Atlanto-Occipital Decompression of Vertebral Artery for a Variant of Bow Hunter's Syndrome: 2-Dimensional Operative Video.

Rotational vertebral artery (VA) occlusion syndrome, also known as bow hunter's syndrome, is an uncommon variant of vertebrobasilar insufficiency typically occurring with head rotation.1-3 The most common presenting symptom is dizziness (76.8%), followed by visual abnormalities and syncope (50.4% and 40.4%, respectively).2 Osteophytic compression due to spinal spondylosis has been shown to be the most common etiology (46.2%), with other factors, such as a fibrous band, muscular compression, or spinal instability, being documented.1,2 Treatment is dependent on the level and site of VA compression with anterior, anterolateral, or posterior approaches being described.1,4 We present the case of a 72-yr-old male with osteophytic compression of the V3 segment of the vertebral artery at the occipital-cervical junction. The patient underwent a C1 hemilaminectomy and removal of osteophytic compression from the occipital-cervical joint. The patient had complete resolution of compression of his vertebral artery on postoperative imaging and remained neurologically intact following the procedure. We review the literature on this topic, the technical nuances of the procedure performed, and review the different treatment modalities available for this rare condition.1-11 The patient consented to the procedure and to publication of their image.

COVID-19 Impact on Stroke Presentations.

BACKGROUND: As Covid-19 evolved into a world-wide pandemic, hospitals reported marked declines in strokes, only to be followed by reports of increased numbers of young people presenting with large-vessel occlusions. We reviewed our patient data-base to determine if similar or other novel trends were present. RESULTS: Our Thrombectomy Stroke Center experienced marked declines in ED visits from 2,349 in early March to 1,178 in late April, stroke alerts dropped from 34 to 14 during the same period. Average monthly stroke admissions dropped from 34 in 2019 to 23 in 2020. Nonetheless, in March, we had 12 patients eligible for tPA, which is twice the typical caseload and was unexpected given the low overall stroke presentations. Although the neurointervention caseload was low, the patients were significantly younger. Of the acute intervention patients in March, 5 of the 12 patients were ≤ 60 years old, and two were in their 30's. These trends are similar to those reported elsewhere but were highly unusual for our center as our catchment area is predominantly Caucasian with 34 % of the population > 65 years of age. CONCLUSIONS: Even in low risk centers Covid-19 will likely impart unique stroke presentations. It will be imperative to determine the mechanisms responsible for these changes so we can institute effective strategies for optimal stroke prevention as well as maintain timely acute interventions.

Relationship between weather conditions and admissions for ischemic stroke and subarachnoid hemorrhage.

AIM: To assess impacts of different weather conditions on hospitalizations of patients with ischemic strokes and subarachnoid hemorrhages (SAH) in South Florida. METHODS: Diagnostic data of patients with spontaneous SAH and strokes were recorded between June 2010 and July 2013. Daily synchronous forecast charts were collected from the National Weather Service and the whole data were matched prospectively. The incidence rate ratio (IRR) was calculated. RESULTS: Increased incidence rate of ischemic stroke was consistent with the daily lowest and highest air pressure (IRR 1.03, P=0.128 and IRR 0.98, P=0.380, respectively), highest air temperature (IRR 0.99, P=0.375), and presence of hurricanes or storms (IRR 0.65, P=0.054). Increased incidence of SAH cases was consistent with daily lowest and highest air pressure (IRR 0.87, P<0.001 and IRR 1.08, P=0.019, respectively) and highest air temperature (IRR 0.98, P<0.001). Presence of hurricanes and/or tropical storms did not influence the frequency of SAH. We found no relationship between the presence of fronts and the admissions for ischemic stroke or SAH. CONCLUSION: Higher number of ischemic stroke and SAH cases can be expected with the daily lowest and highest air pressure, highest air temperature. Presence of hurricanes or tropical storms increased the risk of ischemic stroke but not the SAH. These findings can help to develop preventive health plans for cerebrovascular diseases.

Aspiration Thrombectomy After Intravenous Alteplase Versus Intravenous Alteplase Alone.

