Serum Neurofilament Light Chain Concentration Correlates with Infarct Volume but Not Prognosis in Acute Ischemic Stroke

Circulating levels of neurofilament light chain as a biomarker of infarct and white matter hyperintensity volumes after ischemic stroke

Serum neurofilament light chain protein (sNfL) shows promise as a biomarker for infarct size in acute ischemic stroke and for monitoring cerebral small vessel disease (cSVD). However, distinguishing the cSVD contribution after stroke may not be possible due to post-stroke sNfL increase. Additionally, it remains unclear if etiologic subtype differences exist. We measured infarct and white matter hyperintensity (WMH) volumes using MRI at the index stroke in ischemic stroke patients (n = 316, mean age 53 years, 65% males) and at 7-year follow-up (n = 187). Serum NfL concentration was measured in the acute phase (n = 235), at 3-months (n = 288), and 7-years (n = 190) post stroke. In multivariable regression, acute and 3-month sNfL concentrations were associated with infarct volume and time since stroke, but not with stroke etiology or infarct location. Seven years post-stroke, sNfL was associated with WMHs and age, but not with stroke etiology. Nonlinear regression estimated that sNfL peaks around 1 month, and declines by 50% at 3 months, and 99% at 9 months. We conclude that sNfL can indicate infarct volume and time since brain injury in the acute and subacute phases after stroke. Due to the significant post-stroke sNfL increase, several months are needed for reliable assessment of cSVD activity.

Neurofilaments as biomarkers in neurological disorders - towards clinical application

Neurofilament proteins have been validated as specific body fluid biomarkers of neuro-axonal injury. The advent of highly sensitive analytical platforms that enable reliable quantification of neurofilaments in blood samples and simplify longitudinal follow-up has paved the way for the development of neurofilaments as a biomarker in clinical practice. Potential applications include assessment of disease activity, monitoring of treatment responses, and determining prognosis in many acute and chronic neurological disorders as well as their use as an outcome measure in trials of novel therapies. Progress has now moved the measurement of neurofilaments to the doorstep of routine clinical practice for the evaluation of individuals. In this Review, we first outline current knowledge on the structure and function of neurofilaments. We then discuss analytical and statistical approaches and challenges in determining neurofilament levels in different clinical contexts and assess the implications of neurofilament light chain (NfL) levels in normal ageing and the confounding factors that need to be considered when interpreting NfL measures. In addition, we summarize the current value and potential clinical applications of neurofilaments as a biomarker of neuro-axonal damage in a range of neurological disorders, including multiple sclerosis, Alzheimer disease, frontotemporal dementia, amyotrophic lateral sclerosis, stroke and cerebrovascular disease, traumatic brain injury, and Parkinson disease. We also consider the steps needed to complete the translation of neurofilaments from the laboratory to the management of neurological diseases in clinical practice.

Functional Outcome and Mortality Predictors in Patients with Cerebral Ischemic Infarction After Decompressive Craniectomy: Cross-Sectional Study

OBJECTIVE

Surgeons commonly perform Decompressive craniectomy (DC) to manage patients with cerebral ischemic infarction. However, there are conflicting data on the long-term functional outcomes following DC. Therefore, this study aims to determine the functional outcome of patients with cerebral ischemic infarction after DC.

METHODS

This prospective and retrospective cross-sectional study included 148 patients with cerebral ischemic infarction who underwent DC at Ghaem Hospital, Mashhad, Iran, from March 2011 to March 2021. The Modified Rankin Scale (mRS) assesses disability in these patients and determines the recovery and degree of long-term functional outcomes. Demographic and clinical data were extracted and recorded in a researcher-made questionnaire.

RESULTS

In summary, the follow-up revealed a survival rate of 39.2% among patients with ischemic stroke. The comparison of the mean infarct volume in patients with various mRS scores showed that the mean infarct volume was significantly higher in patients with unfavorable functional outcomes, based on mRS scores at discharge (P = 0.05), 3 months mRS (P < 0.01), and mRS score at final follow-up (P = 0.01). Final mortality was higher in patients with higher mRS scores at discharge, after 3 months, and final follow-up (P < 0.01). Older age and infarction volume can predict mRS and mortality in patients with ischemic stroke (P < 0.01).

CONCLUSIONS

The present study showed that mortality and mRS scores at various times are associated with infarction volume and older age in patients with ischemic stroke.

Role of Microglia in Stroke

Ischemic stroke is a complex brain pathology caused by an interruption of blood supply to the brain. It results in neurological deficits which that reflect the localization and the size of the compromised brain area and are the manifestation of complex pathogenic events triggered by energy depletion. Inflammation plays a prominent role, worsening the injury in the early phase and influencing poststroke recovery in the late phase. Activated microglia are one of the most important cellular components of poststroke inflammation, appearing from the first few hours and persisting for days and weeks after stroke injury. In this chapter, we will discuss the nature of the inflammatory response in brain ischemia, the contribution of microglia to injury and regeneration after stroke, and finally, how ischemic stroke directly affects microglia functions and survival.

Strict blood pressure control following thrombectomy is associated with neuronal injury and poor functional outcome

OBJECTIVE

Mechanical thrombectomy (MT) has become standard treatment in acute ischemic stroke due to large vessel occlusion (LVO). However, optimal blood pressure (BP) management following successful recanalization remains unclear. We aim to investigate the association of strictly achieving BP targets of ≤160/90 mmHg with the extent of neuronal loss and functional outcome.

METHODS

In patients prospectively enrolled in the Gutenberg-Stroke-Study (May 2018-November 2019), BP was measured half-hourly for 24 h following MT. Based on achieving BP target of ≤160/90 mmHg, patients with successful recanalization of LVO were divided into "low-BP" group (BP ≤ 160/90 mmHg) or "high-BP" group (BP > 160/90 mmHg). Neuronal loss was quantified by serum-based measurement of neurofilament light chain (sNfL) after three days. BP groups and association of BP parameters with sNfL were investigated by correlation analyses and multiple regression modeling.

RESULTS

Of 253 enrolled patients (mean age 73.1 ± 12.9 years, 53.4% female), 165 met inclusion criteria. 21.2% (n = 35) strictly achieved "low-BP" target. "low-BP" was associated with unfavorable functional outcome at 90-day follow-up (aOR [95%CI]: 5.88 [1.88-18.32], p = 0.002) and decreased health-related quality of life (mean EQ-5D-index 0.45 ± 0.28 vs 0.63 ± 0.31, p = 0.009). sNfL levels were increased in "low-BP" patients (median [IQR] 239.7 [168.4-303.4] vs 118.8 [52.5-220.5] pg/mL, p = 0.026). Hypotensive episodes were more frequent in the "low-BP" group (48.6% vs 29.2%, p = 0.031). sNfL level could identify patients who had experienced hypotensive episodes with high discriminative ability (AUC [95%CI]: 0.68 [0.56-0.78], p = 0.007).

INTERPRETATION

Strict BP control (≤160/90 mmHg) within 24 h following successful recanalization of LVO by MT is associated with increased neuronal injury, displayed by higher sNfL levels, and poorer functional outcome, potentially indicating hypotension-induced neuronal loss during post-MT phase.

Quantification and prospective evaluation of serum NfL and GFAP as blood-derived biomarkers of outcome in acute ischemic stroke patients

Identification of reliable and accessible biomarkers to characterize ischemic stroke patients' prognosis remains a clinical challenge. Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) are markers of brain injury, detectable in blood by high-sensitive technologies. Our aim was to measure serum NfL and GFAP after stroke, and to evaluate their correlation with functional outcome and the scores in rehabilitation scales at 3-month follow-up. Stroke patients were prospectively enrolled in a longitudinal observational study within 24 hours from symptom onset (D1) and monitored after 7 (D7), 30 ± 3 (M1) and 90 ± 5 (M3) days. At each time-point serum NfL and GFAP levels were measured by Single Molecule Array and correlated with National Institute of Health Stroke Scale (NIHSS), modified Rankin scale (mRS), Trunk Control Test (TCT), Functional Ambulation Classification (FAC) and Functional Independence Measure (FIM) scores. Serum NfL and GFAP showed different temporal profiles: NfL increased after stroke with a peak value at D7; GFAP showed an earlier peak at D1. NfL and GFAP concentrations correlated with clinical/rehabilitation outcomes both longitudinally and prospectively. Multivariate analysis revealed that NfL-D7 and GFAP-D1 were independent predictors of 3-month NIHSS, TCT, FAC and FIM scores, with NfL being the biomarker with the best predictive performance.

