Plasma neurofilament light chain predicts cerebellar atrophy and clinical progression in spinocerebellar ataxia

Longitudinal Changes of Clinical, Imaging, and Fluid Biomarkers in Preataxic and Early Ataxic Spinocerebellar Ataxia Type 2 and 7 Carriers

BACKGROUND AND OBJECTIVES

Brain MRI abnormalities and increases in neurofilament light chain (NfL) have mostly been observed in cross-sectional studies before ataxia onset in polyglutamine spinocerebellar ataxias. Our study aimed to identify longitudinal changes in biological, clinical, and/or imaging biomarkers in spinocerebellar ataxia (SCA) 2 and SCA7 carriers over 1 year.

METHODS

We studied SCA2 and SCA7 carriers and controls (expansion-negative relatives) at the Paris Brain Institute. Inclusion criteria included Scale for the Assessment and Rating of Ataxia (SARA) scores between 0 and 15. Assessments at baseline, 6 months, and 12 months comprised neurologic, quality of life, orofacial motor, neuropsychological, and ophthalmologic examinations, along with gait and oculomotor recordings, brain MRI, CSF, and blood sampling. The primary outcome was the longitudinal change in these assessments over 1 year.

RESULTS

We included 15 SCA2 carriers, 15 SCA7 carriers, and 10 controls between May 2020 and April 2021. At baseline, the ages were similar (41 [37, 46] for SCA2, 38 [28.5, 39.8] for SCA7, and 39.5 [31, 54.5] for controls, p = 0.78), as well the sex (p = 0.61); SARA scores were low but different (4 [1.25, 6.5] in SCA2, 2 [0, 11.5] in SCA7, and 0 in controls, p < 0.01). Pons and medulla volumes were smaller in SCAs (p < 0.05) and cerebellum volume only in SCA2 (p = 0.01). Plasma NfL levels were higher in SCA participants (SCA2: 14.2 pg/mL [11.52, 15.89], SCA7: 15.53 [13.27, 23.23]) than in controls (4.88 [3.56, 6.17], p < 0.001). After 1-year follow-up, in SCA2, there was significant pons (-144 ± 60 mm3) and cerebellum (-1,508 ± 580 mm3) volume loss and a worsening of gait assessment; in SCA7, SARA score significantly increased (+1.3 ± 0.4) and outer retinal nuclear layer thickness decreased (-15.4 ± 1.6 μm); for both SCA groups, the orofacial motor assessment significantly worsened. For preataxic and early ataxic carriers, the strongest longitudinal deterioration on outcome measures was orofacial motility in SCA2 and retinal thickness in SCA7.

DISCUSSION

Despite the limitation of the small sample size, we detected annual changes in preataxic and early ataxic SCA individuals across brain MRI imaging, clinical scores, gait parameters, and retinal thickness. These parameters could serve as potential end points for future therapeutic trials in the preataxic phase.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov NCT04288128.

Decreasing ganglioside synthesis delays motor and cognitive symptom onset in Spg11 knockout mice

Biallelic variants in the SPG11 gene account for the most common form of autosomal recessive hereditary spastic paraplegia characterized by motor and cognitive impairment, with currently no therapeutic option. We previously observed in a Spg11 knockout mouse that neurodegeneration is associated with accumulation of gangliosides in lysosomes. To test whether a substrate reduction therapy could be a therapeutic option, we downregulated the key enzyme involved in ganglioside biosynthesis using an AAV-PHP.eB viral vector expressing a miRNA targeting St3gal5. Downregulation of St3gal5 in Spg11 knockout mice prevented the accumulation of gangliosides, delayed the onset of motor and cognitive symptoms, and prevented the upregulation of serum levels of neurofilament light chain, a biomarker widely used in neurodegenerative diseases. Importantly, similar results were observed when Spg11 knockout mice were administrated venglustat, a pharmacological inhibitor of glucosylceramide synthase expected to decrease ganglioside synthesis. Downregulation of St3gal5 or venglustat administration in Spg11 knockout mice strongly decreased the formation of axonal spheroids, previously associated with impaired trafficking. Venglustat had similar effect on cultured human SPG11 neurons. In conclusion, this work identifies the first disease-modifying therapeutic strategy in SPG11, and provides data supporting its relevance for therapeutic testing in SPG11 patients.

Multimodal, Longitudinal Profiling of SCA1 Identifies Predictors of Disease Severity and Progression

OBJECTIVES

Spinocerebellar ataxia type 1 (SCA1) is a rare autosomal dominant neurodegenerative disease. Objective surrogate markers sensitive to detect changes in disease severity are needed to reduce sample sizes in interventional trials and identification of predictors of faster disease progression would facilitate patient selection, enrichment, or stratification in such trials.

METHODS

We performed a prospective 1-year longitudinal, multimodal study in 34 ataxic SCA1 individuals and 21 healthy controls. We collected clinical, patient-reported outcomes, biochemical and magnetic resonance (MR) biomarkers at baseline and after 1 year. We determined 1-year progression and evaluated the potential predictive value of several baseline markers on 1-year disease progression.

RESULTS

At baseline, multiple structural and spectroscopic MR markers in pons and cerebellum differentiated SCA1 from healthy controls and correlated with disease severity. Plasma and cerebrospinal fluid (CSF) neurofilament light (NfL) chain and CSF glial fibrillary acidic protein (GFAP) were elevated in SCA1. In longitudinal analysis, total brainstem and pontine volume change, inventory of non-ataxia signs (INAS) count, and SCA functional index (SCAFI) showed larger responsiveness compared to the Scale for Assessment and Rating of Ataxia (SARA). Longer disease duration, longer non-expanded CAG repeat length, and higher disease burden were associated with faster SARA increase after 1-year in the SCA1 group. Similarly, lower baseline brainstem, pontine, and cerebellar volumes, as well as lower levels of N-acetylaspartate and glutamate in the cerebellar white matter, were also associated with faster SARA increase.

INTERPRETATION

Our results guide the selection of the most sensitive measures of disease progression in SCA1 and have identified features associated with accelerated progression that could inform the design of clinical trials. ANN NEUROL 2024.

The Role of Protein Quantity Control in Polyglutamine Spinocerebellar Ataxias

Polyglutamine spinocerebellar ataxias (polyQ SCAs) represent the most prevalent subtype of SCAs. The primary pathogenic mechanism is believed to be the gain-of-function neurotoxicity of polyQ proteins. Strategies such as enhancing the degradation or inhibiting the accumulation of these mutant proteins are pivotal for reducing their toxicity and slowing disease progression. The protein quality control (PQC) system, comprising primarily molecular chaperones and the ubiquitin‒proteasome system (UPS), is essential for maintaining protein homeostasis by regulating protein folding, trafficking, and degradation. Notably, polyQ proteins can disrupt the PQC system by sequestering its critical components and impairing its proteasomal functions. Therefore, restoring the PQC system through genetic or pharmacological interventions could potentially offer beneficial effects and alleviate the symptoms of the disease. Here, we will provide a review on the distribution, expression, and genetic or pharmacological intervention of protein quality control system in cellular or animal models of PolyQ SCAs.

