CSF neurofilament light chain and phosphorylated tau 181 predict disease progression in PSP

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.

Association of Neurofilament Light Chain, [18F]PI-2620 Tau-PET, TSPO-PET, and Clinical Progression in Patients With β-Amyloid-Negative CBS

BACKGROUND AND OBJECTIVES

Corticobasal syndrome (CBS) with underlying 4-repeat tauopathy is a progressive neurodegenerative disease characterized by declining cognitive and motor functions. Biomarkers for assessing pathologic brain changes in CBS including tau-PET, 18 kDa translocator protein (TSPO)-PET, structural MRI, neurofilament light chain (NfL), or glial fibrillary acidic protein (GFAP) have recently been evaluated for differential diagnosis and disease staging, yet their association with disease trajectories remains unclear. Therefore, we performed a head-to-head comparison of neuroimaging (tau-PET, TSPO-PET, structural MRI) and plasma biomarkers (NfL, GFAP) as prognostic tools for longitudinal clinical trajectories in β-amyloid (Aβ)-negative CBS.

METHODS

We included patients with clinically diagnosed Aβ-negative CBS with clinical follow-up data who underwent baseline structural MRI and plasma-NfL analysis for assessing neurodegeneration, [18F]PI-2620-PET for assessing tau pathology, [18F]GE-180-PET for assessing microglia activation, and plasma-GFAP analysis for assessing astrocytosis. To quantify tau and microglia load, we assessed summary scores of whole-brain, cortical, and subcortical PET signal. For structural MRI analysis, we quantified subcortical and cortical gray matter volume. Plasma NfL and GFAP values were assessed using Simoa-based immunoassays. Symptom progression was determined using a battery of cognitive and motor tests (i.e., Progressive Supranuclear Palsy Rating Scale [PSPRS]). Using linear mixed models, we tested whether the assessed biomarkers at baseline were associated with faster symptom progression over time (i.e., time × biomarker interaction).

RESULTS

Overall, 21 patients with Aβ-negative CBS with ∼2-year clinical follow-up data were included. Patients with CBS with more widespread global tau-PET signal showed faster clinical progression (PSPRS: B/SE = 0.001/0.0005, p = 0.025), driven by cortical rather than subcortical tau-PET. By contrast, patients with higher global [18F]GE-180-PET readouts showed slower clinical progression (PSPRS: B/SE = -0.056/0.023, p = 0.019). No association was found between gray matter volume and clinical progression. Concerning fluid biomarkers, only higher plasma-NfL (PSPRS: B/SE = 0.176/0.046, p < 0.001) but not GFAP was associated with faster clinical deterioration. In a subsequent sensitivity analysis, we found that tau-PET, TSPO-PET, and plasma-NfL showed significant interaction effects with time on clinical trajectories when tested in the same model.

DISCUSSION

[18F]PI-2620 tau-PET, [18F]GE-180 TSPO-PET, and plasma-NfL show prognostic potential for clinical progression in patients with Aβ-negative CBS with probable 4-repeat tauopathy, which can be useful for clinical decision-making and stratifying patients in clinical trials.

Association of Insulin-like Growth Factor-1 and Neurofilament Light Chain in Patients with Progressive Supranuclear Palsy

Background

Progressive supranuclear palsy (PSP) is the most common primary tauopathy. The definite diagnosis of PSP is established by histopathologic changes in the brain. There are no reliable blood-based biomarkers to aid the diagnosis of this fatal disease at an early stage. Also, the precise etiopathology of PSP and its variants is inadequately understood.

Objective

Blood-based molecules such as neurofilament light chain (NfL) and insulin-like growth factor-1 (IGF-1) are shown as important markers of neurodegenerative and aging processes, respectively. These two biomarkers have not been analyzed simultaneously in PSP patients.

Methods

To address this knowledge gap, 40 PSP patients and equal number of healthy individuals were recruited and serum levels of NfL and IGF-1 were assayed in all the study participants by enzyme-linked immunosorbent assay (ELISA). Motor and nonmotor symptoms were evaluated in PSP patients using various scales/questionnaires. Cardiac autonomic function tests were performed in a subset of patients (n = 27).

Results

A significantly high serum level of NfL (P < 0.01) and a reduced level of IGF-1 (P = 0.02) were observed in PSP patients compared to healthy controls. Besides, a negative correlation (r = -0.54, P < 0.01) between NfL and IGF-1 levels was observed in PSP patients.

Conclusion

The finding of this study reinforces the important role of blood NfL level as a potential biomarker of PSP. Further, the current study provides novel insights into the reciprocal correlation between NfL and IGF-1 in PSP patients. Combined analysis of blood levels of these two functionally relevant markers might be useful in the prediction and diagnosis of PSP.

Unexpected gender differences in progressive supranuclear palsy reveal efficacy for davunetide in women

Progressive supranuclear palsy (PSP) is a pure tauopathy, implicating davunetide, enhancing Tau-microtubule interaction, as an ideal drug candidate. However, pooling patient data irrespective of sex concluded no efficacy. Here, analyzing sex-dependency in a 52 week-long- PSP clinical trial (involving over 200 patients) demonstrated clear baseline differences in brain ventricular volumes, a secondary endpoint. Dramatic baseline ventricular volume-dependent/volume increase correlations were observed in 52-week-placebo-treated females (r = 0.74, P = 2.36-9), whereas davunetide-treated females (like males) revealed no such effects. Assessment of primary endpoints, by the PSP Rating Scale (PSPRS) and markedly more so by the Schwab and England Activities of Daily Living (SEADL) scale, showed significantly faster deterioration in females, starting at trial week 13 (P = 0.01, and correlating with most other endpoints by week 52). Twice daily davunetide treatments slowed female disease progression and revealed significant protection according to the SEADL scale as early as at 39 weeks (P = 0.008), as well as protection of the bulbar and limb motor domains considered by the PSPRS, including speaking and swallowing difficulties caused by brain damage, and deterioration of fine motor skills, respectably (P = 0.01), at 52 weeks. Furthermore, at 52 weeks of trial, the exploratory Geriatric Depression Scale (GDS) significantly correlated with the SEADL scale deterioration in the female placebo group and demonstrated davunetide-mediated protection of females. Female-specific davunetide-mediated protection of ventricular volume corresponded to clinical efficacy. Together with the significantly slower disease progression seen in men, the results reveal sex-based drug efficacy differences, demonstrating the neuroprotective and disease-modifying impact of davunetide treatment for female PSP patients.

Midbrain and pons MRI shape analysis and its clinical and CSF correlates in degenerative parkinsonisms: a pilot study

OBJECTIVES

To conduct brainstem MRI shape analysis across neurodegenerative parkinsonisms and control subjects (CS), along with its association with clinical and cerebrospinal fluid (CSF) correlates.

METHODOLOGY

We collected demographic and clinical variables, performed planimetric and shape MRI analyses, and determined CSF neurofilament-light chain (NfL) levels in 84 participants: 11 CS, 12 with Parkinson's disease (PD), 26 with multiple system atrophy (MSA), 21 with progressive supranuclear palsy (PSP), and 14 with corticobasal degeneration (CBD).

RESULTS

MSA featured the most extensive and significant brainstem shape narrowing (that is, atrophy), mostly in the pons. CBD presented local atrophy in several small areas in the pons and midbrain compared to PD and CS. PSP presented local atrophy in small areas in the posterior and upper midbrain as well as the rostral pons compared to MSA. Our findings of planimetric MRI measurements and CSF NfL levels replicated those from previous literature. Brainstem shape atrophy correlated with worse motor state in all parkinsonisms and with higher NfL levels in MSA, PSP, and PD.

CONCLUSION

Atypical parkinsonisms present different brainstem shape patterns which correlate with clinical severity and neuronal degeneration. In MSA, shape analysis could be further explored as a potential diagnostic biomarker. By contrast, shape analysis appears to have a rather limited discriminant value in PSP.

KEY POINTS

• Atypical parkinsonisms present different brainstem shape patterns. • Shape patterns correlate with clinical severity and neuronal degeneration. • In MSA, shape analysis could be further explored as a potential diagnostic biomarker.

Plasma Biomarkers and Positron Emission Tomography Tau Pathology in Progressive Supranuclear Palsy

BACKGROUND

Development of disease-modifying therapeutic trials of progressive supranuclear palsy (PSP) urges the need for sensitive fluid biomarkers.

OBJECTIVES

The objectives of this study were to explore the utility of plasma biomarkers in the diagnosis, differential diagnosis, and assessment of disease severity, brain atrophy, and tau deposition in PSP.

METHODS

Plasma biomarkers were measured using a single-molecule array in a cohort composed of patients with PSP, Parkinson's disease (PD), multiple system atrophy with predominant parkinsonism (MSA-P), and healthy controls (HCs).

