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Background and purpose Accurate and reliable detection of medium-vessel occlusions is important to establish the diagnosis of acute ischemic stroke and initiate appropriate treatment with intravenous thrombolysis or endovascular thrombectomy. However, medium-vessel occlusions are often challenging to detect, especially for unexperienced readers. We aimed to evaluate the accuracy and interrater agreement of the detection of medium-vessel occlusions using single-phase and multiphase CTA. Materials and methods Single-phase and multiphase CTA of 120 patients with acute ischemic stroke (20 with no occlusion, 44 with large-vessel occlusion, and 56 with medium-vessel occlusion in the anterior and posterior circulation) were assessed by 3 readers with varying levels of experience (session 1: single-phase CTA; session 2: multiphase CTA). Interrater agreement for occlusion type (large-vessel occlusion versus medium-vessel occlusion versus no occlusion) and for detailed occlusion sites was calculated using the Fleiss κ with 95% confidence intervals. Accuracy for the detection of medium-vessel occlusions was calculated for each reader using classification tables. Results Interrater agreement for occlusion type was moderate for single-phase CTA (κ = 0.58; 95% CI, 0.56-0.62) and almost perfect for multiphase CTA (κ = 0.81; 95% CI, 0.78-0.83). Interrater agreement for detailed occlusion sites was moderate for single-phase CTA (κ = 0.55; 95% CI, 0.53-0.56) and substantial for multiphase CTA (κ = 0.71; 95% CI, 0.67-0.74). On single-phase CTA, readers 1, 2, and 3 classified 33/56 (59%), 34/56 (61%), and 32/56 (57%) correctly as medium-vessel occlusions. On multiphase CTA, 48/56 (86%), 50/56 (89%), and 50/56 (89%) medium-vessel occlusions were classified correctly. Conclusions Interrater agreement for medium-vessel occlusions is moderate when using single-phase CTA and almost perfect with multiphase CTA. Detection accuracy is substantially higher with multiphase CTA compared with single-phase CTA, suggesting that multiphase CTA might be a valuable tool for assessment of medium-vessel occlusion stroke.

BACKGROUND AND PURPOSE: There is a paucity of evidence regarding the safety of endovascular treatment for patients with acute ischemic stroke due to primary medium-vessel occlusion. The aim of this study was to examine the willingness among stroke physicians to perform endovascular treatment in patients with mild-yet-disabling deficits due to medium-vessel occlusion. MATERIALS AND METHODS: In an international cross-sectional survey consisting of 7 primary medium-vessel occlusion case scenarios, participants were asked whether the presence of personally disabling deficits would influence their decision-making for endovascular treatment despite the patients having low NIHSS scores (100 endovascular treatments per year (risk ratio = 1.63; 95% CI, 1.22–2.17). CONCLUSIONS: The presence of a patient-relevant deficit in low-NIHSS acute ischemic stroke due to medium-vessel occlusion is an important factor for endovascular treatment decision-making. This may have relevance for the conduct and interpretation of low-NIHSS endovascular treatment in randomized trials.

BACKGROUND AND PURPOSE: Infarct volume is an important predictor of clinical outcome in acute stroke. We hypothesized that the association of infarct volume and clinical outcome changes with the magnitude of infarct size. MATERIALS AND METHODS: Data were derived from the Safety and Efficacy of Nerinetide in Subjects Undergoing Endovascular Thrombectomy for Stroke (ESCAPE-NA1) trial, in which patients with acute stroke with large-vessel occlusion were randomized to endovascular treatment plus either nerinetide or a placebo. Infarct volume was manually segmented on 24-hour noncontrast CT or DWI. The relationship between infarct volume and good outcome, defined as mRS 0–2 at 90 days, was plotted. Patients were categorized on the basis of visual grouping at the curve shoulders of the infarct volume/outcome plot. The relationship between infarct volume and adjusted probability of good outcome was fitted with linear or polynomial functions as appropriate in each group. RESULTS: We included 1099 individuals in the study. Median infarct volume at 24 hours was 24.9 mL (interquartile range [IQR] = 6.6–92.2 mL). On the basis of the infarct volume/outcome plot, 4 infarct volume groups were defined (IQR = 0–15 mL, 15.1–70 mL, 70.1–200 mL, >200 mL). Proportions of good outcome in the 4 groups were 359/431 (83.3%), 219/337 (65.0%), 71/201 (35.3%), and 16/130 (12.3%), respectively. In small infarcts (IQR = 0–15 mL), no relationship with outcome was appreciated. In patients with intermediate infarct volume (IQR = 15–200 mL), there was progressive importance of volume as an outcome predictor. In infarcts of > 200 mL, outcomes were overall poor. CONCLUSIONS: The relationship between infarct volume and clinical outcome varies nonlinearly with the magnitude of infarct size. Infarct volume was linearly associated with decreased chances of achieving good outcome in patients with moderate-to-large infarcts, but not in those with small infarcts. In very large infarcts, a near-deterministic association with poor outcome was seen.

