The resistance to ischemia of white and gray matter after stroke

Outcomes of mechanical thrombectomy in stroke patients with extreme large infarction core

BACKGROUND

Recent clinical trials have demonstrated that patients with large vessel occlusion (LVO) and large infarction core may still benefit from mechanical thrombectomy (MT). In this study, we evaluate outcomes of MT in LVO patients presenting with extremely large infarction core Alberta Stroke Program Early CT Score (ASPECTS 0-2).

METHODS

Data from the Stroke Thrombectomy and Aneurysm Registry (STAR) was interrogated. We identified thrombectomy patients presenting with an occlusion in the intracranial internal carotid artery (ICA) or M1 segment of the middle cerebral artery and extremely large infarction core (ASPECTS 0-2). A favorable outcome was defined by achieving a modified Rankin scale of 0-3 at 90 days post-MT. Successful recanalization was defined by achieving a modified Thrombolysis In Cerebral Ischemia (mTICI) score ≥2B.

RESULTS

We identified 58 patients who presented with ASPECTS 0-2 and underwent MT. Median age was 74.0 (66.3-80.0) years, 30 (51.7%) were females, and 16 (27.6%) patients received intravenous tissue plasminogen activator. There was no difference regarding the location of the occlusion (p=0.57). Aspiration thrombectomy was performed in 34 (64.2%) patients and stent retriever was used in 8 (15.1%) patients. In patients presenting with ASPECTS 0-2 the mortality rate was 41.4%, 31% had mRS 0-3 at day 90, 66.67% ≥70 years of age had mRS of 5-6 at day 90. On multivariable analysis, age, National Institutes of Health Stroke Scale on admission, and successful recanalization (mTICI ≥2B) were independently associated with favorable outcomes.

CONCLUSIONS

This multicentered, retrospective cohort study suggests that MT may be beneficial in a select group of patients with ASPECTS 0-2.

Reducing False-Positives in CT Perfusion Infarct Core Segmentation Using Contralateral Local Normalization

BACKGROUND AND PURPOSE

The established global threshold of rCBF <30% for infarct core segmentation can lead to false-positives, as it does not account for the differences in blood flow between GM and WM and patient-individual factors, such as microangiopathy. To mitigate this problem, we suggest normalizing each voxel not only with a global reference value (ie, the median value of normally perfused tissue) but also with its local contralateral counterpart.

MATERIALS AND METHODS

We retrospectively enrolled 2830 CTP scans with suspected ischemic stroke, of which 335 showed obvious signs of microangiopathy. In addition to the conventional, global normalization, a local normalization was performed by dividing the rCBF maps with their mirrored and smoothed counterpart, which sets each voxel value in relation to the contralateral counterpart, intrinsically accounting for GM and WM differences and symmetric patient individual microangiopathy. Maps were visually assessed and core volumes were calculated for both methods.

RESULTS

Cases with obvious microangiopathy showed a strong reduction in false-positives by using local normalization (mean 14.7 mL versus mean 3.7 mL in cases with and without microangiopathy). On average, core volumes were slightly smaller, indicating an improved segmentation that was more robust against naturally low blood flow values in the deep WM.

CONCLUSIONS

The proposed method of local normalization can reduce overestimation of the infarct core, especially in the deep WM and in cases with obvious microangiopathy. False-positives in CTP infarct core segmentation might lead to less-than-optimal therapy decisions when not correctly interpreted. The proposed method might help mitigate this problem.

Infarct Evolution on MR-DWI After Thrombectomy in Acute Stroke Patients Randomized to Nerinetide or Placebo: The REPERFUSE-NA1 Study

BACKGROUND AND OBJECTIVES

The neuroprotectant nerinetide has shown promise in reducing infarct volumes in primate models of ischemia reperfusion. We hypothesized that early secondary infarct growth after endovascular therapy (EVT) (1) may be a suitable surrogate biomarker for testing neuroprotective compounds, (2) is feasible to assess in the acute setting using sequential MRI, and (3) can be modified by treatment with nerinetide.

METHODS

REPERFUSE-NA1 was a prospective, multisite MRI substudy of the randomized controlled trial ESCAPE-NA1 (ClinicalTrials.gov NCT02930018) that involved patients with acute disabling large vessel occlusive stroke undergoing EVT within 12 hours of onset who were randomized to receive intravenous nerinetide or placebo. Patients enrolled in REPERFUSE-NA1 underwent sequential MRI <5 hours post-EVT (day 1) and at 24 hours (day 2). The primary outcome was total diffusion-weighted MRI infarct growth early after EVT, defined as the lesion volume difference between day 2 and day 1. The secondary outcome was region-specific infarct growth in different brain tissue compartments. Statistical analyses were performed using the Mann-Whitney U test and multiple linear regression.

RESULTS

Sixty-seven of 71 patients included had MRI of sufficient quality. The median infarct volume post-EVT was 12.98 mL (IQR, 5.93-28.08) in the nerinetide group and 10.80 mL (IQR, 3.11-24.45) in the control group (p = 0.59). Patients receiving nerinetide showed a median early secondary infarct growth of 5.92 mL (IQR, 1.09-21.30) compared with 10.80 mL (interquartile range [IQR], 2.54-21.81) in patients with placebo (p = 0.30). Intravenous alteplase modified the effect of nerinetide on region-specific infarct growth in white matter and basal ganglia compartments. In patients with no alteplase, the infarct growth rate was reduced by 120% (standard error [SE], 60%) in the white matter (p = 0.03) and by 340% (SE, 140%) in the basal ganglia (p = 0.02) in the nerinetide group compared with placebo after adjusting for confounders.

DISCUSSION

This study highlights the potential of using MR imaging as a biomarker to estimate the effect of a neuroprotective agent in acute stroke treatment. Patients with acute large vessel occlusive stroke exhibited appreciable early infarct growth both in the gray matter and the white matter after undergoing EVT. Acknowledging relatively small overall infarct volumes in this study, treatment with nerinetide was associated with slightly reduced percentage infarct growth in the white matter and basal ganglia compared with placebo in patients not receiving intravenous alteplase and had no effect on the total early secondary infarct growth.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov NCT02930018.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that for patients with acute large vessel ischemic stroke undergoing EVT, nerinetide did not significantly decrease early post-EVT infarct growth compared with placebo.

Clipping of Unruptured Anterior Choroidal Artery Aneurysms Together with Small Branches: Safety Confirmation Using Intraoperative Indocyanine Green Video-Angiography and Intraoperative Neurophysiological Monitoring

BACKGROUND

In treating anterior choroidal artery (AChA) aneurysms, preserving the AChA main trunk is of course necessary to prevent postoperative ischemic complications. However, in practice, complete occlusions are often limited by small branches.

OBJECTIVE

We aimed to demonstrate that even in cases where complete occlusion of the AChA aneurysm is complex due to small branches, complete occlusion can be safely achieved using indocyanine green video-angiography and intraoperative neurophysiological monitoring (IONM).

METHODS

We performed a retrospective review of all unruptured AChA aneurysms surgically treated at our institution from 2012 to 2021. All available surgical videos were reviewed to find AChA aneurysms clipped with small branches; clinical and radiological data were collected for these cases.

RESULTS

Among 391 cases of unruptured AChA aneurysms treated surgically, 25 AChA aneurysms were clipped with small branches. AChA-related ischemic complications occurred in 2 cases (8%) without retrograde indocyanine green filling to the branches. These 2 cases had changes in IONM. There were no ischemic complications in the remaining cases with retrograde indocyanine green filling to the branches and no change in IONM. During an average follow-up of 47 months (12-111 months), a small residual neck was observed in 3 cases (12%) and recurrence or progression of the aneurysm was observed in only 1 case (4%).

CONCLUSIONS

The surgical treatment of AChA aneurysms carries the risk of devastating ischemic complications. Even in cases where complete clip ligation seems impossible due to small branches associated with AChA aneurysms, complete occlusion can be safely achieved using indocyanine green video-angiography and IONM.

