Systematic comparison of perfusion-CT and CT-angiography in acute stroke patients

Intracranial Cerebrospinal Fluid Volume as a Predictor of Malignant Middle Cerebral Artery Infarction

Background and Purpose- Predicting malignant middle cerebral artery (MCA) infarction can help to identify patients who may benefit from preventive decompressive surgery. We aimed to investigate the association between the ratio of intracranial cerebrospinal fluid (CSF) volume to intracranial volume (ICV) and malignant MCA infarction. Methods- Patients with an occlusion proximal to the M3 segment of the MCA were selected from the DUST (Dutch Acute Stroke Study). Admission imaging included noncontrast computed tomography (CT), CT perfusion, and CT angiography. Patient characteristics and CT findings were collected. The ratio of intracranial CSF volume to ICV (CSF/ICV) was quantified on admission thin-slice noncontrast CT. Malignant MCA infarction was defined as a midline shift of >5 mm on follow-up noncontrast CT, which was performed 3 days after the stroke or in case of clinical deterioration. To test the association between CSF/ICV and malignant MCA infarction, odds ratios and 95% CIs were calculated for 3 multivariable models by using binary logistic regression. Model performances were compared by using the likelihood ratio test. Results- Of the 286 included patients, 35 (12%) developed malignant MCA infarction. CSF/ICV was independently associated with malignant MCA infarction in 3 multivariable models: (1) with age and admission National Institutes of Health Stroke Scale (odds ratio, 3.3; 95% CI, 1.1-11.1), (2) with admission National Institutes of Health Stroke Scale and poor collateral score (odds ratio, 7.0; 95% CI, 2.6-21.3), and (3) with terminal internal carotid artery or proximal M1 occlusion and poor collateral score (odds ratio, 7.7; 95% CI, 2.8-23.9). The performance of model 1 (areas under the receiver operating characteristic curves, 0.795 versus 0.824; P=0.033), model 2 (areas under the receiver operating characteristic curves, 0.813 versus 0.850; P<0.001), and model 3 (areas under the receiver operating characteristic curves, 0.811 versus 0.856; P<0.001) improved significantly after adding CSF/ICV. Conclusions- The CSF/ICV ratio is associated with malignant MCA infarction and has added value to clinical and imaging prediction models in limited numbers of patients.

Stroke progression and clinical outcome in ischemic stroke patients with a history of migraine

Background

Patients with migraine might be more susceptible of spreading depolarizations, which are known to affect vascular and neuronal function and penumbra recovery after stroke. We investigated whether these patients have more severe stroke progression and less favorable outcomes after recanalization therapy.

Methods

We included patients from a prospective multicenter ischemic stroke cohort. Lifetime migraine history was based on the International Classification of Headache Disorders II criteria. Patients without confirmed migraine diagnosis were excluded. Patients underwent CT angiography and CT perfusion <9 h of onset and follow-up CT after three days. On admission, presence of a perfusion deficit, infarct core and penumbra volume, and blood brain barrier permeability (BBBP) were assessed. At follow-up we assessed malignant edema, hemorrhagic transformation, and final infarct volume. Outcome at three months was evaluated with the modified Rankin Scale (mRS). We calculated adjusted relative risks (aRR) or difference of means (aB) with regression analyses.

Results

We included 600 patients of whom 43 had migraine. There were no differences between patients with or without migraine in presence of a perfusion deficit on admission (aRR: 0.98, 95%CI: 0.77–1.25), infarct core volume (aB: -10.8, 95%CI: -27.04–5.51), penumbra volume (aB: -11.6, 95%CI: -26.52–3.38), mean blood brain barrier permeability (aB: 0.08, 95%CI: -3.11–2.96), malignant edema (0% vs. 5%), hemorrhagic transformation (aRR: 0.26, 95%CI: 0.04–1.73), final infarct volume (aB: -14.8, 95%CI: 29.9–0.2) or outcome after recanalization therapy (mRS > 2, aRR: 0.50, 95%CI: 0.21–1.22).

Conclusion

Elderly patients with a history of migraine do not seem to have more severe stroke progression and have similar treatment outcomes compared with patients without migraine.

Collaterals are a major determinant of the core but not the penumbra volume in acute ischemic stroke

PURPOSE

Determinants of early loss of ischemic tissue (core) or its prolonged survival (penumbra) in acute ischemic stroke (AIS) are poorly understood. We aimed to identify radiological associations of core and penumbra volumes on CT perfusion (CTP) in a large cohort of AIS.

METHODS

In the ASTRAL registry (2003-2016), we identified consecutive AIS patients with proximal middle cerebral artery (MCA) occlusion. We calculated core and penumbra volumes using established thresholds and the mismatch ratio (MR). We graded collaterals into three categories on CT-angiography. We used clot burden score (CBS) to quantify the clot length. We related CTP volumes to radiological variables in multivariate regression analyses, adjusted for time from stroke onset to first imaging.

RESULTS

The median age of the 415 included patients was 69 years (IQR = 21) and 49% were female. Median admission NIHSS was 16 (11) and median delay to imaging 2.2 h (1.9). Lower core volumes were associated with higher ASPECTS (hazard ratio = 1.08), absence of hyperdense MCA sign (HR = 0.70), higher CBS (i.e., smaller clot, HR = 1.10), and better collaterals (HR = 1.95). Higher penumbra volumes were related to lower CBS (i.e., longer clot, HR = 1.08) and proximal intracranial occlusion (HR = 1.47), but not to collaterals. Higher MR was found in absence of hyperdense MCA sign (HR = 1.28), absence of distal intracranial occlusion (HR = 1.39), and with better collaterals (HR = 0.52).

CONCLUSIONS

In AIS, better collaterals were associated with lower core volumes, but not with higher penumbra volumes. This suggests a major role of collaterals in early tissue loss and their limited significance as marker of salvageable tissue.

Factors influencing infarct growth including collateral status assessed using computed tomography in acute stroke patients with large artery occlusion

In major ischemic stroke caused by a large artery occlusion, neuronal loss varies considerably across individuals without revascularization. This study aims to identify which patient characteristics are most highly associated with this variability. Demographic and clinical information were retrospectively collected on a registry of 878 patients. Imaging biomarkers including Alberta Stroke Program Early CT score, noncontrast head computed tomography infarct volume, perfusion computed tomography infarct core and penumbra, occlusion site, collateral score, and recanalization status were evaluated on the baseline and early follow-up computed tomography images. Infarct growth rates were calculated by dividing infarct volumes by the time elapsed between the computed tomography scan and the symptom onset. Collateral score was graded into four levels (0, 1, 2, and 3) in comparison with the normal side. Correlation of perfusion computed tomography and noncontrast head computed tomography infarct volumes and infarct growth rates were estimated with the nonparametric Spearman's rank correlation. Conditional inference trees were used to identify the clinical and imaging biomarkers that were most highly associated with the infarct growth rate and modified Rankin Scale at 90 days. Two hundred and thirty-two patients met the inclusion criteria for this study. The median infarct growth rates for perfusion computed tomography and noncontrast head computed tomography were 11.2 and 6.2 ml/log(min) in logarithmic model, and 18.9 and 10.4 ml/h in linear model, respectively. Noncontrast head computed tomography and perfusion computed tomography infarct volumes and infarct growth rates were significantly correlated (rho=0.53; P < 0.001). Collateral status was the strongest predictor for infarct growth rates. For collateral=0, the perfusion computed tomography and noncontrast head computed tomography infarct growth rate were 31.56 and 16.86 ml/log(min), respectively. Patients who had collateral >0 and penumbra volumes>92 ml had the lowest predicted perfusion computed tomography infarct growth rates (6.61 ml/log(min)). Collateral status was closely related to the diversity of infarct growth rates, poor collaterals were associated with a faster infarct growth rates and vice versa.

Cerebral Collateral Circulation: A Review in the Context of Ischemic Stroke and Mechanical Thrombectomy

The pial (leptomenigeal) collateral circulation is a key determinant of functional outcome after mechanical thrombectomy after large-vessel ischemic stroke. Patients with good collateral blood flow benefit up to 24 hours after stroke onset, whereas those with poor collateral flow evidence less or no benefit. However, clues to why collateral flow varies so widely among patients have remained elusive. Recent findings in animal studies, which are currently being tested for confirmation in humans, have found that naturally occurring variants of a novel "collateral gene," Rabep2, result in large differences in the extent of anatomic collaterals and thus blood flow and infarct size in mice after stroke. The comprehension of collagerogenesis in humans and the evaluation of collateral status could aid in identifying patients who will benefit not only from mechanical thrombectomy in the extended time window but also from any reperfusion strategy. We performed a literature review focused on radiographic, clinical, and genetic aspects of the collateral circulation.