A health care crisis such as the coronavirus disease 2019 (COVID-19) pandemic requires allocation of hospital staff and resources on short notice. Thus, new and sometimes less experienced team members might join the team to fill in the gaps. This scenario can be particularly challenging in endovascular stroke treatment, which is a highly specialized task that requires seamless cooperation of numerous health care workers across various specialties and professions. This document is intended for stroke teams who face the challenge of integrating new team members into endovascular stroke-treatment workflows during the COVID-19 pandemic or any other global health care emergency. It discusses the key strategies for smooth integration of new stroke-team members in a crisis situation: 1) transfer of key knowledge (simple take-home messages), 2) open communication and a nonjudgmental atmosphere, 3) strategic task assignment, and 4) graded learning and responsibility. While these 4 key principles should generally be followed in endovascular stroke treatment, they become even more important during health care emergencies such as the COVID-19 pandemic, when health care professionals have to take on new and additional roles and responsibilities in challenging working environments for which they were not specifically trained.

BACKGROUND AND PURPOSE: Endovascular therapy in acute ischemic stroke is rapidly evolving. We explored physicians’ treatment attitudes and practice in patients with acute ischemic stroke due to M2 occlusion, given the absence of Level-1 guidelines. MATERIALS AND METHODS: We conducted an international multidisciplinary survey among physicians involved in acute stroke care. Respondents were presented with 10 of 22 case scenarios (4 with proximal M2 occlusions and 1 with a small-branch M2 occlusion) and asked about their treatment approach under A) current local resources, and B) assumed ideal conditions (no monetary or infrastructural restraints). Overall treatment decisions were evaluated; subgroup analyses by physician and patient baseline characteristics were performed. RESULTS: A total of 607 physicians participated. Most of the respondents decided in favor of endovascular therapy in M2 occlusions, both under current local resources and assumed ideal conditions (65.4% versus 69.6%; P = .017). Under current local resources, older patient age (P

Various imaging protocols exist for the identification of vessel occlusion and assessment of collateral flow in acute stroke. CT perfusion is particularly popular because the color maps are a striking visual indicator of pathology. Multiphase CTA has similar diagnostic and prognostic ability but requires more expertise to interpret. This article presents a new multiphase CTA display format that incorporates vascular information from all phases of the multiphase CTA series in a single time-variant color map, thereby facilitating multiphase CTA interpretation, particularly for less experienced readers. Exemplary cases of multiphase CTA from this new display format are compared with conventional multiphase CTA, CT perfusion, and follow-up imaging to demonstrate how time-variant multiphase CTA color maps facilitate assessment of collateral flow, detection of distal and multiple intracranial occlusions, differentiation of pseudo-occlusion from real occlusion, and assessment of flow relevance of stenoses, ante- and retrograde flow patterns, and clot permeability.

