Serum neurofilament light as biomarker of seizure-related neuronal injury in status epilepticus

Exploring biomarkers of neurodegeneration in epilepsy: Critical insights

The advent of biofluid biomarkers for neurodegenerative disorders has precipitated a surge in recent evidence regarding their role in epilepsy. In this literature review, we examine the diagnostic, prognostic, and therapeutic potential of several biomarkers, including amyloid-beta (Aβ) protein, total (t-tau), phosphorylated tau (p-tau) protein, alpha-synuclein, neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), and others in epilepsy. Recent studies highlight mid-life Aβ levels as a risk factor for late-onset epilepsy. Several studies also show that amyloid pathology correlates with cognitive impairment in people with epilepsy (PWE). T-tau and p-tau levels in CSF and serum show diagnostic potential, particularly for temporal lobe epilepsy (TLE). Tau may also have significant prognostic utility in cognition of PWE and status epilepticus. Despite promising findings, larger prospective studies are needed to validate these biomarkers for routine clinical use in older PWE. Mouse models demonstrate tau's association with increased seizure susceptibility and mortality and the association of tau reduction with reduced seizure severity. This further highlights the need to investigate tau-targeting therapies in future studies in older PWE. Recent small-scale retrospective studies link NfL's role in cognitive impairment and status epilepticus, suggest a prognostic role of alpha-synuclein in certain epilepsies, and propose emerging diagnostic and prognostic roles of other biomarkers in epilepsy, including GFAP, cytoskeletal proteins, and S100B. However, larger longitudinal studies are needed to confirm these findings. We propose integrating some of these biomarkers into clinical practice for selected older adults with epilepsy. This integration could improve diagnostic accuracy, prognosticate outcomes, and identify therapeutic targets that may improve seizure control and mitigate the progression of cognitive decline in PWE.

The utility of serum neurofilament light chain in MOGAD: Current insights and future directions

BACKGROUND

Serum neurofilament light chain (sNfL) has become an increasingly established biomarker for monitoring in multiple sclerosis (MS). Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a demyelinating disorder distinct from MS in terms of pathophysiology and treatment options, also presenting with demyelinating attacks that can result in permanent disability. Given its unpredictable disease course, the need for biomarkers reflective of the risk for poor clinical recovery or relapsing course is pressing. The purpose of this review is to summarize the current knowledge on sNfL levels in people with MOGAD, assess their utility for clinical practice and gain insights for future research.

METHODS

Embase, MEDLINE, Scopus, and CINAHL databases were searched following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations. Keywords used in the search included: (myelin oligodendrocyte glycoprotein OR MOG OR MOGAD) AND (neurofilament* OR neuro filament* OR NfL OR sNfL). This initial search generated 195 reports, 23 of which were original research articles investigating NfL levels in MOGAD patients, therefore meeting our inclusion criteria.

RESULTS

422 MOGAD patients were involved across all studies. Most studies revealed higher sNfL in MOGAD patients (n = 292) than in healthy controls (n = 3,172) with one study finding higher sNfL in MOGAD only during relapse. sNfL levels during attacks were similar when comparing MOGAD (n = 94) to MS (n = 256) and MOGAD (n = 149) to APQ4+ neuromyelitis optica spectrum disorder (APQ4+ NMOSD) (n = 214). MOGAD patients with brain lesions on magnetic resonance imaging (MRI) during a recent attack (n = 69 samples) had higher sNfL levels than patients without brain lesions (n = 78 samples). Median sNfL concentration was higher following clinical attacks (n = 69 samples) than in remission (n = 83 samples) in 3/5 studies. sNfL were higher at disease onset than subsequent attacks in 2 studies (n = 133 samples). Onset sNfL levels were not predictive of the likelihood of future relapse (relapsing: n = 15, monophasic: n = 18). A positive correlation was found between sNfL levels and attack severity assessed through various disability scales (n = 202), but not with the severity of acute or residual visual acuity (n = 45 eyes), or with residual retinal thickness among subjects with the optic neuritis (ON) phenotype (n = 11 eyes). The sGFAP/sNfL ratio showed utility in discriminating MOGAD from other autoimmune demyelinating diseases in two studies (MOGAD: n = 56, APQ4+ NMOSD: n = 66, MS: n = 31).

DISCUSSION

sNfL levels at presentation have limited utility in distinguishing MOGAD from other demyelinating disorders, but their combination with other biomarkers might improve their diagnostic utility. sNfL levels are higher in brain/spinal cord presentations than optic neuritis, correlating with clinical severity of these phenotypes but less so with the severity of visual outcome. Further studies should clarify the utility of sNfL as a biomarker for MOGAD, particularly in relation to long-term outcomes and imaging markers of central nervous system damage. Standardized sNfL testing parameters will improve study comparability and clinical application.

