Clinical-diffusion mismatch defined by NIHSS and ASPECTS in non-lacunar anterior circulation infarction

Core and penumbra estimation using deep learning-based AIF in association with clinical measures in computed tomography perfusion (CTP)

OBJECTIVES

To investigate whether utilizing a convolutional neural network (CNN)-based arterial input function (AIF) improves the volumetric estimation of core and penumbra in association with clinical measures in stroke patients.

METHODS

The study included 160 acute ischemic stroke patients (male = 87, female = 73, median age = 73 years) with approval from the institutional review board. The patients had undergone CTP imaging, NIHSS and ASPECTS grading. convolutional neural network (CNN) model was trained to fit a raw AIF curve to a gamma variate function. CNN AIF was utilized to estimate the core and penumbra volumes which were further validated with clinical scores.

RESULTS

Penumbra estimated by CNN AIF correlated positively with the NIHSS score (r = 0.69; p < 0.001) and negatively with the ASPECTS (r =  - 0.43; p < 0.001). The CNN AIF estimated penumbra and core volume matching the patient symptoms, typically in patients with higher NIHSS (> 20) and lower ASPECT score (< 5). In group analysis, the median CBF < 20%, CBF < 30%, rCBF < 38%, Tmax > 10 s, Tmax > 10 s volumes were statistically significantly higher (p < .05).

CONCLUSIONS

With inclusion of the CNN AIF in perfusion imaging pipeline, penumbra and core estimations are more reliable as they correlate with scores representing neurological deficits in stroke.

CRITICAL RELEVANCE STATEMENT

With CNN AIF perfusion imaging pipeline, penumbra and core estimations are more reliable as they correlate with scores representing neurological deficits in stroke.

NIHSS-the Alberta Stroke Program Early CT Score mismatch in guiding thrombolysis in patients with acute ischemic stroke

Objective

This study investigates the mismatch between the National Institutes of Health Stroke Scale (NIHSS) score and the computed tomography (CT) findings measured by the Alberta Stroke Program Early CT Score (ASPECTS) for predicting the functional outcome and safety of intravenous thrombolysis (IVT) treatment in patients with acute ischemic stroke (AIS).

Methods

This prospective observational study includes patients with AIS who underwent CT imaging within 4.5 h of the onset of symptoms. Patients were divided into the NIHSS–ASPECTS mismatch (NAM)-positive and NAM-negative groups (group P and N, respectively). The clinical outcome was assessed using the Modified Rankin Scale (mRS). Safety outcomes included progression, symptomatic intracerebral hemorrhage (sICH), intracerebral hemorrhage (ICH), adverse events, clinical adverse events, and mortality.

Results

A total of 208 patients were enrolled in the study. In group P, IVT treatment was associated with a good functional outcome at 3 months (p = 0.005) and 1 year (p = 0.001). A higher percentage of patients with favorable mRS (0–2) (p = 0.01) and excellent mRS (0–1) (p = 0.011) functional outcomes was obtained at 1 year in group P with IVT treatment. Group N did not benefit from the same treatment (p = 0.352 and p = 0.480 at 3 months and 1 year, respectively). There were no statistically significant differences in sICH, ICH, mortality rates, or other risks between the IVT and conventional treatment groups.

Conclusion

IVT treatment is associated with a good functional outcome in patients with NAM, without increasing the risks of sICH, ICH, mortality, or other negative outcomes. NAM promises to be an easily obtained indicator for guiding the treatment decisions of AIS.

Clinical-CT mismatch defined NIHSS ≥ 8 and CT-ASPECTS ≥ 9 as a reliable marker of candidacy for intravenous thrombolytic therapy in acute ischemic stroke

Background

Clinical-diffusion mismatch between stroke severity and diffusion-weighted imaging lesion volume seems to identify stroke patients with penumbra. However, urgent magnetic resonance imaging is sometimes inaccessible or contraindicated. Thus, we hypothesized that using brain computed tomography (CT) to determine a baseline “clinical-CT mismatch” may also predict the responses to thrombolytic therapy.

Methods

Brain CT lesions were measured using the Alberta Stroke Program Early CT Score (ASPECTS). A total of 104 patients were included: 79 patients with a baseline National Institutes of Health Stroke Scale (NIHSS) score ≥ 8 and a CT-ASPECTS ≥ 9 who were defined as clinical-CT mismatch-positive (P group) and 25 patients with an NIHSS score ≥ 8 and a CT-ASPECTS < 9 who were defined as clinical-CT mismatch-negative (the N group). We compared their clinical outcomes, including early neurological improvement (ENI), early neurological deterioration (END), delta NIHSS score (admission NIHSS—baseline NIHSS score), symptomatic intracranial hemorrhage (sICH), mortality, and favorable outcome at 3 months.