Specific Biomarkers in Spinocerebellar Ataxia Type 3: A Systematic Review of Their Potential Uses in Disease Staging and Treatment Assessment

Spinocerebellar ataxia type 3 (SCA3) is the most common type of disease related to poly-glutamine (polyQ) repeats. Its hallmark pathology is related to the abnormal accumulation of ataxin 3 with a longer polyQ tract (polyQ-ATXN3). However, there are other mechanisms related to SCA3 progression that require identifying trait and state biomarkers for a more accurate diagnosis and prognosis. Moreover, the identification of potential pharmacodynamic targets and assessment of therapeutic efficacy necessitates valid biomarker profiles. The aim of this review was to identify potential trait and state biomarkers and their potential value in clinical trials. Our results show that, in SCA3, there are different fluid biomarkers involved in neurodegeneration, oxidative stress, metabolism, miRNA and novel genes. However, neurofilament light chain NfL and polyQ-ATXN3 stand out as the most prevalent in body fluids and SCA3 stages. A heterogeneity analysis of NfL revealed that it may be a valuable state biomarker, particularly when measured in plasma. Nonetheless, since it could be a more beneficial approach to tracking SCA3 progression and clinical trial efficacy, it is more convenient to perform a biomarker profile evaluation than to rely on only one.

Digital Gait Measures Capture 1-Year Progression in Early-Stage Spinocerebellar Ataxia Type 2

BACKGROUND

With disease-modifying drugs in reach for cerebellar ataxias, fine-grained digital health measures are highly warranted to complement clinical and patient-reported outcome measures in upcoming treatment trials and treatment monitoring. These measures need to demonstrate sensitivity to capture change, in particular in the early stages of the disease.

OBJECTIVE

Our aim is to unravel gait measures sensitive to longitudinal change in the-particularly trial-relevant-early stage of spinocerebellar ataxia type 2 (SCA2).

METHODS

We performed a multicenter longitudinal study with combined cross-sectional and 1-year interval longitudinal analysis in early-stage SCA2 participants (n = 23, including nine pre-ataxic expansion carriers; median, ATXN2 CAG repeat expansion 38 ± 2; median, Scale for the Assessment and Rating of Ataxia [SARA] score 4.8 ± 4.3). Gait was assessed using three wearable motion sensors during a 2-minute walk, with analyses focused on gait measures of spatio-temporal variability that have shown sensitivity to ataxia severity (eg, lateral step deviation).

RESULTS

We found significant changes for gait measures between baseline and 1-year follow-up with large effect sizes (lateral step deviation P = 0.0001, effect size rprb = 0.78), whereas the SARA score showed no change (P = 0.67). Sample size estimation indicates a required cohort size of n = 43 to detect a 50% reduction in natural progression. Test-retest reliability and minimal detectable change analysis confirm the accuracy of detecting 50% of the identified 1-year change.

CONCLUSIONS

Gait measures assessed by wearable sensors can capture natural progression in early-stage SCA2 within just 1 year-in contrast to a clinical ataxia outcome. Lateral step deviation represents a promising outcome measure for upcoming multicenter interventional trials, particularly in the early stages of cerebellar ataxia. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

ATXN7-Related Cone-Rod Dystrophy: The Integrated Functional Evaluation of the Cerebellum (CERMOI) Study

Importance

Reliable biomarkers with diagnostic and prognostic values are needed for upcoming gene therapy trials for spinocerebellar ataxias.

Objective

To identify ophthalmological biomarkers in a sample of spinocerebellar ataxia type 7 (SCA7) carriers.

Design, Setting, and Participants

This article presents baseline data from a cross-sectional natural history study conducted in Paris, France, reference centers for rare diseases from May 2020 to April 2021. Data were analyzed from September to December 2022. Fifteen adult ATXN7 pathogenic expansion carriers (9 with preataxia and 6 with ataxia) were included, all with a Scale for the Assessment and Rating of Ataxia (SARA) score of 15 of 40 or lower. Patients were recruited at the Paris Brain Institute, and all contacted patients accepted to participate in the study.

Main Outcomes and Measures

Three visits (baseline, 6 months, and 12 months) were planned, including neurological examination (SARA and Composite Cerebellar Functional Severity Score), ophthalmological examination (best-corrected visual acuity, microperimetry, full-field electroretinogram, optical coherence tomography, and fundus autofluorescence imaging), and neurofilament light chain (NfL) measurements. Here we report the baseline ophthalmic data from the cohort and determine whether there is a correlation between disease scores and ophthalmic results.

Results

Among the 15 included SCA7 carriers (median [range] age, 38 [18-60] years; 8 women and 7 men), 12 displayed cone or cone-rod dystrophy, with the number of CAG repeats correlating with disease severity (ρ, 0.73, 95% CI, 0.34 to 0.90; P < .001). Two patients with cone-rod dystrophy exhibited higher repeat numbers and greater ataxia scores (median [range] SARA score, 9 [7-15]) compared to those with only cone dystrophy (median [range] SARA score, 2 [0-5]). A correlation emerged for outer nuclear layer thickness with SARA score (ρ, -0.88; 95% CI, -0.96 to -0.59; P < .001) and NfL levels (ρ, -0.87; 95% CI, -0.86 to 0.96; P < .001). Moreover, ataxia severity was correlated with visual acuity (ρ: 0.89; 95% CI, 0.68 to 0.96; P < .001) and retinal sensitivity (ρ, -0.88; 95% CI, -0.96 to 0.59; P < .001).

Conclusions and Relevance

In this cross-sectional study, retinal abnormalities were found at preataxic stages of the disease. Most of the carriers presented with cone dystrophy and preserved rod function. The outer nuclear layer thickness correlated with SARA score and plasma NfL levels suggesting nuclear layer thickness to be a biomarker of disease severity. These findings contribute to understanding the dynamics of SCA7-related retinal dystrophy and may help lay the groundwork for future therapeutic intervention monitoring and clinical trials.

Trial Registration

ClinicalTrials.gov Identifier: NCT04288128.

[Recent clinical advances in hereditary spinocerebellar degeneration]

Spinocerebellar degeneration (SCD) is a neurodegenerative disorder characterized by cerebellar ataxia and other multisystem manifestations, such as Parkinsonism and pyramidal tract symptoms. No effective treatment is available for SCD. Approximately one-third of the cases of SCD are inherited, and the remaining two-third are sporadic, including multiple system atrophy. This article provides an overview of hereditary SCD, its clinical features, recent treatment advances, biomarkers, role of genomic medicine, and future treatment prospects.

