The clinical-DWI mismatch: a new diagnostic approach to the brain tissue at risk of infarction

Wake-Up Stroke: Current Understanding

Patients with wake-up strokes account for approximately 1 in 5 individuals presenting with an acute ischemic stroke. However, they are commonly excluded from acute stroke treatment. This article reviews the current understanding of wake-up strokes. A comparison of wake-up and awake-onset strokes demonstrated that they are physiologically, clinically, and radiologically similar. Use of advanced CT and MRI techniques may help extend acute stroke treatment options to patients with wake-up stroke.

Vectorized nanodelivery systems for ischemic stroke: a concept and a need

Neurological diseases of diverse aetiologies have significant effects on the quality of life of patients. The limited self-repairing capacity of the brain is considered to be the origin of the irreversible and progressive nature of many neurological diseases. Therefore, neuroprotection is an important goal shared by many clinical neurologists and neuroscientists. In this review, we discuss the main obstacles that have prevented the implementation of experimental neuroprotective strategies in humans and propose alternative avenues for the use of neuroprotection as a feasible therapeutic approach. Special attention is devoted to nanotechnology, which is a new approach for developing highly specific and localized biomedical solutions for the study of the multiple mechanisms involved in stroke. Nanotechnology is contributing to personalized neuroprotection by allowing us to identify mechanisms, determine optimal therapeutic windows, and protect patients from brain damage. In summary, multiple aspects of these new players in biomedicine should be considered in future in vivo and in vitro studies with the aim of improving their applicability to clinical studies.

Diffusion and Perfusion MR Imaging in Acute Stroke: Clinical Utility and Potential Limitations for Treatment Selection

Magnetic resonance (MR) diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) offer unique insight into acute ischemic stroke pathophysiology. These techniques may offer the ability to apply pathophysiology to accurately individualize acute stroke reperfusion treatment, including extending the opportunity of reperfusion treatment to well beyond the current time-based treatment windows.This review examines the use of DWI and PWI in the major stroke trials, their current clinical utility, and potential limitations for reperfusion treatment selection. DWI and PWI continue to be investigated in ongoing randomized controlled trials, and continued research into these techniques will help achieve the goal of tissue-based decision making and individualized acute stroke treatment.

Association of Cortical Vein Filling with Clot Location and Clinical Outcomes in Acute Ischaemic Stroke Patients

Delay in cortical vein filling during the late-venous phase (delayed-LCVF) is characterized by opacification of cerebral veins despite contrast clearance from contralateral veins on dynamic computed tomography angiography (dCTA) in acute ischemic stroke (AIS) patients. The aim of the study was to investigate the associations of delayed-LCVF with clot location, reperfusion status at 24 hours, and 90-days functional outcome in AIS patients who received reperfusion therapy. A prospective cohort of AIS patients treated with intravenous thrombolysis was studied. Groupwise comparison, univariate, and multivariate regression analyses were used to study the association of delayed-LCVF with clot location and clinical outcomes. Of 93 patients (mean age = 72 ± 12 years) with hemispheric AIS included in the study, 46 (49%) demonstrated delayed-LCVF. Patients with delayed-LCVF demonstrated a significantly higher proportion of proximal occlusion (72% vs 13%, P =< 0.0001), and poor reperfusion at 24 hours (41% vs 11%, P = 0.001). The proportion of poor functional outcome at 90 days was not significantly different (22/56 (48%) vs 17/61 (36%), P = 0.297). The appearance of delayed-LCVF on baseline dCTA may be a surrogate for large vessel occlusion, and an early marker for poor 24-hour angiographic reperfusion.

Clinical diffusion mismatch better discriminates infarct growth than mean transit time-diffusion weighted imaging mismatch in patients with middle cerebral artery-M1 occlusion and limited infarct core

BACKGROUND AND PURPOSE

Our purpose was to compare clinical diffusion mismatch (CDM) and mean transit time (MTT)-diffusion mismatch as predictors of infarct growth in patients with proximal middle cerebral artery (MCA) occlusion and small infarct core on presentation.

