Congenital myasthenic syndromes in adults: clinical features, diagnosis and long-term prognosis.

Congenital myasthenic syndromes (CMS) are clinically and genetically heterogeneous diseases caused by mutations affecting neuromuscular transmission. Even if the first symptoms mainly occur during childhood, adult neurologists must confront this challenging diagnosis and manage these patients throughout their adulthood. However, long-term follow-up data from large cohorts of CMS patients are lacking and the long-term prognosis of these patients is largely unknown. We report the clinical features, diagnostic difficulties, and long-term prognosis of a French nationwide cohort of 235 adult patients with genetically confirmed CMS followed in 23 specialized neuromuscular centres. Data were retrospectively analysed. Of the 235 patients, 123 were female (52.3%). The diagnosis was made in adulthood in 139 patients, 110 of whom presented their first symptoms before the age of 18. Mean follow-up time between first symptoms and last visit was 34 years (SD = 15.1). Pathogenic variants were found in 19 disease-related genes. CHRNE-low expressor variants were the most common (23.8%), followed by variants in DOK7 (18.7%) and RAPSN (14%). Genotypes were clustered into four groups according to the initial presentation: ocular group (CHRNE-LE, CHRND, FCCMS), distal group (SCCMS), limb-girdle group (RAPSN, COLQ, DOK7, GMPPB, GFPT1), and a variable-phenotype group (MUSK, AGRN). The phenotypical features of CMS did not change throughout life. Only four genotypes had a proportion of patients requiring intensive care unit (ICU) admission that exceeded 20%: RAPSN (54.8%), MUSK (50%), DOK7 (38.6%) and AGRN (25.0%). In RAPSN and MUSK patients most ICU admissions occurred before age 18 years and in DOK7 and AGRN patients at or after 18 years of age. Different patterns of disease course (stability, improvement and progressive worsening) may succeed one another in the same patient throughout life, particularly in AGRN, DOK7 and COLQ. At the last visit, 55% of SCCMS and 36.3% of DOK7 patients required ventilation; 36.3% of DOK7 patients, 25% of GMPPB patients and 20% of GFPT1 patients were wheelchair-bound; most of the patients who were both wheelchair-bound and ventilated were DOK7 patients. Six patients died in this cohort. The positive impact of therapy was striking, even in severely affected patients. In conclusion, even if motor and/or respiratory deterioration could occur in patients with initially moderate disease, particularly in DOK7, SCCMS and GFPT1 patients, the long-term prognosis for most CMS patients was favourable, with neither ventilation nor wheelchair needed at last visit. CHRNE patients did not worsen during adulthood and RAPSN patients, often severely affected in early childhood, subsequently improved.

The Hexokinase 1 5'-UTR Mutation in Charcot-Marie-Tooth 4G Disease Alters Hexokinase 1 Binding to Voltage-Dependent Anion Channel-1 and Leads to Dysfunctional Mitochondrial Calcium Buffering.

Demyelinating Charcot-Marie-Tooth 4G (CMT4G) results from a recessive mutation in the 5'UTR region of the Hexokinase 1 (HK1) gene. HK participates in mitochondrial calcium homeostasis by binding to the Voltage-Dependent Anion Channel (VDAC), through its N-terminal porin-binding domain. Our hypothesis is that CMT4G mutation results in a broken interaction between mutant HK1 and VDAC, disturbing mitochondrial calcium homeostasis. We studied a cohort of 25 CMT4G patients recruited in the French gypsy population. The disease was characterized by a childhood onset, an intermediate demyelinating pattern, and a significant phenotype leading to becoming wheelchair-bound by the fifth decade of life. Co-IP and PLA studies indicated a strong decreased interaction between VDAC and HK1 in the patients' PBMCs and sural nerve. We observed that either wild-type HK1 expression or a peptide comprising the 15 aa of the N-terminal wild-type HK1 administration decreased mitochondrial calcium release in HEK293 cells. However, mutated CMT4G HK1 or the 15 aa of the mutated HK1 was unable to block mitochondrial calcium release. Taken together, these data show that the CMT4G-induced modification of the HK1 N-terminus disrupts HK1-VDAC interaction. This alters mitochondrial calcium buffering that has been shown to be critical for myelin sheath maintenance.