Rates of change of pons and middle cerebellar peduncle diameters are diagnostic of multiple system atrophy of the cerebellar type

Definitive diagnosis of multiple system atrophy of the cerebellar type (MSA-C) is challenging. We hypothesized that rates of change of pons and middle cerebellar peduncle diameters on MRI would be unique to MSA-C and serve as diagnostic biomarkers. We defined the normative data for anterior-posterior pons and transverse middle cerebellar peduncle diameters on brain MRI in healthy controls, performed diameter-volume correlations and measured intra- and inter-rater reliability. We studied an Exploratory cohort (2002-2014) of 88 MSA-C and 78 other cerebellar ataxia patients, and a Validation cohort (2015-2021) of 49 MSA-C, 13 multiple system atrophy of the parkinsonian type (MSA-P), 99 other cerebellar ataxia patients and 314 non-ataxia patients. We measured anterior-posterior pons and middle cerebellar peduncle diameters on baseline and subsequent MRIs, and correlated results with Brief Ataxia Rating Scale scores. We assessed midbrain:pons and middle cerebellar peduncle:pons ratios over time. The normative anterior-posterior pons diameter was 23.6 ± 1.6 mm, and middle cerebellar peduncle diameter 16.4 ± 1.4 mm. Pons diameter correlated with volume, r = 0.94, P < 0.0001. The anterior-posterior pons and middle cerebellar peduncle measures were smaller at first scan in MSA-C compared to all other ataxias; anterior-posterior pons diameter: Exploratory, 19.3 ± 2.6 mm versus 20.7 ± 2.6 mm, Validation, 19.9 ± 2.1 mm versus 21.1 ± 2.1 mm; middle cerebellar peduncle transverse diameter, Exploratory, 12.0 ± 2.6 mm versus 14.3 ±2.1 mm, Validation, 13.6 ± 2.1 mm versus 15.1 ± 1.8 mm, all P < 0.001. The anterior-posterior pons and middle cerebellar peduncle rates of change were faster in MSA-C than in all other ataxias; anterior-posterior pons diameter rates of change: Exploratory, -0.87 ± 0.04 mm/year versus -0.09 ± 0.02 mm/year, Validation, -0.89 ± 0.48 mm/year versus -0.10 ± 0.21 mm/year; middle cerebellar peduncle transverse diameter rates of change: Exploratory, -0.84 ± 0.05 mm/year versus -0.08 ± 0.02 mm/year, Validation, -0.94 ± 0.64 mm/year versus -0.11 ± 0.27 mm/year, all values P < 0.0001. Anterior-posterior pons and middle cerebellar peduncle diameters were indistinguishable between Possible, Probable and Definite MSA-C. The rate of anterior-posterior pons atrophy was linear, correlating with ataxia severity. Using a lower threshold anterior-posterior pons diameter decrease of -0.4 mm/year to balance sensitivity and specificity, area under the curve analysis discriminating MSA-C from other ataxias was 0.94, yielding sensitivity 0.92 and specificity 0.87. For the middle cerebellar peduncle, with threshold decline -0.5 mm/year, area under the curve was 0.90 yielding sensitivity 0.85 and specificity 0.79. The midbrain:pons ratio increased progressively in MSA-C, whereas the middle cerebellar peduncle:pons ratio was almost unchanged. Anterior-posterior pons and middle cerebellar peduncle diameters were smaller in MSA-C than in MSA-P, P < 0.001. We conclude from this 20-year longitudinal clinical and imaging study that anterior-posterior pons and middle cerebellar peduncle diameters are phenotypic imaging biomarkers of MSA-C. In the correct clinical context, an anterior-posterior pons and transverse middle cerebellar peduncle diameter decline of ∼0.8 mm/year is sufficient for and diagnostic of MSA-C.

Stage-Dependent Biomarker Changes in Spinocerebellar Ataxia Type 3

Spinocerebellar ataxia type 3/Machado-Joseph disease is the most common autosomal dominant ataxia. In view of the development of targeted therapies, knowledge of early biomarker changes is needed. We analyzed cross-sectional data of 292 spinocerebellar ataxia type 3/Machado-Joseph disease mutation carriers. Blood concentrations of mutant ATXN3 were high before and after ataxia onset, whereas neurofilament light deviated from normal 13.3 years before onset. Pons and cerebellar white matter volumes decreased and deviated from normal 2.2 years and 0.6 years before ataxia onset. We propose a staging model of spinocerebellar ataxia type 3/Machado-Joseph disease that includes a biomarker stage characterized by objective indicators of neurodegeneration before ataxia onset. ANN NEUROL 2024;95:400-406.

Association Between Serum Neurofilament Light Chain and Neurochemistry Deficits in Patients with Spinocerebellar Ataxia Type 3

Extensive evidence supports the claim that the serum neurofilament light chain (sNfL) can be used as a biomarker to monitor disease severity in patients with spinocerebellar ataxia type 3 (SCA3). However, little is known about the associations between sNfL levels and neurochemical alterations in SCA3 patients. In this study, we performed a cross-sectional study to analyze the association between sNfL and brain metabolic changes in SCA3 patients. The severity of ataxia was assessed by using the Scale for the Assessment and Rating of Ataxia (SARA) and the International Cooperative Ataxia Rating Scale (ICARS). The sNfL levels and brain metabolic changes, represented by N-acetyl aspartate (NAA)/creatine (Cr) and choline complex (Cho)/Cr ratios, were measured by a single-molecule array and proton magnetic resonance spectroscopy, respectively. In this cohort, we observed consistently elevated sNfL levels and reduced brain metabolites in the cerebellar hemispheres, dentate nucleus, and cerebellar vermis. However, this correlation was further validated in the cerebellar cortex after analysis using pairwise comparisons and a Bonferroni correction. Taken together, our results further confirmed that sNfL levels were increased in SCA3 patients and were negatively correlated with metabolic changes in the cerebellar cortex. Our data also support the idea that sNfL levels are a promising potential complementary biomarker for patients with SCA3.

Clinical stage and plasma neurofilament concentration in adults with Friedreich ataxia

Objectives

Friedreich Ataxia (FRDA) is the most common recessive ataxia disorder. Yet, little is known of the prevalence in Sweden. In the future, there may be effective disease-modifying therapies, and use of clinical rating scales as well as possible biomarkers in serum or cerebrospinal fluid may be of importance. We evaluated the axonal protein neurofilament light in plasma (p-NfL) as a possible biomarker for disease severity in FRDA.

Materials & methods

We searched for all possible genetically confirmed FRDA cases in the Västra Götaland Region (VGR) of Sweden, and investigated each patient clinically and obtained blood sample for analysis of p-NfL.

