Electrodiagnostic evaluation of myopathies

Anti-HMGCR myopathy mimicking facioscapulohumeral muscular dystrophy

Introduction

Statin use can lead to various muscle-related issues, including benign creatine kinase (CK) elevations, myalgias, toxic myopathies, rhabdomyolysis, and immune-mediated necrotizing myositis (IMNM), which primarily affects older males. IMNM presents with proximal muscle weakness, elevated CK levels, and specific antibodies.

Case presentation

We describe a 72-year-old patient with muscle weakness persisting for over 3 years after statin therapy. Initially suspected to have a genetic disorder, further testing revealed elevated anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) antibodies, indicating immune-mediated myopathy. Despite the absence of inflammatory changes on biopsy, the patient responded positively to immune therapy.

Conclusion

This case highlights challenges in diagnosing immune-mediated myopathy, especially in older patients with atypical presentations. Testing for HMGCR antibodies can aid in diagnosis, particularly when inflammatory markers are absent. Awareness of red flags, such as delayed symptom onset and response to prednisone, is crucial for accurate diagnosis and management.

Advance in the mechanism and clinical research of myalgia in long COVID

As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to evolve, mortality rates of coronavirus disease 2019 (COVID-19) have significantly decreased. However, a variable proportion of patients exhibit persistent prolonged symptoms of COVID-19 infection (long COVID). This virus primarily attacks respiratory system, but numerous individuals complain persistent skeletal muscle pain or worsening pre-existing muscle pain post COVID-19, which severely affects the quality of life and recovery. Currently, there is limited research on the skeletal muscle pain in long COVID. In this brief review, we review potential pathological mechanisms of skeletal muscle pain in long COVID, and summarize the various auxiliary examinations and treatments for skeletal muscle pain in long COVID. We consider abnormal activation of inflammatory response, myopathy, and neurological damages as pivotal pathological mechanisms of skeletal muscle pain in long COVID. A comprehensive examination is significantly important in order to work out effective treatment plans and relieve skeletal muscle pain. So far, rehabilitation interventions for myalgia in long COVID contain but are not limited to drug, nutraceutical therapy, gut microbiome-targeted therapy, interventional therapy and strength training. Our study provides a potential mechanism reference for clinical researches, highlighting the importance of comprehensive approach and management of skeletal muscle pain in long COVID. The relief of skeletal muscle pain will accelerate rehabilitation process, improve activities of daily living and enhance the quality of life, promoting individuals return to society with profound significance.

Immune-Mediated Necrotizing Myopathies: Current Landscape

PURPOSE OF REVIEW

Immune-mediated necrotizing myopathy (IMNM), characterized by acute or subacute onset, severe weakness, and elevated creatine kinase levels, poses diagnostic and therapeutic challenges. This article provides a succinct overview of IMNM, including clinical features, diagnostic strategies, and treatment approaches.

RECENT FINDINGS

Recent insights highlight the different clinical presentations and therapeutic options of IMNM stratified by autoantibody positivity and type. Additionally, recent findings call into question the reported link between statin use and IMNM. This review synthesizes current knowledge on IMNM, emphasizing its distinct clinical features and challenging management. The evolving understanding of IMNM underscores the need for a comprehensive diagnostic approach that utilizes a growing range of modalities. Early and aggressive immunomodulatory therapy remains pivotal. Ongoing research aims to refine diagnostic tools and therapeutic interventions for this challenging muscle disorder, underscoring the importance of advancing our understanding to enhance patient outcomes.

Isotretinoin-induced myositis

Retinoid-induced myositis is a phenomenon recognised in multiple case reports. We report a case of isotretinoin-induced myositis in an 18-year-old male patient. This case adds to the published literature as it demonstrates (i) myositis may occur after extended periods of isotretinoin use, (ii) should be considered as a differential diagnosis even when presenting asymmetrically and (iii) can continue to progress clinically and biochemically initially following the suspension of isotretinoin before being effectively treated with corticosteroids.

Myelin abnormalities in merosin-deficient congenital muscular dystrophy

INTRODUCTION/AIMS

Merosin is a protein complex located in the basement membrane of skeletal muscles and laminin α2-containing regions of the central and peripheral nervous systems. However, because of the prominence of muscle-related symptoms, peripheral neuropathy associated with merosin-deficient congenital muscular dystrophy type 1A (MDC1A) has received little clinical attention. This study aimed to present pathological changes in intramuscular nerves of three patients with MDC1A and discuss their relationship with electrophysiological findings to provide new evidence of peripheral nerve involvement in MDC1A.

METHODS

MDC1A was confirmed by clinical features, muscle biopsy, and genetic testing for variants in LAMA2. To clarify peripheral nerve involvement, we statistically evaluated electrophysiological and muscle pathology findings of intramuscular nerves. These findings were compared with those of age-matched boys with Duchenne muscular dystrophy (DMD) as controls with normal nerves. Nerve conduction studies (NCS) were performed before biopsy. Biopsied intramuscular nerves were examined with electron microscopy using g-ratio, which is the ratio of axon diameter to myelinated fiber diameter.

RESULTS

The myelin sheaths were significantly thinner in MDC1A patients than in age-matched DMD patients, with a mean g-ratio of 0.76 ± 0.07 in MDC1A patients and 0.65 ± 0.14 in DMD patients (p < .0001). No neuropathic changes were identified in muscle pathology. Low compound muscle action potential amplitudes, positive sharp waves and fibrillation potentials, and low-amplitude motor unit potentials with increased polyphasia indicated myopathic changes; no neurogenic changes were seen.

DISCUSSION

We postulate that the thin myelin associated with MDC1A reflects the role of merosin in myelin maturation.

Assessment of Motor Unit Potentials Duration as the Biomarker of DT-DEC01 Cell Therapy Efficacy in Duchenne Muscular Dystrophy Patients up to 12 Months After Systemic-Intraosseous Administration

Duchenne muscular dystrophy (DMD) is a lethal X-linked disease caused by mutations in the dystrophin gene, leading to muscle degeneration and wasting. Electromyography (EMG) is an objective electrophysiological biomarker of muscle fiber function in muscular dystrophies. A novel, DT-DEC01 therapy, consisting of Dystrophin Expressing Chimeric (DEC) cells created by fusing allogeneic myoblasts from normal donors with autologous myoblasts from DMD-affected patients, was assessed for safety and preliminary efficacy in boys of age 6-15 years old (n = 3). Assessments included EMG testing of selected muscles of upper (deltoideus, biceps brachii) and lower (rectus femoris and gastrocnemius) extremities at the screening visit and at 3, 6, and 12 months following systemic-intraosseous administration of a single low dose of DT-DEC01 therapy (Bioethics Committee approval no. 46/2019). No immunosuppression was administered. Safety of DT-DEC01 was confirmed by the lack of therapy-related Adverse Events or Serious Adverse Events up to 22 months following DT-DEC01 administration. EMG of selected muscles of both, ambulatory and non-ambulatory patients confirmed preliminary efficacy of DT-DEC01 therapy by an increase in motor unit potentials (MUP) duration, amplitudes, and polyphasic MUPs at 12 months. This study confirmed EMG as a reliable and objective biomarker of functional assessment in DMD patients after intraosseous administration of the novel DT-DEC01 therapy.

