Promises and pitfalls of imaging-based biomarkers in motor neuron diseases.

PURPOSE OF REVIEW: Although neuroimaging in motor neuron diseases (MNDs) continues to generate important novel academic insights, the translation of novel radiological protocols into viable biomarkers remains challenging. RECENT FINDINGS: A multitude of technological advances contribute to the success of academic imaging in MND such as the availability of high-field MRI platforms, novel imaging techniques, quantitative spinal cord protocols to whole-brain spectroscopy. International collaborations, protocol harmonization efforts, open-source image analysis suites also fuel developments in the field. Despite the success of academic neuroimaging in MND, the meaningful interpretation of radiological data from single patients and accurate classification into relevant diagnostic, phenotypic and prognostic categories remain challenging. Appraising accruing disease burden over the short follow-up intervals typically used in pharmacological trials is also notoriously difficult. SUMMARY: Although we acknowledge the academic achievements of large descriptive studies, an unmet priority of neuroimaging in MND is the development of robust diagnostic, prognostic and monitoring applications to meet the practical demands of clinical decision-making and pharmacological trials. A paradigm shift from group-level analyses to individual-level data interpretation, accurate single-subject classification and disease-burden tracking is therefore urgently needed to distil raw spatially coded imaging data into practical biomarkers.

Time for optimism in amyotrophic lateral sclerosis.

BACKGROUND AND PURPOSE: Amyotrophic lateral sclerosis (ALS) is among the most common motor neuron diseases in adults. Nevertheless, ALS remains fatal, despite decades of research and clinical trials, which has led to negative conclusions until recently in regard to four specific treatments. It is well known that we can learn from failures, and we consider that the time has come to present positive insight on this disease. METHODS: We did a literature search using PubMed and Scopus for articles published in English from 1 January 2016, to 30 June 2022 dealing with "amyotrophic lateral sclerosis", diagnosis, treatment, and biomarkers. RESULTS: A comprehensive review of the literature on diagnosis, monitoring, and treatment of this condition showed convincing evidence that we are now able to diagnose earlier as well as to better monitor and treat ALS. CONCLUSIONS: Although ALS is often difficult to diagnose and remains incurable, there are many indications that an optimistic view of ALS management in the coming years is now realistic.

A retrospective analysis of all-cause and cause-specific mortality rates in French male professional footballers.

This study retrospectively compared all-cause and cause-specific mortality in French male professional football players with data from France's national population. Altogether, 6114 individuals born in Metropolitan France or in one of its overseas territories who played at least one competitive match in France's professional football championships between January 1, 1968 and December 31, 2015, were identified and followed up for vital status obtained from a national reference database until December 31, 2015. Data on all-cause and cause-specific mortality were subsequently compared to the expected number of deaths for the national population after standardization for the year, age, and sex. Ratios between observed and expected deaths provided standardized mortality ratios (SMR) along with 95% confidence intervals (95% CI). Linear trends were investigated using the Poisson trend test. Altogether, 662 player deaths were observed. All-cause mortality overall was lower than that of the national population (SMR: 0.69, 95% CI 0.64-0.75). An excess of deaths from dementia was observed in the players (SMR: 3.38, 95% CI: 2.49-4.50) whereas mortality from diseases of the nervous (SMR: 0.64, 95% CI: 0.35-1.08) and cardiovascular systems (SMR: 0.82, 95% CI: 0.70-0.96), and cancer (SMR: 0.67, 95% CI: 0.58-0.76) was lower. Lower overall mortality and that owing to common cardiovascular and cancer-related diseases were reported in French professional football players compared to France's national population. In line with previous studies, however, excess mortality from dementia was observed in the players. Career length was not associated with all-cause or cause-specific mortality. Prospective matched-cohort studies are necessary to identify the neurologic impact of participation in professional football.

The Amyotrophic Lateral Sclerosis M114T PFN1 Mutation Deregulates Alternative Autophagy Pathways and Mitochondrial Homeostasis.

