CSF protein biomarkers for proximal axonal damage improve prognostic accuracy in the acute phase of Guillain-Barré syndrome

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.

Factors Associated with Respiratory Insufficiency in Children with Guillain-Barré Syndrome

OBJECTIVE

 The risk factors for respiratory insufficiency in children with Guillain-Barré syndrome (GBS) are poorly known. This study aimed to investigate the factors associated with respiratory insufficiency in children with GBS.

METHODS

 This retrospective study included children diagnosed with GBS by pediatric neurologists and admitted at the Wuhan Children's Hospital and other hospitals from January 2013 to October 2022. The patients were divided into the respiratory insufficiency and nonrespiratory insufficiency groups according to whether they received assist breathing during treatment.

RESULTS

 The median (interquartile range) age of onset of 103 patients were 5 (3.1-8.5) years, 69 (67%) were male, and 64 (62.1%) had a history of precursor infection. Compared with the nonrespiratory insufficiency group, the respiratory insufficiency group showed more facial and/or bulbar weakness (p = 0.002), a higher Hughes Functional Grading Scale (HFGS) at admission (p < 0.001), and a shorter onset-to-admission interval (p = 0.017). Compared with the acute motor axonal neuropathy (AMAN) subtype, the acute inflammatory demyelinating polyneuropathy (AIDP) subtype showed longer days from onset to lumbar (p = 0.000), lower HFGS at admission (p = 0.04), longer onset-to-admission interval (p = 0.001), and more cranial nerve involvement (p = 0.04). The incidence of respiratory insufficiency between AIDP and AMAN showed no statistical difference (p > 0.05).

CONCLUSION

 In conclusion, facial and/or bulbar weakness, HFGS at admission, and onset-to-admission interval were associated with respiratory insufficiency and might be useful prognostic markers in children with GBS.

Dynamics and prognostic value of serum neurofilament light chain in Guillain-Barré syndrome

BACKGROUND

Neurofilament light chain (NfL) is a biomarker for axonal damage in several neurological disorders. We studied the longitudinal changes in serum NfL in patients with Guillain-Barré syndrome (GBS) in relation to disease severity, electrophysiological subtype, treatment response, and prognosis.

METHODS

We included patients with GBS who participated in a double-blind, randomised, placebo-controlled trial that evaluated the effects of a second course of intravenous immunoglobulin (IVIg) on clinical outcomes. Serum NfL levels were measured before initiation of treatment and at one, two, four, and twelve weeks using a Simoa HD-X Analyzer. Serum NfL dynamics were analysed using linear mixed-effects models. Logistic regression was employed to determine the associations of serum NfL with clinical outcome and the prognostic value of serum NfL after correcting for known prognostic markers included in the modified Erasmus GBS Outcome Score (mEGOS).

FINDINGS

NfL levels were tested in serum from 281 patients. Serum NfL dynamics were associated with disease severity and electrophysiological subtype. Strong associations were found between high levels of serum NfL at two weeks and inability to walk unaided at four weeks (OR = 1.74, 95% CI = 1.27-2.45), and high serum NfL levels at four weeks and inability to walk unaided at 26 weeks (OR = 2.79, 95% CI = 1.72-4.90). Baseline serum NfL had the most significant prognostic value for ability to walk, independent of predictors included in the mEGOS. The time to regain ability to walk unaided was significantly longer for patients with highest serum NfL levels at baseline (p = 0.0048) and week 2 (p < 0.0001). No differences in serum NfL were observed between patients that received a second IVIg course vs. IVIg and placebo.

INTERPRETATION

Serum NfL levels are associated with disease severity, axonal involvement, and poor outcome in GBS. Serum NfL potentially represents a biomarker to monitor neuronal damage in GBS and an intermediate endpoint to evaluate the effects of treatment.

FUNDING

Prinses Beatrix Spierfonds W.OR19-24.

Mechanisms underlying HIV-associated cognitive impairment and emerging therapies for its management

People living with HIV are affected by the chronic consequences of neurocognitive impairment (NCI) despite antiretroviral therapies that suppress viral replication, improve health and extend life. Furthermore, viral suppression does not eliminate the virus, and remaining infected cells may continue to produce viral proteins that trigger neurodegeneration. Comorbidities such as diabetes mellitus are likely to contribute substantially to CNS injury in people living with HIV, and some components of antiretroviral therapy exert undesirable side effects on the nervous system. No treatment for HIV-associated NCI has been approved by the European Medicines Agency or the US Food and Drug Administration. Historically, roadblocks to developing effective treatments have included a limited understanding of the pathophysiology of HIV-associated NCI and heterogeneity in its clinical manifestations. This heterogeneity might reflect multiple underlying causes that differ among individuals, rather than a single unifying neuropathogenesis. Despite these complexities, accelerating discoveries in HIV neuropathogenesis are yielding potentially druggable targets, including excessive immune activation, metabolic alterations culminating in mitochondrial dysfunction, dysregulation of metal ion homeostasis and lysosomal function, and microbiome alterations. In addition to drug treatments, we also highlight the importance of non-pharmacological interventions. By revisiting mechanisms implicated in NCI and potential interventions addressing these mechanisms, we hope to supply reasons for optimism in people living with HIV affected by NCI and their care providers.

Increasing Neuroinflammation Relates to Increasing Neurodegeneration in People with HIV

BACKGROUND

HIV infection causes neuroinflammation and immune activation (NIIA) and systemic inflammation and immune activation (SIIA), which in turn drive neurodegeneration (ND). Cross-sectionally, higher levels of NIIA biomarkers correlate with increased biomarkers of ND. A more convincing confirmation would be a longitudinal demonstration.

METHODS

PWH in the US multisite CHARTER Aging project were assessed at a baseline visit and after 12 years using standardized evaluations. We measured a panel of 14 biomarkers of NIIA, SIIA, and ND in plasma and CSF at two time points and calculated changes from baseline to the 12-year visit. Factor analysis yielded simplified indices of NIIA, SIIA, and ND.

