Making Sense of Vagus Nerve Stimulation for Stroke.

Implantable vagus nerve stimulation, paired with high-dose occupational therapy, has been shown to be effective in improving upper limb function among patients with stroke and received regulatory approval from the US Food and Drug Administration and the Centers for Medicare & Medicaid Services. Combining nonsurgical and surgical approaches of vagus nerve stimulation in recent meta-analyses has resulted in misleading reports on the efficacy of each type of stimulation among patients with stroke. This article aims to clarify the confusion surrounding implantable vagus nerve stimulation as a poststroke treatment option, highlighting the importance of distinguishing between transcutaneous auricular vagus nerve stimulation and implantable vagus nerve stimulation. Recent meta-analyses on vagus nerve stimulation have inappropriately combined studies of fundamentally different interventions, outcome measures, and participant selection, which do not conform to methodological best practices and, hence, cannot be used to deduce the relative efficacy of the different types of vagus nerve stimulation for stroke rehabilitation. Health care providers, patients, and insurers should rely on appropriately designed research to guide well-informed decisions.

Direct Versus Indirect Revascularization for Moyamoya: a Large Multicenter Study.

BACKGROUND: Moyamoya is a chronic occlusive cerebrovascular disease of unknown etiology causing neovascularization of the lenticulostriate collaterals at the base of the brain. Although revascularization surgery is the most effective treatment for moyamoya, there is still no consensus on the best surgical treatment modality as different studies provide different outcomes. OBJECTIVE: In this large case series, we compare the outcomes of direct (DR) and indirect revascularisation (IR) and compare our results to the literature in order to reflect on the best revascularization modality for moyamoya. METHODS: We conducted a multicenter retrospective study in accordance with the Strengthening the Reporting of Observational studies in Epidemiology guidelines of moyamoya affected hemispheres treated with DR and IR surgeries across 13 academic institutions predominantly in North America. All patients who underwent surgical revascularization of their moyamoya-affected hemispheres were included in the study. The primary outcome of the study was the rate of symptomatic strokes. RESULTS: The rates of symptomatic strokes across 515 disease-affected hemispheres were comparable between the two cohorts (11.6% in the DR cohort vs 9.6% in the IR cohort, OR 1.238 (95% CI 0.651 to 2.354), p=0.514). The rate of total perioperative strokes was slightly higher in the DR cohort (6.1% for DR vs 2.0% for IR, OR 3.129 (95% CI 0.991 to 9.875), p=0.052). The rate of total follow-up strokes was slightly higher in the IR cohort (8.1% vs 6.6%, OR 0.799 (95% CI 0.374 to 1.709) p=0.563). CONCLUSION: Since both modalities showed comparable rates of overall total strokes, both modalities of revascularization can be performed depending on the patient's risk assessment.

Comparison between endovascular and surgical treatment of spinal dural arteriovenous fistulas: a single-center cohort and systematic review.

OBJECTIVE: With recent advancements in minimally invasive techniques, endovascular embolization has gained popularity as a first-line treatment option for spinal dural arteriovenous fistulas (sDAVFs). The authors present their institution's case series of sDAVFs treated endovascularly and surgically, and they performed a systemic review to assess the outcomes of both modalities of treatment. METHODS: The authors conducted a retrospective observational study of 24 consecutive patients with sDAVFs treated between 2013 and 2023. The primary outcome was the rate of occlusion, which was compared between the surgically and endovascularly treated sDAVFs. They also conducted a systemic review of all the literature comparing outcomes of endovascular and surgical treatment of sDAVFs. RESULTS: A total of 24 patients with 24 sDAVFs were studied. The mean patient age was 63.8 ± 15.5 years, and the majority of patients were male (n = 19, 79.2%). Of the 24 patients, 8 (33.3%) received endovascular treatment, 15 (62.5%) received surgical treatment, and 1 (4.2%) patient received both. Complete occlusion at first follow-up was higher in the surgical cohort but did not achieve statistical significance (66.7% vs 25%, p = 0.52). Recurrence was higher in the endovascular cohort (37.5% vs 13.3%, p = 0.3), while the rate of postprocedural complications was higher in the surgical cohort (13.3% vs 0%, p = 0.52); however, neither of these differences was statistically significant. CONCLUSIONS: Endovascular embolization in the management of sDAVFs is an alternative treatment to surgery, whose long-term efficacy is still under investigation. These findings suggest overall comparable outcomes between endovascular and open surgical treatment of sDAVFs. Future studies are needed to determine the role of endovascular embolization in the overall management of sDAVFs.