Idiopathic Inflammatory Myopathy with Delayed Finger Opening Resembling Grip Myotonia

Grip myotonia can be a clue for the diagnosis of myotonic disorders. However, several clinical conditions cause delayed finger opening mimicking grip myotonia. We herein report a 44-year-old man with idiopathic inflammatory myopathy who presented with delayed finger opening resembling grip myotonia. The delayed finger opening differed from grip myotonia given the absence of the warm-up phenomenon and percussion myotonia, relative sparing of the thumb extension, and pronounced weakness of the extensor digitorum. Focusing on the extension of the thumb and other fingers may aid in the differentiation between delayed finger opening and true grip myotonia.

[18F]FDG-PET/CT in Idiopathic Inflammatory Myopathies: Retrospective Data from a Belgian Cohort

[¹⁸F]FDG-PET/CT is a useful tool for diagnosis and cancer detection in idiopathic inflammatory myopathies (IIMs), especially polymyositis (PM) and dermatomyositis (DM). Data deriving from Europe are lacking. We describe [¹⁸F]FDG-PET/CT results in a Belgian cohort with IIMs, focusing on patients with PM and DM. All of the cases of IIMs admitted between December 2010 and January 2023 to the Cliniques Universitaires Saint-Luc (Belgium) were retrospectively reviewed. In total, 44 patients were identified with suspected IIMs; among them, 29 were retained for final analysis. The mean age of the retained patients was 48.7 years; 19 patients were female (65.5%). Twenty-two patients had DM and seven had PM. The mean serum creatinine kinase (CK) and the mean CRP levels were 3125 UI/L and 30.3 mg/L, respectively. [¹⁸F]FDG-PET/CT imaging was performed for 27 patients, detecting interstitial lung diseases (ILDs) in 7 patients (25.9%), cancer in 3 patients (11.1%), and abnormal muscle FDG uptake compatible with myositis in 13 patients (48.1%). All of the patients who were detected to have ILDs via PET/CT imaging were confirmed using a low-dose lung CT scan. Among the patients who were detected to have abnormal muscle FDG uptake via PET/CT scans (13/28), the EMG was positive in 12 patients (p = 0.004), while the MRI was positive in 8 patients (p = 0.02). We further observed that there was a significantly higher level of CK in the group with abnormal muscle FDG uptake (p = 0.008). Our study showed that PET/CT is useful for detecting cancer and ILDs. We showed that the detection of abnormal muscle uptake via PET/CT was in accordance with EMG and MRI results, as well as with the mean CK value, and that the presence of dyspnea was significantly associated with the presence of ILDs detected via PET/CT imaging (p = 0.002).

Muscle velocity recovery cycles in myopathy

OBJECTIVE

To understand the pathophysiology of myopathies by using muscle velocity recovery cycles (MVRC) and frequency ramp (RAMP) methodologies.

METHODS

42 patients with quantitative electromyography (qEMG) and biopsy or genetic verified myopathy and 42 healthy controls were examined with qEMG, MVRC and RAMP, all recorded from the anterior tibial muscle.

RESULTS

There were significant differences in the motor unit potential (MUP) duration, the early and late supernormalities of the MVRC and the RAMP latencies in myopathy patients compared to controls (p < 0.05 apart from muscle relatively refractory period (MRRP)). When dividing into subgroups, the above-mentioned changes in MVRC and RAMP parameters were increased for the patients with non-inflammatory myopathy, while there were no significant changes in the group of patients with inflammatory myopathy.

CONCLUSIONS

The MVRC and RAMP parameters can discriminate between healthy controls and myopathy patients, more significantly for non-inflammatory myopathy. MVRC differences with normal MRRP in myopathy differs from other conditions with membrane depolarisation.

SIGNIFICANCE

MVCR and RAMP may have a potential in understanding disease pathophysiology in myopathies. The pathogenesis in non-inflammatory myopathy does not seem to be caused by a depolarisation of the resting membrane potential but rather by the change in sodium channels of the muscle membrane.

Clinical, Genetic, and Histological Characterization of Patients with Rare Neuromuscular and Mitochondrial Diseases Presenting with Different Cardiomyopathy Phenotypes

Cardiomyopathies are mostly determined by genetic mutations affecting either cardiac muscle cell structure or function. Nevertheless, cardiomyopathies may also be part of complex clinical phenotypes in the spectrum of neuromuscular (NMD) or mitochondrial diseases (MD). The aim of this study is to describe the clinical, molecular, and histological characteristics of a consecutive cohort of patients with cardiomyopathy associated with NMDs or MDs referred to a tertiary cardiomyopathy clinic. Consecutive patients with a definitive diagnosis of NMDs and MDs presenting with a cardiomyopathy phenotype were described. Seven patients were identified: two patients with ACAD9 deficiency (Patient 1 carried the c.1240C>T (p.Arg414Cys) homozygous variant in ACAD9; Patient 2 carried the c.1240C>T (p.Arg414Cys) and the c.1646G>A (p.Ar549Gln) variants in ACAD9); two patients with MYH7-related myopathy (Patient 3 carried the c.1325G>A (p.Arg442His) variant in MYH7; Patient 4 carried the c.1357C>T (p.Arg453Cys) variant in MYH7); one patient with desminopathy (Patient 5 carried the c.46C>T (p.Arg16Cys) variant in DES); two patients with mitochondrial myopathy (Patient 6 carried the m.3243A>G variant in MT-TL1; Patient 7 carried the c.253G>A (p.Gly85Arg) and the c.1055C>T (p.Thr352Met) variants in MTO1). All patients underwent a comprehensive cardiovascular and neuromuscular evaluation, including muscle biopsy and genetic testing. This study described the clinical phenotype of rare NMDs and MDs presenting as cardiomyopathies. A multidisciplinary evaluation, combined with genetic testing, plays a main role in the diagnosis of these rare diseases, and provides information about clinical expectations, and guides management.