Results

Patients in the P group had a greater proportion of favorable outcome at 3 months (p = 0.032) and more frequent ENI (p = 0.038) and a greater delta NIHSS score (p = 0.001), as well as a lower proportion of END (p = 0.004) than those in the N group patients. There were no significant differences in the incidence rates of sICH and mortality between the two groups.

Conclusions

Clinical-CT mismatch may be able to predict which patients would benefit from intravenous thrombolysis.

Neuroimaging Paradigms to Identify Patients for Reperfusion Therapy in Stroke of Unknown Onset

Despite the proven efficacy of intravenous alteplase or endovascular thrombectomy for the treatment of patients with acute ischemic stroke, only a minority receive these treatments. This low treatment rate is due in large part to delay in hospital arrival or uncertainty as to the exact time of onset of ischemic stroke, which renders patients outside the current guideline-recommended window of eligibility for receiving these therapeutics. However, recent pivotal clinical trials of late-window thrombectomy now force us to rethink the value of a simplistic chronological formulation that “time is brain.” We must recognize a more nuanced concept that the rate of tissue death as a function of time is not invariant, that still salvageable tissue at risk of infarction may be present up to 24 h after last-known well, and that those patients may strongly benefit from reperfusion. Multiple studies have sought to address this clinical dilemma using neuroimaging methods to identify a radiographic time-stamp of stroke onset or evidence of salvageable ischemic tissue and thereby increase the number of patients eligible for reperfusion therapies. In this review, we provide a critical analysis of the current state of neuroimaging techniques to select patients with unwitnessed stroke for revascularization therapies and speculate on the future direction of this clinically relevant area of stroke research.

Angioplasty and stenting for symptomatic extracranial non-tandem internal carotid artery occlusion

Introduction

Symptomatic internal carotid artery occlusion (ICAO) can lead to neurologic decline, recurrent stroke, and mortality.

Objective

We sought to evaluate the safety and feasibility of endovascular revascularization for ICAO without tandem intracranial large vessel occlusion (LVO).

Design, setting, and participants

This is a retrospective cohort analysis of all patients presenting to a single academic center with ischemic stroke and ipsilateral cervical ICAO from November 2003 through April 2016. Patients were excluded if pre-procedural angiography demonstrated tandem LVO or if patients were known to have chronic ICAO.

Main outcome(s) and measure(s)

Study endpoints included discharge neurologic examination, post-procedural infarct burden, 3-month functional outcomes, and treatment durability.

Results

A total of 107 patients with symptomatic angiographically-confirmed cervical ICAO without tandem LVO were identified. Median admission NIH Stroke Scale (NIHSS) score was 8 (IQR 11). Baseline radiographic stroke severity was assessed by ASPECT score (median 9; IQR 2), perfusion mismatch (present in 93%), and clinical imaging mismatch (42%). Median time from symptom onset to treatment was 25 hours (IQR 61). Successful revascularization was achieved in 92% of patients. At discharge, 83% had stable/improved NIHSS score, while at 3 months 65% achieved independence (modified Rankin Scale score ≤2). The most common complication was distal embolization (22%) of which 16% required intra-arterial treatment. Rate of significant restenosis (≥70%) was 15% at 1 year.

Conclusions

Stenting in selected patients at risk of neurologic deterioration due to symptomatic ICAO can be performed with high rates of technical success and good clinical outcomes. Because of significant peri-procedural risks and high rates of restenosis, randomized studies are necessary to understand the benefit of this approach.

Effect of Collaterals on Clinical Presentation, Baseline Imaging, Complications, and Outcome in Acute Stroke

BACKGROUND AND PURPOSE

Good CTA collaterals independently predict good outcome in acute ischemic stroke. Our aim was to evaluate the role of collateral circulation and its added benefit over CTP-derived total ischemic volume as a predictor of baseline NIHSS score, total ischemic volume, hemorrhagic transformation, final infarct size, and a modified Rankin Scale score >2.

MATERIALS AND METHODS

This was a retrospective study of 395 patients with stroke dichotomized by recanalization (recanalization positive/recanalization negative) and collateral status. Clot burden score was quantified on baseline CTA. Total ischemic volumes were derived from thresholded CTP maps. Final infarct size was assessed on follow-up CT/MRI. We performed uni-/multivariate analyses for each outcome, adjusting for rtPA status, using general linear (continuous variables) and logistic (binary variables) regression. Model comparison with collateral score and total ischemic volume was performed using the F or likelihood ratio test.

RESULTS

Collateral presence independently and inversely predicted all outcomes except hemorrhagic transformation in patients who were recanalization negative and mRS >2 in patients who were recanalization positive. The greatest collateral benefit occurred in patients who were recanalization negative, contributing 16.5% and 19.2% of the variability for final infarct size and mRS >2. The collateral score model is superior to the total ischemic volume for mRS >2 prediction, but a combination of total ischemic volume and collateral score is superior for mRS >2 and final infarct prediction (24% and 28% variability, respectively). In patients who were recanalization positive, a model including collateral score and total ischemic volume was superior to that of total ischemic volume for hemorrhagic transformation and final infarct prediction but was muted compared with patients who were recanalization negative (11.3% and 16.9% variability).