RESULTS

The CSF NIIA factor analysis yielded Factor1 loading on soluble tumor necrosis factor type-2 (sTNFR-II) and neopterin, and Factor2, loading on MCP1, soluble CD14, and IL-6. The SIIA factor analysis yielded Factor1 loading on CRP, D-dimer, and Neopterin; Factor2 loading on sTNFR-II. The ND analysis yielded Factor1 loading on Phosphorylated tau (p-tau) and Aβ42; Factor2 loading on NFL. NIIA Factor1, but not Factor2, correlated with increases in CSF NFL (r = 0.370, p = 0.0002).

CONCLUSIONS

Increases in NIIA and SIIA in PWH were associated with corresponding increases in ND, suggesting that reducing neuro/systemic inflammation might slow or reverse neurodegeneration.

Emerging biomarkers to predict clinical outcomes in Guillain-Barré syndrome

INTRODUCTION

Guillain-Barré syndrome (GBS) is an immune-mediated poly(radiculo)neuropathy with a variable clinical outcome. Identifying patients who are at risk of suffering from long-term disabilities is a great challenge. Biomarkers are useful to confirm diagnosis, monitor disease progression, and predict outcome.

AREAS COVERED

The authors provide an overview of the diagnostic and prognostic biomarkers for GBS, which are useful for establishing early treatment strategies and follow-up care plans.

EXPERT OPINION

Detecting patients at risk of developing a severe outcome may improve management of disease progression and limit potential complications. Several clinical factors are associated with poor prognosis: higher age, presence of diarrhea within 4 weeks of symptom onset, rapid and severe weakness progression, dysautonomia, decreased vital capacity and facial, bulbar, and neck weakness. Biological, neurophysiological and imaging measures of unfavorable outcome include multiple anti-ganglioside antibodies elevation, increased serum and CSF neurofilaments light (NfL) and heavy chain, decreased NfL CSF/serum ratio, hypoalbuminemia, nerve conduction study with early signs of demyelination or axonal loss and enlargement of nerve cross-sectional area on ultrasound. Depicting prognostic biomarkers aims at predicting short-term mortality and need for cardio-pulmonary support, long-term patient functional outcome, guiding treatment decisions and monitoring therapeutic responses in future clinical trials.

Higher Levels of Cerebrospinal Fluid and Plasma Neurofilament Light in Human Immunodeficiency Virus-Associated Distal Sensory Polyneuropathy

BACKGROUND

Neurofilament light (NFL) chain concentrations, reflecting axonal damage, are seen in several polyneuropathies but have not been studied in human immunodeficiency virus (HIV) distal sensory polyneuropathy (DSP). We evaluated NFL in cerebrospinal fluid (CSF) and plasma in relation to DSP in people with HIV (PWH) from 2 independent cohorts and in people without HIV (PWoH).

METHODS

Cohort 1 consisted of PWH from the CHARTER Study. Cohort 2 consisted of PWH and PWoH from the HIV Neurobehavioral Research Center (HNRC). We evaluated DSP signs and symptoms in both cohorts. Immunoassays measured NFL in CSF for all and for plasma as well in Cohort 2.

RESULTS

Cohort 1 consisted of 111 PWH, mean ± SD age 56.8 ± 8.32 years, 15.3% female, 38.7% Black, 49.6% White, current CD4+ T-cells (median, interquartile range [IQR]) 532/µL (295, 785), 83.5% with plasma HIV RNA ≤50 copies/mL. Cohort 2 consisted of 233 PWH of similar demographics to PWH in Cohort 1 but also 51 PWoH, together age 58.4 ± 6.68 years, 41.2% female, 18.0% Black, Hispanic, non-Hispanic White 52.0%, 6.00% White. In both cohorts of PWH, CSF and plasma NFL were significantly higher in both PWH with DSP signs. Findings were similar, albeit not significant, for PWoH. The observed relationships were not explained by confounds.

CONCLUSIONS

Both plasma and CSF NFL were elevated in PWH and PWoH with DSP. The convergence of our findings with others demonstrates that NFL is a reliable biomarker reflecting peripheral nerve injury. Biomarkers such as NFL might provide, validate, and optimize clinical trials of neuroregenerative strategies in HIV DSP.

The 2022 Lady Estelle Wolfson lectureship on neurofilaments

Neurofilament proteins (Nf) have been validated and established as a reliable body fluid biomarker for neurodegenerative pathology. This review covers seven Nf isoforms, Nf light (NfL), two splicing variants of Nf medium (NfM), two splicing variants of Nf heavy (NfH), α -internexin (INA) and peripherin (PRPH). The genetic and epigenetic aspects of Nf are discussed as relevant for neurodegenerative diseases and oncology. The comprehensive list of mutations for all Nf isoforms covers Amyotrophic Lateral Sclerosis, Charcot-Marie Tooth disease, Spinal muscular atrophy, Parkinson Disease and Lewy Body Dementia. Next, emphasis is given to the expanding field of post-translational modifications (PTM) of the Nf amino acid residues. Protein structural aspects are reviewed alongside PTMs causing neurodegenerative pathology and human autoimmunity. Molecular visualisations of NF PTMs, assembly and stoichiometry make use of Alphafold2 modelling. The implications for Nf function on the cellular level and axonal transport are discussed. Neurofilament aggregate formation and proteolytic breakdown are reviewed as relevant for biomarker tests and disease. Likewise, Nf stoichiometry is reviewed with regard to in vitro experiments and as a compensatory mechanism in neurodegeneration. The review of Nf across a spectrum of 87 diseases from all parts of medicine is followed by a critical appraisal of 33 meta-analyses on Nf body fluid levels. The review concludes with considerations for clinical trial design and an outlook for future research.