METHODS

Retrospective analysis of consecutive stroke patients with: (1) MCA-M1 occlusion; (2) MRI performed ≤10 h from symptoms onset; and (3) baseline MRI-diffusion weighted imaging (DWI) volume ≤25 mL. Definitions included: CDM=baseline National Institutes of Health Stroke Scale (NIHSS) score ≥8 and DWI volume ≤25 mL; MTT-DWI mismatch=visually assessed unthresholded MTT lesion ((MTT-DWI))/DWI) ≥20% and ≥10 mL larger than the DWI lesion; and significant infarct growth (>20% (≥5 mL) increase in infarct volume on follow-up). Uni-/multivariate analyses were performed to define the predictors of infarct growth.

RESULTS

63 stroke patients with MCA-M1 occlusions and MRI within 10 h of onset were evaluated. 20 patients were excluded on the basis of DWI volume >25 mL leaving 43 patients (mean age 75.8 years; median NIHSS=13) in the study cohort. On univariate analysis, larger admission DWI volume (p<0.0001), baseline NIHSS score ≥8 (p=0.001), lack of IV and/or endovascular treatment (p=0.021), glucose levels >125 mg/dL (p=0.024), poor CT angiography collaterals (p=0.046), and lower admission Alberta Stroke Program Early CT score (ASPECTS) (p=0.049) predicted infarct growth. Baseline NIHSS score ≥8 was the only independent predictor of stroke growth in the multivariate analysis (p=0.001). All patients had MTT-DWI mismatch >20%. There was no significant association between the amount of MTT-DWI mismatch and infarct growth (p=0.33).

CONCLUSIONS

CDM is the most powerful predictor of infarct growth in patients with MCA-M1 occlusion and small infarct core. Most of these patients will have a significant oligemic MTT lesion regardless of admission NIHSS score.

Fluid-Attenuated Inversion Recovery Vascular Hyperintensities–Diffusion-Weighted Imaging Mismatch Identifies Acute Stroke Patients Most Likely to Benefit From Recanalization

Background and Purpose—

Fluid-attenuated inversion recovery vascular hyperintensities (FVH) beyond the boundaries of diffusion-weighted imaging (DWI) lesion (FVH-DWI mismatch) have been proposed as an alternative to perfusion-weighted imaging (PWI)-DWI mismatch. We aimed to establish whether FVH-DWI mismatch can identify patients most likely to benefit from recanalization.

Methods—

FVH-DWI mismatch was assessed in 164 patients with proximal middle cerebral artery occlusion before intravenous thrombolysis. PWI-DWI mismatch (PWI Tmax>6sec /DWI>1.8) was assessed in the 104 patients with available PWI data. We tested the associations between 24-hours complete recanalization on magnetic resonance angiography and 3-month favorable outcome (modified Rankin Scale score ≤2), stratified on FVH-DWI (or PWI-DWI) status.

Results—

FVH-DWI mismatch was present in 121/164 (74%) patients and recanalization in 50/164 (30%) patients. The odds ratio for favorable outcome with recanalization was 16.2 (95% confidence interval, 5.7–46.5; P <0.0001) in patients with FVH-DWI mismatch and 2.6 (95% confidence interval, 0.6–12.1; P =0.22) in those without FVH-DWI mismatch ( P =0.048 for interaction). Recanalization was associated with favorable outcome in patients with PWI-DWI mismatch (odds ratios, 9.9; 95% confidence interval, 3.1–31.3; P =0.0001) and in patients without PWI-DWI mismatch (odds ratios, 7.0; 95% confidence interval, 1.1–44.1; P =0.047), P =0.76 for interaction.

Conclusion—

The FVH-DWI mismatch may rapidly identify patients with proximal occlusion most likely to benefit from recanalization.

Imaging acute ischemic stroke

Acute ischemic stroke is common and often treatable, but treatment requires reliable information on the state of the brain that may be provided by modern neuroimaging. Critical information includes: the presence of hemorrhage; the site of arterial occlusion; the size of the early infarct "core"; and the size of underperfused, potentially threatened brain parenchyma, commonly referred to as the "penumbra." In this chapter we review the major determinants of outcomes in ischemic stroke patients, and the clinical value of various advanced computed tomography and magnetic resonance imaging methods that may provide key physiologic information in these patients. The focus is on major strokes due to occlusions of large arteries of the anterior circulation, the most common cause of a severe stroke syndrome. The current evidence-based approach to imaging the acute stroke patient at the Massachusetts General Hospital is presented, which is applicable for all stroke types. We conclude with new information on time and stroke evolution that imaging has revealed, and how it may open the possibilities of treating many more patients.

