Paraspinal and limb motor neuron involvement within homologous spinal segments in ALS

Needle electromyography abnormalities in the upper trapezius muscle in neuromuscular disorders

BACKGROUND

: Needle electromyography (EMG) abnormalities in the trapezius muscle (TM) can be seen in neuromuscular disorders. The aim was to determine the characteristics of needle EMG abnormalities observed in the TM in neuromuscular disorders.

METHODS

The data of patients who applied to the Clinical Neurophysiology Laboratory of University of Health Sciences Adana City Training and Research Hospital between December 2018 and October 2021 were reviewed. Polio survivors, amyotrophic lateral sclerosis (ALS) patients, patients with sensorimotor polyneuropathy, patients with spinal cord lesions involving C2/C3/C4 segments, patients with spinal accessory nerve (SAN) lesions, neuralgic amyotrophy (NA) patients, and patients with myopathy were included. Needle EMG findings of the upper TM of the patients were analyzed. Positive sharp waves, fibrillation potentials, fasciculation potentials, myotonic discharges, and motor unit action potential (MUAP) changes were considered needle EMG abnormalities.

RESULTS

Eighty-one polio survivors, 23 ALS patients, 39 patients with sensorimotor polyneuropathy, 10 patients with cervical spinal lesions, eight NA patients, seven patients with SAN lesions, and three patients with myopathy were included in the study. Fifteen (65.2%) ALS patients, 18 (22.2%) polio survivors, three (30%) patients with cervical spinal lesions, two (5.1%) patients with sensorimotor neuropathy, one (12.5%) NA patient, seven (100%) patients with SAN lesions, and two (66.7%) patients with myopathies had at least one needle EMG abnormality in the TM. Fasciculation potentials in the TM were seen in 10 (43.5%) ALS patients. In four patients with SAN lesions and one polio survivor, MUAP could not be obtained from the TM.

DISCUSSION

There may be more frequent needle EMG abnormalities, particularly in ALS patients and patients with SAN lesions. Since the number of patients with myopathy included in this study was low, it is difficult to comment on the needle EMG features of the TM for these patients. In addition, this study indicated that fasciculation potentials in the TM are typical in ALS patients and that MUAP may not be obtained from the TM in patients with SAN lesions.

Quantitative electromyography: Normative data in paraspinal muscles

BACKGROUND

Quantitative electromyography of paraspinal muscle is a valuable diagnostic tool, but normative data are lacking.

METHODS

Needle electromyography (EMG) was obtained in 65 healthy subjects (49% men, 51% women) aged 21 to 82 years at C7, Th10, and L5 segments bilaterally. The incidence of spontaneous activity; motor unit potential (MUP) amplitudes, durations, and the incidence of polyphasic potentials; and the recruitment pattern at maximal voluntary contraction (MVC) were evaluated.

RESULTS

The incidence of fibrillation potentials was similar to limb muscles. The mean MUP duration and amplitude, and the amplitude at MVC increased caudally, while the incidence of polyphasic potentials was similar at all levels. EMG parameters did not correlate with sex or age.

CONCLUSIONS

In contrast to limb muscles, EMG parameters did not change with age, while polyphasic potentials were more frequent in paraspinal muscle than in limb muscles. The EMG gradient suggests larger motor units at more caudal segments.

Mir-17∼92 Confers Motor Neuron Subtype Differential Resistance to ALS-Associated Degeneration

Progressive degeneration of motor neurons (MNs) is the hallmark of amyotrophic lateral sclerosis (ALS). Limb-innervating lateral motor column MNs (LMC-MNs) seem to be particularly vulnerable and are among the first MNs affected in ALS. Here, we report association of this differential susceptibility with reduced expression of the mir-17∼92 cluster in LMC-MNs prior to disease onset. Reduced mir-17∼92 is accompanied by elevated nuclear PTEN in spinal MNs of presymptomatic SOD1^G93A mice. Selective dysregulation of the mir-17∼92/nuclear PTEN axis in degenerating SOD1^G93A LMC-MNs was confirmed in a double-transgenic embryonic stem cell system and recapitulated in human SOD1^+/L144F-induced pluripotent stem cell (iPSC)-derived MNs. We further show that overexpression of mir-17∼92 significantly rescues human SOD1^+/L144F MNs, and intrathecal delivery of adeno-associated virus (AAV)9-mir-17∼92 improves motor deficits and survival in SOD1^G93A mice. Thus, mir-17∼92 may have value as a prognostic marker of MN degeneration and is a candidate therapeutic target in SOD1-linked ALS. VIDEO ABSTRACT.

