neurosurgeons facing a malpractice suit each year is highest among all medical and surgical specialties. It is critical for neurosurgeons to understand local malpractice laws because they vary among states. Sovereign immunity, as described in the 11th constitutional amendment, provides absolute immunity to states from being sued by their residents and by other states. A state may waive its sovereign immunity, however, and substitute itself as the defendant in place of a state-employed physician in the court of law. This means that a physician working for a state-funded hospital may not be liable to a malpractice suit. Further provisions of the law allow the state not to pay indemnity beyond a certain limit, which discourages plaintiff attorneys from pursuing indemnity charges against physicians working for state-funded institutions. In this review, the authors describe the concept of sovereign immunity and its implications for the practice of neurosurgery.

Transradial middle meningeal artery embolization for chronic subdural hematoma using Onyx: case series.

BACKGROUND: Middle meningeal artery (MMA) embolization is an emerging therapy for the resolution of subacute or chronic subdural hematoma (CSDH). CSDH patients are often elderly and have several comorbidities. We evaluated our experience with transradial access (TRA) for MMA embolization using predominantly Onyx under conscious sedation. METHODS: Data for consecutive patients who underwent transradial MMA embolization for CSDH during a 2-year period (2018-2019) were analyzed from a single-center, prospectively-maintained database. Patient demographics, comorbidities, ambulatory times, subdural hematoma resorption status, and guide catheter type were recorded. Conversion to femoral access and complication rates were also recorded. Univariate and multivariate analyses were performed. RESULTS: Forty-six patients (mean age, 71.7±14.4 years) were included in this study. Mean CSDH size was 14±5.5 mm. Most (91.3%) TRA embolizations were performed with 6-French 0.071-inch Benchmark guide catheters (Penumbra). MMA embolization was successful in 44 patients (95.7%) (including two cases of TRA conversion). Twenty-one (48%) patients had a severe Charlson Comorbidity Index (>5). Symptomatic improvement was noted in 39 of 44 patients (88.6%). Mean length of stay was 4±3 days. Patients were ambulated immediately postprocedure. At mean follow-up (8±4 weeks), 86.4% of patients had complete or partial CSDH resolution. Persistent use of antiplatelet agents after the procedure was associated with failed or minimal CSDH resorption (5 of 6, 83.3% vs 9 of 38 23.7% with complete or near-complete resolution; P=0.009). CONCLUSION: Transradial Onyx MMA embolization under conscious sedation is safe and effective for CSDH treatment. TRA may be especially useful in elderly patients with numerous comorbidities.

Measurement of instant flow reserve to quantify functional flow limitation across stenosis in intracranial atherosclerotic disease.

Angiographic stenosis may not be an accurate reflection of physiological flow limitation. Measurement of instant flow reserve (IFR) to quantify functional flow limitation across stenosis may be valuable in identifying lesions causing significant flow limitation. A case of left middle cerebral artery atherosclerotic disease is presented. Because medical therapy had failed, endovascular revascularization was chosen. In this video 1, IFR measurement to guide submaximal balloon angioplasty with a 1.5×9 mm non-compliant Mini-Trek balloon (Abbott) is demonstrated. Pressure gradient across the middle cerebral artery-M1 stenosis was measured with a Volcano pressure wire (Philips) before and after submaximal balloon angioplasty. An excellent radiographic result and flow improvement into the severely stenosed segment were achieved, with an IFR increase from 0.23 to 0.89. The degree of corresponding stenosis changed from 85% to 30%. No periprocedural complication was observed. IFR can help to identify lesions requiring treatment in select patients and prevent the tendency to overtreat a lesion that is not physiologically significant.