Rapid Assessment of Perfusion–Diffusion Mismatch

Automated Supra- and Infratentorial Brain Infarct Volume Estimation on Diffusion Weighted Imaging Using the RAPID Software

Purpose

The present computerized techniques have limits to estimate the ischemic lesion volume especially in vertebrobasilar ischemia (VBI) automatically. We investigated the ability of the RAPID AI (RAPID) software on diffusion-weighted imaging (DWI) to estimate the infarct size in VBI in comparison to supratentorial ischemia (STI).

Methods

Among 123 stroke patients (39 women, 84 men, mean age 66 ± 11 years) having undergone DWI, 41 had had a VBI and 82 a STI. The infarct volume calculation by RAPID was compared to volume calculations by 2 neurologists using the ABC/2 method. For inter-reader and between-method analysis intraclass correlation coefficient (ICC), area under the curve (AUC) estimations, and Bland–Altman plots were used.

Results

ICC between the two neurologists and each neurologist and RAPID were >0.946 (largest 95% CI boundaries 0.917–0.988) in the STI group, and > 0.757 (95% CI boundaries between 0.544 and 0.982) in the VBI group. In the STI group, AUC values ranged between 0.982 and 0.999 (95% CI 0.971–1) between the 2 neurologists and between 0.875 and 1 (95% CI 0.787–1) between the neurologists and RAPID; in the VBI group, they ranged between 0.925 and 0.965 (95% CI 0.801–1) between the neurologists, and between 0.788 and 0.931 (95% CI 0.663–1) between RAPID and the neurologists. Compared to the visual DWI interpretation by the neurologists, RAPID did not recognize a substantial number of infarct volumes of ≤ 2 ml.

Conclusion

The ability of the RAPID software to depict strokes in the vertebrobasilar artery system seems close to its ability in the supratentorial brain tissue. However, small lesion volumes ≤ 2 ml remain still undetected in both brain areas.

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.

Predictive value of Alberta stroke program early CT score for perfusion weighted imaging - diffusion weighted imaging mismatch in stroke with middle cerebral artery occlusion

This study aimed to quantitatively assess the consistency and correlation between perfusion weighted imaging (PWI)/ diffusion weighted imaging (DWI) Alberta Stroke Program Early CT Score (ASPECTS) mismatch and PWI/DWI mismatch.Sixty-eight acute ischemic stroke with middle cerebral artery occlusion who underwent magnetic resonance imaging before thrombectomy were eligible. DWI volume, PWI volume and PWI-DWI mismatch were measured. DWI-, PWI-, PWI-DWI ASPECTS were evaluated. Statistical analysis was performed to compare the correlation between volume and ASPECTS of DWI-, PWI- and PWI-DWI mismatch. Receiver operating characteristic curve analysis was used to assess the predictive value of the PWI-DWI ASPECTS mismatch for the occurrence of PWI-DWI mismatch in acute ischemic stroke patients with middle cerebral artery occlusion.Of 68 patients, the DWI volume, PWI volume and PWI-DWI mismatch volume were (27.76 ± 17.53) mL, (167.09 ± 59.64) mL and (139.33 ± 58.18) mL respectively. DWI-ASPECTS was 6.75 ± 1.90 with the interobserver agreement was κ=0.98 (95% CI, 0.95-0.99); PWI-ASPECTS was 3.09 ± 2.11 with the interobserver agreement was κ=0.95 (95% CI, 0.91-0.99); PWI-DWI ASPECTS mismatch was 6.75 ± 1.90. Spearman's rank correlation analysis revealed that PWI-DWI mismatch volume was negatively correlated with PWI-DWI ASPECTS mismatch (r = -0.802; P = .000). Receiver operating characteristic analysis showed that when the PWI-DWI ASPECTS mismatch cut point was ≥ 2, the under curve of PWI-DWI ASPECTS mismatch for predicting PWI-DWI mismatch was 0.954 (95%CI, 0.911-0.998), with the sensitivity and specificity were 84.00% and 100% respectively.PWI-DWI ASPECTS mismatch may represent a convenient surrogate for penumbra in clinical trials.

The Safety and Efficacy of Endovascular Treatment for Patients With ASPECTS<6 in Anterior Circulation Stroke: A Meta-Analysis and Subgroup Analysis by Imaging Techniques

BACKGROUND

Endovascular treatment (EVT) is merely recommended as class of recommendation IIb for patients with ASPECTS <6 according to the American Heart Association guideline 2019. In addition, the best determined imaging technique for EVT in patient with ASPECTS<6 remains unknown. The objective of this study was to define the safety and efficacy of EVT for patients with ASPECTS<6 and investigate the superiority between MRI and CT for patient selection.

METHODS

A systematic search of PubMed, EMBASE, The Cochrane Library and other additional sources was performed for studies published with no publication period. Our study was conducted corresponding to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRIMA) guidelines. The analysis was performed using the Comprehensive Meta-Analysis (CMA) 2.0.

RESULTS

Five studies reporting data from 844 participants were included in our analysis according to the inclusion criteria. Consequently, EVT was associated with statistically significant higher functional independence compared with MT (OR 5.401, 95% CI 3.227-9.041). Whereas EVT was found to be related to lower mortality compared with MT based on eligible data (OR 0.461, 95% CI 0.329-0.647). No significant difference was identified in sICH between EVT and MT (OR 1.075, 95% CI 0.452-2.558).

CONCLUSION

According to the results of our study, we suggested that EVT is a preferred therapy in ACS patients with ASPECTS<6 in consideration of efficacy and safety. Furthermore, MRI did not show superiority over CT as no statistical difference was detected in all subgroups.

Technical considerations of multi-parametric tissue outcome prediction methods in acute ischemic stroke patients

Decisions regarding acute stroke treatment rely heavily on imaging, but interpretation can be difficult for physicians. Machine learning methods can assist clinicians by providing tissue outcome predictions for different treatment approaches based on acute multi-parametric imaging. To produce such clinically viable machine learning models, factors such as classifier choice, data normalization, and data balancing must be considered. This study gives comprehensive consideration to these factors by comparing the agreement of voxel-based tissue outcome predictions using acute imaging and clinical parameters with manual lesion segmentations derived from follow-up imaging. This study considers random decision forest, generalized linear model, and k-nearest-neighbor machine learning classifiers in conjunction with three data normalization approaches (non-normalized, relative to contralateral hemisphere, and relative to contralateral VOI), and two data balancing strategies (full dataset and stratified subsampling). These classifier settings were evaluated based on 90 MRI datasets from acute ischemic stroke patients. Distinction was made between patients recanalized using intraarterial and intravenous methods, as well as those without successful recanalization. For primary quantitative comparison, the Dice metric was computed for each voxel-based tissue outcome prediction and its corresponding follow-up lesion segmentation. It was found that the random forest classifier outperformed the generalized linear model and the k-nearest-neighbor classifier, that normalization did not improve the Dice score of the lesion outcome predictions, and that the models generated lesion outcome predictions with higher Dice scores when trained with balanced datasets. No significant difference was found between the treatment groups (intraarterial vs intravenous) regarding the Dice score of the tissue outcome predictions.

