The carotid artery is unique; it is the only vessel to bifurcate into a bulb larger than itself. The history of its anatomic description, understanding of its pathophysiology and evolution of its imaging are relevant to current controversies regarding measurement of stenosis, surgical/endovascular therapies and medical management of carotid stenosis in stroke prevention. Treatment decisions on millions of symptomatic and asymptomatic patients are routinely based on information from clinical trials from over 30 years ago. This article briefly summarizes the highlights of past research in key areas and discuss how they led to current challenges of diagnosis and treatment.

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Increasing evidence indicates that circadian and diurnal rhythms robustly influence stroke onset, mechanism, progression, recovery, and response to therapy in human patients. Pioneering initial investigations yielded important insights but were often single-center series, used basic imaging approaches, and used conflicting definitions of key data elements, including what constitutes daytime versus nighttime. Contemporary methodologic advances in human neurovascular investigation have the potential to substantially increase understanding, including the use of large multicenter and national data registries, detailed clinical trial data sets, analysis guided by individual patient chronotype, and multimodal computed tomographic and magnetic resonance imaging. To fully harness the power of these approaches to enhance pathophysiologic knowledge, an important foundational step is to develop standardized definitions and coding guides for data collection, permitting rapid aggregation of data acquired in different studies, and ensuring a common framework for analysis. To meet this need, the Leducq Consortium International pour la Recherche Circadienne sur l’AVC (CIRCA) convened a Consensus Statement Working Group of leading international researchers in cerebrovascular and circadian/diurnal biology. Using an iterative, mixed-methods process, the working group developed 79 data standards, including 48 common data elements (23 new and 25 modified/unmodified from existing common data elements), 14 intervals for time-anchored analyses of different granularity, and 7 formal, validated scales. This portfolio of standardized data structures is now available to assist researchers in the design, implementation, aggregation, and interpretation of clinical, imaging, and population research related to the influence of human circadian/diurnal biology upon ischemic and hemorrhagic stroke.

Background and Purpose: Cerebral emboli are generated by every step of standard carotid angioplasty and stenting. Primary carotid stenting (PCS) is a technique in which the use of balloon angioplasty (BA) is minimized to decrease the embolic load. The primary aim of this study is to establish the number of emboli generated by each step of primary stenting and determine the relationship to new diffusion (DWI) lesions on subsequent magnetic resonance imaging (MRI). Methods: Eighty-five patients with severe, symptomatic carotid stenosis were prospectively recruited and underwent carotid stenting. Intraoperative transcranial Doppler was performed in 77 patients. The number and size of microemboli for each of seven procedural steps were recorded. Correlation was made with the number and location of new DWI lesions. Results: PCS was performed in 73 patients. BA was required in 12 patients. The mean number of microemboli was 114, and most microemboli were generated by stent deployment, followed by BA. Balloon techniques generated significantly more emboli than primary stenting (p = 0.017). There was a significant relationship between total microemboli and new DWI lesions (p = 0.009), and between new DWI lesions in multiple territories and the severity of pretreatment stenosis (p = 0.002). Conclusions: During PCS, more emboli are generated by stent deployment than during any other stage of the procedure. When BA is necessary, more malignant emboli are generated but total emboli are unchanged and there is no difference in new diffusion lesions on MRI. PCS is safe and is not inferior to historical controls for the generation of new DWI lesions.

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Background: There is an association between anterior cerebral artery vessel asymmetry and anterior communicating artery aneurysm, presumably based on flow dynamics. The purpose of this study is to investigate the potential relationship between aortic arch branching patterns and incidence of intracranial aneurysm. Methods: This study included patients scanned over 1 year at our tertiary care center who underwent high-resolution imaging (computed tomography angiography or digital subtracted angiogram) of the head and neck arteries, aortic arch, and superior mediastinum. Exclusion criteria included patients with suboptimal images. Patient age, gender, aortic arch branching pattern, and the presence, location, and number of aneurysms were documented. Results: Among the 1082 patients analyzed, 250 (23%) patients had a variant aortic arch branching pattern, 22 (8.8%) of whom had aneurysms. There were 104 patients with 126 aneurysms, with majority of patients with normal aortic arch branching pattern (n = 82, 79%). The most common variant was a common origin of the left common carotid artery and brachiocephalic trunk with or without direct origin of the left vertebral artery. Twenty-two patients with aneurysms had an aberrant aortic arch (21%), compared to 232 patients without an aneurysm (24%). Fischer exact test showed no statistically significant difference between the incidence of aneurysm with different aortic arch variant groups (two-tailed p-value = 0.715). Conclusion: To our knowledge, this is the first study to examine the association between aortic arch branching patterns and incidence of intracranial aneurysm. No significant association was found between aortic arch branching pattern and the incidence of intracranial aneurysm.