Myositis Multidisciplinary Clinic in a Tertiary Referral Center

Background

Idiopathic inflammatory myopathies (IIM) are a rare heterogeneous group of diseases characterised by chronic skeletal muscle inflammation, but other organs are also frequently involved. IMM represent a diagnostic challenge and a multidisciplinary approach is important to ensure successful diagnosis and adequate follow-up of these patients.

Objective

To describe the general functioning of our multidisciplinary myositis clinic, highlighting the benefits of multidisciplinary team management in patients with confirmed or suspected IIM and to characterise our clinical experience.

Methods

Description of the organization of a dedicated multidisciplinary myositis outpatient clinic, supported by IMM specific electronic assessment tools and protocols based on our Portuguese Register - Reuma.pt. In addition, an overview of our activity between 2017 and 2022 is provided.

Results

An IIM multidisciplinary care clinic, based on a close collaboration between Rheumatologists, Dermatologists and Physiatrist is detailed in this paper. One hundred and eighty-five patients were assessed in our myositis clinic; 138 (75%) of those were female, with a median age of 58 [45-70] years. At the last appointment, 130 patients had a confirmed IIM diagnosis, and the mean disease duration was 4 [2-6] years. The most frequent diagnosis was dermatomyositis (n = 34, 26.2%), followed by antisynthetase syndrome (n = 27, 20.8%) and clinically amyopathic/paucimyopathic dermatomyositis (n = 18, 13.8%). Twenty-four patients (18.5%) were on monotherapy and 94 (72.3%) were on combination therapy.

Conclusion

A multidisciplinary approach is important to ensure the correct diagnosis and follow-up of these patients. A myositis clinic, with a standardised practice at a tertiary hospital level, contributes to a standardization of care and opens research opportunities.

Pathogenic variants in three families with distal muscle involvement

Three families suspected of distal hereditary motor neuropathy underwent genetic screening with the aim to identify the molecular defect underlying the disease. The description of the identification reflects the shift in molecular diagnostics that was made during the last decades. Our candidate gene approach yielded a known pathogenic variant in BSCL2 (p.Asn88Ser) in one family, and via a CMT-capture, in HSPB1 (p.Arg127Trp), in addition to five other variations in Charcot-Marie-Tooth-related genes in the proband of the second family. In the third family, using whole exome sequencing, followed by linkage-by-location, a three base pair deletion in exon 33 of MYH7 (p.Glu1508del) was found, a reported pathogenic allele albeit for a myopathy. After identification of the causative molecular defect, cardiac examination was performed for patients of the third family and this demonstrated abnormalities in three out of five affected family members. Heterogeneity and expansion of clinical phenotypes beyond known characteristics requires a wider set of genes to be screened. Whole exome/genome analysis with limited prior clinical information may therefore be used to precede a detailed clinical evaluation in cases of large families, preventing screening of a too narrow set of genes, and enabling the identification of novel disease-associated genes. In our cases, the variants had been reported, and co-segregation analysis confirmed the molecular diagnosis.

Challenging Neuromuscular Disease Cases

The diagnosis of neuromuscular disorders requires a thorough history including family history and examination, with the next steps broadened now beyond electromyography and neuropathology to include genetic testing. The challenge in diagnosis can often be putting all the information together. With advances in genetic testing, some diagnoses that adult patients may have received as children deserve a second look and may result in diagnoses better defined or alternative diagnoses made. Clearly defining or redefining a diagnosis can result in understanding of potential other systems involved, prognosis, or potential treatments. This article presents several cases and approach to diagnosis as well as potential treatment and prognostic concerns, including seipinopathy, congenital myasthenic syndrome, central core myopathy, and myotonic dystrophy type 2.

The Limb-Girdle Muscular Dystrophies

PURPOSE OF REVIEW

The limb-girdle muscular dystrophies (LGMDs) are a group of inherited muscle disorders with a common feature of limb-girdle pattern of weakness, caused by over 29 individual genes. This article describes the classification scheme, common subtypes, and the management of individuals with LGMD.

RECENT FINDINGS

Advances in genetic testing and next-generation sequencing panels containing all of the LGMD genes have led to earlier genetic confirmation, but also to more individuals with variants of uncertain significance. The LGMDs include disorders with autosomal recessive inheritance, which are often due to loss-of-function mutations in muscle structural or repair proteins and typically have younger ages of onset and more rapidly progressive presentations, and those with autosomal dominant inheritance, which can have older ages of presentation and chronic progressive disease courses. All cause progressive disability and potential loss of ability to walk or maintain a job due to progressive muscle wasting. Certain mutations are associated with cardiac or respiratory involvement. No disease-altering therapies have been approved by the US Food and Drug Administration (FDA) for LGMDs and standard treatment uses a multidisciplinary clinic model, but recessive LGMDs are potentially amenable to systemic gene replacement therapies, which are already being tested in clinical trials for sarcoglycan and FKRP mutations. The dominant LGMDs may be amenable to RNA-based therapeutic approaches.

SUMMARY

International efforts are underway to better characterize LGMDs, help resolve variants of uncertain significance, provide consistent and improved standards of care, and prepare for future clinical trials.

Post-COVID-19 Myositis Based on Magnetic Resonance Imaging: A Case Report

The severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) causes COVID-19, which is known to cause fever, dry cough, exhaustion, headache, and loss of taste and smell. Although fever, sore throat, and cough have historically been the utmost characteristic symptoms of the illness, published case reports have recently started to emphasize additional uncommon and unusual presentations of infection with the coronavirus. In COVID, the musculoskeletal system is seldomly involved. In addition to reviewing the causes and imaging characteristics of COVID-19-related illnesses of the musculoskeletal system, we elaborate on a case of a middle-aged man who developed myositis as sequelae to the COVID-19 infection.

