Perfusion Imaging and Clinical Outcome in Acute Ischemic Stroke with Large Core

OBJECTIVE

Mechanical thrombectomy (MT) is not recommended for acute stroke with large vessel occlusion (LVO) and a large volume of irreversibly injured tissue ("core"). Perfusion imaging may identify a subset of patients with large core who benefit from MT.

METHODS

We compared two cohorts of LVO-related patients with large core (>50 ml on diffusion-weighted-imaging or CT-perfusion using RAPID), available perfusion imaging, and treated within 6 hours from onset by either MT + Best Medical Management (BMM) in one prospective study, or BMM alone in the pre-MT era from a prospective registry. Primary outcome was 90-day modified Rankin Scale ≤2. We searched for an interaction between treatment group and amount of penumbra as estimated by the mismatch ratio (MMRatio = critical hypoperfusion/core volume).

RESULTS

Overall, 107 patients were included (56 MT + BMM and 51 BMM): Mean age was 68 ± 15 years, median core volume 99 ml (IQR: 72-131) and MMRatio 1.4 (IQR: 1.0-1.9). Baseline clinical and radiological variables were similar between the two groups, except for a higher intravenous thrombolysis rate in the BMM group. The MMRatio strongly modified the clinical outcome following MT (p_interaction  < 0.001 for continuous MMRatio); MT was associated with a higher rate of good outcome in patients with, but not in those without, MMRatio>1.2 (adjusted OR [95% CI] = 6.8 [1.7-27.0] vs 0.7 [0.1-6.2], respectively). Similar findings were present for MMRatio ≥1.8 in the subgroup with core ≥70 ml. Parenchymal hemorrhage on follow-up imaging was more frequent in the MT + BMM group regardless of the MMRatio.

INTERPRETATION

Perfusion imaging may help select which patients with large core should be considered for MT. Randomized studies are warranted. ANN NEUROL 2021.

The core/penumbra model: implications for acute stroke treatment and patient selection in 2021

Despite major advances in prevention, ischaemic stroke remains one of the leading causes of death and disability worldwide. After centuries of nihilism and decades of failed neuroprotection trials, the discovery, initially in non-human primates and subsequently in man, that ischaemic brain tissue termed the ischaemic penumbra can be salvaged from infarction up to and perhaps beyond 24 h after stroke onset has underpinned the development of highly efficient reperfusion therapies, namely intravenous thrombolysis and endovascular thrombectomy, which have revolutionized the management of the acute stroke patient. Animal experiments have documented that how long the penumbra can survive depends not only on time elapsed since arterial occlusion ('time is brain'), but also on how severely perfusion is reduced. Novel imaging techniques allowing the penumbra and the already irreversibly damaged core in the individual subject to be mapped have documented that the time course of core growth at the expense of the penumbra widely differs from patient to patient, and hence that individual physiology should be considered in addition to time since stroke onset for decision-making. This concept has been implemented to optimize patient selection in pivotal trials of reperfusion therapies beyond 3 h after stroke onset and is now routinely applied in clinical practice, using computed tomography or magnetic resonance imaging. The notion that, in order to be both efficient and harmless, treatment should be tailored to each patient's physiological characteristics represents a radical move towards precision medicine.

Recovery and Prediction of Bimanual Hand Use After Stroke

OBJECTIVE

To determine similarities and differences in key predictors of recovery of bimanual hand use and unimanual motor impairment after stroke.

METHOD

In this prospective longitudinal study, 89 patients with first-ever stroke with arm paresis were assessed at 3 weeks and 3 and 6 months after stroke onset. Bimanual activity performance was assessed with the Adult Assisting Hand Assessment Stroke (Ad-AHA), and unimanual motor impairment was assessed with the Fugl-Meyer Assessment (FMA). Candidate predictors included shoulder abduction and finger extension measured by the corresponding FMA items (FMA-SAFE; range 0-4) and sensory and cognitive impairment. MRI was used to measure weighted corticospinal tract lesion load (wCST-LL) and resting-state interhemispheric functional connectivity (FC).

RESULTS

Initial Ad-AHA performance was poor but improved over time in all (mild-severe) impairment subgroups. Ad-AHA correlated with FMA at each time point (r > 0.88, p < 0.001), and recovery trajectories were similar. In patients with moderate to severe initial FMA, FMA-SAFE score was the strongest predictor of Ad-AHA outcome (R ² = 0.81) and degree of recovery (R ² = 0.64). Two-point discrimination explained additional variance in Ad-AHA outcome (R ² = 0.05). Repeated analyses without FMA-SAFE score identified wCST-LL and cognitive impairment as additional predictors. A wCST-LL >5.5 cm³ strongly predicted low to minimal FMA/Ad-AHA recovery (≤10 and 20 points respectively, specificity = 0.91). FC explained some additional variance to FMA-SAFE score only in unimanual recovery.