CONCLUSIONS

Collateral circulation is an independent predictor of all outcomes, but the magnitude of significance varies, greater in patients who were recanalization negative versus recanalization positive. Total ischemic volume assessment is complementary to collateral score in many cases.

Acute Stroke Imaging Part II: The Ischemic Penumbra

In acute ischemic stroke, the volume of threatened but potentially salvageable tissue, i.e. the ischemic penumbra, is critical to the success of all acute therapeutic interventions, most notably thrombolysis. Despite the availability of both CT and MRI based techniques to detect and assess the penumbra, advanced imaging of this type remains under-utilized. Although the optimal selection criteria are still being refined and technical improvements are ongoing, rapid imaging of the penumbra appears to be the most promising approach to expanding the acute thrombolysis population, as well as tailoring treatment based on specific pathophysiological findings. This second article in a two-part series reviews current evidence for penumbral-based treatment selection and discusses the barriers to implementation of these advanced imaging techniques in acute stroke management protocols.

Emergent surgical embolectomy for middle cerebral artery occlusion due to carotid plaque rupture followed by elective carotid endarterectomy

Embolic intracranial large artery occlusion with severe neurological deficit is associated with an extremely poor prognosis. The safest and most effective treatment strategy has not yet been determined when such emboli are associated with unstable proximal carotid plaque. The authors performed emergent surgical embolectomy for left middle cerebral artery (MCA) occlusion, and the patient experienced marked neurological recovery without focal deficit and regained premorbid activity. Postoperative investigation revealed “vulnerable plaque” of the left internal carotid artery without apparent evidence of cardiac embolism, such as would be seen with atrial fibrillation. Specimens from subsequent elective carotid endarterectomy (CEA) showed ruptured vulnerable plaque that was histologically consistent as a source of the intracranial embolic specimen. Surgical embolectomy for MCA occlusion due to carotid plaque rupture followed by CEA could be a safer and more effective alternative to endovascular treatment from the standpoint of obviating the risk of secondary embolism that could otherwise occur as a result of the manipulation of devices through an extremely unstable portion of plaque. Further, this strategy is associated with a high probability of complete recanalization with direct removal of hard and large, though fragile, emboli.

Interleukin-10 facilitates the selection of patients for systemic thrombolysis

BACKGROUND

Clinical-Diffusion mismatch (CDM; NIHSS score ≥8 & DWI lesion volume ≤25 mL) and Perfusion-Diffusion mismatch (PDM; difference >20% between initial DWI and MTT lesion volumes) have been proposed as surrogates for ischemic brains that are at risk of infarction. However, their utility to improve the selection of patients for thrombolytic treatment remains controversial. Our aim was to identify molecular biomarkers that can be used with neuroimaging to facilitate the selection of ischemic stroke patients for systemic thrombolysis.

METHODS

We prospectively studied 595 patients with ischemic stroke within 12 h of the stroke onset. A total of 184 patients received thrombolytic treatment according to the SITS-MOST criteria. DWI and MTT volumes were measured at admission. The main outcome variable was good functional outcome at 3 months (modified Rankin scale <3). Serum levels of glutamate (Glu), IL-10, TNF-α, IL-6, NSE, and active MMP-9 also were determined at admission.

RESULTS

Patients treated with t-PA who presented with PDM had higher IL-10 levels at admission (p < 0.0001). In contrast, patients with CDM had higher levels of IL-10 (p < 0.0001) as well as Glu and TNF-α (all p < 0.05) and lower levels of NSE and active MMP-9 (all p < 0.0001). IL-10 ≥ 30 pg/mL predicts good functional outcome at 3 months with a specificity of 88% and a sensitibity of 86%. IL-10 levels ≥30 pg/mL independently in both patients with PDM (OR, 18.9) and CDM (OR, 7.5), after an adjustment for covariates.

CONCLUSIONS

Serum levels of IL-10 facilitate the selection of ischemic stroke patients with CDM and PDM for systemic thrombolysis.

Clinical-radiological severity mismatch phenomenon: patients with severe neurological deficits without matching infarction on computed tomographic scan

OBJECTIVE

The objective was to determine the long-term outcome of patients with severe persistent neurological deficits without a large infarction on computed tomographic (CT) scan.

METHODS

We analyzed the prospectively collected data as part of the randomized, placebo controlled trial in patients with ischemic stroke presenting within 3 hours of symptom onset. Volume of infarction was measured from CT scan acquired at 3 months. Favorable outcome defined by no significant or slight disability on a modified Rankin scale at 12 months. We determined the outcome of patients with National Institutes of Health Stroke Scale score (NIHSS score) ≥ 10 at 24 hours.