Hereditary transthyretin amyloidosis in middle-aged and elderly patients with idiopathic polyneuropathy: a nationwide prospective study.

BACKGROUND: Hereditary transthyretin amyloidosis (ATTRv) is an adult-onset autosomal dominant disease resulting from TTR gene pathogenic variants. ATTRv often presents as a progressive polyneuropathy, and effective ATTRv treatments are available. METHODS: In this 5 year-long (2017-2021) nationwide prospective study, we systematically analysed the TTR gene in French patients with age >50 years with a progressive idiopathic polyneuropathy. RESULTS: 553 patients (70% males) with a mean age of 70 years were included. A TTR gene pathogenic variant was found in 15 patients (2.7%), including the Val30Met TTR variation in 10 cases. In comparison with patients with no TTR gene pathogenic variants (n = 538), patients with TTR pathogenic variants more often presented with orthostatic hypotension (53 vs. 21%, p = .007), significant weight loss (33 vs 11%, p = .024) and rapidly deteriorating nerve conduction studies (26 vs. 8%, p = .03). ATTRv diagnosis led to amyloid cardiomyopathy diagnosis in 11 cases, ATTRv specific treatment in all cases and identification of 15 additional ATTRv cases among relatives. CONCLUSION: In this nationwide prospective study, we found ATTRv in 2.7% of patients with age >50 years with a progressive polyneuropathy. These results are highly important for the early identification of patients in need of disease-modifying treatments.

Ultrasensitive digital immunoassays for SOD1 conformation in amyotrophic lateral sclerosis.

Aim: The aim of this study was to detect misfolded Cu/Zn SOD1 as a potential biomarker for amyotrophic lateral sclerosis (ALS). Materials & methods: Two ultrasensitive immunodetection assays were developed for the quantification of total and misfolded SOD1. Results: The detection of total and misfolded SOD1 was possible in human serum and cerebrospinal fluid. Total SOD1 was increased in cerebrospinal fluid from ALS patients. Misfolded SOD1 had low and variable expression in both control and ALS patient samples. Conclusion: These assays hold promise for improving our understanding of ALS and its detection, and could lead to more effective treatment options in the future. Further studies in larger cohorts are now required.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease associated with protein misfolding, including Cu/Zn SOD1. In this study, we set up a method for detecting normal and pathological misfolded SOD1 in human serum and cerebrospinal fluid. SOD1 was increased in ALS and misfolded SOD1 had low and variable expression in both control and ALS. These assays holds promise for improving our understanding of ALS and its diagnosis.

Serum neurofilament light chain cut-off definition for clinical diagnosis and prognosis of amyotrophic lateral sclerosis.

BACKGROUND: The neurofilament light chain (NfL) assay is gradually becoming an essential diagnostic tool for the diagnosis of many neurological diseases including amyotrophic lateral sclerosis (ALS). Different methods for the determination of this biomarker in serum have been developed in recent years. METHODS: We measured blood NfL in 429 patients referred to the tertiary ALS center of Montpellier, France using two different ultrasensitive methods (Ella™ and Simoa™) and we compared the clinical performances of these two approaches. We also converted NfL values into age and body mass index-adjusted Z-scores to assess cut-off values of this biomarker in this clinical context. RESULTS: We show comparable diagnostic and prognostic performance of Ella™ and Simoa™ technologies in ALS, with specificities and sensitivities exceeding 80% for both. We propose cut-off values for serum NfL in this clinical context, thus enabling the routine clinical use of this biomarker. CONCLUSION: The use of NfL in routine clinical practice will help predict survival and improve diagnostic accuracy by distinguishing ALS from other neurological diseases and motor neuron disease mimics.

Immune-mediated diseases involving central and peripheral nervous systems.