Neurofilament light chain and total tau in the differential diagnosis and prognostic evaluation of acute and chronic inflammatory polyneuropathies

Background and Purpose

To investigate the diagnostic and prognostic value of axonal injury biomarkers in patients with inflammatory polyneuropathies.

Methods

Neurofilament light chain (NfL) and total tau (T‐tau) were measured in the cerebrospinal fluid (CSF) and plasma in 41 patients with Guillain–Barré syndrome (GBS), 32 patients with chronic inflammatory demyelinating polyneuropathy (CIDP), 10 with paraproteinemia‐related demyelinating polyneuropathy (PDN), and 8 with multifocal motor neuropathy (MMN), in comparison with 39 disease‐free controls and 59 other controls. Outcome was measured with the GBS‐disability score (GBS‐ds) or Inflammatory Neuropathy Cause and Treatment (INCAT) disability score.

Results

Neurofilament light chain levels in CSF and plasma were higher in GBS, CIDP, and PDN vs. disease‐free controls. Patients with MMN had higher NfL levels in plasma vs. disease‐free controls, but lower levels in CSF and plasma vs. patients with amyotrophic lateral sclerosis (ALS).

T‐tau levels in plasma were higher in GBS, CIDP, PDN, and MMN vs. all control groups.

Neurofilament light chain levels in CSF and plasma in patients with GBS correlated with GBS‐ds, as higher levels were associated with inability to run after 6 and 12 months. NfL levels in CSF and plasma in CIDP did not correlate significantly with outcome.

Conclusions

Acute and chronic inflammatory neuropathies are associated with an increase in levels of NfL in CSF and plasma, but NfL is validated as a prognostic biomarker only in GBS. NfL could be used in differentiating patients with MMN from ALS. T‐tau in plasma is a novel biomarker that could be used in a diagnostic assessment of patients with acute and chronic inflammatory polyneuropathies.

Fluid Biomarkers for Monitoring Structural Changes in Polyneuropathies: Their Use in Clinical Practice and Trials

Reliable and responsive tools for monitoring disease activity and treatment outcomes in patients with neuropathies are lacking. With the emergence of ultrasensitive blood bioassays, proteins released with nerve damage are potentially useful response biomarkers for many neurological disorders, including polyneuropathies. In this review, we provide an overview of the existing literature focusing on potential applications in polyneuropathy clinical care and trials. Whilst several promising candidates have been identified, no studies have investigated if any of these proteins can serve as response biomarkers of longitudinal disease activity, except for neurofilament light (NfL). For NfL, limited evidence exists supporting a role as a response biomarker in Guillain-Barré syndrome, vasculitic neuropathy, and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Most evidence exists for NfL as a response biomarker in hereditary transthyretin-related amyloidosis (hATTR). At the present time, the role of NfL is therefore limited to a supporting clinical tool or exploratory endpoint in trials. Future developments will need to focus on the discovery of additional biomarkers for anatomically specific and other forms of nerve damage using high-throughput technologies and highly sensitive analytical platforms in adequality powered studies of appropriate design. For NfL, a better understanding of cut-off values, the relation to clinical symptoms and long-term disability as well as dynamics in serum on and off treatment is needed to further expand and proceed towards implementation.

Case Report: Plasma Biomarkers Reflect Immune Mechanisms of Guillain-Barré Syndrome

This case series reported a group of patients with Guillain–Barré syndrome (GBS) and their plasma cytokine changes before and after immunotherapy. We aimed to understand GBS's pathogenesis and pathophysiology through observing the interval differences of the representative cytokines, which were the thymus and activation regulated chemokine (TARC) for T-cell chemotaxis, CD40 ligand (CD40L) for cosimulation of B and T cells, activated complement component C5/C5a, and brain-derived neurotrophic factor (BDNF) for survival and regenerative responses to nerve injuries. The fluorescence magnetic bead-based multiplexing immunoassay simultaneously quantified the five cytokines in a single sample. From June 2018 to December 2019, we enrolled five GBS patients who had completed before–after blood cytokine measurements. One patient was diagnosed with paraneoplastic GBS and excluded from the following cytokine analysis. The BDNF level decreased consistently in all the patients and made it a potential biomarker for the acute stage of GBS. Interval changes of the other four cytokines were relatively inconsistent and possibly related to interindividual differences in the immune response to GBS triggers, types of GBS variants, and classes of antiganglioside antibodies. In summary, utilizing the multiplexing immunoassay helps in understanding the complex immune mechanisms of GBS and the variation of immune responses in GBS subtypes; this method is feasible for identifying potential biomarkers of GBS.

CSF Diagnostics: A Potentially Valuable Tool in Neurodegenerative and Inflammatory Disorders Involving Motor Neurons: A Review

Cerebrospinal fluid (CSF) diagnostics has emerged as a valid tool for a variety of neurological diseases. However, CSF diagnostics has been playing a subordinate role in the diagnosis of many neurological conditions. Thus, in the multitude of neuromuscular diseases in which motor neurons are affected, a CSF sample is rarely taken routinely. However, CSF diagnostics has the potential to specify the diagnosis and monitor the treatment of neuromuscular disorders. In this review, we therefore focused on a variety of neuromuscular diseases, among them amyotrophic lateral sclerosis (ALS), peripheral neuropathies, and spinal muscular atrophy (SMA), for which CSF diagnostics has emerged as a promising option for determining the disease itself and its progression. We focus on potentially valuable biomarkers among different disorders, such as neurofilaments, cytokines, other proteins, and lipids to determine their suitability, differentiating between different neurological disorders and their potential to determine early disease onset, disease progression, and treatment outcome. We further recommend novel approaches, e.g., the use of mass spectrometry as a promising alternative techniques to standard ELISA assays, potentially enhancing biomarker significance in clinical applications.