RESULTS

Of the 277 patients with NIHSS score ≥ 10 at 24 hours, 88 (32%) met the criteria of clinical-radiological severity mismatch. Compared with patients with NIHSS score ≥ 10 with infarct volume ≥ 20 cc, the patients with NIHSS score ≥ 10 and infarct volume <20 cc were older but there were no differences in the gender, race or vascular risk factors. Patients with clinical-radiological severity mismatch were more likely to have a favorable outcome at 12 months compared with those without mismatch (odd ratio 4.3, 95% confidence interval 1.5-12.6, P = .0063) after adjusting for potential confounders.

CONCLUSIONS

We observed that approximately one-fourth of patients with severe neurological deficits have clinical-radiological severity mismatch. Such patients appear to have a high rate of favorable outcomes at 1 year.

Endovascular recanalisation therapy for prolonged basilar artery occlusion based on clinical-diffusion MRI mismatch

OBJECTIVES

Clinical-diffusion magnetic resonance imaging (MRI) mismatch (CDM) in patients with anterior circulation occlusions is an optional method used to select patients for recanalisation outside the 3-h time window. A similar concept has not been reported with posterior circulation occlusions.

METHODS

CDM was defined as a Glasgow Coma Scale (GCS) score <8 with DWI lesions not located in the dorsal pons, midbrain or thalamus at the time of admission. Eligible patients were treated with endovascular recanalisation therapy (ERT). The treatment included intra-arterial rt-PA thrombolysis and angioplasty and stenting performed separately or combined. The recanalisation result was assessed by angiography immediately after the treatment according to the trial reports in the Thrombolysis in Myocardial Infarction Criteria (TIMI). The complications and outcome 3 months later were recorded.

RESULTS

Nine patients with a mean age of 66.6 years were included in the study (7 men and 2 women). The median durations of clinical presentation and coma were 31 h (range 25-53 h) and 6 h (range 2-13 h). The median GCS score at admission was 6 (range 4-7). Occlusions were located in the proximal basilar artery (BA) (n=2) and the middle BA (n=7). ERT was successful in 8 patients (TIMI 2, n=2 and TIMI 3, n=6) but failed in 1 patient because recanalisation was not possible (TIMI 0). No intracranial haemorrhage or dissections occurred during treatment. The recanalised patients recovered consciousness within 9-27 h after treatment. The median GCS score upon discharge was 14 (range 3-15). Three months later, 6 patients had a good outcome (modified Rankin Score (mRS) 0-2), and 2 patients had a moderate outcome (mRS 3). The patient who did not undergo recanalisation died in the rehabilitation hospital 21 days later.

CONCLUSIONS

CDM may be a valid method for selecting patients with prolonged basilar artery occlusion (BAO) who are eligible for recanalisation treatment. ERT was feasible for patients with BAO. A good clinical outcome was achieved with successful recanalisation.

Predicting stroke evolution: comparison of susceptibility-weighted MR imaging with MR perfusion

OBJECTIVES

To investigate the ability of susceptibility-weighted imaging (SWI) to predict stroke evolution in comparison with perfusion-weighted imaging (PWI).

METHODS

In a retrospective analysis of 15 patients with non-lacunar ischaemic stroke studied no later than 24 h after symptom onset, we used the Alberta Stroke Program Early CT Score (ASPECTS) to compare lesions on initial diffusion-weighted images (DWI), SWI, PWI and follow-up studies obtained at least 5 days after symptom onset. The National Institutes of Health Stroke Scale scores at entry and stroke risk factors were documented. The clinical-DWI, SWI-DWI and PWI-DWI mismatches were calculated.

RESULTS

SWI-DWI and mean transit time (MTT)-DWI mismatches were significantly associated with higher incidence of infarct growth (P = 0.007 and 0.028) and had similar ability to predict stroke evolution (P = 1.0). ASPECTS values on initial DWI, SWI and PWI were significantly correlated with those on follow-up studies (P ≤ 0.026) but not associated with infarct growth. The SWI ASPECTS values were best correlated with MTT ones (ρ = 0.8, P < 0.001).

CONCLUSIONS

SWI is an alternative to PWI to assess penumbra and predict stroke evolution. Further prospective studies are needed to evaluate the role of SWI in guiding thrombolytic therapy. Key Points • SWI can provide perfusion information comparable to MTT • SWI-DWI mismatch can indicate ischaemic penumbra • SWI-DWI mismatch can be a predictor for stroke evolution.

Clinical stroke penumbra: use of National Institutes of Health stroke scale as a surrogate for CT perfusion in patient triage for intra-arterial middle cerebral artery stroke therapy

BACKGROUND AND PURPOSE

CTP may help triage acute stroke patients for IAT, but requires additional contrast agent, radiation, and imaging time. Our aim was to determine whether clinical examination (NIHSS) with NCCT and CTA can substitute for CTP without significantly affecting IAT triage of patients with acute MCA stroke.