Multimodal CT in Acute Stroke

PURPOSE OF REVIEW

Multimodal CT imaging (non-contrast CT, NCCT; CT angiography, CTA; and CT Perfusion, CTP) is central to acute ischemic stroke diagnosis and treatment. We reviewed the purpose and interpretation of each component of multimodal CT, as well as the evidence for use in routine care.

RECENT FINDINGS

Acute stroke thrombolysis can be administered immediately following NCCT in acute ischemic stroke patients assessed within 4.5 h of symptom onset. Definitive identification of a large vessel occlusion (LVO) requires vascular imaging, which is easily achieved with CTA. This is critical, as the standard of care for LVO within 6 h of onset is now endovascular thrombectomy (EVT). CTA source images can also be used to estimate the efficacy of collateral flow in LVO patients. The final component (CTP) permits a more accurate assessment of the extent of the ischemic penumbra. Complete multimodal CT, including objective penumbral measurement with CTP, has been used to extend the EVT window to 24 h. There is also randomized controlled trial evidence for extension of the IV thrombolysis window to 9 h with multimodal CT. Although there have been attempts to assess for responders to reperfusion strategies beyond 6 h ("late window") using collateral grades, the only evidence for treatment of this group of patients is based on selection using multimodal CT including CTP. The development of fully automated software providing quantitative ischemic penumbral and core volumes has facilitated the adoption of CTP and complete multimodal CT into routine clinical use. Multimodal CT is a powerful imaging algorithm that is central to current ischemic stroke patient care.

Clinical Results of the Intra-Arterial Thrombolysis with Stent Retriever Device Weather Perfusion Diffusion Mismatching and Intravenous Tissue Plasminogen Activator Administration

Objective

Intraarterial thrombolysis (IA-Tx) with stent retriever is accepted as an additional treatment for selected patients and the clinical benefit is well reported. Each intravenous tissue plasminogen activator administration (IV-tPA) and perfusion diffusion mismatching (P/D-mismatching) is well known the beneficial effects for recanalization and clinical outcomes. In this report, authors analyzed the clinical outcomes of additional IA-Tx with retrieval stent device, according to the combined IV-tPA and P/D-mismatching or not.

Methods

Eighty-one treated IA-Tx with the Solitaire stent retriever device, diagnosed as anterior circulation larger vessel occlusion were included in this study. Computed tomography-angiography (CTA) was done as an initial diagnostic image and acute stroke magnetic resonance image (MRI) followed after the IV-tPA. Forty-two patients were in the tPA group and 39 patients were in the non-tPA group. Recanalization rate, clinically significant hemorrhagic (sICH) and clinical outcomes were recorded according to the IV-tPA and P/D-mismatching.

Results

Recanalization rate was 81.0% in IV-tPA group, and it was 69.2% in non-tPA group (p = 0.017). While sICH were 19.9% and 25.6%, respectively (p = 0.328). Neurologic outcomes did not influence by IV-tPA administration or not. But according to the P/D-mismatching, the recanalization rate and sICH were 91.9% and 16.7% in the mismatched group and 46.7% and 46.7% in the matched group (p = 0.008 and p = 0.019, respectively).

Conclusion

For patients treated with IA-Tx with retrieval stent, IV-tPA infusion does not influence on the sICH, recanalization rate and neurologic outcomes. But P/D-mismatching was correlated well with sICH, recanalization rate and clinical outcomes.

Penumbral Imaging-Based Thrombolysis with Tenecteplase Is Feasible up to 24 Hours after Symptom Onset

BACKGROUND AND PURPOSE

Thrombolysis >4.5 hours after ischemic stroke onset is unproven. We assessed the feasibility of tenecteplase (TNK) treatment in patients with evidence of an ischemic penumbra 4.5 to 24 hours after onset.

METHODS

Acute ischemic stroke patients underwent perfusion computed tomography (CT)/magnetic resonance imaging. Patients with cerebral blood volume (CBV) or diffusion weighted imaging Alberta Stroke Program Early CT Scores (ASPECTS) >6 and mismatch score >2 (defined as >2 ASPECTS regions with delay on mean transit time maps and normal CBV) were eligible for treatment with TNK (0.25 mg/kg). Patients with mismatch patterns enrolled in non-endovascular/non-thrombolysis trials and those without mismatch patterns served as comparators.

RESULTS

The median (interquartile range) baseline National Institutes of Health Stroke Scale (NIHSS) in TNK treated patients (n=16) was 12 (range, 8 to 15). In the untreated mismatch (n=18) and nonmismatch (n=23) groups, the baseline NIHSS was 12 (range, 7 to 12) and 16 (range, 8 to 20; P=0.09) respectively. There was one symptomatic hemorrhage each in the TNK group (parenchymal hematoma [PH] 2) and non-mismatch group (PH 2). Penumbral salvage volumes were higher in TNK treated patients (48.3 mL [range, 24.9 to 80.4]) than the non-mismatch (-90.8 mL [range, -197 to -20]; P<0.0001) patients.

CONCLUSIONS

This prospective, non-randomized study supports the feasibility of TNK therapy in patients with evidence of ischemic penumbra 4 to 24 hours after onset.

ASPECTS (Alberta Stroke Program Early CT Score) Assessment of the Perfusion-Diffusion Mismatch

BACKGROUND AND PURPOSE

Rapid and reliable assessment of the perfusion-weighted imaging (PWI)/diffusion-weighted imaging (DWI) mismatch is required to promote its wider application in both acute stroke clinical routine and trials. We tested whether an evaluation based on the Alberta Stroke Program Early CT Score (ASPECTS) reliably identifies the PWI/DWI mismatch.

METHODS

A total of 232 consecutive patients with acute middle cerebral artery stroke who underwent pretreatment magnetic resonance imaging (PWI and DWI) were retrospectively evaluated. PWI-ASPECTS and DWI-ASPECTS were determined blind from manually segmented PWI and DWI volumes. Mismatch-ASPECTS was defined as the difference between PWI-ASPECTS and DWI-ASPECTS (a high score indicates a large mismatch). We determined the mismatch-ASPECTS cutoff that best identified the volumetric mismatch, defined as VolumeTmax>6s/VolumeDWI≥1.8, a volume difference≥15 mL, and a VolumeDWI<70 mL.

RESULTS

Inter-reader agreement was almost perfect for PWI-ASPECTS (κ=0.95 [95% confidence interval, 0.90-1]), and DWI-ASPECTS (κ=0.96 [95% confidence interval, 0.91-1]). There were strong negative correlations between volumetric and ASPECTS-based assessments of DWI lesions (ρ=-0.84, P<0.01) and PWI lesions (ρ=-0.90, P<0.01). Receiver operating characteristic curve analysis showed that a mismatch-ASPECTS ≥2 best identified a volumetric mismatch, with a sensitivity of 0.93 (95% confidence interval, 0.89-0.98) and a specificity of 0.82 (95% confidence interval, 0.74-0.89).