BACKGROUND AND PURPOSE: Thrombus characteristics identified on non-contrast CT (NCCT) are potentially associated with recanalization with intravenous (IV) alteplase in patients with acute ischemic stroke (AIS). Our aim was to determine the best radiomics-based features of thrombus on NCCT and CT angiography associated with recanalization with IV alteplase in AIS patients and proximal intracranial thrombi. MATERIALS AND METHODS: With a nested case-control design, 67 patients with ICA/M1 MCA segment thrombus treated with IV alteplase were included in this analysis. Three hundred twenty-six radiomics features were extracted from each thrombus on both NCCT and CTA images. Linear discriminative analysis was applied to select features most strongly associated with early recanalization with IV alteplase. These features were then used to train a linear support vector machine classifier. Ten times 5-fold cross-validation was used to evaluate the accuracy of the trained classifier and the stability of the selected features. RESULTS: Receiver operating characteristic curves showed that thrombus radiomics features are predictive of early recanalization with IV alteplase. The combination of radiomics features from NCCT, CTA, and radiomics changes is best associated with early recanalization with IV alteplase (area under the curve = 0.85) and was significantly better than any single feature such as thrombus length (P < .001), volume (P < .001), and permeability as measured by mean attenuation increase (P < .001), maximum attenuation in CTA (P < .001), maximum attenuation increase (P < .001), and assessment of residual flow grade (P < .001). CONCLUSIONS: Thrombus radiomics features derived from NCCT and CTA are more predictive of recanalization with IV alteplase in patients with acute ischemic stroke with proximal occlusion than previously known thrombus imaging features such as length, volume, and permeability.

We read with great interest the article by Fasen et al,[1][1] which addresses an important and often underappreciated topic in radiology: diagnostic errors and, more specifically, missed large- and medium-vessel occlusions on CT angiography in patients with acute ischemic stroke. Little is known

BACKGROUND AND PURPOSE: The safety and efficacy of endovascular therapy for large-artery stroke in the extended time window is not yet well-established. We performed a subgroup analysis on subjects enrolled within an extended time window in the Endovascular Treatment for Small Core and Proximal Occlusion Ischemic Stroke (ESCAPE) trial. MATERIALS AND METHODS: Fifty-nine of 315 subjects (33 in the intervention group and 26 in the control group) were randomized in the ESCAPE trial between 5.5 and 12 hours after last seen healthy (likely to have groin puncture administered 6 hours after that). Treatment effect sizes for all relevant outcomes (90-day mRS shift, mRS 0–2, mRS 0–1, and 24-hour NIHSS scores and intracerebral hemorrhage) were reported using unadjusted and adjusted analyses. RESULTS: There was no evidence of treatment heterogeneity between subjects in the early and late windows. Treatment effect favoring intervention was seen across all clinical outcomes in the extended time window (absolute risk difference of 19.3% for mRS 0–2 at 90 days). There were more asymptomatic intracerebral hemorrhage events within the intervention arm (48.5% versus 11.5%, P = .004) but no difference in symptomatic intracerebral hemorrhage. CONCLUSIONS: Patients with an extended time window could potentially benefit from endovascular treatment. Ongoing randomized controlled trials using imaging to identify late presenters with favorable brain physiology will help cement the paradigm of using time windows to select the population for acute imaging and imaging to select individual patients for therapy.

The overwhelming benefit of endovascular therapy in patients with large-vessel occlusions suggests that more patients will be screened than treated. Some of those patients will be evaluated first at primary stroke centers; this type of evaluation calls for standardizing the imaging approach to minimize delays in assessing, transferring, and treating these patients. Here, we propose that CT angiography (performed at the same time as head CT) should be the minimum imaging approach for all patients with stroke with suspected large-vessel occlusion presenting to primary stroke centers. We discuss some of the implications of this approach and how to facilitate them.