Should DWI MRI be the primary screening test for stroke?

Patients presenting with focal neurological symptoms may suffer from ischemic stroke, intracerebral hemorrhage, or stroke mimics. Such patients are usually screened with a noncontrast-enhanced computed tomography to rule out hemorrhage and to detect early signs of ischemia. However, the sensitivity of noncontrast-enhanced computed tomography for acute stroke is far inferior to that of diffusion-weighted magnetic resonance imaging and the latter is also very sensitive for identifying acute intracerebral hemorrhage. Most centers perform a magnetic resonance imaging stroke protocol that takes long to accomplish and may therefore delay therapy. Herein, we propose that a short diffusion-weighted imaging-only magnetic resonance imaging protocol can effectively differentiate ischemic stroke from intracerebral hemorrhage and stroke mimics and could therefore be used as the first line screening test for stroke. Adopting such a screening strategy will result in increased diagnostic accuracy and avoidance of unnecessary treatment of stroke mimics with thrombolysis but may come at the increased cost of performing a magnetic resonance imaging at the emergency department. Whether such a strategy will be cost effective or not remains to be tested in future studies.

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.

Comparison of magnetic resonance imaging mismatch criteria to select patients for endovascular stroke therapy

BACKGROUND AND PURPOSE

The Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution 2 (DEFUSE 2) study has shown that clinical response to endovascular reperfusion differs between patients with and without perfusion-diffusion (perfusion-weighted imaging-diffusion-weighted imaging, PWI-DWI) mismatch: patients with mismatch have a favorable clinical response to reperfusion, whereas patients without mismatch do not. This study examined whether alternative mismatch criteria can also differentiate patients according to their response to reperfusion.

METHODS

Patients from the DEFUSE 2 study were categorized according to vessel occlusion on magnetic resonance angiography (MRA) and DWI lesion volume criteria (MRA-DWI mismatch) and symptom severity and DWI criteria (clinical-DWI mismatch). Favorable clinical response was defined as an improvement of ≥8 points on the National Institutes of Health Stroke Scale (NIHSS) by day 30 or an NIHSS score of ≤1 at day 30. We assessed, for each set of criteria, whether the association between reperfusion and favorable clinical response differed according to mismatch status.

RESULTS

A differential response to reperfusion was observed between patients with and without MRA-DWI mismatch defined as an internal carotid artery or M1 occlusion and a DWI lesion<50 mL. Reperfusion was associated with good functional outcome in patients who met these MRA-DWI mismatch criteria (odds ratio [OR], 8.5; 95% confidence interval [CI], 2.3-31.3), whereas no association was observed in patients who did not meet these criteria (OR, 0.5; 95% CI, 0.08-3.1; P for difference between the odds, 0.01). No differential response to reperfusion was observed with other variations of the MRA-DWI or clinical-DWI mismatch criteria.

CONCLUSIONS

The MRA-DWI mismatch is a promising alternative to DEFUSE 2's PWI-DWI mismatch for patient selection in endovascular stroke trials.

Re-endovascular recanalization for acute middle cerebral artery reocclusion after surgical embolectomy

A 62-year-old woman with atrial fibrillation underwent burr hole trephination for a chronic subdural hematoma. Two days later the patient suddenly presented with motor dysphasia and slightly decreased motor power. Time of flight MR angiography revealed distal M1 occlusion without diffusion restriction. Stent-assisted mechanical thrombectomy was attempted but failed. Post-procedure MRI illustrated a small area of diffusion restriction within the peri-insular and parietal areas. Immediate surgical embolectomy was performed but reocclusion of M1 was documented in the postoperative angiography. Stent-assisted revascularization with a Solitaire stent was conducted and immediate restoration of blood flow was observed. The patient's motor weakness and motor dysphasia recovered fully. Re-endovascular intervention can be beneficial in selected patients for acute middle cerebral artery reocclusion after surgical embolectomy when endovascular thrombectomy fails.