CONCLUSIONS

The mismatch-ASPECTS method can detect a true mismatch in patients with acute middle cerebral artery stroke. It could be used for rapid screening of patients with eligible mismatch, in centers not equipped with ultrafast postprocessing software.

A Stroke Registry Data on the Use of Intravenous Recombinant Tissue Plasminogen Activator in Stroke of Unknown Time of Onset

BACKGROUND

Stroke of unknown time of onset (SUTO) constitutes one fifth of all ischemic stroke admissions, and routine use of intravenous recombinant tissue plasminogen activator (IV rtPA) is recommended only in patients with a symptom onset time of less than 4.5 hours. There are limited data on clinical outcome in patients with SUTO versus patients with symptoms onset less than 4.5 hours from onset time. We hypothesized that efficacy and safety outcomes of IV rtPA therapy in selected SUTO patients are comparable to those with known onset time.

METHODS

We compared 90 days' modified Rankin Scale (mRS), rates of symptomatic intracerebral hemorrhage (sICH), in-hospital mortality, and death due to sICH between 3 groups treated with IV rtPA: SUTO, 3 hours or less, and 3.0-4.5 hours from prospective patient admissions between April 1, 2012, and July 31, 2013.

RESULTS

There were 65 participants in the SUTO group, 186 in the 3 hours or less group, and 51 in the 3.0-4.5 hours group. In-hospital mortality rates were 14.5%, 13.5%, and 11.8%, respectively. sICH risks were 1.5%, 1.6%, and 5.8%, and death rates due to sICH were 0%, 1.1%, and 1.9%, respectively. Ninety days' odds of excellent clinical outcome (mRS score 0-1) were not different between the SUTO group (odds ratio [OR] 1.14, 95% confidence interval [CI]: .63-2.10), the 3 hours or less group (OR .87, 95% CI: .48-1.60), and the 3.0-4.5 hours group (OR .79, 95% CI: .48-1.60) (P = .82).

CONCLUSION

Thrombolytic therapy outcome in SUTO is not different from in-license use in our patient population. There is an urgent need to include this patient group in ongoing randomized multicenter trials.

Susceptibility-Diffusion Mismatch in Hyperacute Stroke: Correlation with Perfusion-Diffusion Mismatch and Clinical Outcome

BACKGROUND

A prominent vein (PV) on susceptibility-weighted imaging (SWI) was recently proposed to be a marker of the penumbra. We aimed to compare the utility of SWI and perfusion-weighted imaging (PWI) sequences for the evaluation of the penumbra in hyperacute middle cerebral artery (MCA) stroke, and to determine whether SWI-DWI mismatch is a neuroimaging marker of clinical outcome.

METHODS

A total of 149 consecutive patients with MCA stroke were prospectively enrolled. Magnetic resonance imaging (MRI) was performed within 6 hours of the onset of stroke. The ASPECTS values on diffusion-weighted imaging (DWI), PWI (delayed mean transit time), and SWI (visualization of PVs) were calculated by 2 independent raters. Correlation between PWI-ASPECTS and SWI-ASPECTS was calculated with the Pearson coefficient. Reliability of the PV rating system was calculated by an intraclass correlation coefficient (ICC). Favorable outcome was defined as a modified Rankin Scale score of 0-2 at 3 months for the 88 patients who received thrombolytic therapy.

RESULTS

The ASPECTS-SWI and ASPECTS-PWI scores showed a good correlation (Pearson coefficient of .69, P <.001). The reproducibility between the findings of the junior and the senior radiologists was excellent with an ICC of .89 (confidence interval of 95% (IC95): .85-.92, P <.001). However, neither SWI-DWI mismatch nor PWI-SWI mismatch was associated with clinical outcome.

CONCLUSION

SWI and PWI were complementary but not commutable for the assessment of the penumbra. Susceptibility-diffusion mismatch was not found in this study to have predictive value for stroke outcome.

Outcomes Are Not Different between Patients with Intermediate and High DWI-ASPECTS after Stent-Retriever Embolectomy for Acute Anterior Circulation Stroke

BACKGROUND AND PURPOSE

Questions remain as to what benefits embolectomy provides to patients presented with considerable early ischemic changes on baseline imaging studies. This study aimed to investigate the impact of the Alberta Stroke Program Early CT Score applied to DWI on treatment outcomes in patients with acute stroke undergoing stent-retriever embolectomy.

MATERIALS AND METHODS

We retrospectively analyzed the clinical and DWI data from 171 patients with acute anterior circulation stroke who were treated with stent-retriever embolectomy within 6 hours of symptom onset. DWI-ASPECTS scores were analyzed with the full scale or were dichotomized (4-6 versus 7-10). Patients with DWI-ASPECTS ≤3 were excluded from the study. Associations between outcome and clinical and radiologic factors were determined with a multivariate logistic regression analysis. A good outcome was defined as a modified Rankin Scale score of 0-2 at 3 months.

RESULTS

The median DWI-ASPECTS was 7 (interquartile range, 6-8). The rates of good outcome, symptomatic hemorrhage, and mortality were not different between high DWI-ASPECTS (scores of 7-10) and intermediate DWI-ASPECTS (scores of 4-6) groups. In patients with an intermediate DWI-ASPECTS, good outcome was achieved in 46.5% (20/43) of patients with successful revascularization, whereas no patients without successful revascularization had a good outcome (P = .016). In multivariate logistic regression analysis, independent predictors of good outcome were age and successful revascularization.

CONCLUSIONS

Our study suggested that there were no differences in outcomes between patients with a high DWI-ASPECTS and those with an intermediate DWI-ASPECTS who underwent stent-retriever embolectomy for acute anterior circulation stroke. Thus, patients with an intermediate DWI-ASPECTS otherwise eligible for endovascular therapy may not be excluded from stent-retriever embolectomy or stroke trials.

Clinical results of intraarterial thrombolysis according to tPA administration and perfusion/diffusion mismatching

BACKGROUND

IA-Tx and advanced dynamic imaging studies have been adopted for ischemic stroke patient treatment. Many patients are treated with IV-tPA, but this treatment is not always feasible. In this study, IA-Tx was used for patients for whom IV-tPA was not indicated or when IV-tPA did not result in recanalization.

METHODS

A total of 156 patients treated with IA-Tx were retrospectively reviewed. Of these, 72 patients were treated with a full dose of IV-tPA before receiving the IA-Tx; the remaining 84 patients only received IA-Tx. An initial imaging study using CTA and acute stroke MRI followed. Patients' demographics and clinical results were recorded and compared according to P/D mismatching and IV-tPA.