BACKGROUND AND PURPOSE: Carotid webs may cause recurrent ischemic stroke. We describe the prevalence, demographics, clinical presentation, imaging features, histopathology, and stroke risk associated with this under-recognized lesion. MATERIALS AND METHODS: A carotid web was defined on CTA as a thin intraluminal filling defect along the posterior wall of the carotid bulb just beyond the carotid bifurcation on oblique sagittal section CTA that was seen as a septum on axial CTA. Using a prospective case series from April 2013 to April 2014, we describe the demographics, spectrum of imaging features on CTA, and histopathology of these carotid webs. From a retrospective analysis of patients at our center from May 2012 to April 2013 who had a baseline head and neck CTA followed by a brain MR imaging within 1–2 days of the CTA, we determine the period prevalence of carotid webs and the prevalence of ipsilateral stroke on imaging. RESULTS: In the prospective series, the mean age was 50 years (range, 41–55 years); 5/7 patients were women. Recurrent stroke was seen in 5/7 (71.4%) patients with the carotid web; time to recurrence ranged from 1 to 97 months. Histopathology suggested a high probability of fibromuscular dysplasia. In the retrospective series, carotid webs were seen in 7/576 patients for a hospital-based-period prevalence of 1.2% (95% CI, 0.4%–2.5%). Two of these 7 patients had acute stroke in the vascular territory of the carotid web. CONCLUSIONS: A carotid web may contribute to recurrent ischemic stroke in patients with no other determined stroke mechanism. Intimal variant fibromuscular dysplasia is the pathologic diagnosis in most cases. The prevalence of carotid web is low, while the optimal management strategy remains unknown.

BACKGROUND AND PURPOSE: Gadobutrol (Gadavist) and gadoteridol (ProHance) have similar macrocyclic molecular structures, but gadobutrol is formulated at a 2-fold higher (1 mol/L versus 0.5 mol/L) concentration. We sought to determine whether this difference impacts morphologic contrast-enhanced MR imaging. MATERIALS AND METHODS: Two hundred twenty-nine adult patients with suspected or known brain tumors underwent two 1.5T MR imaging examinations with gadoteridol or gadobutrol administered in randomized order at a dose of 0.1 mmol/kg of body weight. Imaging sequences and T1 postinjection timing were identical for both examinations. Three blinded readers evaluated images qualitatively and quantitatively for lesion detection and for accuracy in characterization of histologically confirmed brain tumors. Data were analyzed by using the Wilcoxon signed rank test, the McNemar test, and a mixed model. RESULTS: Two hundred nine patients successfully completed both examinations. No reader noted a significant qualitative or quantitative difference in lesion enhancement, extent, delineation, or internal morphology (P values = .69–1.00). One hundred thirty-nine patients had at least 1 histologically confirmed brain lesion. Two readers found no difference in the detection of patients with lesions (133/139 versus 135/139, P = .317; 137/139 versus 136/139, P = .564), while 1 reader found minimal differences in favor of gadoteridol (136/139 versus 132/139, P = .046). Similar findings were noted for the number of lesions detected and characterization of tumors (malignant/benign). Three-reader agreement for characterization was similar for gadobutrol (66.4% [κ = 0.43]) versus gadoteridol (70.3% [κ = 0.45]). There were no significant differences in the incidence of adverse events (P = .199). CONCLUSIONS: Gadoteridol and gadobutrol at 0.1 mmol/kg of body weight provide similar information for visualization and diagnosis of brain lesions. The 2-fold higher gadolinium concentration of gadobutrol provides no benefit for routine morphologic imaging.

BACKGROUND AND PURPOSE: Collateral status at baseline is an independent determinant of clinical outcome among patients with acute ischemic stroke. We sought to identify whether the association between recanalization after intra-arterial acute stroke therapy and favorable clinical response is modified by the presence of good collateral flow assessed on baseline CTA. MATERIALS AND METHODS: Data are from the Keimyung Stroke Registry, a prospective cohort study of patients with acute ischemic stroke from Daegu, South Korea. Patients with M1 segment MCA with or without intracranial ICA occlusions on baseline CTA from May 2004 to July 2009 who also had baseline MR imaging were included. Two readers blinded to all clinical information assessed baseline and follow-up imaging. Leptomeningeal collaterals on baseline CTA were assessed by consensus by use of the regional leptomeningeal score. RESULTS: Among 84 patients (mean age, 65.2 ± 13.2 years; median NIHSS score, 14; interquartile range, 8.5), median time from stroke onset to initial MR imaging was 164 minutes. TICI 2b–3 recanalization was achieved in 38.1% of patients and mRS 0–2 at 90 days in 35.8% of patients. In a multivariable model, the interaction between collateral status and recanalization was significant. Only patients with intermediate or good collaterals who recanalized showed a statistically significant association with good clinical outcome (rate ratio = 3.8; 95% CI, 1.2–12.1). Patients with good and intermediate collaterals who did not achieve recanalization and patients with poor collaterals, even if they achieved recanalization, did not do well. CONCLUSIONS: Patients with good or intermediate collaterals on CTA benefit from intra-arterial therapy, whereas patients with poor collaterals do not benefit from treatment.