Acute reperfusion without recanalization: Serial assessment of collaterals within 6 h of using perfusion-weighted magnetic resonance imaging

Acute reperfusion despite persistent arterial occlusion may occur in up to 30% of ischemic stroke patients. Recruitment of leptomeningeal collaterals may explain this phenomenon. Using dynamic susceptibility-contrast perfusion imaging (DSC-PI), we assessed acute changes in collateral flow among patients without recanalization. From a multicenter prospective database (I-KNOW), 46 patients with magnetic resonance angiography visible occlusion in whom both reperfusion and recanalization were assessed within 6 h of onset were identified. Maps of collateral flow at arterial, capillary and late venous phases were generated from DSC-PI through inter-frame registration, baseline signal subtraction and temporal summation, and graded blind to all other relevant clinical and radiological data using the Higashida scale. Flow direction and the acute evolution of collaterals were evaluated against the reperfusion status. Among patients without recanalization ( n = 33), flow direction remained retrograde. Collateral grades significantly improved between admission and acute follow-up in patients who reperfused (OR: 4.57; 95% CI: 1.1-22.7; p = 0.048), but not in those without reperfusion (OR: 1.34; 95% CI: 0.4-4.5; p = 0.623). Our study confirmed that acute reperfusion without recanalization is associated with a significant improvement of retrograde collateral flow. DSC-PI can detect acute changes in collateral flow, and may help evaluate novel treatments targeting leptomeningeal collaterals.

Determining factors of better leptomeningeal collaterals: a study of 857 consecutive acute ischemic stroke patients

BACKGROUND

In acute ischemic stroke (AIS) collaterals correlate with infarct size, recanalization rate and clinical outcome. We aimed to identify factors associated with better collateral status in a large series of AIS patients with middle cerebral artery (MCA) occlusion.

METHODS

In the Acute STroke Registry and Analysis of Lausanne (ASTRAL) from 2003 to 2016, we identified all consecutive AIS with proximal MCA occlusion on CT-angiography performed < 24 h. Collaterals were scored from 0 (absent) to 3 (≥ 100%) and related to multiple demographic, clinical, metabolic and radiological variables in a multivariate regression analysis (MVA).

RESULTS

The 857 included patients had a median age of 72.3 years, 48.4% were female and median admission NIHSS was 16. Better collaterals were associated with younger age (OR 0.99; 95% CI 0.98-1.00), hemineglect (OR 1.35; 95% CI 1.03-1.76), absence of visual field defects (OR 0.64; 95% CI 0.46-0.90), eye deviation (OR 0.58; 95% CI 0.43-0.79) and decreased vigilance (OR 0.62; 95% CI 0.44-0.88). Better collaterals were also associated with dyslipidemia (OR 1.57; 95% CI 1.16-2.13), no previous statin use (OR 0.69; 95% CI 0.50-0.95), and lower creatinine levels (OR 0.99; 95% CI 0.99-1.00). On neuroimaging, better collaterals related to higher ASPECTS score (OR 1.27; 95% CI 1.20-1.35) and higher clot burden score (OR 1.09; 95% CI 1.03-1.14).

CONCLUSIONS

Younger age, dyslipidemia and lower creatinine levels were predictors of better collaterals in AIS patients from proximal MCA occlusions. Greater degree of collaterals related to lower stroke severity on admission. On neuroimaging, better collaterals were independently associated with minor early ischemic changes and lower clot burden. These data may add knowledge on pathophysiology of collaterals development and may help to identify patients with better collaterals for late or aggressive recanalization treatments.

Collateral perfusion using arterial spin labeling in symptomatic versus asymptomatic middle cerebral artery stenosis

The purpose was to assess the difference of collaterals in symptomatic versus asymptomatic patients with unilateral middle cerebral artery (MCA) stenosis by comparing cerebral blood flow (CBF) at two post labeling delays (PLD) using three-dimensional pseudo-continuous arterial spin labeling (3D pCASL). Eighty-one patients (49 symptomatic and 32 asymptomatic) with unilateral MCA stenosis ≥50% who underwent pCASL with two PLDs were included. Mean CBF and CBF subtraction images between two PLDs of MCA territories were compared in symptomatic and asymptomatic groups, respectively. Compared with the asymptomatic group, patients with symptomatic MCA stenosis had significantly lower CBF in the MCA territory of stenotic side at each PLD. The CBF of stenotic territory showed greater increase than that of normal side from PLD 1.5 to 2.5 s. The CBF of asymptomatic MCA territory increased similarly with that of symptomatic MCA territory from PLD of 1.5 to 2.5 s in stenotic side, while symptomatic patients experienced significantly slower antegrade flow. On CBF subtraction images, asymptomatic patients showed larger volume of differences between PLD of 1.5 and 2.5 s compared with those of symptomatic patients ( p = 0.037). The results suggest that more robust collateral perfusion on two-delay 3D pCASL is present in asymptomatic patients compared with symptomatic patients.

Single-phase CT angiography: collateral grade is independent of scan weighting

PURPOSE

Collateral grading may vary on single-phase CTA (sCTA) depending on whether the CTA is arterial (A), arteriovenous (AV), or venous (V) weighted. We studied the impact of sCTA weighting on collateral grading using the Tan, MAAS, and Menon methods, and their ability to predict infarct and clinical outcome hypothesizing that AV-weighted sCTA should better predict these outcomes.

METHODS

Multicenter retrospective analysis of 212 patients undergoing baseline CTP/sCTA. sCTA weighting was determined by comparing ICA to torcula AV ratios with those from concomitant CTP time-density curves at peak arterial or venous contrast attenuation. A generalized linear mixed model investigated the predictive value for infarct volume or 90-day mRS of the three collateral scores stratified by sCTA weighting and adjusting for age, sex, clot burden score (CBS), and NIHSS. Bayesian information criterion (BIC) differences were calculated between the null and fitted models.

RESULTS

Mean age, baseline median NIHSS, ASPECTS, and onset to treatment time were 69.89 ± 14.45, 13 (6-18), 10 (8-10), and 128 (66-181) minutes. sCTA scans were AV-weighted in 137/212 (65%) and A-weighted in 73 (34%). No association was demonstrated between sCTA weighting, hospital site, and sCTA technique. All collateral scores were related to infarct volume irrespective of sCTA weighting, with greatest fit with the regional leptomeningeal score (BIC 18.29, p = 0.0001). No association was shown between sCTA weighting, collateral grade, and clinical outcome.

CONCLUSION

sCTA weighting did not significantly impact collateral grade using three common collateral scores or their ability to predict final infarct.

Effect of mechanical thrombectomy alone or in combination with intravenous thrombolysis for acute ischemic stroke

OBJECTIVE AND DESIGN

Whether combining intravenous thrombolysis (IVT) and mechanical thrombectomy (MT) is superior to mechanical thrombectomy alone for large vessel occlusion acute ischemic stroke is still uncertain. Our aim was to compare the safety and the efficacy of these two therapeutic strategies.

MATERIALS

Patients with acute ischemic stroke secondary to anterior circulation large vessel occlusion.

METHODS

A retrospective analysis was conducted. IVT was performed with full dose recombinant tissue plasminogen activator. MT alone was performed only if intravenous thrombolysis was contraindicated. Primary outcomes were successful reperfusion, 3-month functional independence, symptomatic intracranial hemorrhage (sICH), and 3-month mortality.

RESULTS

325 patients were analyzed: 193 treated with combined IVT and MT, 132 with MT alone. The combined treatment group showed higher systolic blood pressure (140 [80-230] vs 150 [90-220]; p = 0.036), rate of good collaterals (55.9% vs 67%; p = 0.03), use of aspiration devices (68.2% vs 79.3%; p = 0.003) and shorter onset-to-reperfusion time (300 [90-845] vs 288 [141-435]; p = 0.008). No differences were found in the efficacy and safety outcomes except for mortality which was lower in the combined treatment group (36.4% vs 25.4%; p = 0.02). However, after multivariable analysis combined treatment was not associated with lower mortality (OR 1.47; 95% CI 0.73-2.96; p = 0.3).

CONCLUSIONS

Our study suggests that mechanical thrombectomy alone is effective and safe in patients with contraindications to intravenous thrombolysis. Preceding use of IVT in eligible patients was not associated with increased harm or benefit. Randomized controlled trials are needed to clarify whether intravenous thrombolysis before mechanical thrombectomy is associated with additional benefit.

Outcome Prediction Using Perfusion Parameters and Collateral Scores of Multi-Phase and Single-Phase CT Angiography in Acute Stroke: Need for One, Two, Three, or Thirty Scans?

BACKGROUND AND PURPOSE

Collateral status is an important factor determining outcome in acute ischemic stroke (AIS). Hence, different collateral scoring systems have been introduced. We applied different scoring systems on single- and multi-phase computed tomography (CT) angiography (spCTA and mpCTA) and compared them to CT perfusion (CTP) parameters to identify the best method for collateral evaluation in patients with AIS.

METHODS

A total of 102 patients with AIS due to large vessel occlusion in the anterior circulation who underwent multimodal CT imaging and who were treated endovascularly were included. Collateral status was assessed on spCTA and mpCTA using four different scoring systems and compared to CTP parameters. Logistic regression was performed for predicting favorable outcome.