Ghost infarct core: A systematic review of the frequency, magnitude, and variables of CT perfusion overestimation

BACKGROUND AND PURPOSE

CT perfusion (CTP) imaging is now widely used to select patients with large vessel occlusions for mechanical thrombectomy. Ghost infarct core (GIC) phenomenon has been coined to describe CTP core overestimation and has been investigated in several retrospective studies. Our aim is to review the frequency, magnitude, and variables associated with this phenomenon.

METHODS

A primary literature search resulted in eight studies documenting median time from symptom onset to CTP, median estimated core size, median final infarct volume, median core overestimation of the GIC population, recanalization rates, good outcomes, and collateral status for this systematic review.

RESULTS

All the studies investigated patients who underwent CTP within 6 hours of symptom onset, ranging from median times of 105 to 309 minutes. The frequency of core overestimation varied from 6% to 58.4%, while the median estimated ischemic core and final infarction volume ranged from 7 to 27 mL and 12 to 31 mL, respectively. The median core overestimation ranged from 3.6 to 30 mL with upper quartile ranges up to 58 mL. GIC was found to be a highly time-and-collateral-dependent process that increases in frequency and magnitude as the time from symptom onset to imaging decreases and in the presence of poor collaterals.

CONCLUSIONS

CTP ischemic core overestimation appears to be a relatively common phenomenon that is most frequent in patients with poor collaterals imaged within the acute time window. Early perfusion imaging should be interpreted with caution to prevent the inadvertent exclusion of patients from highly effective reperfusion therapies.

Neurological Functional Independence After Endovascular Thrombectomy and Different Imaging Modalities for Large Infarct Core Assessment : A Systematic Review and Meta-analysis

PURPOSE

To investigate the rate of neurological functional independence (NFI) at 90 days in patients with large infarct core (LIC), which was evaluated by different imaging modalities before endovascular thrombectomy (EVT).

METHODS

PubMed and EMBASE were searched for original studies on clinical functional outcomes at 90 days in LIC patients who received EVT treatment from inception to 28 September 2021. The pooled NFI rates were calculated using random effects model according to different imaging modalities and criteria.

RESULTS

We included 34 studies enrolling 2997 LIC patients. The NFI rates were 23% (95% confidence interval, CI 15-32%) and 24% (95% CI 10-38%) when LIC was defined as core volume ≥50 ml and ≥ 70 ml separately on computed tomography perfusion, 36% (95% CI 23-48%) and 21% (95% CI 17-25%) when LIC was defined as core volume ≥ 50 ml and ≥ 70 ml separately on magnetic resonance diffusion-weighted imaging (DWI), 28% (95% CI 24-32%) and 37% (95% CI 21-53%) when LIC was defined as DWI-ASPECTS ≤ 5 and ≤ 6 separately, 23% (95% CI 19-27%) and 32% (95% CI 18-46%) when LIC was defined as NCCT-ASPECTS ≤ 5 and ≤ 6 separately.

CONCLUSION

Similar NFI rates could be obtained after EVT in LIC patients if proper LIC criteria were select according to the imaging modality.

The Significance of Lipids for the Absorption and Release of Oxygen in Biological Organisms

A critically important step for the uptake and transport of oxygen (O2) in living organisms is the crossing of the phase boundary between gas (or water) and lipid/proteins in the cell. Classically, this transport across the phase boundary is explained as a transport by proteins or protein-based structures. In our contribution here, we want to show the significance of passive transport of O2 also (and in some cases probably predominantly) through lipids in many if not all aerobic organisms. In plants, the significance of lipids for gas exchange (absorption of CO2 and release of O2) is well recognized. The leaves of plants have a cuticle layer as the last film on both sides formed by polyesters and lipids. In animals, the skin has sebum as its last layer consisting of a mixture of neutral fatty esters, cholesterol and waxes which are also at the border between the cells of the body and the air. The last cellular layers of skin are not vascularized therefore their metabolism totally depends on this extravasal O2 absorption, which cannot be replenished by the bloodstream. The human body absorbs about 0.5% of O2 through the skin. In the brain, myelin, surrounding nerve cell axons and being formed by oligodendrocytes, is most probably also responsible for enabling O2 transport from the extracellular space to the cells (neurons). Myelin, being not vascularized and consisting of water, lipids and proteins, seems to absorb O2 in order to transport it to the nerve cell axon as well as to perform extramitochondrial oxidative phosphorylation inside the myelin structure around the axons (i.e., myelin synthesizes ATP) - similarly to the metabolic process occurring in concentric multilamellar structures of cyanobacteria. Another example is the gas transport in the lung where lipids play a crucial role in the surfactant ensuring incorporation of O2 in the alveoli where there are lamellar body and tubular myelin which form multilayered surface films at the air-membrane border of the alveolus. According to our view, the role played by lipids in the physical absorption of gases appears to be crucial to the existence of many, if not all, of the living aerobic species.

Accuracy of CT Perfusion-Based Core Estimation of Follow-up Infarction: Effects of Time Since Last Known Well

BACKGROUND AND OBJECTIVES

To assess the accuracy of baseline CT perfusion (CTP) ischemic core estimates.

METHODS

From SELECT (Optimizing Patient Selection for Endovascular Treatment in Acute Ischemic Stroke), a prospective multicenter cohort study of imaging selection, patients undergoing endovascular thrombectomy who achieved complete reperfusion (modified Thrombolysis In Cerebral Ischemia score 3) and had follow-up diffusion-weighted imaging (DWI) available were evaluated. Follow-up DWI lesions were coregistered to baseline CTP. The difference between baseline CTP core (relative cerebral blood flow [rCBF] <30%) volume and follow-up infarct volume was classified as overestimation (core ≥10 mL larger than infarct), adequate, or underestimation (core ≥25 mL smaller than infarct) and spatial overlap was evaluated.

RESULTS

Of 101 included patients, median time from last known well (LKW) to imaging acquisition was 138 (82-244) minutes. The median baseline ischemic core estimate was 9 (0-31.9) mL and median follow-up infarct volume was 18.4 (5.3-68.7) mL. All 6/101 (6%) patients with overestimation of the subsequent infarct volume were imaged within 90 minutes of LKW and achieved rapid reperfusion (within 120 minutes of CTP). Using rCBF <20% threshold to estimate ischemic core in patients presenting within 90 minutes eliminated overestimation. Volumetric correlation between the ischemic core estimate and follow-up imaging improved as LKW time to imaging acquisition increased: Spearman ρ <90 minutes 0.33 (p = 0.049), 90-270 minutes 0.63 (p < 0.0001), >270 minutes 0.86 (p < 0.0001). Assessment of the spatial overlap between baseline CTP ischemic core lesion and follow-up infarct demonstrated that a median of 3.2 (0.0-9.0) mL of estimated core fell outside the subsequent infarct. These regions were predominantly in white matter.

DISCUSSION

Significant overestimation of irreversibly injured ischemic core volume was rare, was only observed in patients who presented within 90 minutes of LKW and achieved reperfusion within 120 minutes of CTP acquisition, and occurred primarily in white matter. Use of a more conservative (rCBF <20%) threshold for estimating ischemic core in patients presenting within 90 minutes eliminated all significant overestimation cases.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov: NCT03876457.

Comparison of Large Animal Models for Acute Ischemic Stroke: Which Model to Use?

Translation of acute ischemic stroke research to the clinical setting remains limited over the last few decades with only one drug, recombinant tissue-type plasminogen activator, successfully completing the path from experimental study to clinical practice. To improve the selection of experimental treatments before testing in clinical studies, the use of large gyrencephalic animal models of acute ischemic stroke has been recommended. Currently, these models include, among others, dogs, swine, sheep, and nonhuman primates that closely emulate aspects of the human setting of brain ischemia and reperfusion. Species-specific characteristics, such as the cerebrovascular architecture or pathophysiology of thrombotic/ischemic processes, significantly influence the suitability of a model to address specific research questions. In this article, we review key characteristics of the main large animal models used in translational studies of acute ischemic stroke, regarding (1) anatomy and physiology of the cerebral vasculature, including brain morphology, coagulation characteristics, and immune function; (2) ischemic stroke modeling, including vessel occlusion approaches, reproducibility of infarct size, procedural complications, and functional outcome assessment; and (3) implementation aspects, including ethics, logistics, and costs. This review specifically aims to facilitate the selection of the appropriate large animal model for studies on acute ischemic stroke, based on specific research questions and large animal model characteristics.