Comparison of the transarterial, transvenous, and superior ophthalmic vein approaches in the treatment of indirect carotid-cavernous fistulas.

OBJECTIVE: Indirect carotid-cavernous fistulas (CCFs) are abnormal arteriovenous shunting lesions with a highly variable clinical presentation that depends on the drainage pattern. Based on venous drainage, treatment can be either transarterial (TA) or transvenous (TV). The aim of this study was to compare the outcomes of indirect CCF embolization via the TA, TV, and direct superior ophthalmic vein (SOV) approaches. METHODS: The authors conducted a retrospective analysis of 74 patients admitted to their institution from 2010 to 2023 with the diagnosis of 77 indirect CCFs as confirmed on digital subtraction angiography. RESULTS: A total of 74 patients with 77 indirect CCFs were included in this study. Embolization was performed via the TA approach in 4 cases, the TV approach in 50 cases, and the SOV in 23 cases. At the end of the procedure, complete occlusion was achieved in 76 (98.7%) cases. The rate of complete occlusion at the end of the procedure and at last radiological follow-up was significantly higher in the SOV and TV cohorts than in the TA cohort. The rate of recurrence was highest in the TA cohort (25% for TA vs 5.3% for TV vs 0% for SOV, p = 0.68). CONCLUSIONS: The rate of immediate complete occlusion was higher in the TV and SOV cohorts than in the TA cohort while the rate of complete occlusion at final follow-up was highest in the SOV cohort. The SOV approach was significantly associated with higher rates of postoperative complications. Indirect CCFs require careful examination of the fistulous point and the venous drainage to provide the most effective patient-tailored approach.

The effect of institutional case volume on post-operative outcomes after endarterectomy and stenting for symptomatic carotid stenosis.

OBJECTIVE: To investigate the effects of yearly institutional case volume for carotid endarterectomy (CEA) and stenting (CAS) among symptomatic carotid stenosis patients on the rates of postoperative stroke and inpatient mortality. MATERIALS AND METHODS: Patients with prior stroke ("symptomatic") undergoing CEA or CAS during an inpatient stay were identified from the National Inpatient Sample for years 2012-2015. The primary variable was volume of CEA or CAS performed annually by each institution. The primary outcome was a composite variable for in-hospital death or postoperative stroke. RESULTS: A total of 5,628 patients with symptomatic carotid stenosis underwent CEA, while 245 underwent CAS. In the symptomatic CEA population, 519 (9.2%) patients experienced postoperative stroke or mortality, and were more likely to be treated at centers with a lower yearly institutional volume (median 10 [IQR 5-15] versus 10 [7-20] cases, p<0.001). In the symptomatic CAS population, 32 (13.1%) patients experienced stroke or mortality, and these patients were also more likely to undergo treatment at hospitals with a lower yearly institutional volume (median 5 [IQR 5-7] versus 5 [5-10] cases, p=0.044). Thresholds for yearly institutional volume found differences in adverse outcome between 0-9, 10-29, and ≥30 cases/year (11.7% vs 8.4% vs 6.0%, p<0.001) for CEA, and differences in postoperative stroke between 0-9 and ≥10 cases/year for CAS (11.0% vs 1.4%, p=0.028). CONCLUSIONS: Hospitals performing higher volumes of CEA or CAS have fewer postoperative strokes. The threshold reported herein is ≥30 CEA procedures or ≥10 CAS procedures annually for appreciably improved outcomes.

Predictors of aneurysm occlusion following treatment with the WEB device: systematic review and case series.

The Woven EndoBridge (WEB) device is becoming increasingly popular for treatment of wide-neck aneurysms. As experience with this device grows, it is important to identify factors associated with occlusion following WEB treatment to guide decision making and screen patients at high risk for recurrence. The aim of this study was to identify factors associated with adequate aneurysm occlusion following WEB device treatment in the neurosurgical literature and in our case series. A systematic review of the present literature was conducted to identify studies related to the prediction of WEB device occlusion. In addition, a retrospective review of our institutional data for patients treated with the WEB device was performed. Demographics, aneurysm characteristics, procedural variables, and 6-month follow-up angiographic outcomes were recorded. Seven articles totaling 450 patients with 456 aneurysms fit our criteria. Factors in the literature associated with inadequate occlusion included larger size, increased neck width, partial intrasaccular thrombosis, irregular shape, and tobacco use. Our retrospective review identified 43 patients with 45 aneurysms. A total of 91.1% of our patients achieved adequate occlusion at a mean follow-up time of 7.32 months. Increasing degree of contrast stasis after WEB placement on the post-deployment angiogram was significantly associated with adequate occlusion on follow-up angiogram (p = 0.005) and with Raymond-Roy classification (p = 0.048), but not with retreatment (p = 0.617). In our systematic review and case series totaling 450 patients with 456 aneurysms, contrast stasis on post-deployment angiogram was identified as a predictor of adequate aneurysm occlusion, while morphological characteristics such as larger size and wide neck negatively impact occlusion.