Secondary neurodegeneration following Stroke: what can blood biomarkers tell us?

Stroke is one of the leading causes of death and the primary source of disability in adults, resulting in neuronal necrosis of ischemic areas, and in possible secondary degeneration of regions surrounding or distant to the initial damaged area. Secondary neurodegeneration (SNDG) following stroke has been shown to have different pathogenetic origins including inflammation, neurovascular response and cytotoxicity, but can be associated also to regenerative processes. Aside from focal neuronal loss, ipsilateral and contralateral effects distal to the lesion site, disruptions of global functional connectivity and a transcallosal diaschisis have been reported in the chronic stages after stroke. Furthermore, SNDG can be observed in different areas not directly connected to the primary lesion, such as thalamus, hippocampus, amygdala, substantia nigra, corpus callosum, bilateral inferior fronto-occipital fasciculus and superior longitudinal fasciculus, which can be highlighted by neuroimaging techniques. Although the clinical relevance of SNDG following stroke has not been well understood, the identification of specific biomarkers that reflect the brain response to the damage, is of paramount importance to investigate in vivo the different phases of stroke. Actually, brain-derived markers, particularly neurofilament light chain, tau protein, S100b, in post-stroke patients have yielded promising results. This review focuses on cerebral morphological modifications occurring after a stroke, on associated cellular and molecular changes and on state-of-the-art of biomarkers in acute and chronic phase. Finally, we discuss new perspectives regarding the implementation of blood-based biomarkers in clinical practice to improve the rehabilitation approaches and post stroke recovery.

Plasma Neurofilament Light Chain Is Elevated after Transcatheter Aortic Valve Implantation

INTRODUCTION

Transcatheter aortic valve implantation (TAVI) is associated with a high incidence of new silent brain infarcts (SBIs) on postprocedural neuroimaging. A venous blood sample reflecting neuronal damage following TAVI could help identify patients with potential SBIs. We aimed to investigate if a biochemical marker of neuronal injury, neurofilament light chain (NFL), is elevated after TAVI.

METHODS

In this observational study, NFL was measured in plasma from 31 patients before and after TAVI. Multivariable regression analysis was performed to investigate any effect of clinical- and procedure-related factors on differences in NFL levels before and after TAVI.

RESULTS

Samples were collected 41 (14-81) days before and 44 (35-59) days after TAVI, median (interquartile range). Median age was 81 (77-84) years, and 35% were female. No patient had any overt procedure-related neurological complications. The geometric mean (95% confidence interval) of the NFL concentration was 30 (25-36) pg/mL before TAVI and 48 (39-61) pg/mL, after TAVI, p <0.001. None of the included variables in the multiple linear regression model were statistically significantly associated with the difference in levels before and after TAVI.

CONCLUSIONS

NFL levels in plasma were higher after TAVI as compared with levels before, with a mean increase of 60% (18 pg/mL). Further studies including neuroimaging and cognitive outcomes are needed to understand the potential value of measuring NFL in relation to TAVI.

Serum neurofilament light chain levels are associated with early neurological deterioration in minor ischemic stroke

Objectives

Patients with minor ischemic stroke (MIS) frequently suffer from early neurological deterioration (END) and become disabled. Our study aimed to explore the association between serum neurofilament light chain (sNfL) levels and END in patients with MIS.

Methods

We conducted a prospective observational study in patients with MIS [defined as a National Institutes of Health Stroke Scale (NIHSS) score 0–3] admitted within 24 h from the onset of symptoms. sNfL levels were measured at admission. The primary outcome was END, defined as an increase in the NIHSS score by ≥2 points within 5 days after admission. Univariate and multivariate analyses were performed to explore the risk factors associated with END. Stratified analyses and interaction tests were conducted to identify variables that might modify the association between sNfL levels and END.

Results

A total of 152 patients with MIS were enrolled, of which 24 (15.8%) developed END. The median sNfL level was 63.1 [interquartile range (IQR), 51.2–83.4] pg/ml on admission, which was significantly higher than that of 40 age- and sex-matched healthy controls (median 47.6, IQR 40.8–56.1 pg/ml; p &lt; 0.001). Patients with MIS with END had a higher level of sNfL (with ND: median 74.1, IQR 59.5–89.8 pg/ml; without END: median 61.2, IQR 50.5–82.2 pg/ml; p = 0.026). After adjusting for age, baseline NIHSS score, and potential confounding factors in multivariate analyses, an elevated sNfL level (per 10 pg/mL) was associated with an increased risk of END [odds ratio (OR) 1.35, 95% confidence interval (CI) 1.04–1.77; p = 0.027). Stratified analyses and interaction tests demonstrated that the association between sNfL and END did not change by age group, sex, baseline NIHSS score, Fazekas' rating scale, hypertension, diabetes mellitus, intravenous thrombolysis, and dual antiplatelet therapy in patients with MIS (all p for interaction &gt; 0.05). END was associated with an increased risk of unfavorable outcomes (modified Rankin scale score ranging from 3 to 6) at 3 months.

Conclusion

Early neurological deterioration is common in minor ischemic stroke and is associated with poor prognosis. The elevated sNfL level was associated with an increased risk of early neurological deterioration in patients with minor ischemic stroke. sNfL might be a promising biomarker candidate that can help to identify patients with minor ischemic stroke at high risk of neurological deterioration, for reaching individual therapeutic decisions in clinical practice.

Neurofilament light is associated with clinical outcome and hemorrhagic transformation in moderate to severe ischemic stroke

Background

Ischemic stroke is a leading cause of morbidity and mortality worldwide. One possible predictor is the use of biomarkers especially neurofilament light chain (NFL).

Objectives

To explore whether NFL could predict clinical outcome and hemorrhagic transformation in moderate to severe stroke.

Design

Single center prospective cohort study.

Methods

Fifty-one moderate to severe ischemic stroke patients were recruited. Blood NFL was obtained from patients at admission (First sample) and 24-96 hours later (Second sample). NFL was analyzed with the ultrasensitive single molecule array (Simoa). Later, we calculated incremental rate NFL (IRN) by changes in NFL per day from baseline. We evaluated National Institute of Health stroke scale (NIHSS), modified Rankins score (mRs), and the presence of hemorrhagic transformation (HT).

Results

IRN was found to be higher in patients with unfavorable outcome (7.12 vs 24.07, P = .04) as well as Second sample (49.06 vs 71.41, P = .011), while NFL First sample was not significant. IRN had a great correlation with mRS (r = .552, P < .001). Univariate logistic regression model showed OR of IRN and Second sample to be 1.081 (95% CI 1.016-1.149, P = .013) and 1.019 (1.002-1.037, P = .03), respectively. Multiple logistic regression model has shown to be significant. In receiver operating analysis, IRN, Second sample, combined IRN with NIHSS and combined Second sample with NIHSS showed AUC (.744, P = .004; 0.713, P = .01; 0.805, P < .001; 0.803, P < .001, respectively). For HT, First sample and Second sample had significant difference with HT (Z = 2.13, P = .033; Z = 2.487, P = .013, respectively).

Conclusion

NFL was found to correlate and predict clinical outcome. In addition, it was found to correlate with HT.