Mutations in profilin 1 (PFN1) have been identified in rare familial cases of Amyotrophic Lateral Sclerosis (ALS). PFN1 is involved in multiple pathways that could intervene in ALS pathology. However, the specific pathogenic role of PFN1 mutations in ALS is still not fully understood. We hypothesized that PFN1 could play a role in regulating autophagy pathways and that PFN1 mutations could disrupt this function. We used patient cells (lymphoblasts) or tissue (post-mortem) carrying PFN1 mutations (M114T and E117G), and designed experimental models expressing wild-type or mutant PFN1 (cell lines and novel PFN1 mice established by lentiviral transgenesis) to study the effects of PFN1 mutations on autophagic pathway markers. We observed no accumulation of PFN1 in the spinal cord of one E117G mutation carrier. Moreover, in patient lymphoblasts and transfected cell lines, the M114T mutant PFN1 protein was unstable and deregulated the RAB9-mediated alternative autophagy pathway involved in the clearance of damaged mitochondria. In vivo, motor neurons expressing M114T mutant PFN1 showed mitochondrial abnormalities. Our results demonstrate that the M114T PFN1 mutation is more deleterious than the E117G variant in patient cells and experimental models and suggest a role for the RAB9-dependent autophagic pathway in ALS.

Split-hand and split-limb phenomena in amyotrophic lateral sclerosis: pathophysiology, electrophysiology and clinical manifestations.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting the upper and lower motor neurons. A key clinical feature of ALS is the absence of accurate, early-stage diagnostic indicators. 'Split-hand syndrome' was first described in ALS at the end of the last century and a considerable body of literature suggests that the split-hand phenomenon may be an important clinical feature of ALS. Considering the published investigations, it is conceivable that the 'split-hand syndrome' results from the associated upper and lower motor neuron degeneration, whose interaction remains to be fully clarified. Additionally, other split syndromes have been described in ALS involving upper or lower limbs, with a nuanced description of clinical and neurophysiological manifestations that may further aid ALS diagnosis. In this review, we endeavour to systematically present the spectrum of the 'split syndromes' in ALS from a clinical and neurophysiology perspective and discuss their diagnostic and pathogenic utility.

Effect of familial clustering in the genetic screening of 235 French ALS families.

OBJECTIVES: To determine whether the familial clustering of amyotrophic lateral sclerosis (ALS) cases and the phenotype of the disease may help identify the pathogenic genes involved. METHODS: We conducted a targeted next-generation sequencing analysis on 235 French familial ALS (FALS), unrelated probands to identify mutations in 30 genes linked to the disease. The genealogy, that is, number of cases and generations with ALS, gender, age, site of onset and the duration of the disease were analysed. RESULTS: Regarding the number of generations, 49 pedigrees had only one affected generation, 152 had two affected generations and 34 had at least three affected generations. Among the 149 pedigrees (63.4%) for which a deleterious variant was found, an abnormal G4C2 expansion in C9orf72 was found in 98 cases as well as SOD1, TARBP or FUS mutations in 30, 9 and 7 cases, respectively. Considering pedigrees from the number of generations, abnormal G4C2 expansion in C9orf72 was more frequent in pedigrees with pairs of affected ALS cases, which represented 65.2% of our cohort. SOD1 mutation involved all types of pedigrees. No TARDBP nor FUS mutation was present in monogenerational pedigrees. TARDBP mutation predominated in bigenerational pedigrees with at least three cases and FUS mutation in multigenerational pedigrees with more than seven cases, on average, and with an age of onset younger than 45 years. CONCLUSION: Our results suggest that familial clustering, phenotypes and genotypes are interconnected in FALS, and thus it might be possible to target the genetic screening from the familial architecture and the phenotype of ALS cases.

Neural Correlates of Motor Imagery of Gait in Amyotrophic Lateral Sclerosis.