RESULTS

Plasma neurofilament light chain (NfL) outperformed other plasma makers (ie, glial fibrillary acidic protein [GFAP], phosphorylated-tau 181 [p-tau181], amyloid-β 1-40, amyloid-β 1-42) in identifying PSP from HC (area under the curve [AUC] = 0.904) and from MSA-P (AUC = 0.711). Plasma GFAP aided in distinguishing PSP from HC (AUC = 0.774) and from MSA-P (AUC = 0.832). It correlated with brainstem atrophy and higher regional tau accumulation. However, plasma p-tau181 neither helped in diagnosis nor was it associated with clinical or neuroimaging measures.

CONCLUSIONS

Plasma NfL and GFAP showed different values in differentiating PSP from HC or controls with other forms of neurodegenerative parkinsonism and detecting disease severity, brain atrophy, or tau deposition in PSP. © 2023 International Parkinson and Movement Disorder Society.

CSF1R inhibitors induce a sex-specific resilient microglial phenotype and functional rescue in a tauopathy mouse model

Microglia are central to pathogenesis in many neurological conditions. Drugs targeting colony-stimulating factor-1 receptor (CSF1R) to block microglial proliferation in preclinical disease models have shown mixed outcomes, thus the therapeutic potential of this approach remains unclear. Here, we show that CSF1R inhibitors given by multiple dosing paradigms in the Tg2541 tauopathy mouse model cause a sex-independent reduction in pathogenic tau and reversion of non-microglial gene expression patterns toward a normal wild type signature. Despite greater drug exposure in male mice, only female mice have functional rescue and extended survival. A dose-dependent upregulation of immediate early genes and neurotransmitter dysregulation are observed in the brains of male mice only, indicating that excitotoxicity may preclude functional benefits. Drug-resilient microglia in male mice exhibit morphological and gene expression patterns consistent with increased neuroinflammatory signaling, suggesting a mechanistic basis for sex-specific excitotoxicity. Complete microglial ablation is neither required nor desirable for neuroprotection and therapeutics targeting microglia must consider sex-dependent effects.

Social Cognition in Behavioral Variant Frontotemporal Dementia and Pathological Subtypes: A Narrative Review

Behavioral variant frontotemporal dementia (bvFTD) belongs to the spectrum of frontotemporal lobar degeneration (FTLD) and is characterized by frontal dysfunction with executive deficits and prominent socioemotional impairments. Social cognition, such as emotion processing, theory of mind, and empathy may significantly impact daily behavior in bvFTD. Abnormal protein accumulation of tau or TDP-43 are the main causes of neurodegeneration and cognitive decline. Differential diagnosis is difficult due to the heterogeneous pathology in bvFTD and the high clinicopathological overlap with other FTLD syndromes, especially in late disease stages. Despite recent advances, social cognition in bvFTD has not yet received sufficient attention, nor has its association with underlying pathology. This narrative review evaluates social behavior and social cognition in bvFTD, by relating these symptoms to neural correlates and underlying molecular pathology or genetic subtypes. Negative and positive behavioral symptoms, such as apathy and disinhibition, share similar brain atrophy and reflect social cognition. More complex social cognitive impairments are probably caused by the interference of executive impairments due to increasing neurodegeneration. Evidence suggests that underlying TDP-43 is associated with neuropsychiatric and early social cognitive dysfunction, while patients with underlying tau pathology are marked by strong cognitive dysfunction with increasing social impairments in later stages. Despite many current research gaps and controversies, finding distinct social cognitive markers in association to underlying pathology in bvFTD is essential for validating biomarkers, for clinical trials of novel therapies, and for clinical practice.

Performance of [18F]RO948 PET, MRI and CSF neurofilament light in the differential diagnosis of progressive supranuclear palsy

INTRODUCTION

The diagnosis of progressive supranuclear palsy (PSP) is often challenging since PSP may clinically resemble other neurodegenerative disorders. Recently, the tau PET tracer [¹⁸F]RO948, a potential new biomarker for PSP, was developed. The aim of this study was to determine the ability of three different biomarkers, including [¹⁸F]RO948 PET, to distinguish PSP patients from healthy controls and from patients with α-synucleinopathies.

METHODS

Patients with PSP (n = 23), α-synucleinopathies (n = 47) and healthy controls (n = 61) were included from the BioFINDER-2 study. [¹⁸F]RO948 standardized uptake value ratios (SUVR), magnetic resonance imaging midbrain/pons ratio, and cerebrospinal fluid neurofilament light (NfL) levels were compared between diagnostic groups individually and in combination.

RESULTS

[¹⁸F]RO948 PET SUVR in the globus pallidus, NfL, and midbrain/pons area ratios were all able to differentiate PSP patients from controls and from patients with α-synucleinopathies ([¹⁸F]RO948 [mean ± SD]: controls 1.24 ± 0.22; PSP 1.47 ± 0.4; PD 1.18 ± 0.2; DLB 1.25 ± 0.24, p < 0.05), (NfL pg/mL [mean ± SD]: controls 1055 ± 569; PSP 2197 ± 1010; PD 1038 ± 416; DLB 1548 ± 687, p < 0.001) and (midbrain/pons ratio [mean ± SD]: controls 0.46 ± 0.07; PSP 0.34 ± 0.09; PD 0.43 ± 0.06; DLB 0.40 ± 0.07, p < 0.01). Receiver operating characteristic (ROC) analyses indicated that combining the three biomarkers resulted in the highest area under the ROC values (0.94 [0.88-1.00]) for separating controls from PSP and (0.92 [0.85-0.99]) for separating PSP from α-synucleinopathies.

CONCLUSIONS

All studied biomarkers could individually separate PSP from controls and α-synucleinopathies patients at a group level. The optimal prediction models included NfL and midbrain/pons ratio for separating controls from PSP and all three biomarkers for separating PSP from α-synucleinopathies.

Associations between cerebrospinal fluid markers and cognition in ageing and dementia: A systematic review

A biomarker associated with cognition in neurodegenerative dementias would aid in the early detection of disease progression, complement clinical staging and act as a surrogate endpoint in clinical trials. The current systematic review evaluates the association between cerebrospinal fluid protein markers of synapse loss and neuronal injury and cognition. We performed a systematic search which revealed 67 studies reporting an association between cerebrospinal fluid markers of interest and neuropsychological performance. Despite the substantial heterogeneity between studies, we found some evidence for an association between neurofilament-light and worse cognition in Alzheimer's diseases, frontotemporal dementia and typical cognitive ageing. Moreover, there was an association between cerebrospinal fluid neurogranin and cognition in those with an Alzheimer's-like cerebrospinal fluid biomarker profile. Some evidence was found for cerebrospinal fluid neuronal pentraxin-2 as a correlate of cognition across dementia syndromes. Due to the substantial heterogeneity of the field, no firm conclusions can be drawn from this review. Future research should focus on improving standardization and reporting as well as establishing the importance of novel markers such as neuronal pentraxin-2 and whether such markers can predict longitudinal cognitive decline.

Blood based biomarkers for movement disorders

Movement disorders have been carefully clinically defined, based on clinico-pathological series; however there is often diagnostic and prognostic uncertainty, especially in early stage disease. Blood-based biomarkers for Alzheimer's disease (AD), particularly p-tau181 and p-tau217, may be useful in the movement disorder clinic, especially in identifying corticobasal syndrome due to AD pathology and in identifying Parkinson's disease (PD) patients at high risk for the future development of dementia. Serum or plasma neurofilament light (NfL) may be useful in separating Parkinson's plus syndromes (progressive supranuclear palsy-PSP, multiple system atrophy - MSA, and corticobasal syndrome-CBS) from PD. NfL is also a prognostic biomarker, in that the level of baseline or cross-sectional plasma/serum NfL is associated with a worse prognosis in PD and PSP. The development of protein aggregation assays in cerebrospinal fluid and multiplex assays which can measure 100 s-1000s of proteins in blood will provide new tools and insights for movement disorders for clinicians and researchers. The challenge is in efficiently integrating these tools into clinical practice and multi-modal approaches, where biomarkers are combined with clinical, genetic, and imaging data may guide the future use of these technologies.

Striatal dopaminergic lesions contributed to the disease severity in progressive supranuclear palsy

Background

Reduced dopamine transporter (DAT) binding in the striatum has been reported in patients with progressive supranuclear palsy (PSP). However, the relationship between striatal dopaminergic lesions and the disease severity of PSP remains to be explored.

Objective

To investigate the contributions of striatal dopaminergic lesions to the disease severity of PSP.

Methods

One hundred patients with clinically diagnosed PSP were consecutively enrolled in this study. The disease severity was systemically assessed using the PSP rating scale (PSPrs), and the dopaminergic lesions were assessed using the 11C-N-2-carbomethoxy-3-(4-fluorophenyl)-tropane positron emission tomography (11C-CFT PET) imaging. To explore the correlations between striatal DAT bindings and the disease severity, both the region-wise and voxel-wise analysis were adopted. Partial correlations and multiple linear regressions were performed to investigate the contribution of striatal dopaminergic lesions to the disease severity in PSP.