CONCLUSION

Although recovery of bimanual activity depends on the extent of corticospinal tract injury and initial sensory and cognitive impairments, FMA-SAFE score captures most of the variance explained by these mechanisms. FMA-SAFE score, a straightforward clinical measure, strongly predicts bimanual recovery.

CLINICALTRIALSGOV IDENTIFIER

NCT02878304.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that the FMA-SAFE score predicts bimanual recovery after stroke.

Cathodal Transcranial Direct Current Stimulation in Acute Ischemic Stroke: Pilot Randomized Controlled Trial

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Temporary application of lower body positive pressure improves intracranial velocities in symptomatic acute carotid occlusion or tight stenosis: A pilot study

BACKGROUND

Patients with isolated cervical carotid artery occlusion not eligible to recanalization therapies but with compromised intracranial hemodynamics may be at risk of further clinical events. Apart from lying flat until spontaneous recanalization or adjustment of the collateral circulation hopefully occurs, no specific treatment is currently implemented. Improving collateral flow is an attractive option in this setting. Lower body positive pressure (LBPP) is known to result in rapid venous blood shift from the lower to the upper body part, in turn improving cardiac preload and output, and is routinely used in acute hemorrhagic shock. We report here cerebral blood flow velocities measured during LBPP in this patient population.

METHODS

This is a retrospective analysis of the clinical, physiological, and transcranial Doppler monitoring data collected during and 15 min after LBPP in 21 consecutive patients (10 females, median age: 54 years) with recently symptomatic isolated carotid occlusion/tight stenosis (unilateral in 18) mostly due to atherosclerosis or dissection. LBPP was applied for 90 min at a median 5 days after symptom onset.

RESULTS

At baseline, middle-cerebral artery velocities were markedly lower on the symptomatic, as compared to asymptomatic, side. LBPP significantly improved blood flow velocities in both the symptomatic and asymptomatic middle-cerebral artery as well as the basilar artery, which persisted 15 min after discontinuing the procedure. LBPP also resulted in mild but significant increases in mean arterial blood pressure.

CONCLUSIONS

LBPP improved intracranial hemodynamics downstream recently symptomatic carotid occlusion/tight stenosis as well as in the contralateral and posterior circulations, which persisted after LBPP deflation. Randomized trials should determine if this easy-to-use, noninvasive, nonpharmacologic approach has long-lasting benefits on the intracranial circulation and improves functional outcome.

Prediction of Early Neurological Deterioration in Individuals With Minor Stroke and Large Vessel Occlusion Intended for Intravenous Thrombolysis Alone

Importance

The best reperfusion strategy in patients with acute minor stroke and large vessel occlusion (LVO) is unknown. Accurately predicting early neurological deterioration of presumed ischemic origin (ENDi) following intravenous thrombolysis (IVT) in this population may help to select candidates for immediate transfer for additional thrombectomy.

Objective

To develop and validate an easily applicable predictive score of ENDi following IVT in patients with minor stroke and LVO.

Design, Setting, and Participants

This multicentric retrospective cohort included 729 consecutive patients with minor stroke (National Institutes of Health Stroke Scale [NIHSS] score of 5 or less) and LVO (basilar artery, internal carotid artery, first [M1] or second [M2] segment of middle cerebral artery) intended for IVT alone in 45 French stroke centers, ie, including those who eventually received rescue thrombectomy because of ENDi. For external validation, another cohort of 347 patients with similar inclusion criteria was collected from 9 additional centers. Data were collected from January 2018 to September 2019.

Main Outcomes and Measures

ENDi, defined as 4 or more points' deterioration on NIHSS score within the first 24 hours without parenchymal hemorrhage on follow-up imaging or another identified cause.

Results

Of the 729 patients in the derivation cohort, 335 (46.0%) were male, and the mean (SD) age was 70 (15) years; of the 347 patients in the validation cohort, 190 (54.8%) were male, and the mean (SD) age was 69 (15) years. In the derivation cohort, the median (interquartile range) NIHSS score was 3 (1-4), and the occlusion site was the internal carotid artery in 97 patients (13.3%), M1 in 207 (28.4%), M2 in 395 (54.2%), and basilar artery in 30 (4.1%). ENDi occurred in 88 patients (12.1%; 95% CI, 9.7-14.4) and was strongly associated with poorer 3-month outcomes, even in patients who underwent rescue thrombectomy. In multivariable analysis, a more proximal occlusion site and a longer thrombus were independently associated with ENDi. A 4-point score derived from these variables-1 point for thrombus length and 3 points for occlusion site-showed good discriminative power for ENDi (C statistic = 0.76; 95% CI, 0.70-0.82) and was successfully validated in the validation cohort (ENDi rate, 11.0% [38 of 347]; C statistic = 0.78; 95% CI, 0.70-0.86). In both cohorts, ENDi probability was approximately 3%, 7%, 20%, and 35% for scores of 0, 1, 2 and 3 to 4, respectively.