BACKGROUND AND PURPOSE: Carotid revascularization procedures can be complicated by stroke. Additional disability adds to the already high costs of the procedure. To weigh the cost and benefit, we estimated the cost-utility of carotid angioplasty and stenting compared with carotid endarterectomy among patients with symptomatic carotid stenosis, with special emphasis on scenario analyses that would yield carotid angioplasty and stenting as the cost-effective alternative relative to carotid endarterectomy. MATERIALS AND METHODS: A cost-utility analysis from the perspective of the health system payer was performed by using a Markov analytic model. Clinical estimates were based on a meta-analysis. The procedural costs were derived from a microcosting data base. The costs for hospitalization and rehabilitation of patients with stroke were based on a Canadian multicenter study. Utilities were based on a randomized controlled trial. RESULTS: In the base case analysis, carotid angioplasty and stenting were more expensive (incremental cost of $6107) and had a lower utility (−0.12 quality-adjusted life years) than carotid endarterectomy. The results are sensitive to changes in the risk of clinical events and the relative risk of death and stroke. Carotid angioplasty and stenting were more economically attractive among high-risk surgical patients. For carotid angioplasty and stenting to become the preferred option, their costs would need to fall from more than $7300 to $4350 or less and the risks of the periprocedural and annual minor strokes would have to be equivalent to that of carotid endarterectomy. CONCLUSIONS: In the base case analysis, carotid angioplasty and stenting were associated with higher costs and lower utility compared with carotid endarterectomy for patients with symptomatic carotid stenosis. Carotid angioplasty and stenting were cost-effective for patients with high surgical risk.

BACKGROUND AND PURPOSE: Gadobenate dimeglumine has proved advantageous compared with other gadolinium-based contrast agents for contrast-enhanced brain MR imaging. Gadobutrol is a more highly concentrated agent (1.0 mol/L). This study intraindividually compared 0.1-mmol/kg doses of these agents for qualitative and quantitative evaluation of brain tumors. MATERIALS AND METHODS: Adult patients with suspected or known brain tumors underwent 2 identical MR imaging examinations at 1.5T, 1 with gadobenate dimeglumine and the other with gadobutrol, both at a dose of 0.1-mmol/kg body weight. The agents were injected in randomized order separated by 3–14 days. Imaging sequences and acquisition timing were identical for the 2 examinations. Three blinded readers evaluated images qualitatively for diagnostic information (lesion extent, delineation, morphology, enhancement, global preference) and quantitatively for CNR and LBR. RESULTS: One hundred fourteen of 123 enrolled patients successfully underwent both examinations. Final diagnoses were intra-axial tumors, metastases, extra-axial tumors, “other” tumors, and “nontumor” (49, 46, 8, 7, and 4 subjects, respectively). Readers 1, 2, and 3 demonstrated preference for gadobenate dimeglumine in 46 (40.7%), 54 (47.4%), and 49 (43.0%) patients, respectively, compared with 6, 7, and 7 patients for gadobutrol (P < .0001, all readers). Highly significant (P < .0001, all readers) preference for gadobenate dimeglumine was demonstrated for all other qualitative end points. Inter-reader agreement was good for all evaluations (κ = 0.414–0.629). Significantly superior CNR and LBR were determined for gadobenate dimeglumine (P < .019, all readers). CONCLUSIONS: Significantly greater morphologic information and lesion enhancement are achieved on brain MR imaging with 0.1-mmol/kg gadobenate dimeglumine compared with gadobutrol at an equivalent dose.