Glossitis in an older non-corgi dog: Diagnosis and long-term follow-up

A 9-year-old spayed female 18.8 kg mixed breed boxer dog was referred for evaluation of a 7-month history of difficulty swallowing and prehending food, regurgitation, hypersalivation, and an abnormal dorsiflexion of the tongue. Prior to referral, a barium study was performed, which revealed a mildly dilated esophagus. Treatment with sucralfate, cisapride, and prednisone was initiated. Physical examination revealed bilateral, symmetric atrophy of the temporalis muscles, dorsiflexion of the distal aspect of the tongue with concurrent muscle atrophy, and a reduced gag reflex. Electrodiagnostic examinations revealed spontaneous electrical activity in the muscles of mastication and tongue. Biopsies from the right temporalis, tongue, and biceps femoris muscles were collected. An immune-mediated myositis with fibrosis, scattered CD3, CD4, and CD8+ T-lymphocytes, and upregulation of markers for major histocompatibility antigens were observed in the tongue and temporalis muscles. The dog was treated with a tapering course of prednisone over 2 months and cyclosporine long-term. The dog was maintained on cyclosporine alone for > 2 years and clinical signs remained static, although multiple episodes of aspiration pneumonia occurred. Ultimately, euthanasia was performed due to chronic kidney disease with associated anemia, lethargy, and anorexia.

Clinical implication of denervation in sporadic inclusion body myositis

INTRODUCTION

Sporadic inclusion body myositis (sIBM) is often accompanied by signs suggestive of denervation on electromyography (EMG), which mimics neurogenic disorders. Hence, the current study aimed to assess reinnervation after denervation in sIBM and its clinical impllcation.

METHODS

We retrospectively examined consecutive muscle biopsy specimens collected from 109 sIBM patients who were referred to our institution for diagnostic muscle biopsy from 2001 to 2018. Reinnervation after denervation in sIBM patients was assessed via muscle biopsy and EMG. The levels of acetylcholine receptor subunit γ (Chrng) and muscle-specific kinase (MuSK) mRNA, which are markers of denervation, were examined using real-time polymerase chain reaction. Response to treatment was defined as an increase of grade 1 or higher in two or more muscle groups as assessed using the Medical Research Council scale.

RESULTS

In total, 93 (85.3%) of 109 sIBM patients had reinnervation after denervation on histological examination and/or EMG. The mean disease duration before biopsy was significantly longer in patients with reinnervation after denervation than in those without (p < 0.00001). Patients with denervation had significantly higher levels of Chrng and MuSK mRNA than those without. The proportion of patients who responded to immunosuppressive therapies was smaller in the patients with denervation than those without (p < 0.05). However, there was no significant difference regarding time from onset to using a walking aid between the two groups.

DISCUSSION

Reinnervation after denervation is associated with disease duration and short-term response to therapy in individuals with sIBM.

Muscle Biopsy: A Requirement for Precision Medicine in Adult-Onset Myopathy

Muscle biopsy is a fundamental procedure to assist the final diagnosis of myopathy. With the recent advances in molecular diagnosis, serology tests, and mechanism-based classification in myopathy, the précised diagnosis for myopathy required the applications of multiple tools. This study intends to reappraise the benefit of muscle biopsy in adult-onset myopathy under the setting of an optimized muscle biopsy protocol and comprehensive serology tests. A one-group pretest-posttest study design was used. The pre- and post-biopsy diagnoses and treatments in 69 adult patients were compared. Muscle biopsy yielded 85.5% of definitive diagnoses, including changes in pre-biopsy diagnoses (40.6%) and narrowing down the suspicious myopathies (49.3%). The demographic data and clinical parameters between the group “with change” and “without change” after biopsy were not different. Among those with changes in diagnosis, 39.3% also had a corresponding shift in treatment, which benefits the patients significantly. Regarding the most common adult-onset myopathy, idiopathic inflammatory myopathy (IIM), 41% of patients with pre-biopsy diagnosis as IIM had changes in their IIM subtype diagnosis, and 53% was finally not IIM after muscle biopsy. Although there have been advances in molecular diagnosis recently, muscle biopsy still undoubtedly critically guided the diagnosis and treatment of adult-onset myopathy in the era of precision medicine.

Neurotransmission Recovery by Melatonin Measured by CMAP

Compound muscle action potential (CMAP) recordings provide a sensitive electromyographic approach to measure nerve conduction and assess neuromuscular junction functionality in humans and rodents. In humans, it represents a diagnostic tool for neuromuscular disorders. In rodents, this approach is widely employed to dissect the molecular mechanisms driving peripheral nerve degeneration/regeneration, as well as to evaluate the effect of candidate pro-regenerative compounds. The method described here allows recording CMAP from the gastrocnemius muscle of mice after sciatic nerve stimulation. We report some representative traces of CMAP recorded from adult, healthy mice, after sciatic nerve compression and during neurotransmission recovery stimulated by melatonin administration.

Evidence based position paper on Physical and Rehabilitation Medicine practice for people with muscular dystrophies

Muscular dystrophies present a group of inherited degenerative disorder that are characterized by progressive muscular weakness. This evidence-based position paper represents the official position of the European Union through the UEMS PRM Section. The aim of the paper is to evaluate the role of the physical and rehabilitation medicine (PRM) physician and PRM practice for people with muscular dystrophies. A systematic review of the literature and a consensus procedure by means of a Delphi process have been performed involving the delegates of all European countries represented in the UEMS PRM Section. The systematic literature review is reported together with thirty-three recommendations resulting from the Delphi procedure. The role of the PRM physician is to assess the functional status of persons with muscular dystrophy and to plan, monitor and lead PRM program in an interdisciplinary setting within a multiprofessional team.

Clinical features and diagnostic tools in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are rare autoimmune disorders affecting primarily muscles, but other organs can be involved. This review describes the clinical features, diagnosis and treatment for IIMs, namely polymyositis (PM), dermatomyositis (DM), sporadic inclusion body myositis (sIBM), immune-mediated necrotizing myopathy (IMNM), and myositis associated with antisynthetase syndrome (ASS). The diagnostic approach has been updated recently based on the discovery of circulating autoantibodies, which has enhanced the management of patients. Currently, validated classification criteria for IIMs allow clinical studies with well-defined sets of patients but diagnostic criteria to guide the care of individual patients in routine clinical practice are still missing. This review analyzes the clinical manifestations and laboratory findings of IIMs, discusses the efficiency of modern and standard methods employed in their workup, and delineates optimal practice for clinical care. Α multidisciplinary diagnostic approach that combines clinical, neurologic and rheumatologic examination, evaluation of electrophysiologic and morphologic muscle characteristics, and assessment of autoantibody immunoassays has been determined to be the preferred approach for effective management of patients with suspected IIMs.

Development and Preliminary Validation of an Electromyography-Scoring Protocol for the Assessment and Grading of Muscle Involvement in Patients With Juvenile Idiopathic Inflammatory Myopathies

INTRODUCTION

We performed a pilot study in order to investigate the feasibility of an electromyography (EMG)-scoring protocol for the assessment of disease activity in juvenile idiopathic inflammatory myopathies (JIIM).