Conclusions and Relevance

The substantial ENDi rates observed in these cohorts highlights the current debate regarding whether to directly transfer patients with IVT-treated minor stroke and LVO for additional thrombectomy. Based on the strong associations observed, an easily applicable score for ENDi risk prediction that may assist decision-making was derived and externally validated.

Abstract 36: The Boston Criteria V2.0 for Cerebral Amyloid Angiopathy: Updated Criteria and Multicenter MRI-Neuropathology Validation

Introduction: The Boston criteria are used worldwide for in vivo diagnosis of cerebral amyloid angiopathy (CAA). Given substantial advances in CAA research, we aimed to update the Boston criteria and externally validate their diagnostic accuracy across the spectrum of CAA-related presentations and across international sites.

Methods: As part of an International CAA Association multicenter study, we identified patients age 50 or older with potential CAA-related clinical presentations (spontaneous intracerebral hemorrhage, cognitive impairment, or transient focal neurological episodes), available brain MRI, and histopathologic assessment for the diagnosis of CAA. We derived Boston criteria v2.0 by selecting MRI features to optimize diagnostic specificity and sensitivity in a pre-specified derivation sample (Boston cases 1994 to 2012, n=159), then externally validated in pre-specified temporal (Boston cases 2012-2018, n=59) and geographical (non-Boston cases 2004-2018; n=123) validation samples and compared their diagnostic accuracy to the currently used modified Boston criteria.

Results: Based on exploratory analyses in the derivation sample, we derived provisional criteria for probable CAA requiring presence of at least 2 strictly lobar hemorrhagic lesions (intracerebral hemorrhage, cerebral microbleed, or cortical superficial siderosis focus) or at least 1 strictly lobar hemorrhagic lesion and 1 white matter characteristic (severe degree of visible perivascular spaces in centrum semiovale or white matter hyperintensities multispot pattern). Sensitivity/specificity of the criteria were 74.8/84.6% in the derivation sample, 92.5/89.5% in the temporal validation sample, 80.2/81.5% in the geographic validation sample, and 74.5/95.0% in cases across all samples with autopsy as the diagnostic gold standard. The v2.0 criteria for probable CAA had superior accuracy to the currently modified Boston criteria (p<0.005) in the autopsied cases.

Conclusion: The Boston criteria v.2.0 incorporate emerging MRI markers of CAA to enhance sensitivity without compromising their high specificity. Validation of the criteria across independent patient settings firmly supports their adoption into clinical practice and research.

Brain Glucose Metabolism in Cerebral Amyloid Angiopathy: An FDG-PET Study

BACKGROUND AND PURPOSE

The in vivo diagnosis of cerebral amyloid angiopathy (CAA) is currently based on the Boston criteria, which largely rely on hemorrhagic features on brain magnetic resonance imaging. Adding to these criteria ¹⁸F-fluoro-deoxy-D-glucose (FDG) positron emission tomography, a widely available imaging modality, might improve their accuracy. Here we tested the hypothesis that FDG uptake is reduced in posterior cortical areas, particularly the primary occipital cortex, which pathologically bear the brunt of vascular Aβ deposition.

METHODS

From a large memory clinic database, we retrospectively included all patients in whom both brain magnetic resonance imaging and FDG positron emission tomography had been obtained as part of routine clinical care and who fulfilled the Boston criteria for probable CAA. None had a history of symptomatic intracerebral hemorrhage. FDG data processing involved (1) spatial normalization to the Montreal Neurology Institute/International Consortium for Brain Mapping 152 space and (2) generation of standardized FDG uptake (relative standardized uptake value; relative to the pons). The relative standardized uptake value data obtained in 13 regions of interest sampling key cortical areas and the cerebellum were compared between the CAA and age-matched control groups using 2 separate healthy subject databases and image-processing pipelines. The presence of significant hypometabolism (2-tailed P<0.05) was assessed for the bilaterally averaged regions-of-interest relative standardized uptake values.

RESULTS

Fourteen patients fulfilling the Boston criteria for probable CAA (≥2 exclusively lobar microbleeds) were identified. Significant hypometabolism (P range, 0.047 to <0.0001) consistently affected the posterior cortical areas, including the superior and inferior parietal, primary visual, lateral occipital, lateral temporal, precuneus, and posterior cingulate regions of interest. The anterior cortical areas were marginally or not significantly hypometabolic, and the cerebellum was spared.