RESULTS

All collateral scores correlated well with each other and with CTP parameters. Comparison of collateral scores stratified by extent of perfusion deficit showed relevant differences between groups (P<0.01 for each). An spCTA collateral score discriminated best between favorable and unfavorable outcome as determined using the modified Rankin Scale 3 months after stroke.

CONCLUSION

s Collateral status evaluated on spCTA may suffice for outcome prediction and decision making in AIS patients, potentially obviating further imaging modalities like mpCTA or CTP.

Collateral status affects the onset-to-reperfusion time window for good outcome

OBJECTIVE

To characterise the time window in which endovascular thrombectomy (EVT) is associated with good outcome, and to test the differential relationship between functional outcome and onset-to-reperfusion time (ORT), depending on collateral status.

METHODS

This was a retrospective analysis of clinical and imaging data of 554 consecutive patients, who had recanalisation success by EVT for anterior circulation large artery occlusion, from the prospectively maintained registries of 16 comprehensive stroke centres between September 2010 and December 2015. The patients were dichotomised into good and poor collateral groups, based on CT angiography. We tested whether the likelihood of good outcome (modified Rankin Scale, 0-2) by ORT was different between two groups.

RESULTS

ORT was 298 min±113 min (range, 81-665 min), and 84.5% of patients had good collaterals. Age, diabetes mellitus, previous infarction, National Institutes of Health Stroke Scale, good collaterals (OR 40.766; 95% CI 10.668 to 155.78; p<0.001) and ORT (OR 0.926 every 30 min delay; 95% CI 0.862 to 0.995; p=0.037) were independently associated with good outcome. The drop in likelihood of good outcome associated with longer ORT was significantly faster in poor collateral group (OR 0.305 for every 30 min; 95% CI 0.113 to 0.822) than in good collateral group (OR 0.926 for every 30 min; 95% CI 0.875 to 0.980).

CONCLUSIONS

Earlier successful recanalisation was strongly associated with good outcome in poor collateral group; however, this association was weak during the tested time window in good collateral group. This suggests that the ORT window for good outcome can be adjusted according to collateral status.

The Prognostic Value of CT-Angiographic Parameters After Reperfusion Therapy in Acute Ischemic Stroke Patients With Internal Carotid Artery Terminus Occlusion: Leptomeningeal Collateral Status and Clot Burden Score

BACKGROUND

The objective of this study was to investigate the prognostic value of computed tomographic angiography (CTA) based on leptomeningeal collateral (LMC) status and other parameters in acute ischemic stroke (AIS) patients with internal carotid artery (ICA) terminus occlusion treated with endovascular treatment (EVT).

METHODS

All eligible patients from January 2013 to December 2017 undergoing EVT were retrospectively reviewed. The regional leptomeningeal score was used to assess the LMCs on baseline CTA. The collateral status measured by the LMC score (0-20) was trichotomized into 3 groups: good (17-20), intermediate (11-16), and poor (0-10).

RESULTS

Our sample included a total of 119 eligible patients (60 males; mean age, 73 years) with a median baseline National Institute of Health Stroke Scale (NIHSS) score of 14. Patients with a good LMC score had a lower baseline mean NIHSS score, a higher mean Alberta Stroke Program Early CT score, and a higher mean clot burden score (CBS). Baseline NIHSS score <15 (odds ratio [OR] 3.69 95% confidence ratio [CI]: 1.32-10.29, P = .013), CBS ≥ 6 (OR 3.97 95%CI: 1.05-14.99, P = .042), good LMC score (OR 5.14 95%CI: 1.62-16.26, P = .005) and successful recanalization (OR 11.55 95%CI: 2.72-48.99 P = .001) were independent predictors of good clinical outcomes.

CONCLUSIONS

CTA-based LMC status and CBS are powerful predictors of clinical outcomes in patients with an acute ICA terminus occlusion treated with EVT.

Endovascular Thrombectomy >24-hr From Stroke Symptom Onset

Background: Trials have demonstrated efficacy for endovascular thrombectomy (EVT) for anterior circulation acute ischaemic stroke (AIS) up to 24-h from symptom onset. The magnitude of effect suggests benefit may exist beyond 24-h.

Objectives: To perform a retrospective review of all patients undergoing EVT for anterior circulation LVO stroke beyond 24-h from symptom onset and assess safety and efficacy.

Methods:A prospectively maintained database of EVT patients treated at two comprehensive stroke centers between January 2016 and December 2017 was retrospectively screened. Patients undergoing EVT for anterior circulation AIS >24-h from symptom onset were selected.

Results: A total of 429 AIS patient underwent EVT in the study period. Five patients treated >24-h from symptom onset were identified. The median age was 72 (range 42–84); median ASPECTS 8 (range 6–8); median baseline-NIHSS 9 (range 4–17); and median time from symptom onset to groin puncture 44 h and 55 min (range 25:07-90:10). One patient underwent CT perfusion imaging. The remaining four patients were selected based on non-contrast CT brain and CT-angiography. Two patients had tandem cervical carotid lesions and underwent acute stenting. Modified thrombolysis in cerebral ischaemia (mTICI) 3 reperfusion was achieved in four patients. No hemorrhagic transformation occurred. All patients were alive at 90-day follow-up. Four patients achieved functional independence at 90-days (mRS 0-2).

Conclusion: Endovascular thrombectomy for AIS patients beyond 24-h from symptom onset appears to be safe and effective in this limited study. There is a need for further evidence-based trials of benefit vs. risk in very prolonged time windows.

Slow Collateral Flow Is Associated with Thrombus Extension in Patients with Acute Large-Artery Occlusion

BACKGROUND AND PURPOSE

It is still poorly understood about the dynamic changes of the thrombus after intravenous thrombolysis and how the remaining thrombus affects clinical outcome in human stroke. Collateral flow was assumed to help to deliver endo/exogenous tissue-type plasminogen activator to the clot. We aimed to analyze the impact of collateral flow on the dynamic changes of the thrombus in patients with acute large-artery occlusion who received intravenous thrombolysis.

MATERIALS AND METHODS

We reviewed consecutive patients with acute ischemic stroke with M1 segment or distal internal carotid artery occlusion who underwent multimodal MR imaging or CT perfusion before and 24 hours after intravenous thrombolysis without recanalization. Patients were divided into 3 groups (thrombus extension, shortening, and no change) according to thrombus-length change between baseline and 24 hours. Collateral flow was measured with arrival time delay and the collateral scoring system. Poor outcome was defined as a 3-month modified Rankin Scale score of ≥3.

RESULTS

Among 51 patients, 18 (35.3%) had thrombus extension, 14 (27%) had thrombus shortening, and 19 (37.3%) had thrombus without change. Arrival time delay was independently associated with thrombus extension (OR = 1.499; 95% CI, 1.053-2.135; P = .025). Similarly, the collateral score on the peak artery phase was independently associated with thrombus extension (OR = 0.456; 95% CI, 0.211-0.984; P = .045), whereas baseline National Institutes of Health Stroke Scale score (OR = 0.768; 95% CI, 0.614-0.961; P = .021) and baseline thrombus length (OR = 1.193; 95% CI, 1.021-1.394; P = .026) were associated with thrombus shortening. All patients with thrombus extension had poor outcomes.

CONCLUSIONS

Slow collateral flow was related to thrombus extension in patients with large-artery occlusion without recanalization after intravenous thrombolysis.

Infarct Core Expansion on Computed Tomography before and after Intravenous Thrombolysis

PURPOSE

Infarct core can expand rapidly in acute stroke patients receiving intravenous tissue plasminogen activator (IV t-PA). We investigated changes in the extent of infarct core during IV t-PA treatment, and explored the associative factors of this infarct core expansion in patients with proximal artery occlusion.

MATERIALS AND METHODS

We included patients who were considered for sequential intra-arterial therapy (IAT) due to occlusion of intracranial proximal artery after IV t-PA. Patients who had a baseline Alberta Stroke Program Early Computed Tomography (CT) Score (ASPECTS) ≥6 and who underwent two consecutive CT scans before and shortly after IV t-PA infusion were enrolled. Patients were classified into no, moderate, and marked expansion groups based on decreases in ASPECTS (0-1, 2-3, and ≥4, respectively) on follow-up CT. Collateral status was graded using CT angiography.

RESULTS

Of the 104 patients, 16 (15.4%) patients showed moderate and 13 (12.5%) patients showed marked infarct core expansion on follow-up CT scans obtained at 71.1±19.1 min after baseline CT scan. Sixteen (15.4%) patients had an ASPECTS value <6 on the follow-up CT. None of the patients with marked expansion were independent at 3 months. Univariate analysis and ordinal logistic regression analysis demonstrated that the infarct core expansion was significantly associated with collateral status (p<0.001).