Neurofilament light chain and glial fibrillary acidic protein as diagnostic and prognostic biomarkers in epileptic seizures and epilepsy: A systematic review

Epileptology - with epilepsy as one of the most common neurological diseases - has an urgent need for easily accessible biomarkers to improve diagnosis, prognosis and therapeutic monitoring. Neurofilament light chain (NfL) and Glial Fibrillary Acidic Protein (GFAP) have emerged as promising fluid biomarkers in various neurological disorders. Their potential role in epileptic seizures and epilepsy remains largely unexplored. To assess the current state of research on this topic we comprehensively searched the published literature for studies on GFAP and/or NfL in cerebrospinal fluid and/or blood in adult humans with epileptic seizures, status epilepticus or epilepsy (last data base search on 10th of May 2024). We identified a total of 2285 publications of which 19 fulfilled our search criteria. The studies targeted various outcomes such as prognosis in status epilepticus, differentiation of seizure semiology and etiology, differentiation of epileptic seizures from non-epileptic conditions, prediction of epilepsy in autoimmune epilepsy, after a stroke or after a first unprovoked seizure, the role of the time interval from seizure to sampling, the association with disease duration as well as seizure frequency and the influence of seizure suppressing medication. The results are heterogeneous but indicate promising applications for both NfL and GFAP in diagnosis and prognostication of patients with epileptic seizures and epilepsy. In the present review we summarize the current evidence, future perspectives, but also limitations, of NfL and GFAP as fluid biomarkers in epilepsy and epileptic seizures.

Transient Global Amnesia (TGA): Is It Really Benign? A Pilot Study on Blood Biomarkers

We aimed to determine whether transient global amnesia (TGA) is associated with alterations in central nervous system (CNS) injury biomarkers-serum neurofilament light chain (sNfL) and serum glial fibrillary acidic protein (sGFAP). In a prospective cohort of TGA patients, blood samples were obtained within 24-48 h of TGA onset (t0) and 6 weeks thereafter (t1). We assessed sNfL and sGFAP levels using the highly sensitive single-molecule array assay and calculated Z-scores adjusted for age, gender, and body mass index (BMI). Demographics, electroencephalography (EEG), and cerebral magnetic resonance imaging (cMRI) findings were also collected. A total of 20 patients were included (median age: 66 years, 70% women). No significant changes in sNfL or sGFAP levels associated with TGA at t0 and t1 were observed. Median sNfL Z-scores were 0.45 (interquartile range [IQR] -0.09, 1.19) at t0 and 0.60 (IQR -0.61, 1.19) at t1. Median sGFAP Z-scores were 0.27 (IQR -0.45, 0.76) at t0 and 0.44 (IQR -0.27, 0.75) at t1. Similarly, in the subgroup of patients with diffusion-weighted imaging (DWI)-positive hippocampal lesions (n = 5/20[25%]), no elevations in blood biomarkers were detected. Our pilot study on neurological blood biomarkers supports the benign nature of TGA, indicating that no CNS tissue damage occurs.

Higher plasma neurofilament-light chain concentration in drug-resistant epilepsy

Drug-resistant epilepsy is the most severe form of epilepsy and is frequently associated with cognitive decline. Whether drug-resistant epilepsy results in neurodegeneration or other types of brain injury is not known, and early detection of detrimental clinical trajectories would be clinically very useful. Blood biomarkers of brain injury reflect neurodegeneration or brain injury in several brain diseases but have not been extensively studied in epilepsy. We investigated a panel of such markers in a large epilepsy cohort with an emphasis on assessing differences between drug-resistant and monotherapy-controlled epilepsy. Blood neurofilament light, glial fibrillary acidic protein, total tau, S100 calcium-binding protein B and neuron-specific enolase concentrations were measured in 444 patients (aged ≥ 18 years) with epilepsy participating in a prospective regional Biobank study in Västra Götaland (Sweden). Multiple linear regression assessed associations between clinical variables and marker levels. Levels were then compared between patients with drug-resistant epilepsy (n = 101) and patients with monotherapy-controlled epilepsy (n = 164). We also performed logistic regression analysis to evaluate the significance of the markers as predictors of epilepsy status (drug-resistant epilepsy or monotherapy-controlled epilepsy) while controlling for clinical variables: age, sex, epilepsy duration, epilepsy type and lesions. All markers correlated with age. In younger patients (≤50 years), cases of drug-resistant epilepsy had higher levels of neurofilament light (P = 0.002) and glial fibrillary acidic protein (P = 0.006) compared with monotherapy-controlled epilepsy. After excluding patients with known structural lesions, neurofilament light levels remained significantly elevated in drug-resistant epilepsy versus monotherapy-controlled epilepsy (P = 0.029). Neurofilament light also emerged as a significant predictor of drug-resistant status in a logistic regression model following adjustments for clinical variables. Future studies should explore if neurofilament light can be used for surveillance of disease course and whether it reflects brain injury in drug-resistant epilepsy.