BACKGROUND: Gait impairment is poorly characterized in amyotrophic lateral sclerosis (ALS), despite increasing evidence of extrapyramidal and cerebellar dysfunction. Gait impairment adds to the considerable motor disability of ALS patients and requires targeted multidisciplinary interventions. PURPOSE: To assess gait imagery-specific networks and functional adaptation in ALS. STUDY TYPE: Prospective. POPULATION: Seventeen ALS patients with lower motor neuron predominant (LMNp) disability, 14 patients with upper motor neurons predominant (UMNp) disease, and 14 healthy controls were included. FIELD STRENGTH/SEQUENCES: 3T / gradient echo echo planar (GE-EPI). ASSESSMENT: Subjects performed a dual motor imagery task: normal and precision gait. The Movement Imagery Questionnaire - Revised Second Version (MIQ-rs) was used to appraise movement imagery in each participant. Study group-specific activation patterns were evaluated during motor imagery of gait. Additional generalized psychophysiological interaction analyses were carried out using the supplementary motor area, caudate, cerebellum, and superior parietal lobule as seed regions. STATISTICAL TESTS: Repeated-measures analysis of variance (ANOVA) was used to compare time imagery and MIQ-rs scores between groups. Size effects were also reported as partial eta squared (η2). One-way ANOVA was performed to explore differences in terms of connexions during motor imagery tasks. RESULTS: A significant increase in imagery time in UMNp patients compared to controls (P < 0.05) and LMNp (P < 0.05) during imagined gait was demonstrated. UMNp patients exhibited altered supplementary motor area, precentral gyrus, superior parietal lobule, and dorsolateral prefrontal cortex activation and increased orbitofrontal (pFDR(False Discovery Rate) < 0.05), posterior parietal (pFDR < 0.05) caudate (pFDR < 0.05), and cerebellar (pFDR < 0.05) signal during imagined locomotion. Increased effective connectivity of the striato-cerebellar and parieto-cerebellar circuits was also demonstrated. Additional activation was detected in the insula and cingulate cortex. DATA CONCLUSION: Enhanced striato- and parieto-cerebellar networks in UMNp ALS patients are likely to represent a compensatory response to impaired postural control. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 5.

Presymptomatic spinal cord pathology in c9orf72 mutation carriers: A longitudinal neuroimaging study.

OBJECTIVE: C9orf72 hexanucleotide repeats expansions account for almost half of familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) cases. Recent imaging studies in asymptomatic C9orf72 carriers have demonstrated cerebral white (WM) and gray matter (GM) degeneration before the age of 40 years. The objective of this study was to characterize cervical spinal cord (SC) changes in asymptomatic C9orf72 hexanucleotide carriers. METHODS: Seventy-two asymptomatic individuals were enrolled in a prospective study of first-degree relatives of ALS and FTD patients carrying the c9orf72 hexanucleotide expansion. Forty of them carried the pathogenic mutation (C9+ ). Each subject underwent quantitative cervical cord imaging. Structural GM and WM metrics and diffusivity parameters were evaluated at baseline and 18 months later. Data were analyzed in C9+ and C9- subgroups, and C9+ subjects were further stratified by age. RESULTS: At baseline, significant WM atrophy was detected at each cervical vertebral level in C9+ subjects older than 40 years without associated changes in GM and diffusion tensor imaging parameters. At 18-month follow-up, WM atrophy was accompanied by significant corticospinal tract (CST) fractional anisotropy (FA) reductions. Intriguingly, asymptomatic C9+ subjects older than 40 years with family history of ALS (as opposed to FTD) also exhibited significant CST FA reduction at baseline. INTERPRETATION: Cervical SC imaging detects WM atrophy exclusively in C9+ subjects older than 40 years, and progressive CST FA reductions can be identified on 18-month follow-up. Cervical SC magnetic resonance imaging readily captures presymptomatic pathological changes and disease propagation in c9orf72-associated conditions. ANN NEUROL 2019;86:158-167.

Absence of hyperexcitability of spinal motoneurons in patients with amyotrophic lateral sclerosis.