Current perspectives on the use of intravenous recombinant tissue plasminogen activator (tPA) for treatment of acute ischemic stroke

In 1995, the NINDS (National Institute of Neurological Disorders and Stroke) tPA (tissue plasminogen activator) Stroke Study Group published the results of a large multicenter clinical trial demonstrating efficacy of intravenous tPA by revealing a 30% relative risk reduction (absolute risk reduction 11%-15%) compared with placebo at 90 days in the likelihood of having minimal or no disability. Since approval in 1996, tPA remains the only drug treatment for acute ischemic stroke approved by the US Food and Drug Administration. Over the years, an abundance of research and clinical data has supported the safe and efficacious use of intravenous tPA in all eligible patients. Despite such supporting data, it remains substantially underutilized. Challenges to the utilization of tPA include narrow eligibility and treatment windows, risk of symptomatic intracerebral hemorrhage, perceived lack of efficacy in certain high-risk subgroups, and a limited pool of neurological and stroke expertise in the community. With recent US census data suggesting annual stroke incidence will more than double by 2050, better education and consensus among both the medical and lay public are necessary to optimize the use of tPA for all eligible stroke patients. Ongoing and future research should continue to improve upon the efficacy of tPA through more rapid stroke diagnosis and treatment, refinement of advanced neuroimaging and stroke biomarkers, and successful demonstration of alternative means of reperfusion.

DWI reversal is associated with small infarct volume in patients with TIA and minor stroke

BACKGROUND AND PURPOSE

More than half of patients with TIA/minor stroke have ischemic lesions on early DWI, which represent irreversibly damaged tissue. The presence and volume of DWI lesions predict early deterioration in this population. We aimed to study the rate and implications of DWI reversal in patients with TIA/minor stroke.

MATERIALS AND METHODS

Patients with TIA/minor stroke were prospectively enrolled and imaged within 24 hours of onset. Patients were followed for 3 months with repeat MR imaging either at day 30 or 90. Baseline DWI/PWI and follow-up FLAIR final infarct volumes were measured.

RESULTS

Of 418 patients included, 55.5% had DWI and 37% had PWI (time-to-peak of the impulse response ≥2 seconds' delay) lesions at baseline. The median time from symptom onset to baseline and follow-up imaging was 13.4 (interquartile range, 12.7) and 78.73 hours (interquartile range, 60.2), respectively. DWI reversal occurred in 5.7% of patients. The median DWI lesion volume was significantly smaller in those with reversal (0.26 mL, interquartile range = 0.58 mL) compared with those without (1.29 mL, interquartile range = 3.6 mL, P = .002); 72.7% of DWI reversal occurred in cortically based lesions. Concurrent tissue hypoperfusion (time-to-peak of the impulse response ≥2 seconds) was seen in 36.4% of those with DWI reversal versus 62.4% without (P = .08). DWI reversal occurred in 3.3% of patients with penumbral patterns (time-to-peak of the impulse response ≥6 seconds - DWI) > 0 and in 6.8% of those without penumbral patterns (P = .3). The severity of hypoperfusion, defined as greater prolongation of time-to-peak of the impulse response (≥2, ≥4, ≥6, ≥8 seconds), did not affect the likelihood of DWI reversal (linear trend, P = .147). No patient with DWI reversal had an mRS score of ≥2 at 90 days versus 18.2% of those without reversal (P = .02).

CONCLUSIONS

DWI reversal is uncommon in patients with TIA/minor stroke and is more likely to occur in those with smaller baseline lesions. DWI reversal should not have a significant effect on the accuracy of penumbra definition.

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.

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.

Impact of diffusion-weighted imaging lesion volume on the success of endovascular reperfusion therapy

BACKGROUND AND PURPOSE

Diffusion-weighted imaging (DWI) lesion volume is associated with poor outcome after thrombolysis, and it is unclear whether endovascular therapies are beneficial for large DWI lesion. Our aim was to assess the impact of pretreatment DWI lesion volume on outcomes after endovascular therapy, with a special emphasis on patients with complete recanalization.