Results

We found eight patients corresponding to 1/170.000 adults in the VGR, and 5 of these participated in the study. Three out of the five FRDA patients displayed a small or moderate increase in the p-NfL value, compared to the age-adjusted cut-offs for p-NfL established in the Clinical Neurochemistry Laboratory at our hospital. The two others were the oldest and most severely affected, displayed normal values according the cut-off values. The cohort is too small to make any statistically significant correlation between the five p-NfL values with regard to disease severity.

Conclusions

FRDA is less prevalent in our region of Sweden than could be assumed. In concordance with previous studies from other authors, we find that p-NfL may be increased in patients with FRDA, but less so in older more clinically affected patients. Thus, we conclude that on an individual basis, p-NFL is of uncertain clinical value as a suitable biomarker.

On the Cut-Off Value of the Anteroposterior Diameter of the Midbrain Atrophy in Spinocerebellar Ataxia Type 2 Patients

(1) Background: Spinocerebellar ataxias (SCA) is a term that refers to a group of hereditary ataxias, which are neurological diseases characterized by degeneration of the cells that constitute the cerebellum. Studies suggest that magnetic resonance imaging (MRI) supports diagnoses of ataxias, and linear measurements of the aneteroposterior diameter of the midbrain (ADM) have been investigated using MRI. These measurements correspond to studies in spinocerebellar ataxia type 2 (SCA2) patients and in healthy subjects. Our goal was to obtain the cut-off value for ADM atrophy in SCA2 patients. (2) Methods: This study evaluated 99 participants (66 SCA2 patients and 33 healthy controls). The sample was divided into estimations (80%) and validation (20%) samples. Using the estimation sample, we fitted a logistic model using the ADM and obtained the cut-off value through the inverse of regression. (3) Results: The optimal cut-off value of ADM was found to be 18.21 mm. The area under the curve (AUC) of the atrophy risk score was 0.957 (95% CI: 0.895-0.991). Using this cut-off on the validation sample, we found a sensitivity of 100.00% (95% CI: 76.84%-100.00%) and a specificity of 85.71% (95% CI: 42.13%-99.64%). (4) Conclusions: We obtained a cut-off value that has an excellent discriminatory capacity to identify SCA2 patients.

Serum Neurofilament Light Chain in Replication Factor Complex Subunit 1 CANVAS and Disease Spectrum

BACKGROUND

Biallelic intronic AAGGG repeat expansions in the replication factor complex subunit 1 (RFC1) gene were identified as the leading cause of cerebellar ataxia, neuropathy, vestibular areflexia syndrome. Patients exhibit significant clinical heterogeneity and variable disease course, but no potential biomarker has been identified to date.

OBJECTIVES

In this multicenter cross-sectional study, we aimed to evaluate neurofilament light (NfL) chain serum levels in a cohort of RFC1 disease patients and to correlate NfL serum concentrations with clinical phenotype and disease severity.

METHODS

Sixty-one patients with genetically confirmed RFC1 disease and 48 healthy controls (HCs) were enrolled from six neurological centers. Serum NfL concentration was measured using the single molecule array assay technique.

RESULTS

Serum NfL concentration was significantly higher in patients with RFC1 disease compared to age- and-sex-matched HCs (P < 0.0001). NfL level showed a moderate correlation with age in both HCs (r = 0.4353, P = 0.0020) and patients (r = 0.4092, P = 0.0011). Mean NfL concentration appeared to be significantly higher in patients with cerebellar involvement compared to patients without cerebellar dysfunction (27.88 vs. 21.84 pg/mL, P = 0.0081). The association between cerebellar involvement and NfL remained significant after controlling for age and sex (β = 0.260, P = 0.034).

CONCLUSIONS

Serum NfL levels are significantly higher in patients with RFC1 disease compared to HCs and correlate with cerebellar involvement. Longitudinal studies are warranted to assess its change over time.

The S-Factor, a New Measure of Disease Severity in Spinocerebellar Ataxia: Findings and Implications

Spinocerebellar ataxias (SCAs) are progressive neurodegenerative disorders, but there is no metric that predicts disease severity over time. We hypothesized that by developing a new metric, the Severity Factor (S-Factor) using immutable disease parameters, it would be possible to capture disease severity independent of clinical rating scales. Extracting data from the CRC-SCA and READISCA natural history studies, we calculated the S-Factor for 438 participants with symptomatic SCA1, SCA2, SCA3, or SCA6, as follows: ((length of CAG repeat expansion - maximum normal repeat length) /maximum normal repeat length) × (current age - age at disease onset) × 10). Within each SCA type, the S-Factor at the first Scale for the Assessment and Rating of Ataxia (SARA) visit (baseline) was correlated against scores on SARA and other motor and cognitive assessments. In 281 participants with longitudinal data, the slope of the S-Factor over time was correlated against slopes of scores on SARA and other motor rating scales. At baseline, the S-Factor showed moderate-to-strong correlations with SARA and other motor rating scales at the group level, but not with cognitive performance. Longitudinally the S-Factor slope showed no consistent association with the slope of performance on motor scales. Approximately 30% of SARA slopes reflected a trend of non-progression in motor symptoms. The S-Factor is an observer-independent metric of disease burden in SCAs. It may be useful at the group level to compare cohorts at baseline in clinical studies. Derivation and examination of the S-factor highlighted challenges in the use of clinical rating scales in this population.

Cerebrospinal fluid neurofilament light and cerebral atrophy in younger-onset dementia and primary psychiatric disorders

BACKGROUND AND AIMS

Neurodegeneration underpins the pathological processes of younger-onset dementia (YOD) and has been implicated in primary psychiatric disorders (PSYs). Cerebrospinal fluid (CSF) neurofilament light (NfL) has been used to investigate neurodegeneration severity through correlation with structural brain changes in various conditions, but has seldom been evaluated in YOD and PSYs.

METHODS

This retrospective study included patients with YOD or PSYs with magnetic resonance imaging (MRI) of the brain and CSF NfL analysis. Findings from brain MRI were analysed using automated volumetry (volBrain) to measure white matter (WM), grey matter (GM) and whole brain (WB) volumes expressed as percentages of total intracranial volume. Correlations between NfL and brain volume measurements were computed whilst adjusting for age.

RESULTS

Seventy patients (47 with YOD and 23 with PSY) were identified. YOD types included Alzheimer disease and behavioural variant frontotemporal dementia. PSY included schizophrenia and major depressive disorder. MRI brain sequences were either fast spoiler gradient-echo (FSPGR) or magnetization-prepared rapid acquisition gradient-echo (MPRAGE). In the total cohort, higher NfL was associated with reduced WB in the FSPGR and MPRAGE sequences (r = -0.402 [95% confidence interval (CI), -0.593 to -0.147], P = 0.008 and r = -0.625 [95% CI, -0.828 to -0.395], P < 0.001, respectively). Higher NfL was related to reduced GM in FSPGR (r = 0.385 [95% CI, -0.649 to -0.014], P = 0.017) and reduced WM in MPRAGE (r = -0.650 [95% CI, -0.777 to -0.307], P < 0.001). Similar relationships were seen in YOD, but not in PSY.