Serum neurofilament light chain levels are correlated with the infarct volume in patients with acute ischemic stroke

Neurofilament light chains (NfLs) are promising biomarkers of neuroaxonal damage in stroke patients. We investigated the correlations between NfL levels and infarct volume, initial stroke severity, and functional outcomes at discharge in patients with acute ischemic stroke. We prospectively included 15 patients with first-ever acute ischemic stroke and 8 age- and sex-matched healthy controls without other neurological disorders. Serum NfL levels were measured using the single-molecule array (Simoa) technique twice within 24 hours of admission (NfL1D) and on the seventh hospital day (NfL7D) in patients with stroke and once in healthy controls. We assessed the infarct volume on diffusion-weighted magnetic resonance imaging using the free software ITK-SNAP. Serum NfL1D levels in stroke patients were significantly higher (28.4 pg/mL; interquartile range [IQR], 43.0) than in healthy controls (14.5 pg/mL; IQR, 3.2; P = .005). Temporal pattern analyses demonstrated that NfL7D levels were increased (114.0 pg/mL; IQR, 109.6) compared to NfL1D levels in all stroke patients (P = .001). There was a strong correlation between NfL7D levels and infarct volume (R = 0.67, P = .007). The difference between NfL1D and NfL7D (NfLdiff levels) was strongly correlated with the infarct volume (R = 0.63; P = .013). However, there was no statistically significant correlation between NfL levels and the initial stroke severity or functional outcomes at discharge. NfL levels in the subacute stage of stroke and the NfL difference between admission and 7th day of hospital were correlated with infarct volume in patients with acute ischemic stroke.

Serum Neurofilament Light Chain in Patients With Atrial Fibrillation

Background

Atrial fibrillation (AF) is associated with stroke and MRI features of cerebral tissue damage but its impact on levels of serum neurofilament light chain (sNFL), an established biochemical marker of neuroaxonal damage, is unknown.

Methods and Results

In this observational study, sNFL was analyzed in 280 patients with AF and 280 controls without AF matched for age, sex, and diabetes status within the STABILITY (Stabilization of Atherosclerotic Plaque by Initiation of Darapladib Therapy) trial. None of the patients had a history of previous stroke or transient ischemic attack. Patients with a diagnosis of AF were divided into two groups based on if they were in AF rhythm at the time of blood sampling (AF ECG+, n=74), or not (AF ECG−, n=206). Multiple linear regression analysis was performed to adjust for clinical risk factors. In patients with AF, the levels of sNFL were 15% (AF ECG+) and 10% (AF ECG−) higher than in the control group after adjustment for clinical risk factors, P =0.047 and 0.04, respectively. There was no association between anticoagulation treatment and sNFL levels.

Conclusions

sNFL was elevated in patients with AF compared with matched controls without AF. Ongoing AF rhythm was associated with even higher levels of sNFL than in patients with a diagnosis of AF but currently not in AF rhythm. Anticoagulation treatment did not affect sNFL levels.

Trial Registration

ClinicalTrials.gov NCT00799903.

Plasma Neurofilament Light Chain Is Associated with Cognitive Impairment after Posterior Circulation Stroke

Background

Neurofilament light chain (NfL) is a biomarker for large-caliber axonal degeneration in the subcortex. The purpose of this research was to examine the relationship between plasma neurofilament light chain (pNfL) and cognitive impairment following a posterior circulation stroke.

Methods

Patients over the age of 18 with their first-ever acute ischemic stroke (AIS) of the posterior cerebral circulation within 24 h of symptom onset were included from July 1, 2017, to December 31, 2019. Blood samples were collected within 48 h after the stroke. The Montreal Cognitive Assessment (MOCA) (MOCA < 26) was adopted to define poststroke cognitive impairment (PSCI) 90 days after stroke onset.

Results

A total of 264 patients were analyzed in this research 101 (38.30%) patients were clinically diagnosed with PSCI. The PNfL concentration was significantly higher in the PSCI group compared with the non-PSCI group (p < 0.001). The pNfL concentration (OR 1.044; p < 0.001) remained to be a significant predictor for PSCI after a multivariable logistic regression analysis, even after adjusting for factors including age, sex, education background (OR 1.044; p < 0.001), baseline NIHSS, infarct volume, and TOAST classification (OR 1.035; p < 0.001). The diagnostic efficacy of pNfL concentration for PSCI was then explored with a ROC analysis. The optimum pNfL concentration threshold was 38.12 pg/ml, with a sensitivity of 78.20%, a specificity of 66.9%, and an AUC of 0.782 (p < 0.001).

Conclusion

This research showed that pNfL concentration, independent of established conventional risk factors, could predict the cognitive impairment in 90 days following posterior circulation stroke.

Neurofilament light chain plasma levels are associated with area of brain damage in experimental cerebral malaria

Neurofilament light chain (NfL), released during central nervous injury, has evolved as a powerful serum marker of disease severity in many neurological disorders, including infectious diseases. So far NfL has not been assessed in cerebral malaria in human or its rodent model experimental cerebral malaria (ECM), a disease that can lead to fatal brain edema or reversible brain edema. In this study we assessed if NfL serum levels can also grade disease severity in an ECM mouse model with reversible (n = 11) and irreversible edema (n = 10). Blood–brain-barrier disruption and brain volume were determined by magnetic resonance imaging. Neurofilament density volume as well as structural integrity were examined by electron microscopy in regions of most severe brain damage (olfactory bulb (OB), cortex and brainstem). NfL plasma levels in mice with irreversible edema (317.0 ± 45.01 pg/ml) or reversible edema (528.3 ± 125.4 pg/ml) were significantly increased compared to controls (103.4 ± 25.78 pg/ml) by three to five fold, but did not differ significantly in mice with reversible or irreversible edema. In both reversible and irreversible edema, the brain region most affected was the OB with highest level of blood–brain-barrier disruption and most pronounced decrease in neurofilament density volume, which correlated with NfL plasma levels (r = − 0.68, p = 0.045). In cortical and brainstem regions neurofilament density was only decreased in mice with irreversible edema and strongest in the brainstem. In reversible edema NfL plasma levels, MRI findings and neurofilament volume density normalized at 3 months’ follow-up. In conclusion, NfL plasma levels are elevated during ECM confirming brain damage. However, NfL plasma levels fail short on reliably indicating on the final outcomes in the acute disease stage that could be either fatal or reversible. Increased levels of plasma NfL during the acute disease stage are thus likely driven by the anatomical location of brain damage, the olfactory bulb, a region that serves as cerebral draining pathway into the nasal lymphatics.

Temporal Patterning of Neurofilament Light as a Blood-Based Biomarker for Stroke: A Systematic Review and Meta-Analysis

Damage to axons is a core feature of ischemic stroke and cerebrovascular disease. The burden of axonal injury is correlated with the acute clinical deficits, the underlying burden of ischemic brain injury, the prognosis of recovery, and may be a meaningful therapeutic target for brain repair. Neurofilament light chain (NfL) has been identified as a blood-based biomarker that reflects neuroaxonal damage resulting from stroke. However, the utility of NfL as a blood-based biomarker in stroke is confounded by studies examining different temporal windows and patient populations. We conducted a systematic review and meta-analysis to verify the utility of blood NfL as a diagnostic, prognostic, and monitoring stroke biomarker. Nineteen studies reporting serum/plasma NfL values for a total of 4,237 distinct patients with stroke were identified. Using available summary data from the 10 studies that employed a common immunoassay platform, we utilized random effects linear mixed modeling and weighted averages to create a phasic model of serum/plasma NfL values in distinct time periods of acute stroke. Weighted averages show that blood NfL levels vary significantly across three distinct temporal epochs of acute (0–7 days), subacute (9–90 days), and chronic (>90 days) stroke with a steep peak in the early subacute period between 14 and 21 days after stroke. Blood NfL values can function as a diagnostic biomarker in distinguishing acute ischemic stroke from transient ischemic attack as well as amongst other cerebrovascular subtypes. Release of NfL into the bloodstream after stroke follows a distinct temporal dynamic that lags several weeks behind stroke onset and reliably associates with a stroke diagnosis despite some variability based on stroke subtype and severity. Identification of these temporal dynamics and the contribution of co- existent cerebrovascular disease states can improve the value of NfL as a stroke biomarker.