Association Between Rectus Abdominis Denervation and Ventilation Dysfunction in Patients with Amyotrophic Lateral Sclerosis

Background:

Spontaneous potentials in electromyography (EMG) of paraspinal muscles are associated with diaphragm denervation and, therefore, poor respiratory function in amyotrophic lateral sclerosis (ALS) is understandable. EMG changes in the rectus abdominis (RA) display an effect similar to those in paraspinal muscles with respect to the function of lower motor neurons in the thoracic spinal cord. The RA denervation was examined to determine its association with ventilation dysfunction in ALS.

Methods:

We collected the clinical data of 128 patients with sporadic ALS in Department of Neurology of Peking University Third Hospital from 2009 to 2013. EMG, Revised ALS Functional Rating Scale (ALSFRS-R) and forced vital capacity (FVC) were performed in all patients and the differences in the EMG changes in RA between those with and without FVC ≥ 80% were analysed.

Results:

The mean FVC value was 83.4% ± 17.1% (range: 45%–131%) of the predicted value. A total of 79 patients displayed FVC ≥80%, and 49 patients displayed FVC <80%. Compared with the patients displaying a normal FVC (60/79, 75.9%), spontaneous activity in RA was significantly different among those patients displaying an FVC <80% (47/49, 95.9%). In addition, spontaneous potentials in RA were more frequently detected in patients exhibiting dyspnea (32/33, 97.0%) than in patients without dyspnea (75/95, 78.9%).

Conclusion:

Spontaneous potentials in RA are associated with ventilation dysfunction and dyspnea in ALS patients.

ALS Patient Stem Cells for Unveiling Disease Signatures of Motoneuron Susceptibility: Perspectives on the Deadly Mitochondria, ER Stress and Calcium Triad

Amyotrophic lateral sclerosis (ALS) is a largely sporadic progressive neurodegenerative disease affecting upper and lower motoneurons (MNs) whose specific etiology is incompletely understood. Mutations in superoxide dismutase-1 (SOD1), TAR DNA-binding protein 43 (TARDBP/TDP-43) and C9orf72, have been identified in subsets of familial and sporadic patients. Key associated molecular and neuropathological features include ubiquitinated TDP-43 inclusions, stress granules, aggregated dipeptide proteins from mutant C9orf72 transcripts, altered mitochondrial ultrastructure, dysregulated calcium homeostasis, oxidative and endoplasmic reticulum (ER) stress, and an unfolded protein response (UPR). Such impairments have been documented in ALS animal models; however, whether these mechanisms are initiating factors or later consequential events leading to MN vulnerability in ALS patients is debatable. Human induced pluripotent stem cells (iPSCs) are a valuable tool that could resolve this “chicken or egg” causality dilemma. Relevant systems for probing pathophysiologically affected cells from large numbers of ALS patients and discovering phenotypic disease signatures of early MN susceptibility are described. Performing unbiased ‘OMICS and high-throughput screening in relevant neural cells from a cohort of ALS patient iPSCs, and rescuing mitochondrial and ER stress impairments, can identify targeted therapeutics for increasing MN longevity in ALS.

Prediction of prognosis of ALS: Importance of active denervation findings of the cervical-upper limb area and trunk area

Amyotrophic lateral sclerosis (ALS) is a motor neuron disease characterized by serious muscle atrophy and weakness. The purpose of this study was to find prognostic factors in patients with mild ALS using application forms for the Specified Disease Treatment Research Program in Japan. We classified ALS as mild, moderate and severe. The subjects consisted of 363 patients with mild ALS who underwent needle electromyography at registration and were followed for more than one year. Time to progression to severe ALS and time to deterioration of activities of daily living such as speech dysfunction, upper limb dysfunction, and walking disability were used as outcomes. Cox proportional hazards model analysis was performed to identify prognostic factors. Of the patients with initially mild ALS, 38.3% (139/363) had progressed severe ALS at the last follow-up. In multivariate analysis of time to progression to severe ALS, bulbar onset (hazard ratio [95% confidence interval]: 1.68 [1.13-2.49], p = 0.010), tongue atrophy (1.69 [1.14-2.51], p = 0.009), dyspnea (1.57 [1.02-2.41], p = 0.042) and active denervation findings (ADFs) of the cervical-upper limb area (1.81 [1.25-2.63], p = 0.002) emerged as prognostic factors. Furthermore ADFs in the trunk area were prognostic factors for upper limb dysfunction and walking disability (1.72 [1.05-2.81], p = 0.031, and 1.97 [1.09-3.59], p = 0.026). In conclusion ADFs of the cervical-upper limb area and trunk area were prognostic factors in ALS patients.

