Degeneration Of Upper Motor Neurons Research Articles

Neuromuscular junction in amyotrophic lateral sclerosis. Is there more to follow?

Background. Amyotrophic lateral sclerosis (ALS) causes progressive degeneration of upper motor neurons in the cortex, and lower motor neurons in the spine. In addition, it is unclear where motor neuron dysfunction begins and what causes motor neuron degeneration: whether it is the dying forward process or the dying back phenomenon where motor neuron degeneration begins distally at the nerve terminal or at the neuromuscular junction and progresses toward the cell body, is still a matter of debate. Materials and methods. Are there neuromuscular junction disorders in the early stages of ALS? To answer this, we described 5 patients with ALS presented at Petre Sarajishvili Institute of Neurology in 2018–2022, 3 males and 2 females aged 50–61 years. ALS diagnosis was based on clinical signs, the Gold Coast criteria, electromyography (Awaji), neuroimaging, blood and urine tests. At the early stage of the disease, only asymmetric ptosis and diplopia were noted, which did not improve on pyridostigmine or steroids. Results. We studied patients’ anamnesis, physical data, evaluated their mental, cognitive functions and neurological status. We have also interviewed family members, as it was often difficult for the patient to accurately describe the symptoms. Acetylcholine receptor antibodies were mildly positive only in one patient. Thymoma was excluded. The neurophysiological study showed only marked neuromuscular transmission failure in orbicularis oculi, there were no clinical and electromyographic signs of motor neuron damage. Conclusions. Approximately 2 years later, all five patients developed clinical and electromyographic signs of ALS. In the present study, neuromuscular junction disorders are found to play an important role in the pathogenesis of ALS and may serve as a useful early diagnostic marker.

Biallelic variants in the COQ4 gene caused hereditary spastic paraplegia predominant phenotype.

Hereditary spastic paraplegias (HSPs) comprise a group of neurodegenerative disorders characterized by progressive degeneration of upper motor neurons. Homozygous or compound heterozygous variants in COQ4 have been reported to cause primary CoQ10 deficiency-7 (COQ10D7), which is a mitochondrial disease. We aimed to screened COQ4 variants in a cohort of HSP patients. A total of 87 genetically unidentified HSP index patients and their available family members were recruited. Whole exome sequencing (WES) was performed in all probands. Functional studies were performed to identify the pathogenicity of those uncertain significance variants. In this study, five different COQ4 variants were identified in three Chinese HSP pedigrees and two variants were novel, c.87dupT (p.Arg30*), c.304C>T (p.Arg102Cys). More importantly, we firstly described two early-onset pure HSP caused by COQ4 variants. Functional studies in patient-derived fibroblast lines revealed a reduction cellular CoQ10 levels and the abnormal mitochondrial structure. Our findings revealed that bilateral variants in the COQ4 gene caused HSP predominant phenotype, expanding the phenotypic spectrum of the COQ4-related disorders.

Evolving Diagnostic Criteria in Amyotrophic Lateral Sclerosis and Its Differential Diagnosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by the degeneration of upper motor neurons in the brainstem and spinal cord and lower motor neurons. ALS was first described by Jean-Martin Charcot in 1874 based on clinical features and postmortem examinations. In 1990, the first diagnostic criteria for ALS were developed based on clinical features. Subsequently, three additional diagnostic criteria were published. In this article, we introduce the clinical features, diagnostic criteria, and diseases that need to be differentiated in ALS.

Cortico-muscular coherence in primary lateral sclerosis reveals abnormal cortical engagement during motor function beyond primary motor areas.