The Association of Serum Neurofilament Light Chain and Acute Ischaemic Stroke Is Influenced by Effective Revascularization

Objective

To explore associations of serum neurofilament light chain (sNfL) at admission with clinical deficits and the long-term prognosis of acute ischaemic stroke (AIS).

Methods

We recruited 110 AIS patients with serum sampled at hospital arrival. The concentrations of sNfL were detected by a Simoa HD-1 analyser. We first investigated the determinants of sNfL levels at admission within the study population. Associations of sNfL levels with National Institutes of Health Stroke Scale (NIHSS) scores and modified Rankin Scale (mRS) scores were then tested. We further divided the patients into revascularized and nonrevascularized groups, and the associations of sNfL levels with NIHSS and mRS scores were assessed in these subgroups.

Results

Age, sex, stroke history, and the time between the onset of illness and arrival at the hospital were independent influencing factors of sNfL levels within the study population. The sNfL levels at admission were correlated with the NIHSS scores 7 days after stroke (p = 0.004) across all subjects but showed no correlation with the NIHSS scores at admission (p = 0.293) or the mRS scores 6 months after stroke (p = 0.065). Further analysis revealed that in the nonrevascularized group of AIS patients, the sNfL levels at admission were positively correlated with NIHSS scores (NIHSS at admission, p = 0.005; NIHSS 7 days after stroke, p = 0.003) and negatively correlated with mRS scores (p = 0.011).

Conclusion

sNfL levels at admission could be a potential biomarker for predicting clinical deficits and prognosis in the natural course of AIS.

Diagnostic and Prognostic Blood Biomarkers in Transient Ischemic Attack and Minor Ischemic Stroke: An Up-To-Date Narrative Review

INTRODUCTION

Early diagnosis and correct risk stratification in patients with transient ischemic attack (TIA) and minor ischemic stroke (MIS) is crucial for the high rate of subsequent disabling stroke. Although highly improved, diagnosis and prognostication of TIA/MIS patients remain still based on clinical and neuroimaging findings, with some inter-rater variability even among trained neurologists.

OBJECTIVES

To provide an up-to-date overview of diagnostic and prognostic blood biomarkers in TIA and MIS patients.

MATERIAL AND METHODS

We performed a bibliographic search on PubMed database with last access on July 10^th 2021. More than 680 articles were screened and we finally included only primary studies on blood biomarkers.

RESULTS

In a narrative fashion, we discussed about blood biomarkers investigated in TIA/MIS patients, including inflammatory, thrombosis, neuronal injury and cardiac analytes, antibodies and microRNAs. Other soluble molecules have been demonstrated to predict the risk of recurrent cerebrovascular events or treatment response in these patients. A rapid point of care assay, combining the determination of different biomarkers, has been developed to improve triage recognition of acute cerebrovascular accidents.

CONCLUSIONS

The implementation of blood biomarkers in the clinical management of TIA/MIS could ameliorate urgent identification, risk stratification and individual treatment choice. Large prospective and longitudinal studies, adopting standardized sampling and analytic procedures, are needed to clarify blood biomarkers kinetic and their relationship with TIA and minor stroke etiology.

Newly-identified blood biomarkers of neurological damage are correlated with infarct volume in patients with acute ischemic stroke

Our group recently performed a genome-wide informatic analysis that highlighted eight brain-enriched proteins with strong potential to serve as blood biomarkers of neurological injury (GFAP, MBP, β-synuclein, OPALIN, MT-3, SNAP-25, KIF5A, MOBP), including six that have yet to be widely investigated. In this study, our aim was to determine whether the circulating levels of these proteins could be used to approximate the extent of neural tissue damage in ischemic stroke. To address this aim, blood was collected from 43 ischemic stroke patients immediately upon hospital admission. The serum levels of the eight candidate proteins were measured via ELISA, infarct volume was assessed via manual tracing of neuroradiological images, and correlational analysis was performed to examine potential associative relationships. The serum levels of all eight proteins exhibited positive correlations with infarct volume, however the strongest associations were observed in a subset of four proteins known to originate from neurons specifically (MT-3, SNAP-25, KIF5A, β-synuclein). Combining the serum levels of these neuron-originating proteins using principal components analysis produced a single composite value that was more strongly correlated with infarct volume than the levels of any single protein considered in isolation (r = 0.48, p < 0.001). Measures of these proteins could potentially be used to provide a minimally invasive approximation of lesion size when advanced imaging techniques are not available, or when imaging results are inconclusive.

Extracellular fluid, cerebrospinal fluid and plasma biomarkers of axonal and neuronal injury following intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) is the most devastating form of stroke. To refine treatments, improved understanding of the secondary injury processes is needed. We compared energy metabolic, amyloid and neuroaxonal injury biomarkers in extracellular fluid (ECF) from the perihemorrhagic zone (PHZ) and non-injured (NCX) brain tissue, cerebrospinal fluid (CSF) and plasma. Patients (n = 11; age 61 ± 10 years) undergoing ICH surgery received two microdialysis (MD) catheters, one in PHZ, and one in NCX. ECF was analysed at three time intervals within the first 60 h post- surgery, as were CSF and plasma samples. Amyloid-beta (Aβ) 40 and 42, microtubule associated protein tau (tau), and neurofilament-light (NF-L) were analysed using Single molecule array (Simoa) technology. Median biomarker concentrations were lowest in plasma, higher in ECF and highest in CSF. Biomarker levels varied over time, with different dynamics in the three fluid compartments. In the PHZ, ECF levels of Aβ40 were lower, and tau higher when compared to the NCX. Altered levels of Aβ peptides, NF-L and tau may reflect brain tissue injury following ICH surgery. However, the dynamics of biomarker levels in the different fluid compartments should be considered in the study of pathophysiology or biomarkers in ICH patients.

The Cytoskeletal Elements MAP2 and NF-L Show Substantial Alterations in Different Stroke Models While Elevated Serum Levels Highlight Especially MAP2 as a Sensitive Biomarker in Stroke Patients

In the setting of ischemic stroke, the neurofilament subunit NF-L and the microtubule-associated protein MAP2 have proven to be exceptionally ischemia-sensitive elements of the neuronal cytoskeleton. Since alterations of the cytoskeleton have been linked to the transition from reversible to irreversible tissue damage, the present study investigates underlying time- and region-specific alterations of NF-L and MAP2 in different animal models of focal cerebral ischemia. Although NF-L is increasingly established as a clinical stroke biomarker, MAP2 serum measurements after stroke are still lacking. Therefore, the present study further compares serum levels of MAP2 with NF-L in stroke patients. In the applied animal models, MAP2-related immunofluorescence intensities were decreased in ischemic areas, whereas the abundance of NF-L degradation products accounted for an increase of NF-L-related immunofluorescence intensity. Accordingly, Western blot analyses of ischemic areas revealed decreased protein levels of both MAP2 and NF-L. The cytoskeletal alterations are further reflected at an ultrastructural level as indicated by a significant reduction of detectable neurofilaments in cortical axons of ischemia-affected areas. Moreover, atomic force microscopy measurements confirmed altered mechanical properties as indicated by a decreased elastic strength in ischemia-affected tissue. In addition to the results from the animal models, stroke patients exhibited significantly elevated serum levels of MAP2, which increased with infarct size, whereas serum levels of NF-L did not differ significantly. Thus, MAP2 appears to be a more sensitive stroke biomarker than NF-L, especially for early neuronal damage. This perspective is strengthened by the results from the animal models, showing MAP2-related alterations at earlier time points compared to NF-L. The profound ischemia-induced alterations further qualify both cytoskeletal elements as promising targets for neuroprotective therapies.