Cerebrospinal Fluid Protein Level and Mechanical Ventilation in Guillain-Barré Syndrome patients

The prognostic value of cerebrospinal fluid (CSF) protein in Guillain Barré Syndrome (GBS) is unclear. We aimed to explore the potential association between CSF protein level and mechanical ventilation in GBS. We undertook a retrospective study of GBS patients from January 2000 to November 2019 at the University of Michigan. 94 patients were ultimately included for evaluation. After adjusting for the Erasmus GBS Respiratory Insufficiency Scale (EGRIS), we did not find a significant difference in CSF protein between ventilated and non-ventilated patients. Elevated CSF protein level does not appear to portend an increased likelihood of mechanical ventilation in GBS patients.

Comprehensive approaches for diagnosis, monitoring and treatment of chronic inflammatory demyelinating polyneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is the most common chronic inflammatory neuropathy. CIDP is diagnosed according to the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) criteria, which combine clinical features with the electrophysiological evidence of demyelination. However, firstly, diagnosis is challenging, as some patients e.g. with severe early axonal damage do not fulfil the criteria. Secondly, objective and reliable tools to monitor the disease course are lacking. Thirdly, about 25% of CIDP patients do not respond to evidence-based first-line therapy. Recognition of these patients is difficult and treatment beyond first-line therapy is based on observational studies and case series only. Individualized immunomodulatory treatment does not exist due to the lack of understanding of essential aspects of the underlying pathophysiology.

Novel diagnostic imaging techniques and molecular approaches can help to solve these problems but do not find enough implementation. This review gives a comprehensive overview of novel diagnostic techniques and monitoring approaches for CIDP and how these can lead to individualized treatment and better understanding of pathophysiology.

Serum neurofilament light chain predicts long-term prognosis in Guillain-Barré syndrome patients

OBJECTIVE

To study baseline serum neurofilament light chain (sNfL) levels as a prognostic biomarker in Guillain-Barré syndrome (GBS).

METHODS

We measured NfL in serum (98 samples) and cerebrospinal fluid (CSF) (24 samples) of patients with GBS prospectively included in the International GBS Outcome Study (IGOS) in Spain using single-molecule array (SiMoA) and compared them with 53 healthy controls (HCs). We performed multivariable regression to analyse the association between sNfL levels and functional outcome at 1 year.

RESULTS

Patients with GBS had higher NfL levels than HC in serum (55.49 pg/mL vs 9.83 pg/mL, p<0.0001) and CSF (1308.5 pg/mL vs 440.24 pg/mL, p=0.034). Patients with preceding diarrhoea had higher sNfL than patients with respiratory symptoms or no preceding infection (134.90 pg/mL vs 47.86 pg/mL vs 38.02 pg/mL, p=0.016). sNfL levels correlated with Guillain-Barré Syndrome Disability Score and Inflammatory Rasch-built Overall Disability Scale (I-RODS) at every timepoint. Patients with pure motor variant and Miller Fisher syndrome showed higher sNfL levels than patients with sensorimotor GBS (162.18 pg/mL vs 95.50 pg/mL vs 38.02 pg/mL, p=0.025). Patients with acute motor axonal neuropathy cute motor axonal neuropathy had higher sNfL levels than other variants (190.55 pg/mL vs 46.79 pg/mL, p=0.013). sNfL returned to normal levels at 1 year. High baseline sNfL levels were associated with inability to run (OR=1.65, 95% CI 1.14 to 2.40, p=0.009) and lower I-RODS (β -2.60, 95% CI -4.66 to -0.54, p=0.014) at 1 year. Cut-off points predicting clinically relevant outcomes at 1 year with high specificity were calculated: inability to walk independently (>319 pg/mL), inability to run (>248 pg/mL) and ability to run (<34 pg/mL).

CONCLUSION

Baseline sNfL levels are increased in patients with GBS, are associated with disease severity and axonal variants and have an independent prognostic value in patients with GBS.

Ratio and index of Neurofilament light chain indicate its origin in Guillain-Barré Syndrome

Objective

Neurofilament light chain (NfL) has been established as a biomarker of axonal damage in many diseases of the central nervous system (CNS). Increased levels of serum NfL (sNfL) can derive as well from damage in the peripheral nervous system (PNS) as from CNS, but little is known about the quantities contributing to sNfL. Peripheral nerve damage may be reflected by an increase in sNfL levels, while the NfL CSF/serum ratio and NfL index decreases.

Methods

We collected serum and cerebrospinal fluid (CSF) from 21 Guillain‐Barré Syndrome (GBS) patients and measured NfL in serum and CSF and compared them with 19 neurologically healthy controls.

Results

In general, NfL in CSF and serum was significantly higher in GBS patients. Serum NfL was higher in GBS patients admitted to the intensive care unit (P = 0.02). Controls had a mean CSF/serum NfL ratio of 26.7 (ranging from 5.8 to 69.5) indicating a central origin of NfL. Three GBS patients had a similar range (23.9 to 42.7, mean 33.3) all of them with demyelinating pathology in the PNS. Eighteen GBS patients with axonal or mixed axonal‐demyelinating pathology showed significantly lower CSF/serum ratios (0.02–12.2, mean 4.4), indicative of a peripheral origin of NfL. When applying the NfL index subdivisions remain the same.

Interpretation

These results demonstrate that the PNS is a relevant contributor to sNfL levels and that the distribution can be identified by a lowered NfL CSF/serum ratio of NfL index. Furthermore, acute or subacute polyneuropathies are likely confounding factors in interpreting sNfL levels in CNS diseases.

CSF Neurofilament Light Chain Elevation Predicts ALS Severity and Progression

Objectives: This study compared neurofilament light chain (NFL) levels in the cerebrospinal fluid (CSF) of patients with sporadic amyotrophic lateral sclerosis (sALS) with levels in patients with other neurological diseases and healthy controls and assessed correlations between NFL levels and clinical indicators of sALS.