CONCLUSION

Among patients who were considered for IAT after IV t-PA treatment, one out of every seven patients exhibited marked expansion of infarct core on follow-up CT before IAT. These patients tend to have poor collaterals and poor outcomes despite rescue IAT.

Computed Tomography Perfusion Derived Blood-Brain Barrier Permeability Does Not Yet Improve Prediction of Hemorrhagic Transformation

INTRODUCTION

Hemorrhagic transformation (HT) in acute ischemic stroke can occur as a result of reperfusion treatment. While withholding treatment may be warranted in patients with increased risk of HT, prediction of HT remains difficult. Nonlinear regression analysis can be used to estimate blood-brain barrier permeability (BBBP). The aim of this study was to identify a combination of clinical and imaging variables, including BBBP estimations, that can predict HT.

MATERIALS AND METHODS

From the Dutch acute stroke study, 545 patients treated with intravenous recombinant tissue plasminogen activator and/or intra-arterial treatment were selected, with available admission extended computed tomography (CT) perfusion and follow-up imaging. Patient admission treatment characteristics and CT imaging parameters regarding occlusion site, stroke severity, and BBBP were recorded. HT was assessed on day 3 follow-up imaging. The association between potential predictors and HT was analyzed using univariate and multivariate logistic regression. To compare the added value of BBBP, areas under the curve (AUCs) were created from 2 models, with and without BBBP.

RESULTS

HT occurred in 57 patients (10%). In univariate analysis, older age (OR 1.03, 95% CI 1.006-1.05), higher admission National Institutes of Health Stroke Scale (NIHSS; OR 1.13, 95% CI 1.08-1.18), higher clot burden (OR 1.28, 95% CI 1.16-1.41), poor collateral score (OR 3.49, 95% CI 1.85-6.58), larger Alberta Stroke Program Early CT Score cerebral blood volume deficit size (OR 1.26, 95% CI 1.14-1.38), and increased BBBP (OR 2.22, 95% CI 1.46-3.37) were associated with HT. In multivariate analysis with age and admission NIHSS, the addition of BBBP did not improve the AUC compared to both independent predictors alone (AUC 0.77, 95% CI 0.71-0.83).

CONCLUSION

BBBP predicts HT but does not improve prediction with age and admission NIHSS.

Predictors of short-term outcome in patients with acute middle cerebral artery occlusion: unsuitability of fluid-attenuated inversion recovery vascular hyperintensity scores

Fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH) is used to assess leptomeningeal collateral circulation, but clinical outcomes of patients with FVH can be very different. The aim of the present study was to assess a FVH score and explore its relationship with clinical outcomes. Patients with acute ischemic stroke due to middle cerebral artery M1 occlusion underwent magnetic resonance imaging and were followed up at 10 days (National Institutes of Health Stroke Scale) and 90 days (modified Rankin Scale) to determine short-term clinical outcomes. Effective collateral circulation indirectly improved recovery of neurological function and short-term clinical outcome by extending the size of the pial penumbra and reducing infarct lesions. FVH score showed no correlation with 90-day functional clinical outcome and was not sufficient as an independent predictor of short-term clinical outcome.

Imaging assessment of acute ischaemic stroke: a review of radiological methods

Acute ischaemic stroke is the second largest cause of death worldwide and a cause of major physical and psychological morbidity. Current evidence based treatment includes intravenous thrombolysis (IVT) and mechanical thrombectomy (MT), both requiring careful patient selection and to be administered as quickly as possible within a limited time window from symptom onset. Imaging plays a crucial role identifying patients who may benefit from MT or IVT whilst excluding those that may be harmed. For IVT, imaging must as a minimum exclude haemorrhage, stroke mimics and provide an estimate of non-viable brain. For MT, imaging must in addition detect and characterize intra-arterial thrombus and assess the intra and extracranial arterial architecture. More advanced imaging techniques may be used to assess more accurately the volume of non-viable and potentially salvageable brain tissue. It is highly likely that further research will identify patients who would benefit from treatment beyond currently accepted time windows for IVT (4.5 h) and MT (6 h) and patients with an unknown time of symptom onset. Current evidence indicates that best outcomes are achieved when treatment is instituted as soon as possible after symptom onset. A rapid, efficient imaging pathway including interpretation is fundamental to achieving the best outcomes. This review summarizes current techniques for imaging assessment of acute stroke, highlighting strengths and limitations of each. The optimum pathway is a balance between diagnostic information, local resources, specialization and the time taken to acquire, process and interpret the data. As new evidence emerges, it is likely that the minimum required imaging data will change.

Mechanical Thrombectomy with Solitaire Stent Retrieval for Acute Cardioembolic Stroke

Objective

Few studies have reported the outcome of mechanical thrombectomy with Solitaire stent retrival (MTSR) in subtypes of acute ischemic stroke. The purpose of this study was to evaluate the efficacy and result of MTSR in acute cardioembolic stroke.

Methods

Twenty consecutive patients with acute cardioembolic stroke were treated by MTSR. The angiographic outcome was assessed by thrombolysis in cerebral infarction (TICI) grade. TICI grade 2a, 2b, or 3 with a measurable thrombus that was retrieved was considered as a success when MTSR was performed in the site of primary vessel occlusion, and TICI grade 2b or 3 was considered as a success when final result was reported. Clinical and radiological results were compared between two groups divided on the basis of final results of MTSR. Persistent thrombus compression sign on angiogram was defined as a stenotic, tapered arterial lumen whenever temporary stenting was performed. The clinical outcomes were assessed by the modified Rankin Scale (mRS) at 3 months.

Results

The failure rate of MTSR was 20% (4/20) and other modalities, such as permanent stenting, were needed. Final successful recanalization (TICI grade 2b or 3) was 80% when other treatments were included. The rate of good outcome (mRS≤2) was 35% at the 3-month follow-up. Failure of MTSR was significantly correlated with persistent thrombus compression sign (p=0.001).

Conclusion

Some cases of cardioembolic stroke are resistant to MTSR and may need other treatment modalities. Careful interpretation of angiogram may be helpful to the decision.

Time-resolved CT assessment of collaterals as imaging biomarkers to predict clinical outcomes in acute ischemic stroke

PURPOSE

Collateral circulation plays a pivotal role in the pathophysiology of acute ischemic stroke and is increasingly recognized as a promising biomarker for predicting the clinical outcome. However, there is no single established grading system. We designed a novel machine-learning software that allows non-invasive, objective, and quantitative assessment of collaterals according to their vascular territories. Our goal is to investigate the prognostic and predictive value of this collateral score for the prediction of acute stroke outcome.

METHODS

This is a retrospective study of 135 patients with anterior circulation stroke treated with IV TPA. An equation using this collateral score (adjusting for age, baseline NIHSS, and recanalization) was derived to predict the clinical outcome (90-day mRS). The primary analyses focused on determining the prognostic value of our newly developed collateral scores. Secondary analyses examined the interrelationships between the collateral score and other variables.

RESULTS

The collateral score emerged as a statistically significant prognostic biomarker for good clinical outcome (p < 0.033) among recanalized patients, but not among non-recanalized patients (p < 0.497). Our results also showed that collateral score was a predictive biomarker (p < 0.044). These results suggest that (1) patients with good collateral score derive more benefit from successful recanalization than patients with poor collateral score and (2) collateral status is inconsequential if recanalization is not achieved.

CONCLUSION

Our data results reinforce the importance of careful patient selection for recanalization therapy to avoid futile recanalization. The paucity of collaterals predicts poor clinical outcome despite recanalization. On the other hand, robust collaterals warrant consideration for recanalization therapy given the better odds of good clinical outcome.

Pretreatment predictors of malignant evolution in patients with ischemic stroke undergoing mechanical thrombectomy

BACKGROUND

Few data exist on malignant middle cerebral artery infarction (MMI) among patients with acute ischemic stroke (AIS) after endovascular treatment (ET). Numerous predictors of MMI evolution have been proposed, but a comprehensive research of patients undergoing ET has never been performed. Our purpose was to find a practical model to determine robust predictors of MMI in patients undergoing ET.

METHODS

Patients from a prospective single-center database with AIS secondary to large intracranial vessel occlusion of the anterior circulation, treated with ET, were retrospectively analyzed. We investigated demographic, clinical, and radiological data. Multivariate regression analysis was used to identify clinical and imaging predictors of MMI.

RESULTS

98 patients were included in the analysis, 35 of whom developed MMI (35.7%). No differences in the rate of successful reperfusion and time from stroke onset to reperfusion were found between the MMI and non-MMI groups. The following parameters were identified as independent predictors of MMI: systolic blood pressure (SBP) on admission (p=0.008), blood glucose (BG) on admission (p=0.024), and the CTangiography (CTA) Alberta Stroke Program Early CT Score (ASPECTS) (p=0.001). A scoreof ≤5 in CTA ASPECTS was the best cut-off to predict MMI evolution (sensitivity 46%; specificity 97%; positive predictive value 78%; negative predictive value 65%).