METHODS

We analyzed data collected between April 2007 and November 2011 in a prospective clinical registry. All acute ischemic stroke patients with complete occlusion of internal carotid artery or middle cerebral artery treated by endovascular therapy were included. DWI lesion volumes were measured by the RAPID software. Favorable outcome was defined by modified Rankin Scale of 0 to 2 at 90 days.

RESULTS

A total of 139 acute ischemic stroke patients were included. Median DWI lesion volume was 14 cc (interquartile range, 5-43) after a median onset time to imaging of 110 minutes (interquartile range, 77-178). Higher volume was associated with less favorable outcome (adjusted odds ratio, 0.55; 95% confidence interval, 0.31-0.96). A complete recanalization was achieved in 65 (47%) patients after a median onset time of 238 minutes (interquartile range, 206-285). After adjustment for volume, complete recanalization was associated with more favorable outcome (adjusted odds ratio, 6.32; 95% confidence interval, 2.90-13.78). After stratification of volume by tertiles, complete recanalization was similarly associated with favorable outcome in the upper 2 tertiles (P<0.005).

CONCLUSIONS

Our results emphasize the importance of initial DWI volume and recanalization on clinical outcome after endovascular treatment. Large DWI lesions may still benefit from recanalization in selected patients.

Re-endovascular recanalization for acute middle cerebral artery reocclusion after surgical embolectomy

A 62-year-old woman with atrial fibrillation underwent burr hole trephination for a chronic subdural hematoma. Two days later the patient suddenly presented with motor dysphasia and slightly decreased motor power. Time of flight MR angiography revealed distal M1 occlusion without diffusion restriction. Stent-assisted mechanical thrombectomy was attempted but failed. Post-procedure MRI illustrated a small area of diffusion restriction within the peri-insular and parietal areas. Immediate surgical embolectomy was performed but reocclusion of M1 was documented in the postoperative angiography. Stent-assisted revascularization with a Solitaire stent was conducted and immediate restoration of blood flow was observed. The patient's motor weakness and motor dysphasia recovered fully. Re-endovascular intervention can be beneficial in selected patients for acute middle cerebral artery reocclusion after surgical embolectomy when endovascular thrombectomy fails.

Advanced multimodal CT/MRI approaches to hyperacute stroke diagnosis, treatment, and monitoring

Multimodal CT/MRI has dramatically changed the approach to ischemic stroke management, as noninvasive CT/MRI images detail brain tissue or parenchyma, angiography or vessel status, and collateral perfusion or blood flow in regions of the brain vulnerable to ischemic injury. Such snapshots of the dynamic process of cerebral ischemia may be used to gauge reversibility and therapeutic opportunities. Treatment of acute stroke may be rapidly tailored to clinical scenarios based on imaging correlation of ischemia, vessel status, and perfusion. Serial or repeated imaging from the initial presentation to later stages of the hospital course may illustrate infarct growth, persisting occlusion, reocclusion, recanalization, reperfusion, and hemorrhagic transformation. From acute stroke to rehabilitation phases and subsequent prevention, multimodal CT/MRI has emerged as a key tool to track the process of stroke and the impact of our therapeutic interventions.

Leukoaraiosis and sex predict the hyperacute ischemic core volume

BACKGROUND AND PURPOSE

Leukoaraiosis (LA) and male sex have been associated with decreased cerebrovascular reactivity, which potentially adversely affects tissue viability in acute stroke. Therefore, we aimed to elucidate the contribution of LA-severity and sex to the extent of the hyperacute ischemic core volume after intracranial large artery occlusion.

METHODS

We analyzed data from 87 patients with acute intracranial large artery occlusion who had acute multimodal computed tomography-imaging. LA-severity was assessed using the van Swieten scale on noncontrast computed tomography. Computed tomography perfusion data were analyzed using automatic calculation of the mean transit time and hyperacute cerebral blood volume defects. Multivariate linear and logistic regression analyses were used to identify independent predictors of the hyperacute infarct-volume.

RESULTS

Severe LA (van Swieten Scale, 3-4; odds ratio, 43.22; 95% CI, 6.26-298.42; P<0.001) and male sex (odds ratio, 7.52; 95% CI, 1.38-40.86; P=0.020) were independently associated with a hyperacute cerebral blood volume-lesion >25 mL on multivariate logistic regression analysis. Multivariate linear regression analysis confirmed the association between severe LA (P<0.001) and male sex (P=0.01) with larger cerebral blood volume-lesions. There was no significant difference in the absolute or relative mean transit time-lesion volumes when stratified by LA-severity or sex. Women had significantly smaller cerebral blood volume-lesion volumes compared with men (P=0.036).