KEY POINTS: •Amyotrophic lateral sclerosis (ALS) motoneurons become hypoexcitable with disease progression in experimental models, raising questions about the neural hyperexcitability supported by clinical observations. •A variant of the ∆F method, based on motor unit discharge frequency modulations during recruitment and derecruitment, has been developed to investigate the motoneuron capacity to self-sustained discharge in patients. •The modulation of motor unit firing rate during ramp contraction and vibration-induced recruitment are modified in ALS, suggesting lower motoneuron capacity to self-sustained discharge, which is a sign of hypoexcitability. •∆F-D decreases with functional impairment and its reduction is more pronounced in fast progressors. •In patients with ALS, motoneurons exhibit hypoexcitability, which increases with disease progression. ABSTRACT: Experimental models have primarily revealed spinal motoneuron hypoexcitability in amyotrophic lateral sclerosis (ALS), which is contentious considering the role of glutamate-induced excitotoxicity in neurodegeneration and clinical features rather supporting hyperexcitability. This phenomenon was evaluated in human patients by investigating changes in motor unit firing during contraction and relaxation. Twenty-two ALS patients with subtle motor deficits and 28 controls performed tonic contractions of extensor carpi radialis, triceps brachialis, tibialis anterior and quadriceps, aiming to isolate a low-threshold unit (U1) on the electromyogram (EMG). Subsequently, they performed a stronger contraction or tendon vibration was delivered, to recruit higher threshold unit (U2) for 10 s before they relaxed progressively. EMG and motor unit potential analyses suggest altered neuromuscular function in all muscles, including those with normal strength (Medical Research Council score at 5). During the preconditioning tonic phase, U1 discharge frequency did not differ significantly between groups. During recruitment, the increase in U1 frequency (∆F-R) was comparable between groups both during contraction and tendon vibration. During derecruitment, the decrease in U1 frequency (∆F-D) was reduced in ALS regardless of the recruitment mode, particularly for ∆F-R <8 Hz in the upper limbs, consistent with the muscle weakness profile of the group. ∆F-D was associated with functional disability and its reduction was more pronounced in patients with more rapid disease progression rate. This in vivo study has demonstrated reduced motoneuron capacity for self-sustained discharge, and further supports that motoneurons are normo- to hypoexcitable in ALS patients, similar to observations in experimental models.

The changing landscape of motor neuron disease imaging: the transition from descriptive studies to precision clinical tools.

PURPOSE OF REVIEW: Neuroimaging in motor neuron disease (MND) has traditionally been seen as an academic tool with limited direct relevance to individualized patient care. This has changed radically in recent years as computational imaging has emerged as a viable clinical tool with true biomarker potential. This transition is not only fuelled by technological advances but also by important conceptual developments. RECENT FINDINGS: The natural history of MND is now evaluated by presymptomatic, postmortem and multi-timepoint longitudinal imaging studies. The anatomical spectrum of MND imaging has also been expanded from an overwhelmingly cerebral focus to innovative spinal and muscle applications. In contrast to the group-comparisons of previous studies, machine-learning and deep-learning approaches are increasingly utilized to model real-life diagnostic dilemmas and aid prognostic classification. The focus from evaluating focal structural changes has shifted to the appraisal of network integrity by connectivity-based approaches. The armamentarium of MND imaging has also been complemented by novel PET-ligands, spinal toolboxes and the availability of magnetoencephalography and high-field magnetic resonance (MR) imaging platforms. SUMMARY: In addition to the technological and conceptual advances, collaborative multicentre research efforts have also gained considerable momentum. This opinion-piece reviews emerging trends in MND imaging and their implications to clinical care and drug development.

Cortical drive to breathe in amyotrophic lateral sclerosis: a dyspnoea-worsening defence?

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease causing diaphragm weakness that can be partially compensated by inspiratory neck muscle recruitment. This disappears during sleep, which is compatible with a cortical contribution to the drive to breathe. We hypothesised that ALS patients with respiratory failure exhibit respiratory-related cortical activity, relieved by noninvasive ventilation (NIV) and related to dyspnoea.We studied 14 ALS patients with respiratory failure. Electroencephalographic recordings (EEGs) and electromyographic recordings of inspiratory neck muscles were performed during spontaneous breathing and NIV. Dyspnoea was evaluated using the Multidimensional Dyspnea Profile.Eight patients exhibited slow EEG negativities preceding inspiration (pre-inspiratory potentials) during spontaneous breathing. Pre-inspiratory potentials were attenuated during NIV (p=0.04). Patients without pre-inspiratory potentials presented more advanced forms of ALS and more severe respiratory impairment, but less severe dyspnoea. Patients with pre-inspiratory potentials had stronger inspiratory neck muscle activation and more severe dyspnoea during spontaneous breathing.ALS-related diaphragm weakness can engage cortical resources to augment the neural drive to breathe. This might reflect a compensatory mechanism, with the intensity of dyspnoea a negative consequence. Disease progression and the corresponding neural loss could abolish this phenomenon. A putative cognitive cost should be investigated.