BACKGROUND AND PURPOSE: Thrombectomy, primarily with stent retrievers with or without adjunctive aspiration, provided clinical benefit across multiple prospective randomized trials. Whether this benefit is exclusive to stent retrievers is unclear. METHODS: THERAPY (The Randomized, Concurrent Controlled Trial to Assess the Penumbra System's Safety and Effectiveness in the Treatment of Acute Stroke; NCT01429350) was an international, multicenter, prospective, randomized (1:1), open label, blinded end point evaluation, concurrent controlled clinical trial of aspiration thrombectomy after intravenous alteplase (IAT) administration compared with intravenous-alteplase alone in patients with large vessel ischemic stroke because of a thrombus length of ≥8 mm. The primary efficacy end point was the percent of patients achieving independence at 90 days (modified Rankin Scale score, 0-2; intention-to-treat analysis). The primary safety end point was the rate of severe adverse events (SAEs) by 90 days (as treated analysis). Patients were randomized 1:1 across 36 centers in 2 countries (United States and Germany). RESULTS: Enrollment was halted after 108 (55 IAT and 53 intravenous) patients (of 692 planned) because of external evidence of the added benefit of endovascular therapy to intravenous-alteplase alone. Functional independence was achieved in 38% IAT and 30% intravenous intention-to-treat groups (P=0.52). Intention-to-treat ordinal modified Rankin Scale odds ratio was 1.76 (95% confidence interval, 0.86-3.59; P=0.12) in favor of IAT. Secondary efficacy analyses all demonstrated a consistent direction of effect toward benefit of IAT. No differences in symptomatic intracranial hemorrhage rates (9.3% IAT versus 9.7% intravenous, P=1.0) or 90-day mortality (IAT: 12% versus intravenous: 23.9%, P=0.18) were observed. CONCLUSIONS: THERAPY did not achieve its primary end point in this underpowered sample. Directions of effect for all prespecified outcomes were both internally and externally consistent toward benefit. It is possible that an alternate method of thrombectomy, primary aspiration, will benefit selected patients harboring large vessel occlusions. Further study on this topic is indicated. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01429350.

The SPEED study: initial clinical evaluation of the Penumbra novel 054 Reperfusion Catheter.

BACKGROUND AND PURPOSE: Revascularization of acute ischemic stroke from a large vessel occlusion continues to be a challenge with current thrombectomy devices. The purpose of the SPEED study was to report the safety and effectiveness of the Penumbra 054 Reperfusion Catheter System in revascularizing large vessel occlusions. METHODS: In this retrospective multicenter study, data were collected from patients with angiographic evidence of large vessel occlusion treated with the Penumbra 054 device as the intended primary therapy. Clinical outcome data were collected with 90-day follow-up and the results were compared with those from the Penumbra Pivotal trial. RESULTS: Eighty-seven target vessels in 86 consecutive patients treated with the Penumbra 054 device were included. The Thrombolysis In Myocardial Infarction (TIMI) 2 or 3 revascularization rate was 91% compared with a reported 82% in the Penumbra Pivotal trial. This was accomplished in a median time of 20 min compared with 45 min in the Penumbra Pivotal trial (p<0.0001). Eighteen (21%) patients experienced an intracranial hemorrhage of which 12 (14%) were symptomatic. Good neurologic outcome (modified Rankin scores ≤ 2) at 90-day follow-up was achieved in 34.9% of patients compared with 25% reported in the Penumbra Pivotal trial. All-cause mortality was 25.6%. CONCLUSIONS: These results suggest that the Penumbra 054 is a fast, safe and effective revascularization tool for patients experiencing ischemic stroke secondary to large vessel occlusive disease. Improvements in speed and effectiveness of revascularization probably contributed to improved outcomes.

1-hexyl n-cyanoacrylate compound (Neucrylate™ AN), a new berry aneurysm treatment. II. Rabbit implant studies: technique and histology.

INTRODUCTION: Following satisfactory benchtop testing of a new liquid embolic agent, animal implant studies were performed. MATERIALS AND METHOD: Elastase aneurysms were created in the right common carotid artery of New Zealand rabbits under approved institutional guidelines. Using direct fluoroscopic control and commercially available microcatheters, the device was introduced into the aneurysms. At 2 months, 12 months and 24 months, follow-up angiography was performed and analyzed. The animals were sacrificed, the brachiocephalic arteries were explanted and fixed, and the histologic appearance of the treated aneurysms was evaluated. RESULTS: The Neucrylate polymerized into an open pore elastic sponge. The open pores permitted fibrous tissue ingrowth. By 2 months, all of the aneurysm necks had been covered by fibrous tissue and a neointima. Two of the aneurysms originally inadequately filled allowed opportunity for retreatment. The reactive change within the aneurysms demonstrated fibroblastic proliferation, collagen and some giant cells but no vascular necrosis. Results at 2 months, 12 months and 24 months were for all practical purposes similar. CONCLUSION: The lack of necrosis, the mild inflammatory response and the permanence of the implant are interesting in a cyanoacrylate based embolic agent, especially in light of the experience with lower chain homologs and other liquid embolic agents.