Robot-assisted carotid artery stenting: outcomes, safety, and operational learning curve.

OBJECTIVE: Over the past 2 decades, robots have been increasingly used in surgeries to help overcome human limitations and perform precise and accurate tasks. Endovascular robots were pioneered in interventional cardiology, however, the CorPath GRX was recently approved by the FDA for peripheral vascular and extracranial interventions. The authors aimed to evaluate the operational learning curve for robot-assisted carotid artery stenting over a period of 19 months at a single institution. METHODS: A retrospective analysis of a prospectively maintained database was conducted, and 14 consecutive patients who underwent robot-assisted carotid artery stenting from December 2019 to June 2021 were identified. The metrics for proficiency were the total fluoroscopy and procedure times, contrast volume used, and radiation dose. To evaluate operator progress, the patients were divided into 3 groups of 5, 4, and 5 patients based on the study period. RESULTS: A total of 14 patients were included. All patients received balloon angioplasty and stent placement. The median degree of stenosis was 95%. Ten patients (71%) were treated via the transradial approach and 4 patients (29%) via the transfemoral approach, with no procedural complications. The median contrast volume used was 80 mL, and the median radiation dose was 38,978.5 mGy/cm2. The overall median fluoroscopy and procedure times were 24.6 minutes and 70.5 minutes, respectively. Subgroup analysis showed a significant decrease in these times, from 32 minutes and 86 minutes, respectively, in group 1 to 21.9 minutes and 62 minutes, respectively, in group 3 (p = 0.002 and p = 0.008, respectively). CONCLUSIONS: Robot-assisted carotid artery stenting was found to be safe and effective, and the learning curve for robotic procedures was overcome within a short period of time at a high-volume cerebrovascular center.

Mechanical Thrombectomy in Patients Presenting with NIHSS Score <6: A Safety and Efficacy Analysis.

BACKGROUND AND OBJECTIVES: Groundbreaking trials have shown the tremendous efficacy of mechanical thrombectomy for large vessel occlusions. Currently, mechanical thrombectomy is limited to patients with NIHSS scores ≥6. We investigated the feasibility and safety of MT in patients presenting with NIHSS scores <6. MATERIALS AND METHODS: A retrospective review of patient who presented with acute ischemic stroke due to large vessel occlusion with an NIHSS score <6 between 2015 - 2021. The patients were then divided into two groups: those who received mechanical thrombectomy and those who did not. RESULTS: Among 83 patients, 41 received a mechanical thrombectomy while 42 received medical treatment only. The mean age in the mechanical thrombectomy group was 66 years versus 60 years in the medical group (p = 0.06). Risk factors for stroke did not differ significantly between both groups. 14 patients (34.1%) in the mechanical thrombectomy group and 20 (47.6%) in the medical group received tissue plasminogen activator. No significant difference in clinical improvement (NIHSS) at discharge (p=0.85) or the mRS score at 90 days (p = 0.15) was noted. Mechanical thrombectomy was associated with smaller infarct size (p=0.04) and decreased mortality (p=0.03). CONCLUSIONS: Mechanical thrombectomy is safe and effective for patients who present with large vessel occlusions and low initial NIHSS scores. Therefore, the decision to offer the patient mechanical thrombectomy or not should not be decided by NIHSS score alone. Rather, the decision should be multifactorial with the aim of maximizing the patients' outcomes.

A comparative study of transradial versus transfemoral approach for flow diversion.