Imaging Acute Stroke: From One-Size-Fit-All to Biomarkers

In acute stroke management, time window has been rigidly used as a guide for decades and the reperfusion treatment is only available in the first few limited hours. Recently, imaging-based selection of patients has successfully expanded the treatment window out to 16 and even 24 h in the DEFUSE 3 and DAWN trials, respectively. Recent guidelines recommend the use of imaging techniques to guide therapeutic decision-making and expanded eligibility in acute ischemic stroke. A tissue window is proposed to replace the time window and serve as the surrogate marker for potentially salvageable tissue. This article reviews the evolution of time window, addresses the advantage of a tissue window in precision medicine for ischemic stroke, and discusses both the established and emerging techniques of neuroimaging and their roles in defining a tissue window. We also emphasize the metabolic imaging and molecular imaging of brain pathophysiology, and highlight its potential in patient selection and treatment response prediction in ischemic stroke.

Efficient extra-mitochondrial aerobic ATP synthesis in neuronal membrane systems

The nervous system displays high energy consumption, apparently not fulfilled by mitochondria, which are underrepresented therein. The oxidative phosphorylation (OxPhos) activity, a mitochondrial process that aerobically provides ATP, has also been reported also in the myelin sheath and the rod outer segment (OS) disks. Thus, commonalities and differences between the extra-mitochondrial and mitochondrial aerobic metabolism were evaluated in bovine isolated myelin (IM), rod OS, and mitochondria-enriched fractions (MIT). The subcellular fraction quality and the absence of contamination fractions have been estimated by western blot analysis. Oxygen consumption and ATP synthesis were stimulated by conventional (pyruvate + malate or succinate) and unconventional (NADH) substrates, observing that oxygen consumption and ATP synthesis by IM and rod OS are more efficient than by MIT, in the presence of both kinds of respiratory substrates. Mitochondria did not utilize NADH as a respiring substrate. When ATP synthesis by either sample was assayed in the presence of 10-100 µM ATP in the assay medium, only in IM and OS it was not inhibited, suggesting that the ATP exportation by the mitochondria is limited by extravesicular ATP concentration. Interestingly, IM and OS but not mitochondria appear able to synthesize ATP at a later time with respect to exposure to respiratory substrates, supporting the hypothesis that the proton gradient produced by the electron transport chain is buffered by membrane phospholipids. The putative transfer mode of the OxPhos molecular machinery from mitochondria to the extra-mitochondrial structures is also discussed, opening new perspectives in the field of neurophysiology.

Early Thrombectomy Protects the Internal Capsule in Patients With Proximal Middle Cerebral Artery Occlusion

BACKGROUND AND PURPOSE

Proximal middle cerebral artery (MCA) occlusions impede blood flow to the noncollateralized lenticulostriate artery territory. Previous work has shown that this almost inevitably leads to infarction of the dependent gray matter territories in the striate even if perfusion is restored by mechanical thrombectomy. Purpose of this analysis was to evaluate potential sparing of neighboring fiber tracts, ie, the internal capsule.

METHODS

An observational single-center study of patients with proximal MCA occlusions treated with mechanical thrombectomy and receiving postinterventional high-resolution diffusion-weighted imaging was conducted. Patients were classified according to internal capsule ischemia (IC+ versus IC-) at the postero-superior level of the MCA lenticulostriate artery territory (corticospinal tract correlate). Associations of IC+ versus IC- with baseline variables as well as its clinical impact were evaluated using multivariable logistic or linear regression analyses adjusting for potential confounders.

RESULTS

Of 92 included patients with proximal MCA territory infarctions, 45 (48.9%) had an IC+ pattern. Longer time from symptom-onset to groin-puncture (adjusted odds ratio, 2.12 [95% CI, 1.19-3.76] per hour), female sex and more severe strokes were associated with IC+. Patients with IC+ had lower rates of substantial neurological improvement and functional independence (adjusted odds ratio, 0.26 [95% CI, 0.09-0.81] and adjusted odds ratio, 0.25 [95% CI, 0.07-0.86]) after adjustment for confounders. These associations remained unchanged when confining analyses to patients without ischemia in the corona radiata or the motor cortex and here, IC+ was associated with higher National Institutes of Health Stroke Scale motor item scores (β, +2.8 [95% CI, 1.5 to 4.1]) without a significant increase in nonmotor items (β, +0.8 [95% CI, -0.2 to 1.9).

CONCLUSIONS

Rapid mechanical thrombectomy with successful reperfusion of the lenticulostriate arteries often protects the internal capsule from subsequent ischemia despite early basal ganglia damage. Salvage of this eloquent white matter tract within the MCA lenticulostriate artery territory seems strongly time-dependent, which has clinical and pathophysiological implications.

Preclinical Stroke Research and Translational Failure: A Bird's Eye View on Preventable Variables

Despite achieving remarkable success in understanding the cellular, molecular and pathophysiological aspects of stroke, translation from preclinical research has always remained an area of debate. Although thousands of experimental compounds have been reported to be neuro-protective, their failures in clinical setting have left the researchers and stakeholders in doldrums. Though the failures described have been excruciating, they also give us a chance to refocus on the shortcomings. For better translational value, evidences from preclinical studies should be robust and reliable. Preclinical study design has a plethora of variables affecting the study outcome. Hence, this review focusses on the factors to be considered for a well-planned preclinical study while adhering to guidelines with emphasis on the study design, commonly used animal models, their limitations with special attention on various preventable attritions including comorbidities, aged animals, time of dosing, outcome measures and physiological variables along with the concept of multicentric preclinical randomized controlled trials. Here, we provide an overview of a panorama of practical aspects, which could be implemented, so that a well-defined preclinical study would result in a neuro-protectant with better translational value.

Intracisternal administration of tanshinone IIA-loaded nanoparticles leads to reduced tissue injury and functional deficits in a porcine model of ischemic stroke

Background

The absolute number of new stroke patients is annually increasing and there still remains only a few Food and Drug Administration (FDA) approved treatments with significant limitations available to patients. Tanshinone IIA (Tan IIA) is a promising potential therapeutic for ischemic stroke that has shown success in pre-clinical rodent studies but lead to inconsistent efficacy results in human patients. The physical properties of Tan-IIA, including short half-life and low solubility, suggests that Poly (lactic-co-glycolic acid) (PLGA) nanoparticle-assisted delivery may lead to improve bioavailability and therapeutic efficacy. The objective of this study was to develop Tan IIA-loaded nanoparticles (Tan IIA-NPs) and to evaluate their therapeutic effects on cerebral pathological changes and consequent motor function deficits in a pig ischemic stroke model.

Results

Tan IIA-NP treated neural stem cells showed a reduction in SOD activity in in vitro assays demonstrating antioxidative effects. Ischemic stroke pigs treated with Tan IIA-NPs showed reduced hemispheric swelling when compared to vehicle only treated pigs (7.85 ± 1.41 vs. 16.83 ± 0.62%), consequent midline shift (MLS) (1.72 ± 0.07 vs. 2.91 ± 0.36 mm), and ischemic lesion volumes (9.54 ± 5.06 vs. 12.01 ± 0.17 cm³) when compared to vehicle-only treated pigs. Treatment also lead to lower reductions in diffusivity (-37.30 ± 3.67 vs. -46.33 ± 0.73%) and white matter integrity (-19.66 ± 5.58 vs. -30.11 ± 1.19%) as well as reduced hemorrhage (0.85 ± 0.15 vs 2.91 ± 0.84 cm³) 24 h post-ischemic stroke. In addition, Tan IIA-NPs led to a reduced percentage of circulating band neutrophils at 12 (7.75 ± 1.93 vs. 14.00 ± 1.73%) and 24 (4.25 ± 0.48 vs 5.75 ± 0.85%) hours post-stroke suggesting a mitigated inflammatory response. Moreover, spatiotemporal gait deficits including cadence, cycle time, step time, swing percent of cycle, stride length, and changes in relative mean pressure were less severe post-stroke in Tan IIA-NP treated pigs relative to control pigs.