CONCLUSIONS

Supporting our hypothesis, significant glucose hypometabolism predominantly affected posterior cortical regions, including the visual cortex. These findings from a small sample may have diagnostic implications but require replication in larger prospective studies. In addition, whether they generalize to CAA-related symptomatic intracerebral hemorrhage warrants specific studies.

[18 F]FDG PET may differentiate cerebral amyloid angiopathy from Alzheimer's disease

BACKGROUND

Cerebral amyloid angiopathy (CAA) is a frequent cause of both intracerebral hemorrhage (ICH) and cognitive impairment in the elderly. Diagnosis relies on the Boston criteria, which use magnetic resonance imaging markers including ≥2 exclusively lobar cerebral microbleeds (lCMBs). Although amyloid positron emission tomography (PET) may provide molecular diagnosis, its specificity relative to Alzheimer's disease (AD) is limited due to the prevalence of positive amyloid PET in cognitively normal elderly. Using early-phase ¹¹ C-Pittsburgh compound B as surrogate for tissue perfusion, a significantly lower occipital/posterior cingulate (O/PC) tracer uptake ratio in probable CAA relative to AD was recently reported, consistent with histopathological lesion distribution. We tested whether this finding could be reproduced using [¹⁸ F]fluorodeoxyglucose (FDG)-PET, a widely available modality that correlates well with early-phase amyloid PET in both healthy subjects and AD.

METHODS

From a large memory clinic database, we retrospectively included 14 patients with probable CAA (Boston criteria) and 21 patients with no lCMB fulfilling AD criteria including cerebrospinal fluid biomarkers. In all, [¹⁸ F]FDG-PET/computed tomography (CT) was available as part of routine care. No subject had a clinical history of ICH. Regional standardized [¹⁸ F]FDG uptake values normalized to the pons (standard uptake value ratio [SUVr]) were obtained, and the O/PC ratio was calculated.

RESULTS

The SUVr O/PC ratio was significantly lower in CAA versus AD (1.02 ± 0.14 vs. 1.19 ± 0.18, respectively; p = 0.024).

CONCLUSIONS

Despite the small sample, our findings are consistent with the previous early-phase amyloid PET study. Thus, [¹⁸ F]FDG-PET may help differentiate CAA from AD, particularly in cases of amyloid PET positivity. Larger prospective studies, including in CAA-related ICH, are however warranted.

Tissue no-reflow despite full recanalization following thrombectomy for anterior circulation stroke with proximal occlusion: A clinical study

Despite early thrombectomy, a sizeable fraction of acute stroke patients with large vessel occlusion have poor outcome. The no-reflow phenomenon, i.e. impaired microvascular reperfusion despite complete recanalization, may contribute to such "futile recanalizations". Although well reported in animal models, no-reflow is still poorly characterized in man. From a large prospective thrombectomy database, we included all patients with intracranial proximal occlusion, complete recanalization (modified thrombolysis in cerebral infarction score 2c-3), and availability of both baseline and 24 h follow-up MRI including arterial spin labeling perfusion mapping. No-reflow was operationally defined as i) hypoperfusion ≥40% relative to contralateral homologous region, assessed with both visual (two independent investigators) and automatic image analysis, and ii) infarction on follow-up MRI. Thirty-three patients were eligible (median age: 70 years, NIHSS: 18, and stroke onset-to-recanalization delay: 208 min). The operational criteria were met in one patient only, consistently with the visual and automatic analyses. This patient recanalized 160 min after stroke onset and had excellent functional outcome. In our cohort of patients with complete and stable recanalization following thrombectomy for intracranial proximal occlusion, severe ipsilateral hypoperfusion on follow-up imaging associated with newly developed infarction was a rare occurrence. Thus, no-reflow may be infrequent in human stroke and may not substantially contribute to futile recanalizations.

Intended Bridging Therapy or Intravenous Thrombolysis Alone in Minor Stroke With Basilar Artery Occlusion

BACKGROUND AND PURPOSE

Whether bridging therapy (intravenous thrombolysis [IVT] followed by mechanical thrombectomy) is superior to IVT alone in minor stroke with basilar artery occlusion remains uncertain.

METHODS

Multicentric retrospective observational study of consecutive minor stroke patients (National Institutes of Health Stroke Scale score ≤5) with basilar artery occlusion intended for IVT alone or bridging therapy. Propensity-score weighting was used to reduce baseline between-groups differences, and residual imbalance was addressed through adjusted logistic regression, with excellent outcome (3-month modified Rankin Scale score 0-1) as the dependent variable.