BACKGROUND AND PURPOSE: In addition to combined central and peripheral demyelination, other immune diseases could involve both the central nervous system (CNS) and peripheral nervous system (PNS). METHODS: To identify immune-mediated diseases responsible for symptomatic combined central/peripheral nervous system involvement (ICCPs), we conducted a multicentric retrospective study and assessed clinical, electrophysiological, and radiological features of patients fulfilling our ICCP criteria. RESULTS: Thirty patients (20 males) were included and followed during a median of 79.5 months (interquartile range [IQR] = 43-145). The median age at onset was 51.5 years (IQR = 39-58). Patients were assigned to one of four groups: (i) monophasic disease with concomitant CNS/PNS involvement including anti-GQ1b syndrome (acute polyradiculoneuropathy + rhombencephalitis, n = 2), checkpoint inhibitor-related toxicities (acute polyradiculoneuropathy + encephalitis, n = 3), and anti-glial fibrillary acidic protein astrocytopathy (subacute polyradiculoneuropathy and meningoencephalomyelitis with linear gadolinium enhancements, n = 2); (ii) chronic course with concomitant CNS/PNS involvement including paraneoplastic syndromes (ganglionopathy/peripheral hyperexcitability + limbic encephalitis, n = 4); (iii) chronic course with sequential CNS/PNS involvement including POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes) syndrome (polyradiculoneuropathy + strokes, n = 2), histiocytosis (polyradiculoneuropathy + lepto-/pachymeningitis, n = 1), and systemic vasculitis (multineuropathy + CNS vasculitis/pachymeningitis, n = 2); and (iv) chronic course with concomitant or sequential CNS/PNS involvement including combined central and peripheral demyelination (polyradiculoneuropathy + CNS demyelinating lesions, n = 10) and connective tissue diseases (ganglionopathy/radiculopathy/multineuropathy + limbic encephalitis/transverse myelitis/stroke, n = 4). CONCLUSIONS: We diagnosed nine ICCPs. The timing of central and peripheral manifestations and the disease course help determine the underlying immune disease. When antibody against neuroglial antigen is identified, CNS and PNS involvement is systematically concomitant, suggesting a common CNS/PNS antigen and a simultaneous disruption of blood-nerve and blood-brain barriers.

The SOD1-mediated ALS phenotype shows a decoupling between age of symptom onset and disease duration.

Superoxide dismutase (SOD1) gene variants may cause amyotrophic lateral sclerosis, some of which are associated with a distinct phenotype. Most studies assess limited variants or sample sizes. In this international, retrospective observational study, we compare phenotypic and demographic characteristics between people with SOD1-ALS and people with ALS and no recorded SOD1 variant. We investigate which variants are associated with age at symptom onset and time from onset to death or censoring using Cox proportional-hazards regression. The SOD1-ALS dataset reports age of onset for 1122 and disease duration for 883 people; the comparator population includes 10,214 and 9010 people respectively. Eight variants are associated with younger age of onset and distinct survival trajectories; a further eight associated with younger onset only and one with distinct survival only. Here we show that onset and survival are decoupled in SOD1-ALS. Future research should characterise rarer variants and molecular mechanisms causing the observed variability.

Spatio-temporal clustering of amyotrophic lateral sclerosis in France: A population-based study.

OBJECTIVE: To assess spatial aggregates of amyotrophic lateral sclerosis (ALS) incident cases, using a solid geo-epidemiological statistical method, in France. METHODS: This population-based study (2003-2011) investigated 47.1 million person-years of follow-up (PYFU). Case ascertainment of incident ALS cases was based on multiple sources (ALS referral centers, hospital centres and health insurance data). Neurologists confirmed all ALS diagnoses. Exhaustiveness was estimated through capture-recapture. Aggregates were investigated in four steps: (a) geographical modelling (standardized incidence ratio (SIR) calculation), (b) analysis of the spatial distribution of incidence (Phothoff-Winttinghill's test, Global Moran's Index, Kulldorf's spatial scan statistic, Local Moran's Index), (c) classification of the level of certainty of spatial aggregates (i.e. definite cluster; probable over-incidence area; possible over-incidence area) and (d) evaluation of the robustness of the results. RESULTS: The standardized incidence of ALS was 2.46/100,000 PYFU (95% CI 2.31-2.63, European population as reference) based on 1199 incident cases. We identified 13 areas of spatial aggregates: one cluster (stable in robustness analysis), five probable over-incidence areas (2 stable in robustness analysis) and seven possible over-incidence areas (including 4 stable areas in robustness analysis). A cluster was identified in the Rhône-Alpes region: 100 observed vs 54.07 expected cases for 2,411,514 PYFU, SIR: 1.85 (95% CI 1.50-2.25). CONCLUSION: We report here one of the largest investigations of incidence and spatial aggregation of ALS ever performed in a western country. Using a solid methodology framework for case ascertainment and cluster analysis, we identified 13 areas that warrant further investigation.