RESULTS

Among P/D-mismatched patients, the recanalization rate was 80 % and the symptomatic intracranial hemorrhage rate was 14.5 %, while among P/D-matched patients, the rates were 63 % and 41.3 % respectively (p < 0.05). A favorable clinical outcome occurred in 49.1 % of P/D-mismatched, but only in 21.7 % of P/D-matched patients (p < 0.05). Among patients who were treated with IV-tPA before undergoing IA-Tx, the recanalization rate was 79.2 % and the sICH rate was 27.8 %, while it was 71.4 % and 17.9 % in patients who did not receive IV-tPA (p < 0.05).

CONCLUSIONS

Patients who have P/D mismatching and are treated with IA-Tx have higher recanalization rates and a greater probability of a favorable outcome than patients who have P/D matching and receive IA-Tx. For patients who do not undergo successful recanalization after IV-tPA or who are not indicated for IV-tPA, the authors recommend IA-Tx after undergoing appropriate imaging evaluation.

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.

Thrombolysis for acute ischaemic stroke

BACKGROUND

Most strokes are due to blockage of an artery in the brain by a blood clot. Prompt treatment with thrombolytic drugs can restore blood flow before major brain damage has occurred and improve recovery after stroke in some people. Thrombolytic drugs, however, can also cause serious bleeding in the brain, which can be fatal. One drug, recombinant tissue plasminogen activator (rt-PA), is licensed for use in selected patients within 4.5 hours of stroke in Europe and within three hours in the USA. There is an upper age limit of 80 years in some countries, and a limitation to mainly non-severe stroke in others. Forty per cent more data are available since this review was last updated in 2009.

OBJECTIVES

To determine whether, and in what circumstances, thrombolytic therapy might be an effective and safe treatment for acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (last searched November 2013), MEDLINE (1966 to November 2013) and EMBASE (1980 to November 2013). We also handsearched conference proceedings and journals, searched reference lists and contacted pharmaceutical companies and trialists.

SELECTION CRITERIA

Randomised trials of any thrombolytic agent compared with control in people with definite ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors applied the inclusion criteria, extracted data and assessed trial quality. We verified the extracted data with investigators of all major trials, obtaining additional unpublished data if available.

MAIN RESULTS

We included 27 trials, involving 10,187 participants, testing urokinase, streptokinase, rt-PA, recombinant pro-urokinase or desmoteplase. Four trials used intra-arterial administration, while the rest used the intravenous route. Most data come from trials that started treatment up to six hours after stroke. About 44% of the trials (about 70% of the participants) were testing intravenous rt-PA. In earlier studies very few of the participants (0.5%) were aged over 80 years; in this update, 16% of participants are over 80 years of age due to the inclusion of IST-3 (53% of participants in this trial were aged over 80 years). Trials published more recently utilised computerised randomisation, so there are less likely to be baseline imbalances than in previous versions of the review. More than 50% of trials fulfilled criteria for high-grade concealment; there were few losses to follow-up for the main outcomes.Thrombolytic therapy, mostly administered up to six hours after ischaemic stroke, significantly reduced the proportion of participants who were dead or dependent (modified Rankin 3 to 6) at three to six months after stroke (odds ratio (OR) 0.85, 95% confidence interval (CI) 0.78 to 0.93). Thrombolytic therapy increased the risk of symptomatic intracranial haemorrhage (OR 3.75, 95% CI 3.11 to 4.51), early death (OR 1.69, 95% CI 1.44 to 1.98; 13 trials, 7458 participants) and death by three to six months after stroke (OR 1.18, 95% CI 1.06 to 1.30). Early death after thrombolysis was mostly attributable to intracranial haemorrhage. Treatment within three hours of stroke was more effective in reducing death or dependency (OR 0.66, 95% CI 0.56 to 0.79) without any increase in death (OR 0.99, 95% CI 0.82 to 1.21; 11 trials, 2187 participants). There was heterogeneity between the trials. Contemporaneous antithrombotic drugs increased the risk of death. Trials testing rt-PA showed a significant reduction in death or dependency with treatment up to six hours (OR 0.84, 95% CI 0.77 to 0.93, P = 0.0006; 8 trials, 6729 participants) with significant heterogeneity; treatment within three hours was more beneficial (OR 0.65, 95% CI 0.54 to 0.80, P < 0.0001; 6 trials, 1779 participants) without heterogeneity. Participants aged over 80 years benefited equally to those aged under 80 years, particularly if treated within three hours of stroke.

AUTHORS' CONCLUSIONS

Thrombolytic therapy given up to six hours after stroke reduces the proportion of dead or dependent people. Those treated within the first three hours derive substantially more benefit than with later treatment. This overall benefit was apparent despite an increase in symptomatic intracranial haemorrhage, deaths at seven to 10 days, and deaths at final follow-up (except for trials testing rt-PA, which had no effect on death at final follow-up). Further trials are needed to identify the latest time window, whether people with mild stroke benefit from thrombolysis, to find ways of reducing symptomatic intracranial haemorrhage and deaths, and to identify the environment in which thrombolysis may best be given in routine practice.

To do or not to do; dilemma of intra-arterial revascularization in acute ischemic stroke

Background

There has still been lack of evidence for definite imaging criteria of intra-arterial revascularization (IAR). Therefore, IAR selection is left largely to individual clinicians. In this study, we sought to investigate the overall agreement of IAR selection among different stroke clinicians and factors associated with good agreement of IAR selection.

Methods

From the prospectively registered data base of a tertiary hospital, we identified consecutive patients with acute ischemic stroke. IAR selection based on the provided magnetic resonance imaging (MRI) results and clinical information were independently performed by 5 independent stroke physicians currently working at 4 different university hospitals. MRI results were also reviewed by 2 independent experienced neurologists blinded to clinical data and physicians' IAR selection. The Alberta Stroke Program Early Computed Tomography Score (ASPECTS) was calculated on initial DWI and MTT. We arbitrarily used ASPECTS differences between DWI and MTT (D-M ASPECTS) to quantitatively evaluate mismatch.

Results

The overall interobserver agreement of IAR selection was fair (kappa = 0.398). In patients with DWI-ASPECTS >6, interobserver agreement was moderate to substantial (0.398–0.620). In patients with D-M ASPECTS >4, interobserver agreement was moderate to almost perfect (0.532–1.000). Patients with higher DWI or D-M ASPECTS had better agreement of IAR selection.

Conclusion

Our study showed that DWI-ASPSECTS >6 and D-M ASPECTS >4 had moderate to substantial agreement of IAR selection among different stroke physicians. However, there is still poor agreement as to whether IAR should not be performed in patients with lower DWI and D-M ASPECTS.

Pretreatment advanced imaging in patients with stroke treated with IV thrombolysis: evaluation of a multihospital data base

BACKGROUND AND PURPOSE

CT angiography, CT perfusion, and MR imaging have all been advocated as potentially useful in treatment planning for patients with acute ischemic stroke. We evaluated a large multihospital data base to determine how the use of advanced imaging is evolving in patients treated with intravenous thrombolysis.