CONCLUSIONS

in our study a clinical and radiological features-based model was strongly predictive of MMI evolution in AIS. High SBP and BG on admission and, especially, a CTA ASPECTS ≤5 may help to make decisions quickly, regardless of time to treatment and successful reperfusion.

Comparative accuracy of CT perfusion in diagnosing acute ischemic stroke: A systematic review of 27 trials

OBJECTIVE

To systematically evaluate and compare the diagnostic accuracy of CT perfusion (CTP), non-enhanced computed tomography (NCCT) and computed tomography angiography (CTA) in detecting acute ischemic stroke.

METHODS

We searched seven databases and screened the reference lists of the included studies. The risk of bias in the study quality was assessed using QUADASII. We produced paired forest plots in RevMan to show the variation of the sensitivity and specificity estimates together with their 95% CI. We used a hierarchical summary ROC model to summarize the sensitivity and specificity of CTP in detecting ischemic stroke.

RESULTS

We identified 27 studies with a total of 2168 patients. The pooled sensitivity of CTP for acute ischemic stroke was 82% (95% CI 75-88%), and the specificity was 96% (95% CI 89-99%). CTP was more sensitive than NCCT and had a similar accuracy with CTA. There were no statistically significant differences in the sensitivity and specificity between patients who underwent CTP within 6 hours of symptom onset and beyond 6 hours after symptom onset. No adverse events were reported in the included studies.

CONCLUSIONS

CTP is more accurate than NCCT and has similar accuracy to CTA in detecting acute ischemic stroke. However, the evidence is not strong. There is potential benefit of using CTP to select stroke patients for treatment, but more high-quality evidence is needed to confirm this result.

Efficacy and Safety of Mechanical Thrombectomy in Older Adults with Acute Ischemic Stoke

OBJECTIVES

To evaluate the safety and efficacy of endovascular therapy in elderly adults treated for acute ischemic stroke.

DESIGN

Retrospective cohort study.

SETTING

Comprehensive Stroke Center, University of Tor Vergata, Rome, Italy.

PARTICIPANTS

Elderly adults treated for acute ischemic stroke (N = 219).

MEASUREMENTS

Participants were divided into two groups based on their age (n = 62, ≥80; n = 157, <80). Baseline and procedural characteristics, safety outcomes such as intracranial hemorrhage (ICH) and mortality and efficacy outcomes such as successful reperfusion and 3-month good clinical outcome of the two groups were compared. Mutivariable analysis was performed to identify predictors of clinical outcome.

RESULTS

Intravenous thrombolysis was more frequent (67.7% vs 52.8%, P = .04), and onset to reperfusion time was shorter (318.7 ± 128.7 vs 282 ± 53.5, P = .02) in participants aged 80 and older, but no between-group differences were found in terms of successful reperfusion (69% vs 63%, P = .4), good clinical outcome (30.6% vs 34.3%, P = .6), any (37% vs 37.5%, P > .99) or symptomatic (11% vs 14%, P = .6) ICH, or mortality (40.3% vs 29.2%, P = .14). Multivariable analysis revealed that, in the older group, onset National Institute of Health Stroke Scale (NIHSS) score (odds ratio (OR) = 0.65, 95% confidence interval (CI) = 0.44-0.96, P = .03) and 24-hour clinical improvement (OR = 141.13, 95% CI = 2.96-6,720.7, P = .01) were independent predictors of 3-month functional independence.

CONCLUSION

These findings suggest that endovascular treatment for stroke in selected elderly adults could be safe and effective. Major determinants of outcome in this subgroup of elderly patients are presentation NIHSS score and 24-hour clinical improvement.

Prevalence of Imaging Biomarkers to Guide the Planning of Acute Stroke Reperfusion Trials

BACKGROUND AND PURPOSE

Imaging biomarkers are increasingly used as selection criteria for stroke clinical trials. The goal of our study was to determine the prevalence of commonly studied imaging biomarkers in different time windows after acute ischemic stroke onset to better facilitate the design of stroke clinical trials using such biomarkers for patient selection.

METHODS

This retrospective study included 612 patients admitted with a clinical suspicion of acute ischemic stroke with symptom onset no more than 24 hours before completing baseline imaging. Patients with subacute/chronic/remote infarcts and hemorrhage were excluded from this study. Imaging biomarkers were extracted from baseline imaging, which included a noncontrast head computed tomography (CT), perfusion CT, and CT angiography. The prevalence of dichotomized versions of each of the imaging biomarkers in several time windows (time since symptom onset) was assessed and statistically modeled to assess time dependence (not lack thereof).

RESULTS

We created tables showing the prevalence of the imaging biomarkers pertaining to the core, the penumbra and the arterial occlusion for different time windows. All continuous imaging features vary over time. The dichotomized imaging features that vary significantly over time include: noncontrast head computed tomography Alberta Stroke Program Early CT (ASPECT) score and dense artery sign, perfusion CT infarct volume, and CT angiography collateral score and visible clot. The dichotomized imaging features that did not vary significantly over time include the thresholded perfusion CT penumbra volumes.

CONCLUSIONS

As part of the feasibility analysis in stroke clinical trials, this analysis and the resulting tables can help investigators determine sample size and the number needed to screen.

Hypoattenuation on CTA images with large vessel occlusion: timing affects conspicuity

PURPOSE

Parenchymal hypoattenuation distal to occlusions on CTA source images (CTASI) is perceived because of the differences in tissue contrast compared to normally perfused tissue. This difference in conspicuity can be measured objectively. We evaluated the effect of contrast timing on the conspicuity of ischemic areas.

METHODS

We collected consecutive patients, retrospectively, between 2012 and 2014 with large vessel occlusions that had dynamic multiphase CT angiography (CTA) and CT perfusion (CTP). We identified areas of low cerebral blood volume on CTP maps and drew the region of interest (ROI) on the corresponding CTASI. A second ROI was placed in an area of normally perfused tissue. We evaluated conspicuity by comparing the absolute and relative change in attenuation between ischemic and normally perfused tissue over seven time points.

RESULTS

The median absolute and relative conspicuity was greatest at the peak arterial (8.6 HU (IQR 5.1-13.9); 1.15 (1.09-1.26)), notch (9.4 HU (5.8-14.9); 1.17 (1.10-1.27)), and peak venous phases (7.0 HU (3.1-12.7); 1.13 (1.05-1.23)) compared to other portions of the time-attenuation curve (TAC). There was a significant effect of phase on the TAC for the conspicuity of ischemic vs normally perfused areas (P < 0.00001).

CONCLUSION

The conspicuity of ischemic areas distal to a large artery occlusion in acute stroke is dependent on the phase of contrast arrival with dynamic CTASI and is objectively greatest in the mid-phase of the TAC.

Imaging Brain Collaterals: Quantification, Scoring, and Potential Significance

Leptomeningeal collaterals provide the primary source of perfusion to ischemic brain tissue following the onset of acute ischemic stroke and are becoming an important imaging biomarker for stroke therapy triage. Collateral circulation is predictive of infarct growth, end infarct volume, and response to endovascular therapy. The strength of the collateral circulation varies among patients and is partially dependent on genetic and modifiable risk factors. Collateral circulation may be assessed by standard angiographic techniques, including digital subtraction angiography, computed tomography and magnetic resonance (MR) angiography, as well as a growing array of advanced MR techniques including arterial spin labeling and dynamic MR angiography. Simple scoring systems are used to estimate the relative strength of the collateral circulation for a given patient, although there are some discrepancies in the predictive value of these systems. In this review, we discuss methods and techniques for determining the robustness of the collateral circulation and the role of the collateral circulation in acute ischemic stroke assessment and triage.

Severe cerebral hypovolemia on perfusion CT and lower body weight are associated with parenchymal haemorrhage after thrombolysis

INTRODUCTION

Haemorrhagic transformation of acute ischemic stroke (AIS) and particularly parenchymal haemorrhage (PH) remains a feared complication of intravenous thrombolysis (IVT). We aimed to identify clinical and perfusion CT (PCT) variables which are independently associated with PHs.

METHODS

In this observational cohort study, based on the Acute Stroke Registry Analysis of Lausanne (ASTRAL) from 2003 to December 2013, we selected patients with AIS involving the middle cerebral artery (MCA) territory who were thrombolysed within 4.5 h of symptoms' onset and who had a good quality baseline PCT at the beginning of IVT. In addition to demographic, clinical, laboratory and non-contrast CT data, volumes of salvageable tissue and ischemic core on PCT, as well as absolute CBF and CBV values within the ischemic regions were compared in patients with and without PH in multivariate analysis.

RESULTS

Of the 190 included patients, 24 (12.6%) presented a PH (11 had PH1 and 13 had PH2). In multivariate analysis of the clinical and radiological variables, the lowest CBV in the core and lower body weight was both significantly associated with PH (p = 0.009 and p = 0.024, respectively).