RESULTS

Fifty-seven patients were included (28 and 29 in the bridging therapy and IVT alone groups, respectively). Following propensity-score weighting, the distribution of baseline clinical and radiological variables was similar across the 2 patient groups, except age, posterior circulation Alberta Stroke Program Early CT Score, history of hypertension and smoking, and onset-to-IVT time. Compared with IVT alone, bridging therapy was associated with excellent outcome (adjusted odds ratio=3.37 [95% CI, 1.13-10.03]; P=0.03). No patient experienced symptomatic intracranial hemorrhage.

CONCLUSIONS

Our results suggest that bridging therapy may be superior to IVT alone in minor stroke with basilar artery occlusion.

The ischemic penumbra: From concept to reality

The discovery that brain tissue could potentially be salvaged from ischaemia due to stroke, has led to major advances in the development of therapies for ischemic stroke. In this review, we detail the advances in the understanding of this area termed the ischaemic penumbra, from its discovery to the evolution of imaging techniques, and finally some of the treatments developed. Evolving from animal studies from the 70s and 80s and translated to clinical practice, the field of ischemic reperfusion therapy has largely been guided by an array of imaging techniques developed to positively identify the ischemic penumbra, including positron emission tomography, computed tomography and magnetic resonance imaging. More recently, numerous penumbral identification imaging studies have allowed for a better understanding of the progression of the ischaemic core at the expense of the penumbra, and identification of patients than can benefit from reperfusion therapies in the acute phase. Importantly, 40 years of critical imaging research on the ischaemic penumbra have allowed for considerable extension of the treatment time window and better patient selection for reperfusion therapy. The translation of the penumbra concept into routine clinical practice has shown that "tissue is at least as important as time."

Early-stage 11C-Flumazenil PET predicts day-14 selective neuronal loss in a rodent model of transient focal cerebral ischemia

Predicting tissue outcome early after stroke is an important goal. MRI >3 h accurately predicts infarction but is insensitive to selective neuronal loss (SNL). Previous studies suggest that chronic-stage ¹¹C-flumazenil PET (FMZ-PET) is a validated marker of SNL in rats, while early-stage FMZ-PET may predict infarction. Whether early FMZ-PET also predicts SNL is unknown. Following 45-min distal MCA occlusion, adult rats underwent FMZ-PET at 1 h and 48 h post-reperfusion to map distribution volume (V_T), which reflects GABA-_A receptor binding. NeuN immunohistochemistry was performed at Day 14. In each rat, V_T and %NeuN loss were determined in 44 ROIs spanning the hemisphere. NeuN revealed isolated SNL and cortical infarction in five and one rats, respectively. In the SNL subgroup, V_T-1 h was mildly reduced and only weakly predicted SNL, while V_T-48 h was significantly increased and predicted SNL both individually (p < 0.01, Kendall) and across the group (p < 0.001), i.e. the higher the V_T, the stronger the SNL. Similar correlations were found in the rat with infarction. Our findings suggest GABA-_A receptors are still present on injured neurons at the 48 h timepoint, and the increased 48 h V_T observed here is consistent with earlier rat studies showing early GABA-_A receptor upregulation. That FMZ binding at 48 h was predictive of SNL may have clinical implications.

Bridging Therapy or IV Thrombolysis in Minor Stroke with Large Vessel Occlusion

OBJECTIVE

Whether bridging therapy (intravenous thrombolysis [IVT] followed by endovascular treatment) is superior to IVT alone in minor stroke with large vessel occlusion (LVO) is unknown.

METHODS

Multicentric retrospective observational study including, in intention-to-treat, consecutive IVT-treated minor strokes (National Institutes of Health Stroke Scale [NIHSS] ≤ 5) with LVO, with or without additional mechanical thrombectomy. Propensity-score (inverse probability of treatment weighting) was used to reduce baseline between-groups differences. The primary outcome was excellent outcome, that is, modified Rankin score 0 to 1 at 3 months follow-up.

RESULTS

Overall, 598 patients were included (214 and 384 in the bridging therapy and IVT groups, respectively). Following propensity-score weighting, the distribution of baseline clinical and radiological variables was similar across the two patient groups. Compared with IVT alone, bridging therapy was not associated with excellent outcome (odds ratio [OR] = 0.96; 95% confidence interval [CI] = 0.75-1.24; p = 0.76), but was associated with symptomatic intracranial hemorrhage (OR = 3.01; 95% CI = 1.77-5.11; p < 0.0001). Occlusion site was a strong modifier of the effect of bridging therapy on outcome (p_interaction < 0.0001), with bridging therapy associated with higher odds of excellent outcome in proximal M1 (OR = 3.26; 95% CI = 1.67-6.35; p = 0.0006) and distal M1 (OR = 1.69; 95% CI = 1.01-2.82; p = 0.04) occlusions, but with lower odds of excellent outcome for M2 (OR = 0.53; 95% CI = 0.38-0.75; p = 0.0003) occlusions. Bridging therapy was associated with higher rates of symptomatic intracranial hemorrhage in M2 occlusions only (OR = 4.40; 95% CI = 2.20-8.83; p < 0.0001).