Primary lateral sclerosis (PLS) is a slowly progressing disorder, which is characterized primarily by the degeneration of upper motor neurons (UMNs) in the primary motor area (M1). It is not yet clear how the function of sensorimotor networks beyond M1 are affected by PLS. The aim of this study was to use cortico-muscular coherence (CMC) to characterize the oscillatory drives between cortical regions and muscles during a motor task in PLS and to examine the relationship between CMC and the level of clinical impairment. We recorded EEG and EMG from hand muscles in 16 participants with PLS and 18 controls during a pincer-grip task. In PLS, higher CMC was observed over contralateral-M1 (α- and γ-band) and ipsilateral-M1 (β-band) compared with controls. Significant correlations between clinically assessed UMN scores and CMC measures showed that higher clinical impairment was associated with lower CMC over contralateral-M1/frontal areas, higher CMC over parietal area, and both higher and lower CMC (in different bands) over ipsilateral-M1. The results suggest an atypical engagement of both contralateral and ipsilateral M1 during motor activity in PLS, indicating the presence of pathogenic and/or adaptive/compensatory alterations in neural activity. The findings demonstrate the potential of CMC for identifying dysfunction within the sensorimotor networks in PLS.

Extracellular Vesicles as Potential Biomarkers in Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is described as a fatal and rapidly progressive neurodegenerative disorder caused by the degeneration of upper motor neurons in the primary motor cortex and lower motor neurons of the brainstem and spinal cord. Due to ALS's slowly progressive characteristic, which is often accompanied by other neurological comorbidities, its diagnosis remains challenging. Perturbations in vesicle-mediated transport and autophagy as well as cell-autonomous disease initiation in glutamatergic neurons have been revealed in ALS. The use of extracellular vesicles (EVs) may be key in accessing pathologically relevant tissues for ALS, as EVs can cross the blood-brain barrier and be isolated from the blood. The number and content of EVs may provide indications of the disease pathogenesis, its stage, and prognosis. In this review, we collected a recent study aiming at the identification of EVs as a biomarker of ALS with respect to the size, quantity, and content of EVs in the biological fluids of patients compared to controls.

Prolonged central motor conduction time and pyramidal tract degeneration in amyotrophic lateral sclerosis.

Electrophysiological methods to detect the degeneration of the upper motor neuron system have not been fully established in patients with amyotrophic lateral sclerosis (ALS). This may be partly because the parallel demonstration of electrophysiology and a corresponding pathological abnormality is insufficient, and because a substantial number of patients with ALS do not exhibit upper motor neuron degeneration. Recently, we encountered 2 patients with ALS who had been examined for abnormal central motor conduction time (CMCT) using transcranial magnetic stimulation within a 20-day period prior to their death. Autopsy revealed that 1 patient had marked pyramidal degeneration with prolonged CMCT; in contrast, the other patient had no obvious pyramidal degeneration and showed normal CMCT. Both the patients with contrasting clinicopathological differences contributed to the identification that the prolongation of CMCT was possibly linked to the degeneration of the corticospinal tract. This report indicates that CMCT is useful for predicting the severity of upper motor neuron degeneration in patients with ALS.

Functional alterations in large-scale resting-state networks of amyotrophic lateral sclerosis: A multi-site study across Canada and the United States.

Amyotrophic lateral sclerosis (ALS) is a multisystem neurodegenerative disorder characterized by progressive degeneration of upper motor neurons and lower motor neurons, and frontotemporal regions resulting in impaired bulbar, limb, and cognitive function. Magnetic resonance imaging studies have reported cortical and subcortical brain involvement in the pathophysiology of ALS. The present study investigates the functional integrity of resting-state networks (RSNs) and their importance in ALS. Intra- and inter-network resting-state functional connectivity (Rs-FC) was examined using an independent component analysis approach in a large multi-center cohort. A total of 235 subjects (120 ALS patients; 115 healthy controls (HC) were recruited across North America through the Canadian ALS Neuroimaging Consortium (CALSNIC). Intra-network and inter-network Rs-FC was evaluated by the FSL-MELODIC and FSLNets software packages. As compared to HC, ALS patients displayed higher intra-network Rs-FC in the sensorimotor, default mode, right and left fronto-parietal, and orbitofrontal RSNs, and in previously undescribed networks including auditory, dorsal attention, basal ganglia, medial temporal, ventral streams, and cerebellum which negatively correlated with disease severity. Furthermore, ALS patients displayed higher inter-network Rs-FC between the orbitofrontal and basal ganglia RSNs which negatively correlated with cognitive impairment. In summary, in ALS there is an increase in intra- and inter-network functional connectivity of RSNs underpinning both motor and cognitive impairment. Moreover, the large multi-center CALSNIC dataset permitted the exploration of RSNs in unprecedented detail, revealing previously undescribed network involvement in ALS.

