Arteriovenous shunts of the cervical spine: patient demographics, presentation, patterns of high-risk venous drainage, and updated classification.

BACKGROUND: Intracranial dural arteriovenous (AV) fistula classifications focus on presence/absence of retrograde flow in the cortical veins of the brain as this angiographic finding portends a worse prognosis. However, prior categorization systems of AV shunts in the spine do not incorporate these features. We propose an updated classification for spinal shunting lesions that terms any shunting lesion with retrograde flow in any cortical vein of the brain or spinal cord medullary vein as "high risk". To present this classification, we analyzed our center's most recent experience with cervical spine shunting lesions. METHODS: The electronic medical record at our institution was reviewed to identify shunting lesions of the cervical spine and patient demographics/presentation. Comprehensive craniospinal digital subtraction angiograms were evaluated to classify shunt location, type (arteriovenous malformation (AVM) vs arteriovenous fistula (AVF)), and presence of high-risk venous drainage. RESULTS: Some 52 lesions were identified and categorized as pial/dural/epidural/paravertebral AVFs and intramedullary/extraspinal AVMs. Lesions were classified as high risk or not depending on the presence of retrograde flow into at least one vein that directly drains the spinal cord or brain. All patients who presented with either hemorrhage or infarct had underlying high-risk lesions. Additionally, 50% (17/34) of symptomatic patients with high-risk lesions presented with neurological extremity symptoms (OR=10.0, p=0.037) most of which fit a myelopathic pattern. CONCLUSION: We present an updated classification system for shunting lesions of the spine that focuses on high-risk retrograde flow to the brain or spine in addition to anatomical location in order to better inform patient management.

Robotic Diagnostic Cerebral Angiography: A Multicenter Experience of 113 Patients.

BACKGROUND: Neurointerventional robotic systems have potential to reduce occupational radiation, improve procedural precision, and allow for future remote teleoperation. A limited number of single institution case reports and series have been published outlining the safety and feasibility of robot-assisted diagnostic cerebral angiography. METHODS: This is a multicenter, retrospective case series of patients undergoing diagnostic cerebral angiography at three separate institutions - University of California, Davis (UCD); University of California, Los Angeles (UCLA); and University of California, San Francisco (UCSF). The equipment used was the CorPath GRX Robotic System (Corindus, Waltham, MA). RESULTS: A total of 113 cases were analyzed who underwent robot-assisted diagnostic cerebral angiography from September 28, 2020 to October 27, 2022. There were no significant complications related to use of the robotic system including stroke, arterial dissection, bleeding, or pseudoaneurysm formation at the access site. Using the robotic system, 88 of 113 (77.9%) cases were completed successfully without unplanned manual conversion. The principal causes for unplanned manual conversion included challenging anatomy, technical difficulty with the bedside robotic cassette, and hubbing out of the robotic system due to limited working length. For robotic operation, average fluoroscopy time was 13.2 min (interquartile range (IQR), 9.3 to 16.8 min) and average cumulative air kerma was 975.8 mGY (IQR, 350.8 to 1073.5 mGy). CONCLUSIONS: Robotic cerebral angiography with the CorPath GRX Robotic System is safe and easily learned by novice users without much prior manual experience. However, there are technical limitations such as a short working length and an inability to support 0.035" wires which may limit its widespread adoption in clinical practice.

Clinical evaluation of pulsatile tinnitus: history and physical examination techniques to predict vascular etiology.

BACKGROUND: Pulsatile tinnitus (PT) may be due to a spectrum of cerebrovascular etiologies, ranging from benign venous turbulence to life threatening dural arteriovenous fistulas. A focused clinical history and physical examination provide clues to the ultimate diagnosis; however, the predictive accuracy of these features in determining PT etiology remains uncertain. METHODS: Patients with clinical PT evaluation and DSA were included. The final etiology of PT after DSA was categorized as shunting, venous, arterial, or non-vascular. Clinical variables were compared between etiologies using multivariate logistic regression, and performance at predicting PT etiology was determined by area under the receiver operating curve (AUROC). RESULTS: 164 patients were included. On multivariate analysis, patient reported high pitch PT (relative risk (RR) 33.81; 95% CI 3.81 to 882.80) compared with exclusively low pitch PT and presence of a bruit on physical examination (9.95; 2.04 to 62.08; P=0.007) were associated with shunting PT. Hearing loss was associated with a lower risk of shunting PT (0.16; 0.03 to 0.79; P=0.029). Alleviation of PT with ipsilateral lateral neck pressure was associated with a higher risk of venous PT (5.24; 1.62 to 21.01; P=0.010). An AUROC of 0.882 was achieved for predicting the presence or absence of a shunt and 0.751 for venous PT. CONCLUSION: In patients with PT, clinical history and physical examination can achieve high performance at detecting a shunting lesion. Potentially treatable venous etiologies may also be suggested by relief with neck compression.