CONCLUSION

In thrombolysed MCA strokes, maximal hypoperfusion severity depicted by lowest CBV values in the core region and lower body weight are independently correlated with PH. This information, if confirmed in other case series, may add to the stratification of revascularisation decisions in patients with a perceived high PH risk.

Imaging in Endovascular Stroke Trials

Ischemic stroke remains a leading cause of death and disability worldwide. Various endovascular trials have addressed clinical outcomes without elucidating the impact of imaging studies in patient selection. The success of recent endovascular trials was bolstered by the use of advanced imaging techniques for optimal selection of reperfusion candidates. This seminal juncture in the history of stroke trials warrants further consideration on the use of imaging to guide future refinements in the treatment of acute stroke. In this article, we systematically review the imaging methodology and key facets used in all published endovascular stroke trials to date, discuss the success of recent trials using latest advanced imaging techniques and focus on the importance of imaging studies for future patient selection.

CT angiography-based collateral flow and time to reperfusion are strong predictors of outcome in endovascular treatment of patients with stroke

Background

Collateral flow (CF) is an effective predictor of outcome in acute ischemic stroke (AIS) with potential to sustain the ischemic penumbra. However, the clinical prognostic value of CF in patients with AIS undergoing mechanical thrombectomy has not been clearly established. We evaluated the relationship of CF with clinical outcomes in patients with large artery anterior circulation AIS treated with mechanical thrombectomy.

Methods

Baseline collaterals of patients with AIS (n=135) undergoing mechanical thrombectomy were independently evaluated by CT angiography (CTA) and conventional angiography and dichotomized into poor and good CF. Multivariable analyses were performed to evaluate the predictive effect of CF on outcome and the effect of time to reperfusion on outcome based on adequacy of the collaterals.

Results

Evaluation of CF was consistent by both CTA and conventional angiography (p<0.0001). A higher rate of patients with good collaterals had good functional outcome at 3-month follow-up compared with those with poor collaterals (modified Rankin Scale (mRS) 0–2: 60% vs 10%, p=0.0001). Patients with poor collaterals had a significantly higher mortality rate (mRS 6: 45% vs 8%, p=0.0001). Multivariable analyses showed that CF was the strongest predictor of outcome. Time to reperfusion had a clear effect on favorable outcome (mRS ≤2) in patients with good collaterals; in patients with poor collaterals this effect was only seen when mRS ≤3 was considered an acceptable outcome.

Conclusions

CTA is a valid tool for assessing the ability of CF to predict clinical outcome in patients with AIS treated with mechanical thrombectomy. Limiting time to reperfusion is of definite value in patients with good collaterals and also to some extent in those with poor collaterals.

Collateral state and the effect of endovascular reperfusion therapy on clinical outcome in ischemic stroke patients

PURPOSE

Clinically successful endovascular therapy (EVT) in ischemic stroke requires reliable noninvasive pretherapeutic selection criteria. We investigated the association of imaging parameters including CT angiographic collaterals and degree of reperfusion with clinical outcome after EVT.

METHODS

In our database, we identified 93 patients with large vessel occlusion in the anterior circulation treated with EVT. Besides clinical data, we assessed the baseline Alberta Stroke Program Early CT score (ASPECTS) on noncontrast CT (NCCT) and CT angiography (CTA) source images, collaterals (CT-CS) and clot burden score (CBS) on CTA and the degree of reperfusion after EVT on angiography. Three readers, blinded to clinical information, evaluated the images in consensus. Data-driven multivariable ordinal regression analysis identified predictors of good outcome after 90 days as measured with the modified Rankin Scale.

RESULTS

Successful angiographic reperfusion (OR 26.50; 95%-CI 9.33-83.61) and good collaterals (OR 9.69; 95%-CI 2.28-59.27) were independent predictors of favorable outcome along with female sex (OR 0.35; 95%-CI 0.14-0.85), younger age (OR 0.88; 95%-CI 0.83-0.92) and higher NCCT ASPECTS (OR 2.54; 95%-CI 1.01-6.63). Outcome was best in patients with good collaterals and successful reperfusion, but there was no statistical interaction between collaterals and reperfusion.

CONCLUSIONS

CTA-collateral status was the strongest pretherapeutic predictor of favorable outcome in ischemic stroke patients treated with EVT. CTA-collaterals are thus well suited for patient selection in EVT. However, the independent effect of reperfusion on outcome tended to be stronger than that of CTA-collaterals.

Improving the Evaluation of Collateral Circulation by Multiphase Computed Tomography Angiography in Acute Stroke Patients Treated with Endovascular Reperfusion Therapies

Good collateral circulation (CC) is associated with favorable outcomes in acute stroke, but the best technique to evaluate collaterals is controversial. Single-phase computed tomography angiography (sCTA) is widely used but lacks temporal resolution. We aim to compare CC evaluation by sCTA and multiphase CTA (mCTA) as predictors of outcome in endovascular treated patients.

METHODS

Consecutive endovascular treated patients with M1 middle cerebral artery (MCA) or terminal intracranial carotid artery (TICA) occlusion confirmed by sCTA were included. Two more CTA acquisitions with 8- and 16-second delays were performed for mCTA. Endovascular thrombectomy was performed independently of the CC status according to a local protocol [Alberta Stroke Program Early CT score (ASPECTS) >6, modified Rankin scale (mRS) score <3]. CC on sCTA and mCTA were compared.

RESULTS

108 patients were included. Their mean age was 69.6 ± 13 years and their median National Institutes of Health Stroke Scale (NIHSS) score was 17 (interquartile range 8). 79 (73.1%) had M1 MCA and 29 (26.9%) TICA occlusions. The mean time from symptom onset to CTA was 146.8 ± 96.5 min. On sCTA, 50.9% patients presented good CC vs. 57.5% on mCTA. Good CC status in both sCTA and mCTA had a lower 24-hour infarct volume (27.4 vs. 74.8 cm³ on sCTA, p = 0.04; 17.2 vs. 97.8 cm³ on mCTA, p < 0.01). However, only good CC on mCTA was associated with lower 24-hour (5 vs. 8.5, p = 0.04) and median discharge NIHSS (2 vs. 4.5, p = 0.04) scores and functional independency (mRS score <3) at 3 months (76.9 vs. 23.1%, p < 0.01). In a logistic regression model including age, NIHSS, ASPECTS and recanalization, only age (OR 0.96, 95% CI 0.93-0.99, p = 0.02) and good CC on mCTA (OR 5, 95% CI 1.99-12.6, p < 0.01) were independent predictors of functional outcome at 3 months.

CONCLUSION

CC evaluation by mCTA is a better prognostic marker than CC evaluation by sCTA for clinical and functional endpoints in acute stroke patients treated with endovascular thrombectomy.

Intravenous Thrombolysis and Passes of Thrombectomy as Predictors for Endovascular Revascularization in Ischemic Stroke

BACKGROUND

Patient selection for endovascular revascularization treatment (ERT) in acute ischemic stroke depends on the expected benefit-risk ratio. As rapid revascularization is a major determinant of good functional outcome, we aimed to identify its predictors after ERT.

METHODS

Consecutive stroke patients from a single stroke center with distal internal carotid artery-, proximal middle cerebral artery- or T-occlusions treated with ERT were retrospectively selected. We assessed admission noncontrast computed tomography and computed tomography angiography for thrombus location, thrombus load (clot burden score), and collateral status. Clinical data were extracted from medical charts. Univariate and multivariate regression analyses were performed to identify predictors of revascularization (thrombolysis in cerebral infarction ≥2b) after ERT.

RESULTS

A total of 63 patients were identified (median age, 73 years; interquartile range: 62-77; 40 females). Sixteen patients (25.4%) underwent intravenous thrombolysis (ivT) before ERT. Twenty-two patients (34.9%) had additional intra-arterial application of recombinant tissue plasminogen activator. The overall recanalization rate was 66.7%, and 9.5% had symptomatic intracranial bleeding. In-hospital mortality was 15%, and 30% reached good functional outcome at discharge. In the univariate analysis, preceding ivT and the number of passes for thrombectomy (dichotomized ≤2 versus >2) were associated with recanalization. There was a trend for number of thrombectomy passes (as continuous variable) and multimodal ERT. In the multivariate regression analysis, ivT prior to ERT and passes of thrombectomy were identified as independent predictors for recanalization.

CONCLUSION

ivT and lower passes of thrombectomy are associated with recanalization after ERT for ischemic stroke with proximal vessel occlusions.

Determinants of leptomeningeal collateral flow in stroke patients with a middle cerebral artery occlusion

Introduction

Poor leptomeningeal collateral flow is related to worse clinical outcome in acute ischemic stroke, but the factors that determine leptomeningeal collateral patency are largely unknown. We explored the determinants of leptomeningeal collateral flow and assessed their effect on the relation between leptomeningeal collateral flow and clinical outcome.