Higher plasma total tau concentrations among patients reporting CNS-related side effects from antiseizure medication

BACKGROUND

Side effects from antiseizure medication (ASM) are common in epilepsy but biomarkers for detection and monitoring are missing. This study investigated associations between CNS-related side effects from ASM and blood concentrations of the brain injury markers neurofilament-light (NFL), total tau, glial acidic fibrillary protein (GFAP), S100 calcium-binding protein B (S100B) and neuron-specific enolase (NSE).

METHODS

This is a population-based cohort study of adults with epilepsy recruited from five Swedish outpatient neurology clinics from December 2020 to April 2023. Side effects classified as CNS-related: tiredness, dizziness, headache, concentration, memory, mood, motor/tremor, or sleep. Marker concentrations in the groups CNS side effects/no side effects were analyzed with Mann-Whitney U-test and significant differences were included in multivariable logistic regression models adjusting for age, epilepsy duration, seizure status, acquired structural lesion, and mono-/polytherapy.

RESULTS

The cohort consisted of 367 patients, 187 (51 %) were females, the median age was 43 years (IQR 30-61), and 123 (34 %) reported CNS side effects. Total tau was higher among participants reporting CNS side effects (median 4.44 (95 %CI 4.12-4.88) pg/ml) compared with participants without side effects (3.84 (95 %CI 3.52-4.07) pg/ml, p < 0.01). The difference remained significant in multivariable regression models. NSE was higher among participants without side effects but did not remain significant in the multivariable regression model. No differences were observed for NFL, GFAP or S100B.

CONCLUSIONS

Higher total tau plasma concentration could be associated with increased risk of CNS side effects from ASM. Longitudinal studies could determine if this reflects vulnerability or detrimental effects of ASM.

TRIAL REGISTRATION

PREDICT, clinicaltrials.gov identifier NCT04559919.

Cerebrospinal Creatine Kinase BB Isoenzyme: A Biomarker for Predicting Outcome After Cardiac Arrest

BACKGROUND

Cerebrospinal fluid creatine kinase BB isoenzyme (CSF CK-BB) after cardiac arrest (CA) has been shown to have a high positive predictive value for poor neurological outcome, but it has not been evaluated in the setting of targeted temperature management (TTM) and modern CA care. We aimed to evaluate CSF CK-BB as a prognostic biomarker after CA.

METHODS

We performed a retrospective cohort study of patients with CA admitted between 2010 and 2020 to a three-hospital health system who remained comatose and had CSF CK-BB assayed between 36 and 84 h after CA. We examined the proportion of patients at hospital discharge who achieved favorable or intermediate neurological outcome, defined as Cerebral Performance Category score of 1-3, compared with those with poor outcome (Cerebral Performance Category score 4-5) for various CSF CK-BB thresholds. We also evaluated additive value of bilateral absence of somatosensory evoked potentials (SSEPs).

RESULTS

Among 214 eligible patients, the mean age was 54.7 ± 4.8 years, 72% of patients were male, 33% were nonwhite, 17% had shockable rhythm, 90% were out-of-hospital CA, and 83% received TTM. A total of 19 (9%) awakened. CSF CK-BB ≥ 230 U/L predicted a poor outcome at hospital discharge, with a specificity of 100% (95% confidence interval [CI] 82-100%) and sensitivity of 69% (95% CI 62-76%). When combined with bilaterally absent N20 response on SSEP, specificity remained 100% while sensitivity increased to 80% (95% CI 73-85%). Discordant CK-BB and SSEP findings were seen in 13 (9%) patients.

CONCLUSIONS

Cerebrospinal fluid creatine kinase BB isoenzyme levels accurately predicted poor neurological outcome among CA survivors treated with TTM. The CSF CK-BB cutoff of 230 U/L optimizes sensitivity to 69% while maintaining a specificity of 100%. CSF CK-BB could be a useful addition to multimodal neurological prognostication after CA.

Plasma proteomics in epilepsy: Network-based identification of proteins associated with seizures

PURPOSE

Identification of potential biomarkers of seizures.

METHODS

In this exploratory study, we quantified plasma protein intensities in 15 patients with recent seizures compared to 15 patients with long-standing seizure freedom. Using TMT-based proteomics we found fifty-one differentially expressed proteins.

RESULTS

Network analyses including co-expression networks and protein-protein interaction networks, using the STRING database, followed by network centrality and modularity analyses revealed 22 protein modules, with one module showing a significant association with seizures. The protein-protein interaction network centered around this module identified a subnetwork of 125 proteins, grouped into four clusters. Notably, one cluster (mainly enriching inflammatory pathways and Gene Ontology terms) demonstrated the highest enrichment of known epilepsy-related genes.

CONCLUSION

Overall, our network-based approach identified a protein module linked with seizures. The module contained known markers of epilepsy and inflammation. The results also demonstrate the potential of network analysis in discovering new biomarkers for improved epilepsy management.