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ABSTRACT: Objectives: The COVID-19 pandemic has resulted in huge disruption to healthcare delivery worldwide. There is a need to balance the urgent needs of the neurovascular patient population with the desire to preserve critical inpatient hospital capacity. It is incumbent on neurointerventionalists to advocate for their patients to minimise future disability. Patients still require semiurgent carotid revascularisation after ischaemic embolic events. We present a review of a novel protocol for expediting patient flow through the carotid stenting process, in accordance with government directives to minimise nonessential inpatient admissions, ensure its efficacy, and evaluate its safety. We also evaluate the literature regarding complications with attention to the timing of these related to the procedure. Methods: A retrospective review of 45 consecutive carotid stenting cases performed at London Health Sciences Centre between March 2020 and March 2021 for symptomatic extracranial internal carotid artery stenosis utilising a default same-day discharge policy was performed. Complications were plotted as a function of time. Results: Twenty-four patients underwent carotid artery stenting with same-day discharge and 21 patients underwent stenting with an overnight inpatient stay. A single stent occlusion occurred 27 h post stenting. Conclusion: Simple modification of protocol for symptomatic carotid artery stenting during the COVID-19 outbreak with radial access as first approach appears to provide safe, efficacious care.

ABSTRACT: The goal of effective neuroprotection in acute ischemic stroke remains elusive. Despite decades of experimental preclinical and clinical experience with innumerable agents, no strategy has proven to be beneficial in humans. As endovascular therapies mature and approach the limits of speed and efficacy, neuroprotection will become the next frontier of acute stroke care. This review will briefly summarize the history, preclinical and clinical triumphs and failures, and future directions of cerebral neuroprotection.

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Interventional neuroradiology (INR) has evolved from a hybrid mixture of daring radiologists and iconoclastic neurosurgeons into a multidisciplinary specialty, which has become indispensable for cerebrovascular and neurological centers worldwide. This manuscript traces the origins of INR and describes its evolution to the present day. The focus will be on cerebrovascular disorders including aneurysms, stroke, brain arteriovenous malformations, dural arteriovenous fistulae, and atherosclerotic disease, both intra- and extracranial. Also discussed are cerebral vasospasm, venolymphatic malformations of the head and neck, tumor embolization, idiopathic intracranial hypertension, inferior petrosal venous sinus sampling for Cushing's disease, and spinal interventions. Pediatric INR has not been included and deserves a separate, dedicated review.

A 56-year-old woman with a history of a subtotally resected left suprasellar WHO Grade 1 meningioma reported increasing left-sided retroorbital headaches. Head MRI showed progression of residual left cavernous sinus tumor. Radiation treatment was delivered, and she received 50.4 Gy over 28 fractions to a highly conformal volume using volumetric modulated arc therapy with multiple noncoplanar arcs (Fig. 1A). Two days after her 28th radiation treatment she presented with bizarre behavior, followed by seizures leading to intubation. Head MRI revealed diffusion restriction in the mesiotemporal lobes. There was no appreciable reduction in the size of the meningioma postradiation. Cerebrospinal fluid examination showed mildly elevated protein, a normal white blood cell count, and no oligoclonal bands. Infectious testing was negative for HIV, syphilis, Lyme, Whipple disease, flaviviruses, herpes simplex virus (HSV), varicella zoster virus, and enterovirus. Antibody testing was negative for antinuclear antibodies, antiglutamic acid decarboxylase antibodies, antithyroid antibodies, anti–N-methyl-D-aspartate receptor (NMDAR) antibodies, anti–voltage-gated potassium channel (VGKC) complex antibodies, and antibodies to Hu, Yo, Ri, CV2, amphiphysin, and Ma2. Whole-body PET/CT was unremarkable. The patient received phenytoin and levetiracetam for seizure control, and completed a 3-week course of acyclovir without improvement. Methylprednisolone and intravenous immunoglobulin was administered for possible limbic encephalitis (LE). She was extubated but remained stuporous and was hypothermic. Repeat head MRI showed persistent T2-signal abnormality in the mesiotemporal lobes extending into the hypothalamus, and new gyriform enhancement involving the right more than left mesiotemporal lobes (Fig. 1, B and C). A right temporal lobe biopsy was performed, revealing a T-cell–predominant encephalitis with no microorganisms seen (Fig. 1, E-H). The patient had transient clinical improvement the month following immunotherapy, but 1 month after that she deteriorated and became comatose. Repeat head MRI showed worsening T2-signal abnormality and enhancement of the limbic structures. She received methylprednisolone, plasma exchange, and rituximab 4 months after the onset of her encephalopathy, and dramatically improved. She became awake and conversational, although her shortterm memory was poor. Follow-up assessment 1.5 years after disease onset confirmed sustained clinical neurologic improvement, and repeat head MRI at that time showed no progression of T2-signal abnormalities, predominantly right-sided temporal lobe encephalomalacia, and resolution of enhancement (Fig. 1D).