Conclusion

The findings of this proof of concept study strongly suggest that administration of Tan IIA-NPs in the acute phase post-stroke mitigates neural injury likely through limiting free radical formation, thus leading to less severe gait deficits in a translational pig ischemic stroke model. With stroke as one of the leading causes of functional disability in the United States, and gait deficits being a major component, these promising results suggest that acute Tan IIA-NP administration may improve functional outcomes and the quality of life of many future stroke patients.

White Matter Acute Infarct Volume After Thrombectomy for Anterior Circulation Large Vessel Occlusion Stroke is Associated with Long Term Outcomes

OBJECTIVES

Despite the proven efficacy of endovascular thrombectomy (EVT) for large vessel occlusion stroke, over half treated remain functionally disabled or die. Infarct topography may have implications for prognostication, patient selection, and the development of tissue-specific neuroprotective agents. We sought to quantify white matter injury in anterior circulation acute infarcts post-EVT to understand its significance and identify its determinants.

MATERIALS AND METHODS

Demographics, history, presentations, and outcomes for consecutive patients treated with EVT were recorded in a prospectively maintained database at a single center. Acute infarct masks were coregistered to standard space. Standard atlases of white matter, cortex, and basal ganglia were used to determine region-specific infarct volumes.

RESULTS

167 individuals were identified with median age 69 years and 53% women. 85% achieved adequate reperfusion (TICI 2b-3) after EVT; 43% achieved 90-day functional independence (mRS 0-2). Median infarct volumes were 45cc (IQR 18-122) for total, 17cc (6-49) for white matter, 21cc (4-53) for cortex, and 5cc (1-8) for basal ganglia. The odds of 90-day mRS 0-2 were reduced in patients with larger white matter infarct volume (cc, OR=0.89, 95%CI=0.81-0.96), independent of cortex infarct volume, basal ganglia infarct volume, age, NIHSS, and TICI 2b-3 reperfusion. Reperfusion-to-MRI time was associated with white matter infarct volume (hr, β=0.119, p=0.017), but not cortical or basal ganglia infarct volume.

CONCLUSIONS

These data quantitatively describe region-specific infarct volumes after EVT and suggest the clinical relevance of white matter infarct volume as a predictor of long-term outcomes. Further study is warranted to examine delayed white matter infarction and the significance of specific white matter tracts.

Lower cardiac output is associated with neurodegeneration among older adults with normal cognition but not mild cognitive impairment

Subclinical cardiac dysfunction is associated with smaller total brain volume on magnetic resonance imaging (MRI). To study whether cardiac output relates to regional measurements of grey and white matter structure, older adults (n = 326) underwent echocardiogram to quantify cardiac output (L/min) and brain MRI. Linear regressions related cardiac output to grey matter volumes measured on T₁ and white matter hyperintensities assessed on T₂-FLAIR. Voxelwise analyses related cardiac output to diffusion tensor imaging adjusting for demographic, genetic, and vascular risk factors. Follow-up models assessed a cardiac output x diagnosis interaction with stratification (normal cognition, mild cognitive impairment). Cardiac output interacted with diagnosis, such that lower cardiac output related to smaller total grey matter (p = 0.01), frontal lobe (p = 0.01), and occipital lobe volumes (p = 0.01) among participants with normal cognition. When excluding participants with cardiovascular disease and atrial fibrillation, associations emerged with smaller parietal lobe (p = 0.005) and hippocampal volume (p = 0.05). Subtle age-related cardiac changes may disrupt neuronal homeostasis and impact grey matter integrity prior to cognitive impairment.

Cavitation of symptomatic acute single small subcortical infarctions

BACKGROUND AND PURPOSE

To investigate cavitation of symptomatic acute single small subcortical infarctions (SSSI).

METHODS

Acute SSSI were diagnosed with magnetic resonance (MR) diffusion-weighted imaging (DWI) combined with apparent diffusion coefficient (ADC) sequence on follow-up MR imaging. Cavitation of the acute SSSI was comprehensively viewed on FLAIR, T2-, and T1-weighted sequences.

RESULTS

We enrolled 123 patients with acute SSSI. The follow-up median interval was 303 (125-390) days. The lesions of SSSI evolved into cavitation in 93 patients (75.6%), evolved into WMHs in nine patients (7.3%), and were no visible in 21 patients (17.1%). Cavitation was independently associated with larger infarct diameter on baseline DWI [odds ratio (OR), 1.250, 95% CI (1.078-1.451), P = 0.003], higher score of baseline old lacunar infarct [OR 3.44, 95% CI (1.49-7.91), P = 0.004], and lower rate of dyslipidemia [OR 0.30, 95% CI (0.10-0.76), P = 0.013].

CONCLUSION

Cavitation occurred more in the setting of small vessel diseased brain and less in the SSSI of possible atherosclerotic etiology. This suggested that the etiology of infarct was associated with cavitation after acute SSSI.

Mechanical Thrombectomy in Ischemic Stroke Patients With Alberta Stroke Program Early Computed Tomography Score 0-5

Supplemental Digital Content is available in the text.

Background and Purpose—

If anterior circulation large vessel occlusion acute ischemic stroke patients presenting with ASPECTS 0–5 (Alberta Stroke Program Early CT Score) should be treated with mechanical thrombectomy remains unclear. Purpose of this study was to report on the outcome of patients with ASPECTS 0–5 treated with mechanical thrombectomy and to provide data regarding the effect of successful reperfusion on clinical outcomes and safety measures in these patients.

Methods—

Multicenter, pooled analysis of 7 institutional prospective registries: Bernese-European Registry for Ischemic Stroke Patients Treated Outside Current Guidelines With Neurothrombectomy Devices Using the SOLITAIRE FR With the Intention for Thrombectomy (Clinical Trial Registration—URL: https://www.clinicaltrials.gov. Unique identifier: NCT03496064). Primary outcome was defined as modified Rankin Scale 0–3 at day 90 (favorable outcome). Secondary outcomes included rates of day 90 modified Rankin Scale 0–2 (functional independence), day 90 mortality and occurrence of symptomatic intracerebral hemorrhage. Multivariable logistic regression analyses were performed to assess the association of successful reperfusion with clinical outcomes. Outputs are displayed as adjusted Odds Ratios (aOR) and 95% CI.

Results—

Two hundred thirty-seven of 2046 patients included in this registry presented with anterior circulation large vessel occlusion and ASPECTS 0–5. In this subgroup, the overall rates of favorable outcome and mortality at day 90 were 40.1% and 40.9%. Achieving successful reperfusion was independently associated with favorable outcome (aOR, 5.534; 95% CI, 2.363–12.961), functional independence (aOR, 5.583; 95% CI, 1.964–15.873), reduced mortality (aOR, 0.180; 95% CI, 0.083–0.390), and lower rates of symptomatic intracerebral hemorrhage (aOR, 0.235; 95% CI, 0.062–0.887). The mortality-reducing effect remained in patients with ASPECTS 0–4 (aOR, 0.167; 95% CI, 0.056–0.499). Sensitivity analyses did not change the primary results.

Conclusions—

In patients presenting with ASPECTS 0–5, who were treated with mechanical thrombectomy, successful reperfusion was beneficial without increasing the risk of symptomatic intracerebral hemorrhage. Although the results do not allow for general treatment recommendations, formal testing of mechanical thrombectomy versus best medical treatment in these patients in a randomized controlled trial is warranted.

Brain-Specific Serum Biomarkers Predict Neurological Morbidity in Diagnostically Diverse Pediatric Intensive Care Unit Patients

BACKGROUND

Unexpected neurological morbidity in Pediatric Intensive Care Units (PICUs) remains high and is difficult to detect proactively. Brain-specific biomarkers represent a novel approach for early detection of neurological injury. We sought to determine whether serum concentrations of neuron-specific enolase (NSE), myelin basic protein (MBP), and S100B, specific for neurons, oligodendrocytes, and glia, respectively, were predictive of neurological morbidity in critically ill children.