Neurological deficits associated with the elastase-induced aneurysm model in rabbits.

OBJECTIVE: Although the rabbit elastase-induced aneurysm model is currently used widely for endovascular research and device testing, procedural causes leading to animal morbidity and mortality have not yet been clearly described. We conducted a retrospective study to analyse factors contributing to neurological deficits in rabbits that underwent the elastase-induced aneurysm creation procedure at our research center from 2002 to 2005 in order to improve the technique and reduce procedure-related morbidity and mortality. METHODS: A total sample of 38 animals that underwent the procedure under the same conditions was analysed in two groups: animals that presented neurological deficits (ND, n=15) and animals that were neurological deficit free (NDF, n=23). Data were collected by reviewing the animal records and radiographic images from the procedures. Statistical analyses using the Mann-Whitney test, unpaired t-test with Welch correction and Fisher's exact tests were performed to compare the two groups based on variables associated with endothelial injury and activation of the coagulation cascade. RESULTS: The variables of animal weight (signifying state of health of the animal), total procedure time, total balloon occlusion time and clot formation were found to be significantly and/or very significantly correlated to ND presentation. DISCUSSION: Successful creation of the rabbit elastase-induced aneurysm model depends on careful control over several technical details. Important variables governing outcome have been identified here. A specific, improved endovascular arrangement that facilitates maneuvering of the devices and reduces the risk of air emboli is presented.

Angiographic assessment of the performance of flow divertors to treat cerebral aneurysms.

Past clinical and experimental evidence suggests that cerebral aneurysms can be successfully excluded from the circulation solely by the endovascular placement of a flow diverting device across the aneurysm neck. These devices promote intraaneurysmal flow stasis and concomitant thrombosis by redirecting flow away from the aneurysm. To comprehensively test the efficacy of such flow divertors, we are implanting devices with three different porosities in a large cohort of elastase-induced aneurysms in rabbits. Treatment efficacy is quantified by a mathematical model that is fit to aneurysmal angiographic contrast washout curves. Results from three animals implanted with different device porosities are presented here. The model competently captures the behavior of the aneurysmal washout curves and provides reliable indices of device efficacy. Preliminary analysis indicates that immediately after implantation, the device with medium porosity performs better than the devices with lower and higher porosities.

Morphology of elastase-induced cerebral aneurysm model in rabbit and rapid prototyping of elastomeric transparent replicas.

In this work, we describe a methodology to fabricate transparent elastomeric vascular replicas using rapid prototyping techniques. First, the three-dimensional morphology of an elastase-induced aneurysm model in rabbit is acquired. The morphology is reconstructed from in vivo rotational angiography and it is compared with three-dimensional reconstructions obtained by computerized tomography and magnetic resonance imaging of an intraluminal arterial cast that was obtained from the same animal at sacrifice. Results show that resolution of the imaging modality strongly influences the level of detail, such as small side branches, in the final reconstruction. We developed an average morphology model for elastase-induced aneurysms in rabbits including the surrounding vasculature and describe a method for rapid prototyping of vascular models from the three-dimensional morphology. Our replicas can be manufactured in a short period of time and the final product is optically clear. In addition, the elasticity of the models can be controlled to represent arterial elasticity, which makes them ideal for optical investigations of detailed flow dynamics using measurement tools such as particle image velocimetry.

Contrast injection via the central artery of the left ear in rabbits: a new technique to simplify follow-up studies.

Our goal was to establish a contrast injection technique that uses the unique vascular anatomy of the rabbit ear to spare the valuable femoral artery access sites. The central artery of the left ear was cannulated. Contrast injected in a retrograde fashion opacified the right brachiocephalic artery and its branches. The technique can be used in rabbits with the usual bovine-type left common carotid artery origin.

Functional angiography.

The discovery of X-rays over a century ago enabled noninvasive examination of the human body. Contrast agents that enhanced X-ray images were soon developed that advanced angiology by allowing exploration of the vascular tree. Starting as a diagnostic tool, angiography underwent technological transformations over the last century and became a basis for interventional therapy as well. Initially a static two-dimensional record of the vasculature on screen films, angiography has evolved to real-time two-dimensional display of the vasculature on television monitors, three-dimensional reconstruction from computerized tomographic (CT) scans, and, more recently, three-dimensional cone-beam reconstruction. Cinematographic angiography is referred to as dynamic angiography in current terminology, but it essentially provides no more than images of vascular structures and changes therein. Although dynamic angiography has facilitated advances in image-guided interventions, the evaluation of blood flow rate, or perfusion, and blood flow velocity using angiography remains elusive. Many lines of research have been pursued toward enabling such evaluations, but none have found their way into clinical practice. This article reviews angiographic flow assessment methods attempted over the past several decades and explores some new avenues that may facilitate the transfer of such methods into the clinical practice of diagnostic and interventional angiography and, eventually, contribute to better patient care.