CONCLUSIONS

Severe LA and male sex are associated with larger infarct cores, which adds to the notion that sex and LA alter the brain's intrinsic susceptibility to acute cerebral ischemia. Future, larger studies are needed to confirm our observation that women have smaller core volumes and its significance.

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.

Platelet derived growth factor-CC isoform is associated with hemorrhagic transformation in ischemic stroke patients treated with tissue plasminogen activator

OBJECTIVE

Platelet derived growth factor-CC (PDGF-CC) isoform is activated by tissue plasminogen activator (tPA) regulating blood brain barrier permeability after ischemia. We aimed to study the association of PDGF isoforms serum levels with hemorrhagic transformation (HT) and edema after thrombolytic treatment in ischemic stroke.

METHODS

We studied 129 patients with ischemic stroke treated with tPA within the first 4.5 h (h) from stroke onset. CT was performed on admission and at 24-36 h. On the 2nd CT, HT was classified according to ECASS II criteria, and severe brain edema was diagnosed if extensive swelling causing any shifting of the structures of the midline was detected. PDGF-AA, PDGF-AB, PDGF-BB and PDGF-CC serum levels were analyzed by ELISA on admission (before tPA bolus), at 24 and 72 h.

RESULTS

Patients who developed HT showed only higher levels of PDGF-CC isoform on admission and at 24 h (all p < 0.0001). In the multivariate analysis, PDGF-CC levels on admission (OR, 1.02; CI 95%, 1.00-1.04) and at 24 h (OR, 1.05; CI 95%, 1.02-1.08) were independently associated with HT after adjustment by confounding factors. On the other hand, patients with severe edema showed also higher levels of PDGF-CC on admission and at 24 h (p < 0.0001), but this statistical association was lost in the logistic regression analysis. PDGF-CC levels ≥ 175 ng/mL at 24 h predict the development of PH with a sensitivity of 90% and specificity of 88% (area under the curve 0.936; p < 0.0001).

CONCLUSION

Increased PDGF-CC levels after tPA treatment is associated with HT.

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.

Refining the mismatch concept in acute stroke: lessons learned from PET and MRI

In ischemic stroke, positron-emission tomography (PET) established the imaging-based concept of penumbra. It defines hypoperfused, but functionally impaired, tissue with preserved viability that can be rescued by timely reperfusion. Diffusion-weighted and perfusion-weighted (PW) magnetic resonance imaging (MRI) translated the concept of penumbra to the concept of mismatch. However, the use of mismatch-based patient stratification for reperfusion therapy remains a matter of debate. The equivalence of mismatch and penumbra, as well as the validity of the classical mismatch concept is questioned for several reasons. First, methodological differences between PET and MRI lead to different definitions of the tissue at risk. Second, the mismatch concept is still poorly standardized among imaging facilities causing relevant variability in stroke research. Third, relevant conceptual issues (e.g., the choice of the adequate perfusion measure, the best quantitative approach to perfusion maps, and the required size of the mismatch) need further refinement. Fourth, the use of single thresholds does not account for the physiological heterogeneity of the penumbra and probabilistic approaches may be more promising. The implementation of this current knowledge into an optimized state-of-the-art mismatch model and its validation in clinical stroke studies remains a major challenge for future stroke research.

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.

Improved outcome prediction using CT angiography in addition to standard ischemic stroke assessment: results from the STOPStroke study

PURPOSE

To improve ischemic stroke outcome prediction using imaging information from a prospective cohort who received admission CT angiography (CTA).

METHODS

In a prospectively designed study, 649 stroke patients diagnosed with acute ischemic stroke had admission NIH stroke scale scores, noncontrast CT (NCCT), CTA, and 6-month outcome assessed using the modified Rankin scale (mRS) scores. Poor outcome was defined as mRS>2. Strokes were classified as "major" by the (1) Alberta Stroke Program Early CT Score (ASPECTS+) if NCCT ASPECTS was ≤7; (2) Boston Acute Stroke Imaging Scale (BASIS+) if they were ASPECTS+ or CTA showed occlusion of the distal internal carotid, proximal middle cerebral, or basilar arteries; and (3) NIHSS for scores >10.