Sensitivity of brain MRI and neurological examination for detection of upper motor neurone degeneration in amyotrophic lateral sclerosis

ObjectivesTo investigate sensitivity of brain MRI and neurological examination for detection of upper motor neuron (UMN) degeneration in patients with amyotrophic lateral sclerosis (ALS).MethodsWe studied 192 patients with ALS and...

Upper and Lower Motor Neuron Degenerations Are Somatotopically Related and Temporally Ordered in the Sod1 Mouse Model of Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is a devastating and fatal neurodegenerative disease arising from the combined degeneration of upper motor neurons (UMN) in the motor cortex, and lower motor neurons (LMN) in the brainstem and spinal cord. This dual impairment raises two major questions: (i) are the degenerations of these two neuronal populations somatotopically related? and if yes (ii), where does neurodegeneration start? If studies carried out on ALS patients clearly demonstrated the somatotopic relationship between UMN and LMN degenerations, their temporal relationship remained an unanswered question. In the present study, we took advantage of the well-described Sod1G86R model of ALS to interrogate the somatotopic and temporal relationships between UMN and LMN degenerations in ALS. Using retrograde labelling from the cervical or lumbar spinal cord of Sod1G86R mice and controls to identify UMN, along with electrophysiology and histology to assess LMN degeneration, we applied rigorous sampling, counting, and statistical analyses, and show that UMN and LMN degenerations are somatotopically related and that UMN depletion precedes LMN degeneration. Together, the data indicate that UMN degeneration is a particularly early and thus relevant event in ALS, in accordance with a possible cortical origin of the disease, and emphasize the need to further elucidate the molecular mechanisms behind UMN degeneration, towards new therapeutic avenues.

Improving mitochondria and ER stability helps eliminate upper motor neuron degeneration that occurs due to mSOD1 toxicity and TDP-43 pathology.

BackgroundUpper motor neurons (UMNs) are a key component of motor neuron circuitry. Their degeneration is a hallmark for diseases, such as hereditary spastic paraplegia (HSP), primary lateral sclerosis (PLS), and amyotrophic lateral sclerosis (ALS). Currently there are no preclinical assays investigating cellular responses of UMNs to compound treatment, even for diseases of the UMNs. The basis of UMN vulnerability is not fully understood, and no compound has yet been identified to improve the health of diseased UMNs: two major roadblocks for building effective treatment strategies.MethodsNovel UMN reporter models, in which UMNs that are diseased because of misfolded superoxide dismutase protein (mSOD1) toxicity and TDP‐43 pathology are labeled with eGFP expression, allow direct assessment of UMN response to compound treatment. Electron microscopy reveals very precise aspects of endoplasmic reticulum (ER) and mitochondrial damage. Administration of NU‐9, a compound initially identified based on its ability to reduce mSOD1 toxicity, has profound impact on improving the health and stability of UMNs, as identified by detailed cellular and ultrastructural analyses.ResultsProblems with mitochondria and ER are conserved in diseased UMNs among different species. NU‐9 has drug‐like pharmacokinetic properties. It lacks toxicity and crosses the blood brain barrier. NU‐9 improves the structural integrity of mitochondria and ER, reduces levels of mSOD1, stabilizes degenerating UMN apical dendrites, improves motor behavior measured by the hanging wire test, and eliminates ongoing degeneration of UMNs that become diseased both because of mSOD1 toxicity and TDP‐43 pathology, two distinct and important overarching causes of motor neuron degeneration.ConclusionsMechanism‐focused and cell‐based drug discovery approaches not only addressed key cellular defects responsible for UMN loss, but also identified NU‐9, the first compound to improve the health of diseased UMNs, neurons that degenerate in ALS, HSP, PLS, and ALS/FTLD patients.