Methods: We used enzyme-linked immunosorbent assays to determine the NFL levels in the CSF of 45 patients with sALS, 21 patients with other central nervous system diseases (OCNSDs), 18 with immune-mediated peripheral neuropathy (IMPN), 14 with non-immune-mediated peripheral neuropathy (NIMPN), and 19 healthy controls (HCs).

Results: The median NFL levels in the CSF of the sALS, OCNSD, IMPN, NIMPN, and HC groups were 6510, 5372, 4320, 1477, and 756 pg/mL, respectively. The CSF NFL levels did not differ significantly among the sALS, IMPN, and OCNSD groups, but were significantly higher than those of the NIMPN and HC groups. The NFL CSF levels were significantly higher in the NIMPN group than the HCs. There was a negative correlation between the NFL level and ALS function score (ALSFRS-R), and a positive correlation with the disease progression rate in patients with sALS.

Conclusion: CSF NFL may not be sufficient to distinguish ALS from other central nervous system diseases or peripheral neuropathy, but it predicts ALS severity and progression.

[The prognosis and prognostic factor of Guillain-Barré Syndrome]

Guillain-Barré Syndrome (GBS) is an acute monophasic immune-mediated neuropathy, generally considered to be of good prognosis. However, 15-20% of GBS patients cannot walk independently at six months from onset. Poor prognostic factors for long-term functional disability included old age, preceding diarrhea, muscle weakness on admission and on day 7 from admission, severe GBS disability score at two weeks from admission and IgG antibody against GD1a/GD1b ganglioside complex. Factors related with requirement of mechanical ventilation included the time from onset to admission <7 days, muscle weakness on admission, facial and/or bulbar weakness and IgG antibody against GQ1b. Recently modified Erasmus GBS outcome score (mEGOS) and Erasmus GBS respiratory insufficiency score (EGRIS) were reported as prognostic factors for the long-term functional disability and respiratory insufficiency. Those were designed on Dutch patients. The usefulness of these tools in Japan or other countries remained unknown. The authors validated mEGOS and EGRIS on Japanese GBS patients in Japanese GBS outcome study, which revealed that these tools were also adaptable on Japanese GBS patients. To identify clinical and biological factors of GBS in more detail, such a large scale prospective study as International GBS outcome study (IGOS) is warranted.

Neurofilament light protein levels in cerebrospinal fluid predict long-term disability of Guillain-Barré syndrome: A pilot study

OBJECTIVES

Although the recovery from Guillain-Barré syndrome (GBS) is good in most patients, some develop permanent severe disability or even die. Early predictors would increase the likelihood to identify patients at risk for poor outcome at the acute stage, allowing them intensified therapeutic intervention.

MATERIALS AND METHOD

Eighteen patients with a history of GBS 9-17 years ago were reassessed with scoring of neurological disability and quality of life assessment (QoL). Their previous diagnostic work-up included clinical examination with scoring of disability, neurophysiological investigation, a battery of serology tests for infections, and cerebrospinal fluid (CSF) examination. Aliquots of CSF were frozen, stored for 20-28 years, and analyzed by ELISA for determination of neurofilament light protein (NFL) and glial fibrillary acidic protein (GFAP).

RESULTS

Patients with poor outcome (n = 3) had significantly higher NFL and GFAP levels at GBS nadir than those with good outcome (n = 15, P < .01 and P < .05, respectively). High NFL correlated with more prominent disability and worse QoL at long-term follow-up (r = .694, P < .001, and SF 36 dimension physical component summary (PCS) (r =-.65, P < .05), respectively, whereas GFAP did not correlate with clinical outcome or QoL.

CONCLUSION

High NFL in CSF at the acute stage of GBS seems to predict long-term outcome and might, together with neurophysiological and clinical measures, be useful in treatment decisions and clinical care of GBS.

Cerebrospinal fluid findings in Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathies

The classic immunologic alteration of the cerebrospinal fluid (CSF) in Guillain-Barré syndrome (GBS), albuminocytologic dissociation, has been known since the original paper by Guillain, Barré, and Strohl. Albuminocytologic dissociation has been also described in other forms of the GBS spectrum, such as axonal motor or motor-sensory forms (AMAN, AMSAN), the anti-GQ1b spectrum of Miller Fisher syndrome, and Bickerstaff brainstem encephalitis. Cytokines, chemokines, antibodies, complement components, and molecules with a putative neuroprotective role or indicating axonal damage have also been examined using different methods. Besides these candidate approaches, proteomics has been recently applied to discover potential biomarkers. The overall results support the immunopathogenesis of GBS, but albuminocytologic dissociation remained the only consistent CSF biomarker supporting the diagnosis of GBS. Chronic inflammatory neuropathies also comprise a heterogeneous group of diseases. Increased protein in the CSF is a supportive factor of chronic inflammatory demyelinating polyneuropathy, especially in the absence of definite electrophysiologic criteria. A number of other markers have also been investigated in the CSF of patients with chronic inflammatory neuropathies, similar to GBS. However, none has been used in supporting diagnosis, differentiating among syndromes, or predicting the clinical course and treatment responses.

Validation of a multiplexing technique to determine the intrathecal, polyspecific antiviral immune response in multiple sclerosis

BACKGROUND

Beside the determination of oligoclonal bands (OCBs) as a diagnostic biomarker in multiple sclerosis (MS), the presence of an intrathecal production of antibodies against the neurotropic viruses measles (M), rubella (R) and Varicella-Zoster (Z), the so called MRZ reaction (MRZR) is an even more specific diagnostic biomarker in MS.

METHODS

We compared and validated the determination of the MRZR in 97 cerebrospinal fluid (CSF) and serum sample pairs of a bead-based multiplexing technique and a classical enzyme-linked immunosorbent assay (ELISA).

RESULTS

Conformity of 94% (M), 94% (R), 94% (Z), 96% (H) and 97% for the interpretation of the MRZR was obtained.

CONCLUSION

Based on our findings of high conformity between the multiplex technique and classical ELISA, as well as the time and cost savings multiplexing allows, we conclude that the multiplexing technique is applicable as a diagnostic tool for the determination of the MRZR.