Prognostic models based on patient snapshots and time windows: Predicting disease progression to assisted ventilation in Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a devastating disease and the most common neurodegenerative disorder of young adults. ALS patients present a rapidly progressive motor weakness. This usually leads to death in a few years by respiratory failure. The correct prediction of respiratory insufficiency is thus key for patient management. In this context, we propose an innovative approach for prognostic prediction based on patient snapshots and time windows. We first cluster temporally-related tests to obtain snapshots of the patient's condition at a given time (patient snapshots). Then we use the snapshots to predict the probability of an ALS patient to require assisted ventilation after k days from the time of clinical evaluation (time window). This probability is based on the patient's current condition, evaluated using clinical features, including functional impairment assessments and a complete set of respiratory tests. The prognostic models include three temporal windows allowing to perform short, medium and long term prognosis regarding progression to assisted ventilation. Experimental results show an area under the receiver operating characteristics curve (AUC) in the test set of approximately 79% for time windows of 90, 180 and 365 days. Creating patient snapshots using hierarchical clustering with constraints outperforms the state of the art, and the proposed prognostic model becomes the first non population-based approach for prognostic prediction in ALS. The results are promising and should enhance the current clinical practice, largely supported by non-standardized tests and clinicians' experience.

Spreading of amyotrophic lateral sclerosis lesions--multifocal hits and local propagation?

OBJECTIVE

To investigate whether or not the lesions in sporadic amyotrophic lateral sclerosis (ALS) originate from a single focal onset site and spread contiguously by prion-like cell-to-cell propagation in the rostrocaudal direction along the spinal cord, as has been hypothesised (the 'single seed and simple propagation' hypothesis).

METHODS

Subjects included 36 patients with sporadic ALS and initial symptoms in the bulbar, respiratory or upper limb regions. Abnormal spontaneous activities in needle electromyography (nEMG)-that is, fibrillation potentials, positive sharp waves (Fib/PSWs) or fasciculation potentials (FPs)-were compared among the unilateral muscles innervated by different spinal segments, especially between the T10 and L5 paraspinal muscles, and between the vastus medialis and biceps femoris. Axon length and the proportion of muscle fibre types, which are both related to motoneuronal vulnerability in ALS, are similar in the paired muscles.

RESULTS

Fourteen of 36 patients showed a non-contiguous distribution of nEMG abnormalities from the onset site, with skipping of intermediate segments. In eight of them, the non-contiguous pattern was evident between paired muscles with the same motoneuronal vulnerability. The non-contiguously affected lumbosacral lesions involved motoneuron columns horizontally or radially proximate to one another, appearing to form a cluster in four of the eight patients. FPs, known to precede Fib/PSWs, were shown more frequently than Fib/PSWs in all the lumbosacral segments but L5, suggesting that 2nd hits occur at L5 and then spread to other lumbosacral segments.

CONCLUSIONS

In sporadic ALS, the distribution of lower motoneuron involvement cannot be explained by the 'single seed and simple propagation' hypothesis alone. We propose a 'multifocal hits and local propagation' hypothesis instead.

Can regional spreading of amyotrophic lateral sclerosis motor symptoms be explained by prion-like propagation?

Progressive accumulation of specific misfolded protein is a defining feature of amyotrophic lateral sclerosis (ALS), similarly seen in Alzheimer disease, Parkinson disease, Huntington disease and Creutzfeldt-Jakob disease. The intercellular transfer of inclusions made of tau, α-synuclein and huntingtin has been demonstrated, revealing the existence of mechanisms reminiscent of those by which prions spread through the nervous system. Evidence for such a prion-like propagation mechanism has now spread to the major misfolded proteins, superoxide dismutase 1 (SOD1) and the 43 kDa transactive response DNA binding protein (TDP-43), implicated in ALS. The focus in this review is on what is known about ALS progression in terms of clinical as well as molecular aspects. Furthermore, the concept of 'propagation' is dissected into contiguous and non-contiguous types, and this concept is expanded to the severity of the focal symptom as well as its regional spread which can be explained by cell to cell propagation in the local neuron pool.

Motor neuron diversity in development and disease

Although often considered as a group, spinal motor neurons are highly diverse in terms of their morphology, connectivity, and functional properties and differ significantly in their response to disease. Recent studies of motor neuron diversity have clarified developmental mechanisms and provided novel insights into neurodegeneration in amyotrophic lateral sclerosis (ALS). Motor neurons of different classes and subtypes--fast/slow, alpha/gamma--are grouped together into motor pools, each of which innervates a single skeletal muscle. Distinct mechanisms regulate their development. For example, glial cell line-derived neurotrophic factor (GDNF) has effects that are pool-specific on motor neuron connectivity, column-specific on axonal growth, and subtype-specific on survival. In multiple degenerative contexts including ALS, spinal muscular atrophy (SMA), and aging, fast-fatigable (FF) motor units degenerate early, whereas motor neurons innervating slow muscles and those involved in eye movement and pelvic sphincter control are strikingly preserved. Extrinsic and intrinsic mechanisms that confer resistance represent promising therapeutic targets in these currently incurable diseases.