Clarifying the clinical landscape of pediatric spinal arteriovenous shunts: an institutional experience and individual patient-data meta-analysis.

BACKGROUND: Pediatric spinal arteriovenous shunts (SAVS) are rare lesions with heterogeneous pathogenesis and clinical manifestations. OBJECTIVE: To evaluate the clinical characteristics, angioarchitecture, and technical/clinical outcomes in SAVS through a large single-center cohort analysis and meta-analysis of individual patient data. METHODS: A retrospective institutional database identified children (aged 0-21 years) who underwent digital subtraction spinal angiography (DSA) for SAVS between January 1996 and July 2021. Clinical data were recorded to evaluate angioarchitecture, generate modified Aminoff-Logue gait disturbance scores (AL) and McCormick grades (MC), and assess outcomes. We then performed a systematic literature review following PRISMA-IPD (Preferred Reporting Items for Systematic Reviews and Meta-Analyses for individual patient data) guidelines, extracting similar data on individual patients for meta-analysis. RESULTS: The cohort consisted of 28 children (M:F=11:17) with 32 SAVS lesions, with a mean age of 12.8±1.1 years at diagnosis. At presentation, SAVS were most highly concentrated in the cervical region (40.6%). Children had a median AL=2 and MC=2, with thoracolumbar AVS carrying the greatest disability. Among treated cases, complete obliteration was achieved in 48% of cases and median AL scores and MC grades both improved by one point. Systematic literature review identified 161 children (M:F=96:65) with 166 SAVS lesions with a mean age of 8.7±0.4 years. Among studies describing symptom chronicity, 37/51 (72.5%) of children presented acutely. At presentation, children had a median AL=4 and MC=3, with thoracolumbar AVS carrying the highest MC grades. After intervention, median AL and MC both improved by one point. CONCLUSIONS: This study provides epidemiologic information on the location, onset, and presentation of the full spectrum of pediatric SAVS, highlighting the role of targeted treatment of high-risk features.

A Deep Learning Approach for Automated Bone Removal from Computed Tomography Angiography of the Brain.

Advanced visualization techniques such as maximum intensity projection (MIP) and volume rendering (VR) are useful for evaluating neurovascular anatomy on CT angiography (CTA) of the brain; however, interference from surrounding osseous anatomy is common. Existing methods for removing bone from CTA images are limited in scope and/or accuracy, particularly at the skull base. We present a new brain CTA bone removal tool, which addresses many of these limitations. A deep convolutional neural network was designed and trained for bone removal using 72 brain CTAs. The model was tested on 15 CTAs from the same data source and 17 CTAs from an independent external dataset. Bone removal accuracy was assessed quantitatively, by comparing automated segmentation results to manual segmentations, and qualitatively by evaluating VR visualization of the carotid siphons compared to an existing method for automated bone removal. Average Dice overlap between automated and manual segmentations from the internal and external test datasets were 0.986 and 0.979 respectively. This was superior compared to a publicly available noncontrast head CT bone removal algorithm which had a Dice overlap of 0.947 (internal dataset) and 0.938 (external dataset). Our algorithm yielded better VR visualization of the carotid siphons than the publicly available bone removal tool in 14 out of 15 CTAs (93%, chi-square statistic of 22.5, p-value of < 0.00001) from the internal test dataset and 15 out of 17 CTAs (88%, chi-square statistic of 23.1, p-value of < 0.00001) from the external test dataset. Bone removal allowed subjectively superior MIP and VR visualization of vascular anatomy/pathology. The proposed brain CTA bone removal algorithm is rapid, accurate, and allows superior visualization of vascular anatomy and pathology compared to other available techniques and was validated on an independent external dataset.

Head CT deep learning model is highly accurate for early infarct estimation.