Gait Performance and Use of Mental Imagery as a Measure of Disease Progression in Amyotrophic Lateral Sclerosis.

OBJECTIVE: Gait and balance are key determinants of disease status in amyotrophic lateral sclerosis (ALS). This study aims at testing the relationship between the imagery of gait and disability in patients with ALS. METHODS: Twenty-five consecutive patients (63.8 ± 2.4 years; 52% female) performed the timed up and go (TUG) test and a validated imagined version of the TUG between March 2011 and May 2012. The revised ALS functional rating score (ALSFRS-R) was assessed simultaneously. RESULTS: The mean duration of TUG (16.7 ± 2.2 s) was significantly longer than imagined TUG (iTUG; 10.5 ± 1.4 s, p < 0.001). The TUG (R2 = 0.40, p = 0.001) and the iTUG (R2 = 0.30, p = 0.007) were significantly associated with results of the ALSFRS-R score (37.0 ± 7.3) as well as with muscle strength in arms (TUG R2 = 0.42, p < 0.001, iTUG R2 = 0.38, p = 0.001) and legs (TUG R2 = 0.47, p < 0.001, iTUG R2 = 0.46, p < 0.001). TUG and iTUG increased with age (TUG R2 = 0.18, p = 0.04, iTUG R2 = 0.12, p = 0.05). CONCLUSION: ALS patients performed the imagined gait faster than the real gait. Both TUG and iTUG correlated with disability measured by the ALSFRS-R score and by muscle strength. These inexpensive and easy clinical tests represent promising tools in clinical practice to study gait in ALS.

Deciphering spreading mechanisms in amyotrophic lateral sclerosis: clinical evidence and potential molecular processes.

PURPOSE OF REVIEW: The aim of this review is to refer to recent arguments supporting the existence of specific propagation mechanisms associated with spreading of neuron injury in amyotrophic lateral sclerosis (ALS). RECENT FINDINGS: Misfolded ALS-linked protein accumulation can induce aggregation of their native equivalent isoforms through a mechanism analogous to the infectious prion proteins initiation and its propagation. SUMMARY: Although ALS is clinically heterogeneous, a shared characteristic is the focal onset and the progressive extension to all body regions. Being viewed until now as just summation of the increased number of affected neurons, dispersion is now rather considered as the result of a seeded self-propagating process. A sequential regional spreading pattern is supported by the distribution of TDP-43 aggregates in ALS autopsy cases. Electrophysiology and advanced neuroimaging methods also recently provided some evidence for propagation of lesions both in the brain and spinal cord, more longitudinal studies being still needed. Lesions are supposed to spread cell-to-cell regionally or through connected neuronal pathway. At the molecular level, the prion-like spreading is an emerging mechanism hypothesis, but other machineries such as those that are in charge of dealing with misfolded proteins and secretion of deleterious peptides may be involved in the propagation of neuron loss. Deciphering the mechanisms underlying spreading of ALS symptoms is of crucial importance to better understand this neurodegenerative disease, build new and appropriate animal models and to define novel therapeutic targets.

Validation of a semiautomated spinal cord segmentation method.

PURPOSE: To validate semiautomated spinal cord segmentation in healthy subjects and patients with neurodegenerative diseases and trauma. MATERIALS AND METHODS: Forty-nine healthy subjects, as well as 29 patients with amyotrophic lateral sclerosis, 19 with spinal muscular atrophy, and 14 with spinal cord injuries were studied. Cord area was measured from T2 -weighted 3D turbo spin echo images (cord levels from C2 to T9) using the semiautomated segmentation method of Losseff et al (Brain [1996] 119(Pt 3):701-708), compared with manual segmentation. Reproducibility was evaluated using the inter- and intraobserver coefficient of variation (CoV). Accuracy was assessed using the Dice similarity coefficient (DSC). Robustness to initialization was assessed by simulating modifications to the contours drawn manually prior to segmentation. RESULTS: Mean interobserver CoV was 4.00% for manual segmentation (1.90% for Losseff's method) in the cervical region and 5.62% (respectively 2.19%) in the thoracic region. Mean intraobserver CoV was 2.34% for manual segmentation (1.08% for Losseff's method) in the cervical region and 2.35% (respectively 1.34%) in the thoracic region. DSC was high (0.96) in both cervical and thoracic regions. DSC remained higher than 0.8 even when modifying initial contours by 50%. CONCLUSION: The semiautomated segmentation method showed high reproducibility and accuracy in measuring spinal cord area.