Does the motor cortex influence denervation in ALS? EMG studies of muscles with both contralateral and bilateral corticospinal innervation

OBJECTIVES

To evaluate the pattern of degeneration of lower motor neuron progression in ALS in relation to the contralateral and ipsilateral corticospinal innervation of the tested muscles.

METHODS

EMG evaluation of the sternomastoid and trapezius muscles on one or both sides, and transcranial magnetic stimulation to record motor evoked responses from these muscles after ipsilateral and contralateral cortical stimulation. The sternomastoid muscle receives corticospinal input from both hemispheres, but the trapezius only a contralateral corticospinal innervation; however the power motor innervation of both these muscles is derived from the same spinal nucleus, and the same motor nerve. Seventy-five patients with ALS were studied at the time of diagnosis, and 54 control subjects, consisting of normal subjects and disease control subjects. MUP analysis and spontaneous activity were assessed.

RESULTS

We confirmed that the sternomastoid receives both contralateral and ipsilateral corticospinal innervation, and the trapezius usually only contralateral innervation. The MUP analysis revealed symmetric changes in sternomastoid and trapezius muscles, and both muscles were equally affected.

CONCLUSIONS

Our findings are in accord with the concept that LMN degeneration in ALS is related to local factors in the spinal cord.

SIGNIFICANCE

Our findings suggest that local factors in the spinal grey matter are important in causing LMN degeneration in ALS, but they do not rule out a corticomotoneuronal contribution.

Association of paraspinal and diaphragm denervation in ALS

Paraspinal EMG needle examination is commonly performed in amyotrophic lateral sclerosis (ALS) for diagnosis. Because lower motor neurons for axial muscles and diaphragm are located medially in the anterior horn, we tested if involvement of axial muscles is associated with diaphragm weakness in ALS. Forty-four ALS patients were included with ALSFRS greater than 20/40. We used needle EMG to search for signs of denervation in biceps, tibialis anterior, C6 and T5 paraspinal muscles, and intercostal and diaphragm muscles. We also evaluated phrenic nerve motor responses and forced vital capacity (FVC). We tested specificity, sensitivity, and discriminative strength (ROC analysis). Fibs-sw in C6 and T5 paraspinal muscles, as well as fibs-sw in diaphragm and intercostal muscles showed high specificity and positive predictive value for FVC<80%. Discriminative strength was good for all the above tests, as well as for phrenic nerve amplitude and ALSFRS regarding FVC<80%. Axial muscles denervation is related to diaphragm denervation and therefore to poor respiratory function in ALS. We suggest that medially located lower motor neurons are affected concurrently in ALS.

[Update on fundamental and clinical research in amyotrophic lateral sclerosis]

This paper from a group of French experts in amyotrophic lateral sclerosis (ALS) presents an update of recent advances in fundamental, epidemiological and clinical research in ALS. Recent development in the pathogenesis of ALS suggests that motor neuron degeneration is a multifactorial and noncell autonomous process. Research has been advanced through the identification of the TAR-DNA-binding protein (TDP-43) as a common neuropathological marker of ALS and frontotemporal lobar degeneration with ubiquitin-positive inclusions. Recently, mutations in the TDP-43 gene have been described in individuals with familial and sporadic ALS. Fundamental research in ALS is expected to lead to the disclosure of new diagnostic markers and therapeutic targets. A small trial has suggested that lithium carbonate may slow ALS progression but larger trials will be needed to confirm these results.

Awaji diagnostic algorithm increases sensitivity of El Escorial criteria for ALS diagnosis

We have tested the sensitivity of a recently published approach to combining clinical and EMG data in the 'research diagnosis' of ALS, in 55 consecutive patients clinically diagnosed with ALS. The application of this 'Awaji algorithm' to the revised El Escorial diagnostic criteria for diagnosis of ALS achieved a diagnostic sensitivity of 95% for definite ALS compared with 18% using the clinical El Escorial criteria and 53% when the EMG criteria as defined in the El Escorial criteria, were applied to the same dataset. This increased sensitivity was particularly relevant for bulbar onset patients (sensitivity improved from 38% to 87%) and for patients with El Escorial clinically possible ALS (from 50% to 86%). We suggest that, in future, investigators and triallists should use the Awaji algorithm superimposed onto the El Escorial criteria, in selecting patients for research studies.