MATERIALS AND METHODS

Patients with acute ischemic stroke receiving IV thrombolytic therapy from 2008 to 2011 were identified by using the Premier Perspective data base. Mortality and discharge to long-term care rates were compared following multivariate logistic regression between patients who received head CT only versus those who received CTA without CT perfusion, CT perfusion, or MR imaging.

RESULTS

Of 12,429 included patients, 7305 (59%) were in the CT group, 2359 (19%) were in the CTA group, 848 (7%) were in the CTP group, and 1917 (15%) were in the MR group. From 2008 to 2011, the percentage of patients receiving head CT only decreased from 64% to 55%, while the percentage who received cerebral CT perfusion increased from 3% to 8%. The use of CT angiography and MR imaging marginally increased (1%-2%). Outcomes were similar between CT only and advanced imaging patients, except discharge to long-term care was slightly more frequent in the CTP group (OR = 1.17 [95% CI, 0.96-1.43]; P = .0412) and MR group (OR = 1.14 [95% CI, 1.01-1.28]; P = .0177) and mortality was lower in the MR group (OR = 0.64 [95% CI, 0.52-0.79]; P < .0001).

CONCLUSIONS

Use of advanced imaging is increasing in patients treated with IV thrombolysis. While there were differences in outcomes among imaging groups, the clinical effect of advanced imaging remains unclear.

Translational Perspectives on Perfusion–Diffusion Mismatch in Ischemic Stroke

Magnetic resonance imaging has tremendous potential to illuminate ischemic stroke pathophysiology and guide rational treatment decisions. Clinical applications to date have been largely limited to trials. However, recent analyses of the major clinical studies have led to refinements in selection criteria and improved understanding of the potential implications for the risk vs. benefit of thrombolytic therapy. In parallel, preclinical studies have provided complementary information on the evolution of stroke that is difficult to obtain in humans due to the requirement for continuous or repeated imaging and pathological verification. We review the clinical and preclinical advances that have led to perfusion–diffusion mismatch being applied in phase 3 randomized trials and, potentially, future routine clinical practice.

Reliability of visual assessment of non-contrast CT, CT angiography source images and CT perfusion in patients with suspected ischemic stroke

Background and Purpose

Good reliability of methods to assess the extent of ischemia in acute stroke is important for implementation in clinical practice, especially between observers with varying experience. Our aim was to determine inter- and intra-observer reliability of the 1/3 middle cerebral artery (MCA) rule and the Alberta Stroke Program Early CT Score (ASPECTS) for different CT modalities in patients suspected of acute ischemic stroke.

Methods

We prospectively included 105 patients with acute neurological deficit due to suspected acute ischemic stroke within 9 hours after symptom onset. All patients underwent non-contrast CT, CT perfusion and CT angiography on admission. All images were evaluated twice for presence of ischemia, ischemia with >1/3 MCA involvement, and ASPECTS. Four observers evaluated twenty scans twice for intra-observer agreement. We used kappa statistics and intraclass correlation coefficient to calculate agreement.

Results

Inter-observer agreement for the 1/3 MCA rule and ASPECTS was fair to good for non-contrast CT, poor to good for CT angiography source images, but excellent for all CT perfusion maps (cerebral blood volume, mean transit time, and predicted penumbra and infarct maps). Intra-observer agreement for the 1/3 MCA rule and ASPECTS was poor to good for non-contrast CT, fair to moderate for CT angiography source images, and good to excellent for all CT perfusion maps.

Conclusion

Between observers with a different level of experience, agreement on the radiological diagnosis of cerebral ischemia is much better for CT perfusion than for non-contrast CT and CT angiography source images, and therefore CT perfusion is a very reliable addition to standard stroke imaging.

Early Anticipation of Candidacy for Intra-Arterial Reperfusion Therapy Based on Baseline Clinical Stroke Subtypes: Comparison with Multiparametric MRI Taken within 4.5 Hours from Stroke Onset

Background

The decision to proceed with intra-arterial (IA) reperfusion therapy is typically made late in the course of in-hospital treatment for acute ischemic stroke. Early anticipation of candidacy for IA reperfusion therapy based on clinical stroke subtypes would be useful for guiding stroke management. The aim of this study was to investigate the relationship between the clinical Oxfordshire Community Stroke Project (OCSP) classification and MRI results taken within a 4.5-hour time window from stroke onset, with the hypothesis that the persistence of major arterial occlusion and extended ischemic penumbra, key criteria for proceeding with IA reperfusion therapy, would be distinctive between the clinical stroke subtypes.

Methods

A total of 161 patients with acute ischemic stroke in the anterior circulation were included in this study. All patients were treated with intravenous alteplase, and MRI scans were performed following alteplase initiation. Prior to treatment, the patients were categorized, based on the OCSP classification scheme, as having total anterior circulation infarcts (TACI), partial anterior circulation infarcts (PACI), or lacunar infarcts (LACI). The relationship between OCSP subtypes, MRI parameters, and clinical variables was analyzed.

Results

Overall, 40/161 patients (24.8%) were candidates for IA rescue reperfusion. With respect to the classification, 30/69 TACI (43.5%), 6/33 PACI (18.2%), and 4/59 LACI patients (6.8%) were candidates (p < 0.001). Major arterial occlusion was found in 56/161 patients (34.8%), and 46/69 TACI (66.7%), 6/33 PACI (18.2%), and 4/59 LACI patients (6.8%) had a major arterial occlusion (p < 0.001). A perfusion-diffusion mismatch greater than 20% was found in 85/161 patients (52.8%). More specifically, 40/69 TACI (58.0%), 25/33 PACI (75.8%), and 20/59 LACI patients (33.9%) had a perfusion-diffusion mismatch (p < 0.001). However, in terms of the total area of mismatch, 66.0% of patients with ASPECTS_DWI-PWI ≥2 (Alberta Stroke Program Early CT Score) were classified as TACI patients (p < 0.001) and of the patients with ASPECTS_DWI-PWI ≥3, 74.3% were classified as TACI patients (p < 0.001). Relative to candidates for IA rescue reperfusion, the clinical TACI group showed 75.0% sensitivity, 67.8% specificity, a positive predictive value of 43.5%, and a negative predictive value of 89.1%.

Conclusions

In this study, patients classified as having clinical TACI were significantly more likely to be candidates for IA rescue reperfusion. Additionally, they incurred a higher incidence of persistent major arterial occlusion and had a penumbra area that was significantly larger than normal. Therefore, clinical OCSP can be used as an ‘early warning system’ for IA reperfusion candidacy, which can allow for advanced preparation of IA therapy and theoretically shorten treatment time and reduce infarction.