Plasma neurofilament light predicts mortality in patients with stroke

Given the heterogeneity of stroke brain injury, there is a clear need for a biomarker that determines the degree of neuroaxonal injury across stroke types. We evaluated whether blood neurofilament light (NFL) would fulfill this purpose for patients with acute cerebral infarction (ACI; N = 227), aneurysmal subarachnoid hemorrhage (aSAH; N = 58), or nontraumatic intracerebral hemorrhage (ICH; N = 29). We additionally validated our findings in two independent cohorts of patients with ICH (N = 96 and N = 54) given the scarcity of blood biomarker studies for this deadliest stroke type. Compared to healthy individuals (N = 79 and N = 48 for the discovery and validation cohorts, respectively), NFL was higher for all stroke types. NFL associated with radiographic markers of brain tissue damage. It correlated with the extent of early ischemic injury in patients with ACI, hemorrhage severity in patients with aSAH, and intracranial hemorrhage volume in patients with ICH. In all patients, NFL independently correlated with scores from the NIH Stroke Scale, the modified Rankin Scale, and the Mini-Mental State Examination at blood draw, which respectively assess neurological, functional, and cognitive status. Furthermore, higher NFL concentrations independently associated with 3- or 6-month functional disability and higher all-cause mortality. These data support NFL as a uniform method to estimate neuroaxonal injury and forecast mortality regardless of stroke mechanism. As a prognostic biomarker, blood NFL has the potential to assist with planning supportive and rehabilitation services and improving clinical trial efficiency for stroke therapeutics and devices.

Tau, S100B and NSE as Blood Biomarkers in Acute Cerebrovascular Events

BACKGROUND/AIM

We aimed to analyze the diagnostic value of total tau (T-tau), S-100 calcium-binding protein B (S100B) and neuron-specific enolase (NSE) as blood-based biomarkers in acute ischemic stroke (AIS) or transient ischemic attack (TIA), and their correlation with symptom severity, infarct size, etiology and outcome.

PATIENTS AND METHODS

A total of 102 patients with stroke and 35 with TIA were analyzed. Subacute (63.8±50.1 h) plasma T-tau was measured with the single-molecule array (Simoa) method and NSE and S100B were evaluated for comparison. We evaluated biomarkers associations with: (i) diagnosis of AIS or TIA, (ii) cerebral infarction volume in the brain computed tomography, (iii) stroke etiology, (iv) clinical stroke severity and (iv) functional outcome after three months.

RESULTS

T-tau was higher in patients with stroke [1.0 pg/ml (IQR=0.3-2.2)] than with TIA [0.5 pg/ml (IQR=0.2-1.0), p=0.02]. The levels of S100B were also increased in stroke [0.082 μg/l (IQR=0.049-0.157)] patients compared to TIA patients [0.045 μg/l (IQR=0.03-0.073), p<0.001]. However, when the results were adjusted for confounders, significance was lost. Serum levels of NSE among patients with AIS [11.85 μg/l (IQR=9.30-16.14)] compared to those with TIA [10.96 μg/l (IQR=7.98-15.33), p=0.30] were equal. T-tau and S100B concentrations significantly correlated with cerebral infarction volume (r=0.412, p<0.001) and (r=0.597, p<0.001), also after corrections (p<0.001). mRS scores at three-month follow-up correlated with T-tau (r=0.248, p=0.016) and S100B concentrations (r=0.205, p=0.045).

CONCLUSION

For the diagnosis of TIA vs. AIS, blood T-tau and S100B concentrations discriminated only modestly. Additionally, groups were not separable after measuring of T-tau and S100B levels in the blood. T-tau and S100B concentrations correlated with the infarct size, but were not alone predictive for functional outcome at 3 months.

Plasma neurofilament light chain levels predict improvement in late phase after stroke

BACKGROUND AND PURPOSE

Although functional recovery is most pronounced in the first 6 months after stroke, improvement is possible also in the late phase. The value of plasma neurofilament light chain (NfL), a biomarker of axonal injury and secondary neurodegeneration, was explored for the prediction of functional improvement in the late phase after stroke.

METHODS

Baseline plasma NfL levels were measured in 115 participants of a trial on the efficacy of multimodal rehabilitation in the late phase after stroke. The association between NfL levels, impairment in balance, gait and cognitive domains, and improvement 3 and 9 months later was determined.

RESULTS

Plasma NfL levels were associated with the degree of impairment in all three domains. Individuals with meaningful improvement in balance and gait capacity had higher plasma NfL levels compared with non-improvers (p = 0.001 and p = 0.018, respectively). Higher NfL levels were associated with improvement in balance (odds ratio [OR] 2.34, 95% confidence interval [CI] 1.35-4.27, p = 0.004) and gait (OR 2.27, 95% CI 1.25-4.32, p = 0.009). Elevated plasma NfL levels showed a positive predictive value for cognitive improvement, and this effect was specific for the intervention targeting the cognitive domain. The association of NfL levels with cognitive improvement withstood correction for baseline impairment, age and total years of schooling (OR 7.54, 95% CI 1.52-45.66, p = 0.018).

CONCLUSIONS

In addition to its established role as a biomarker in the acute phase, elevated circulating NfL levels may predict functional improvement in the late phase after stroke. Our results should prompt further studies into the use of plasma NfL as a biomarker in the late phase after stroke.

Genetic inactivation of RIP1 kinase activity in rats protects against ischemic brain injury

RIP1 kinase-mediated inflammatory and cell death pathways have been implicated in the pathology of acute and chronic disorders of the nervous system. Here, we describe a novel animal model of RIP1 kinase deficiency, generated by knock-in of the kinase-inactivating RIP1(D138N) mutation in rats. Homozygous RIP1 kinase-dead (KD) rats had normal development, reproduction and did not show any gross phenotypes at baseline. However, cells derived from RIP1 KD rats displayed resistance to necroptotic cell death. In addition, RIP1 KD rats were resistant to TNF-induced systemic shock. We studied the utility of RIP1 KD rats for neurological disorders by testing the efficacy of the genetic inactivation in the transient middle cerebral artery occlusion/reperfusion model of brain injury. RIP1 KD rats were protected in this model in a battery of behavioral, imaging, and histopathological endpoints. In addition, RIP1 KD rats had reduced inflammation and accumulation of neuronal injury biomarkers. Unbiased proteomics in the plasma identified additional changes that were ameliorated by RIP1 genetic inactivation. Together these data highlight the utility of the RIP1 KD rats for target validation and biomarker studies for neurological disorders.

Plasma neurofilament light chain is associated with mortality after spontaneous intracerebral hemorrhage

Background Neurofilament light chain (NfL) is a neuron-specific biomarker with prognostic ability in several types of central nervous system injuries. This study investigates if plasma NfL (pNfL) is elevated early after spontaneous intracerebral hemorrhage (ICH) and whether such elevation reflects disease severity and day-30 outcome. Methods pNfL was quantified by single molecule array analysis in 103 reference subjects (RS) and in samples from 37 patients with ICH obtained on admission to hospital and at 24-h follow-up. The primary outcome was day-30 mortality. Clinical status on admission was evaluated by standardized scoring systems. Results Median pNfL among RS was 9.6 (interquartile range [IQR] 6.2) pg/mL. Upon admission, ICH patients had pNfL of 19.8 (IQR 30.7) pg/mL increasing to 35.9 (IQR 44.5) pg/mL at 24 h (all, p < 0.001). On admission, pNfL was higher among ICH non-survivors than survivors (119.2 [IQR 152.6] pg/mL vs. 15.7 [IQR 19.6] pg/mL, p < 0.01) and this difference was observed also on 24 h follow-up (195.1 [IQR 73.9] pg/mL vs. 31.3 [IQR 27.8] pg/mL, p < 0.01). The area under the receiver operating characteristic curve (ROC AUC) for discrimination of day-30 mortality was significant on admission (AUC = 0.83, 95% confidence interval [CI]: 0.56-1.0) and increased on 24-h follow-up (AUC = 0.93, 95% CI: 0.84-1.0). The odds ratio (OR) for death, by each quartile increase in pNfL was significant both on admission (OR = 4.52, 95% CI: 1.32-15.48) and after 24-h follow-up (OR = 9.52, 95% CI: 1.26-71.74). Conclusions PNfL is associated with day-30 mortality after spontaneous ICH when early after the ictus.