Neurofilament Light Chain Determination from Peripheral Blood Samples

The loss of neurological function is closely related to axonal damage. Neurofilament subunits are concentrated in neurons and axons and have emerged as promising biomarkers for neurodegeneration. Electrochemiluminescence (ECL) based assays are known to be of superior sensitivity and require less sample volume than conventional ELISAs. Here, we describe a highly sensitive ECL based immunoassay for quantification of neurofilament light chain (NfL) in blood and CSF.

Inflammatory neuropathies: pathology, molecular markers and targets for specific therapeutic intervention

Inflammatory neuropathies encompass groups of heterogeneous disorders characterized by pathogenic immune-mediated hematogenous leukocyte infiltration of peripheral nerves, nerve roots or both, with resultant demyelination or axonal degeneration or both. Inflammatory neuropathies may be divided into three major disease categories: Guillain-Barré syndrome (particularly the acute inflammatory demyelinating polyradiculoneuropathy variant), chronic inflammatory demyelinating polyradiculoneuropathy and nonsystemic vasculitic neuropathy (or peripheral nerve vasculitis). Despite major advances in molecular biology, pathology and genetics, the pathogenesis of these disorders remains elusive. There is insufficient knowledge on the mechanisms of hematogenous leukocyte trafficking into the peripheral nervous system to guide the development of specific molecular therapies for immune-mediated inflammatory neuropathies compared to disorders such as psoriasis, inflammatory bowel disease, rheumatoid arthritis or multiple sclerosis. The recent isolation and characterization of human endoneurial endothelial cells that form the blood-nerve barrier provides an opportunity to elucidate leukocyte-endothelial cell interactions critical to the pathogenesis of inflammatory neuropathies at the interface between the systemic circulation and peripheral nerve endoneurium. This review discusses our current knowledge of the classic pathological features of inflammatory neuropathies, attempts at molecular classification and genetic determinants, the utilization of in vitro and in vivo animal models to determine pathogenic mechanisms at the interface between the systemic circulation and the peripheral nervous system relevant to these disorders and prospects for future potential molecular pathology biomarkers and targets for specific therapeutic intervention.

Association of ubiquitin carboxy-terminal hydrolase-L1 in cerebrospinal fluid with clinical severity in a cohort of patients with Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an acute immune-mediated polyneuropathy. Although its pathogenic mechanism has been revealed and various therapeutic trials have been performed, a proportion of patients experience the severe sequelae associated with GBS. In this paper, we investigated whether the amount of the neuron-specific protein, ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1), in the cerebrospinal fluid of patients with GBS was correlated with the clinical course of the disease. UCH-L1 protein levels were greater in patients with GBS than in controls. The patients with GBS whose UCH-L1 protein levels were higher than those of the controls presented with more severe symptoms at peak. UCH-L1 protein levels tended to become elevated as the total protein levels were increased; however, elevated UCH-L1 without an increase in total protein might be correlated with severe disease course (bedridden or ventilator supported). These results suggest that UCH-L1 could be a biomarker associated with the severity of the disease at the acute phase of GBS.

Pure sensory Guillain-Barré syndrome: A case report and review of the literature

Sensory Guillain-Barré syndrome (GBS) is an acute demyelinating neuropathy that presents clinically with involvement of the sensory peripheral nerve only. To date, <10 cases of pure sensory GBS have been reported; thus, the clinical and pathological features of sensory variant GBS are yet to be well characterized. The current study reports the case of a 43-year-old female that presented with acute, symmetric and monophasic sensory neuropathy, without motor weakness. Patient history, clinical examination, routine nerve conduction studies and sural nerve biopsy were reviewed. All the observations were consistent with a diagnosis of pure sensory GBS. In particular, the pathological features of the sural nerve biopsy revealed that the form of regenerated nerve fibers have complete structure of myelinated nerve fascicles, and these myelinated nerve fibers are thicker than other parts of the biopsy. The patient received small-dose (20 mg/day) prednisone initially, but without any benefit. Satisfactory improvements were observed with one course of intravenous immunoglobulin.

Increased neurofilament light chain blood levels in neurodegenerative neurological diseases

Objective

Neuronal damage is the morphological substrate of persisting neurological disability. Neurofilaments (Nf) are cytoskeletal proteins of neurons and their release into cerebrospinal fluid has shown encouraging results as a biomarker for neurodegeneration. This study aimed to validate the quantification of the Nf light chain (NfL) in blood samples, as a biofluid source easily accessible for longitudinal studies.

Methods

We developed and applied a highly sensitive electrochemiluminescence (ECL) based immunoassay for quantification of NfL in blood and CSF.

Results

Patients with Alzheimer’s disease (AD) (30.8 pg/ml, n=20), Guillain-Barré-syndrome (GBS) (79.4 pg/ml, n=19) or amyotrophic lateral sclerosis (ALS) (95.4 pg/ml, n=46) had higher serum NfL values than a control group of neurological patients without evidence of structural CNS damage (control patients, CP) (4.4 pg/ml, n=68, p<0.0001 for each comparison, p=0.002 for AD patients) and healthy controls (HC) (3.3 pg/ml, n=67, p<0.0001). Similar differences were seen in corresponding CSF samples. CSF and serum levels correlated in AD (r=0.48, p=0.033), GBS (r=0.79, p<0.0001) and ALS (r=0.70, p<0.0001), but not in CP (r=0.11, p=0.3739). The sensitivity and specificity of serum NfL for separating ALS from healthy controls was 91.3% and 91.0%.

Conclusions

We developed and validated a novel ECL based sandwich immunoassay for the NfL protein in serum (NfL^Umea47:3); levels in ALS were more than 20-fold higher than in controls. Our data supports further longitudinal studies of serum NfL in neurodegenerative diseases as a potential biomarker of on-going disease progression, and as a potential surrogate to quantify effects of neuroprotective drugs in clinical trials.