PURPOSE: Data in neurointerventional literature is extremely limited regarding the safety and efficacy of flow diversion using transradial access (TRA). We aim to demonstrate the safety and efficacy of intracranial aneurysm treatment with the Pipeline Embolization Device (PED) using TRA compared to transfemoral access (TFA). METHODS: We conducted a retrospective analysis of a prospectively maintained database and identified 79 consecutive patients who underwent neuroendovascular embolization for cerebral aneurysms using the PED from April 2018 through October 2019. Patients were divided into 2 groups: TRA (32 patients) and TFA (47 patients). A comparative analysis was performed between the two groups. RESULTS: There was no significant difference in postoperative intracranial hemorrhage (p>.99), symptomatic ischemic stroke (p=.512), access site complications (p=.268), or other complications (p=.512). However, there was a significant increase in overall complications (14.9% vs. 0.0%, p=.038) and procedure duration (71.4 min ± 31.2 vs. 58.5 ± 20.3, p=.018) in the TFA group. There was no significant difference in complete occlusion at latest follow-up (19/25, 76.0% vs. 35/40, 87.5%; p=.311), 6-month follow-up (17/23, 73.9% vs. 33/38, 86.8%; p=.303), or 12-month follow-up (8/8, 100.0% vs. 5/6, 83.3%; p=.429). There was also no significant difference in rate of retreatment (p>.99), morbidity (p=.512), mortality (p>.99), latest follow-up (p=.985), or loss of follow-up (p=.298). CONCLUSIONS: The feasibility and efficacy of flow diversion with the PED via TRA for the treatment of intracranial aneurysms is comparable to TFA. Widespread adoption of this approach may be facilitated by improvements in device navigation and manipulation via radial-specific engineering.

Low diagnostic yield in follow-up MR imaging in patients with spontaneous intracerebral hemorrhage with a negative initial MRI.

PURPOSE: Follow-up MRI/MRA is historically obtained as outpatient when patients with a spontaneous intracerebral hemorrhage (ICH) have an initial MRI/MRA that is negative for an underlying structural lesion. However, the utility of repeating MR imaging in a delayed fashion remains uncertain. METHODS: We retrospectively reviewed 396 patients with spontaneous ICH admitted at our institution between 2015 and 2017 and selected those whose initial MRI/MRA was negative for an underlying structural lesion and those who underwent follow-up MR imaging in a delayed fashion. RESULTS: A total of 113 patients met the study criteria. The average age of those with negative follow-up MRI/MRA was 65.0 ± 12.6 (IQR: 55.0-74.0) years old. None of the 113 patients with a negative inpatient MRI/MRA had an underlying structural lesion on follow-up MRI/MRA (0%, 95% CI 0.0-0.032, p < 0.001). The mean time of the follow-up imaging from the initial study was 105.7 days (median: 62 days; IQR: 42.5-100.5). Of the 113, 83 (73.5%) underwent follow-up MRI with and without gadolinium, while 30 (26.5%) patients did not receive gadolinium. CONCLUSION: Delayed follow-up MRI in patients with a negative initial MRI/MRA for workup of spontaneous ICH was not diagnostic in any of the patients included in the study. Our study suggests that a routine follow-up MRI for this patient population is not necessary.

An artificial nervous system to treat chronic stroke.

Despite remarkable advances in the treatment of numerous medical conditions, neurological disease and injury remains an outstanding challenge and cause of disability worldwide. The decreased regenerative capacity and extreme complexity and heterogeneity of nervous tissue, in particular the brain, and the fact that the brain remains the least understood organ, have hampered our ability to provide definitive treatments for prevalent conditions such as stroke. Stroke is the second-leading cause of death worldwide, and the nervous system is intimately involved in other prevalent conditions including ischemic heart disease, diabetes mellitus, and hypertension. Advances in neuromodulation, electroceuticals, microsurgical techniques, optogenetics, brain-computer interfaces, and autologous constructs offer potential solutions to address the otherwise permanent neurological deficits of stroke and other conditions. Here we review these various approaches to build an "artificial nervous system" that could restore function and independence in people living with these conditions. We focus on stroke both because it is the leading cause of neurological disability worldwide and because we anticipate that advances in the reversal of stroke-related deficits will have ripple effects benefiting people with other neurological conditions including spinal cord injury, traumatic brain injury, ALS, and muscular dystrophy.

Rapid Decline in Telestroke Consults in the Setting of COVID-19.