Biological variation of serum neurofilament light chain

OBJECTIVES

The neurofilament light chain (NfL) has emerged as a versatile biomarker for CNS-diseases and is approaching clinical use. The observed changes in NfL levels are frequently of limited magnitude and in order to make clinical decisions based on NfL measurements, it is essential that biological variation is not confused with clinically relevant changes. The present study was designed to evaluate the biological variation of serum NfL.

METHODS

Apparently healthy individuals (n=33) were submitted to blood draws for three days in a row. On the second day, blood draws were performed every third hour for 12 h. NfL was quantified in serum using the Simoa™ HD-1 platform. The within-subject variation (CV_I) and between-subject variation (CV_G) were calculated using linear mixed-effects models.

RESULTS

The overall median value of NfL was 6.3 pg/mL (range 2.1-19.1). The CV_I was 3.1% and the CV_G was 35.6%. An increase in two serial measurements had to exceed 24.3% to be classified as significant at the 95% confidence level. Serum NfL levels remained stable during the day (p=0.40), whereas a minute variation (6.0-6.6 pg/mL) was observed from day-to-day (p=0.02).

CONCLUSIONS

Serum NfL is subject to tight homeostatic regulation with none or neglectable semidiurnal and day-to-day variation, but considerable between-subject variation exists. This emphasizes serum NfL as a well-suited biomarker for disease monitoring, but warrants caution when interpreting NfL levels in relation to reference intervals in a diagnosis setting. Furthermore, NfL's tight regulation requires that the analytical variation is kept at a minimum.

Plasma Neurofilament Light Chain as a Predictive Biomarker for Post-stroke Cognitive Impairment: A Prospective Cohort Study

BACKGROUND

Plasma neurofilaments light chain (pNfL) is a marker of axonal injury. The purpose of this study was to examine the role of pNfL as a predictive biomarker for post-stroke cognitive impairment (PSCI).

METHODS

A prospective single-center observational cohort study was conducted at the General Hospital of Western Theater Command between July 1, 2017 and December 31, 2019. Consecutive patients ≥18 years with first-ever acute ischemic stroke (AIS) of anterior circulation within 24 h of symptom onset were included. PSCI was defined by the Montreal Cognitive Assessment (MOCA) (MOCA < 26) at 90 days after stroke onset.

RESULTS

A total of 1,694 patients [male, 893 (52.70%); median age, 64 (16) years] were enrolled in the cohort analysis, and 1,029 (60.70%) were diagnosed with PSCI. Patients with PSCI had significantly higher pNfL [median (IQR), 55.96 (36.13) vs. 35.73 (17.57) pg/ml; P < 0.001] than Non-PSCI. pNfL was valuable for the prediction of PSCI (OR 1.044, 95% CI 1.038-1.049, P < 0.001) after a logistic regression analysis, even after adjusting for conventional risk factors including age, sex, education level, NIHSS, TOAST classification, and infarction volume (OR 1.041, 95% CI 1.034-1.047, P < 0.001). The optimal cutoff value of the pNfL concentration was 46.12 pg/ml, which yielded a sensitivity of 71.0% and a specificity of 81.5%, with the area under the curve (AUC) at 0.785 (95% CI 0.762-0.808, P < 0.001).

CONCLUSION

This prospective cohort study showed that the pNfL concentration within 48 h of onset was an independent risk factor for PSCI 90 days after an anterior circulation stroke, even after being adjusted for potential influencing factors regarded as clinically relevant.

CLINICAL TRIAL REGISTRATION

www.chictr.org.cn, identifier ChiCTR1800020330.

Serum levels of neurofilament light chain, neuron-specific enolase and S100 calcium-binding protein B during acute bacterial meningitis: a prospective cohort study

PURPOSE

Acute bacterial meningitis (ABM) is a severe disease with an overall poor outcome. Neurofilament (NFL) has shown to be a promising biomarker of neuroaxonal injury in various neurological disorders but has not been investigated in ABM. The aims of this study were (i) to obtain a temporal profile of NFL, neuron-specific enolase (NSE) and S100B in serum during ABM, and (ii) to evaluate their use as biomarkers of severity (Glasgow coma score) and prognosis (Glasgow Outcome Score, GOS and death) in severe ABM.

METHODS

Fifteen adults with severe community-acquired ABM who were admitted to the intensive care unit (ICU) and fulfilled the inclusion criteria were included. Lumbar puncture and blood tests were performed on admission, and blood tests were performed three times daily during the ICU stay. GOS was obtained day 30.

RESULTS

Serum NFL was significantly elevated in ABM patients compared to healthy controls, both at admission and throughout the observation period (p < .01). NFL increased significantly from day 1 up to day 3-6 (p < .0001), peaking day 6. NSE increased significantly from admission up to day 3 (p < .01). At day 5-6, the serum values were not significantly different from values at admission. The highest median serum value of S100B was observed at admission (0.10 µg/L, IQR 0.06-0.14), significantly decreasing day 4-6 (p < .05). None of the investigated biomarkers revealed significant correlation with severity and prognosis.

CONCLUSION

This study represents a first clinical observation of the temporal profile of NFL in serum, in severe ABM. No correlation with severity or prognosis.

Expression and significance of S-100β, CysC and NF-κB in patients with acute cerebral infarction

The present study aimed to explore the expression and significance of S100 protein β (S100β), cystatin C (CysC), and nuclear factor kappa B (NF-κB) in patients with acute cerebral infarction (ACI). ACI patients (n=120) were selected as the experimental group at Xuzhou Central Hospital from August 2016 to August 2018. Ninety healthy subjects who underwent a physical examination at Xuzhou Central Hospital during the same period were selected as the control group. The expression levels of S-100β, CysC and NF-κB were compared between the two groups. Serum S-100β, CysC and NF-κB levels were compared between ACI patients with different degree of nervous functional defects, different infarct size and different prognosis. ROC curve analysis was used for the diagnosis of ACI by serum S-100β, CysC and NF-κB levels. Serum S-100β, CysC and NF-κB levels in the experimental group were higher than those in the control group (P<0.05). The levels of serum S-100β, CysC and NF-κB in patients with different neurological deficits were significantly different. The levels of serum S-100β, CysC and NF-κB in the severe and medium type infarction group were significantly higher than those in the mild type infarction group (both P<0.05). The levels of serum S-100β, CysC and NF-κB in the severe type infarction group were higher than those in the medium type infarction group (P<0.05). There were significant differences in serum S-100β, CysC and NF-κB levels in patients with different infarct sizes. The levels of serum S-100β, CysC and NF-κB in patients with large and medium size infarction were higher than those in the small size infarction group (both P<0.05). The levels of serum S-100β, CysC and NF-κB in patients with large size infarction were higher than those in patients with medium size infarction (P<0.05). Serum S-100β, CysC and NF-κB levels in patients of the worsening group were significantly higher than those in patients of the non-worsening group. The levels of S-100β, CysC, NF-κB in ACI patients were significantly higher than those in healthy subjects. Increased levels of S-100β, CysC and NF-κB can be used as ideal indexes for diagnosing cerebral infarction and studying the condition.

Acute ischemic stroke biomarkers: a new era with diagnostic promise?

Stroke is considered as the first cause of neurological dysfunction and second cause of death worldwide. Recombinant tissue plasminogen activator is the only chemical treatment for ischemic stroke approved by the US Food and Drug Administration. It was the only standard of care for a long time with a very narrow therapeutic window, which usually ranges from 3 to 4.5 h of stroke onset; until 2015, when multiple trials demonstrated the benefit of mechanical thrombectomy during the first 6 h. In addition, recent trials showed that mechanical thrombectomy can be beneficial up to 24 h if the patients meet certain criteria including the presence of magnetic resonance imaging/computed tomography perfusion mismatch, which allows better selectivity and higher recruitment of eligible stroke patients. However, magnetic resonance imaging/computed tomography perfusion is not available in all stroke centers. Hence, physicians need other easy and available diagnostic tools to select stroke patients eligible for mechanical thrombectomy. Moreover, stroke management is still challenging for physicians, particularly those dealing with patients with "wake-up" stroke. The resulting brain tissue damage of ischemic stroke and the subsequent pathological processes are mediated by multiple molecular pathways that are modulated by inflammatory markers and post-transcriptional activity. A considerable number of published works suggest the role of inflammatory and cardiac brain-derived biomarkers (serum matrix metalloproteinase, thioredoxin, neuronal and glial markers, and troponin proteins) as well as different biomarkers including the emerging roles of microRNAs. In this review, we assess the accumulating evidence regarding the current status of acute ischemic stroke diagnostic biomarkers that could guide physicians for better management of stroke patients. Our review could give an insight into the roles of the different emerging markers and microRNAs that can be of high diagnostic value in patients with stroke. In fact, the field of stroke research, similar to the field of traumatic brain injury, is in immense need for novel biomarkers that can stratify diagnosis, prognosis, and therapy.