MATERIALS AND METHODS

We reviewed NCCT, CTA, and CTP imaging performed within 8 hours of symptom onset in 36 patients presenting with MCA territory stroke (September 2007-October 2009). Two neuroradiologists reviewed, independently and by consensus, NCCT, CTA, and CTP (CTP group), and 2 different neuroradiologists blinded to CTP reviewed NCCT, CTA, and NIHSS (stroke scale group) to determine IAT eligibility: M1 or proximal M2 occlusion; infarct core <1/3 MCA territory; and ischemic penumbra >20% infarct core. The stroke scale group estimated infarct core from NCCT and CTA source images and ischemic penumbra from core size relative to NIHSS score and re-evaluated patients after unblinding to CTP. We computed intragroup and intergroup κ scores for IAT treatment recommendation and used the McNemar test to determine whether CTP significantly affected the stroke scale group's decisions.

RESULTS

IAT was recommended in 16/36 (44%) and 17/36 (47%) patients by the CTP and stroke scale groups, respectively, with intragroup κ scores of 0.78 ± 0.11 versus 0.83 ± 0.09. The intergroup κ score was 0.83 ± 0.09. When unblinded to CTP, the stroke scale group revised 2/36 (5.6%) decisions, which was insignificant (P = .48, McNemar test).

CONCLUSIONS

NIHSS interpreted with NCCT and CTA may be an effective substitute for CTP-derived measures in the IAT triage of patients with acute MCA stroke. Replacing CTP may potentially reduce radiation and contrast dose and time to treatment.

Magnetic resonance diffusion-perfusion mismatch in acute ischemic stroke: An update

The concept of magnetic resonance perfusion-diffusion mismatch (PDM) provides a practical and approximate measure of the tissue at risk and has been increasingly applied for the evaluation of hyperacute and acute stroke in animals and patients. Recent studies demonstrated that PDM does not optimally define the ischemic penumbra; because early abnormality on diffusion-weighted imaging overestimates the infarct core by including part of the penumbra, and the abnormality on perfusion weighted imaging overestimates the penumbra by including regions of benign oligemia. To overcome these limitations, many efforts have been made to optimize conventional PDM. Various alternatives beyond the PDM concept are under investigation in order to better define the penumbra. The PDM theory has been applied in ischemic stroke for at least three purposes: to be used as a practical selection tool for stroke treatment; to test the hypothesis that patients with PDM pattern will benefit from treatment, while those without mismatch pattern will not; to be a surrogate measure for stroke outcome. The main patterns of PDM and its relation with clinical outcomes were also briefly reviewed. The conclusion was that patients with PDM documented more reperfusion, reduced infarct growth and better clinical outcomes compared to patients without PDM, but it was not yet clear that thrombolytic therapy is beneficial when patients were selected on PDM. Studies based on a larger cohort are currently under investigation to further validate the PDM hypothesis.

The infarct core is well represented by the acute diffusion lesion: sustained reversal is infrequent

Diffusion-weighted imaging (DWI) is commonly used to assess irreversibly infarcted tissue but its accuracy is challenged by reports of diffusion lesion reversal (DLR). We investigated the frequency and implications for mismatch classification of DLR using imaging from the EPITHET (Echoplanar Imaging Thrombolytic Evaluation Trial) and DEFUSE (Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution) studies. In 119 patients (83 treated with IV tissue plasminogen activator), follow-up images were coregistered to acute diffusion images and the lesions manually outlined to their maximal visual extent in diffusion space. Diffusion lesion reversal was defined as voxels of acute diffusion lesion that corresponded to normal brain at follow-up (i.e., final infarct, leukoaraiosis, and cerebrospinal fluid (CSF) voxels were excluded from consideration). The appearance of DLR was visually checked for artifacts, the volume calculated, and the impact of adjusting baseline diffusion lesion volume for DLR volume on perfusion-diffusion mismatch analyzed. Median DLR volume reduced from 4.4 to 1.5 mL after excluding CSF/leukoaraiosis. Visual inspection verified 8/119 (6.7%) with true DLR, median volume 2.33 mL. Subtracting DLR from acute diffusion volume altered perfusion-diffusion mismatch (T(max)>6 seconds, ratio>1.2) in 3/119 (2.5%) patients. Diffusion lesion reversal between baseline and 3 to 6 hours DWI was also uncommon (7/65, 11%) and often transient. Clinically relevant DLR is uncommon and rarely alters perfusion-diffusion mismatch. The acute diffusion lesion is generally a reliable signature of the infarct core.