Hemodynamics of carotid artery atherosclerotic occlusive disease.

Hemodynamic mechanisms for the initiation and progression of carotid bifurcation atherosclerotic occlusive disease have been extensively researched during the past few decades. Attention has focused on the carotid bulb, or sinus, where most atherosclerotic plaques are found. Herein, the authors review the seminal works that have led to an understanding of not only complex local hemodynamics but also the elicited specific biologic response. In addition, new analysis of the age-dependent morphologic maturation of the human carotid bifurcation is unveiled. Understanding the role of hemodynamics in atherogenesis may lead to the improvement of minimally invasive endovascular therapy and noninvasive strategies.

Vessel size measurements in angiograms: manual measurements.

Vessel size measurement is perhaps the most often performed quantitative analysis in diagnostic and interventional angiography. Although automated vessel sizing techniques are generally considered to have good accuracy and precision, we have observed that clinicians rarely use these techniques in standard clinical practice, choosing to indicate the edges of vessels and catheters to determine sizes and calibrate magnifications, i.e., manual measurements. Thus, we undertook an investigation of the accuracy and precision of vessel sizes calculated from manually indicated edges of vessels. Manual measurements were performed by three neuroradiologists and three physicists. Vessel sizes ranged from 0.1-3.0 mm in simulation studies and 0.3-6.4 mm in phantom studies. Simulation resolution functions had full-widths-at-half-maximum (FWHM) ranging from 0.0 to 0.5 mm. Phantom studies were performed with 4.5 in., 6 in., 9 in., and 12 in. image intensifier modes, magnification factor = 1, with and without zooming. The accuracy and reproducibility of the measurements ranged from 0.1 to 0.2 mm, depending on vessel size, resolution, and pixel size, and zoom. These results indicate that manual measurements may have accuracies comparable to automated techniques for vessels with sizes greater than 1 mm, but that automated techniques which take into account the resolution function should be used for vessels with sizes smaller than 1 mm.

Vessel size measurements in angiograms: a comparison of techniques.

As interventional procedures become more complicated, the need for accurate quantitative vascular information increases. In response to this need, many commercial vendors provide techniques for measurement of vessel sizes, usually based on derivative techniques. In this study, we investigate the accuracy of several techniques used in the measurement of vessel size. Simulated images of vessels having circular cross sections were generated and convolved with various focal spot distributions taking into account the magnification. These vessel images were then convolved with Gaussian image detector line spread functions (LSFs). Additionally, images of a phantom containing vessels with a range of diameters were acquired for the 4.5", 6", 9", and 12" modes of an image intensifier-TV (II-TV) system. Vessel sizes in the images were determined using a first-derivative technique, a second-derivative technique, a linear combination of these two measured sizes, a thresholding technique, a densitometric technique, and a model-based technique. For the same focal spot size, the shape of the focal spot distribution does not affect measured vessel sizes except at large magnifications. For vessels with diameters larger than the full-width-at-half-maximum (FWHM) of the LSF, accurate vessel sizes (errors approximately 0.1 mm) could be obtained by using an average of sizes determined by the first and second derivatives. For vessels with diameters smaller than the FWHM of the LSF, the densitometric and model-based techniques can provide accurate vessel sizes when these techniques are properly calibrated.

Improved method of magnification factor calculation for the angiographic measurement of neurovascular lesion dimensions.

Accurately evaluating the size of a neurovascular lesion is essential for properly devising treatment strategies. The magnification factor must be considered in order to measure the dimension of a lesion from an angiogram. Although a method to calculate the magnification of the lesion by linear interpolation of the measurable magnification factors of two markers has been in use, this paper shows that it can be inaccurate. By deriving the exact formula for calculating the magnification factor at the level of the lesion, the error generated by the linear interpolation of magnification factor has been evaluated. This error was found to depend on source-to-skin distance (SSD), the location of the lesion in the head, and the head size. The closer the head is to the focal spot and the nearer the lesion is to the center of the head, the larger is the error. Since clinicians tend to use high geometric magnification (i.e., small SSD) in interventional procedures, there exists a possible consequential error of more than 3% in lesion sizing if the linear-interpolation calculation method is used. It is thus recommended that the exact formula derived here be used to calculate the magnification factor to improve accuracy.