Background and Purpose: As coronavirus disease 2019 (COVID-19) continues to be a global pandemic, there is a growing body of evidence suggesting that incidence of diseases that require emergent care, particularly myocardial infarction and ischemic stroke, has declined rapidly. The objective of this study is to quantify our experience of telestroke (TS) consults at a large tertiary comprehensive stroke center during the COVID-19 pandemic. Methods: We retrospectively reviewed TS consults of patients presenting to our neuroscience network. Those with a confirmed diagnosis of acute ischemic stroke or transient ischemia attack were included. Data were compared from April 1, 2019, to June 30, 2020, which include consults prepandemic and during the crisis. Results: A total of 1,982 TS consults were provided in 1 year. Prepandemic, the mean monthly consults were 148. In April 2020, only 59 patients were seen (49% decline). Mobile stroke unit consults decreased by 72% in the same month. The 30-day moving average of patients seen per day was between five and six prepandemic declined to between two and three in April, and then began to uptrend during May. The mean percentage of patients receiving intravenous tissue plasminogen activator was 16% from April 2019 to March 2020 and increased to 31% in April 2020. The mean percentage of patients receiving endovascular therapy was 10% from April 2019 to March 2020 and increased to 19% in April 2020. Conclusions: At our large tertiary comprehensive stroke center, we observed a significant and rapid decline in TS consults during the COVID-19 pandemic. We cannot be certain of the reasons for the decline, but a fear of contracting coronavirus, social distancing, and isolation likely played a major role. Further research must be done to elucidate the etiology of this decline.

Adoption of the Transradial Approach for Neurointerventions: A National Survey of Current Practitioners.

OBJECTIVES: The transradial approach (TRA) is technically feasible for both diagnostic and therapeutic neurointerventions. It improves patient comfort and is not associated with increased procedural complications when compared to the transfemoral approach (TFA). To date, no studies have looked at barriers to adoption of TRA in the neurointerventionalist community. This study aims to obtain neurointerventionalist perspectives on their adoption of TRA. MATERIALS AND METHODS: Online survey distributed to neurointerventionalists. RESULTS: A total of 55 neurointerventionalists, 52 of whom utilized TRA, responded to our survey. Overall, participants were not concerned about TRA's technical feasibility for diagnostic or therapeutic neurointerventions or about procedural complications. Most of our cohort adopted TRA due to its increased patient comfort and to reduce access site complications. In-institution interventionalists were strongly perceived to be the most effective method of teaching TRA when compared to other methods. Catheters and equipment issues were reported by about 30% of our cohort as a barrier to TRA adoption. CONCLUSIONS: The neurointerventionalist community largely perceives TRA to be technically feasible and was not concerned about its procedural complications. In-person institutionalists are strongly perceived to be the most effective method of teaching the approach. A significant barrier to adoption seems to be related to catheters and equipment issues.

A Machine Learning Approach to First Pass Reperfusion in Mechanical Thrombectomy: Prediction and Feature Analysis.

INTRODUCTION: Novel machine learning (ML) methods are being investigated across medicine for their predictive capabilities while boasting increased adaptability and generalizability. In our study, we compare logistic regression with machine learning for feature importance analysis and prediction in first-pass reperfusion. METHODS: We retrospectively identified cases of ischemic stroke treated with mechanical thrombectomy (MT) at our institution from 2012-2018. Significant variables used in predictive modeling were demographic characteristics, medical history, admission NIHSS, and stroke characteristics. Outcome was binarized TICI on first pass (0-2a vs 2b-3). Shapley feature importance plots were used to identify variables that strongly affected outcomes. RESULTS: Accuracy for the Random Forest and SVM models were 67.1% compared to 65.8% for the logistic regression model. Brier score was lower for the Random Forest model (0.329 vs 0.342) indicating better predictive capability. Other supervised learning models performed worse than the logistic regression model, with accuracy of 56.2% for Naïve Bayes and 61.6% for XGBoost. Shapley plots for the Random Forest model showed use of aspiration, hyperlipidemia, hypertension, use of stent retriever, and time between symptom onset and catheterization as the top five predictors of first pass reperfusion. CONCLUSION: Use of machine learning models, such as Random Forest, for the study of MT outcomes, is more accurate than logistic regression for our dataset, and identifies new factors that contribute to achieving first pass reperfusion. The benefits of machine learning, such as improved predictive capabilities, integration of new data, and generalizability, establish ML as the preferred model for studying outcomes in stroke.

Discrepancies in Stroke Distribution and Dataset Origin in Machine Learning for Stroke.