Bursts of brain erosion: seizures and age-dependent neurological vulnerability

Hypersynchronous and exaggerated neuronal firing, exemplified by epileptiform activity and seizures, are disruptors of brain function across acute and chronic neuropathological conditions. Here, we focus on how seizure activity, whether as a primary symptom or a secondary comorbid event within a complex pathological setting, adversely impacts neurological trajectories. We discuss experimental and clinical evidence illustrating the participation of neurodegenerative and senescence-like adaptations. Paroxysmal neuronal events, through bidirectional causality, are linked with immune and microvascular changes, disrupting cellular homeostasis and creating a feed-forward loop that intertwines with age-related frailty to deteriorate mental health. We emphasize the clinical significance of early detection of these brain vulnerabilities through biomarkers, monitoring neurodevelopmental risks in children, and tracking neurodegenerative disease progression in aging populations.

Emerging Trends: Neurofilament Biomarkers in Precision Neurology

Neurofilaments are structural proteins found in the cytoplasm of neurons, particularly in axons, providing structural support and stability to the axon. They consist of multiple subunits, including NF-H, NF-M, and NF-L, which form long filaments along the axon's length. Neurofilaments are crucial for maintaining the shape and integrity of neurons, promoting axonal transport, and regulating neuronal function. They are part of the intermediate filament (IF) family, which has approximately 70 tissue-specific genes. This diversity allows for a customizable cytoplasmic meshwork, adapting to the unique structural demands of different tissues and cell types. Neurofilament proteins show increased levels in both cerebrospinal fluid (CSF) and blood after neuroaxonal damage, indicating injury regardless of the underlying etiology. Precise measurement and long-term monitoring of damage are necessary for determining prognosis, assessing disease activity, tracking therapeutic responses, and creating treatments. These investigations contribute to our understanding of the importance of proper NF composition in fundamental neuronal processes and have implications for neurological disorders associated with NF abnormalities along with its alteration in different animal and human models. Here in this review, we have highlighted various neurological disorders such as Alzheimer's, Parkinson's, Huntington's, Dementia, and paved the way to use neurofilament as a marker in managing neurological disorders.

Neurofilament light (NfL) concentrations in patients with epilepsy with recurrent isolated seizures: Insights from a clinical cohort study

PURPOSE

To detect possible neuronal damage due to recurrent isolated seizures in patients with epilepsy in a clinical routine setting.

METHODS

We measured the serum concentrations of neurofilament light chain (sNfL) in 46 outpatients with an at least monthly occurrence (self-reported) of generalized tonic-clonic seizures in the six months prior to the study and in 49 patients who had been seizure free (self-reported) for at least one year. We assigned the patients with seizure activity into groups with moderate and high seizure frequency. We measured sNfL with a highly sensitive single molecule array (Simoa).

RESULTS

The majority (94 %) of all patients with epilepsy had sNfL values within the age adjusted reference ranges of our laboratory. Three patients with and three patients without seizure activity (each 3 %) showed elevated sNfL concentrations. Age adjusted sNfL concentrations did not differ significantly between patients with and without seizure activity in the total sample or in the female subgroup. In contrast, NfL concentrations were significantly higher in male patients with seizure activity and highest in the subgroup of those with high seizure activity, but were only above the reference range in two patients. sNfL concentrations did not differ between focal and generalized epilepsies and between genetic and structural etiologies.

CONCLUSIONS

The sNfL concentrations in patients with epilepsy and healthy patients did not differ significantly. The finding of higher sNfL concentrations in males with self-reported seizure activity should be viewed with utmost caution because the difference was small and only two male patients showed sNfL concentrations above the reference range.

Elevated plasma neurofilament light and glial fibrillary acidic protein in epilepsy versus nonepileptic seizures and nonepileptic disorders

OBJECTIVE

Research suggests that recurrent seizures may lead to neuronal injury. Neurofilament light chain protein (NfL) and glial fibrillary acidic protein (GFAP) levels increase in cerebrospinal fluid and blood in response to neuroaxonal damage, and they have been hypothesized as potential biomarkers for epilepsy. We examined plasma NfL and GFAP levels and their diagnostic utility in differentiating patients with epilepsy from those with psychogenic nonepileptic seizures (PNES) and other nonepileptic disorders.

METHODS

We recruited consecutive adults admitted for video-electroencephalographic monitoring and formal neuropsychiatric assessment. NfL and GFAP levels were quantified and compared between different patient groups and an age-matched reference cohort (n = 1926) and correlated with clinical variables in patients with epilepsy.

RESULTS

A total of 138 patients were included, of whom 104 were diagnosed with epilepsy, 22 with PNES, and 12 with other conditions. Plasma NfL and GFAP levels were elevated in patients with epilepsy compared to PNES, adjusted for age and sex (NfL p = .04, GFAP p = .04). A high proportion of patients with epilepsy (20%) had NfL levels above the 95th age-matched percentile compared to the reference cohort (5%). NfL levels above the 95th percentile of the reference cohort had a 95% positive predictive value for epilepsy. Patients with epilepsy who had NfL levels above the 95th percentile were younger than those with lower levels (37.5 vs. 43.8 years, p = .03).