Results

Sixty-three patients of PSP with Richardson’s syndrome (PSP-RS) and 37 patients with PSP-non-RS were finally included. The disease severity in PSP-RS was much heavier than that in the PSP-non-RS. The DAT bindings in the caudate and anterior putamen correlated significantly with the PSPrs total scores, mainly in the domains of history, mentation, bulbar, and ocular motor symptoms. The striatal DAT bindings (caudate) contributed significantly to the disease severity of PSP, independent of the motor, cognition, emotion and behavioral dysfunctions.

Conclusion

Our study highlighted the independent contribution of striatal dopaminergic lesions to the disease severity in PSP.

Neurofilaments in neurologic disorders and beyond

Many neurologic diseases can initially present as a diagnostic challenge and even when a diagnosis is made, monitoring of disease activity, progression and response to therapy may be limited with existing clinical and paraclinical assessments. As such, the identification of disease specific biomarkers provides a promising avenue by which diseases can be effectively diagnosed, monitored and used as a prognostic indicator for long-term outcomes. Neurofilaments are an integral component of the neuronal cytoskeleton, where assessment of neurofilaments in the blood, cerebrospinal fluid (CSF) and diseased tissue has been shown to have value in providing diagnostic clarity, monitoring disease activity, tracking progression and treatment efficacy, as well as lending prognostic insight into long-term outcomes. As such, this review attempts to provide a glimpse into the structure and function of neurofilaments, their role in various neurologic and non-neurologic disorders, including uncommon conditions with recent knowledge of neurofilament-related pathology, as well as their applicability in future clinical practice.

Sodium selenate as a therapeutic for tauopathies: A hypothesis paper

In a large proportion of individuals with fronto-temporal lobar degeneration (FTLD), the underlying pathology is associated with the misfolding and aggregation of the microtubule associated protein tau (FTLD-tau). With disease progression, widespread protein accumulation throughout cortical and subcortical brain regions may be responsible for neurodegeneration. One of the syndromes of FTLD is the behavioral variant of frontotemporal dementia (bvFTD), in which the underlying pathology is heterogenous, with half of the cases being related to FTLD-tau. Currently, there are no approved disease-modifying treatments for FTLD-tau, therefore representing a major unmet therapeutic need. These descriptive, preliminary findings of the phase 1 open-label trial provide data to support the potential of sodium selenate to halt the cognitive and behavioral decline, as well as to reduce tau levels in a small group of participants with bvFTD (N = 11). All participants were treated with sodium selenate over a period of 52 weeks. Cognition was assessed with the Neuropsychiatry Unit Cognitive Assessment Tool (NUCOG, total scores), social cognition with the Revised Self-Monitoring Scale (RSMS, total scores), behavior with the Cambridge Behavioral Inventory (CBI), and carer burden with the Caregiver Buden Scale (CBS). Fluid biomarker measures include cerebrospinal fluid of total tau (t-tau), phosphorylated tau (p-tau₁₈₁), NfL, p-tau₁₈₁/t-tau, t-tau/Aβ_1–42, and p-tau₁₈₁/Aβ_1–42 levels. After treatment at follow-up, cognition and behavior showed further negative change (based on a reliable change criterion cut-off of annual NUCOG decline) in the “progressors,” but not in the “non-progressors.” “Non-progressors” also showed elevated baseline CSF tau levels and no increase after treatment, indicating underlying tau pathology and a positive response to sodium selenate treatment. Significant changes in MRI were not observed. The findings provide useful information for future clinical trials to systematically assess the disease-modifying treatment effects of sodium selenate in randomized controlled designs for bvFTD and FTLD-tau pathologies.

Alzheimer's disease: a scoping review of biomarker research and development for effective disease diagnosis

INTRODUCTION

Alzheimer's disease (AD) is regarded as the foremost reason for neurodegeneration that prominently affects the geriatric population. Characterized by extracellular accumulation of amyloid-beta (Aβ), intracellular aggregation of hyperphosphorylated tau (p-tau), and neuronal degeneration that causes impairment of memory and cognition. Amyloid/tau/neurodegeneration (ATN) classification is utilized for research purposes and involves amyloid, tau, and neuronal injury staging through MRI, PET scanning, and CSF protein concentration estimations. CSF sampling is invasive, and MRI and PET scanning requires sophisticated radiological facilities which limit its widespread diagnostic use. ATN classification lacks effectiveness in preclinical AD.

AREAS COVERED

This publication intends to collate and review the existing biomarker profile and the current research and development of a new arsenal of biomarkers for AD pathology from different biological samples, microRNA (miRNA), proteomics, metabolomics, artificial intelligence, and machine learning for AD screening, diagnosis, prognosis, and monitoring of AD treatments.

EXPERT OPINION

It is an accepted observation that AD-related pathological changes occur over a long period of time before the first symptoms are observed providing ample opportunity for detection of biological alterations in various biological samples that can aid in early diagnosis and modify treatment outcomes.

Clinical Spectrum of Tauopathies

Tauopathies are both clinical and pathological heterogeneous disorders characterized by neuronal and/or glial accumulation of misfolded tau protein. It is now well understood that every pathologic tauopathy may present with various clinical phenotypes based on the primary site of involvement and the spread and distribution of the pathology in the nervous system making clinicopathological correlation more and more challenging. The clinical spectrum of tauopathies includes syndromes with a strong association with an underlying primary tauopathy, including Richardson syndrome (RS), corticobasal syndrome (CBS), non-fluent agrammatic primary progressive aphasia (nfaPPA)/apraxia of speech, pure akinesia with gait freezing (PAGF), and behavioral variant frontotemporal dementia (bvFTD), or weak association with an underlying primary tauopathy, including Parkinsonian syndrome, late-onset cerebellar ataxia, primary lateral sclerosis, semantic variant PPA (svPPA), and amnestic syndrome. Here, we discuss clinical syndromes associated with various primary tauopathies and their distinguishing clinical features and new biomarkers becoming available to improve in vivo diagnosis. Although the typical phenotypic clinical presentations lead us to suspect specific underlying pathologies, it is still challenging to differentiate pathology accurately based on clinical findings due to large phenotypic overlaps. Larger pathology-confirmed studies to validate the use of different biomarkers and prospective longitudinal cohorts evaluating detailed clinical, biofluid, and imaging protocols in subjects presenting with heterogenous phenotypes reflecting a variety of suspected underlying pathologies are fundamental for a better understanding of the clinicopathological correlations.

Disease modification in Parkinsonism: obstacles and ways forward

To date, the diagnoses of Parkinson syndromes are based on clinical examination. Therefore, these specific diagnoses are made, when the neuropathological process is already advanced. However, disease modification or neuroprotection, is considered to be most effective before marked neurodegeneration has occurred. In recent years, early clinical or prodromal stages of Parkinson syndromes came into focus. Moreover, subtypes of distinct diseases will allow predictions of the individual course of the diseases more precisely. Thereby, patients will be enrolled into clinical trials with more specific disease entities and endpoints. Furthermore, novel fluid and imaging biomarkers that allow biochemical diagnoses are under development. These will lead to earlier diagnoses and earlier therapy in the future as consequence. Furthermore, therapeutic approaches will take the underlying neuropathological process of neurodegenerative Parkinson syndromes more specific into account. Specifically, future therapies will target the aggregation of aggregation-prone proteins such as alpha-synuclein and tau, the degradation of pathological aggregates, and the spreading of pathological protein aggregates throughout the brain. Many of these approaches are already in (pre)clinical development. In addition, anti-inflammatory approaches are in development. Furthermore, drug-repurposing is a feasible approach to shorten the developmental process of new drugs.

Serum-Based Biomarkers in Neurodegeneration and Multiple Sclerosis

Multiple Sclerosis (MS) is a debilitating disease with typical onset between 20 and 40 years of age, so the disability associated with this disease, unfortunately, occurs in the prime of life. At a very early stage of MS, the relapsing-remitting mobility impairment occurs in parallel with a progressive decline in cognition, which is subclinical. This stage of the disease is considered the beginning of progressive MS. Understanding where a patient is along such a subclinical phase could be critical for therapeutic efficacy and enrollment in clinical trials to test drugs targeted at neurodegeneration. Since the disease course is uneven among patients, biomarkers are needed to provide insights into pathogenesis, diagnosis, and prognosis of events that affect neurons during this subclinical phase that shapes neurodegeneration and disability. Thus, subclinical cognitive decline must be better understood. One approach to this problem is to follow known biomarkers of neurodegeneration over time. These biomarkers include Neurofilament, Tau and phosphotau protein, amyloid-peptide-β, Brl2 and Brl2-23, N-Acetylaspartate, and 14-3-3 family proteins. A composite set of these serum-based biomarkers of neurodegeneration might provide a distinct signature in early vs. late subclinical cognitive decline, thus offering additional diagnostic criteria for progressive neurodegeneration and response to treatment. Studies on serum-based biomarkers are described together with selective studies on CSF-based biomarkers and MRI-based biomarkers.