CONCLUSION

Higher CSF NfL is related to brain atrophy in YOD, further supporting its use as a nonspecific marker of neurodegeneration severity.

Blood levels of neurofilament light are associated with disease progression in a mouse model of spinocerebellar ataxia type 3

Increased neurofilament light (NfL; NEFL) protein in biofluids is reflective of neurodegeneration and has gained interest as a biomarker across neurodegenerative diseases. In spinocerebellar ataxia type 3 (SCA3), the most common dominantly inherited ataxia, patients exhibit progressive NfL increases in peripheral blood when becoming symptomatic, and NfL remains stably elevated throughout further disease course. However, progressive NfL changes are not yet validated in relevant preclinical SCA3 animal models, hindering its application as a biomarker during therapeutic development. We used ultra-sensitive single-molecule array (Simoa) to measure blood NfL over disease progression in YACQ84 mice, a model of SCA3, assessing relationships with measures of disease severity including age, CAG repeat size and magnetic resonance spectroscopy. YACQ84 mice exhibited plasma NfL increases that were concomitant with ataxia-related motor deficits as well as increased serum NfL, which correlated with previously established neurometabolite abnormalities, two relevant measures of disease in patients with SCA3. Our findings establish the progression of NfL increases in the preclinical YACQ84 mouse, further supporting the utility of blood NfL as a peripheral neurodegeneration biomarker and informing on coinciding timelines of different measures of SCA3 pathogenesis.

Autosomal dominant cerebellar ataxias: new genes and progress towards treatments

Dominantly inherited spinocerebellar ataxias (SCAs) are associated with phenotypes that range from pure cerebellar to multisystemic. The list of implicated genes has lengthened in the past 5 years with the inclusion of SCA37/DAB1, SCA45/FAT2, SCA46/PLD3, SCA47/PUM1, SCA48/STUB1, SCA50/NPTX1, SCA25/PNPT1, SCA49/SAM9DL, and SCA27B/FGF14. In some patients, co-occurrence of multiple potentially pathogenic variants can explain variable penetrance or more severe phenotypes. Given this extreme clinical and genetic heterogeneity, genome sequencing should become the diagnostic tool of choice but is still not available in many clinical settings. Treatments tested in phase 2 and phase 3 studies, such as riluzole and transcranial direct current stimulation of the cerebellum and spinal cord, have given conflicting results. To enable early intervention, preataxic carriers of pathogenic variants should be assessed with biomarkers, such as neurofilament light chain and brain MRI; these biomarkers could also be used as outcome measures, given that clinical outcomes are not useful in the preataxic phase. The development of bioassays measuring the concentration of the mutant protein (eg, ataxin-3) might facilitate monitoring of target engagement by gene therapies.

Stage-dependent biomarker changes in spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3) is the most common autosomal dominant ataxia. In view of the development of targeted therapies for SCA3, precise knowledge of stage-dependent fluid and MRI biomarker changes is needed. We analyzed cross-sectional data of 292 SCA3 mutation carriers including 57 pre-ataxic individuals, and 108 healthy controls from the European Spinocerebellar ataxia type 3/Machado-Joseph Disease Initiative (ESMI) cohort. Blood concentrations of mutant ATXN3 and neurofilament light (NfL) were determined, and volumes of pons, cerebellar white matter (CWM) and cerebellar grey matter (CGM) were measured on MRI. Mutant ATXN3 concentrations were high before and after ataxia onset, while NfL continuously increased and deviated from normal 11.9 years before onset. Pons and CWM volumes decreased, but the deviation from normal was only 2.0 years (pons) and 0.3 years (CWM) before ataxia onset. We propose a staging model of SCA3 that includes an initial asymptomatic carrier stage followed by the biomarker stage defined by absence of ataxia, but a significant rise of NfL. The biomarker stage leads into the ataxia stage, defined by manifest ataxia. The present analysis provides a robust framework for further studies aiming at elaboration and differentiation of the staging model of SCA3.

Baseline Clinical and Blood Biomarkers in Patients With Preataxic and Early-Stage Disease Spinocerebellar Ataxia 1 and 3

BACKGROUND AND OBJECTIVES

In spinocerebellar ataxia, ataxia onset can be preceded by mild clinical manifestation, cerebellar and/or brainstem alterations, or biomarker modifications. READISCA is a prospective, longitudinal observational study of patients with spinocerebellar ataxia type 1 (SCA1) and 3 (SCA3) to provide essential markers for therapeutic interventions. We looked for clinical, imaging, or biological markers that are present at an early stage of the disease.

METHODS

We enrolled carriers of a pathologic ATXN1 or ATXN3 expansion and controls from 18 US and 2 European ataxia referral centers. Clinical, cognitive, quantitative motor, neuropsychological measures and plasma neurofilament light chain (NfL) measurements were compared between expansion carriers with and without ataxia and controls.

RESULTS

We enrolled 200 participants: 45 carriers of a pathologic ATXN1 expansion (31 patients with ataxia [median Scale for the Assessment and Rating of Ataxia: 9; 7-10] and 14 expansion carriers without ataxia [1; 0-2]) and 116 carriers of a pathologic ATXN3 expansion (80 patients with ataxia [7; 6-9] and 36 expansion carriers without ataxia [1; 0-2]). In addition, we enrolled 39 controls who did not carry a pathologic expansion in ATXN1 or ATXN3. Plasma NfL levels were significantly higher in expansion carriers without ataxia than controls, despite similar mean age (controls: 5.7 pg/mL, SCA1: 18.0 pg/mL [p < 0.0001], SCA3: 19.8 pg/mL [p < 0.0001]). Expansion carriers without ataxia differed from controls by significantly more upper motor signs (SCA1 p = 0.0003, SCA3 p = 0.003) and by the presence of sensor impairment and diplopia in SCA3 (p = 0.0448 and 0.0445, respectively). Functional scales, fatigue and depression scores, swallowing difficulties, and cognitive impairment were worse in expansion carriers with ataxia than those without ataxia. Ataxic SCA3 participants showed extrapyramidal signs, urinary dysfunction, and lower motor neuron signs significantly more often than expansion carriers without ataxia.

DISCUSSION

READISCA showed the feasibility of harmonized data acquisition in a multinational network. NfL alterations, early sensory ataxia, and corticospinal signs were quantifiable between preataxic participants and controls. Patients with ataxia differed in many parameters from controls and expansion carriers without ataxia, with a graded increase of abnormal measures from control to preataxic to ataxic cohorts.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov NCT03487367.