SIGNIFICANCE

An elevated NfL or GFAP level in an individual patient may support an underlying epilepsy diagnosis, particularly in younger adults, and cautions against a diagnosis of PNES alone. Further examination of the association between NfL and GFAP levels and specific epilepsy subtypes or seizure characteristics may provide valuable insights into disease heterogeneity and contribute to the refinement of diagnosis, understanding pathophysiological mechanisms, and formulating treatment approaches.

Cerebral clues: serum neurofilament light chain (sNfL) as a novel biomarker for immune check point inhibitor (ICI) mediated seronegative encephalitis

Immune checkpoint inhibitor (ICI) mediated encephalitides are increasingly being recognized in the literature, but atypical cases may be missed or misdiagnosed. Recent efforts are directed to identify biomarkers to help elucidate early diagnosis and treatment. Herein, we describe two cases of antibody negative ICI-mediated encephalitis with elevated serum Neurofilament light chain (sNfL) levels. Practical Implication: Baseline and longitudinal measurements of serum neurofilament light chains can help determine treatment strategies and prognosis in patients with suspected immune checkpoint inhibitor encephalitis.

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.

Neurosteroids as Novel Anticonvulsants for Refractory Status Epilepticus and Medical Countermeasures for Nerve Agents: A 15-Year Journey to Bring Ganaxolone from Bench to Clinic

This article describes recent advances in the use of neurosteroids as novel anticonvulsants for refractory status epilepticus (RSE) and as medical countermeasures (MCs) for organophosphates and chemical nerve agents (OPNAs). We highlight a comprehensive 15-year journey to bring the synthetic neurosteroid ganaxolone (GX) from bench to clinic. RSE, including when caused by nerve agents, is associated with devastating morbidity and permanent long-term neurologic dysfunction. Although recent approval of benzodiazepines such as intranasal midazolam and intranasal midazolam offers improved control of acute seizures, novel anticonvulsants are needed to suppress RSE and improve neurologic function outcomes. Currently, few anticonvulsant MCs exist for victims of OPNA exposure and RSE. Standard-of-care MCs for postexposure treatment include benzodiazepines, which do not effectively prevent or mitigate seizures resulting from nerve agent intoxication, leaving an urgent unmet medical need for new anticonvulsants for RSE. Recently, we pioneered neurosteroids as next-generation anticonvulsants that are superior to benzodiazepines for treatment of OPNA intoxication and RSE. Because GX and related neurosteroids that activate extrasynaptic GABA-A receptors rapidly control seizures and offer robust neuroprotection by reducing neuronal damage and neuroinflammation, they effectively improve neurologic outcomes after acute OPNA exposure and RSE. GX has been selected for advanced, Biomedical Advanced Research and Development Authority-supported phase 3 trials of RSE and nerve agent seizures. In addition, in mechanistic studies of neurosteroids at extrasynaptic receptors, we identified novel synthetic analogs with features that are superior to GX for current medical needs. Development of new MCs for RSE is complex, tedious, and uncertain due to scientific and regulatory challenges. Thus, further research will be critical to fill key gaps in evaluating RSE and anticonvulsants in vulnerable (pediatric and geriatric) populations and military persons. SIGNIFICANCE STATEMENT: Following organophosphate and nerve agent intoxication, refractory status epilepticus (RSE) occurs despite benzodiazepine treatment. RSE occurs in 40% of status epilepticus patients, with a 35% mortality rate and significant neurological morbidity in survivors. To treat RSE, neurosteroids are better anticonvulsants than benzodiazepines. Our pioneering use of neurosteroids for RSE and nerve agents led us to develop ganaxolone as a novel anticonvulsant and neuroprotectant with significantly improved neurological outcomes. This article describes the bench-to-bedside journey of bringing neurosteroid therapy to patients, with ganaxolone leading the way.

Neurofilament light, glial fibrillary acidic protein, and tau in a regional epilepsy cohort: High plasma levels are rare but related to seizures

OBJECTIVE

Higher levels of biochemical blood markers of brain injury have been described immediately after tonic-clonic seizures and in drug-resistant epilepsy, but the levels of such markers in epilepsy in general have not been well characterized. We analyzed neurofilament light (NfL), glial fibrillary acidic protein (GFAP), and tau in a regional hospital-based epilepsy cohort and investigated what proportion of patients have levels suggesting brain injury, and whether certain epilepsy features are associated with high levels.

METHODS

Biomarker levels were measured in 204 patients with an epilepsy diagnosis participating in a prospective regional biobank study, with age and sex distribution correlating closely to that of all patients seen for epilepsy in the health care region. Absolute biomarker levels were assessed between two patient groups: patients reporting seizures within the 2 months preceding inclusion and patients who did not have seizures for more than 1 year. We also assessed the proportion of patients with above-normal levels of NfL.