Recent developments and future directions in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) encompasses a spectrum of acquired neuropathic conditions characterized by inflammatory demyelinating or axonal peripheral neuropathy with acute onset. Clinical and experimental studies in the past years have led to substantial progress in epidemiology, pathogenesis of GBS variants, and identification of prognostic factors relevant to treatment. In this review we provide an overview and critical assessment of the most recent developments and future directions in GBS research.

Cerebrospinal fluid tau levels predict prognosis in non-inherited frontotemporal dementia

BACKGROUND

The course of frontotemporal dementia (FTD) is heterogeneous and no predictors of survival are currently available. Cerebrospinal fluid (CSF) tau dosage has been demonstrated to be useful in predicting outcome over time in a number of neurological disorders.

OBJECTIVE

To assess CSF tau levels in FTD and to evaluate their prognostic value.

METHODS

Seventy-seven FTD patients with no mutations in known causative genes were consecutively enrolled, and CSF tau and phospho-tau levels analysed. Each patient was reassessed over time, and survival (i.e. death/bedridden and otherwise) was evaluated. The survival analysis was carried out by Cox proportional hazards regression models.

RESULTS

Patients with high CSF tau levels (≥400 pg/ml) had shorter survival than those with low CSF tau levels [hazard ratio (HR) = 3.406; 95% CI: 1.151-10.077; Wald χ(2) = 4.902; d.f. = 1; p = 0.027]. The association between tau levels and survival probability was confirmed after adjusting for age, gender, clinical phenotype and FTD clinical dementia rating at enrolment (HR = 3.769; 95% CI: 1.143-12.433; Wald χ(2) = 4.748; d.f. = 1; p = 0.029). Neither demographic or clinical characteristics nor CSF phospho-tau levels or apolipoprotein E genotype were significantly associated with prognosis.

CONCLUSIONS

This study argues that CSF tau levels may be considered in FTD to predict patients' outcome. Establishing in vivo prognostic biomarkers is mandatory to define homogeneous groups for inclusion in future clinical trials and to monitor the effectiveness of future therapeutic approaches.

S100B is increased in Parkinson's disease and ablation protects against MPTP-induced toxicity through the RAGE and TNF-α pathway

Parkinson’s disease is a neurodegenerative disorder that can, at least partly, be mimicked by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. S100B is a calcium-binding protein expressed in, and secreted by, astrocytes. There is increasing evidence that S100B acts as a cytokine or damage-associated molecular pattern protein not only in inflammatory but also in neurodegenerative diseases. In this study, we show that S100B protein levels were higher in post-mortem substantia nigra of patients with Parkinson’s disease compared with control tissue, and cerebrospinal fluid S100B levels were higher in a large cohort of patients with Parkinson’s disease compared with controls. Correspondingly, mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine showed upregulated S100B messenger RNA and protein levels. In turn, ablation of S100B resulted in neuroprotection, reduced microgliosis and reduced expression of both the receptor for advanced glycation endproducts and tumour necrosis factor-α. Our results demonstrate a role of S100B in the pathophysiology of Parkinson’s disease. Targeting S100B may emerge as a potential treatment strategy in this disorder.

Elevated levels of S100B, tau and pNFH in cerebrospinal fluid are correlated with subtypes of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an immune-mediated inflammatory disease in the peripheral nervous system. Specific biomarkers for the two most common clinical subtypes of GBS, i.e., acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor axonal neuropathy (AMAN) are still missing. The distinctive pathological features of AIDP and AMAN may lead to release of such specific biomarkers including glial markers (calcium-binding astroglial protein, S100B) and axonal damage markers [axoskeletal protein, phosphorylated neurofilament heavy protein (pNFH); cytoskeletal protein, tau], etc. To explore the potentials of biochemical markers for differential diagnosis and evaluation of prognosis of clinical subtypes in GBS, we used ELISA to measure the levels of S100B, tau and pNFH in serum and cerebrospinal fluid (CSF) from the patients with AIDP, AMAN, viral encephalitis and other non-inflammatory neurological disorders (OND), respectively. The values of albumin quotient and IgG index in CSF are significantly higher in AIDP and AMAN than in OND. The levels of S100B, tau and pNFH in serum and CSF are elevated in the patients with AIDP and AMAN compared to OND. The concentrations of these proteins are all higher in CSF than in serum. Increased levels of S100B in CSF at the acute phase are positively correlated with the GBS disability scale scores (GDSs) in AIDP, whereas enhanced levels of tau and pNFH in CSF are positively correlated with the GDSs in AMAN. Increased CSF levels of S100B, tau and pNFH at the acute phase may predict a poor prognosis and evaluate the severity of AIDP or AMAN at plateau and the recovery phase. Elevated levels of pNFH in CSF may be used for differentiating between AMAN and AIDP.

A case of anti-GA1 antibody-positive Fisher syndrome with elevated tau protein in cerebrospinal fluid

We describe a boy with Fisher syndrome. He presented the typical symptoms of Fisher syndrome, including external ophthalmoplegia, abnormality of convergence, and areflexia, after an episode of Campylobacter enterocolitis. Atypically, however, anti-GA1 antibody was detected in his serum, though anti-GQ1b and anti-GT1a antibodies were not. In addition, the tau protein level in his cerebrospinal fluid was elevated. Generally, Fisher syndrome is a self-limiting disease and has a good prognosis. In our patient, however, mild diplopia and areflexia persisted 6 months after their onset. Here, we report on the first Fisher syndrome patient with anti-GA1 antibody in the serum and elevated tau protein in the cerebrospinal fluid.

Evidence for acute neurotoxicity after chemotherapy

OBJECTIVE

Chronic neurotoxicity is a recognized long-term complication following chemotherapy in a range of diseases. Neurotoxicity adversely affects patients' quality of life. The objective of this study is to examine whether there is evidence of acute neurotoxicity.