Head-to-head comparison of 6 plasma biomarkers in early multiple system atrophy

There is a dire need for reliable biomarkers to solidify an early and accurate diagnosis of multiple system atrophy (MSA). We sought to compare the ability of emerging plasma markers in distinguishing MSA from its mimics and healthy controls in early disease stages, and to evaluate their performance in detecting disease severity and brain atrophy. Plasma neurofilament light (NfL), glial fibrillary acidic protein (GFAP), phosphorylated tau181, amyloid-β (Aβ)42, and Aβ40 were measured using ultrasensitive Simoa in early-stage patients with MSA (n = 73), spinocerebellar ataxia (SCA, n = 29), Parkinson's disease (PD, n = 28), and healthy controls (n = 100). We observed that elevated NfL outperformed other biomarkers in distinguishing MSA and its subtypes (AUC = 0.9) versus controls. Intriguingly, when separating MSA from its mimics, increased GFAP (AUC = 0.717) in MSA-C and decreased Aβ40 (AUC = 0.807) in MSA-P best discriminated from SCA and PD respectively. Plasma levels were comparable between MSA-C and MSA-P and the differentiation by plasma index alone was poor. Combining plasma markers noticeably improved the discriminatory efficacy. Of note, among MSA patients, higher GFAP and NfL were correlated with the atrophy of brain regions vulnerable to MSA (e.g., cerebellum, pons, or putamen). They could also aggravate the severity of MSA, and this association was partially mediated by cerebral volumes. In contrast, no obvious associations of phosphorylated tau and Aβ with disease severity were observed. Collectively, plasma biomarkers, especially in combination, are useful to facilitate the discriminatory work-up of MSA at early stages. Moreover, NfL and GFAP may be promising biomarkers to monitor the disease severity of MSA.

TR-FRET-Based Immunoassay to Measure Ataxin-2 as a Target Engagement Marker in Spinocerebellar Ataxia Type 2

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominantly inherited neurodegenerative disease, which belongs to the trinucleotide repeat disease group with a CAG repeat expansion in exon 1 of the ATXN2 gene resulting in an ataxin-2 protein with an expanded polyglutamine (polyQ)-stretch. The disease is late manifesting leading to early death. Today, therapeutic interventions to cure the disease or even to decelerate disease progression are not available yet. Furthermore, primary readout parameter for disease progression and therapeutic intervention studies are limited. Thus, there is an urgent need for quantifiable molecular biomarkers such as ataxin-2 becoming even more important due to numerous potential protein-lowering therapeutic intervention strategies. The aim of this study was to establish a sensitive technique to measure the amount of soluble polyQ-expanded ataxin-2 in human biofluids to evaluate ataxin-2 protein levels as prognostic and/or therapeutic biomarker in SCA2. Time-resolved fluorescence energy transfer (TR-FRET) was used to establish a polyQ-expanded ataxin-2-specific immunoassay. Two different ataxin-2 antibodies and two different polyQ-binding antibodies were validated in three different concentrations and tested in cellular and animal tissue as well as in human cell lines, comparing different buffer conditions to evaluate the best assay conditions. We established a TR-FRET-based immunoassay for soluble polyQ-expanded ataxin-2 and validated measurements in human cell lines including iPSC-derived cortical neurons. Additionally, our immunoassay was sensitive enough to monitor small ataxin-2 expression changes by siRNA or starvation treatment. We successfully established the first sensitive ataxin-2 immunoassay to measure specifically soluble polyQ-expanded ataxin-2 in human biomaterials.

Blood neurofilament light chain levels are associated with disease progression in a transgenic SCA3 mouse model

Increased neurofilament light (NfL) protein in biofluids is reflective of neurodegeneration and has gained interest as a biomarker across neurodegenerative diseases. In spinocerebellar ataxia type 3 (SCA3), the most common dominantly inherited ataxia, patients exhibit progressive NfL increases in peripheral blood when becoming symptomatic, remaining stably elevated throughout further disease course. However, progressive NfL changes are not yet validated in relevant preclinical SCA3 animal models, hindering its application as a biomarker during therapeutic development. We used ultra-sensitive single-molecule array (Simoa) to measure blood NfL over disease progression in the YACQ84 mouse, assessing relationships with measures of disease severity including age, CAG repeat size, and magnetic resonance spectroscopy. We show that YACQ84 mice exhibit increased blood NfL, concomitant with ataxia-related motor deficits and correlated with neurometabolite abnormalities. Our findings establish natural history progression of NfL increases in the preclinical YACQ84 mouse, further supporting the utility of blood NfL as a peripheral neurodegeneration biomarker and informing coinciding timelines of different measures of SCA3 pathogenesis.

Summary statement

Peripheral blood of SCA3 YACQ84 mice exhibits increased abundance of neuronal-specific NfL protein directly associating with disease progression, providing an accessible disease biofluid biomarker to interrogate in preclinical therapeutic studies.

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.

Tau and neurofilament light-chain as fluid biomarkers in spinocerebellar ataxia type 3

BACKGROUND AND PURPOSE

Clinical trials in spinocerebellar ataxia type 3 (SCA3) will require biomarkers for use as outcome measures.

METHODS

To evaluate total tau (t-tau), glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase L1 (UCHL1) and neurofilament light-chain (NfL) as fluid biomarkers in SCA3, ATXN3 mutation carriers (n = 143) and controls (n = 172) were clinically assessed, and the plasma concentrations of the four proteins were analysed on the Simoa HD-1 platform. Eleven ATXN3 mutation carrier cerebrospinal fluid samples were analysed for t-tau and phosphorylated tau (p-tau¹⁸¹ ). A transgenic SCA3 mouse model (MJDTg) was used to measure cerebellar t-tau levels.

RESULTS

Plasma t-tau levels were higher in mutation carriers below the age of 50 compared to controls, and the Inventory of Non-Ataxia Signs was associated with t-tau in ataxic patients (p = 0.004). Pre-ataxic carriers showed higher cerebrospinal fluid t-tau and p-tau¹⁸¹ concentrations compared to ataxic patients (p = 0.025 and p = 0.014, respectively). Cerebellar t-tau was elevated in MJDTg mice compared to wild-type (p = 0.033) only in the early stages of the disease. GFAP and UCHL1 did not show higher levels in mutation carriers compared to controls. Plasma NfL concentrations were higher in mutation carriers compared to controls, and differences were greater for younger carriers. The Scale for the Assessment and Rating of Ataxia was the strongest predictor of NfL in ataxic patients (p < 0.001).

CONCLUSION

Our results suggest that tau might be a marker of early disease stages in SCA3. NfL can discriminate mutation carriers from controls and is associated with different clinical variables. Longitudinal studies are required to confirm their potential role as biomarkers in clinical trials.