RESULTS

NfL and GFAP, but not tau, increased with age. Twenty-seven patients had abnormally high levels of NfL. Factors associated with such levels were recent seizures (p = .010) and epileptogenic lesion on radiology (p = .001). Levels of NfL (p = .006) and GFAP (p = .032) were significantly higher in young patients (<65 years) with seizures ≤2 months before inclusion compared to those who reported no seizures for >1 year. NfL and GFAP correlated weakly with the number of days since last seizure (NfL: rs  = -.228, p = .007; GFAP: rs  = -.167, p = .048) in young patients. NfL also correlated weakly with seizure frequency in the last 2 months (rs  = .162, p = .047).

SIGNIFICANCE

Most patients with epilepsy do not have biochemical evidence of brain injury. The association with seizures merits further study; future studies should aim for longitudinal sampling and examine whether individual variations in NfL or GFAP levels could reflect seizure activity.

Clinical, imaging, and biomarker evidence of amyloid- and tau-related neurodegeneration in late-onset epilepsy of unknown etiology

Accumulating evidence suggests amyloid and tau-related neurodegeneration may play a role in development of late-onset epilepsy of unknown etiology (LOEU). In this article, we review recent evidence that epilepsy may be an initial manifestation of an amyloidopathy or tauopathy that precedes development of Alzheimer's disease (AD). Patients with LOEU demonstrate an increased risk of cognitive decline, and patients with AD have increased prevalence of preceding epilepsy. Moreover, investigations of LOEU that use CSF biomarkers and imaging techniques have identified preclinical neurodegeneration with evidence of amyloid and tau deposition. Overall, findings to date suggest a relationship between acquired, non-lesional late-onset epilepsy and amyloid and tau-related neurodegeneration, which supports that preclinical or prodromal AD is a distinct etiology of late-onset epilepsy. We propose criteria for assessing elevated risk of developing dementia in patients with late-onset epilepsy utilizing clinical features, available imaging techniques, and biomarker measurements. Further research is needed to validate these criteria and assess optimal treatment strategies for patients with probable epileptic preclinical AD and epileptic prodromal AD.

Fluid Biomarkers of Neuro-Glial Injury in Human Status Epilepticus: A Systematic Review

As per the latest ILAE definition, status epilepticus (SE) may lead to long-term irreversible consequences, such as neuronal death, neuronal injury, and alterations in neuronal networks. Consequently, there is growing interest in identifying biomarkers that can demonstrate and quantify the extent of neuronal and glial injury. Despite numerous studies conducted on animal models of status epilepticus, which clearly indicate seizure-induced neuronal and glial injury, as well as signs of atrophy and gliosis, evidence in humans remains limited to case reports and small case series. The implications of identifying such biomarkers in clinical practice are significant, including improved prognostic stratification of patients and the early identification of those at high risk of developing irreversible complications. Moreover, the clinical validation of these biomarkers could be crucial in promoting neuroprotective strategies in addition to antiseizure medications. In this study, we present a systematic review of research on biomarkers of neuro-glial injury in patients with status epilepticus.

Neurofilament light chain: A possible fluid biomarker in the intrahippocampal kainic acid mouse model for chronic epilepsy?

OBJECTIVE

In the management of epilepsy, there is an ongoing quest to discover new biomarkers to improve the diagnostic process, the monitoring of disease progression, and the evaluation of treatment responsiveness. In this regard, biochemical traceability in biofluids is notably absent in contrast to other diseases. In the present preclinical study, we investigated the potential of neurofilament light chain (NfL) as a possible diagnostic and response fluid biomarker for epilepsy.

METHODS

We gained insights into NfL levels during the various phases of the intrahippocampal kainic acid mouse model of temporal lobe epilepsy-namely, the status epilepticus (SE) and the chronic phase with spontaneous seizures. To this end, NfL levels were determined directly in the cerebral interstitial fluid (ISF) with cerebral open flow microperfusion as sampling technique, as well as in cerebrospinal fluid (CSF) and plasma. Lastly, we assessed whether NfL levels diminished upon curtailing SE with diazepam and ketamine.

RESULTS

NfL levels are higher during SE in both cerebral ISF and plasma in kainic acid-treated mice compared to sham-injected mice. Additionally, ISF and plasma NfL levels are lower in mice treated with diazepam and ketamine to stop SE compared with the vehicle-treated mice. In the chronic phase with spontaneous seizures, higher NfL levels could only be detected in ISF and CSF samples, and not in plasma. No correlations could be found between NfL levels and seizure burden, nor with immunohistological markers for neurodegeneration/inflammation.

SIGNIFICANCE

Our findings demonstrate the translational potential of NfL as a blood-based fluid biomarker for SE. This is less evident for chronic epilepsy, as in this case higher NfL levels could only be detected in ISF and CSF, and not in plasma, acknowledging the invasive nature of CSF sampling in chronic epilepsy follow-up.