INTERPRETATION

Although overall outcomes were similar in intended bridging therapy as compared to intended IVT alone in minor strokes with LVO, our results suggest that intended bridging therapy may be beneficial in M1 occlusions, whereas the benefit-risk profile may favor IVT alone in M2 occlusions. ANN NEUROL 2020 ANN NEUROL 2020;88:160-169.

A Risk Score Including Carotid Plaque Inflammation and Stenosis Severity Improves Identification of Recurrent Stroke

Background and Purpose—

In randomized trials of symptomatic carotid endarterectomy, only modest benefit occurred in patients with moderate stenosis and important subgroups experienced no benefit. Carotid plaque 18 F-fluorodeoxyglucose uptake on positron emission tomography, reflecting inflammation, independently predicts recurrent stroke. We investigated if a risk score combining stenosis and plaque 18 F-fluorodeoxyglucose would improve the identification of early recurrent stroke.

Methods—

We derived the score in a prospective cohort study of recent (<30 days) non-severe (modified Rankin Scale score ≤3) stroke/transient ischemic attack. We derived the SCAIL (symptomatic carotid atheroma inflammation lumen-stenosis) score (range, 0–5) including 18 F-fluorodeoxyglucose standardized uptake values (SUV max <2 g/mL, 0 points; SUV max 2–2.99 g/mL, 1 point; SUV max 3–3.99 g/mL, 2 points; SUV max ≥4 g/mL, 3 points) and stenosis (<50%, 0 points; 50%–69%, 1 point; ≥70%, 2 points). We validated the score in an independent pooled cohort of 2 studies. In the pooled cohorts, we investigated the SCAIL score to discriminate recurrent stroke after the index stroke/transient ischemic attack, after positron emission tomography-imaging, and in mild or moderate stenosis.

Results—

In the derivation cohort (109 patients), recurrent stroke risk increased with increasing SCAIL score ( P =0.002, C statistic 0.71 [95% CI, 0.56–0.86]). The adjusted (age, sex, smoking, hypertension, diabetes mellitus, antiplatelets, and statins) hazard ratio per 1-point SCAIL increase was 2.4 (95% CI, 1.2–4.5, P =0.01). Findings were confirmed in the validation cohort (87 patients, adjusted hazard ratio, 2.9 [95% CI, 1.9–5], P <0.001; C statistic 0.77 [95% CI, 0.67–0.87]). The SCAIL score independently predicted recurrent stroke after positron emission tomography-imaging (adjusted hazard ratio, 4.52 [95% CI, 1.58–12.93], P =0.005). Compared with stenosis severity (C statistic, 0.63 [95% CI, 0.46–0.80]), prediction of post-positron emission tomography stroke recurrence was improved with the SCAIL score (C statistic, 0.82 [95% CI, 0.66–0.97], P =0.04). Findings were confirmed in mild or moderate stenosis (adjusted hazard ratio, 2.74 [95% CI, 1.39–5.39], P =0.004).

Conclusions—

The SCAIL score improved the identification of early recurrent stroke. Randomized trials are needed to test if a combined stenosis-inflammation strategy improves selection for carotid revascularization where benefit is currently uncertain.

Relationships between brain perfusion and early recanalization after intravenous thrombolysis for acute stroke with large vessel occlusion

In large vessel occlusion (LVO) stroke, it is unclear whether severity of ischemia is involved in early post-thrombolysis recanalization over and above thrombus site and length. Here we assessed the relationships between perfusion parameters and early recanalization following intravenous thrombolysis administration in LVO patients. From a multicenter registry, we identified 218 thrombolysed LVO patients referred for thrombectomy with both (i) pre-thrombolysis MRI, including diffusion-weighted imaging (DWI), T2*-imaging, MR-angiography and dynamic susceptibility-contrast perfusion-weighted imaging (PWI); and (ii) evaluation of recanalization on first angiographic run or non-invasive imaging ≤ 3 h from thrombolysis start. Infarct core volume on DWI, PWI-DWI mismatch volume and hypoperfusion intensity ratio (HIR; defined as Tmax ≥ 10 s volume/ Tmax ≥ 6 s volume, low HIR indicating milder hypoperfusion) were determined using a commercially available software. Early recanalization occurred in 34 (16%) patients, and multivariable analysis was associated with lower HIR (P = 0.006), shorter thrombus on T2*-imaging (P < 0.001) and more distal occlusion (P = 0.006). However, the relationship between HIR and early recanalization was robust only for thrombus length <14 mm. In summary, the present study disclosed an association between lower HIR and early post-thrombolysis recanalization. Early post-thrombolysis recanalization is therefore determined not only by thrombus site and length but also by severity of ischemia.