RESULTS

Of 649 patients, 253 (39.0%) had poor outcomes. NIHSS, BASIS, and age, but not ASPECTS, were independent predictors of outcome. BASIS and NIHSS had similar sensitivities, both superior to ASPECTS (p<0.0001). Combining NIHSS with BASIS was highly predictive: 77.6% (114/147) classified as NIHSS>10/BASIS+ had poor outcomes, versus 21.5% (77/358) with NIHSS≤10/BASIS- (p<0.0001), regardless of treatment. The odds ratios for poor outcome is 12.6 (95% CI: 7.9 to 20.0) in patients who are NIHSS>10/BASIS+ compared to patients who are NIHSS≤10/BASIS-; the odds ratio is 5.4 (95% CI: 3.5 to 8.5) when compared to patients who are only NIHSS>10 or BASIS+.

CONCLUSIONS

BASIS and NIHSS are independent outcome predictors. Their combination is stronger than either instrument alone in predicting outcomes. The findings suggest that CTA is a significant clinical tool in routine acute stroke assessment.

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.

Imaging-based treatment selection for intravenous and intra-arterial stroke therapies: a comprehensive review

Reperfusion therapy is the only approved treatment for acute ischemic stroke. The current approach to patient selection is primarily based on the time from stroke symptom onset. However, this algorithm sharply restricts the eligible patient population, and neglects large variations in collateral circulation that ultimately determine the therapeutic time window in individual patients. Time alone is unlikely to remain the dominant parameter. Alternative approaches to patient selection involve advanced neuroimaging methods including MRI diffusion-weighted imaging, magnetic resonance and computed tomography perfusion imaging and noninvasive angiography that provide potentially valuable information regarding the state of the brain parenchyma and the neurovasculature. These techniques have now been used extensively, and there is emerging evidence on how specific imaging data may result in improved clinical outcomes. This article will review the major studies that have investigated the role of imaging in patient selection for both intravenous and intra-arterial therapies.

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.

Predicting acute ischaemic stroke outcome using clinical and temporal thresholds

Background. Few studies have analysed the natural course of cerebral ischaemia for predicting outcome. We aimed to determine the early clinical findings and the thresholds for deficit severity and symptom duration that make it possible to stratify outcome. Methods. We included 154 patients with transient ischaemic attack or ischaemic stroke. Stroke profiles and neurological status were assessed from onset to 24 hrs, on admission, at 48 hrs, and at discharge. Outcomes were evaluated using the modified Rankin Scale. Positive and negative predictive values were calculated for the different thresholds. The model was subsequently evaluated on a new prospective cohort of 157 patients. Results. Initial National Institute of Health Stroke Scale (NIHSS) score <5 and symptoms regressing within 135 min were predictive of good outcome. Initial NIHSS score >22 and symptom stability after 1,230 min were predictive of physical dependency or death. Conclusions. Low and high NIHSS cut-off points are effective positive predictive values for good and poor outcomes. Thresholds for symptom duration are less conclusive.

Predictors of good clinical outcome in acute stroke patients treated with intravenous thrombolysis

OBJECTIVES

Intravenous thrombolysis (IVT) is considered an effective treatment for acute ischemic stroke (IS). However, not all treated patients may achieve good outcome. The aim was to evaluate whether the initial NIHSS and DWI infarct volume could be the predictors for good outcome after IVT.

PATIENTS AND METHODS

The set of 125 patients with consecutive hemispheric IS (78 men; mean age 66.0 ± 12.1 years) treated with IVT within 3 h was analyzed. DWI volume was measured on admission. Good outcome was defined as a score 0-2 in modified Rankin Scale.

RESULTS

Multivariate logistic regression analysis showed initial NIHSS as an independent predictor of good outcome (P = 0.001). ROC curves showed baseline NIHSS ≤13.5 points and DWI volume ≤13.7 ml as cut-offs related to good outcome.