Perfusion imaging in brain disease

Perfusion CT or MRI have been extensively developed over the last years and are accessible on most imaging machines. Perfusion CT has taken a major place in the assessment of a stroke. Its role has to be specified for the diagnosis and treatment of the vasospasm, complicating a subarachnoid hemorrhage. Perfusion MRI should be included in the assessment of any brain tumor, both at the time of the diagnosis as well as in the post-treatment monitoring. It is included in the multimodal approach required for the optimum treatment of this disease. The applications in epilepsy and the neurodegenerative diseases are in the evaluation process.

Hemodynamic segmentation of brain perfusion images with delay and dispersion effects using an expectation-maximization algorithm

Automatic identification of various perfusion compartments from dynamic susceptibility contrast magnetic resonance brain images can assist in clinical diagnosis and treatment of cerebrovascular diseases. The principle of segmentation methods was based on the clustering of bolus transit-time profiles to discern areas of different tissues. However, the cerebrovascular diseases may result in a delayed and dispersed local perfusion and therefore alter the hemodynamic signal profiles. Assessing the accuracy of the segmentation technique under delayed/dispersed circumstance is critical to accurately evaluate the severity of the vascular disease. In this study, we improved the segmentation method of expectation-maximization algorithm by using the results of hierarchical clustering on whitened perfusion data as initial parameters for a mixture of multivariate Gaussians model. In addition, Monte Carlo simulations were conducted to evaluate the performance of proposed method under different levels of delay, dispersion, and noise of signal profiles in tissue segmentation. The proposed method was used to classify brain tissue types using perfusion data from five normal participants, a patient with unilateral stenosis of the internal carotid artery, and a patient with moyamoya disease. Our results showed that the normal, delayed or dispersed hemodynamics can be well differentiated for patients, and therefore the local arterial input function for impaired tissues can be recognized to minimize the error when estimating the cerebral blood flow. Furthermore, the tissue in the risk of infarct and the tissue with or without the complementary blood supply from the communicating arteries can be identified.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Interobserver Agreement of ASPECT Score Distribution for Noncontrast CT, CT Angiography, and CT Perfusion in Acute Stroke

Background and Purpose—

The Alberta Stroke program early CT score (ASPECTS) is a semiquantative scale for estimating extent and distribution of early ischemic changes within the MCA territory in the acute stroke setting. Good interobserver agreement of total ASPECTS is demonstrated for noncontrast CT (NCCT) and other imaging modalities. Our purpose is to assess interobserver agreement for individual ASPECTS regions for different imaging modalities.

Methods—

One hundred and eighty-one consecutive patients presenting with acute stroke symptoms within 4.5 hours of onset were included. Four readers assigned total and individual ASPECTS for NCCT, CT angiography source images (CTA-SI), and CTP maps of cerebral blood volume (CTP-CBV). Interobserver agreement was assessed by measuring internal consistency and concordance of total and individual ASPECTS using Cronbach’s α and intraclass correlation coefficient, respectively.

Results—

Total ASPECTS demonstrated very good concordance and internal consistency for all 3 modalities. Intraclass correlation coefficient and Cronbach’s α were 0.834 and 0.859 for NCCT, 0.876 and 0.894 for CTA, and 0.903 and 0.911 for CTP-CBV, respectively. Performance for individual ASPECTS regions was inferior to total ASPECTS, but incremental improvement in interobserver reliability was demonstrated for NCCT, CTA-SI, and CTP-CBV, respectively. Highest concordance was shown for caudate, lentiform, and M1–M3, whereas performance for internal capsule and M4–M6 was poorer.

Conclusions—

CTP-CBV demonstrates the highest interobserver agreement for individual ASPECTS regions.

Deletion of TRAAK potassium channel affects brain metabolism and protects against ischemia

Cerebral stroke is a worldwide leading cause of disability. The two-pore domain K⁺ channels identified as background channels are involved in many functions in brain under physiological and pathological conditions. We addressed the hypothesis that TRAAK, a mechano-gated and lipid-sensitive two-pore domain K⁺ channel, is involved in the pathophysiology of brain ischemia. We studied the effects of TRAAK deletion on brain morphology and metabolism under physiological conditions, and during temporary focal cerebral ischemia in Traak⁻/⁻ mice using a combination of in vivo magnetic resonance imaging (MRI) techniques and multinuclear magnetic resonance spectroscopy (MRS) methods. We provide the first in vivo evidence establishing a link between TRAAK and neurometabolism. Under physiological conditions, Traak⁻/⁻ mice showed a particular metabolic phenotype characterized by higher levels of taurine and myo-inositol than Traak⁺/⁺ mice. Upon ischemia, Traak⁻/⁻ mice had a smaller infarcted volume, with lower contribution of cellular edema than Traak⁺/⁺ mice. Moreover, brain microcirculation was less damaged, and brain metabolism and pH were preserved. Our results show that expression of TRAAK strongly influences tissue levels of organic osmolytes. Traak⁻/⁻ mice resilience to cellular edema under ischemia appears related to their physiologically high levels of myo-inositol and of taurine, an aminoacid involved in the modulation of mitochondrial activity and cell death. The beneficial effects of TRAAK deletion designate this channel as a promising pharmacological target for the treatment against stroke.

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.

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.

ASPECTS and other neuroimaging scores in the triage and prediction of outcome in acute stroke patients

Information obtained from brain imaging is now summarized in the form of various neuroimaging scores to help physicians in making therapeutic decisions and determining prognosis. The Alberta Stroke Program Early CT Score (ASPECTS) was devised to quantify the extent of early ischemic changes in the middle cerebral artery territory on noncontrast computed tomography. With its systematic approach, the score is simple, reliable, and a strong predictor of functional outcome. This review summarizes ASPECTS and other neuroimaging scores developed for risk prognostication and risk stratification with treatment in patients with acute ischemic stroke.

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.

Safety and clinical outcome of thrombolysis in ischaemic stroke using a perfusion CT mismatch between 3 and 6 hours

OBJECTIVE

It may be possible to thrombolyse ischaemic stroke (IS) patients up to 6 h by using penumbral imaging. We investigated whether a perfusion CT (CTP) mismatch can help to select patients for thrombolysis up to 6 h.

METHODS

A cohort of 254 thrombolysed IS patients was studied. 174 (69%) were thrombolysed at 0-3 h by using non-contrast CT (NCCT), and 80 (31%) at 3-6 h (35 at 3-4.5 h and 45 at 4.5-6 h) by using CTP mismatch criteria. Symptomatic intracerebral haemorrhage (SICH), the mortality and the modified Rankin Score (mRS) were assessed at 3 months. Independent determinants of outcome in patients thrombolysed between 3 and 6 h were identified.

RESULTS

The baseline characteristics were comparable in the two groups. There were no differences in SICH (3% v 4%, p = 0.71), any ICH (7% v 9%, p = 0.61), or mortality (16% v 9%, p = 0.15) or mRS 0-2 at 3 months (55% v 54%, p = 0.96) between patients thrombolysed at 0-3 h (NCCT only) or at 3-6 h (CTP mismatch). There were no significant differences in outcome between patients thrombolysed at 3-4.5 h or 4.5-6 h. The NIHSS score was the only independent determinant of a mRS of 0-2 at 3 months (OR 0.89, 95% CI 0.82-0.97, p = 0.007) in patients treated using CTP mismatch criteria beyond 3 h.