Neurofilament light (NfL) as biomarker in serum and CSF in status epilepticus

OBJECTIVE

We explored the potential of neurofilament light chain (NfL) in serum and cerebrospinal fluid as a biomarker for neurodestruction in status epilepticus.

METHODS

In a retrospective analysis, we measured NfL in serum and cerebrospinal fluid samples of patients with status epilepticus using a highly sensitive single-molecule array technique (Simoa). Status epilepticus was diagnosed according to ILAE criteria. Additionally, we employed an alternative classification with more emphasis on the course of status epilepticus. We used data from three large control groups to compare NfL in status epilepticus versus neurologically healthy controls.

RESULTS

We included 28 patients (mean age: 69.4 years, SD: 15 years) with a median status duration of 44 h (IQR: 80 h). Twenty-one patients (75%) suffered from convulsive status epilepticus and seven (25%) from non-convulsive status epilepticus. Six patients died (21%). Cerebrospinal fluid and serum NfL concentrations showed a high correlation (r = 0.73, p < 0.001, Pearson). The main determinant of NfL concentration was the status duration. NfL concentrations did not differ between convulsive status epilepticus and convulsive status epilepticus classified according to the ILAE or to the alternative classification without and with adjusting for status duration and time between status onset and sampling. We found no association of NfL concentration with death, treatment refractoriness, or prognostic scores.

CONCLUSION

The results suggest that neurodestruction in status epilepticus measured by NfL is mainly determined by status duration, not status type nor therapy refractoriness. Therefore, our results suggest that regarding neurodestruction convulsive and non-convulsive status epilepticus are both neurological emergencies of comparable urgency.

Molecular Biomarkers of Neuronal Injury in Epilepsy Shared with Neurodegenerative Diseases

In neurodegenerative diseases, changes in neuronal proteins in the cerebrospinal fluid and blood are viewed as potential biomarkers of the primary pathology in the central nervous system (CNS). Recent reports suggest, however, that level of neuronal proteins in fluids also alters in several types of epilepsy in various age groups, including children. With increasing evidence supporting clinical and sub-clinical seizures in Alzheimer's disease, Lewy body dementia, Parkinson's disease, and in other less common neurodegenerative conditions, these findings call into question the specificity of neuronal protein response to neurodegenerative process and urge analysis of the effects of concomitant epilepsy and other comorbidities. In this article, we revisit the evidence for alterations in neuronal proteins in the blood and cerebrospinal fluid associated with epilepsy with and without neurodegenerative diseases. We discuss shared and distinctive characteristics of changes in neuronal markers, review their neurobiological mechanisms, and consider the emerging opportunities and challenges for their future research and diagnostic use.

Neurofilament light chain in cerebrospinal fluid as a novel biomarker in evaluating both clinical severity and therapeutic response in Niemann-Pick disease type C1

PURPOSE

Niemann-Pick disease type C1 (NPC1) is a neurodegenerative lysosomal disorder caused by pathogenic variants in NPC1. Disease progression is monitored using the NPC Neurological Severity Scale, but there are currently no established validated or qualified biomarkers. Neurofilament light chain (NfL) is being investigated as a biomarker in multiple neurodegenerative diseases.

METHODS

Cross-sectional and longitudinal cerebrospinal fluid (CSF) samples were obtained from 116 individuals with NPC1. NfL levels were measured using a solid-phase sandwich enzyme-linked immunosorbent assay and compared with age-appropriate non-NPC1 comparison samples.

RESULTS

Median levels of NfL were elevated at baseline (1152 [680-1840] pg/mL) in NPC1 compared with controls (167 [82-372] pg/mL; P < .001). Elevated NfL levels were associated with more severe disease as assessed by both the 17-domain and 5-domain NPC Neurological Severity Score. Associations were also observed with ambulation, fine motor, speech, and swallowing scores. Although treatment with the investigational drug 2-hydroxypropyl-β-cyclodextrin (adrabetadex) did not decrease CSF NfL levels, miglustat therapy over time was associated with a decrease (odds ratio = 0.77, 95% CI = 0.62-0.96).

CONCLUSION

CSF NfL levels are increased in individuals with NPC1, associated with clinical disease severity, and decreased with miglustat therapy. These data suggest that NfL is a biomarker that may have utility in future therapeutic trials.

Neuro-glial degeneration in Status Epilepticus: Exploring the role of serum levels of Neurofilament light chains and S100B as prognostic biomarkers for short-term functional outcome

BACKGROUND

The last ILAE definition of Status Epilepticus (SE) highlights that the persistence of the epileptic activity per se could determine irreversible brain damages that could be responsible for long-term consequences. The measurement of neuro-glial injury biomarkers could help in the identification of those patients who will eventually develop short- and long-term consequences of SE. At present none of the already studied biomarkers has been validated to be used in everyday clinical practice. In this study, we explore the role of NfL and S100B as a prognostic biomarkers to identify patients who will develop short-term disability after an episode of SE.