OBJECTIVEEndovascular approaches have evolved from a technique practiced at very few centers to a widely available option in the management of arteriovenous malformations (AVMs) of the central nervous system. Embolization can be employed as definitive therapy or as an adjunct to surgical excision. A wide variety of embolic agents have been successfully developed and used in the clinical setting. In addition to facilitating vascular occlusion, embolic agents induce a number of reactive and destructive changes in vessel walls and the surrounding tissue. However, studies examining the pathological changes induced by different embolic agents and varying times of exposure are scarce. The goal of the present study was to compare embolic agents and time of exposure on the pathology in excised specimens.METHODSThe records of the Department of Pathology at the London Health Sciences Centre were searched for embolized AVMs for the 35-year period 1980-2015. All cases were reevaluated for clinical and technical variables and standardized histopathological findings. Cases were grouped by embolic agent, volume of agent used, and time to excision.RESULTSA total of 101 specimens were identified. Embolic agents were invariably associated with a range of pathological findings, some of which may affect the integrity of vessel walls or the reestablishment of flow, thrombosis, acute and chronic inflammatory changes, angionecrosis, extravasation, and recanalization. The type of embolic agent did not predict differences in the incidence or severity of histopathological changes. Larger volumes of embolic agent were associated with a greater proportion of vessels containing embolic material. AVMs excised early (< 1 week postembolization) contained more acute vasculitis, while those excised later (≥ 1 week postembolization) were more likely to exhibit recanalization and foreign body giant cell infiltrates.CONCLUSIONSEmbolic agents induce a predictable range and temporal progression of pathological changes in cerebral AVMs. The embolic agents studied are indistinguishable in terms of the range and frequency of pathological reactions induced. Greater volumes of embolic agent are associated with more abundant agent within the lesion, but the proportion of vessels and vascular cross-sectional areas containing agent is small. Several changes are significantly associated with time postembolization. Acute vasculitis is a more common finding in the 1st week, while recanalization and foreign body-type granulomatous inflammation are more common at 1 week and beyond.

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Introduction Brain arteriovenous malformations are abnormal connections between arteries and veins without an intervening capillary bed. Endovascular glue embolization with N-butyl cyanoacrylate (NBCA) is an accepted form of treatment. The reported complication rates vary widely from 2% to 15%, and timing of polymerization appears to play a major role. Additionally, the interaction between NBCA and vessel surface as well as the presence of biological catalysts are poorly understood. Methods Polymerization time was measured for mixtures of Lipiodol/NBCA of 50/50, 70/30, and 60/40. The influence of pH, temperature, and the presence of biological catalysts on polymerization time was investigated. Contact angles were measured on polyvinyl alcohol cryogel (PVA-C), silicone, and endothelial surfaces in a submerged aqueous environment to assess physical surface interactions. High speed video analysis of glue injection through a microcatheter was performed to characterize simulated coaxial flow. Results NBCA polymerization rate increased with pH and temperature. A hydrophilic surface such as PVA-C was better than silicone at mimicking the physical properties of endothelium. Live endothelium provided a catalytic surface that at least doubled the rate of polymerization. Blood products further increased the polymerization rate in the following order (slowest to fastest): plasma, platelets, red blood cells (RBCs), and lysed RBCs. These factors could explain the discrepancy between in vitro and in vivo results reported in the current literature. High speed video analysis of NBCA injection showed dripping to jetting transition with significant wall effect which deviated from previous ideal assumptions. Conclusions The determinants of NBCA polymerization rate are multifactorial and dependent mainly on the presence of biological catalysts coupled with flow related wall interaction.

The objective of this paper was to report a rare complication of basilar artery (BA) tourniquet treatment of a giant basilar tip aneurysm, and to discuss possible causes for the formation of a de novo giant posterior cerebral artery (PCA) aneurysm. A 34-year-old woman underwent satisfactory treatment of a ruptured giant basilar bifurcation aneurysm by BA ligation (Drake tourniquet) in 1985. She presented 25 years later with a new aneurysm in the left PCA, successfully treated by coil embolization. To the authors' knowledge, this is the first case of de novo aneurysm formation on a PCA, and the first de novo aneurysm reported as a complication of BA ligation therapy by Drake tourniquet. Long-term follow-up is necessary in patients with treated cerebral aneurysms, particularly those occurring in young patients, those with multiple aneurysms, those with complex posterior circulation aneurysms, and those undergoing flow diversion or flow-altering therapies.