Selective disruption of acetylcholine synthesis in subsets of motor neurons: a new model of late-onset motor neuron disease.

Motor neuron diseases are characterized by the selective chronic dysfunction of a subset of motor neurons and the subsequent impairment of neuromuscular function. To reproduce in the mouse these hallmarks of diseases affecting motor neurons, we generated a mouse line in which ~40% of motor neurons in the spinal cord and the brainstem become unable to sustain neuromuscular transmission. These mice were obtained by conditional knockout of the gene encoding choline acetyltransferase (ChAT), the biosynthetic enzyme for acetylcholine. The mutant mice are viable and spontaneously display abnormal phenotypes that worsen with age including hunched back, reduced lifespan, weight loss, as well as striking deficits in muscle strength and motor function. This slowly progressive neuromuscular dysfunction is accompanied by muscle fiber histopathological features characteristic of neurogenic diseases. Unexpectedly, most changes appeared with a 6-month delay relative to the onset of reduction in ChAT levels, suggesting that compensatory mechanisms preserve muscular function for several months and then are overwhelmed. Deterioration of mouse phenotype after ChAT gene disruption is a specific aging process reminiscent of human pathological situations, particularly among survivors of paralytic poliomyelitis. These mutant mice may represent an invaluable tool to determine the sequence of events that follow the loss of function of a motor neuron subset as the disease progresses, and to evaluate therapeutic strategies. They also offer the opportunity to explore fundamental issues of motor neuron biology.

Muscle histone deacetylase 4 upregulation in amyotrophic lateral sclerosis: potential role in reinnervation ability and disease progression.

Amyotrophic lateral sclerosis is a typically rapidly progressive neurodegenerative disorder affecting motor neurons leading to progressive muscle paralysis and death, usually from respiratory failure, in 3-5 years. Some patients have slow disease progression and prolonged survival, but the underlying mechanisms remain poorly understood. Riluzole, the only approved treatment, only modestly prolongs survival and has no effect on muscle function. In the early phase of the disease, motor neuron loss is initially compensated for by collateral reinnervation, but over time this compensation fails, leading to progressive muscle wasting. The crucial role of muscle histone deacetylase 4 and its regulator microRNA-206 in compensatory reinnervation and disease progression was recently suggested in a mouse model of amyotrophic lateral sclerosis (transgenic mice carrying human mutations in the superoxide dismutase gene). Here, we sought to investigate whether the microRNA-206-histone deacetylase 4 pathway plays a role in muscle compensatory reinnervation in patients with amyotrophic lateral sclerosis and thus contributes to disease outcome differences. We studied muscle reinnervation using high-resolution confocal imaging of neuromuscular junctions in muscle samples obtained from 11 patients with amyotrophic lateral sclerosis, including five long-term survivors. We showed that the proportion of reinnervated neuromuscular junctions was significantly higher in long-term survivors than in patients with rapidly progressive disease. We analysed the expression of muscle candidate genes involved in the reinnervation process and showed that histone deacetylase 4 upregulation was significantly greater in patients with rapidly progressive disease and was negatively correlated with the extent of muscle reinnervation and functional outcome. Conversely, the proposed regulator of histone deacetylase 4, microRNA-206, was upregulated in both patient groups, but did not correlate with disease progression or reinnervation. We conclude that muscle expression of histone deacetylase 4 may be a key factor for muscle reinnervation and disease progression in patients with amyotrophic lateral sclerosis. Specific histone deacetylase 4 inhibitors may then constitute a therapeutic approach to enhancing motor performance and slowing disease progression in amyotrophic lateral sclerosis.