Non-contrast head CT (NCCT) is extremely insensitive for early (< 3-6 h) acute infarct identification. We developed a deep learning model that detects and delineates suspected early acute infarcts on NCCT, using diffusion MRI as ground truth (3566 NCCT/MRI training patient pairs). The model substantially outperformed 3 expert neuroradiologists on a test set of 150 CT scans of patients who were potential candidates for thrombectomy (60 stroke-negative, 90 stroke-positive middle cerebral artery territory only infarcts), with sensitivity 96% (specificity 72%) for the model versus 61-66% (specificity 90-92%) for the experts; model infarct volume estimates also strongly correlated with those of diffusion MRI (r2 > 0.98). When this 150 CT test set was expanded to include a total of 364 CT scans with a more heterogeneous distribution of infarct locations (94 stroke-negative, 270 stroke-positive mixed territory infarcts), model sensitivity was 97%, specificity 99%, for detection of infarcts larger than the 70 mL volume threshold used for patient selection in several major randomized controlled trials of thrombectomy treatment.

Cerebrovascular pulsatile tinnitus: causes, treatments, and outcomes in 164 patients with neuroangiographic correlation.

BACKGROUND: Pulsatile tinnitus (PT) can cause significant detriment to quality of life and may herald a life-threatening condition. Endovascular evaluation is the gold standard for the definitive diagnosis of PT and facilitates treatment. However, no large study has determined the distribution of causes and treatment outcomes of PT evaluated endovascularly. METHODS: Consecutive patients evaluated at a multidisciplinary PT clinic from a single academic center were retrospectively reviewed. Patients with a suspected cerebrovascular etiology of PT based on clinical and/or non-invasive imaging, who were evaluated by endovascular techniques (arteriography, venography, manometry, and/or balloon test occlusion), were included in analysis. Baseline clinical features and treatment results by final etiology of PT were compared. RESULTS: Of 552 patients referred for PT evaluation, 164 patients (29.7%) who underwent endovascular evaluation of PT were included. Mean (±SD) age at first clinical evaluation was 54.3±14.1 years (range 25-89 years); 111 patients (67.7%) were female. PT causes were 75.6% vascular and 24.4% non-vascular. Arteriovenous shunting lesions caused 20.7% of cases, venous etiologies 48.2%, and arterial etiologies 6.7%. Of patients with a shunting lesion treated with endovascular embolization, 96.9% had lasting significant improvement or resolution in PT. Endovascular stenting for venous sinus stenosis gave 84.6% of patients lasting improvement or resolution in PT. Arterial and non-vascular PT had fewer patients treated endovascularly and less improvement in PT symptoms. CONCLUSION: PT with a suspected vascular cause is most often attributable to venous etiologies. PT caused by arteriovenous shunting or venous sinus stenosis may be effectively treated endovascularly.

Percutaneous sclerotherapy for head and neck lymphatic malformations in neonates and infants ≤12 months of age.

BACKGROUND: Percutaneous sclerotherapy is an effective treatment for lymphatic malformations (LM) of the head and neck in adults. The purpose of this study was to examine the indications and efficacy of sclerotherapy for head/neck LM in the neonate and infant population. METHODS: We retrospectively reviewed patients treated with percutaneous sclerotherapy for LM of the head/neck at age ≤12 months at a single vascular anomalies clinic. The clinical, anatomic, and technical aspects of each treatment, complications, and post-treatment clinical and imaging outcomes were analyzed. RESULTS: 22 patients underwent 36 treatments during the first year of life. Median age at first treatment was 6.2 months (range 2-320 days). Severe airway compromise was the most frequent indication for treatment (31.8%). Sclerosants included doxycycline (80.5%), sodium tetradecyl sulfate (55.5%), bleomycin (11.1%) and ethanol (2.8%). There were no immediate procedure-related complications; sclerosant-related laboratory complications included transient metabolic acidosis (8.3%) and hemolytic anemia (5.5%). Median follow-up was 3.7 years (IQR 0.6-4.8). 47.6% of patients showed >75% lesion size reduction and 19.0% showed minimal response (<25% improvement). At last follow-up, 71.4% of children were developmentally normal and asymptomatic, 23.8% had recurring symptoms, and 4.8% required permanent tracheostomy. Patients with ongoing symptoms or limited response to percutaneous sclerotherapy (33.3%) were treated with long-term sirolimus. CONCLUSIONS: Percutaneous sclerotherapy is a safe and effective treatment for symptomatic LM of the head and neck in neonates and infants. Treatment strategy and management of recurrent symptoms requires consensus from an experienced, multidisciplinary team.

Dual-agent percutaneous sclerotherapy technique for macrocystic lymphatic malformations.