Methods

We included 484 patients from the Dutch acute stroke study (DUST) with a middle cerebral artery (MCA) occlusion. The determinants of poor leptomeningeal collateral flow (≤50 % collateral filling) were identified with logistic regression. We calculated the relative risk (RR) of poor leptomeningeal collateral flow in relation to poor clinical outcome (90-day modified Rankin Scale 3–6) using Poisson regression and assessed whether the determinants of leptomeningeal collateral flow affected this relation.

Results

Leptomeningeal collateral flow was poor in 142 patients (29 %). In multivariable analyses, higher admission glucose level (odds ratio (OR) 1.1 per mmol/L increase (95 % CI 1.0–1.2)), a proximal MCA occlusion (OR 1.9 (95 % CI 1.3–3.0)), and an incomplete posterior circle of Willis (OR 1.7 (95 % CI 1.1–2.6)) were independently related to poor leptomeningeal collateral flow. Poor leptomeningeal collateral flow was related to poor clinical outcome (unadjusted RR 1.7 (95 % CI 1.4–2.0)), and this relation was not affected by the determinants of leptomeningeal collateral flow.

Conclusion

Our study shows that admission glucose level, a proximal MCA occlusion, and an incomplete ipsilateral posterior circle of Willis are determinants of leptomeningeal collateral flow that represent a combination of congenital, acquired, and acute factors. After adjustment for these determinants, leptomeningeal collateral flow remains related to clinical outcome.

Comparison of CTA- and DSA-Based Collateral Flow Assessment in Patients with Anterior Circulation Stroke

BACKGROUND AND PURPOSE

Collateral flow is associated with clinical outcome after acute ischemic stroke and may serve as a parameter for patient selection for intra-arterial therapy. In clinical trials, DSA and CTA are 2 imaging modalities commonly used to assess collateral flow. We aimed to determine the agreement between collateral flow assessment on CTA and DSA and their respective associations with clinical outcome.

MATERIALS AND METHODS

Patients randomized in MR CLEAN with middle cerebral artery occlusion and both baseline CTA images and complete DSA runs were included. Collateral flow on CTA and DSA was graded 0 (absent) to 3 (good). Quadratic weighted κ statistics determined agreement between both methods. The association of both modalities with mRS at 90 days was assessed. Also, association between the dichotomized collateral score and mRS 0-2 (functional independence) was ascertained.

RESULTS

Of 45 patients with evaluable imaging data, collateral flow was graded on CTA as 0, 1, 2, 3 for 3, 10, 20, and 12 patients, respectively, and on DSA for 12, 17, 10, and 6 patients, respectively. The κ-value was 0.24 (95% CI, 0.16-0.32). The overall proportion of agreement was 24% (95% CI, 0.12-0.38). The adjusted odds ratio for favorable outcome on mRS was 2.27 and 1.29 for CTA and DSA, respectively. The relationship between the dichotomized collateral score and mRS 0-2 was significant for CTA (P = .01), but not for DSA (P = .77).

CONCLUSIONS

Commonly applied collateral flow assessment on CTA and DSA showed large differences, indicating that these techniques are not interchangeable. CTA was significantly associated with mRS at 90 days, whereas DSA was not.

Collateral blood vessels in acute ischemic stroke: a physiological window to predict future outcomes

Collateral circulation is a physiologic pathway that protects the brain against ischemic injury and can potentially bypass the effect of a blocked artery, thereby influencing ischemic lesion size and growth. Several recent stroke trials have provided information about the role of collaterals in stroke pathophysiology, and collateral perfusion has been recognized to influence arterial recanalization, reperfusion, hemorrhagic transformation, and neurological outcomes after stroke. Our current aim is to summarize the anatomy and physiology of the collateral circulation and to present and discuss a comprehensible review of the related knowledge, particularly the effects of collateral circulation on the time course of ischemic injury and stroke severity, as well as imaging findings and therapeutic implications.

Imaging Findings Associated with Space-Occupying Edema in Patients with Large Middle Cerebral Artery Infarcts

BACKGROUND AND PURPOSE

Prominent space-occupying cerebral edema is a devastating complication occurring in some but not all patients with large MCA infarcts. It is unclear why differences in the extent of edema exist. Better knowledge of factors related to prominent edema formation could aid treatment strategies. This study aimed to identify variables associated with the development of prominent edema in patients with large MCA infarcts.

MATERIALS AND METHODS

From the Dutch Acute Stroke Study (DUST), 137 patients were selected with large MCA infarcts on follow-up NCCT (3 ± 2 days after stroke onset), defined as ASPECTS ≤4. Prominent edema was defined as a midline shift of ≥5 mm on follow-up. Admission patient and treatment characteristics were collected. Admission CT parameters used were ASPECTS on NCCT and CBV and MTT maps, and occlusion site, clot burden, and collaterals on CTA. Permeability on admission CTP, and day 3 recanalization and reperfusion statuses were obtained if available. Unadjusted and adjusted (age and NIHSS) odds ratios were calculated for all variables in relation to prominent edema.

RESULTS

Prominent edema developed in 51 patients (37%). Adjusted odds ratios for prominent edema were higher with lower ASPECTS on NCCT (adjusted odds ratio, 1.32; 95% CI, 1.13-1.55) and CBV (adjusted odds ratio, 1.26; 95% CI, 1.07-1.49), higher permeability (adjusted odds ratio, 2.35; 95% CI, 1.30-4.24), more proximal thrombus location (adjusted odds ratio, 3.40; 95% CI, 1.57-7.37), higher clot burden (adjusted odds ratio, 2.88; 95% CI, 1.11-7.45), and poor collaterals (adjusted odds ratio, 3.93; 95% CI, 1.78-8.69).

CONCLUSIONS

Extensive proximal occlusion, poor collaterals, and larger ischemic deficits with higher permeability play a role in the development of prominent edema in large MCA infarcts.

Multimodal CT techniques for cerebrovascular and hemodynamic evaluation of ischemic stroke: occlusion, collaterals, and perfusion

Neuroimaging of cerebrovascular status and hemodynamics has vastly improved our understanding of stroke mechanisms and provided information for therapeutic decision-making. CT techniques are the most commonly used techniques due to wide availability, rapid acquisition and acceptable tolerance. Numerous multimodal CT techniques have been developed in the last few years. We summarize and explain the various multimodal CT acquisition techniques within three categories based on the scanning mode, namely static mode (single-phase CTA), multiple static mode (multi-phase CTA) and continuous mode (CT perfusion and dynamic CTA). Post-processing methods based on different acquisition modes are also introduced in an easy manner by focusing on the information extracted and products generated. We also describe the applications for these techniques along with their advantages and disadvantages.

Assessment of Collateral Status by Dynamic CT Angiography in Acute MCA Stroke: Timing of Acquisition and Relationship with Final Infarct Volume

BACKGROUND AND PURPOSE

Dynamic CTA is a promising technique for visualization of collateral filling in patients with acute ischemic stroke. Our aim was to describe collateral filling with dynamic CTA and assess the relationship with infarct volume at follow-up.

MATERIALS AND METHODS

We selected patients with acute ischemic stroke due to proximal MCA occlusion. Patients underwent NCCT, single-phase CTA, and whole-brain CT perfusion/dynamic CTA within 9 hours after stroke onset. For each patient, a detailed assessment of the extent and velocity of arterial filling was obtained. Poor radiologic outcome was defined as an infarct volume of ≥70 mL. The association between collateral score and follow-up infarct volume was analyzed with Poisson regression.

RESULTS

Sixty-one patients with a mean age of 67 years were included. For all patients combined, the interval that contained the peak of arterial filling in both hemispheres was between 11 and 21 seconds after ICA contrast entry. Poor collateral status as assessed with dynamic CTA was more strongly associated with infarct volume of ≥70 mL (risk ratio, 1.9; 95% CI, 1.3-2.9) than with single-phase CTA (risk ratio, 1.4; 95% CI, 0.8-2.5). Four subgroups (good-versus-poor and fast-versus-slow collaterals) were analyzed separately; the results showed that compared with good and fast collaterals, a similar risk ratio was found for patients with good-but-slow collaterals (risk ratio, 1.3; 95% CI, 0.7-2.4).

CONCLUSIONS

Dynamic CTA provides a more detailed assessment of collaterals than single-phase CTA and has a stronger relationship with infarct volume at follow-up. The extent of collateral flow is more important in determining tissue fate than the velocity of collateral filling. The timing of dynamic CTA acquisition in relation to intravenous contrast administration is critical for the optimal assessment of the extent of collaterals.