The degeneration of upper and lower motor neuron from the perspective of clinical neurological examination and MRI-electromyography manifold detection in amyotrophic lateral sclerosis.

The aim of this study was to explore the upper motor neurons (UMN) and lower motor neurons (LMN) degeneration in amyotrophic lateral sclerosis (ALS) from the perspective of the clinical neurological examination and MRI-electromyography manifold detection, respectively. The clinical data, cortical thickness of corresponding areas in different body regions in MRI and electromyography data were collected from 108 classical ALS patients. The kappa value of UMN and LMN involvement signs in the bulbar region (0.31) was higher than that of the left upper limb (-0.13), right upper limb (-0.27), left lower limb (-0.05) and right lower limb (-0.08). The cortical thickness in the positive LMN damage group was thinner than that of the negative LMN damage group in the left head-face area (P < 0.05; Cohen's d = 0.84); however, cortical thickness showed no significant differences in the right head-face, bilateral tongue-larynx, upper-limb, trunk and lower-limb areas between LMN-damage-positive and LMN-damage-negative groups. The degeneration of motor neuron could be independent through UMN and LMN levels. The degenerative process was not only confined to UMN and LMN levels but can also expand to white matter fiber tracts. Thus, the degeneration of UMN and LMN might be independent of the motor system's three-dimensional anatomy.

Neuropathological profile of long-duration amyotrophic lateral sclerosis in military Veterans.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting both the upper and lower motor neurons. Although ALS typically leads to death within 3 to 5years after initial symptom onset, approximately 10% of patients with ALS live more than 10years after symptom onset. We set out to determine similarities and differences in clinical presentation and neuropathology in persons with ALS with long vs. those with standard duration. Participants were United States military Veterans with a pathologically confirmed diagnosis of ALS (n=179), dichotomized into standard duration (<10years) and long-duration (≥10years). The ALS Functional Rating Scale-Revised (ALSFRS-R) was administered at study entry and semi-annually thereafter until death. Microglial density was determined in a subset of participants. long-duration ALS occurred in 76 participants (42%) with a mean disease duration of 16.3years (min/max=10.1/42.2). Participants with long-duration ALS were younger at disease onset (P=0.002), had a slower initial ALS symptom progression on the ALSFRS-R (P<0.001) and took longer to diagnose (P<0.002) than standard duration ALS. Pathologically, long-duration ALS was associated with less frequent TDP-43 pathology (P<0.001). Upper motor neuron degeneration was similar; however, long-duration ALS participants had less severe lower motor neuron degeneration at death (P<0.001). In addition, the density of microglia was decreased in the corticospinal tract (P=0.017) and spinal cord anterior horn (P=0.009) in long-duration ALS. Notably, many neuropathological markers of ALS were similar between the standard and long-duration groups and there was no difference in the frequency of known ALS genetic mutations. These findings suggest that the lower motor neuron system is relatively spared in long-duration ALS and that pathological progression is likely slowed by as yet unknown genetic and environmental modifiers.

Electrodiagnosis of Amyotrophic Lateral Sclerosis: A Review of Existing Guidelines.

Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of upper motor neurons in the motor cortex and lower motor neurons (LMN) in the brainstem and spinal cord, resulting in a progressive functional impairment. Neurophysiology is a diagnostic tool to detect dysfunction of upper motor neurons and LMN, even when the changes are subclinical. Electromyography is the standard neurophysiological investigation to detect LMN changes, which is essential to exclude mimicking disorders and attain early diagnosis. Recently, Awaji criteria was proposed to support ALS diagnosis, in these criteria fasciculation potentials associated with neurogenic motor unit potentials represents a sufficient marker of LMN involvement, in each muscle. Many studies have confirmed that Awaji criteria are more sensitive, permitting earlier diagnosis without loss of specificity when compared with the revised El Escorial criteria. Fasciculations are easily detected by ultrasound; increasingly, this technique has been used to diagnose ALS, combined with electromyography. This combination can increase diagnostic accuracy. Many techniques for estimating the number of motor units have been proposed, they are useful to quantify LMN loss. Electrical impedance myography is an emerging technique with great potential to monitor ALS progression. Neurophysiological investigation of upper motor neuron dysfunction is difficult in ALS, detecting decreased cortical inhibition by threshold tracking cortical magnetic stimulation is a promising method, which needs to be validated in different centers.

Spreading in ALS: The relative impact of upper and lower motor neuron involvement.

ObjectiveTo investigate disease spread in amyotrophic lateral sclerosis (ALS), and determine the influence of lower (LMN) and upper motor neuron (UMN) involvement.MethodsWe assessed disease spread in ALS in 1376 consecutively studied patients, from five European centers, applying an agreed proforma to assess LMN and UMN signs. We defined the pattern of disease onset and progression from predominant UMN or lower motor neuron (LMN) dysfunction in bulbar, upper limbs, lower limbs, and thoracic regions Non‐linear regression analysis was applied to fit the data to a model that described the relation between two random variables, graphically represented by an inverse exponential curve. We analyzed the probability, rate of spread, and both combined (area under the curve).ResultsWe found that progression was more likely and quicker to or from the region of onset to close spinal regions. When the disease had a limb onset, bulbar motor neurons were more resistant. Furthermore, in the same time frame more patients progressed from bulbar to lower limbs than vice‐versa, whether predominantly UMN or LMN involvement. Patients with initial thoracic involvement had a higher probability for rapid change. The presence of predominant UMN signs was associated with a faster caudal progression.InterpretationContiguous progression was leading pattern, and predominant UMN involvement is important in shortening the time for cranial‐caudal spread. Our results can best be fitted to a model of independent LMN and UMN degeneration, with regional progression of LMN degeneration mostly by contiguity. UMN lesion causes an acceleration of rostral‐caudal LMN loss.

Brain Protease Activated Receptor 1 Pathway: A Therapeutic Target in the Superoxide Dismutase 1 (SOD1) Mouse Model of Amyotrophic Lateral Sclerosis.

Glia cells are involved in upper motor neuron degeneration in amyotrophic lateral sclerosis (ALS). Protease activated receptor 1 (PAR1) pathway is related to brain pathologies. Brain PAR1 is located on peri-synaptic astrocytes, adjacent to pyramidal motor neurons, suggesting possible involvement in ALS. Brain thrombin activity in superoxide dismutase 1 (SOD1) mice was measured using a fluorometric assay, and PAR1 levels by western blot. PAR1 was localized using immunohistochemistry staining. Treatment targeted PAR1 pathway on three levels; thrombin inhibitor TLCK (N-Tosyl-Lys-chloromethylketone), PAR1 antagonist SCH-79797 and the Ras intracellular inhibitor FTS (S-trans-trans-farnesylthiosalicylic acid). Mice were weighed and assessed for motor function and survival. SOD1 brain thrombin activity was increased (p < 0.001) particularly in the posterior frontal lobe (p = 0.027) and hindbrain (p < 0.01). PAR1 levels were decreased (p < 0.001, brain, spinal cord, p < 0.05). PAR1 and glial fibrillary acidic protein (GFAP) staining decreased in the cerebellum and cortex. SOD1 mice lost weight (≥17 weeks, p = 0.047), and showed shorter rotarod time (≥14 weeks, p < 0.01). FTS 40mg/kg significantly improved rotarod scores (p < 0.001). Survival improved with all treatments (p < 0.01 for all treatments). PAR1 antagonism was the most efficient, with a median survival improvement of 10 days (p < 0.0001). Our results support PAR1 pathway involvement in ALS.