Blood neurofilament light: a critical review of its application to neurologic disease

Neuronal injury is a universal event that occurs in disease processes that affect both the central and peripheral nervous systems. A blood biomarker linked to neuronal injury would provide a critical measure to understand and treat neurologic diseases. Neurofilament light chain (NfL), a cytoskeletal protein expressed only in neurons, has emerged as such a biomarker. With the ability to quantify neuronal damage in blood, NfL is being applied to a wide range of neurologic conditions to investigate and monitor disease including assessment of treatment efficacy. Blood NfL is not specific for one disease and its release can also be induced by physiological processes. Longitudinal studies in multiple sclerosis, traumatic brain injury, and stroke show accumulation of NfL over days followed by elevated levels over months. Therefore, it may be hard to determine with a single measurement when the peak of NfL is reached and when the levels are normalized. Nonetheless, measurement of blood NfL provides a new blood biomarker for neurologic diseases overcoming the invasiveness of CSF sampling that restricted NfL clinical application. In this review, we examine the use of blood NfL as a biologic test for neurologic disease.

Acute Neurofilament Light Chain Plasma Levels Correlate With Stroke Severity and Clinical Outcome in Ischemic Stroke Patients

Background: Ischemic stroke causes increased blood–brain barrier permeability and release of markers of axonal damage and inflammation. To investigate diagnostic and prognostic roles of neurofilament light chain (NF-L), we assessed levels of NF-L, S100B, interleukin-6 (IL-6), E-selectin, vascular endothelial growth factor-A (VEGF-A), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) in patients with acute ischemic stroke or transient ischemic attack (TIA) and healthy controls.

Methods: We studied neurofilament (NF) expression in 2 cases of human postmortem ischemic stroke, representing infarcts aged 3- to >7-days. In a prospective study, we measured plasma NF-L and inflammatory markers <8 h of symptom onset and at 72 h in acute ischemic stroke (n = 31), TIA (n = 9), and healthy controls (n = 29). We assessed whether NF-L, S100B, and IL-6 were associated with clinical severity on admission (Scandinavian Stroke Scale, SSS), diagnosis of ischemic stroke vs. TIA, and functional outcome at 3 months (modified Rankin Scale, mRS).

Results: NF expression increased in ischemic neurons and in the infarcted brain parenchyma after stroke. Plasma NF-L levels were higher in stroke patients than in TIA patients and healthy controls, but IL-6 levels were similar. Higher acute NF-L levels were associated with lower SSS scores at admission and higher mRS scores at 3 months. No correlation was observed between NF-L and S100B, NF-L and IL-6, nor between S100B or IL-6 and SSS or mRS. Compared to controls, stroke patients had significantly higher VEGF-A and VCAM-1 at <8 h that remained elevated at 72 h, with significantly higher VEGF-A at <8 h; ICAM-1 was significantly increased at <8 h, while S100B and E-selectin were unchanged.

Conclusions: Plasma NF-L levels, but not IL-6 and S100B, were significant predictors of clinical severity on admission and functional outcome at 3 months. Plasma NF-L is a promising biomarker of functional outcome after ischemic stroke.

Serum neurofilament light chain in FTLD: association with C9orf72, clinical phenotype, and prognosis

Objective

The aim of the present study was to compare the levels of serum neurofilament light chain (sNfL) in frontotemporal lobar degeneration (FTLD) patients of different clinical subtypes (bvFTD, PPA, and FTLD‐MND) and with or without the C9orf72 repeat expansion, and to correlate sNfL levels to disease progression, assessed by the brain atrophy rate and survival time.

Methods

The sNfL levels were determined from 78 FTLD patients (C9orf72 repeat expansion carriers [n = 26] and non‐carriers [n = 52]) with Single Molecule Array (SIMOA). The progression of brain atrophy was evaluated using repeated T1‐weighted MRI scans and the survival time from medical records.

Results

In the total FTLD cohort, sNfL levels were significantly higher in C9orf72 repeat expansion carriers compared to non‐carriers. Considering clinical phenotypes, sNfL levels were higher in the C9orf72 repeat expansion carriers than in the non‐carriers in bvFTD and PPA groups. Furthermore, sNfL levels were the highest in the FTLD‐MND group (median 105 pg/mL) and the lowest in the bvFTD group (median 27 pg/mL). Higher sNfL levels significantly correlated with frontal cortical atrophy rate and subcortical grey matter atrophy rate. The higher sNfL levels also associated with shorter survival time.

Interpretation

Our results indicate that the C9orf72 repeat expansion carriers show elevated sNFL levels compared to non‐carriers and that the levels differ among different clinical phenotypes of FTLD. Higher sNfL levels correlated with a shorter survival time and cortical and subcortical atrophy rates. Thus, sNfL could prove as a potential prognostic biomarker in FTLD.

Association of serum biomarker neurofilament light concentration with post-stroke depression: A preliminary study

OBJECTIVE

To investigate serum neurofilament light (sNfL) levels in acute ischemic stroke and to assess whether sNfL are related to the severity of disease and a potential prognostic marker of post-stroke depression (PSD) during a 3-month follow-up period.

METHODS

This was a single-center prospective cohort study. The sNfL concentration was measured in baseline samples using the Simoa platform- Single Molecule Array technology. A psychiatrist administered the Structural Clinical Interview for Diagnostic and Statistical Manual IV to all patients and made a diagnosis of PSD 3 months after stroke. The logistic regression was used to examine the association between sNfL and PSD.

RESULTS

In total, 236 ischemic stroke cases were included and finished the follow-up. In the follow-up, 55 patients were defined as PSD, thus the incidence rate was 23.3% (95% confidence intervals [CI]: 17.9%-28.7%). Significant differences were observed between the sNfL levels in patients with PSD (124.8 pg/ml [interquartile range {IQR}: 59.6-159.2]) and in patients without PSD (35.9 pg/ml [IQR: 18.2-60.4]) levels (P < 0.001). After adjusting for age, family history of depression, marital status, National Institutes of Health and Stroke Scale score, C-reactive protein and homocysteine levels, sNfL levels independently predicted the development of post-stroke depression. The crude and adjusted odds ratios [OR] (and 95%CI) of PSD associated with an IQR increase for sNfL were 3.38(2.29, 4.98) and 2.65(1.59, 4.04), respectively. According to receiver operating characteristic curves (ROC) curves, the cut-off value of sNfL to predict PSD was 111.4 pg/ml with an area under the curve (AUC) of 0.84(95% CI, 0.78-0.90) and with the highest sensitivity (61.8%) and specificity (95.4%).

CONCLUSIONS

In this study, elevated level of sNfL is associated with higher risk of 3-month depression in patients with ischemic stroke and makes early diagnoses of depression. The study needs replication to ensure the validity of our preliminary results.