CONCLUSIONS

The use of a CTP mismatch model may help to guide thrombolysis decisions up to 6 h after IS onset.

In vivo evaluation of quantitative MR angiography in a canine carotid artery stenosis model

BACKGROUND AND PURPOSE

Large-vessel cerebral blood flow quantification has emerged as a potential predictor of stroke risk. QMRA uses phase-contrast techniques to noninvasively measure vessel flows. To evaluate the in vivo accuracy of QMRA for measuring the effects of progressive arterial stenosis, we compared this technique with invasive flow measurements from a sonographic transit-time flow probe in a canine model.

MATERIALS AND METHODS

A sonographic flow probe was implanted around the CCA of hound dogs (n = 4) under general anesthesia. Pulsatile blood flow and arterial pressure were continuously recorded during CCA flow measurements with QMRA. A vascular tourniquet was applied around the CCA to produce progressive stenosis and varying flow rates. Statistical comparisons were made by using the Pearson product moment correlation coefficient.

RESULTS

A total of 60 paired CCA flow measurements were compared. Mean blood flows ranged between 21 and 691 mL/min during QMRA acquisition as measured by the flow probe. The correlation coefficients between flow probe and QMRA measurements for mean, maximum, and minimum volume flow rates were 0.99 (P < .0001), 0.98 (P < .0001), and 0.96 (P < .0001), respectively. The overall proportional difference between the 2 techniques was 7.8 ± 1%. Measurements at higher flow rates and in the absence of arterial stenosis had the lowest PD.

CONCLUSIONS

Noninvasive CCA flow measurements by using QMRA are accurate compared with invasive flow-probe measurements in a canine arterial flow model with stenosis and may be useful for the evaluation of the hemodynamic effects of stenosis caused by cerebrovascular atherosclerosis.

Oxfordshire community stroke project classification poorly differentiates small cortical and subcortical infarcts

BACKGROUND AND PURPOSE

The Oxfordshire Community Stroke Project (OCSP) is a common clinical stroke classification tool. We evaluated the accuracy of OCSP classification with a prospective magnetic resonance imaging (MRI) study.

METHODS

Stroke/transient ischemic attack patients presenting within 48 hours of onset were included in the study (n=130). Following computed tomography scan, OCSP classification, total anterior circulation infarcts (TACI), partial anterior circulation infarcts (PACI), lacunar circulation infarcts (LACI), and posterior circulation infarcts (POCI) were performed by 3 independent examiners. All patients underwent diffusion-weighted MRI with planimetric volume measurement and classification into OCSP categories, organized by lesion location.

RESULTS

Patients were clinically classified as TACI (12 patients), PACI (62 patients), LACI (38 patients), and POCI (18 patients). In 101 patients with diffusion-weighted MRI lesions, correct classification rates were: TACI (83.3%), PACI (83%), LACI (39%), and POCI (86%). OCSP had the following sensitivity (SE), specificity (SP), and positive predictive value (PPV): TACI (SE, 100%; SP, 98%; PPV, 83%), PACI (SE, 73%; SP, 78%; PPV, 83%), LACI (SE, 47%; SP, 83%; PPV, 39%), and POCI (SE, 92%; SP, 98%; PPV, 86%). Sixty-one percent of patients in the LACI group had radiographic appearances consistent with PACI, and 15% of those classified as PACI had lacunar infarcts. No differences in stroke severity existed between patients classified correctly (median National Institutes of Health Stroke Scale [NIHSS]=4; interquartile range [IQR]=7) or incorrectly (median NIHSS=3; IQR=3). Patients classified correctly had larger infarct volume (median=6.75 mL; IQR=33.2) than did those who were incorrectly classified (1.86 mL; IQR=5; P=0.008).

CONCLUSIONS

OCSP classification does not permit accurate discrimination between lacunar and small-volume cortical infarcts. Differential patterns of investigation for stroke etiology should not be based solely on clinical criteria.

Relationship between sodium intensity and perfusion deficits in acute ischemic stroke

PURPOSE

To assess the relationship between sodium signal intensity changes and oligemia, measured with perfusion-weighted imaging (PWI), in ischemic stroke patients.

MATERIALS AND METHODS

Nine ischemic stroke patients (55 ± 13 years), four with follow-up scans, underwent sodium and proton imaging 4-32 hours after symptom onset. Relative sodium intensity was calculated as the ratio of signal intensities in core (identified as hypertintense lesions on diffusion-weighted imaging [DWI]) or putative penumbra (PWI-DWI mismatch) to contralateral homologous regions.

RESULTS

Sodium intensity increases in the core were not correlated with the severity of hypoperfusion, measured with either cerebral blood flow (rho = 0.157; P = 0.61) or cerebral blood volume (rho = -0.234; P = 0.44). In contrast, relative sodium intensity was not elevated (4-7 hours 0.96 ± 0.07; 17-32 hours 1.00 ± 0.07) in PWI-DWI mismatch regions.

CONCLUSION

Sodium signal intensity cannot be predicted by the degree of hypoperfusion acutely. Sodium intensity also remains unchanged in PWI-DWI mismatch tissue, indicating preservation of ionic homeostasis. Sodium magnetic resonance imaging (MRI), in conjunction with PWI and DWI, may permit identification of patients with viable tissue, despite an unknown symptom onset time.

Thrombolysis as a factor associated with favorable outcomes in patients with unclear-onset stroke

BACKGROUND AND PURPOSE

Clinical and radiological features of patients with unclear-onset stroke do not differ significantly from those with known-onset stroke. There is a lack of evidence for the safety and efficacy of thrombolysis in patients with unclear-onset stroke. We sought to provide supportive data on the safety and efficiency of thrombolysis in patients with unclear-onset stroke.

METHODS

We retrospectively identified patients with unclear-onset stroke (<3 h of first found abnormal time) from our stroke registry. We performed following protocols for thrombolysis in patients with unclear-onset stroke; initial conventional CT-based intravenous thrombolysis (IVT), repeat MRI during IVT, and then decision to maintain IVT or to perform combined intra-arterial thrombolysis. In addition, we compared clinical outcomes and safety between thrombolyzed and non-thrombolyzed patients.

RESULTS

A total of 78 patients with unclear-onset stroke were included. Twenty-nine patients underwent thrombolysis. Thrombolysis (OR, 6.842; 95% CI, 1.950-24.004; P = 0.003) and baseline NIHSS (OR, 0.769; 95% CI, 0.645-0.917; P = 0.003) were associated with favorable outcomes at 3 months in multivariate logistic regression analysis. The frequency of hemorrhagic transformation and symptomatic ICH was not significantly different between the thrombolyzed and non-thrombolyzed patients (34.4% vs. 40.7% and 10.3% vs. 8.2%, respectively).