METHODS

Serum was prospectively collected on days 1-7 from diagnostically diverse PICU patients (n = 103). Unfavorable neurological outcome at hospital discharge was defined as Pediatric Cerebral Performance Category (PCPC) score of 3-6 with a deterioration from baseline. NSE, MBP, and S100B concentrations were measured by enzyme-linked immunosorbent assay.

RESULTS

Peak biomarker levels were greater in patients with unfavorable versus favorable neurological outcome [NSE 39.4 ± 44.1 vs. 12.2 ± 22.9 ng/ml (P = 0.005), MBP 9.1 ± 11.5 vs. 0.6 ± 1.3 ng/ml (P = 0.003), S100B 130 ± 232 vs. 34 ± 70 pg/ml (P = 0.04), respectively; mean ± SD]. Peak levels were each independently associated with unfavorable neurological outcome when controlling for presence of primary neurologic admission diagnosis and poor baseline PCPC using logistic regression analysis (NSE, P = 0.04; MBP, P = 0.004; S100B, P = 0.04), and had the following receiver operating characteristics: NSE 0.75 (0.58, 0.92), MBP 0.81 (0.66, 0.94), and S100B 0.80 (0.67, 0.93) (area under the curve [95% confidence intervals]).

CONCLUSIONS

Prospectively collected brain-specific serum biomarkers predict unfavorable neurological outcome in critically ill children. Serum biomarkers used in conjunction with clinical data could be used to generate models predicting early detection of neurological injury, allowing for more timely diagnostic and therapeutic interventions, potentially reducing neurological morbidity in the PICU.

Intraoperative neuromonitoring during microsurgical clipping for unruptured anterior choroidal artery aneurysm

OBJECTIVE

To investigate the safety and unexpected finding of the intraoperative neuromonitoring (IONM) including somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) during microsurgical clipping of an unruptured anterior choroidal artery (AChA) aneurysm.

PATIENTS AND METHODS

From January 2011 to March 2018, the neurophysiological, clinical, and radiological data of 115 patients who underwent microsurgical clipping for an unruptured AChA aneurysm under IONM were retrospectively analyzed. The incidence of ischemic complications after microsurgical clipping of unruptured AChA aneurysms as well as the false-negative rate, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of IONM during surgery were calculated.

RESULTS

Ischemic complications after the microsurgical clipping of an AChA aneurysm under IONM occurred in 7 of 115 patients (6.08%). Among them, 3 were symptomatic (2.6%). The false-negative rate of IONM for ischemic complications was 6.08% (7 patients). High specificity; 100% (95% confidence interval [95% CI] = 0.972-1.000), PPVs; 100% (95% CI = 0.055-1.000), and NPVs; 93% (95% CI = 0.945-0.973) with low sensitivity; 11.1% (95% CI = 0.006-0.111) were calculated.

CONCLUSIONS

IONM including transcranial MEP during microsurgical clipping of unruptured AChA aneurysm might have limited usefulness. Therefore, other MEP monitoring using direct cortical stimulation or modified transcranial methodology should be considered to compensate for it.

Large animals in neurointerventional research: A systematic review on models, techniques and their application in endovascular procedures for stroke, aneurysms and vascular malformations

Neuroendovascular procedures have led to breakthroughs in the treatment of ischemic stroke, intracranial aneurysms, and intracranial arteriovenous malformations. Due to these substantial successes, there is continuous development of novel and refined therapeutic approaches. Large animal models feature various conceptual advantages in translational research, which makes them appealing for the development of novel endovascular treatments. However, the availability and role of large animal models have not been systematically described so far. Based on comprehensive research in two databases, this systematic review describes current large animal models in neuroendovascular research including their primary use. It may therefore serve as a compact compendium for researchers entering the field or looking for opportunities to refine study concepts. It also describes particular applications for ischemic stroke and aneurysm therapy, as well as for the treatment of arteriovenous malformations. It focuses on most promising study designs and readout parameters, as well as on important pitfalls in endovascular translational research including ways to circumvent them.

Progressive Assessment of Ischemic Injury to White Matter Using Diffusion Tensor Imaging: A Preliminary Study of a Macaque Model of Stroke

Background:

Previous Diffusion Tensor Imaging (DTI) studies have demonstrated the temporal evolution of stroke injury in grey matter and white matter can be characterized by DTI indices. However, it still remains not fully understood how the DTI indices of white matter are altered progressively during the hyperacute (first 6 hours) and acute stage of stroke (≤ 1 week). In the present study, DTI was employed to characterize the temporal evolution of infarction and white matter injury after stroke insult using a macaque model with permanent ischemic occlusion.

Methods and materials:

Permanent middle cerebral artery (MCA) occlusion was induced in rhesus monkeys (n=4, 10-21 years old). The brain lesion was examined longitudinally with DTI during the hyperacute phase (2-6 hours, n=4), 48 hours (n=4) and 96 hours (n=3) post-occlusion.

Results:

Cortical infarction was seen in all animals. The Mean Diffusivity (MD) in lesion regions decreased substantially at the first time point (2 hours post stroke) (35%, p <0.05, compared to the contralateral side) and became pseudo-normalized at 96 hours. In contrast, evident FA reduction was seen at 48 hours (39%, p <0.10) post-stroke. MD reduction in white matter bundles of the lesion area was much less than that in the grey matter during the hyper-acute phase but significant change was observed 4 hours (4.2%, p < 0.05) post stroke . Also, MD pseudonormalisation was seen at 96 hours post stroke. There was a significant correlation between the temporal changes of MD in white matter bundles and those in whole lesion areas during the entire study period. Meanwhile, no obvious fractional anisotropy (FA) changes were seen during the hyper-acute phase in either the entire infarct region or white matter bundles. Significant FA alteration was observed in entire lesion areas and injured white matter bundles 48 and 96 hours post stroke. The stroke lesion in grey matter and white matter was validated by pathological findings.

Conclusion:

The temporal evolution of ischemic injury to the grey matter and white matter from 2 to 96 hours after stroke onset was characterized using a macaque model and DTI. Progressive MD changes in white matter bundles are seen from hyperacute phase to acute phase after permanent MCA occlusion and temporally correlated with the MD changes in entire infarction regions. MD reduction in white matter bundles is mild in comparison with that in the grey matter but significant and progressive, indicating it may be useful to detect early white matter degeneration after stroke.

Advances in chronic cerebral circulation insufficiency

Chronic cerebral circulation insufficiency (CCCI) may not be an independent disease; rather, it is a pervasive state of long-term cerebral blood flow insufficiency caused by a variety of etiologies, and considered to be associated with either occurrence or recurrence of ischemic stroke, vascular cognitive impairment, and development of vascular dementia, resulting in disability and mortality worldwide. This review summarizes the features and recent progress of CCCI, mainly focusing on epidemiology, experimental research, pathophysiology, etiology, clinical manifestations, imaging presentation, diagnosis, and potential therapeutic regimens. Some research directions are briefly discussed as well.

Effects of hyperoxia on 18F-fluoro-misonidazole brain uptake and tissue oxygen tension following middle cerebral artery occlusion in rodents: Pilot studies

PURPOSE

Mapping brain hypoxia is a major goal for stroke diagnosis, pathophysiology and treatment monitoring. 18F-fluoro-misonidazole (FMISO) positron emission tomography (PET) is the gold standard hypoxia imaging method. Normobaric hyperoxia (NBO) is a promising therapy in acute stroke. In this pilot study, we tested the straightforward hypothesis that NBO would markedly reduce FMISO uptake in ischemic brain in Wistar and spontaneously hypertensive rats (SHRs), two rat strains with distinct vulnerability to brain ischemia, mimicking clinical heterogeneity.