Levels of Neurofilament Light at the Preataxic and Ataxic Stages of Spinocerebellar Ataxia Type 1

BACKGROUND AND OBJECTIVES

Neurofilament light (NfL) appears to be a promising fluid biomarker in repeat-expansion spinocerebellar ataxias (SCAs), with piloting studies in mixed SCA cohorts suggesting that NfL might be increased at the ataxic stage of SCA type 1 (SCA1). We here hypothesized that NfL is increased not only at the ataxic stage of SCA1, but also at its (likely most treatment-relevant) preataxic stage.

METHODS

We assessed serum NfL (sNfL) and CSF NfL (cNfL) levels in both preataxic and ataxic SCA1, leveraging a multicentric cohort recruited at 6 European university centers, and clinical follow-up data, including actually observed (rather than only predicted) conversion to the ataxic stage. Levels of sNfL and cNfL were assessed by single-molecule array and ELISA technique, respectively.

RESULTS

Forty individuals with SCA1 (23 preataxic, 17 ataxic) and 89 controls were enrolled, including 11 preataxic individuals converting to the ataxic stage. sNfL levels were increased at the preataxic (median 15.5 pg/mL [interquartile range 10.5-21.1 pg/mL]) and ataxic stage (31.6 pg/mL [26.2-37.7 pg/mL]) compared to controls (6.0 pg/mL [4.7-8.6 pg/mL]), yielding high age-corrected effect sizes (preataxic: r = 0.62, ataxic: r = 0.63). sNfL increases were paralleled by increases of cNfL at both the preataxic and ataxic stage. In preataxic individuals, sNfL levels increased with proximity to predicted ataxia onset, with significant sNfL elevations already 5 years before onset, and confirmed in preataxic individuals with actually observed ataxia onset. sNfL increases were detected already in preataxic individuals with SCA1 without volumetric atrophy of cerebellum or pons, suggesting that sNfL might be more sensitive to early preataxic neurodegeneration than the currently known most change-sensitive regions in volumetric MRI. Using longitudinal sNfL measurements, we estimated sample sizes for clinical trials with the reduction of sNfL as the endpoint.

DISCUSSION

sNfL levels might provide easily accessible peripheral biomarkers in both preataxic and ataxic SCA1, allowing stratification of preataxic individuals regarding proximity to onset, early detection of neurodegeneration even before volumetric MRI alterations, and potentially capture of treatment response in clinical trials.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov Identifier: NCT01037777.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that NfL levels are increased in both ataxic and preataxic SCA1 and are associated with ataxia onset.

Plasma Neurofilament Light Chain Levels Are Elevated in Children and Young Adults With Wolfram Syndrome

Wolfram syndrome is a rare disease caused by pathogenic variants in the WFS1 gene with progressive neurodegeneration. As an easily accessible biomarker of progression of neurodegeneration has not yet been found, accurate tracking of the neurodegenerative process over time requires assessment by costly and time-consuming clinical measures and brain magnetic resonance imaging (MRI). A blood-based measure of neurodegeneration, neurofilament light chain (NfL), is relatively inexpensive and can be repeatedly measured at remote sites, standardized, and measured in individuals with MRI contraindications. To determine whether NfL levels may be of use in disease monitoring and reflect disease activity in Wolfram syndrome, plasma NfL levels were compared between children and young adults with Wolfram syndrome (n = 38) and controls composed of their siblings and parents (n = 35) and related to clinical severity and selected brain region volumes within the Wolfram group. NfL levels were higher in the Wolfram group [median (interquartile range) NfL = 11.3 (7.8-13.9) pg/mL] relative to controls [5.6 (4.5-7.4) pg/mL]. Within the Wolfram group, higher NfL levels related to worse visual acuity, color vision and smell identification, smaller brainstem and thalamic volumes, and faster annual rate of decrease in thalamic volume over time. Our findings suggest that plasma NfL levels can be a powerful tool to non-invasively assess underlying neurodegenerative processes in children, adolescents and young adults with Wolfram syndrome.

IGF-1 as a Potential Therapy for Spinocerebellar Ataxia Type 3

Although the effects of growth hormone (GH) therapy on spinocerebellar ataxia type 3 (SCA3) have been examined in transgenic SCA3 mice, it still poses a nonnegligible risk of cancer when used for a long term. This study investigated the efficacy of IGF-1, a downstream mediator of GH, in vivo for SCA3 treatment. IGF-1 (50 mg/kg) or saline, once a week, was intraperitoneally injected to SCA3 84Q transgenic mice harboring a human ATXN3 gene with a pathogenic expanded 84 cytosine–adenine–guanine (CAG) repeat motif at 9 months of age. Compared with the control mice harboring a 15 CAG repeat motif, the SCA3 84Q mice treated with IGF-1 for 9 months exhibited the improvement only in locomotor function and minimized degeneration of the cerebellar cortex as indicated by the survival of more Purkinje cells with a more favorable mitochondrial function along with a decrease in oxidative stress caused by DNA damage. These findings could be attributable to the inhibition of mitochondrial fission, resulting in mitochondrial fusion, and decreased immunofluorescence staining in aggresome formation and ataxin-3 mutant protein levels, possibly through the enhancement of autophagy. The findings of this study show the therapeutic potential effect of IGF-1 injection for SCA3 to prevent the exacerbation of disease progress.

Association of the Level of Neurofilament Light With Disease Severity in Patients With Spinocerebellar Ataxia Type 2

BACKGROUND AND OBJECTIVES

Few biochemical markers have been identified in spinocerebellar ataxia type 2 (SCA2). This study aimed to determine the levels of neurofilament light (NfL) in patients with SCA2 and identify whether they were associated with disease severity.

METHODS

Participants were recruited from one medical center in China, and individuals with SCA2 were genetically diagnosed. NfL levels were assessed using the single molecule array method. Disease severity was evaluated using the Scale for the Assessment and Rating of Ataxia (SARA), the International Cooperative Ataxia Rating Scale (ICARS), and the Inventory of Non-Ataxia Symptoms (INAS). Cerebellum and brainstem volumes were calculated using neuroimaging measurements. We used Pearson's correlation and partial correlation for correlation analyses.

RESULTS

Forty-nine manifest patients with SCA2, 10 preclinical individuals with SCA2 and 92 controls were enrolled. A high consistency was identified between serum and CSF NfL (r = 0.868, p < 0.0001). In individuals with SCA2, levels of serum NfL were associated with disease severity (SARA, r = 0.425, p = 0.003; ICARS, r = 0.383, p = 0.009; INAS, r = 0.390, p = 0.007; cerebellum volume, r = - 0.393, p = 0.024) after adjustment for age. NfL levels were higher close to the expected age of onset in preclinical individuals with SCA2 (R ² = 0.43, p = 0.04).