CONCLUSIONS

The initial NIHSS and DWI volume might be the predictors for good clinical outcome in acute stroke patients treated with IVT. The initial NIHSS score seems to be more accurate.

Longitudinal studies of ischemic penumbra by using 18F-FDG PET and MRI techniques in permanent and transient focal cerebral ischemia in rats

At present, the goal of stroke research is the identification of a potential recoverable tissue surrounding the ischemic core, suggested as ischemic penumbra, with the aim of applying a treatment that attenuates the growth of this area. Our purpose was to determine whether a combination of imaging techniques, including (18)F-FDG PET and MRI could identify the penumbra area. Longitudinal studies of (18)F-FDG PET and MRI were performed in rats 3 h, 24 h and 48 h after the onset of ischemia. A transient and a permanent model of focal cerebral ischemia were performed. Regions of interest were located, covering the ischemic core, the border that progresses to infarction (recruited tissue), and the border that recovers (recoverable tissue) with early reperfusion. Analyses show that permanent ischemia produces severe damage, whereas the transient ischemia model does not produce clear damage in ADC maps at the earliest time studied. The only significant differences between values for recoverable tissue, (18)F-FDG (84±2%), ADC (108±5%) and PWI (70±8%), and recruited tissue, (18)F-FDG (77±3%), ADC (109±4%) and PWI (77±4%), are shown in (18)F-FDG ratios. We also show that recoverable tissue values are different from those in non-infarcted tissue. The combination of (18)F-FDG PET, ADC and PWI MRI is useful for identification of ischemic penumbra, with (18)F-FDG PET being the most sensitive approach to its study at early times after stroke, when a clear DWI deficit is not observed.

Targeting the Ischemic Penumbra

Background—

In the last 3 decades, and from a therapeutic point of view, the classical concept of ischemic penumbra based on hemodynamic and electrophysiological parameters has loosened up the rigidity of therapeutic windows in acute stroke management. Thirty years later, the ischemic penumbra is an evolved concept that presents more applications. Thus, the ischemic penumbra is a diagnostic target, allowing the extension of therapeutic windows; it is also a biochemical target, in which an intermittent bioenergetic compromise takes place, and it is a target for brain plasticity, neuroprotection, and neurorepair.

Summary of Review—

In this work, we review how the concept of ischemic penumbra has been evolving from its purely electrophysiological/ hemodynamic based definition to the wider metabolic–cellular–therapeutic concept that is managed today by neuroscientists.

Combining acute diffusion-weighted imaging and mean transmit time lesion volumes with National Institutes of Health Stroke Scale Score improves the prediction of acute stroke outcome

BACKGROUND AND PURPOSE

The purpose of this study was to determine whether acute diffusion-weighted imaging (DWI) and mean transit time (MTT) lesion volumes and presenting National Institutes of Health Stroke Scale (NIHSS) can identify patients with acute ischemic stroke who will have a high probability of good and poor outcomes.

METHODS

Fifty-four patients with acute ischemic stroke who had MRI within 9 hours of symptom onset and 3-month follow-up with modified Rankin scale were evaluated. Acute DWI and MTT lesion volumes and baseline NIHSS scores were calculated. Clinical outcomes were considered good if the modified Rankin Scale was 0 to 2.

RESULTS

The 33 of 54 (61%) patients with good outcomes had significantly smaller DWI lesion volumes (P=0.0001), smaller MTT lesion volumes (P<0.0001), and lower NIHSS scores (P<0.0001) compared with those with poor outcomes. Receiver operating characteristic curves for DWI, MTT, and NIHSS relative to poor outcome had areas under the curve of 0.889, 0.854, and 0.930, respectively, which were not significantly different. DWI and MTT lesion volumes predicted outcome better than mismatch volume or percentage mismatch. All patients with a DWI volume >72 mL (13 of 54) and an NIHSS score >20 (6 of 54) had poor outcomes. All patients with an MTT volume of <47 mL (16 of 54) and an NIHSS score <8 (17 of 54) had good outcomes. Combining clinical and imaging thresholds improved prognostic yield (70%) over clinical (43%) or imaging (54%) thresholds alone (P=0.01).

CONCLUSIONS

Combining quantitative DWI and MTT with NIHSS predicts good and poor outcomes with high probability and is superior to NIHSS alone.