METHODS

Thirteen adult male rats were randomized to distal middle cerebral artery occlusion under either 30% O2 or 100% O2. FMISO was administered intravenously and PET data acquired dynamically for 3hrs, after which magnetic resonance imaging (MRI) and tetrazolium chloride (TTC) staining were carried out to map the ischemic lesion. Both FMISO tissue uptake at 2-3hrs and FMISO kinetic rate constants, determined based on previously published kinetic modelling, were obtained for the hypoxic area. In a separate group (n = 9), tissue oxygen partial pressure (PtO2) was measured in the ischemic tissue during both control and NBO conditions.

RESULTS

As expected, the FMISO PET, MRI and TTC lesion volumes were much larger in SHRs than Wistar rats in both the control and NBO conditions. NBO did not appear to substantially reduce FMISO lesion size, nor affect the FMISO kinetic rate constants in either strain. Likewise, MRI and TTC lesion volumes were unaffected. The parallel study showed the expected increases in ischemic cortex PtO2 under NBO, although these were small in some SHRs with very low baseline PtO2.

CONCLUSIONS

Despite small samples, the apparent lack of marked effects of NBO on FMISO uptake suggests that in permanent ischemia the cellular mechanisms underlying FMISO trapping in hypoxic cells may be disjointed from PtO2. Better understanding of FMISO trapping processes will be important for future applications of FMISO imaging.

Impact of time to endovascular reperfusion on outcome differs according to the involvement of the proximal MCA territory

BACKGROUND

The time interval between symptom onset and reperfusion is a major determinant of the benefit of endovascular therapy (ET) and patients' outcome. The impact of time may be attenuated in patients with robust collaterals. However, not all regions in the middle cerebral artery (MCA) territory have access to collaterals.

PURPOSE

To evaluate if the involvement of the poorly collateralized proximal MCA territory has an impact on the degree of time dependency of patients' outcome.

METHODS

Patients with MCA occlusions treated with ET and involvement/sparing of the proximal striatocapsular MCA territory (SC+/SC-, each n=97) were matched according to their symptom onset to reperfusion times (SORTs). Correlation and impact of time on outcome was evaluated with strata of SC+/SC- using multivariate logistic regression models (LRMs), including interaction terms. Discharge National Institute of Health Stroke Scale (NIHSS-DIS) score <5 and discharge modified Rankin Scale (mRS-DIS) score ≤2 were prespecified outcome measures.

RESULTS

A stronger correlation between all outcome measures (NIHSS-DIS/ΔNIHSS/mRS-DIS) and SORTs was found for SC+ patients than for SC-patients. SORTs were significant variables in LRMs for mRS-DIS score ≤2 and NIHSS-DIS score <5 in SC+ but not in SC- patients. Interaction of SC+ and SORTs was significant in LRMs for both endpoints.

CONCLUSION

Time dependency of outcome after ET is more pronounced if parts of the proximal MCA territory are affected. This may reflect the lack of collateralization in the striatocapsular region and a more stringent cell death with time. If confirmed, this finding may affect the selection of patients based on different time windows according to the territory at risk.

Brain hypoxia mapping in acute stroke: Back-to-back T2' MR versus 18F-fluoromisonidazole PET in rodents

Background Mapping the hypoxic brain in acute ischemic stroke has considerable potential for both diagnosis and treatment monitoring. PET using ¹⁸F-fluoro-misonidazole (FMISO) is the reference method; however, it lacks clinical accessibility and involves radiation exposure. MR-based T2' mapping may identify tissue hypoxia and holds clinical potential. However, its validation against FMISO imaging is lacking. Here we implemented back-to-back FMISO-PET and T2' MR in rodents subjected to acute middle cerebral artery occlusion. For direct clinical relevance, regions of interest delineating reduced T2' signal areas were manually drawn. Methods Wistar rats were subjected to filament middle cerebral artery occlusion, immediately followed by intravenous FMISO injection. Multi-echo T2 and T2* sequences were acquired twice during FMISO brain uptake, interleaved with diffusion-weighted imaging. Perfusion-weighted MR was also acquired whenever feasible. Immediately following MR, PET data reflecting the history of FMISO brain uptake during MR acquisition were acquired. T2' maps were generated voxel-wise from T2 and T2*. Two raters independently drew T2' lesion regions of interest. FMISO uptake and perfusion data were obtained within T2' consensus regions of interest, and their overlap with the automatically generated FMISO lesion and apparent diffusion coefficient lesion regions of interest was computed. Results As predicted, consensus T2' lesion regions of interest exhibited high FMISO uptake as well as substantial overlap with the FMISO lesion and significant hypoperfusion, but only small overlap with the apparent diffusion coefficient lesion. Overlap of the T2' lesion regions of interest between the two raters was ∼50%. Conclusions This study provides formal validation of T2' to map non-core hypoxic tissue in acute stroke. T2' lesion delineation reproducibility was suboptimal, reflecting unclear lesion borders.

Effect of Cyclosporine on Lesion Growth and Infarct Size within the White and Gray Matter

Background

In a recent trial, cyclosporine A (CsA) failed to reduce infarct size in acute stroke patients treated with intravenous thrombolysis. White matter (WM) and gray matter (GM) may have distinct vulnerability to ischemia and response to therapy. Using final infarct size and lesion growth as endpoints, our objectives were to (1) investigate any tissue-specific effect of CsA and (2) compare WM and GM response to thrombolysis.

Materials and methods

We analyzed 84 patients from the randomized and placebo-controlled CsA-Stroke trial, who underwent MRI both on admission and at 1 month. Lesion growth was defined voxel-wise as infarcted tissue at 1 month with no visible lesion on baseline diffusion-weighted imaging. After automatic segmentation of GM/WM, final infarct size and lesion growth were compared within the GM and WM.

Results

Occlusion level was distal (>M1) in 51% of cases. No significant difference in GM/WM proportions was observed within final infarcts between treatment groups (P = 0.21). Infarct size within the GM or WM was similar between the CsA and control groups [GM: 9.2 (2.4; 22.8) with CsA vs 8.9 (3.7; 28.4) mL with placebo, P = 0.74; WM: 9.9 (4.7; 25.4) with CsA vs 14.1 (5.6; 34.1) mL with placebo, P = 0.26]. There was no significant effect of CsA on lesion growth in either the GM or WM. Pooling all patients, a trend for increased relative lesion growth in WM compared to GM was observed [49.0% (14.7; 185.7) vs 43.1% (15.4; 117.1), respectively; P = 0.12].

Conclusion

No differential effect of CsA was observed between WM and GM. Pooling all patients, a trend toward greater lesion growth in WM was observed.

White Matter and Gray Matter Segmentation in 4D Computed Tomography

Modern Computed Tomography (CT) scanners are capable of acquiring contrast dynamics of the whole brain, adding functional to anatomical information. Soft tissue segmentation is important for subsequent applications such as tissue dependent perfusion analysis and automated detection and quantification of cerebral pathology. In this work a method is presented to automatically segment white matter (WM) and gray matter (GM) in contrast- enhanced 4D CT images of the brain. The method starts with intracranial segmentation via atlas registration, followed by a refinement using a geodesic active contour with dominating advection term steered by image gradient information, from a 3D temporal average image optimally weighted according to the exposures of the individual time points of the 4D CT acquisition. Next, three groups of voxel features are extracted: intensity, contextual, and temporal. These are used to segment WM and GM with a support vector machine. Performance was assessed using cross validation in a leave-one-patient-out manner on 22 patients. Dice coefficients were 0.81 ± 0.04 and 0.79 ± 0.05, 95% Hausdorff distances were 3.86 ± 1.43 and 3.07 ± 1.72 mm, for WM and GM, respectively. Thus, WM and GM segmentation is feasible in 4D CT with good accuracy.

Intraparenchymal Hyperattenuations on Flat-Panel CT Directly After Mechanical Thrombectomy are Restricted to the Initial Infarct Core on Diffusion-Weighted Imaging

PURPOSE

The presence of intraparenchymal hyperattenuations (IPH) on flat-panel computed tomography (FP-CT) after endovascular recanalization in stroke patients is a common phenomenon. They are thought to occur in ischemic areas with breakdown of the blood-brain barrier but previous studies that investigated a mutual interaction are scarce. We aimed to assess the relationship of IPH localization with prethrombectomy diffusion-weighted imaging (DWI) lesions.