Metabolites and Biomarker Compounds of Neurodegenerative Diseases in Cerebrospinal Fluid

Despite recent advances in diagnostic procedures for neurological disorders, it is still difficult to definitively diagnose some neurodegenerative diseases without neuropathological examination of autopsied brain tissue. As pathological processes in the brain are frequently reflected in the components of cerebrospinal fluid (CSF), CSF samples are sometimes useful for diagnosis. After CSF is secreted from the choroid plexus epithelial cells in the ventricles, some flows in the brain, some is mixed with intracerebral interstitial fluid, and some is excreted through two major drainage pathways, i.e., the intravascular periarterial drainage pathway and the glymphatic system. Accordingly, substances produced by metabolic and pathological processes in the brain may be detectable in CSF. Many papers have reported changes in the concentration of substances in the CSF of patients with metabolic and neurological disorders, some of which can be useful biomarkers of the disorders. In this paper, we show the significance of glucose- and neurotransmitter-related CSF metabolites, considering their transporters in the choroid plexus; summarize the reported candidates of CSF biomarkers for neurodegenerative diseases, including amyloid-β, tau, α-synuclein, microRNAs, and mitochondrial DNA; and evaluate their potential as efficient diagnostic tools.

Tauopathies: new perspectives and challenges

BACKGROUND

Tauopathies are a class of neurodegenerative disorders characterized by neuronal and/or glial tau-positive inclusions.

MAIN BODY

Clinically, tauopathies can present with a range of phenotypes that include cognitive/behavioral-disorders, movement disorders, language disorders and non-specific amnestic symptoms in advanced age. Pathologically, tauopathies can be classified based on the predominant tau isoforms that are present in the inclusion bodies (i.e., 3R, 4R or equal 3R:4R ratio). Imaging, cerebrospinal fluid (CSF) and blood-based tau biomarkers have the potential to be used as a routine diagnostic strategy and in the evaluation of patients with tauopathies. As tauopathies are strongly linked neuropathologically and genetically to tau protein abnormalities, there is a growing interest in pursuing of tau-directed therapeutics for the disorders. Here we synthesize emerging lessons on tauopathies from clinical, pathological, genetic, and experimental studies toward a unified concept of these disorders that may accelerate the therapeutics.

CONCLUSIONS

Since tauopathies are still untreatable diseases, efforts have been made to depict clinical and pathological characteristics, identify biomarkers, elucidate underlying pathogenesis to achieve early diagnosis and develop disease-modifying therapies.

ABI3 Is a Novel Early Biomarker of Alzheimer's Disease

BACKGROUND

The Abi3 gene has been suggested to be an important regulator of microglia during Alzheimer's disease (AD), but the diagnostic power of ABI3 in neurodegenerative disease has rarely been reported.

OBJECTIVE

The aim of this study was to evaluate the diagnostic value of ABI3 in AD patients.

METHODS

ELISAs were used to measure the ABI3 level in the serum and cerebrospinal fluid (CSF) of AD patients as well as in the serum of APP/PS1 mice. RT-PCR and western blot were further performed to detect the expression levels of ABI3 in peripheral blood mononuclear cells (PBMCs) of AD subjects as well as in the hippocampus and cortical tissue of APP/PS1 mice. The correlation of cognitive ability with ABI3 level was estimated by linear regression analysis. Moreover, the diagnostic value of ABI3 for AD was assessed with ROC analysis.

RESULTS

The ABI3 levels all decreased significantly in the serum, CSF, and PBMCs of AD patients and showed a good diagnostic performance. In addition, the ABI3 levels were observed to decrease markedly in the hippocampus from 5-month-old mice, but the dramatic change only appeared in the cortical tissue in the 9-month-old APP/PS1 mice. The ABI3 levels in the PBMCs of AD patients and in the hippocampus of APP/PS1 mice were all positively correlated with cognitive capacity.

CONCLUSION

These results demonstrated that ABI3 in serum, CSF, and PBMCs could be a novel early diagnostic biomarker of AD. Moreover, ABI3 had potential to be a novel tracer marker in hippocampus of early AD.

Neurofilament Light Chain Levels in Frontotemporal Dementia and Progressive Supranuclear Palsy: A Systematic Review

BACKGROUND

It can be challenging to discriminate between progressive supranuclear palsy (PSP) and frontotemporal dementia (FTD). However, a correct diagnosis is a precondition for targeted treatment strategies and proper patient counseling. There has been a growing interest to identify cerebrospinal fluid (CSF) biomarkers, including neurofilament light chain (NfL).

OBJECTIVE

This systematic review evaluates the existing literature on neurofilament light in CSF aiming to validate its utility for differentiating FTD from PSP.

METHODS

A systematic literature search was conducted. A broad range of synonyms for PSP, NfL, and FTD as well as associated MeSH terms, were combined and used as keywords when searching. Relevant data were extracted and assessed for risk of bias.

RESULTS

Nine studies including a total of 671 patients with FTD, 254 patients with PSP, 523 healthy controls, and 1,771 patients with other disorders were included in the review. Four studies found a significantly higher level of CSF NfL in FTD (n = 445) compared to PSP (n = 124); however, in three of these studies the difference was only significant in certain FTD variants. Four studies found no significant difference in CSF NfL between PSP (n = 98) and FTD (n = 248). One study found a significantly higher level of NfL in PSP (n = 33) compared to FTD (n = 16).

CONCLUSION

In the majority of patients in the studies included in this review, a higher level of NfL in CSF was found in patients with FTD compared to patients with PSP; however, results were inconsistent and prospective studies including large study cohorts are needed.

Plasma Neurofilament Light (NfL) in Patients Affected by Niemann-Pick Type C Disease (NPCD)

(1) Background: Niemann-Pick type C disease (NPCD) is an autosomal recessive lysosomal storage disorder caused by mutations in the NPC1 or NPC2 genes. The clinical presentation is characterized by visceral and neurological involvement. Apart from a small group of patients presenting a severe perinatal form, all patients develop progressive and fatal neurological disease with an extremely variable age of onset. Different biomarkers have been identified; however, they poorly correlate with neurological disease. In this study we assessed the possible role of plasma NfL as a neurological disease-associated biomarker in NPCD. (2) Methods: Plasma NfL levels were measured in 75 healthy controls and 26 patients affected by NPCD (24 NPC1 and 2 NPC2; 39 samples). (3) Results: Plasma NfL levels in healthy controls correlated with age and were significantly lower in pediatric patients as compared to adult subjects (p = 0.0017). In both pediatric and adult NPCD patients, the plasma levels of NfL were significantly higher than in age-matched controls (p < 0.0001). Most importantly, plasma NfL levels in NPCD patients with neurological involvement were significantly higher than the levels found in patients free of neurological signs at the time of sampling, both in the pediatric and the adult group (p = 0.0076; p = 0.0032, respectively). Furthermore, in adults the NfL levels in non-neurological patients were comparable with those found in age-matched controls. No correlations between plasma NfL levels and NPCD patient age at sampling or plasma levels of cholestan 3β-5α-6β-triol were found. (4) Conclusions: These data suggest a promising role of plasma NfL as a possible neurological disease-associated biomarker in NPCD.

Evolving concepts in progressive supranuclear palsy and other 4-repeat tauopathies

Tauopathies are classified according to whether tau deposits predominantly contain tau isoforms with three or four repeats of the microtubule-binding domain. Those in which four-repeat (4R) tau predominates are known as 4R-tauopathies, and include progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease, globular glial tauopathies and conditions associated with specific MAPT mutations. In these diseases, 4R-tau deposits are found in various cell types and anatomical regions of the brain and the conditions share pathological, pathophysiological and clinical characteristics. Despite being considered 'prototype' tauopathies and, therefore, ideal for studying neuroprotective agents, 4R-tauopathies are still severe and untreatable diseases for which no validated biomarkers exist. However, advances in research have addressed the issues of phenotypic overlap, early clinical diagnosis, pathophysiology and identification of biomarkers, setting a road map towards development of treatments. New clinical criteria have been developed and large cohorts with early disease are being followed up in prospective studies. New clinical trial readouts are emerging and biomarker research is focused on molecular pathways that have been identified. Lessons learned from failed trials of neuroprotective drugs are being used to design new trials. In this Review, we present an overview of the latest research in 4R-tauopathies, with a focus on progressive supranuclear palsy, and discuss how current evidence dictates ongoing and future research goals.

The fluid biomarkers of Alzheimer’s disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder. However, it still has no available disease‐modifying therapies. Its pathology cascade begins decades before symptomatic presentation. For these reasons, highly sensitive and highly specific fluid biomarkers should be developed for the early diagnosis of AD. In this study, the well‐established and emerging fluid biomarkers of AD are summarized, and recent advances on their role in early diagnosis and progression monitoring as well as their correlations with AD pathology are highlighted. Future prospects and related research directions are also discussed.