METHODS

Children with JIIM followed up in a tertiary-level care center underwent standardized clinical, laboratory, and EMG assessment. An EMG-scoring protocol was devised by a consensus panel including a pediatric neurophysiologist and two pediatric rheumatologists, based on a combined score obtained as the sum of (1) the presence of denervation signs (fibrillation potentials) and (2) motor unit remodeling (mixed pattern of short- and long-duration motor unit action potentials). The EMG-scoring protocol was then validated following the Outcome Measures in Rheumatoid Arthritis Clinical Trials filter for outcome measures in rheumatology and the consensus-based standards for the selection of health measurement instruments methodology.

RESULTS

Thirteen children (77% females) were included in the study, with a median age of 10 years (interquartile range: 7-17 years) and median disease duration of 11.8 months (interquartile range: 2.1-44.5). A total of 39 EMG examinations were evaluated. A strong positive association between a standardized tool for muscle strength assessment and the combined score was observed. No significant associations were found with both creatine kinase and erythrocyte sedimentation rate levels.

DISCUSSION

Our EMG-scoring protocol is the first standardized and reproducible tool for the neurophysiologic evaluation and grading of muscle involvement in patients with JIIM and could provide relevant additional information in the assessment and follow-up of these rare conditions.

Electrodiagnostic Assessment of Myopathy

Electrodiagnostic testing is a useful tool in the evaluation of suspected myopathy and helps to confirm the presence of a myopathy and exclude disease mimickers. The electrodiagnostic pattern of findings during testing guides subsequent laboratory evaluation, genetic testing, and in identifying potential muscle biopsy targets. It also provides a baseline for subsequent assessment of disease progression or response to therapy. This article summarizes the approach to electrodiagnostic assessment in various myopathic disorders.

Musculoskeletal involvement of COVID-19: review of imaging

The global pandemic of coronavirus disease 2019 (COVID-19) has revealed a surprising number of extra-pulmonary manifestations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. While myalgia is a common clinical feature of COVID-19, other musculoskeletal manifestations of COVID-19 were infrequently described early during the pandemic. There have been emerging reports, however, of an array of neuromuscular and rheumatologic complications related to COVID-19 infection and disease course including myositis, neuropathy, arthropathy, and soft tissue abnormalities. Multimodality imaging supports diagnosis and evaluation of musculoskeletal disorders in COVID-19 patients. This article aims to provide a first comprehensive summary of musculoskeletal manifestations of COVID-19 with review of imaging.

Subclinical myopathic changes in COVID-19

Introduction

Coronavirus disease 2019 (COVID-19) is associated to neuromuscular symptoms in up to 10.7% of hospitalized patients. Nevertheless, the extent of muscular involvement in infected subjects with no signs of myopathy has never been assessed with neurophysiological investigations.

Methods

Over a 3-week period — from April 30 through May 20, 2020 — a total of 70 patients were hospitalized in the Internal Medicine Ward of the Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico in Milan, Italy. After excluding patients who underwent invasive ventilation and steroid treatment, 12 patients were evaluated. Nerve conduction studies (NCS) included the analysis of conduction velocity, amplitude, and latency for bilateral motor tibial, ulnar nerves, and sensory sural and radial nerves. Unilateral concentric-needle electromyography (EMG) was performed evaluating at least 4 areas of 8 selected muscles. For each muscle, spontaneous activity at rest, morphology, and recruitment of motor unit action potentials (MUAPs) were evaluated.

Results

While nerve conduction studies were unremarkable, needle electromyography showed myopathic changes in 6 out of 12 subjects. All patients were asymptomatic for muscular involvement. Clinical features and laboratory findings did not show relevant differences between patients with and without myopathic changes.

Conclusion

Our data show that in SARS-CoV-2 infection muscular involvement can occur despite the absence of clinical signs or symptoms and should be considered part of the disease spectrum. The application of muscle biopsy to unravel the mechanisms of myofiber damage on tissue specimens could help to clarify the pathogenesis and the treatment response of coronavirus-mediated injury.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10072-021-05469-8.

Guidelines for genetic testing of muscle and neuromuscular junction disorders

Despite recent advances in the understanding of inherited muscle and neuromuscular junction diseases, as well as the advent of a wide range of genetic tests, patients continue to face delays in diagnosis of sometimes treatable disorders. These guidelines outline an approach to genetic testing in such disorders. Initially, a patient's phenotype is evaluated to identify myopathies requiring directed testing, including myotonic dystrophies, facioscapulohumeral muscular dystrophy, oculopharyngeal muscular dystrophy, mitochondrial myopathies, dystrophinopathies, and oculopharyngodistal myopathy. Initial investigation in the remaining patients is generally a comprehensive gene panel by next-generation sequencing. Broad panels have a higher diagnostic yield and can be cost-effective. Due to extensive phenotypic overlap and treatment implications, genes responsible for congenital myasthenic syndromes should be included when evaluating myopathy patients. For patients whose initial genetic testing is negative or inconclusive, phenotypic re-evaluation is warranted, along with consideration of genes and variants not included initially, as well as their acquired mimickers.

In Vivo Fiber Optic Raman Spectroscopy of Muscle in Preclinical Models of Amyotrophic Lateral Sclerosis and Duchenne Muscular Dystrophy

Neuromuscular diseases result in muscle weakness, disability, and, in many instances, death. Preclinical models form the bedrock of research into these disorders, and the development of in vivo and potentially translational biomarkers for the accurate identification of disease is crucial. Spontaneous Raman spectroscopy can provide a rapid, label-free, and highly specific molecular fingerprint of tissue, making it an attractive potential biomarker. In this study, we have developed and tested an in vivo intramuscular fiber optic Raman technique in two mouse models of devastating human neuromuscular diseases, amyotrophic lateral sclerosis, and Duchenne muscular dystrophy (SOD1G93A and mdx, respectively). The method identified diseased and healthy muscle with high classification accuracies (area under the receiver operating characteristic curves (AUROC): 0.76-0.92). In addition, changes in diseased muscle over time were also identified (AUROCs 0.89-0.97). Key spectral changes related to proteins and the loss of α-helix protein structure. Importantly, in vivo recording did not cause functional motor impairment and only a limited, resolving tissue injury was seen on high-resolution magnetic resonance imaging. Lastly, we demonstrate that ex vivo muscle from human patients with these conditions produced similar spectra to those observed in mice. We conclude that spontaneous Raman spectroscopy of muscle shows promise as a translational research tool.