Dominant Heterogeneity of Upper and Lower Motor Neuron Degeneration to Motor Manifestation of Involved Region in Amyotrophic Lateral Sclerosis

The aim of this study was to localize the anatomic distribution of upper motor neuron (UMN) loss through examining cortical thickness at the clinical onset of amyotrophic lateral sclerosis (ALS) and explore motor manifestation in functionally impaired body region attribute to impairment of lower motor neuron (LMN) or UMN or mixed LMN and UMN? The clinical features, cortical thickness of corresponding areas from different body regions in MRI and electromyography (EMG) data were collected from 108 classical ALS patients. The cortical thickness was thinner in ALS group than control group in bilateral head-face and upper-limb areas (p < 0.05). In head-face area, the cortical thickness of bulbar-onset group was significantly lower than that of control groups (p < 0.05). In upper-limb areas, the cortical thickness of cervical-onset group was significantly thinner than that of control group. Notably, the bulbar ALSFRS-R subscore was correlated with cortical thickness in bilateral head-face areas (p < 0.05). The bulbar ALSFRS-R subscore of the positive LMN damage group was lower compared to that of the negative LMN damage group (P < 0.001). The limb ALSFRS-R subscore correlated with compound muscle action potential (CMAP) amplitudes of median, ulnar, peroneal, and tibial nerves (P < 0.001), but was not related to cortical thickness. In conclusion, the UMN degeneration in ALS was derived from focal initiation, bulbar- and cervical-onset may date from head-face and upper-limb areas in motor homunculus cortex, respectively. The bulbar dysfunction was resulted from the mixed UMN and LMN impairment, while limb dysfunction derived mostly from LMN loss.

A neuropsychological and behavioral study of PLS

Background: Primary lateral sclerosis (PLS) is a rare motor neuron disease characterized by progressive degeneration of upper motor neurons, resulting in spasticity and disability. There is, however, mounting evidence that the disease is not limited to upper motor neurons alone and that cognitive and behavioral changes within the spectrum of frontotemporal dementia (FTD) are part of the clinical phenotype. Objectives: To provide an in-depth classification of the cognitive and behavioral profiles of PLS by using the golden standard, a full neuropsychological evaluation, as well as a comprehensive behavioral assessment in a cohort of 30 cases. Results: Only 7 out of 30 PLS patients scored within normal range on all of the tests within our battery. The neuropsychological profile of PLS consists of deficits in social cognition (affective theory of mind (ToM) in particular), fluency, executive functions and memory. Using the revised Strong criteria, we could classify 57% of patients within the FTD spectrum (of which 17% had behavioral variant FTD). An additional 20% of patients had deficits which were not characteristic of FTD. Conclusions: This study confirms that PLS is not a restricted phenotype (only affecting upper motor neurons) and that behavioral and cognitive changes are common. Therefore, clinicians treating PLS patients should routinely assess cognition and behavior as part of routine care as cognitive and behavioral changes impact management, decision-making and care-giver burden. This assessment should be sensitive to the neuropsychological profile of PLS (social cognition (affective ToM in particular), fluency, executive functions and memory) and behavioral changes.

Suppression of MAP4K4 Signaling Ameliorates Motor Neuron Degeneration in Amyotrophic Lateral Sclerosis-Molecular Studies Toward New Therapeutics.