Collateral blood vessels in acute ischaemic stroke: a potential therapeutic target

Ischaemic stroke results from acute arterial occlusion leading to focal hypoperfusion. Thrombolysis is the only proven treatment. Advanced neuroimaging techniques allow a detailed assessment of the cerebral circulation in patients with acute stroke, and provide information about the status of collateral vessels and collateral blood flow, which could attenuate the effects of arterial occlusion. Imaging of the brain and vessels has shown that collateral flow can sustain brain tissue for hours after the occlusion of major arteries to the brain, and the augmentation or maintenance of collateral flow is therefore a potential therapeutic target. Several interventions that might augment collateral blood flow are being investigated.

Predictive role of modified clinical diffusion mismatch in early neurological deterioration due to atherothrombotic ischemia in the anterior circulation

BACKGROUND

Atherothrombotic ischemia is the most frequent cause of cerebral ischemia; however, few reports have addressed the prognostic factors predicting early neurological deterioration (END) when the occlusive lesion is limited to the anterior main trunk, middle cerebral artery (MCA) or internal cerebral artery (ICA).

METHOD

Between 2006 and 2008, 122 atherothrombotic ischemia patients were diagnosed with MCA or ICA occlusive disease on magnetic resonance angiography. The National Institutes of Health Stroke Scale (NIHSS) score and the modified Alberta Stroke Program Early CT Score on diffusion-weighted imaging [ASPECTS-DW (modified)] were calculated. Clinical-DWI mismatch (CDM) was evaluated using NIHSS and the ASPECTS-DW (modified) to examine the predictive efficacy for early neurological deterioration.

RESULTS

Eighteen of 122 (14.8%) patients fulfilled the definition of CDM. END was observed in 24 patients (19.7%) within 15 days after admission. CDM was observed in 14 cases in the END (+) group (14 of 24 cases, 58.3%) and 4 cases in the END (-) group (4 of 98 cases, 4.1%) (p = 0.001). Multivariate logistic regression analysis demonstrated that CDM was a significant predictive factor of END (odds ratio 26.68, p = 0.0001).

CONCLUSIONS

CDM based on NIHSS and ASPECTS-DW (modified) could be a significant predictive factor for END of atherothrombotic ischemia in MCA/ICA.

Early biomarkers of clinical-diffusion mismatch in acute ischemic stroke

BACKGROUND AND PURPOSE

Clinical-diffusion mismatch (CDM; National Institutes of Health Stroke Scale score≥8 and diffusion-weighted imaging lesion volume<25 mL) has been suggested as a surrogate of ischemic brain at risk of infarction and might be used to recognize salvageable ischemic tissue. Our aim was to identify early biomarkers associated with the presence of CDM.

METHODS

We prospectively evaluated CDM in 226 patients (71.6±11.1 years, 58% men) with hemispheric ischemic stroke within 12 hours from symptom onset (median, 3.6 hours). Diffusion-weighted MRI lesion volume was measured by manual segmentation method. Serum levels of glutamate, aspartate, interleukin-10, tumor necrosis factor-α, interleukin-6, S100β, neuron-specific enolase, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, active matrix metalloproteinase-9, and cellular fibronectin were determined by immunoassay or high-performance liquid chromatography techniques in blood samples obtained at admission.

RESULTS

CDM was found in 61 patients (26.9%). Patients with CDM had higher serum levels of interleukin-10, tumor necrosis factor-α, and glutamate and lower serum levels of neuron-specific enolase, interleukin-6, and active matrix metalloproteinase-9 (all P<0.0001). Binary logistic regression showed that tumor necrosis factor-α≥21 pg/mL (OR, 21), glutamate≥230 μmol/L (OR, 27), neuron-specific enolase≥23 ng/mL (OR, 0.05), interleukin-6≥10 pg/mL (OR, 0.06), and active matrix metalloproteinase-9≥21 ng/mL (OR, 0.28) were independent molecular predictors of CDM after adjustment for covariates. The association of interleukin-10≥23 pg/mL and glutamate≥230 μmol/L levels predicted CDM with a sensitivity of 96% and a specificity of 98%.

CONCLUSIONS

High levels of interleukin-10, tumor necrosis factor-α, and glutamate as well as low levels of neuron-specific enolase, interleukin-6, and active matrix metalloproteinase-9 are associated with CDM.