Diagnostic modelling and therapeutic monitoring of immune-mediated necrotizing myopathy: role of electrical myotonia

Delayed diagnosis of immune-mediated necrotizing myopathy leads to increased morbidity. Patients with the chronic course without 3-hydroxy-3-methylglutaryl-coenzyme-A reductase-IgG or signal recognition particle-IgG are often challenging to diagnose. Immunotherapy response can also be difficult to assess. We created a statistical model to assist immune-mediated necrotizing myopathy diagnosis. Electrical myotonia versus fibrillations were reviewed as biomarkers for immunotherapy treatment response. Identified were 119 immune-mediated necrotizing myopathy cases and 938 other myopathy patients. Inclusion criteria included all having electrophysiological evaluations, muscle biopsies showing inflammatory/necrotizing myopathies, comprehensively recorded neurological examinations, and creatine kinase values. Electrical myotonia was recorded in 56% (67/119) of retrospective and 67% (20/30) of our validation immune-mediated necrotizing myopathy cohorts, and significantly (P < 0.001) favoured immune-mediated necrotizing myopathy over other myopathies: sporadic inclusion body myositis (odds ratio = 4.78); dermatomyositis (odds ratio = 10.61); non-specific inflammatory myopathies (odds ratio = 8.46); limb-girdle muscular dystrophies (odds ratio = 5.34) or mitochondrial myopathies (odds ratio = 14.17). Electrical myotonia occurred in immune-mediated necrotizing myopathy seropositive (3-hydroxy-3-methylglutaryl-coenzyme-A reductase-IgG 70%, 37/53; signal recognition particle-IgG 29%, 5/17) and seronegative (51%, 25/49). Multivariate regression analysis of 20 variables identified 8 (including electrical myotonia) in combination accurately predicted immune-mediated necrotizing myopathy (97.1% area-under-curve). The model was validated in a separate cohort of 30 immune-mediated necrotizing myopathy cases. Delayed diagnosis of cases with electrical myotonia occurred in 24% (16/67, mean 8 months; range 0–194). Half (8/19) had a chronic course and were seronegative, with high model prediction (>86%) at the first visit. Inherited myopathies were commonly first suspected in them. Follow-up evaluation in patients with electrical myotonia on immunotherapy was available in 19 (median 21 months, range 2–124) which reduced from 36% (58/162) of muscles to 7% (8/121; P < 0.001). Reduced myotonia correlated with immunotherapy response in 64% (9/14) as well as with median creatine kinase reduction of 1779 U/l (range 401–9238, P < 0.001). Modelling clinical features with electrical myotonia is especially helpful in immune-mediated necrotizing myopathy diagnostic suspicion among chronic indolent and seronegative cases. Electrical myotonia favours immune-mediated necrotizing myopathy diagnosis and can serve as an adjuvant immunotherapy biomarker.

Tetraparesis and sensorimotor axonal polyneuropathy due to co-occurrence of Pompe disease and hereditary ATTR amyloidosis

INTRODUCTION/AIMS

Hereditary transthyretin amyloidosis with polyneuropathy (hATTRPN) is an autosomal dominant multi-organ disorder manifesting in the third to fifth decade with the key clinical features of distal and painful sensory loss of the lower limbs and autonomic dysregulation. Motor neuropathy and cardiomyopathy evolve in the course of the disease. Pompe disease is an autosomal recessive disease leading to decreased levels of lysosomal enzyme acid α-glucosidase and proximal muscle weakness. We report the clinical features and diagnostic workup in the rare case of a patient with ATTR amyloidosis and late-onset Pompe disease, both genetically confirmed.

METHODS

We performed a detailed clinical assessment, exome sequencing, and biochemical measurements.

RESULTS

The patient presented with a distal, painful hypaesthesia of both legs, a cardiomyopathy, and a muscle weakness in the form of a girdle-type pattern of the arms and legs at the beginning and a spreading to distal muscle groups in the course of disease.

DISCUSSION

This study highlights the importance of searching for co-occurrence of rare monogenetic neuromuscular diseases, especially in cases in which all clinical features can be readily explained by a single gene defect.

Neuropathy in sporadic inclusion body myositis: A multi-modality neurophysiological study

OBJECTIVE

Sporadic inclusion body myositis (sIBM) has been associated with neuropathy. This study employs nerve excitability studies to re-examine this association and attempt to understand underlying pathophysiological mechanisms.

METHODS

Twenty patients with sIBM underwent median nerve motor and sensory excitability studies, clinical assessments, conventional nerve conduction testing (NCS) and quantitative thermal threshold studies. These results were compared to established normal controls, or results from a normal cohort of older control individuals.

RESULTS

Seven sIBM patients (35%) demonstrated abnormalities in conventional NCS, with ten patients (50%) demonstrating abnormalities in thermal thresholds. Median nerve motor and sensory excitability differed significantly in sIBM patients when compared to normal controls. None of these neurophysiological markers correlated significantly with clinical markers of sIBM severity.

CONCLUSION

A concurrent neuropathy exists in a significant proportion of sIBM patients, with nerve excitability studies revealing changes possibly consistent with axolemmal depolarization or concurrent neuronal adaptation to myopathy. Neuropathy in sIBM does not correlate with muscle disease severity and may reflect a differing tissue response to a common pathogenic factor.

SIGNIFICANCE

This study affirms the presence of a concurrent neuropathy in a large proportion of sIBM patients that appears independent of the severity of myopathy.

Lipid-lowering Therapies in Myositis

PURPOSE OF REVIEW

The use of lipid-lowering therapies in patients with idiopathic inflammatory myopathies (IIM) is complicated and there are no guidelines for diagnosing, monitoring, or treating atherosclerotic cardiovascular disease (ASCVD) in this group of patients.

RECENT FINDINGS

The use of lipid-lowering therapies, especially statins, is recommended in patients with increased risk for ASCVD, which includes patients with inflammatory diseases, based on recent American College of Cardiology/American Heart Association (ACC/AHA) guidelines for ASCVD management. There is accumulating evidence that patients with IIM are at increased risk for ASCVD, similar to other inflammatory diseases. Lipid-lowering therapies have side effects that may be pronounced or confounding in myositis patients, potentially limiting their use. Statins are specifically contraindicated in patients with anti 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) antibodies. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have been shown to be safe and potentially beneficial in patients with IIM. Here, we propose a framework for (1) ASCVD risk assessment and treatment based on ACC/AHA ASCVD primary prevention guidelines; (2) myositis disease monitoring while undergoing lipid-lowering therapy; and (3) management of statin intolerance, including, indications for the use of PCSK9 inhibitors.