METHODS

This prospective study included patients with secondary progressive multiple sclerosis (SPMS-BMT, n = 14) and hematological malignancies (HM-BMT, n = 17) receiving chemotherapy as preconditioning for bone marrow transplant. The control groups included SPMS patients matched for demographic and clinical data (SPMS-PL, n = 14) and healthy controls (n = 14). Neurodegeneration was assessed at baseline and longitudinally (months 1, 2, 3, 6, 9, 12, 24, and 36), combining a clinical scale for disability (Expanded Disability Status Scale [EDSS]), a serum protein biomarker for neurodegeneration (neurofilaments, NfH-SMI35), and brain atrophy measures (magnetic resonance imaging).

RESULTS

Disability progression was significantly more acute and severe following chemotherapy compared to placebo. Immediately after starting chemotherapy, serum NfH-SMI35 levels increased in 79% (p < 0.0001) of SPMS-BMT patients and 41% (p < 0.01) of HM-BMT patients compared to 0% of SPMS-PL patients or healthy controls. In SPMS-BMT serum NfH-SMI35 levels were > 100-fold higher 1 month after chemotherapy (29.73ng/ml) compared to baseline (0.28ng/ml, p < 0.0001). High serum NfH-SMI35 levels persisting for at least 3 months were associated with sustained disability progression on the EDSS (p < 0.05). Brain atrophy rates increased acutely in SPMS-BMT (-2.09) compared to SPMS-PL (-1.18, p < 0.05).

INTERPRETATION

Neurotoxicity is an unwanted acute side effect of aggressive chemotherapy.

Rostrocaudal dynamics of CSF biomarkers

The rostrocaudal gradient (RCG) of markers present in cerebrospinal fluid (CSF) has not been studied adequately due to lack of appropriate control populations and ethical restrictions. The aim of this study is to understand the rostrocaudal gradient of CSF biomarkers. We contacted a study comparing CSF levels of seven biomarkers from cisternal (rostral) and lumbar (caudal) CSF obtained from patients with trigeminal neuralgia and tension-type headache. The RCGs of CSF/serum albumin ratio, 8-isoprostane. GFAP, total tau and beta amyloid protein were higher than one. The RCGs of lactate, VEGF and the heavy chain of neurofilament protein were lower than one. The study provides new values for several commonly examined markers of cisternal CSF. Knowledge of the RCG gradient of different CSF markers is important in interpreting studies reporting ventricular CSF values.

Identification and preliminary characterization of ubiquitin C terminal hydrolase 1 (UCHL1) as a biomarker of neuronal loss in aneurysmal subarachnoid hemorrhage

By using two different approaches, ubiquitin C-terminal hydrolase 1 (UCHL1) was identified as a potential cerebrospinal fluid (CSF) biomarker of neuronal loss in aneurysmal subarachnoid hemorrhage (ASAH) and presumably other CNS damage and disease states. Appropriate antibodies and a sensitive ELISA were generated, and the release of UCHL1 into CSF was compared with that of pNF-H and S100beta in a cohort of 30 ASAH patients. Both UCHL1 and pNF-H showed persistent release into CSF in almost all patients in the second week postaneurysmal rupture (AR), and S100beta levels rapidly declined to baseline levels in 23 of 30 patients. Seven of thirty patients showed persistently elevated S100beta levels over the first 5 days post-AR and also had relatively higher levels of pNF-H and UCHL1 higher compared with the rest. These patients proved to have very poor outcomes, with 6 of 7 expiring. Patients who did reduce S100beta levels tended to have a better outcome if pNF-H and UCHL1 levels were also lower, and elevated UCHL1 levels in the second week post-AR were particularly predictive of poor outcome. Acute coordinated releases of large amounts of UCHL1, pNF-H, and S100beta in 16 of 30 patients were observed, suggesting sudden loss of brain tissues associated with secondary events. We conclude that measurement of the CSF levels of these proteins reveals details of ASAH progression and recovery and predicts patient outcome.

A highly sensitive electrochemiluminescence immunoassay for the neurofilament heavy chain protein

BACKGROUND

The loss of neurological function is closely related to axonal damage. Neurofilament subunits are concentrated in neurons and axons and have emerged as promising biomarkers for neurodegeneration. Electrochemiluminescence (ECL) based assays are known to be of superior sensitivity and require less sample volume than conventional ELISAs.

METHODS

We developed an ECL based solid-phase sandwich immunoassay to measure the neurofilament heavy chain protein (NfH(SMI35)) in CSF. We employed commercially available antibodies as previously used in a conventional ELISA (Petzold et al., 2003; Petzold and Shaw, 2007). The optimised and validated assay was applied in a reference cohort and defined patient groups.

RESULTS

Analytical sensitivity (background plus three SD) of our assay was 2.4 pg/ml. The mean intra-assay coefficient of variation (CV) was 4.8% and the inter-assay CV 8.4%. All measured control and patient samples produced signals well above background. Patients with multiple sclerosis (MS) (median 46.2 pg/ml, n=95), amyotrophic lateral sclerosis (ALS) (160.1 pg/ml, n=50), mild cognitive impairment/Alzheimer's disease (MCI/AD) (65.6 pg/ml, n=20), Guillain-Barre syndrome (GBS) (91.0 pg/ml, n=20) or subarachnoid hemorrhage (SAH) (345.0 pg/ml, n=20) had higher CSF NfH(SMI35) values than the reference cohort (27.1 pg/ml, n=73, p<0.0001 for each comparison).

CONCLUSION

The new ECL based assay for NfH(SMI35) in CSF is superior in terms of sensitivity, precision and accuracy to previously published methods (Petzold et al., 2003; Shaw et al., 2005; Teunissen et al., 2009). The improved performance and small sample volume requirement qualify this method in experimental settings and clinical trials designed to perform a number of tests on limited amounts of material.