Significance of clinical-diffusion mismatch in hyperacute cerebral infarction

In recent years, patient selection for intravenous tissue plasminogen activator (t-PA) therapy based on clinical-diffusion mismatch (CDM) has been closely examined. We investigated the relationship between prognosis and CDM in patients with hyperacute cerebral infarction within 3 hours of onset and compared CDM with diffusion-perfusion mismatch (DPM). Of 122 patients with hyperacute cerebral infarction who visited the hospital within 3 hours of onset between April 2007 and November 2008, 85 patients with cerebral infarction in the anterior circulation who underwent head magnetic resonance imaging diffusion-weighted imaging (DWI)/magnetic resonance angiography (MRA) (51 men and 34 women; average age, 74 ± 10 years) were enrolled. Seventeen of these patients underwent CT perfusion imaging. CDM-positive cases were those with a National Institute of Health Stroke Scale (NIHSS) score ≥ 8 and a DWI-Alberta Stroke Program Early CT Score (DWI-ASPECTS) ≥ 8; CDM-negative cases were those with an NIHSS score ≥ 8 and an ASPECTS-DWI < 8. The other patients were classified as belonging to the NIHSS score < 8 group. Of the 32 CDM-positive cases, 10 received t-PA infusion. These patients had markedly higher modified Rankin Scale scores 90 days after onset compared with the 22 patients who did not receive t-PA infusion. The 8 CDM-positive cases included 4 DPM-positive cases and 4 DPM-negative cases, and a discrepancy was confirmed between CDM and DPM. In all DPM-positive cases, MRA confirmed lesions in major intracranial arteries. CDM may enable more accurate prediction of outcomes in patients with hyperacute cerebral infarction. In addition, the combination of CDM findings and MRA findings (stenosis or occlusion in major intracranial arteries) may be an alternative to DPM for determining the indications for IV t-PA therapy in patients with hyperacute cerebral infarction.

ABC/2 for rapid clinical estimate of infarct, perfusion, and mismatch volumes

BACKGROUND

Rapid and easy clinical assessments for volumes of infarction and perfusion mismatch are needed. We tested whether simple geometric models generated accurate estimates of these volumes.

METHODS

Acute diffusion-weighted image (DWI) and perfusion (mean transit time [MTT]) in 63 strokes and established infarct volumes in 50 subacute strokes were measured by computerized planimetry. Mismatch was defined as MTT/DWI > or = 1.2. Observers, blinded to planimetric values, measured lesions in three perpendicular axes A, B, and C. Geometric estimates of sphere, ellipsoid, bicone, and cylinder were compared to planimetric volume by least-squares linear regression.

RESULTS

The ABC/2 formula (ellipsoid) was superior to other geometries for estimating volume of DWI (slope 1.16, 95% confidence interval [CI] 0.94 to 1.38; R(2) = 0.91, p = 0.001) and MTT (slope 1.11, 95% CI 0.99 to 1.23; R(2) = 0.89, p = 0.001). The intrarater and interrater reliability for ABC/2 was high for both DWI (0.992 and 0.965) and MTT (0.881 and 0.712). For subacute infarct, the ABC/2 formula also best estimated planimetric volume (slope 1.00, 95% CI 0.98 to 1.19; R(2) = 0.74, p = 0.001). In general, sphere and cylinder geometries overestimated all volumes and bicone underestimated all volumes. The positive predictive value for mismatch was 92% and negative predictive value was 33%.

CONCLUSIONS

Of the models tested, ABC/2 is reproducible, is accurate, and provides the best simple geometric estimate of infarction and mean transit time volumes. ABC/2 has a high positive predictive value for identifying mismatch greater than 20% and might be a useful tool for rapid determination of acute stroke treatment.

Clinical-diffusion mismatch and benefit from thrombolysis 3 to 6 hours after acute stroke

BACKGROUND AND PURPOSE

The clinical-diffusion mismatch (CDM) model has been proposed as a simpler tool than perfusion-diffusion mismatch (PDM) to select acute ischemic stroke patients for thrombolytic therapy. We hypothesized that in the 3- to 6-hour time window, the effect of tPA was significantly greater in patients with CDM than in patients without CDM.

METHODS

This is a substudy of EPITHET, a double-blind multi-center study of 100 patients randomized to tPA or placebo 3 to 6 hours after stroke onset. MRI was obtained before treatment, and at 3 to 5 days and 90 days after treatment. Presence of PDM (perfusion deficit/DWI(volume) >1.2 and perfusion deficit at least 10 mL>DWI(volume)) and CDM (NIHSS >or=8 and DWI(volume) <or=25 mL) was determined for each patient. We assessed lesion growth and neurological improvement (decrease in NIHSS >or=8 points between baseline and 90 days, or a 90-day NIHSS <or=1).

RESULTS

86% of the patients had PDM, but only 41% had CDM. CDM detected PDM with a sensitivity of 46% and a specificity of 86%. We found statistically significant effects of reperfusion on the rate of neurological improvement (OR 9.92, 95% CI 1.91 to 51.64; P<0.01) and on absolute growth (difference: -59.60 mL, 95% CI -95.40 mL to -23.81 mL; P<0.01). Neither treatment with tPA nor reperfusion had a significantly different impact on lesion growth or clinical course in CDM patients compared to patients without CDM.

CONCLUSIONS

There was no increased benefit from tPA in patients with CDM. The beneficial effects of reperfusion were similar in patients with and without CDM.

Does diffusion-weighted imaging represent the ischemic core? An evidence-based systematic review

BACKGROUND AND PURPOSE

Diffusion-weighted(DWI) hyperintensity is hypothesized to represent irreversibly infarcted tissue (ischemic core) in the setting of acute stroke [corrected]. Measurement of the ischemic core has implications for both prognosis and therapy. We wished to assess the level of evidence in the literature supporting this hypothesis.