Percutaneous sclerotherapy is an effective technique for treating lymphatic malformations of the head and neck, with clinical success rates exceeding 84%.1 Sodium tetradecyl, which damages lipid membranes and stimulates free radical-induced local damage, and doxycycline, which inhibits angiogenesis, have emerged as the safest and most effective of several available sclerosants.2-4 Although severe periprocedural morbidity is rare, temporary local complications are reported in 14% and skin necrosis or scarring in up to 0.8-5.8% of sclerotherapy procedures.5 As these lesions are frequently located in the face and/or neck, even minor complications can be disfiguring and must be avoided. This technical video describes a 'dual-agent' approach for percutaneous sclerotherapy of macrocystic lymphatic malformations using sodium tetradecyl as a 'primer' followed by doxycycline as a definitive sclerosant (video 1). This technique emphasizes meticulous backtable preparation and effective use of ultrasound and fluoroscopy to minimize complications. neurintsurg;15/9/931/V1F1V1Video 1 .

Intermediate-porosity stent for coil-reconstruction of mixed saccular-fusiform basilar trunk aneurysm.

Vertebrobasilar junction and basilar trunk aneurysms are extremely difficult to treat, with significant morbidity associated with bypass-trapping procedures. As a result, endovascular techniques including flow diversion and stent-assisted coil embolization have become the mainstay of treatment.1-3 Traditional flow diverters pose risk of occlusion of basilar perforator arteries while traditional stents used as adjuncts for coil-embolization often have high porosity and cannot function as flow diverters. On the other hand, the LVIS stent uniquely provides more porosity than other flow diverters,4,5 allowing patency of perforators while also being amenable to stent-assisted coiling. We present a case of a mixed saccular and fusiform basilar trunk aneurysm that underwent LVIS stent-assisted coil embolization. Using bifemoral access with triaxial systems, one microcatheter was placed in the aneurysm sac and another was used to deploy a stent from the basilar apex into the right vertebral artery. A durable angiographic outcome was observed at 9 months.

Staged stent-assisted, transcirculatory coiling of partially-thrombosed, mixed saccular and fusiform SCA aneurysm.

SCA aneurysms are rare, making data on their management sparse compared to other posterior circulation aneurysms. While saccular aneurysms at the SCA origin can be treated with primary coiling or surgical clipping, fusiform and distal SCA aneurysms often require endovascular techniques such as stent-assisted coil embolization or parent vessel occlusion. We present a case of a mixed saccular/fusiform SCA aneurysm that underwent staged stent-assisted coil embolization. A right SCA stent was placed in the first stage. Given the acute angle between the BA and the SCA, microcatheter access and stent placement proved challenging. The decision was made to allow the stent to endothelialize and return in a staged fashion to perform a trans-radial, transcirculatory (trans-left PCoA, trans-left PCA) coil embolization. This provided a straight course between the left P1 segment and the right SCA origin, allowing easy microcatheter navigation through the stent and into the aneurysm for coil embolization.

Geometric and Morphologic Features of Ruptured Intracranial Aneurysms Associated with Methamphetamine Use.

BACKGROUND: Methamphetamine (MA) use is associated with poor outcomes after aneurysmal subarachnoid hemorrhage (aSAH). MA exerts both hemodynamic and inflammatory effects, but whether these manifest with altered intracranial aneurysm (IA) remodeling is unknown. The objective of this study was to compare IA geometric and morphologic features in patients with and without MA detected on urine toxicology (Utox) at presentation. METHODS: We retrospectively reviewed 160 consecutive patients with SAH and Utox at time of admission. Geometric-morphologic IA characteristics were assessed by blinded neuroradiologists. Studied features were maximum sac diameter, location, size, ellipsoid volume, aspect ratio, size ratio, volume: neck ratio, dome: neck ratio, bottleneck factor, morphology (saccular, fusiform/dissecting, blister, mycotic), and presence of bleb, vasculopathy, or additional unruptured IA. RESULTS: Of 139/160 patients with aSAH, 23/139 (16.5%) were Utox MA+. There was no difference in aneurysm subtype frequency, presence of bleb, vasculopathy, or presence of an additional (unruptured) aneurysm with a trend toward posterior circulation location and higher Hunt and Hess grade (P = 0.09 for both) in the MA+ group. Maximum IA sac diameter, ellipsoid volume, dome-neck ratio, and size ratio were similar between groups. Only the aspect ratio (AR) differed between groups (MA+ = 2.20 vs. MA- = 1.74, P = 0.02). The AR remained a significant predictor of Utox MA+ in a multiple logistic regression analysis (odds ratio 1.87, 95% confidence interval 1.06-3.39). CONCLUSIONS: Active use of methamphetamine is independently associated with larger AR in patients with ruptured IA. This may indicate hazardous remodeling due to hemodynamic and/or inflammatory changes.