Correlation between CSF and blood neurofilament light chain protein: a systematic review and meta-analysis

OBJECTIVE

To assess the overall pooled correlation coefficient estimate between cerebrospinal fluid (CSF) and blood neurofilament light (NfL) protein.

METHODS

We searched Medline, Embase and Web of Science for published articles, from their inception to 9 July 2019, according to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Studies reporting the correlation between CSF and blood NfL in humans were included. We conducted a random-effects meta-analysis to calculate the overall pooled correlation coefficient estimate, accounting for correlation technique and assay used. Heterogeneity was assessed using the I2 statistic test. In sensitivity analyses, we calculated the pooled correlation coefficient estimate according to blood NfL assay: single-molecule array digital immunoassay (Simoa), electrochemiluminescence (ECL) assay or ELISA.

RESULTS

Data were extracted from 36 articles, including 3961 paired CSF and blood NfL samples. Overall, 26/36 studies measured blood NfL using Simoa, 8/36 ECL, 1/36 ELISA and 1 study reported all three assay results. The overall meta-analysis demonstrated that the pooled correlation coefficient estimate for CSF and blood NfL was r=0.72. Heterogeneity was significant: I2=83%, p<0.01. In sensitivity analyses, the pooled correlation coefficient was similar for studies measuring blood NfL using Simoa and ECL (r=0.69 and r=0.68, respectively) but weaker for ELISA (r=0.35).

CONCLUSION

Moderate correlations are demonstrated between CSF and blood NfL, especially when blood NfL was measured using Simoa and ECL. Given its high analytical sensitivity, Simoa is the preferred assay for measuring NfL, especially at low or physiological concentrations, and this meta-analysis supports its use as the current most advanced surrogate measure of CSF NfL.

PROSPERO REGISTRATION NUMBER

CRD42019140469.

"Don't Phos Over Tau": recent developments in clinical biomarkers and therapies targeting tau phosphorylation in Alzheimer's disease and other tauopathies

Phosphorylation is one of the most prevalent post-translational modifications found in aggregated tau isolated from Alzheimer’s disease (AD) patient brains. In tauopathies like AD, increased phosphorylation or hyperphosphorylation can contribute to microtubule dysfunction and is associated with tau aggregation. In this review, we provide an overview of the structure and functions of tau protein as well as the physiologic roles of tau phosphorylation. We also extensively survey tau phosphorylation sites identified in brain tissue and cerebrospinal fluid from AD patients compared to age-matched healthy controls, which may serve as disease-specific biomarkers. Recently, new assays have been developed to measure minute amounts of specific forms of phosphorylated tau in both cerebrospinal fluid and plasma, which could potentially be useful for aiding clinical diagnosis and monitoring disease progression. Additionally, multiple therapies targeting phosphorylated tau are in various stages of clinical trials including kinase inhibitors, phosphatase activators, and tau immunotherapy. With promising early results, therapies that target phosphorylated tau  could be useful at slowing tau hyperphosphorylation and aggregation in AD and other tauopathies.

Saliva Neurofilament Light Chain Is Not a Diagnostic Biomarker for Neurodegeneration in a Mixed Memory Clinic Population

Neurodegeneration and axonal injury result in an increasing release of neurofilament light chain (NfL) into bodily fluids, including cerebrospinal fluid (CSF) and blood. Numerous studies have shown that NfL levels in CSF and blood are increased in neurodegenerative disorders and monitor neurodegeneration. Saliva is an easily accessible biofluid that could be utilized as a biofluid measurement of Alzheimer's disease (AD) biomarkers. In this study, for the first time, salivary NfL was measured and compared to plasma NfL in a consecutive cohort of patients referred to cognitive assessments. In two mixed memory clinic cohorts, saliva samples were taken from 152 patients, AD (n = 49), mild cognitive impairment (MCI) (n = 47), non-AD (n = 56), and also 17 healthy controls. In addition, 135 also had a matching plasma sample. All saliva and plasma samples were analyzed for NfL, and the association between saliva and plasma NfL and CSF levels of total tau (t-tau), phosphorylated tau (p-tau), and beta amyloid 1-42 (Aβ42) were investigated. In total, 162/169 had quantifiable levels of salivary NfL by single molecule array (Simoa). No statistically significant differences were found in salivary NfL concentration across the diagnostic groups, but as expected, significant increases were found for plasma NfL in dementia cases (P < 0.0001). There was no association between saliva and plasma NfL levels. Furthermore, saliva NfL did not correlate with CSF Aβ42, p-tau, or tau concentrations. In conclusion, NfL is detectable in saliva but does not reflect neurodegeneration in the brain.

Mechanisms of Neurodegeneration in Various Forms of Parkinsonism-Similarities and Differences

Parkinson’s disease (PD), dementia with Lewy body (DLB), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and multiple system atrophy (MSA) belong to a group of neurodegenerative diseases called parkinsonian syndromes. They share several clinical, neuropathological and genetic features. Neurodegenerative diseases are characterized by the progressive dysfunction of specific populations of neurons, determining clinical presentation. Neuronal loss is associated with extra- and intracellular accumulation of misfolded proteins. The parkinsonian diseases affect distinct areas of the brain. PD and MSA belong to a group of synucleinopathies that are characterized by the presence of fibrillary aggregates of α-synuclein protein in the cytoplasm of selected populations of neurons and glial cells. PSP is a tauopathy associated with the pathological aggregation of the microtubule associated tau protein. Although PD is common in the world’s aging population and has been extensively studied, the exact mechanisms of the neurodegeneration are still not fully understood. Growing evidence indicates that parkinsonian disorders to some extent share a genetic background, with two key components identified so far: the microtubule associated tau protein gene (MAPT) and the α-synuclein gene (SNCA). The main pathways of parkinsonian neurodegeneration described in the literature are the protein and mitochondrial pathways. The factors that lead to neurodegeneration are primarily environmental toxins, inflammatory factors, oxidative stress and traumatic brain injury.

Cerebrospinal Fluid and Blood Neurofilament Light Chain Protein in Prion Disease and Other Rapidly Progressive Dementias: Current State of the Art

Rapidly progressive dementia (RPD) is an umbrella term referring to several conditions causing a rapid neurological deterioration associated with cognitive decline and short disease duration. They comprise Creutzfeldt–Jakob disease (CJD), the archetypal RPD, rapidly progressive variants of the most common neurodegenerative dementias (NDs), and potentially treatable conditions such as infectious or autoimmune encephalitis and cerebrovascular disease. Given the significant clinical and, sometimes, neuroradiological overlap between these different disorders, biofluid markers also contribute significantly to the differential diagnosis. Among them, the neurofilament light chain protein (NfL) has attracted growing attention in recent years as a biofluid marker of neurodegeneration due to its sensitivity to axonal damage and the reliability of its measurement in both cerebrospinal fluid (CSF) and blood. Here, we summarize current knowledge regarding biological and clinical implications of NfL evaluation in biofluids across RPDs, emphasizing CJD, and other prion diseases. In the latter, NfL demonstrated a good diagnostic and prognostic accuracy and a potential value as a marker of proximity to clinical onset in pre-symptomatic PRNP mutation carriers. Similarly, in Alzheimer’s disease and other NDs, higher NfL concentrations seem to predict a faster disease progression. While increasing evidence indicates a potential clinical value of NfL in monitoring cerebrovascular disease, the association between NfL and prediction of outcome and/or disease activity in autoimmune encephalitis and infectious diseases has only been investigated in few cohorts and deserves confirmatory studies. In the era of precision medicine and evolving therapeutic options, CSF and blood NfL might aid the diagnostic and prognostic assessment of RPDs and the stratification and management of patients according to disease progression in clinical trials.

Progress regarding the context-of-use of tau as biomarker of Alzheimer's disease and other neurodegenerative diseases

Introduction: Tau protein misfolding and accumulation in toxic species is a critical pathophysiological process of Alzheimer's disease (AD) and other neurodegenerative disorders (NDDs). Tau biomarkers, namely cerebrospinal fluid (CSF) total-tau (t-tau), 181-phosphorylated tau (p-tau), and tau-PET tracers, have been recently embedded in the diagnostic criteria for AD. Nevertheless, the role of tau as a diagnostic and prognostic biomarker for other NDDs remains controversial.Areas covered: We performed a systematical PubMed-based review of the most recent advances in tau-related biomarkers for NDDs. We focused on papers published from 2015 to 2020 assessing the diagnostic or prognostic value of each biomarker.Expert opinion: The assessment of tau biomarkers in alternative easily accessible matrices, through the development of ultrasensitive techniques, represents the most significant perspective for AD-biomarker research. In NDDs, novel tau isoforms (e.g. p-tau217) or proteolytic fragments (e.g. N-terminal fragments) may represent candidate diagnostic and prognostic biomarkers and may help monitoring disease progression. Protein misfolding amplification assays, allowing the identification of different tau strains (e.g. 3 R- vs. 4 R-tau) in CSF, may constitute a breakthrough for the in vivo stratification of NDDs. Tau-PET may help tracking the spatial-temporal evolution of tau pathophysiology in AD but its application outside the AD-spectrum deserves further studies.