HINT1 neuropathy: Expanding the genotype and phenotype spectrum.

Inherited peripheral neuropathy (IPN) is a heterogeneous group of disorders due to pathogenic variation in more than 100 genes. In 2012, the first cases of IPN associated with HINT1 pathogenic variations were described in 33 families sharing the same phenotype characterized by an axonal neuropathy with neuromyotonia and autosomal recessive inheritance (NMAN: OMIM #137200). Histidine Triad Nucleotide Binding Protein 1 regulates transcription, cell-cycle control, and is possibly involved in neuropsychiatric pathophysiology. Herein, we report seven French patients with NMAN identified by Next Generation Sequencing. We conducted a literature review and compared phenotypic and genotypic features with our cohort. We identified a new HINT1 pathogenic variation involved in NMAN: c.310G>C p.(Gly104Arg). This cohort is comparable with literature data regarding age of onset (7,4yo), neuronal involvement (sensorimotor 3/7 and motor pure 4/7), and skeletal abnormalities (scoliosis 3/7, feet anomalies 6/7). We expand the phenotypic spectrum of HINT1-related neuropathy by describing neurodevelopmental or psychiatric features in six out of seven individuals such as generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), mood disorder and attention deficit hyperactivity disorder (ADHD). However, only 3/128 previously described patients had neuropsychiatric symptomatology or neurodevelopmental disorder. These features could be part of HINT1-related disease, and we should further study the clinical phenotype of the patients.

Repeated neurofilament light chain measurements did not capture Riluzole therapeutic effect in amyotrophic lateral sclerosis patients.

BACKGROUND: Little is known about the influence of Riluzole on serum neurofilament light chain (sNfL) levels, a biomarker of prognosis in amyotrophic lateral sclerosis (ALS), and variations with time of sNfL concentrations are controversial. METHODS: Sera from ALS patients (n = 141) and controls (n = 33) were collected at inclusion (sNfL1) and second visit (sNfL2, mean delay 10.4 ± 8.7 months). sNfL levels, determined by single-molecule array, were compared between ALS and controls at both time points. sNfL concentration changes were compared between patients with Riluzole (w/Ril) at inclusion in the study and those who were treated by Riluzole following inclusion (w/o Ril). The factors influencing sNfL concentrations and changes were studied using linear regression and multivariate analysis. RESULTS: sNfL levels were higher in ALS patients than in controls at the two time points (p < 0.00001). In ALS patients, sNfL concentrations were higher in females for both sNfL1 (p = 0.014) and sNfL2 (p < 0.001). In the whole ALS group, sNfL levels were higher at sNfL2 than at sNfL1 (p < 0.001). sNfL1 and sNfL2 concentrations were similar between the two ALS subgroups (w/ and w/o Ril). ALS functional rating scale-revised rate of decline and gender were the two main factors significantly influencing both sNfL1 and sNfL2 levels (p < 0.01). However, only gender was shown to significantly influence sNfL changes with time (p = 0.003). CONCLUSIONS: In this study, sNfL levels increased with time in ALS patients and there was no difference between subjects already treated by Riluzole and those treated after sNfL1. Further studies with larger population samples and different sampling intervals are warranted to better determine the real potential of sNfL measurement as a tool to monitor treatment response in ALS.