DISCUSSION

Levels of serum NfL were correlated with disease intensity in individuals with SCA2, and were higher close to the estimated age of onset in preclinical SCA2. Therefore, NfL is a potential serum biomarker of disease severity in SCA2.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that elevated NfL levels are associated with disease severity in individuals with SCA2.

Neurofilament Proteins as Biomarkers to Monitor Neurological Diseases and the Efficacy of Therapies

Biomarkers of neurodegeneration and neuronal injury have the potential to improve diagnostic accuracy, disease monitoring, prognosis, and measure treatment efficacy. Neurofilament proteins (NfPs) are well suited as biomarkers in these contexts because they are major neuron-specific components that maintain structural integrity and are sensitive to neurodegeneration and neuronal injury across a wide range of neurologic diseases. Low levels of NfPs are constantly released from neurons into the extracellular space and ultimately reach the cerebrospinal fluid (CSF) and blood under physiological conditions throughout normal brain development, maturation, and aging. NfP levels in CSF and blood rise above normal in response to neuronal injury and neurodegeneration independently of cause. NfPs in CSF measured by lumbar puncture are about 40-fold more concentrated than in blood in healthy individuals. New ultra-sensitive methods now allow minimally invasive measurement of these low levels of NfPs in serum or plasma to track disease onset and progression in neurological disorders or nervous system injury and assess responses to therapeutic interventions. Any of the five Nf subunits - neurofilament light chain (NfL), neurofilament medium chain (NfM), neurofilament heavy chain (NfH), alpha-internexin (INA) and peripherin (PRPH) may be altered in a given neuropathological condition. In familial and sporadic Alzheimer's disease (AD), plasma NfL levels may rise as early as 22 years before clinical onset in familial AD and 10 years before sporadic AD. The major determinants of elevated levels of NfPs and degradation fragments in CSF and blood are the magnitude of damaged or degenerating axons of fiber tracks, the affected axon caliber sizes and the rate of release of NfP and fragments at different stages of a given neurological disease or condition directly or indirectly affecting central nervous system (CNS) and/or peripheral nervous system (PNS). NfPs are rapidly emerging as transformative blood biomarkers in neurology providing novel insights into a wide range of neurological diseases and advancing clinical trials. Here we summarize the current understanding of intracellular NfP physiology, pathophysiology and extracellular kinetics of NfPs in biofluids and review the value and limitations of NfPs and degradation fragments as biomarkers of neurodegeneration and neuronal injury.

Blood Neurofilament Light Chain in Genetic Ataxia: A Meta-Analysis

BACKGROUND

No comprehensive meta-analysis has ever been performed to assess the value of neurofilament light chain (NfL) as a biomarker in genetic ataxia.

OBJECTIVE

We conducted a meta-analysis to summarize NfL concentration and evaluate its utility as a biomarker in genetic ataxia.

METHODS

Studies were included if they reported NfL concentration of genetic ataxia. We used log (mean ± SD) NfL to describe mean raw value of NfL. The effect size of NfL between genetic ataxia and healthy controls (HC) was expressed by mean difference. Correlation between NfL and disease severity was calculated.

RESULTS

We identified 11 studies of 624 HC and 1006 patients, here referred to as spinocerebellar ataxia (SCA1, 2, 3, 6, and 7), Friedreich ataxia (FRDA), and ataxia telangiectasia (A-T). The concentration of blood NfL (bNfL) elevated with proximity to expected onset, and progressively increased from asymptomatic to preclinical to clinical stage in SCA3. Compared with HC, bNfL levels were significantly higher in SCA1, 2, 3, and 7, FRDA, as well as A-T, and the difference increased with the advancing disease in SCA3. bNfL levels correlated with disease severity in SCA3. There was a significant correlation between bNfL and longitudinal progression in SCA3. Additionally, bNfL increased with age in HC, yet this is probably masked by higher disease-related effects on bNfL in genetic ataxia.

CONCLUSIONS

bNfL can be used as a potential biomarker to predict disease onset, severity, and progression of genetic ataxia. Reference-value setting of bNfL should be divided according to age. © 2021 International Parkinson and Movement Disorder Society.

MicroRNAs in Huntington's Disease: Diagnostic Biomarkers or Therapeutic Agents?

MicroRNA (miRNA) is a non-coding single-stranded small molecule of approximately 21 nucleotides. It degrades or inhibits the translation of RNA by targeting the 3′-UTR. The miRNA plays an important role in the growth, development, differentiation, and functional execution of the nervous system. Dysregulated miRNA expression has been associated with several pathological processes of neurodegenerative disorders, including Huntington’s disease (HD). Recent studies have suggested promising roles of miRNAs as biomarkers and potential therapeutic targets for HD. Here, we review the emerging role of dysregulated miRNAs in HD and describe general biology of miRNAs, their pathophysiological implications, and their potential roles as biomarkers and therapeutic agents.

Blood-Based Markers of Neuronal Injury in Adult-Onset Myotonic Dystrophy Type 1

INTRODUCTION

The present study had four aims. First, neuronal injury markers, including neurofilament light (NF-L), total tau, glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase (UCH-L1), were compared between individuals with and without adult-onset myotonic dystrophy type 1 (DM1). Second, the impact of age and CTG repeat on brain injury markers was evaluated. Third, change in brain injury markers across the study period was quantified. Fourth, associations between brain injury markers and cerebral white matter (WM) fractional anisotropy (FA) were identified.

METHODS

Yearly assessments, encompassing blood draws and diffusion tensor imaging on a 3T scanner, were conducted on three occasions. Neuronal injury markers were quantified using single molecule array (Simoa).

RESULTS

The sample included 53 patients and 70 controls. NF-L was higher in DM1 patients than controls, with individuals in the premanifest phases of DM1 (PreDM1) exhibiting intermediate levels ( χ ( 2 ) 2 = 38.142, P < 0.001). Total tau was lower in DM1 patients than controls (Estimate = -0.62, 95% confidence interval [CI] -0.95: -0.28, P < 0.001), while GFAP was elevated in PreDM1 only (Estimate = 30.37, 95% CI 10.56:50.19, P = 0.003). Plasma concentrations of UCH-L1 did not differ between groups. The age by CTG interaction predicted NF-L: patients with higher estimated progenitor allelege length (ePAL) had higher NF-L at a younger age, relative to patients with lower CTG repeat; however, the latter exhibited faster age-related change (Estimate = -0.0021, 95% CI -0.0042: -0.0001, P = 0.045). None of the markers changed substantially over the study period. Finally, cerebral WM FA was significantly associated with NF-L (Estimate = -42.86, 95% CI -82.70: -3.02, P = 0.035).

INTERPRETATION

While NF-L appears sensitive to disease onset and severity, its utility as a marker of progression remains to be determined. The tau assay may have low sensitivity to tau pathology associated with DM1.