METHODS

This retrospective multicenter study included 27 acute stroke patients who underwent DWI prior to FP-CT following mechanical thrombectomy. After software-based coregistration of DWI and FP-CT, lesion volumetry was conducted and overlapping was analyzed.

RESULTS

Two different patterns were observed: IPH corresponding to the DWI lesion and IPH exceeding the DWI lesion. The latter showed demarcated infarction of DWI exceeding IPH at 24 h. No major hemorrhage following IPH was observed. Most IPH were manifested within the basal ganglia and insular cortex.

CONCLUSION

The IPH primarily appeared within the initial ischemic core and secondarily within the penumbral tissue that progressed to infarction. The IPH represent the minimum final infarct volume, which may help in periinterventional decision making.

Radiological imaging in acute ischaemic stroke

Patients who suffer acute ischaemic stroke can be treated with thrombolysis if therapy is initiated early. Radiological evaluation of the intracranial tissue before such therapy can be given is mandatory. In this review current radiological diagnostic strategies are discussed for this patient group. Beyond non-enhanced computed tomography (CT), the standard imaging method for many years, more sophisticated CT stroke protocols including CT angiography and CT perfusion have been developed, and additionally an increasing number of patients are examined with magnetic resonance imaging as the first imaging method used. Advantages and challenges of the different methods are discussed.

Diffusion-weighted lesions in stroke patients with transient symptoms--where are they located?

BACKGROUND

MR diffusion-weighted imaging (DWI) has revolutionized neuroimaging and contributed to a tissue-based redefinition of transient ischemic attack (TIA). Stroke patients with DWI lesions may have neurological symptoms that resolve completely within 24 h, suggesting successful vessel recanalization. Prior studies of stroke patients with transient symptoms have not found any predilection for DWI lesions in any specific territory. Other studies have, however, reported an association between higher brain dysfunction and presence of DWI lesions in patients with transient ischemic symptoms, suggesting a high rate of cortical affection in these patients. We sought to see whether DWI location in stroke patients with transient symptoms <24 h differed from those with persistent symptoms ≥ 24 h. We hypothesized an association between transient symptoms <24 h and cortical DWI lesion localization due to a possible higher rate of vessel recanalization in patients with transient symptoms causing distal cortical infarctions.

METHODS

Ischemic stroke patients examined with DWI and admitted within 24 h after symptom onset between February 2006 and November 2013 were prospectively registered in a database (The Bergen NORSTROKE Registry). Based on neurological examination 24 h after admission, patients were classified as having either transient symptoms <24 h (DWI <24) or persistent symptoms ≥ 24 h (DWI ≥ 24). DWI lesions were classified into different groups depending on lesion location: cortical lesions, confined to the supratentorial cortex; large subcortical lesions, located in the hemispheric white matter, basal ganglia, internal capsule, thalamus or corona radiate with a diameter ≥ 15 mm; lacunar lesions, located in the same territory as large subcortical lesions with a diameter <15 mm; mixed cortical-subcortical lesions, located in both supratentorial cortex and subcortex; cerebellar lesions, confined to the cerebellum; brain stem lesions, confined to the brain stem; multiple locations, located in more than one of the above defined areas.

RESULTS

A total of 142 ischemic stroke patients had DWI <24 and 830 DWI ≥ 24. Cortical DWI location was more frequent in patients with DWI <24 (54.2% vs. 29.5%, p < 0.001), while proportions of mixed cortical-subcortical lesions (13.4% vs. 26.5%, p = 0.001) and lesions with multiple locations (5.6% vs. 11.1%, p = 0.048) were less frequent as compared to DWI ≥ 24. Cortical DWI location was independently associated with DWI <24 when adjusted for confounders in multiple regression analyses (OR 1.89, 95% CI 1.28-2.81, p = 0.001).

CONCLUSION

Cortical DWI location was independently associated with transient stroke symptoms <24 h. This may be explained by vessel recanalization, resulting in upstream transportation of remaining particles and distal cortical lesions.

Serum biomarkers of brain injury to classify outcome after pediatric cardiac arrest*

OBJECTIVES

Morbidity and mortality in children with cardiac arrest largely result from neurologic injury. Serum biomarkers of brain injury can potentially measure injury to neurons (neuron-specific enolase), astrocytes (S100b), and axons (myelin basic protein). We hypothesized that serum biomarkers can be used to classify outcome from pediatric cardiac arrest.

DESIGN

Prospective observational study.

SETTING

Single tertiary pediatric hospital.

PATIENTS

Forty-three children with cardiac arrest.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured serum neuron-specific enolase, S100b, and myelin basic protein on days 1-4 and 7 after cardiac arrest. We recorded demographics, details of the cardiac arrest and resuscitation, and Pediatric Cerebral Performance Category at hospital discharge and 6 months. We analyzed the association of biomarker levels at 24, 48, and 72 hours with favorable (Pediatric Cerebral Performance Category 1-3) or unfavorable (Pediatric Cerebral Performance Category 4-6) outcome and mortality. Forty-three children (49% female; mean age of 5.9 ± 6.3) were enrolled and 17 (40%) died. Serum S100b concentrations peaked earliest, followed by neuron-specific enolase and finally myelin basic protein. Serum neuron-specific enolase and S100b concentrations were increased in the unfavorable versus favorable outcome group and in subjects who died at all time points (all p < 0.05). Serum myelin basic protein at 24 and 72 hours correctly classified survival but not good versus poor outcome. Using best specificity, serum S100b and neuron-specific enolase had optimal positive and negative predictive values at 24 hours to classify both favorable versus unfavorable outcome and survival, whereas serum myelin basic protein's best accuracy occurred at 48 hours. Receiver operator curves for serum S100b and neuron-specific enolase to classify favorable versus unfavorable outcome at 6 months were superior to clinical variables.

CONCLUSIONS

Preliminary data show that serum S100b, neuron-specific enolase, and myelin basic protein may aid in outcome classification of children surviving cardiac arrest.

Diffusion and perfusion correlates of the 18F-MISO PET lesion in acute stroke: pilot study

PURPOSE

Mapping the ischaemic penumbra in acute stroke is of considerable clinical interest. For this purpose, mapping tissue hypoxia with (18)F-misonidazole (FMISO) PET is attractive, and is straightforward compared to (15)O PET. Given the current emphasis on penumbra imaging using diffusion/perfusion MR or CT perfusion, investigating the relationships between FMISO uptake and abnormalities with these modalities is important.

METHODS

According to a prospective design, three patients (age 54-81 years; admission NIH stroke scale scores 16-22) with an anterior circulation stroke and extensive penumbra on CT- or MR-based perfusion imaging successfully completed FMISO PET, diffusion-weighted imaging and MR angiography 6-26 h after stroke onset, and follow-up FLAIR to map the final infarction. All had persistent proximal occlusion and a poor outcome despite thrombolysis. Significant FMISO trapping was defined voxel-wise relative to ten age-matched controls and mapped onto coregistered maps of the penumbra and irreversibly damaged ischaemic core.

RESULTS

FMISO trapping was present in all patients (volume range 18-119 ml) and overlapped mainly with the penumbra but also with the core in each patient. There was a significant (p ≤ 0.001) correlation in the expected direction between FMISO uptake and perfusion, with a sharp FMISO uptake bend around the expected penumbra threshold.

CONCLUSION

FMISO uptake had the expected overlap with the penumbra and relationship with local perfusion. However, consistent with recent animal data, our study suggests FMISO trapping may not be specific to the penumbra. If confirmed in larger samples, this preliminary finding would have potential implications for the clinical application of FMISO PET in acute ischaemic stroke.