Compound heterozygous P67S/D91A SOD1 mutations in an ALS family with apparently sporadic case.

Objectives: To describe a family with heterozygous P67S and D91A SOD1 mutations. Methods: The ALS profile of the proband was described. SOD1 gene sequencing was performed in the proband and his children. Results: The affected individual presented with progressive left peripheral facial palsy and slow progression with late limb involvement. Unequivocal upper and lower motor neuron signs were present, together with diffuse denervation at myography. The absence of trigeminal involvement excluded a FOSMN syndrome. Pedigree analysis did not show any other ALS case in the family. Genetic analysis of this patient showed P67S and D91A SOD1 mutations. The genetic analysis of the children showed that the mutations were each one carried by a different chromosome. Conclusions: P67S SOD1 mutation has been described in several ALS cases, either with familial or apparently sporadic ALS. The mutation is located in a mutational hotspot and was predicted pathogenic by in silico prediction software. The study of phylogenetic data show that at this codon, the proline is highly conserved throughout species reinforcing causality. Conversely, the D91A variant is known to have a recessive influence. Unilateral motor facial involvement, even after several years, in an ALS patient is unusual. The present case with compound heterozygosity and unusual onset in a patient with apparently sporadic ALS, widens the clinical spectrum of the disease and adds further arguments to support the systematic genetic screening of all ALS cases in referral ALS clinics.

Reversible sub-acute motor neuron syndrome after mushroom intoxication masquerading as amyotrophic lateral sclerosis.

A 56-year-old man presented with rapidly evolving/sub-acute upper and lower motor neuron syndrome in 2015 with significant weakness in the four limbs and the bulbar region. Amyotrophic lateral sclerosis functional rating scale-revised (ALSFRS-r) was rated 34/48. On electromyography, there was a diffuse and active denervation in the four limbs and the tongue. A diagnosis of definite ALS according to international criteria was made. Six months later the patient stopped worsening. In the following years he progressively recovered. ALSFRS-r score improved to reach 48/48 in 2021. His neurological examination is normal and electromyography shows no denervation. Inquiry revealed that he presented a few months and, again a few days before onset, a mushroom poisoning. He was used to eating false morels either crude or undercooked and developed muscles cramps, nausea and vertigo. The relationships between this reversible sub-acute motor neuron syndrome and mushroom intoxication are discussed in the light of the recently described cluster in the Alps with a high incidence of ALS cases. Epidemiological investigations showed that all patients, but not their spouses, used to eat crude or undercooked false morels. Such a mushroom contains hydrazines, a known neurotoxic agent. We are not aware of another case of ALS reversal in that cluster area. We propose that a potential mushroom poisoning be thoroughly searched for when facing with a patient with sub-acute or rapidly worsening ALS syndrome.

Increased worsening of amyotrophic lateral sclerosis patients during Covid-19-related lockdown in France.

Covid-19-related lockdown (LD) in France precluded in-person follow-up in referral ALS centers. ALS patients' evolution and worsening before and during LD were studied to analyze its impact. A total of 84 patients were identified. The monthly rate of ALSFRS-R decline during LD was 1.06 ± 1.42 and was significantly increased compared to the pre-LD period, 0.58 ± 0.73, corresponding to an 83% increase (p = 0.007). Weight loss was unchanged between pre-LD and LD, gender and site of onset did not influence the rates of change of ALSFRS-R score. Several factors may be implicated in this increased severity of ALS during LD, such as psychological consequences of LD, interruptions of physiotherapy and speech therapy, or in-patient visits both to the tertiary center and the GP. Physicians and health authorities should be aware of that, in order to prevent the consequences of future sanitary restrictions.

Low 25OH Vitamin D Blood Levels Are Independently Associated With Higher Amyotrophic Lateral Sclerosis Severity Scores: Results From a Prospective Study.