MATERIALS AND METHODS

We performed a systematic review of the literature relating to tissue outcomes of DWI hyperintense stroke lesions in humans. The methodologic rigor of studies was evaluated by using criteria set out by the Oxford Centre for Evidence-Based Medicine. Data from individual studies were also analyzed to determine the prevalence of patients demonstrating lesion progression, no change, or lesion regression compared with follow-up imaging.

RESULTS

Limited numbers of highly methodologically rigorous studies (Oxford levels 1 and 2) were available. There was great variability in observed rates of DWI lesion reversal (0%-83%), with a surprisingly high mean rate of DWI lesion reversal (24% of pooled patients). Many studies did not include sufficient data to determine the precise prevalence of DWI lesion growth or reversal.

CONCLUSIONS

The available tissue-outcome evidence supporting the hypothesis that DWI is a surrogate marker for ischemic core in humans is troublingly inconsistent and merits an overall grade D based on the criteria set out by the Oxford Centre for Evidence-Based Medicine.

Diffusion-weighted imaging in ischemic stroke: effect of display method on observers' diagnostic performance

RATIONALE AND OBJECTIVES

When evaluating ischemic stroke on diffusion-weighted magnetic resonance imaging (DWI), the display method has not been investigated. The purpose of this study was to determine whether standardization of the display method for DWI affects observers' diagnostic performance in detecting ischemic stroke on DWI.

MATERIALS AND METHODS

Twenty-six observers evaluated 40 DWI studies in 20 patients with acute (< 6 hours) middle cerebral arterial strokes and 20 controls for the presence of hyperintense lesions in 10 areas using the Alberta Stroke Programme Early CT Score (ASPECTS) system and one area in the corona radiata using a modified version of the ASPECTS system (ASPECTS-DWI). The images were reviewed using a standardized display method (SDM) and a conventional display method (CDM). The reading time was recorded for each session. The observers' performance was evaluated with receiver-operating characteristic analysis.

RESULTS

In all observers with ASPECTS-DWI scores of < or = 8 points, the value of the mean average area under the receiver-operating characteristic curve was slightly higher for the SDM than the CDM, but the difference was not statistically significant. In the insular ribbon, diagnostic accuracy was significantly higher with the SDM than the CDM (P = .036). In the other locations, there were no significant differences. With the SDM, the mean reading time was reduced by 7.5 seconds (P = .024).

CONCLUSION

The SDM improved diagnostic accuracy for the insular ribbon and shortened the reading time, although it did not improve observers' performance with the ASPECTS-DWI system.

Late endovascular revascularization in acute ischemic stroke based on clinical-diffusion mismatch

BACKGROUND AND PURPOSE

A clinical-diffusion mismatch (CDM) among stroke patients presenting within 12-24 hours has been correlated with neurologic deterioration and infarct expansion. We sought to study the feasibility and safety of reperfusion therapy in a series of 11 consecutive patients fulfilling this criterion.

MATERIALS AND METHODS

Patients presenting with large vessel syndromes were considered for revascularization therapy. Of these patients, we identified those presenting beyond 8 hours who scored > or =8 on the National Institutes of Health Stroke Scale (NIHSS) and had limited abnormalities on diffusion-weighted MR imaging. One- and 7-day NIHSS scores were obtained. Rates of early neurologic deterioration (END, increase in NIHSS score by > or =4 points) and early neurologic improvement (ENI, decrease in NIHSS score by > or =4 points) at 1 week were determined. Follow-up imaging was obtained to evaluate intracranial hemorrhage (ICH).

RESULTS

Eleven patients were identified, 8 of whom were successfully revascularized. The mean age of all patients was 55 years with mean initial, 24-hour, and 1-week NIHSS scores of 14 +/- 4, 11 +/- 7, and 6 +/- 5, respectively, with lower scores at 24 hours and 1 week (8 +/- 5 and 4 +/- 3, respectively) among patients successfully revascularized. Eight of the treated patients (72% of the total, 100% of those successfully revascularized) experienced ENI. No patient had END or ICH.

CONCLUSIONS

Endovascular treatment for acute ischemic stroke beyond 8 hours is feasible and may prevent END and promote ENI in patients fulfilling the criteria of a CDM. A prospective study is planned.

Imaging the penumbra - strategies to detect tissue at risk after ischemic stroke

The aim of thrombolytic therapy after acute ischemic stroke is salvage of the ischemic penumbra. Several imaging techniques have been used to identify the penumbra in patients who may benefit from reperfusion beyond the currently narrow 3-hour time-window for thrombolysis. We discuss the advantages and disadvantages of positron emission tomography (PET), single photon emission computed tomography (SPECT), MRI and CT scans. We comment on concepts of clinical-imaging mismatch models and we explore the implications for clinical trials.