The concept of Nash equilibrium, developed by John Forbes Nash Jr, states that an equilibrium in noncooperative games is reached when each player takes the best action for himself or herself, taking into account the actions of the other players. We apply this concept to the provision of endovascular thrombectomy in the treatment of acute ischemic stroke and suggest that collaboration among hospitals in a health care jurisdiction could result in practices such as shared call pools for neurointervention teams, leading to better patient care through streamlined systems.

There are 2 “epochs” of time in acute ischemic stroke caused by large vessel occlusion: onset to imaging time, which is deterministic of the likelihood of favorable imaging (mild to moderate early ischemic changes [ASPECTS 6–10]), and imaging to reperfusion time, which is deterministic of the

BACKGROUND AND PURPOSE: The regional leptomeningeal score is a strong and reliable imaging predictor of good clinical outcomes in acute anterior circulation ischemic strokes and can therefore be used for imaging based patient selection. Efforts to determine biological determinants of collateral status are needed if techniques to alter collateral behavior and extend time windows are to succeed. MATERIALS AND METHODS: This was a retrospective Institutional Review Board–approved study of patients with acute ischemic stroke and M1 middle cerebral artery+/− intracranial internal carotid artery occlusion at our center from 2003 to 2009. The rLMC score is based on scoring pial and lenticulostriate arteries (0, no; 1, less; 2, equal or more prominent compared with matching region in opposite hemisphere) in 6 ASPECTS regions (M1–6) plus anterior cerebral artery region and basal ganglia. Pial arteries in the Sylvian sulcus are scored 0, 2, or 4. Good clinical outcome was defined as mRS ≤2 at 90 days. RESULTS: The analysis included 138 patients: 37.6% had a good (17–20), 40.5% a medium (11–16), and 21.7% a poor (0–10) rLMC score. Interrater reliability was high, with an intraclass correlation coefficient of 0.87 (95% CI, 0.77%–0.95%). On univariate analysis, no single vascular risk factor was associated with the presence of poor rLMCs (P ≥ .20 for all comparisons). In multivariable analysis, the rLMC score (good versus poor: OR, 16.7; 95% CI, 2.9%–97.4%; medium versus poor: OR, 9.2, 95% CI, 1.7%–50.6%), age (

BACKGROUND AND PURPOSE: Atherosclerotic disease of the carotid artery is an important cause of ischemic stroke. We evaluated carotid plaque morphologic features by using CTA in addition to stenosis in the setting of symptomatic hemispheric TIA/stroke to identify factors that may predict plaque activity. MATERIALS AND METHODS: Six hundred seventy-three patients (408 men; ages, 18–91 years; mean, 65.8 ± 15.2 years) presenting with hemispheric ischemic symptoms and having a CTA that included imaging of both carotid arteries within 24 hours were studied. Scans were interpreted for morphologic features, such as plaque length and width, attenuation, shape, surface, presence and degree of calcification, and ILT in addition to stenosis. RESULTS: Univariable analysis showed that carotid occlusions (P = .01, OR = 5.27), high-grade stenosis (70%–99%) (P = .06, OR = 1.8), and the presence of ILT (P = .01, OR = 4.33) were highly predictive of the symptomatic side. Smooth plaque (P = .01, OR = 0.73) and extensive calcification (P = .03, OR = 0.72) were more commonly associated with the asymptomatic side. There was no correlation between plaque hypoattenuation (P = .7, OR = 1.06) or ulcerated plaque (P = .74, OR = 0.955) in predicting the symptomatic side. In a multivariable logistic regression model, the presence of ILT was still found to be significantly associated with the symptomatic side (P = .048, OR = 3.1) and the presence of extensive calcification, with the asymptomatic carotid artery (P = .047, OR = 0.69). CONCLUSIONS: In addition to higher stenosis grades, the presence of ILT is highly predictive of the symptomatic side in carotid disease. Smooth plaque and extensive calcification seem to afford a protective effect. This information may be useful in radiologic risk stratification in carotid disease in addition to the current evidence available based on stenosis criteria alone.

In the treatment of acute stroke, we are reasonably sure of certain issues. These are the following: On the other hand, there are issues that we do not fully understand. The key ones are the following: Other relevant issues are related to the imaging technique that is the best, most