CONCLUSION

The results of this study suggest that thrombolysis in unclear-onset stroke could be independently associated with favorable outcomes at 3 months and that thrombolysis based on repeat imaging appears to be safely applied to patients with unclear-onset stroke.

Neuroimaging in acute ischaemic stroke: insights into unanswered questions of pathophysiology

The treatment of acute ischaemic stroke is based on the principle that there is ischaemic but still potentially salvageable tissue that could be rescued if blood flow could be restored quickly. It is assumed that salvage might only be possible in the first few hours, and that infarct expansion is a direct result of failed recanalization of the main artery. This concept arose from experimental work in the 1970s, supported more recently by studies using imaging to identify penumbral tissue. However, although magnetic resonance diffusion and perfusion imaging is a way of imaging penumbral tissue and has been around for over a decade, it is not an easy technique to apply in practice and its use has produced conflicting results. Computed tomography perfusion, and any other tissue perfusion imaging technique, is likely to encounter the same difficulties. Indeed many factors, other than the presence of a diffusion-perfusion mismatch acutely, may determine or influence ultimate tissue fate even days after the stroke, and in turn, clinical outcome. Many of these potential influences are beginning to emerge from studies using different forms of imaging at later times after stroke. This review will explore the information now emerging from imaging studies in large artery ischaemic stroke to summarize knowledge to date and indicate unresolved issues for the future.

Atlas-based topographical scoring for magnetic resonance imaging of acute stroke

BACKGROUND AND PURPOSE

The Alberta Stroke Program Early CT Score (ASPECTS), a 10-point scale, is a clinical tool for assessment of early ischemic changes after stroke based on the location and extent of a visible stroke lesion. It has been extended for use with MR diffusion-weighted imaging. The purpose of this work was to automate a MR topographical score (MR-TS) using a digital atlas to develop an objective tool for large-scale analyses and possibly reduce interrater variability and slice orientation differences.

METHODS

We assessed 30 patients with acute ischemic stroke with a diffusion lesion who provided informed consent. Patients were imaged by CT and MRI within 24 hours of symptom onset. An MR-TS digital atlas was generated using the ASPECTS scoring sheet and anatomic MR data sets. Automated MR topographical scores (auto-MR-TS) were obtained based on the overlap of lesions on apparent diffusion coefficient maps with MR-TS atlas regions. Auto-MR-TS scores were then compared with scores derived manually (man-MR-TS) and with conventional CT ASPECTS scores.

RESULTS

Of the 30 patients, 29 were assessed with auto-MR-TS. Auto-MR-TS was significantly lower than CT ASPECTS (P<0.001), but with a median difference of only 1 point. There was no significant difference between the auto-MR-TS and the man-MR-TS with a median difference of 0 points; 86% of patient scores differed by <or=1 point.

CONCLUSIONS

Auto-MR-TS provides a measure of stroke severity in an automated fashion and facilitates more objective, sensitive, and potentially more complex ASPECTS-based scoring.

Management of ischemic stroke: Part 1. Emergency room management

BACKGROUND

Acute ischemic stroke is commonly encountered by the hospitalist. There have been dramatic changes in our ability to care for these patients acutely. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) primary stroke center certification has become progressively more important to institutions nationally and includes many aspects of initial evaluation and treatment.

PURPOSE

Acute treatment involves the rapid assimilation of patient characteristics, laboratory results, and imaging results. There are a growing number of potential acute therapies with a range of risk, benefit, necessary time windows, and specific eligibility criteria.

DATA SOURCES

Primary trials, current guidelines.

CONCLUSIONS

The hospitalist is well-positioned to play a major role in the treatment of stroke patients as well as the systems work that aids in the management of this population.

The Alberta Stroke Program Early CT Score in Clinical Practice: What have We Learned?

The introduction of brain imaging with computed tomography revolutionised the treatment of patients with acute ischaemic stroke. With the visual differentiation of haemorrhagic stroke from ischaemic stroke, thrombolytic therapy became feasible. The Alberta Stroke Program Early CT Score was devised to quantify the extent of early ischaemic changes in the middle cerebral artery territory on noncontrast computed tomography. With its systematic approach, the score is simple and reliable. However, the assessment of early ischaemic changes and Alberta Stroke Program Early CT scoring require training. The Alberta Stroke Program Early CT Score is a strong predictor of functional outcome. Furthermore, the effectiveness of intraarterial thrombolysis in patients with middle cerebral artery occlusion shows effect modification by the Alberta Stroke Program Early CT Score. This review summarises the Alberta Stroke Program Early CT Score methodology. We illustrate current knowledge regarding Alberta Stroke Program Early CT Score applied to clinical trials and comment on how Alberta Stroke Program Early CT Score may facilitate clinical treatment decision making and future trial design. Moreover, we introduce a modification of the Alberta Stroke Program Early CT Score methodology that disregards isolated cortical swelling, i.e. focal brain swelling without associated parenchymal hypoattenuation, as early ischaemic changes in the Alberta Stroke Program Early CT Score system.

Revascularization in acute ischaemic stroke using the penumbra system: the first single center experience

BACKGROUND AND PURPOSE

This is the first single center experience illustrating the effectiveness of the penumbra system (PS) in the treatment of large vessel occlusive disease in the arena of acute ischaemic stroke. The PS is an innovative mechanical thrombectomy device, employed in the revascularization of large cerebral vessel occlusions in patients via the utilization of an aspiration platform.

METHODS

This is a prospective, non-randomized controlled trial evaluating the clinical and functional outcome in 29 patients with acute intra-cranial occlusions consequent to mechanical thrombectomy by the PS either as mono-therapy or as an adjunct to current standard of care. Patients were evaluated by a neurologist and treated by our in house interventional neuro-radiologists. Primary end-points were revascularization of the occluded target vessel to TIMI grade 2 or 3 and neurological outcome as measured by an improvement in the NIH Stroke Scale (NIHSS) score after the procedure.

RESULTS

Complete revascularization (TIMI 3) was achieved in 21/29 (72.4%) of patients. Partial revascularization (TIMI 2) was established in 4/29 (13.8%) of patients. Revascularization failed in four (13.8%) patients. Nineteen (19) patients (65.5%) had at least a four-point improvement in NIHSS scores. Modified Rankin scale scores of < or =2 were seen in 37.9% of patients. There were no device-related adverse events. Symptomatic intra-cranial hemorrhage occurred in 7% of patients.

CONCLUSIONS

The PS has the potential of exercising a significant impact in the interventional treatment of ischaemic stroke in the future.

[Mechanical recanalization]

Although several studies and registries have focused on new interventional systems for the treatment of acute ischemic stroke, a standard procedure has not yet been established. The procedure itself is still controversially discussed but studies have shown that patients who were successfully treated with mechanical recanalization had a better clinical outcome.