BACKGROUND: Machine learning algorithms depend on accurate and representative datasets for training in order to become valuable clinical tools that are widely generalizable to a varied population. We aim to conduct a review of machine learning uses in stroke literature to assess the geographic distribution of datasets and patient cohorts used to train these models and compare them to stroke distribution to evaluate for disparities. AIMS: 582 studies were identified on initial searching of the PubMed database. Of these studies, 106 full texts were assessed after title and abstract screening which resulted in 489 papers excluded. Of these 106 studies, 79 were excluded due to using cohorts from outside the United States or being review articles or editorials. 27 studies were thus included in this analysis. SUMMARY OF REVIEW: Of the 27 studies included, 7 (25.9%) used patient data from California, 6 (22.2%) were multicenter, 3 (11.1%) were in Massachusetts, 2 (7.4%) each in Illinois, Missouri, and New York, and 1 (3.7%) each from South Carolina, Washington, West Virginia, and Wisconsin. 1 (3.7%) study used data from Utah and Texas. These were qualitatively compared to a CDC study showing the highest distribution of stroke in Mississippi (4.3%) followed by Oklahoma (3.4%), Washington D.C. (3.4%), Louisiana (3.3%), and Alabama (3.2%) while the prevalence in California was 2.6%. CONCLUSIONS: It is clear that a strong disconnect exists between the datasets and patient cohorts used in training machine learning algorithms in clinical research and the stroke distribution in which clinical tools using these algorithms will be implemented. In order to ensure a lack of bias and increase generalizability and accuracy in future machine learning studies, datasets using a varied patient population that reflects the unequal distribution of stroke risk factors would greatly benefit the usability of these tools and ensure accuracy on a nationwide scale.

Comparison of Anesthetic Agents Dexmedetomidine and Midazolam During Mechanical Thrombectomy.

OBJECTIVES: The ideal anesthetic for mechanical thrombectomy (MT) is a subject of debate. Recent studies have supported the use of monitored anesthesia care (MAC), but few have attempted to compare MAC neuroanesthetics. Our study directly compares midazolam and dexmedetomidine (DEX) on blood pressure control during thrombectomy and functional outcomes at discharge. MATERIALS AND METHODS: We performed a retrospective review of an MT database, which consisted of 612 patients admitted between 2010-2019 to our tertiary stroke center. 193 patients who received either midazolam or DEX for MAC induction were identified. Primary and secondary outcomes were >20% maximum decrease in mean arterial pressure during MT and functional independence respectively. RESULTS: 146 patients were administered midazolam, while 47 were administered DEX. Decrease in blood pressure (BP) during MT was associated with lower rates of functional independence at last follow-up (p=0.034). When compared to midazolam, DEX had significantly higher rates of intraprocedural decrease in MAP at the following cut-offs: >20% (p<0.001), >30% (p=0.001), and >40% (p=0.006). On multivariate analysis, DEX was an independent predictor of >20% MAP decrease (OR 7.042, p<0.001). At time of discharge, NIHSS scores and functional independence (mRS 0-2) were statistically similar between DEX and midazolam. Functional independence at last known follow-up was statistically similar between DEX and midazolam (p = 0.643). CONCLUSIONS: Use of DEX during MT appears to be associated with increased blood pressure volatility when compared to midazolam. Further investigation is needed to determine the impact of MAC agents on functional independence.

Systemic Factors Trigger Vasculature Cells to Drive Notch Signaling and Neurogenesis in Neural Stem Cells in the Adult Brain.

It is well documented that adult neural stem cells (NSCs) residing in the subventricular zone (SVZ) and the subgranular zone (SGZ) are induced to proliferate and differentiate into new neurons after injury such as stroke and hypoxia. However, the role of injury-related cues in driving this process and the means by which they communicate with NSCs remains largely unknown. Recently, the coupling of neurogenesis and angiogenesis and the extensive close contact between vascular cells and other niche cells, known as the neurovascular unit (NVU), has attracted interest. Further facilitating communication between blood and NSCs is a permeable blood-brain-barrier (BBB) present in most niches, making vascular cells a potential conduit between systemic signals, such as vascular endothelial growth factor (VEGF), and NSCs in the niche, which could play an important role in regulating neurogenesis. We show that the leaky BBB in stem cell niches of the intact and stroke brain can respond to circulating VEGF165 to drive induction of the Notch ligand DLL4 (one of the most important cues in angiogenesis) in endothelial cells (ECs), pericytes, and further induce significant proliferation and neurogenesis of stem cells. Stem Cells 2019;37:395-406.