Mice carrying an analogous heterozygous dynamin 2 K562E mutation that causes neuropathy in humans develop predominant characteristics of a primary myopathy

Some mutations affecting dynamin 2 (DNM2) can cause dominantly inherited Charcot-Marie-Tooth (CMT) neuropathy. Here, we describe the analysis of mice carrying the DNM2 K562E mutation which has been associated with dominant-intermediate CMT type B (CMTDIB). Contrary to our expectations, heterozygous DNM2 K562E mutant mice did not develop definitive signs of an axonal or demyelinating neuropathy. Rather, we found a primary myopathy-like phenotype in these mice. A likely interpretation of these results is that the lack of a neuropathy in this mouse model has allowed the unmasking of a primary myopathy due to the DNM2 K562E mutation which might be overshadowed by the neuropathy in humans. Consequently, we hypothesize that a primary myopathy may also contribute to the disease mechanism in some CMTDIB patients. We propose that these findings should be considered in the evaluation of patients, the determination of the underlying disease processes and the development of tailored potential treatment strategies.

Changes in motor unit bioelectrical activity recorded at two different sites in a muscle

INTRODUCTION

The objective of this study was to compare the properties of bioelectrical signals of motor units recorded at different sites in the muscles of controls, patients with myopathy and patients with motor neuron disease (MND).

METHODS

Five controls, 10 patients with myopathy and 11 patients with MND were included. Electrophysiologic tests were performed in the biceps brachii (BB) muscle from two recording sites. Site 1 was near the belly of the muscle and Site 2 was 5cm distal from Site 1, near the tendon. Multi-motor unit potential (MUP) analysis, jitter analysis, and peak number count were calculated from the signals recorded using a concentric needle electrode (CN).

RESULTS

At Site 2, duration was longer, number of phases was higher and amplitudes were smaller in MUPs compared with those recorded at Site 1. This significant difference between recording site and patient groups was related to neurogenic muscles. Jitter analysis showed no significant difference except an intergroup difference between the patient groups and controls. The peak number calculated using the CN was greater when recorded from Site 1 in concordance with MUP analysis.

CONCLUSION

Duration of MUP was longer and amplitude was smaller when the recording electrode was placed distally along the muscle near the tendon in neurogenic muscles, probably related to increased temporal dispersion. However, changing the position of the needle did not provide further information in distinguishing myogenic muscles.

Muscle involvement in myasthenia gravis: Expanding the clinical spectrum of Myasthenia-Myositis association from a large cohort of patients

Myastenia-Inflammatory Myopathy (MG-IM) association has been described in less than 50 cases, as isolated reports or in few case series. In most cases, MG and IM onset occur simultaneously even if the overlapping clinical manifestations could lead to delay the diagnosis in the early stage of disease. In these cases, thymic pathology is present in more than 50% of cases. Pathological findings can be consistent of polymyositis (63%), dermatomyositis (25%) or granulomatosis (12%). Accurate clinical manifestations and severity of IM in MG, including muscle specific antibodies (MSA) and muscle MRI, have not been systematically investigated and focal or mild subclinical myositis have not been reported. We observed that focal myositis or asymptomatic CK elevation can also occur in MG. In this review we have also retrospectively re-analyzed the clinical, serological, pathological and muscle imaging data from 13 patients with MG- IM from our cohort of 441 MG patients (2,9%). Clinical onset occurred simultaneously in 10/13 patients, whereas in 2 patients the IM appeared later in MG disease course (range 10-14 years) and conversely in 1 patient MG symptoms occurred later in IM disease course (4 years). Median age at disease onset was 51 year (range 24-73 years) regardless of clinical onset (MG or IM). Median clinical follow-up was 88 months (range 31-237 months). IM was suspected by CK elevation in all patients (ranging 800-3000 UI/L at first detection) and non-fatigable muscle weakness unresponsive to acetylcholinesterase inhibitors. All the patients presented mild to moderate MG symptoms. Three main categories of muscle involvement, sometimes overlapping, were recognizable: distal, proximal and subclinical myositits, leading to three main clinical groups (A,B,C) and two overlapping subgroups (A/B and B/C). Thymus pathology was present in 10/13 patients. Anti-AChR was detected in al all patients associated with anti-Titin and -RyR1 in those patients with thymoma. No MSA, nor MAA antibodies were detected. Muscle biopsy confirmed IM in all patients. In conclusion we redefined the clinical spectrum of muscle involvement in MG-IM association, which represent a continuum among 3 main clinical groups: distal, proximal and subclinical muscle involvement. Minimal muscle involvement and focal myositis could be underestimated among myasthenic patients and early aggressive immunotherapy could be required in focal group.

A novel de novo variant of LAMA2 contributes to merosin deficient congenital muscular dystrophy type 1A: Case report

Merosin deficient congenital muscular dystrophy type 1A (MDC1A) is caused by defects in the LAMA2 gene. Patients with MDC1A exhibit severe symptoms, including congenital hypotonia, delayed motor development and contractures. The present case report describes a Vietnamese male child with clinical manifestations of delayed motor development, limb-girdle muscular dystrophy, severe scoliosis and white matter abnormality in the brain. Whole exome sequencing (WES) was performed with subsequent validation using Sanger sequencing, and a de novo missense variant (NM_000426.3:c.1964T>C, p.Leu655Pro) and a splice site variant (NG_008678.1:c.3556-13T>A) in the LAMA2 gene of the proband was detected. The missense variant located in exon 14 and has not been reported previously, to the best of our knowledge; whereas the splice site variant has been previously reported to cause premature termination of transcription in patients with MDC1A. In silico tools predicted that the missense variant was damaging. Phenotype-genotype analysis suggested that this proband was associated with classical early onset MDC1A. The co-existence of a de novo and a heterozygous variant in the LAMA2 gene suggested that the de novo variant contributed to the autosomal recessive manner of the disease. Careful consideration of this event by clinical confirmation of parental carrier status may help to accurately determine the risk of occurrence of this disease in future offspring. Additionally, WES is recommended as a powerful tool to assist in identifying potentially causative variants for heterogeneous diseases such as MDC1A.