Recovery and Prediction of Dynamic Precision Grip Force Control After Stroke

Background and Purpose- Dexterous object manipulation, requiring generation and control of finger forces, is often impaired after stroke. This study aimed to describe recovery of precision grip force control after stroke and to determine clinical and imaging predictors of 6-month performance. Methods- Eighty first-ever stroke patients with varying degrees of upper limb weakness were evaluated at 3 weeks, 3 months, and 6 months after stroke. Twenty-three healthy individuals of comparable age were also studied. The Strength-Dexterity test was used to quantify index finger and thumb forces during compression of springs of varying length in a precision grip. The coordination between finger forces (CorrForce), along with Dexterity-score and Repeatability-score, was calculated. Anatomical magnetic resonance imaging was used to calculate weighted corticospinal tract lesion load (wCST-LL). Results- CorrForce, Dexterity-score, and Repeatability-score in the affected hand were dramatically lower at each time point compared with the less-affected hand and the control group, even in patients with mild motor impairment according to Fugl-Meyer assessment. Improved performance over time occurred in CorrForce and Dexterity-score but not in Repeatability-score. The Fugl-Meyer assessment hand subscale, sensory function, and wCST-LL best predicted CorrForce and Dexterity-score status at 6 months (R²=0.56 and 0.87, respectively). wCST-LL explained substantial variance in CorrForce (R²=0.34) and Dexterity-score (R²=0.50) at 6 months; two-point discrimination and Fugl-Meyer score accounted for considerable additional variance. Absence of recovery in CorrForce was predicted by wCST-LL >4 cc and in Dexterity-score by wCST-LL >6 cc. Conclusions- Findings highlight persisting deficits in the ability to grasp and control finger forces after stroke. wCST-LL was the strongest predictor of performance at 6 months, but early two-point discrimination and Fugl-Meyer score had substantial additional predictive value. Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT02878304.

Advancing diagnostic criteria for sporadic cerebral amyloid angiopathy: Study protocol for a multicenter MRI-pathology validation of Boston criteria v2.0

RATIONALE

The Boston criteria are used worldwide for the in vivo diagnosis of cerebral amyloid angiopathy and are the basis for clinical decision-making and research in the field. Given substantial advances in cerebral amyloid angiopathy's clinical aspects and MRI biomarkers, we designed a multicenter study within the International cerebral amyloid angiopathy Association aimed at further validating the diagnostic accuracy of the Boston and potentially improving and updating them.

AIM

We aim to derive and validate an updated "version 2.0" of the Boston criteria across the spectrum of cerebral amyloid angiopathy-related presentations and MRI biomarkers.

SAMPLE SIZE ESTIMATES

Participating centers with suitable available data (see Methods) were identified from existing collaborations and an open invitation to the International Cerebral Amyloid Angiopathy Association emailing list. Our study sample will include: (1) a derivation cohort - Massachusetts General Hospital (MGH), Boston cases from inception to 2012 (∼150 patients); (2) temporal external validation cohort - MGH, Boston cases from 2012 to 2018 (∼100 patients); and (3) geographical external validation cohort - non-Boston cases (∼85 patients).

METHODS AND DESIGN

Multicenter collaborative study. We will collect and analyze data from patients' age ≥ 50 with any potential sporadic cerebral amyloid angiopathy-related clinical presentations (spontaneous intracerebral hemorrhage, transient focal neurological episodes and cognitive impairment), available brain MRI ("index test"), and histopathologic assessment for cerebral amyloid angiopathy ("reference standard" for diagnosis). Trained raters will assess MRI for all prespecified hemorrhagic and non-hemorrhagic small vessel disease markers of interest, according to validated criteria and a prespecified protocol, masked to clinical and histopathologic features. Brain tissue samples will be rated for cerebral amyloid angiopathy, defined as Vonsattel grade ≥2 for whole brain autopsies and ≥1 for cortical biopsies or hematoma evacuation. Based on our estimated available sample size, we will undertake pre-specified cohort splitting as above. We will: (a) pre-specify variables and statistical cut-offs; (b) examine univariable and multivariable associations; and (c) then assess classification measures (sensitivity, specificity etc.) for each MRI biomarker individually, in relation to the cerebral amyloid angiopathy diagnosis reference standard on neuropathology in a derivation cohort. The MRI biomarkers strongly associated with cerebral amyloid angiopathy diagnosis will be selected for inclusion in provisional (probable and possible cerebral amyloid angiopathy) Boston criteria v2.0 and validated using appropriate metrics and models.