Background: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive degeneration of upper and lower motor neurons. Prognosis is highly variable, ranging from few months to more than 30 years. 25OH vitamin D (25OH VD) blood levels have been associated with worse prognosis of ALS, but these results remain in dispute. We addressed this controversy with a prospective study and multivariate analysis to study the influence of known clinical prognostic factors of the disease and 25OH VD levels on Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) severity score (ALS-SS), as defined by the monthly rate of decline of ALSFRS-R score, to identify the factors most closely linked to the risk of worsening of the disease. Results:This prospective cohort of ALS patients recruited 127 individuals, and 105 of them met inclusion criteria. Mean age of onset was 62.2 ± 12.1 years, 32% of subjects had bulbar onset, and gender ratio was 1.44 (male/female). Mean 25OH VD level was 26.8 ± 10.8 ng/ml and was similar between males and females. Patients with 25OH VD levels <15 ng/ml had significantly higher ALS-SS at inclusion (ALS-SSi) than those with normal levels (>30 ng/ml), p = 0.011. The study of ALS-SS as calculated at the end of follow-up (ALS-SSe) was not found correlated to initial 25OH VD levels (r = -0.19; p = 0.084). Univariate analysis showed that ALS-SSe correlated with 25OH VD levels, ALS duration at inclusion, slow vital capacity (SVC) at inclusion, and SVC loss. Multivariate model showed that 25OH VD levels were independently associated with ALS-SSe: r = -0.0125, p = 0.033. Log rank test with Kaplan-Meier curves did not show significant differences of survival between the groups defined by 25OH VD levels: <15, >15 and <30, and > 30 ng/ml, p = 0.88. Conclusions: This prospective study in ALS patients confirmed previous retrospective results: ALS-SSi is significantly higher in patients with severe VD deficiency. For the first time, multivariate analysis showed that 25OH VD level was an independent prognostic factor correlated to ALS-SSe, suggesting that discrepancies between previous works could be due to confounders. It would be important that the present work be replicated in larger samples to confirm the present findings.

Clinical Phenotype and Inheritance in Patients With C9ORF72 Hexanucleotide Repeat Expansion: Results From a Large French Cohort.

BACKGROUND: In familial amyotrophic lateral sclerosis (ALS) cases, the presence of an abnormal C9ORF72 repeat expansion (C9RE) is the most frequent genetic cause identified. Various clinical phenotypes have been described in relation to the presence of C9RE, including psychiatric disorders or Huntington-like symptoms. In a subset of sporadic ALS, C9RE has also been described. In the present study, all index cases with ALS and C9RE identified in our center and their clinical profile, as well as neurological and psychiatric characteristics of identified family members, were described. Clinical characteristics of ALS patients were compared to 999 patients with sporadic ALS (SALS) from our database. RESULTS: From the 70 index cases with ALS identified, a total of 200 individuals were studied, 118 with ALS, 32 with fronto-temporal lobe degeneration (FTD), 37 with ALS/FTD, and 13 with psychiatric disorders. A familial history was present in 57 of the index cases (81%). In ALS and ALS/FTD cases with C9RE, the age of onset (AoO) was earlier than that in SALS cases, p < 0.0001 and p = 0.008, respectively. Sporadic cases with C9REALS (n = 13) had an earlier AoO compared to familial C9REALS ones, p < 0.0001. Within families, there was an earlier AoO in index cases and their siblings compared to their parental generation (p < 0.01). There was also a significant intrafamilial correlation for bulbar onset of ALS. The parental generation had significant female predominance compared to index cases and their siblings (sex ratio 0.47 vs. 1.4, p = 0.004), and this predominance was also present when considering parent-child pairs. In the group with psychiatric disorders, suicide was prominent (n = 9) and mean age was 54 years. CONCLUSION: Although our sample size is rather limited, the earlier AoO in index cases and their siblings compared to the parental generation may suggest an anticipation. Reasons for predominance of female transmission are unclear, but the hypothesis that gender influences transmission of the genetic trait or C9RE size variation may be taken into account. Intrafamilial correlation suggests that genetic aspects underlie the occurrence of bulbar onset in ALS patients. Studies on larger samples are warranted to confirm those results.