Status of SARS-CoV-2 in cerebrospinal fluid of patients with COVID-19 and stroke.

BACKGROUND: Emergence of the novel corona virus (severe acute respiratory syndrome (SARS)-CoV-2) in December 2019 has led to the COVID-19 pandemic. The extent of COVID-19 involvement in the central nervous system is not well established, and the presence or the absence of SARS-CoV-2 particles in the cerebrospinal fluid (CSF) is a topic of debate. CASE DESCRIPTION: We present two patients with COVID-19 and concurrent neurological symptoms. Our first patient is a 31-year-old man who had flu-like symptoms due to COVID-19 and later developed an acute-onset severe headache and loss of consciousness and was diagnosed with a Hunt and Hess grade 3 subarachnoid haemorrhage from a ruptured aneurysm. Our second patient is a 62-year-old woman who had an ischaemic stroke with massive haemorrhagic conversion requiring a decompressive hemicraniectomy. Both patients' CSF was repeatedly negative on real-time PCR analysis despite concurrent neurological disease. CONCLUSION: Our report shows that patients' CSF may be devoid of viral particles even when they test positive for COVID-19 on a nasal swab. Whether SARS-CoV-2 is present in CSF may depend on the systemic disease severity and the degree of the virus' nervous tissue tropism and should be examined in future studies.

Radial Artery Catheterization for Neuroendovascular Procedures.

Background and Purpose- Radial artery catheterization is an alternate route of access that has started to gain more widespread use for neuroendovascular procedures, and there have been few studies that describe its safety and efficacy. We present our institution's experience in performing neuroendovascular interventions via a transradial approach, with excellent clinical outcomes and patient satisfaction measures. Methods- We conducted a retrospective analysis and identified 223 patients who underwent 233 consecutive neuroendovascular interventions via radial artery access at our institution. The incidence of perioperative and postprocedural complications was investigated. We identified a subset of 98 patients who have undergone both transradial and transfemoral cerebral angiograms and compared clinical outcomes and patient satisfaction measures between the 2 groups. Results- The overall incidence of complications was low across all procedures performed via transradial access. Peri-procedurally, only 2 patients had symptomatic radial artery spasm, and there were no instances of iatrogenic complications (vessel dissection, stroke, and hemorrhage). In 10 cases (4.3%), the intended procedure could not be completed via a transradial approach, and, thus, femoral artery access had to be pursued instead. Ten patients complained of minor postprocedural complications, although none required therapeutic intervention. The mean procedure time was shorter for diagnostic angiograms performed via transradial versus transfemoral access (18.8±15.8 versus 39.5±31.1 minutes; P=0.025). Patients overall reported shorter recovery times with transradial access, and the majority of patients (94%) would elect to have subsequent procedures performed via this route. Conclusions- Radial artery catheterization is a safe and durable alternative to perform a wide range of neuroendovascular procedures, with a low rate of complications. On the whole, patients prefer transradial compared with transfemoral access.

Introduction: Endovascular Neurosurgery.

Remarkable developments in the field of endovascular neurosurgery have been witnessed in the last decade. The success of endovascular therapy for ischemic stroke treatment is now irrefutable, making it an accepted standard of care. Endovascular treatment of cerebral aneurysms is no longer limited to primary coiling but now includes options such as stent or balloon assistance and flow diversion and applications utilizing neck reconstruction, intrasaccular, and bifurcation-specific devices. Balloons, liquid embolic agents, and flow-directed catheters have revolutionized the treatment of arteriovenous malformations and fistulae. The ongoing development of endovascular tools has led to novel and expanding approaches (for example, transvenous arteriovenous malformation embolization and transradial access). With improved technology, transposterior communicating artery access and other endovascular strategies are being applied successfully across the anterior and posterior circulations and to lesions once deemed only surgically approachable. Yet, we would be remiss to attribute the successes of endovascular strategies only to the development of their tools. Improvements in both noninvasive and angiographic imaging (such as three-dimensional road map guidance) have provided a greater understanding of pathologic entities and allowed the pursuit of endovascular cures.In this issue of Neurosurgical Focus, we present a wide range of endovascular strategies for a variety of neurovascular pathologies. We hope this video supplement will not only demonstrate the applicability of tried-and-true endovascular strategies to difficult clinical situations but also highlight new and developing endovascular technologies. We thank the authors for their outstanding contributions.