Diagnostic Utility of Measuring Cerebral Atrophy in the Behavioral Variant of Frontotemporal Dementia and Association With Clinical Deterioration

IMPORTANCE

The presence of atrophy on magnetic resonance imaging can support the diagnosis of the behavioral variant of frontotemporal dementia (bvFTD), but reproducible measurements are lacking.

OBJECTIVE

To assess the diagnostic and prognostic utility of 6 visual atrophy scales (VAS) and the Magnetic Resonance Parkinsonism Index (MRPI).

DESIGN, SETTING, AND PARTICIPANTS

In this diagnostic/prognostic study, data from 235 patients with bvFTD and 225 age- and magnetic resonance imaging-matched control individuals from 3 centers were collected from December 1, 1998, to September 30, 2019. One hundred twenty-one participants with bvFTD had high confidence of frontotemporal lobar degeneration (FTLD) (bvFTD-HC), and 19 had low confidence of FTLD (bvFTD-LC). Blinded clinicians applied 6 previously validated VAS, and the MRPI was calculated with a fully automated approach. Cortical thickness and subcortical volumes were also measured for comparison. Data were analyzed from February 1 to June 30, 2020.

MAIN OUTCOMES AND MEASURES

The main outcomes of this study were bvFTD-HC or a neuropathological diagnosis of 4-repeat (4R) tauopathy and the clinical deterioration rate (assessed by longitudinal measurements of Clinical Dementia Rating Sum of Boxes). Measures of cerebral atrophy included VAS scores, the bvFTD atrophy score (sum of VAS scores in orbitofrontal, anterior cingulate, anterior temporal, medial temporal lobe, and frontal insula regions), the MRPI, and other computerized quantifications of cortical and subcortical volumes. The areas under the receiver operating characteristic curve (AUROC) were calculated for the differentiation of participants with bvFTD-HC and bvFTD-LC and controls. Linear mixed models were used to evaluate the ability of atrophy measures to estimate longitudinal clinical deterioration.

RESULTS

Of the 460 included participants, 296 (64.3%) were men, and the mean (SD) age was 62.6 (11.4) years. The accuracy of the bvFTD atrophy score for the differentiation of bvFTD-HC from controls (AUROC, 0.930; 95% CI, 0.903-0.957) and bvFTD-HC from bvFTD-LC (AUROC, 0.880; 95% CI, 0.787-0.972) was comparable to computerized measures (AUROC, 0.973 [95% CI, 0.954-0.993] and 0.898 [95% CI, 0.834-0.962], respectively). The MRPI was increased in patients with bvFTD and underlying 4R tauopathies compared with other FTLD subtypes (14.1 [2.0] vs 11.2 [2.6] points; P < .001). Higher bvFTD atrophy scores were associated with faster clinical deterioration in bvFTD (1.86-point change in Clinical Dementia Rating Sum of Boxes score per bvFTD atrophy score increase per year; 95% CI, 0.99-2.73; P < .001).

CONCLUSIONS AND RELEVANCE

Based on these study findings, in bvFTD, VAS increased the diagnostic certainty of underlying FTLD, and the MRPI showed potential for the detection of participants with underlying 4R tauopathies. These widely available measures of atrophy can also be useful to estimate longitudinal clinical deterioration.

Plasma Tau and Neurofilament Light in Frontotemporal Lobar Degeneration and Alzheimer Disease

OBJECTIVE

To test the hypothesis that plasma total tau (t-tau) and neurofilament light chain (NfL) concentrations may have a differential role in the study of frontotemporal lobar degeneration syndromes (FTLD-S) and clinically diagnosed Alzheimer disease syndromes (AD-S), we determined their diagnostic and prognostic value in FTLD-S and AD-S and their sensitivity to pathologic diagnoses.

METHODS

We measured plasma t-tau and NfL with the Simoa platform in 265 participants: 167 FTLD-S, 43 AD-S, and 55 healthy controls (HC), including 82 pathology-proven cases (50 FTLD-tau, 18 FTLD-TDP, 2 FTLD-FUS, and 12 AD) and 98 participants with amyloid PET. We compared cross-sectional and longitudinal biomarker concentrations between groups, their correlation with clinical measures of disease severity, progression, and survival, and cortical thickness.

RESULTS

Plasma NfL, but not plasma t-tau, discriminated FTLD-S from HC and AD-S from HC. Both plasma NfL and t-tau were poor discriminators between FLTD-S and AD-S. In pathology-confirmed cases, plasma NfL was higher in FTLD than AD and in FTLD-TDP compared to FTLD-tau, after accounting for age and disease severity. Plasma NfL, but not plasma t-tau, predicted clinical decline and survival and correlated with regional cortical thickness in both FTLD-S and AD-S. The combination of plasma NfL with plasma t-tau did not outperform plasma NfL alone.

CONCLUSION

Plasma NfL is superior to plasma t-tau for the diagnosis and prediction of clinical progression of FTLD-S and AD-S.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that plasma NfL has superior diagnostic and prognostic performance vs plasma t-tau in FTLD and AD.

Neurofilament light chain level in plasma extracellular vesicles and Parkinson's disease

Background:

Neurofilament light chain (NfL) is essential for axonal maintenance and reflects neuronal damage. Extracellular vesicles (EVs), especially exosomes, secreted by cells into the blood, are emerging as novel biomedical research platforms of physiological and pathological processes. The present study investigated the possible association between plasma EV NfL and Parkinson’s disease (PD).

Methods:

One hundred and sixteen patients with mild to moderate PD and 46 non-PD, neurological controls were recruited, and their clinical motor symptoms and cognitive function were evaluated. Plasma EVs were isolated using an exoEasy kit, and immunomagnetic reduction assay was used to assess EV NfL level. Statistical analysis was performed using SPSS 25.0, and p < 0.05 was considered significant.

Results:

The isolated plasma EVs were validated according to size and the presence of specific surface markers. Compared with the neurological control group, the levels of plasma EV NfL in patients with PD were not significantly different (PD: 9.42 ± 3.89, control: 9.53 ± 3.62 pg/mL plasma, p = 0.71). On the other hand, plasma EV NfL in patients with PD trendwise correlated with the severity of akinetic rigidity (p = 0.05). PD patients with optimal EV NfL (lowest quartile) had 6.66 ± 2.08 lower Unified Parkinson’s Disease Rating Scale-III score after adjustment for age, sex, and disease duration.

Conclusion:

Plasma EV NfL levels did not distinguish patients with PD from the neurological control group. The possible correlation between plasma EV NfL with the severity of motor symptoms within the PD patients, especially with akinetic rigidity, was noted. Further clinical validation of the blood EV NfL by a longitudinal follow-up study of PD patients is warranted.

Four-Repeat Tauopathies: Current Management and Future Treatments

Four-repeat tauopathies are a neurodegenerative disease characterized by brain parenchymal accumulation of a specific isoform of the protein tau, which gives rise to a wide breadth of clinical syndromes encompassing diverse symptomatology, with the most common syndromes being progressive supranuclear palsy-Richardson's and corticobasal syndrome. Despite the lack of effective disease-modifying therapies, targeted treatment of symptoms can improve quality of life for patients with 4-repeat tauopathies. However, managing these symptoms can be a daunting task, even for those familiar with the diseases, as they span motor, sensory, cognitive, affective, autonomic, and behavioral domains. This review describes current approaches to symptomatic management of common clinical symptoms in 4-repeat tauopathies with a focus on practical patient management, including pharmacologic and nonpharmacologic strategies, and concludes with a discussion of the history and future of disease-modifying therapeutics and clinical trials in this population.

Molecular and Imaging Biomarkers in Alzheimer's Disease: A Focus on Recent Insights

Alzheimer’s disease (AD) is the most common neurodegenerative disease among the elderly, affecting millions of people worldwide and clinically characterized by a progressive and irreversible cognitive decline. The rapid increase in the incidence of AD highlights the need for an easy, efficient and accurate diagnosis of the disease in its initial stages in order to halt or delay the progression. The currently used diagnostic methods rely on measures of amyloid-β (Aβ), phosphorylated (p-tau) and total tau (t-tau) protein levels in the cerebrospinal fluid (CSF) aided by advanced neuroimaging techniques like positron emission tomography (PET) and magnetic resonance imaging (MRI). However, the invasiveness of these procedures and the high cost restrict their utilization. Hence, biomarkers from biological fluids obtained using non-invasive methods and novel neuroimaging approaches provide an attractive alternative for the early diagnosis of AD. Such biomarkers may also be helpful for better understanding of the molecular mechanisms underlying the disease, allowing differential diagnosis or at least prolonging the pre-symptomatic stage in patients suffering from AD. Herein, we discuss the advantages and limits of the conventional biomarkers as well as recent promising candidates from alternative body fluids and new imaging techniques.