Is overactive bladder a brain disease? The pathophysiological role of cerebral white matter in the elderly

Small-vessel disease of the brain affecting the deep white matter characteristically manifests with neurological syndromes, such as vascular dementia and vascular parkinsonism. There is, however, compelling evidence to suggest that white matter disease can cause overactive bladder and incontinence, and in some patients these might be the initial manifestation. As white matter disease increases significantly with age, and preferentially affects the prefrontal deep white matter, white matter disease becomes an anatomical substrate in the brain etiology of overactive bladder. Treatment entails the management of small-vessel disease risk factors and anticholinergic drugs that do not easily penetrate the blood-brain barrier, to improve bladder control. In short, when caring for elderly overactive-bladder patients, we should look at both the brain and the bladder.

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.

Vascular incontinence: incontinence in the elderly due to ischemic white matter changes

This review article introduces the new concept of vascular incontinence, a disorder of bladder control resulting from cerebral white matter disease (WMD). The concept is based on the original observation in 1999 of a correlation between the severity of leukoareosis or WMD, urinary symptoms, gait disorder and cognitive impairment. Over the last 20 years, the realization that WMD is not a benign incidental finding in the elderly has become generally accepted and several studies have pointed to an association between geriatric syndromes and this type of pathology. The main brunt of WMD is in the frontal regions, a region recognized to be crucial for bladder control. Other disorders should be excluded, both neurological and urological, such as normal-pressure hydrocephalus, progressive supranuclear palsy, etc., and prostatic hyperplasia, physical stress incontinence, nocturnal polyuria, etc. Treatment involves management of small vessel disease risk factors and anticholinergic drugs that do not easily penetrate the blood brain barrier to improve bladder control.

Progesterone pharmacokinetics in the mouse: implications for potential stroke therapy

OBJECTIVES

Progesterone has been shown to be neuroprotective in a number of preclinical central nervous system injury models including cerebral ischaemia. The aim of this study was to clarify differences in outcomes owing to different dosing regimens and the pharmacokinetic profile of progesterone, particularly in relation to brain levels.

METHODS

Male C57 Bl/6 mice were injected intraperitoneally with progesterone (8 mg/kg in dimethylsulfoxide) or with a bolus injection followed by continuous subcutaneous infusion (1.0 µl/h of a 50 mg/ml progesterone solution) via implanted osmotic minipumps. Plasma and brain samples were collected over 24 h from bolus-injected mice and 48 h from mice implanted with minipumps. Progesterone concentrations were measured by an enzyme-linked immunoassay and pharmacokinetic profiles were constructed.

KEY FINDINGS

Intraperitoneally injected progesterone had a short half-life (fast component half-life of 0.2 h) in both plasma and brain. Minipump delivery resulted in higher concentrations of progesterone in plasma and particularly in brain over a longer period. The volume of distribution with intraperitoneal injection was 172.78 versus 1641.84 ng/h per g via minipump in the first 24 h.

CONCLUSIONS

A bolus intraperitoneal loading dose of progesterone followed by continuous delivery via osmotic minipump is an effective way of delivering progesterone to the brain.

Monitoring techniques for prevention of procedure-related ischemic damage in aneurysm surgery

OBJECTIVE

To describe the application of intraoperative monitoring techniques during aneurysm surgery and to discuss the advantages and limitations of these techniques in prevention of postoperative neurologic deficits.

METHODS

Articles found in the literature through PubMed for the time frame 1980-2011 and the authors' personal files were reviewed.

RESULTS

Various techniques for detection of vascular insufficiency are available, including direct methods to measure cerebral blood flow and indirect methods to evaluate the integrity of neurologic pathways.

CONCLUSIONS

The choice of monitoring modality should be governed by the vessel and by the vascular territory most at risk during the planned procedure with proper awareness of the potential limits related to each technique. Aneurysm surgery monitoring should help to address issues of continuity and provide a morphologic and functional assessment. Although the use of monitoring devices is still not routine in aneurysm surgery and no standards have been established, combining different monitoring techniques is crucial to optimize aneurysm surgery and avoid or minimize complications.

Proof of concept: pharmacological preconditioning with a Toll-like receptor agonist protects against cerebrovascular injury in a primate model of stroke

Cerebral ischemic injury is a significant portion of the burden of disease in developed countries; rates of mortality are high and the costs associated with morbidity are enormous. Recent therapeutic approaches have aimed at mitigating the extent of damage and/or promoting repair once injury has occurred. Often, patients at high risk of ischemic injury can be identified in advance and targeted for antecedent neuroprotective therapy. Agents that stimulate the innate pattern recognition receptor, Toll-like receptor 9, have been shown to induce tolerance (precondition) to ischemic brain injury in a mouse model of stroke. Here, we demonstrate for the first time that pharmacological preconditioning against cerebrovascular ischemic injury is also possible in a nonhuman primate model of stroke in the rhesus macaque. The model of stroke used is a minimally invasive transient vascular occlusion, resulting in brain damage that is primarily localized to the cortex and as such, represents a model with substantial clinical relevance. Finally, K-type (also referred to as B-type) cytosine-guanine-rich DNA oligonucleotides, the class of agents employed in this study, are currently in use in human clinical trials, underscoring the feasibility of this treatment in patients at risk of cerebral ischemia.

'Salvaged' stroke ischaemic penumbra shows significant injury: studies with the hypoxia tracer FMISO

The degree of cellular injury within the stroke ischaemic penumbra is controversial. Clinical and experimental studies using the hypoxia tracer fluoromisonidazole (FMISO) have shown retention of this tracer in the penumbra, but cellular outcome has not been well characterised. We hypothesised that macroscopically intact FMISO-retaining penumbral tissues would show evidence of microscopic injury, and that no FMISO retention would be seen in the infarct core. To determine the distribution of FMISO retention, a tritium-labelled tracer (hydrogen-3 FMISO ([(3)H]FMISO)) was administered 5 minutes after induction of 2-hour temporary middle cerebral artery occlusion. Coregistered brain histology and autoradiography at 24 hours revealed marked retention of FMISO within the infarct. However, 48% of the FMISO-retaining tissue was not infarcted. Within this noninfarcted tissue, only 27% (17 of 64) of sampled regions showed no evidence of neuronal loss, whereas 44% (28 of 64) showed injury to >50% of neurons within the sample. To determine whether FMISO retention occurred after the tissue was already committed to infarction, FMISO was administered 4 to 6 hours after the onset of permanent vessel occlusion. Intense FMISO retention was consistently seen throughout the infarct core. In conclusion, FMISO retention occurs both within the ischaemic penumbra and within the early infarct core. Most penumbral tissues show evidence of selective cellular injury.

Penumbra, the basis of neuroimaging in acute stroke treatment: current evidence

In modern medicine brain imaging is an essential prerequisite not only to acute stroke triage but also to determining the specific therapy indicated. This article reviews the need for imaging the brain in acute stroke, penumbral pathophysiology, penumbral imaging techniques, as well as current status of various imaging modalities that are being employed to select patients for specific therapeutic approaches.

Applications of nitroimidazole in vivo hypoxia imaging in ischemic stroke

BACKGROUND AND PURPOSE

Nitroimidazole imaging is a promising contender for noninvasive in vivo mapping of brain hypoxia after stroke. However, there is a dearth of knowledge about the behavior of these compounds in the various pathophysiologic situations encountered in ischemic stroke. In this article we report the findings from a systematic review of the literature on the use of the nitroimidazoles to map hypoxia after stroke.

SUMMARY OF REVIEW

We describe the characteristics of nitroimidazoles as imaging tracers, their pharmacology, and results of both animal and clinical studies during and after focal cerebral ischemia. Findings in brain tumors are also presented to the extent that they enlighten results in stroke. Early results from application of kinetic modeling for quantitative measurement of tracer binding are briefly discussed.

CONCLUSIONS

Based on this literature review, nitroimidazole hypoxia imaging agents are of considerable interest in stroke because they appear, both in animal models and in humans, to specifically detect the severely hypoxic viable tissue, but not the reperfused nor the necrotic tissue. To fully realize this potential in stroke, however, formal validation by concurrent measurement of tissue oxygen tension, together with development of novel ligands with faster distribution kinetics, faster clearance from normal tissue, and well-defined trapping mechanisms, are important goals for future investigations.