The Role of Dynamic Contrast-Enhanced MR in Evaluating Level III Collateral Circulation in a Rat Model of Acute Ischemic Stroke

The study aimed to investigate the correlations between parameters of permeability magnetic resonance (MR) and the intensity of vasculature in the focal ischemic cortex of a rat model of middle cerebral artery occlusion. In the present study, sham operation or ischemic-reperfusion with tissue plasminogen activator (tPA) thrombolysis were performed in rats. Cranial MR scans and brain tissue samples were obtained from all animals. Brain slices were stained for immunohistological analyses with confocal fluorescence microscopy, and the intensities of microvessels and capillaries were calculated. Consistency between collateral circulation imaging classification and pathological vascular density was analyzed. We found that the K ^trans value and capillary intensity have the similar trends of declining and increasing, according to different time points, if compared with the sham operation group (P < 0.05). Permeability parameters have better correlations with capillary intensity, and K ^trans value had the best correlation at 4.5 h (kappa = 0.764, P < 0.001), while injection area under curve (IAUC) at 7 days (kappa = 0.725, P < 0.001). Susceptibility-weighted imaging (SWI) exhibited better correlation with microvessel intensity at both 3 days (kappa = 0.715, P < 0.001) and 7 days (kappa = 0.719, P < 0.001). In conclusion, the permeability parameters, such as IAUC and K ^trans map, can quantitatively assess capillary intensity, which may indicate angiogenesis categorized as level III collateral circulation after ischemic stroke.

Differentiating Carotid Terminus Occlusions into Two Distinct Populations Based on Willisian Collateral Status

Background and Purpose

The outcomes of acute internal carotid artery (ICA) terminus occlusions are poor. We classified ICA terminus occlusions into 2 groups according to the occlusion pattern of the circle of Willis and hypothesized that clinical outcomes would significantly differ between them.

Methods

Consecutive patients with acute ICA terminus occlusions evaluated by baseline computed tomographic angiography were enrolled. We investigated the occlusion patterns in the circle of Willis, retrospectively classified patients into simple ICA terminus occlusion (STO; with good Willisian collaterals from neighboring cerebral circulation) and complex ICA terminus occlusion (CTO; with one or more of A2 anterior cerebral artery, fetal posterior cerebral artery occlusion, or hypoplastic/absent contralateral A1; or with poor collaterals from anterior communicating artery) groups, and compared their baseline characteristics and outcomes.

Results

The STO group (n=58) showed smaller infarct volumes at 72 hours than the CTO group (n=34) (median, 81 mL [interquartile range, 38-192] vs. 414 mL [193-540], P<0.001) and more favorable outcomes (3-month modified Rankin Scale 0-3, 44.8% vs. 8.8%, P<0.001; 3-month mortality, 24.1% vs. 67.6%, P<0.001). In multivariable analyses, STO remained an independent predictor for favorable outcomes (odds ratio 6.1, P=0.010).

Conclusions

Favorable outcomes in STO group suggested that the outcomes of acute ICA terminus occlusions depend on Willisian collateral status. Documenting the subtypes on computed tomographic angiography would help predict patient outcome.

CT angiography and CT perfusion improve prediction of infarct volume in patients with anterior circulation stroke

Introduction

We investigated whether baseline CT angiography (CTA) and CT perfusion (CTP) in acute ischemic stroke could improve prediction of infarct presence and infarct volume on follow-up imaging.

Methods

We analyzed 906 patients with suspected anterior circulation stroke from the prospective multicenter Dutch acute stroke study (DUST). All patients underwent baseline non-contrast CT, CTA, and CTP and follow-up non-contrast CT/MRI after 3 days. Multivariable regression models were developed including patient characteristics and non-contrast CT, and subsequently, CTA and CTP measures were added. The increase in area under the curve (AUC) and R² was assessed to determine the additional value of CTA and CTP.

Results

At follow-up, 612 patients (67.5 %) had a detectable infarct on CT/MRI; median infarct volume was 14.8 mL (interquartile range (IQR) 2.8–69.6). Regarding infarct presence, the AUC of 0.82 (95 % confidence interval (CI) 0.79–0.85) for patient characteristics and non-contrast CT was improved with addition of CTA measures (AUC 0.85 (95 % CI 0.82–0.87); p < 0.001) and was even higher after addition of CTP measures (AUC 0.89 (95 % CI 0.87–0.91); p < 0.001) and combined CTA/CTP measures (AUC 0.89 (95 % CI 0.87–0.91); p < 0.001). For infarct volume, adding combined CTA/CTP measures (R² = 0.58) was superior to patient characteristics and non-contrast CT alone (R² = 0.44) and to addition of CTA alone (R² = 0.55) or CTP alone (R² = 0.54; all p < 0.001).

Conclusion

In the acute stage, CTA and CTP have additional value over patient characteristics and non-contrast CT for predicting infarct presence and infarct volume on follow-up imaging. These findings could be applied for patient selection in future trials on ischemic stroke treatment.

Electronic supplementary material

The online version of this article (doi:10.1007/s00234-015-1636-z) contains supplementary material, which is available to authorized users.

Impact of Collateral Status Evaluated by Dynamic Computed Tomographic Angiography on Clinical Outcome in Patients With Ischemic Stroke

Background and Purpose—

Status of collateral circulation is a strong predictor of outcome after acute ischemic stroke. Our aim was to compare the predictive value of strategies for collateral blood flow assessment with dynamic computed tomographic angiography (CTA) and conventional single-phase CT angiography.

Methods—

Patients with a proximal middle cerebral artery occlusion underwent noncontrast CT, single-phase CTA and whole brain CT perfusion/dynamic CTA within 9 hours after stroke onset. We defined poor outcome as a score on the modified Rankin Scale score of ≥3. The association between collateral score and clinical outcome at 3 months was analyzed with Poisson regression. The prognostic value of collateral scoring with dynamic CTA and single-phase CTA in addition to age, stroke severity, and noncontrast CT was assessed with logistic regression and summarized with the area under the curve.

Results—

Seventy patients were included, with a mean age of 68 years. We observed an increased risk of poor outcome in patients with poor collaterals on single-phase CTA (risk ratio, 1.8; 95% confidence interval, 1.0–3.1) and on dynamic CTA (risk ratio, 2.0; 95% confidence interval, 1.5–2.7). The prediction of poor clinical outcome by means of collateral adjustment was better with dynamic CTA (area under the curve, 0.84; likelihood ratio test P <0.01) than by single-phase CTA (area under the curve, 0.80; likelihood ratio test P =0.33).

Conclusions—

Collateral assessment with dynamic CTA better predicts clinical outcome at 3 months than single-phase conventional CTA.

Clinical Trial Registration—

URL: http://www.trialregister.nl/trialreg . Unique identifier: NTR1804. URL: http://www.clinicaltrials.gov . Unique identifier: NCT00880113.

The emerging age of endovascular treatment of acute ischaemic stroke and the role of CT angiography in patient work-up: a guide for the radiologist

Recent trial evidence suggests that for patients suffering large-vessel occlusive stroke, endovascular therapy based on the stent-retriever technique is associated with superior clinical outcomes when compared to intravenous thrombolysis alone. The challenge now is how this service is to be delivered. This may involve both centralisation of services around large cities and development of robust networks to receive patients from district general hospitals situated further afield. Both diagnostic and interventional neuroradiology will need to expand. Furthermore, we suggest that it would be advantageous for radiology departments in those hospitals receiving hyperacute stroke patients to perform computed tomography (CT) angiography in addition to non-contrast CT, which also has implications for service delivery in these units. This could swiftly aid identification of patients who might benefit from thrombectomy and improve decision-making through demonstration of occlusive thrombus and of collateral status.

Influence of Recanalization and Time of Cerebral Ischemia on Tissue Outcome after Endovascular Stroke Treatment on Computed Tomography Perfusion

BACKGROUND

The Alberta Stroke Program Early Computed Tomography Score (ASPECTS) has been proposed as a straightforward alternative to the less reliable visual estimation of tissue at risk. We evaluated the association between admission ASPECTS on computed tomography perfusion (CTP) parameter maps and final infarct ASPECTS in patients with acute ischemic stroke who were treated by endovascular therapy (eT) and compared the results with thrombolysis candidates treated conservatively.

METHODS

eT was performed in 26 consecutive ischemic stroke patients within 6 hours of symptom onset. The control group was matched for age and admission National Institutes of Health Stroke Scale having the same admission imaging protocol and a transcranial Doppler sonography within 24 hours. ASPECTS determined from CTP maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and time to peak (TTP) were compared with final infarct ASPECTS on day 5 noncontrast CT.

RESULTS

Recanalization rate was 73% in treatment and 50% in control group. ASPECTS for all CTP parameters were significantly lower than ASPECTS-CT in both groups (P < .005). In the treatment group, this applied to patients with successful recanalization. Only controls without recanalization showed a strong correlation between ASPECTS-CTP parameters and ASPECTS-CT (CBV: P = .005; CBF and TTP: P = .028). Patients with early recanalization (≤4 hours) had greater differences between ASPECTS-CTP and ASPECTS-CT than patients with late recanalization (>4 hours; CBF: P = .056; CBV: P = .095; TTP: P = .048).

CONCLUSIONS

The initial ASPECTS-CTP lesion was significantly larger than the final infarct determined by ASPECTS in case of recanalization. Initial perfusion lesion, including CBV, is reversible in case of reperfusion, especially in early reperfusion.