Increased Noradrenaline as an Additional Cerebrospinal Fluid Biomarker in PSP-Like Parkinsonism

Academic centers utilize sequential clinical and neuroimaging assessments, including morphometric ratios, to obtain an unequivocal diagnosis of the non-synucleinopathic forms of Parkinsonism, such as progressive supranuclear palsy (PSP), however, a 1–2 year follow-up is required. The on-going long-lasting trials using anti-tau antibodies for PSP patients might therefore be biased by the incorrect enrollment of Parkinson’s disease (PD) patients manifesting early axial signs. This perspective study aimed at achieving two major goals: first, to summarize the established biomarker candidates found in cerebrospinal fluid (CSF) in probable PSP patients, including low p-tau and altered neurofilaments. Second, we share our recent data, from CSF samples of well-selected PSP subjects, attributable to both main variants (and revisited in light of MDS criteria), who were followed for 1 year before and 2 years after lumbar puncture. We found a significantly high level of noradrenaline (NE) in these patients, similar to controls, when compared to PD patients. In contrast, CSF samples, in PD, showed a significant reduction in CSF NE and its major metabolite, which confirmed that PD is a multi-system disease involving several endogenous pathways. The NE axis impairments were prominent in PSP featuring worse NPI. It might represent a counterpart to the early and peculiar psycho-pathological profiles that are observed in tauopathies. In conclusion, we highlight that CSF biomarkers, which are easy to collect, can provide rapid insights as diagnostic tools. Early alterations in endogenous NE machinery in atypical Parkinsonism may represent a specific risk trait in forms characterized by a worse prognosis.

Safety of the tau-directed monoclonal antibody BIIB092 in progressive supranuclear palsy: a randomised, placebo-controlled, multiple ascending dose phase 1b trial

BACKGROUND

Progressive supranuclear palsy is a rare neurodegenerative disease associated with dysfunctional tau protein. BIIB092 is a humanised monoclonal antibody that binds to N-terminal tau and is thus being assessed as a potential novel treatment for progressive supranuclear palsy. We aimed to investigate the safety and tolerability of BIIB092 in individuals with progressive supranuclear palsy.

METHODS

This 12-week, double-blind, randomised, placebo-controlled, multiple ascending dose, phase 1b trial was done at 13 outpatient sites in the USA. Participants aged 41-86 years with probable or possible progressive supranuclear palsy with a score of 20 or greater on the Mini-Mental State Examination (MMSE) were enrolled. Three BIIB092 dose escalation cohorts (150 mg, 700 mg, or 2100 mg; eight participants per cohort) were tested sequentially. For each dose cohort, the first two participants were randomly assigned by a computer-generated scheme to receive either BIIB092 or placebo intravenously every 4 weeks for 57 days. After 2 days, the six remaining participants in each cohort were randomly assigned (5:1) to receive BIIB092 or placebo for 57 days. An additional expansion panel of 24 patients was randomly assigned (3:1) to receive 2100 mg or placebo every 4 weeks for 57 days. All participants were followed up to day 85. The primary outcome was safety, which was analysed in the treated population (all enrolled participants who received at least one dose of the study drug). This trial is registered with ClinicalTrials.gov, NCT02460094.

FINDINGS

Between Oct 2, 2015, and Oct 19, 2016, 48 participants were enrolled and randomly assigned to the BIIB092 (n=36) and placebo (n=12) groups. No apparent demographic differences were observed between the two groups at baseline. All 48 participants completed the treatment phase of the study. Adverse events were generally mild to moderate in severity; the most common in the placebo and BIIB092 groups were falls (in two [17%] of 12 patients and in ten [28%] of 36 patients), urinary tract infections (in one [8%] of 12 and in six [17%] of 36), contusions (in one [8%] of 12 and in five [14%] of 36), and headaches (in none and in five [14%] of 36). Four serious adverse events resulting in admission to hospital were reported in three participants who received BIIB092 2100 mg: two severe adverse events of urinary tract infection, one severe adverse event of change in mental status, and one moderate adverse event of aspiration pneumonia. None was considered to be related to the study drug, all were resolved, and no deaths were reported.

INTERPRETATION

Repeated administration of the anti-tau monoclonal antibody BIIB092, at doses of up to 2100 mg, appears to be well tolerated in participants with progressive supranuclear palsy. Results of this phase 1b trial have informed the design of the ongoing phase 2 PASSPORT (NCT03068468) study to examine the efficacy and safety of BIIB092.

FUNDING

Bristol-Myers Squibb, Biogen.

Open-Label Phase 1 Futility Studies of Salsalate and Young Plasma in Progressive Supranuclear Palsy

BACKGROUND

Progressive supranuclear palsy (PSP) is a neurodegenerative disease without approved therapies, and therapeutics are often tried off-label in the hope of slowing disease progression. Results from these experiences are seldom shared, which limits evidence-based knowledge to guide future treatment decisions.

OBJECTIVES

To describe an open-label experience, including safety/tolerability, and longitudinal changes in biomarkers of disease progression in PSP-Richardson's syndrome (PSP-RS) patients treated with either salsalate or young plasma and compare to natural history data from previous multicenter studies.

METHODS

For 6 months, 10 PSP-RS patients received daily salsalate 2,250 mg, and 5 patients received monthly infusions of four units of young plasma. Every 3 months, clinical severity was assessed with the Progressive Supranuclear Palsy Rating Scale (PSPRS), and MRI was obtained for volumetric measurement of midbrain. A range of exploratory biomarkers, including cerebrospinal fluid levels of neurofilament light chain, were collected at baseline and 6 months. Interventional data were compared to historical PSP-RS patients from the davunetide clinical trial and the 4-Repeat Tauopathy Neuroimaging Initiative.

RESULTS

Salsalate and young plasma were safe and well tolerated. PSPRS change from baseline (mean ± standard deviation [SD]) was similar in salsalate (+5.6 ± 9.6), young plasma (+5.0 ± 7.1), and historical controls (+5.6 ± 7.1), and change in midbrain volume (cm3 ± SD) did not differ between salsalate (-0.07 ± 0.03), young plasma (-0.06 ± 0.03), and historical controls (-0.06 ± 0.04). No differences were observed between groups on any exploratory endpoint.

CONCLUSIONS

Neither salsalate nor young plasma had a detectable effect on disease progression in PSP-RS. Focused open-label clinical trials incorporating historical clinical, neuropsychological, fluid, and imaging biomarkers provide useful preliminary data about the promise of novel PSP-directed therapies.

An update on blood-based biomarkers for non-Alzheimer neurodegenerative disorders

Cerebrospinal fluid analyses and neuroimaging can identify the underlying pathophysiology at the earliest stage of some neurodegenerative disorders, but do not have the scalability needed for population screening. Therefore, a blood-based marker for such pathophysiology would have greater utility in a primary care setting and in eligibility screening for clinical trials. Rapid advances in ultra-sensitive assays have enabled the levels of pathological proteins to be measured in blood samples, but research has been predominantly focused on Alzheimer disease (AD). Nonetheless, proteins that were identified as potential blood-based biomarkers for AD, for example, amyloid-β, tau, phosphorylated tau and neurofilament light chain, are likely to be relevant to other neurodegenerative disorders that involve similar pathological processes and could also be useful for the differential diagnosis of clinical symptoms. This Review outlines the neuropathological, clinical, molecular imaging and cerebrospinal fluid features of the most common neurodegenerative disorders outside the AD continuum and gives an overview of the current status of blood-based biomarkers for these disorders.

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.

Fulminant corticobasal degeneration: a distinct variant with predominant neuronal tau aggregates