STUDY OUTCOMES

Boston criteria v2.0 for clinical cerebral amyloid angiopathy diagnosis.

DISCUSSION

This work aims to potentially update and improve the diagnostic test accuracy of the Boston criteria for cerebral amyloid angiopathy and to provide wider validation of the criteria in a large sample. We envision that this work will meet the needs of clinicians and investigators and help accelerate progress towards better treatment of cerebral amyloid angiopathy.

Comparison of classification methods for tissue outcome after ischaemic stroke

In acute ischaemic stroke, identifying brain tissue at high risk of infarction is important for clinical decision-making. This tissue may be identified with suitable classification methods from magnetic resonance imaging data. The aim of the present study was to assess and compare the performance of five popular classification methods (adaptive boosting, logistic regression, artificial neural networks, random forest and support vector machine) in identifying tissue at high risk of infarction on human voxel-based brain imaging data. The classification methods were used with eight MRI parameters, including diffusion-weighted imaging and perfusion-weighted imaging obtained in 55 patients. The five criteria used to assess the performance of the methods were the area under the receiver operating curve (AUC_roc ), the area under the precision-recall curve (AUC_pr ), sensitivity, specificity and the Dice coefficient. The methods performed equally in terms of sensitivity and specificity, while the results of AUC_roc and the Dice coefficient were significantly better for adaptive boosting, logistic regression, artificial neural networks and random forest. However, there was no statistically significant difference between the performances of these five classification methods regarding AUC_pr , which was the main comparison metric. Machine learning methods can provide valuable prognostic information using multimodal imaging data in acute ischaemic stroke, which in turn can assist in developing personalized treatment decision for clinicians after a thorough validation of methods with an independent data set.

Protecting the ischaemic penumbra as an adjunct to thrombectomy for acute stroke

After ischaemic stroke, brain damage can be curtailed by rescuing the 'ischaemic penumbra' - that is, the severely hypoperfused, at-risk but not yet infarcted tissue. Current evidence-based treatments involve restoration of blood flow so as to salvage the penumbra before it evolves into irreversibly damaged tissue, termed the 'core'. Intravenous thrombolysis (IVT) can salvage the penumbra if given within 4.5 h after stroke onset; however, the early recanalization rate is only ~30%. Direct removal of the occluding clot by mechanical thrombectomy considerably improves outcomes over IVT alone, but despite early recanalization in > 80% of cases, ~50% of patients who receive this treatment do not enjoy functional independence, usually because the core is already too large at the time of recanalization. Novel therapies aiming to 'freeze' the penumbra - that is, prevent core growth until recanalization is complete - hold potential as adjuncts to mechanical thrombectomy. This Review focuses on nonpharmacological approaches that aim to restore the physiological balance between oxygen delivery to and oxygen demand of the penumbra. Particular emphasis is placed on normobaric oxygen therapy, hypothermia and sensory stimulation. Preclinical evidence and early pilot clinical trials are critically reviewed, and future directions, including clinical translation and trial design issues, are discussed.

Quantitative Assessment of Hand Spasticity After Stroke: Imaging Correlates and Impact on Motor Recovery

Objective: This longitudinal observational study investigated how neural stretch-resistance in wrist and finger flexors develops after stroke and relates to motor recovery, secondary complications, and lesion location.

Methods: Sixty-one patients were assessed at 3 weeks (T1), three (T2), and 6 months (T3) after stroke using the NeuroFlexor method and clinical tests. Magnetic Resonance Imaging was used to calculate weighted corticospinal tract lesion load (wCST-LL) and to perform voxel-based lesion symptom mapping.

Results: NeuroFlexor assessment demonstrated spasticity (neural component [NC] >3.4N normative cut-off) in 33% of patients at T1 and in 51% at T3. Four subgroups were identified: early Severe spasticity (n = 10), early Moderate spasticity (n = 10), Late developing spasticity (n = 17) and No spasticity (n = 24). All except the Severe spasticity group improved significantly in Fugl-Meyer Assessment (FMA-HAND) to T3. The Severe and Late spasticity groups did not improve in Box and Blocks Test. The Severe spasticity group showed a 25° reduction in passive range of movement and more frequent arm pain at T3. wCST-LL correlated positively with NC at T1 and T3, even after controlling for FMA-HAND and lesion volume. Voxel-based lesion symptom mapping showed that lesioned white matter below cortical hand knob correlated positively with NC.

Conclusion: Severe hand spasticity early after stroke is negatively associated with hand motor recovery and positively associated with the development of secondary complications. Corticospinal tract damage predicts development of spasticity. Early quantitative hand spasticity measurement may have potential to predict motor recovery and could guide targeted rehabilitation interventions after stroke.