Diagnosis of ischemic stroke using circulating levels of brain-specific proteins measured via high-sensitivity digital ELISA

Limited lower detection ranges associated with traditional immunoassay techniques have prevented the use of brain-specific proteins as blood biomarkers of stroke in the acute phase of care, as these proteins are often only present in circulation at low concentrations. Digital ELISA is a newly developed technique with allows for quantification of proteins in biofluids with up to 1000 times greater sensitivity than conventional ELISA techniques. The purpose of this study was to determine whether the extended lower limits of detection associated with digital ELISA could enable the use of brain-specific proteins as blood biomarkers of ischemic stroke during triage. Blood was sampled from ischemic stroke patients (n = 14) at emergency department admission, as well as from neurologically normal controls matched in terms of risk factors for cardiovascular disease (n = 33). Plasma levels of two brain-specific axonal proteins, neurofilament light chain (NfL) and tau, were measured via digital ELISA, and receiver-operating characteristic analysis was used to determine their ability to discriminate between groups. Plasma levels of NfL and tau were both significantly elevated in stroke patients versus controls, and could respectively discriminate between groups with 92.9% sensitivity / 84.9% specificity, and 85.7% sensitivity / 54.6% specificity. Furthermore, adjustment of measured NfL and Tau levels according to the lower-limits of detection associated with commercially-available conventional ELISA assays resulted in a dramatic and statistically significant decrease in diagnostic performance. Collectively, our results suggest that the increased analytical sensitivity of digital ELISA could enable the use of brain-specific proteins as blood biomarkers of ischemic stroke during triage.

Serum Neurofilament Light Chain as a Predictive Biomarker for Ischemic Stroke Outcome: A Systematic Review and Meta-analysis

BACKGROUND

Stroke is the leading cause of death and long-term disability worldwide. The purpose of the study is to examine the role of serum neurofilament light chain (sNfL) as a predictive biomarker for ischemic stroke outcome.

METHODS

We searched PubMed, Web of Science, and EMBASE for potential studies published in English previous to November 15, 2019. Two independent reviewers screened the search results for studies reporting the correlation between sNfL and stroke outcome in ischemic stroke or transient ischemic attack patients. The Newcastle-Ottawa Scale was adopted to evaluate the quality of the included studies. The pooled odds ratio (OR) of sNfL for stroke functional outcome was calculated with the Comprehensive Meta-Analysis software, version 2. Heterogeneity and publication bias were assessed with the I² test and funnel plot, respectively.

RESULTS

Seven studies met the inclusion criteria. The qualities of the included studies ranged from moderate to high. Despite of the different methods used to measure infarct volume, 5 of the included studies reported similar results about the association between sNfL and infarct volume. Two studies investigating the relationship between sNfL and recurrent ischemic events both reported positive results. In pooled analysis with the adjusted odds ratios (Ors) from multivariate regression models, the meta-analysis reached a pooled adjusted OR = 1.71 [95% CI: 1.17-4.29], which represented that the patients with higher sNfL, compared with lower sNfL patients, had a 1.71 times higher risk of poor functional outcome during follow-up. Both meta-regression and subgroup analysis found that sampling time was an important source of heterogeneity. Based on funnel plot and Egger's test, we did not detect obvious publication bias in our study.

CONCLUSIONS

The sNfL was a promising predictive biomarker for ischemic stroke outcome, and blood sampling time was of great importance in the correlation. The temporal change of sNfL after stroke deserves further exploration in large longitudinal studies and a standardized procedure is warranted.

Penetrating Traumatic Brain Injury Triggers Dysregulation of Cathepsin B Protein Levels Independent of Cysteine Protease Activity in Brain and Cerebral Spinal Fluid

Cathepsin B (CatB), a lysosomal cysteine protease, is important to brain function and may have dual utility as a peripheral biomarker of moderate-severe traumatic brain injury (TBI). The present study determined levels of pro- and mature (mat) CatB protein as well as cysteine protease activity within the frontal cortex (FC; proximal injury site), hippocampus (HC; distal injury site), and cerebral spinal fluid (CSF) collected 1-7 days after craniotomy and penetrating ballistic-like brain injury (PBBI) in rats. Values were compared with naïve controls. Further, the utility of CatB protein as a translational biomarker was determined in CSF derived from patients with severe TBI. Craniotomy increased matCatB levels in the FC and HC, and led to elevation of HC activity at day 7. PBBI caused an even greater elevation in matCatB within the FC and HC within 3-7 days. After PBBI, cysteine protease activity peaked at 3 days in the FC and was elevated at 1 day and 7 days, but not 3 days, in the HC. In rat CSF, proCatB, matCatB, and cysteine protease activity peaked at 3 days after craniotomy and PBBI. Addition of CA-074, a CatB-specific inhibitor, confirmed that protease activity was due to active matCatB in rat brain tissues and CSF at all time-points. In patients, CatB protein was detectable from 6 h through 10 days after TBI. Notably, CatB levels were significantly higher in CSF collected within 3 days after TBI compared with non-TBI controls. Collectively, this work indicates that CatB and its cysteine protease activity may serve as collective molecular signatures of TBI progression that differentially vary within both proximal and distal brain regions. CatB and its protease activity may have utility as a surrogate, translational biomarker of acute-subacute TBI.

Neurofilaments in disease: what do we know?

Neurofilaments are proteins selectively expressed in the cytoskeleton of neurons, and increased levels are a marker of damage. Elevated neurofilament levels can serve as a marker of ongoing disease activity as well as a tool to measure response to therapeutic intervention. The potential utility of neurofilaments has drastically increased as recent advances have made it possible to measure levels in both the cerebrospinal fluid and blood. There is mounting evidence that neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (NfH) are abnormal in a host of neurodegenerative diseases. In this review we examine how both of these proteins behave across diseases and what we know about how these biomarkers relate to in vivo white matter pathology and each other.

Neurofilaments: The C-Reactive Protein of Neurology

Neurofilaments (NFs) are quickly becoming the biomarkers of choice in the field of neurology, suggesting their use as an unspecific screening marker, much like the use of elevated plasma C-reactive protein (CRP) in other fields. With sensitive techniques being readily available, evidence is growing regarding the diagnostic and prognostic value of NFs in many neurological disorders. Here, we review the latest literature on the structure and function of NFs and report the strengths and pitfalls of NFs as markers of neurodegeneration in the context of neurological diseases of the central and peripheral nervous systems.

Serum Neurofilament Light Predicts Severity and Prognosis in Patients with Ischemic Stroke

Serum neurofilaments are markers of axonal injury. We investigated whether serum neurofilament light (sNfL) is a potential prognostic marker of functional outcome in Chinese patients with acute ischemic stroke (AIS). From May 2015 to December 2018, consecutive patients with AIS from the Department of Neurology of the Second Hospital of Jilin University were included. sNfL concentration was tested at baseline, and stroke severity was analyzed at admission using the NIHSS score. Functional outcome was assessed at discharge by the modified Rankin scale (mRS). The sNfL concentration was tested in 343 patients with a median value of 17.8 (IQR, 13.4-25.2) pg/ml. sNfL concentration paralleled lesion size (P = 0.035). At admission, 174 patients were defined as moderate-to-high stroke (NIHSS ≥ 5); the sNfL concentration in those patients were higher than that observed in patients with minor clinical severity [21.2 (IQR, 15.1-31.7) vs. 14.9 (11.8-19.4) pg/ml, P < 0.001]. For each 1 quartile increase of sNfL concentration, the unadjusted and adjusted risk of moderate-to-high stroke increased by 202% (with the OR of 3.04 (95% CI 2.15-4.32), P < 0.001) and 102% [2.02 (1.10-3.16), P = 0.001), respectively. At discharge, 85 patients (24.8%) had poor functional outcome (mRS, 3-6); the sNfL concentration in those patients were higher than that observed in patients with good outcome [24.1 (IQR, 18.8-33.9) vs. 15.7 (11.9-21.8) pg/ml, P < 0.001]. For each 1 quartile increase of sNfL concentration, the unadjusted and adjusted risk of poor outcome increased by 236% [with the OR of 3.36 (95% CI 2.23-5.06), P < 0.001] and 102% [2.29 (1.37-3.82), P < 0.001], respectively. The results show sNfL is meaningful blood biomarker to monitor stroke severity and functional outcome in ischemic stroke, suggesting that sNfL may play a role in stroke progression.