METHODS

This is a retrospective assessment of the serum levels of both NfL and S100B in a cohort of 87 adult patients with SE prospectively collected in our SE registry (Modena Status Epilepticus Registry - MoSER -) at Baggiovara Civil Hospital (Modena, Italy). All samples were acquired during SE within 72 hours of SE diagnosis. The comparison groups were: healthy controls (HC, n = 27) and patients with epilepsy (PWE, n = 30). Demographic, clinical, and therapeutical information and thirty-days follow-up information regarding disability development were acquired for every included patient and analyzed in relation to NfL and S100B values.

RESULTS

Serum levels of NfL were significantly higher in SE compared to those of PWE (median 7.35 pg/ml, IQR 6.4, p < 0.001) and HC (median 6.57 pg/ml, IQR 9.1, p < 0.001); S100B serum levels were higher in SE (median 0.11 ug/L, IQR 0.18) compared to PWE (median 0.03 ug/L, IQR 0.03, p < 0.001) and HC (median 0.02 ug/L, IQR 0.008, p < 0.001). However, only NfL serum levels were found to be an independent predictor of 30 days functional outcome whereas S100B levels did not.

CONCLUSIONS

Our results suggest that NfL measurement in serum during SE could help predict the short-term functional outcome. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022.

Clinical scores and clusters for prediction of outcomes in status epilepticus

Status epilepticus (SE) is a life-threatening condition and may have long-term negative sequelae. Short- and long-term outcomes encompass mortality, deterioration of functional status compared to baseline, refractoriness to treatment, recurrence of SE, and development of epilepsy, cognitive impairment, and behavioral disturbances. So far, the greatest amount of evidence is available for the prediction of short-term mortality. Conversely, the knowledge regarding long-term consequences among SE survivors is still scarce and several issues have not yet been resolved. The heterogeneity of SE renders the prognostication of outcomes challenging. Although aetiology is the main determinant of the outcome, different prognostic predictors have been identified. In this regard, data on group effects need to be integrated into prognostic scores to allow individual risk stratification. Importantly, many of the present scores are not designed to enable repetition to follow patient evolution. A new paradigm for the assessment of SE outcomes should consider variables that become available and/or can be retested during the course of SE. Neuroimaging findings, serum biomarkers, treatment characteristics, complications during SE, peri-ictal and postictal characteristics after SE cessation look as promising determinants of outcome and are suitable for inclusion in future models to enhance the quality and increase the reliability of prediction. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022.

Plasma Neurofilament Light Chain (NF-L) Is a Prognostic Biomarker for Cortical Damage Evolution but Not for Cognitive Impairment or Epileptogenesis Following Experimental TBI

Plasma neurofilament light chain (NF-L) levels were assessed as a diagnostic biomarker for traumatic brain injury (TBI) and as a prognostic biomarker for somatomotor recovery, cognitive decline, and epileptogenesis. Rats with severe TBI induced by lateral fluid-percussion injury (n = 26, 13 with and 13 without epilepsy) or sham-operation (n = 8) were studied. During a 6-month follow-up, rats underwent magnetic resonance imaging (MRI) (day (D) 2, D7, and D21), composite neuroscore (D2, D6, and D14), Morris-water maze (D35−D39), and a 1-month-long video-electroencephalogram to detect unprovoked seizures during the 6th month. Plasma NF-L levels were assessed using a single-molecule assay at baseline (i.e., naïve animals) and on D2, D9, and D178 after TBI or a sham operation. Plasma NF-L levels were 483-fold higher on D2 (5072.0 ± 2007.0 pg/mL), 89-fold higher on D9 (930.3 ± 306.4 pg/mL), and 3-fold higher on D176 32.2 ± 8.9 pg/mL after TBI compared with baseline (10.5 ± 2.6 pg/mL; all p < 0.001). Plasma NF-L levels distinguished TBI rats from naïve animals at all time-points examined (area under the curve [AUC] 1.0, p < 0.001), and from sham-operated controls on D2 (AUC 1.0, p < 0.001). Plasma NF-L increases on D2 were associated with somatomotor impairment severity (ρ = −0.480, p < 0.05) and the cortical lesion extent in MRI (ρ = 0.401, p < 0.05). Plasma NF-L increases on D2 or D9 were associated with the cortical lesion extent in histologic sections at 6 months post-injury (ρ = 0.437 for D2; ρ = 0.393 for D9, p < 0.05). Plasma NF-L levels, however, did not predict somatomotor recovery, cognitive decline, or epileptogenesis (p > 0.05). Plasma NF-L levels represent a promising noninvasive translational diagnostic biomarker for acute TBI and a prognostic biomarker for post-injury somatomotor impairment and long-term structural brain damage.