Pharyngo-tympano-stapedial middle meningeal artery variant supply to a falcotentorial dural arteriovenous fistula.

The pharyngo-tympano-stapedial middle meningeal artery (PTS-MMA) variant has been described in one case report and never in the setting of arterial supply to a dural arteriovenous fistula, to our knowledge. We report the case of a middle-aged patient with severe, daily headache who presented to our institution for angiography and treatment. CT angiography and MRI demonstrated an enlarged left middle meningeal artery coursing to a large venous varix in the falcotentorial region. Dural arteriovenous fistula was confirmed by subsequent cerebral angiography. Endovascular treatment was performed but without complete obliteration of the fistula. Follow-up angiography demonstrated parasitized arterial supply from a right middle meningeal artery arising from the proximal cervical internal carotid artery coursing through the middle ear consistent with a PTS-MMA variant. The fistula was then treated surgically without recurrence at the 6-month follow-up.

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.

Brain herniation (encephalocele) into arachnoid granulations: prevalence and association with pulsatile tinnitus and idiopathic intracranial hypertension.

PURPOSE: Brain herniation into arachnoid granulations (BHAG) of the dural venous sinuses is a recently described finding of uncertain etiology. The purpose of this study was to investigate the prevalence of BHAG in a cohort of patients with pulsatile tinnitus (PT) and to clarify the physiologic and clinical implications of these lesions. METHODS: The imaging and charts of consecutive PT patients were retrospectively reviewed. All patients were examined with MRI including pre- and post-contrast T1- and T2-weighted sequences. Images were reviewed separately by three blinded neuroradiologists to identify the presence of BHAG. Their location, signal intensity, size, presence of arachnoid granulation, and associated dural venous sinus stenosis were documented. Clinical records were further reviewed for idiopathic intracranial hypertension, history of prior lumbar puncture, and opening pressure. RESULTS: Two hundred sixty-two consecutive PT patients over a 4-year period met inclusion criteria. PT patients with BHAG were significantly more likely to have idiopathic intracranial hypertension than PT patients without BHAG (OR 4.2, CI 1.5-12, p = 0.006). Sixteen out of 262 (6%) patients were found to have 18 BHAG. Eleven out of 16 (69%) patients had unilateral temporal or occipital lobe herniations located in the transverse sinus or the transverse-sigmoid junction. Three out of 16 (19%) patients had unilateral cerebellar herniations and 2/16 (13%) patients had bilateral BHAG. CONCLUSION: In patients with PT, BHAG is a prevalent MRI finding that is strongly associated with the clinical diagnosis of IIH. The pathogenesis of BHAG remains uncertain, but recognition should prompt comprehensive evaluation for IIH.

Eptifibatide bridging therapy for staged carotid artery stenting and cardiac surgery: Safety and feasibility.

BACKGROUND: Prophylactic carotid artery stenting (CAS) is an effective strategy to reduce perioperative stroke in patients with severe carotid stenosis who require cardiothoracic surgery (CTS). Staging both procedures (CAS-CTS) during a single hospitalization presents conflicting demands for antiplatelet therapy and the optimal pharmacologic strategy between procedures is not established. The purpose of this study is to present our initial experience with a "bridging" protocol for staged CAS-CTS. METHODS: A retrospective review of staged CAS-CTS procedures at a single referral center was performed. All patients had multivessel coronary and/or valvular disease and severe carotid stenosis (>70%). Patients not previously on aspirin were also started on aspirin prior to surgery, followed by eptifibatide during CAS (intraprocedural bolus followed by post-procedural infusion which was continued until the morning of surgery). Pre- and perioperative (30 days) neurologic morbidity and mortality was the primary endpoint. RESULTS: 11 CAS procedures were performed in 10 patients using the protocol. The median duration of eptifibatide bridge therapy was 36 h (range 24-288 h). There was one minor bleeding complication (1/11, 9.1%) and no major bleeding complications during the bridging and post-operative period. There was one post-operative, non-neurologic death and zero perioperative ischemic strokes. CONCLUSIONS: For patients undergoing staged CAS-CTS, Eptifibatide bridging therapy is a viable temporary antiplatelet strategy with a favorable safety profile. This strategy enables a flexible range of time-intervals between procedures.

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.

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.