Corticobasal degeneration typically progresses gradually over 5–7 years from onset till death. Fulminant corticobasal degeneration cases with a rapidly progressive course were rarely reported (RP-CBD). This study aimed to investigate their neuropathological characteristics. Of the 124 autopsy-confirmed corticobasal degeneration cases collected from 14 centres, we identified 6 RP-CBD cases (4.8%) who died of advanced disease within 3 years of onset. These RP-CBD cases had different clinical phenotypes including rapid global cognitive decline (N = 2), corticobasal syndrome (N = 2) and Richardson’s syndrome (N = 2). We also studied four corticobasal degeneration cases with an average disease duration of 3 years or less, who died of another unrelated illness (Intermediate-CBD). Finally, we selected 12 age-matched corticobasal degeneration cases out of a cohort of 110, who had a typical gradually progressive course and reached advanced clinical stage (End-stage-CBD). Quantitative analysis showed high overall tau burden (p = 0.2) and severe nigral cell loss (p = 0.47) in both the RP-CBD and End-stage-CBD groups consistent with advanced pathological changes, while the Intermediate-CBD group (mean disease duration = 3 years) had milder changes than End-stage-CBD (p < 0.05). These findings indicated that RP-CBD cases had already developed advanced pathological changes as those observed in End-stage-CBD cases (mean disease duration = 6.7 years), but within a significantly shorter duration (2.5 years; p < 0.001). Subgroup analysis was performed to investigate the cellular patterns of tau aggregates in the anterior frontal cortex and caudate by comparing neuronal-to-astrocytic plaque ratios between six RP-CBD cases, four Intermediate-CBD and 12 age-matched End-stage-CBD. Neuronal-to-astrocytic plaque ratios of Intermediate-CBD and End-stage-CBD, but not RP-CBD, positively correlated with disease duration in both the anterior frontal cortex and caudate (p = 0.02). In contrast to the predominance of astrocytic plaques we previously reported in preclinical asymptomatic corticobasal degeneration cases, neuronal tau aggregates predominated in RP-CBD exceeding those in Intermediate-CBD (anterior frontal cortex: p < 0.001, caudate: p = 0.001) and End-stage-CBD (anterior frontal cortex: p = 0.03, caudate: p = 0.01) as demonstrated by its higher neuronal-to-astrocytic plaque ratios in both anterior frontal cortex and caudate. We did not identify any difference in age at onset, any pathogenic tau mutation or concomitant pathologies that could have contributed to the rapid progression of these RP-CBD cases. Mild TDP-43 pathology was observed in three RP-CBD cases. All RP-CBD cases were men. The MAPT H2 haplotype, known to be protective, was identified in one RP-CBD case (17%) and 8 of the matched End-stage-CBD cases (67%). We conclude that RP-CBD is a distinct aggressive variant of corticobasal degeneration with characteristic neuropathological substrates resulting in a fulminant disease process as evident both clinically and pathologically. Biological factors such as genetic modifiers likely play a pivotal role in the RP-CBD variant and should be the subject of future research.

Molecular profiling in Parkinsonian syndromes: CSF biomarkers

An accurate and early diagnosis of degenerative parkinsonian syndromes is a major need for their correct and timely therapeutic management. The current diagnostic criteria are mostly based on clinical features and molecular imaging. However, diagnostic doubts often persist especially in the early stages of diseases when signs are slight, ambiguous and overlapping among different syndromes. Molecular imaging may not be altered in the early stages of diseases, also failing to discriminate among different syndromes. Cerebrospinal fluid (CSF) represents an ideal source of biomarkers reflecting different pathways of neuropathological changes taking place in the brain and preceding the clinical onset. The aim of this review is to provide un update on CSF biomarkers in parkinsonian disorders, discussing in detail their association with neuropathological correlates. Their potential contribution in differential diagnosis and prognostic assessment of different parkinsonian syndromes is also discussed. Before entering the clinical use both for diagnostic and prognostic purposes, these CSF biomarkers need to be thoroughly assessed in terms of pre-analytical and analytical variability, as well as to clinical validation in independent cohorts.

Diagnostic value of plasma phosphorylated tau181 in Alzheimer's disease and frontotemporal lobar degeneration

With the potential development of new disease-modifying Alzheimer's disease (AD) therapies, simple, widely available screening tests are needed to identify which individuals, who are experiencing symptoms of cognitive or behavioral decline, should be further evaluated for initiation of treatment. A blood-based test for AD would be a less invasive and less expensive screening tool than the currently approved cerebrospinal fluid or amyloid β positron emission tomography (PET) diagnostic tests. We examined whether plasma tau phosphorylated at residue 181 (pTau181) could differentiate between clinically diagnosed or autopsy-confirmed AD and frontotemporal lobar degeneration. Plasma pTau181 concentrations were increased by 3.5-fold in AD compared to controls and differentiated AD from both clinically diagnosed (receiver operating characteristic area under the curve of 0.894) and autopsy-confirmed frontotemporal lobar degeneration (area under the curve of 0.878). Plasma pTau181 identified individuals who were amyloid β-PET-positive regardless of clinical diagnosis and correlated with cortical tau protein deposition measured by 18F-flortaucipir PET. Plasma pTau181 may be useful to screen for tau pathology associated with AD.

Latest advances in cerebrospinal fluid and blood biomarkers of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease and its diagnosis has classically been based on clinical symptoms. Recently, a biological rather than a syndromic definition of the disease has been proposed that is based on biomarkers that reflect neuropathological changes. In AD, there are two main biomarker categories, namely neuroimaging and fluid biomarkers [cerebrospinal fluid (CSF) and blood]. As a complex and multifactorial disease, AD biomarkers are important for an accurate diagnosis and to stage the disease, assess the prognosis, test target engagement, and measure the response to treatment. In addition, biomarkers provide us with information that, even if it does not have a current clinical use, helps us to understand the mechanisms of the disease. In addition to the pathological hallmarks of AD, which include amyloid-β and tau deposition, there are multiple concomitant pathological events that play a key role in the disease. These include, but are not limited to, neurodegeneration, inflammation, vascular dysregulation or synaptic dysfunction. In addition, AD patients often have an accumulation of other proteins including α-synuclein and TDP-43, which may have a pathogenic effect on AD. In combination, there is a need to have biomarkers that reflect different aspects of AD pathogenesis and this will be important in the future to establish what are the most suitable applications for each of these AD-related biomarkers. It is unclear whether sex, gender, or both have an effect on the causes of AD. There may be differences in fluid biomarkers due to sex but this issue has often been neglected and warrants further research. In this review, we summarize the current state of the principal AD fluid biomarkers and discuss the effect of sex on these biomarkers.

Neurofilament light is a treatment-responsive biomarker in CLN2 disease

OBJECTIVE

Neuronal ceroid lipofuscinosis type 2 (CLN2 disease) is a rare, progressive, fatal neurodegenerative pediatric disorder resulting from deficiencies of the lysosomal enzyme tripeptidyl peptidase 1 that are caused by mutations in TPP1. Identifying biomarkers of CLN2 disease progression will be important in assessing the efficacy of therapeutic interventions for this disorder. Neurofilament light is an intrinsic component of healthy neurons; elevated circulating extracellular neurofilament light is a biomarker of neuropathology in several adult-onset neurological diseases. Our objective was to assess whether circulating neurofilament light is a biomarker that is responsive to enzyme replacement therapy (ERT) in CLN2 disease.

METHODS

Using an ultrasensitive immunoassay, we assessed plasma neurofilament light changes during disease progression in a canine model of CLN2 disease and in ERT clinical trial CLN2 disease patients.

RESULTS

In tripeptidyl peptidase 1 (TPP1)-null dogs (N = 11), but not in control dogs [N = 6 (TPP1^+/- ) and N = 27 (WT)], neurofilament light levels increased more than tenfold above initial low baseline levels during disease progression. Before treatment in 21 human subjects with CLN2 disease (age range: 1.72-6.85 years), neurofilament light levels were 48-fold higher (P < 0.001) than in 7 pediatric controls (age range: 8-11 years). Pretreatment neurofilament light did not significantly correlate with disease severity or age. In CLN2 disease subjects receiving ERT, neurofilament light levels decreased by 50% each year over more than 3 years of treatment.

INTERPRETATION

Our data indicate that circulating neurofilament light is a treatment-responsive biomarker in CLN2 disease and could contribute to understanding of the pathophysiology of this devastating pediatric disorder.

Progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a neurodegenerative disease characterized pathologically by 4 repeat tau deposition in various cell types and anatomical regions. Richardson's syndrome (RS) is the initially described and one of the clinical phenotypes associated with PSP pathology, characterized by vertical supranuclear gaze paly in particular downwards, postural instability with early falls and subcortical frontal dementia. PSP can manifest as several other clinical phenotypes, including PSP-parkinsonism, -pure akinesia with gait freezing, -frontotemporal dementia, - corticobasal syndrome, - speech/language impairment. RS can also have a pathologic diagnosis other than PSP, including corticobasal degeneration, FTD-TDP-43 and others. New clinical diagnostic criteria take into account this phenotypic variability in an attempt to diagnose the disease earlier, given the current lack of a validated biomarker. At present, therapeutic options for PSP are symptomatic and insufficient. Recent large neuroprotective trials have failed to provide a positive clinical outcome, however, have led to the design of better studies that are ongoing and hold promise for a neuroprotective treatment for PSP.

Multiple System Atrophy: Recent Developments and Future Perspectives

Multiple system atrophy (MSA) is a rare and fatal neurodegenerative disorder characterized by a variable combination of parkinsonism, cerebellar impairment, and autonomic dysfunction. The pathologic hallmark is the accumulation of aggregated α-synuclein in oligodendrocytes, forming glial cytoplasmic inclusions, which qualifies MSA as a synucleinopathy together with Parkinson's disease and dementia with Lewy bodies. The underlying pathogenesis is still not well understood. Some symptomatic treatments are available, whereas neuroprotection remains an urgent unmet treatment need. In this review, we critically appraise significant developments of the past decade with emphasis on pathogenesis, diagnosis, prognosis, and treatment development. We further discuss unsolved questions and highlight some perspectives. © 2019 International Parkinson and Movement Disorder Society.