Amyotrophic lateral sclerosis (ALS), the most common motor neuron (MN) disease of adults, is characterized by the degeneration of upper MNs in the motor cortex and lower MNs in the brain stem and spinal cord. Our recent work suggests that a MAP kinase family member, MAP4K4 (mitogen-activated protein kinase kinase kinase kinase 4), regulates MN degeneration in ALS. Activation of MAP4K4 occurs prior to MN death and inhibition of MAP4K4 improves neurite integrity and neuronal viability in a cell autonomous manner. The mechanism through which MAP4K4 reduction specifically modulates MN viability can be attributed to the attenuation of the c-Jun apoptotic pathway, as well as to the activation of FoxO1-mediated autophagy that reduces the accumulation of protein aggregates. We additionally show the feasibility of MAP4K4 as a drug target using a MAP4K4-specific inhibitor, which improves the survival of both primary and induced pluripotent stem cell (iPSC)-derived MNs. Our studies are thus far the first to highlight a MAP4K4-initiated signaling cascade that contributes to MN degeneration in ALS, providing a new mechanism underlying MN death in disease and a druggable target for new therapeutics. We propose exciting future directions and unexplored avenues based upon this work.

MRI cortical feature of bulbar impairment in patients with amyotrophic lateral sclerosis.

The decline of voluntary bulbar functions such as speech and swallowing are among the clinical manifestations of amyotrophic lateral sclerosis (ALS) influencing a worst prognosis. Differential diagnosis between the contribution of upper motor neuron (UMN) and lower motor neuron degeneration to the bulbar impairment is often hard. Thinning and T2* hypointensity of the primary motor cortex have been recently suggested as possible MRI markers of UMN impairment in ALS patients, but little research has purposely targeted the orofacial region of the primary motor cortex (fM1). With the aim of finding an MRI marker of UMN impairment responsible for bulbar dysfunction, we investigated the T2* signal intensity of fM1 and the relationship with bulbar impairment in ALS patients. Fifty-five ALS patients were examined with 3 T MRI. Their fM1 was evaluated both qualitatively in terms of T2* signal intensity and quantitatively by measuring its magnetic susceptibility with Quantitative Susceptibility Mapping (QSM). Bulbar functions were assessed clinically, by neurological examination and using the items 1–3 of the ALSFRS-R, and with neurophysiological tests.The marked hypointensity of fM1 was detected in 25% of ALS patients, including all patients with bulbar onset, and was 74% sensitive, 100% specific and 91% accurate in diagnosing functional bulbar impairment. Such hypointensity involved the middle and ventral part of fM1 and was usually visible in both hemispheres. The magnetic susceptibility was significantly higher in patients with marked fM1 hypointensity than in the other patients (p ≤ .001).The relationship with clinical and neurophysiological data suggests that such feature could be a marker of UMN degeneration for voluntary bulbar functions.

New insights into the pathophysiology of fasciculations in amyotrophic lateral sclerosis: An ultrasound study

ObjectiveTo describe the fasciculation pattern in ALS and to analyse its clinical and pathophysiological significance. MethodsUltrasound of 19 muscles was performed in 44 patients with a recent diagnosis (<90 days) of ALS. The number of fasciculations was recorded in each muscle and the muscle thickness and strength were additionally measured in limb muscles. A subgroup of patients were electromyographically assessed. ResultsUS was performed in 835 muscles and EMG was available in 263 muscles. US detected fasciculations more frequently than EMG. Fasciculations were widespread, especially in upper limbs onset patients and in the cervical region. Fasciculations’ number inversely associated with ALSFR-R and body mass index (BMI) and directly with BMI loss and upper motor neuron (UMN) impairment. Our statistical model suggest that fasciculations increase with the initial lower motor neuron (LMN) degeneration, reach their peak when the muscle became mildly to moderately weak, decreasing afterwards with increasing muscle weakness and atrophy. ConclusionsOur study suggests that both UMN and LMN degeneration trigger fasciculations causing BMI loss. The degree of LMN impairment could account for differences in fasciculations’ rates within and between muscles. SignificanceIn ALS, fasciculations could explain the link between hyperexcitability and BMI loss.