Muscle Toxicity of Drugs: When Drugs Turn Physiology into Pathophysiology

Drugs are prescribed to manage or prevent symptoms and diseases, but may sometimes cause unexpected toxicity to muscles. The symptomatology and clinical manifestations of the myotoxic reaction can vary significantly between drugs and between patients on the same drug. This poses a challenge on how to recognize and prevent the occurrence of drug-induced muscle toxicity. The key to appropriate management of myotoxicity is prompt recognition that symptoms of patients may be drug related and to be aware that inter-individual differences in susceptibility to drug-induced toxicity exist. The most prevalent and well-documented drug class with unintended myotoxicity are the statins, but even today new classes of drugs with unintended myotoxicity are being discovered. This review will start off by explaining the principles of drug-induced myotoxicity and the different terminologies used to distinguish between grades of toxicity. The main part of the review will focus on the most important pathogenic mechanisms by which drugs can cause muscle toxicity, which will be exemplified by drugs with high risk of muscle toxicity. This will be done by providing information on key clinical and laboratory aspects, muscle electromyography patterns and biopsy results, and pathological mechanism and management for a specific drug from each pathogenic classification. In addition, rather new classes of drugs with unintended myotoxicity will be highlighted. Furthermore, we will explain why it is so difficult to diagnose drug-induced myotoxicity, and which tests can be used as a diagnostic aid. Lastly, a brief description will be given of how to manage and treat drug-induced myotoxicity.

The motor unit and quantitative electromyography

Electromyography (EMG) assesses the anatomic motor unit (A-MU), but knowledge of its anatomy, physiology, and changes with pathology is limited. The electrophysiological motor unit (E-MU) and its motor unit potential (E-MUP) represents a fraction of the A-MU. Routine EMG assesses a limited number of E-MUP waveform characteristics (metrics) and their magnitudes qualitatively scaled in a nonlinear manner. Another approach is quantitative EMG (QEMG), whereby 20⁺ E-MUPs are extracted and both basic and derived metrics obtained and values expressed quantitatively. In diseased muscle, many E-MUP metrics may be normal, which complicates diagnostic interpretation. In QEMG, E-MUP metrics can be clustered and statistical analyses performed to assign probabilities that E-MUPs (and the muscle) are normal, neuropathic, or myopathic. In this article we review what is known about the A-MU, the restricted E-MU, E-MUP metrics, and what QEMG offers currently and in the future.

Late-onset Pompe disease associated with polyneuropathy

Late-onset Pompe disease is caused by a glycogen deposition involving mainly striated muscle. It may also target many other tissues such as liver, smooth muscles or spine anterior horn. Glycogen accumulation in Schwann cells and in the perineurium of peripheral nerves was shown in Pompe's disease mouse models. Moreover two late-onset Pompe disease patients were reported as having a small fiber neuropathy. To the best of our knowledge an involvement of large nerve fibers was never depicted. We describe four late-onset Pompe disease patients having a concomitant polyneuropathy of undetermined etiology. Our observations reinforce the proof-of-concept supporting a potential involvement of peripheral nerves as additional organ targeted by late-onset Pompe disease. It has clinical care consequences since peripheral neuropathy in late-onset Pompe disease could worsen patient's disability and needs particular care such as proprioceptive physiotherapy.

Classification and management of adult inflammatory myopathies

Inflammatory myopathies, collectively known as myositis, are heterogeneous disorders characterised by muscle inflammation, and frequently accompanied by extramuscular manifestations that affect the skin, lung, and joints. Patients with inflammatory myopathies were previously classified as having dermatomyositis if characteristic rashes accompanied the muscle involvement, and as having polymyositis if no rashes were present. Five main types of inflammatory myopathies are now widely recognised: dermatomyositis, immune-mediated necrotising myopathy, sporadic inclusion-body myositis, overlap myositis (including antisynthetase syndrome), and polymyositis. The discovery of autoantibodies that are specifically associated with characteristic clinical phenotypes has been instrumental to the understanding of inflammatory myopathies. Treatment is still largely based on expert opinion, but several studies have shown effectiveness of different therapies in various subsets of inflammatory myopathies. These advances will undoubtedly improve the outcomes of patients with inflammatory myopathies.

Intensive Care Management of the Neuromuscular Patient

Neuromuscular emergencies are a distinct group of acute neurological diseases with distinct characteristic presentations. Patients who suffer from this group of diseases are at immediate risk of losing protection of their native airway as well as aspirating orogastric contents. This is secondary to weakness of the muscles of the oropharynx and respiratory muscles. Although some neuromuscular emergencies such as myasthenia gravis or Guillain-Barré syndrome are well understood, others such as critical illness myopathy and neuropathy are less well characterized. In this chapter, we have discussed the pathophysiology, diagnostic evaluation, and management options in patients who are admitted to the intensive care unit. We have also emphasized the importance of a thorough understanding of the use of pharmacological anesthetic agents in this patient population.

Needle electromyography and histopathologic correlation in myopathies

INTRODUCTION

Needle electromyography (EMG) findings help confirm myopathy and may indicate specific pathologic changes on muscle biopsy.

METHODS

We conducted a retrospective chart review of 218 consecutive patients referred for muscle biopsy. Presence of specific needle EMG findings was correlated with pathologic findings of inflammation, necrosis, splitting, and vacuolar changes. Sensitivity, specificity, and positive and negative predictive values of specific EMG findings for pathologic changes were calculated.

RESULTS

Short-duration motor unit potentials (MUP) were sensitive (83%-94%) but not specific (34%-49%) for pathologic changes. Fibrillation potentials were 65%-74% sensitive and 58%-81% specific for inflammation, necrosis, splitting, or vacuolar changes. The absence of fibrillation potentials had high negative predictive value (82%-93%) for inflammation, splitting, or vacuolar changes.

DISCUSSION

Fibrillation potentials and short-duration MUPs predict pathologic changes of muscle fiber necrosis, splitting, and/or vacuolar changes (as seen with inflammatory myopathies and muscular dystrophies). Absence of fibrillation potentials suggests other myopathologic changes (e.g., congenital myopathy). Muscle Nerve 59:315-320, 2019.

Recording characteristics of electrical impedance-electromyography needle electrodes

OBJECTIVE

Needle EMG remains the standard clinical test for neuromuscular disease (NMD) assessment, but it only characterizes myofiber membrane depolarization. On the other hand, electrical impedance provides non-electrically active structural and compositional data of tissues. Here, we designed a prototype of needle electrode integrating electrical impedance and EMG measurement capabilities, the so-called I-EMG needle electrode.

APPROACH

We use finite element method models to study the impedance recording characteristics of I-EMG needle electrodes. The simulated electrical and mechanical design specifications are then manufactured to create a prototype of an I-EMG needle electrode. We pilot these new needle electrodes by conducting in vivo impedance measurements with muscle at rest on healthy wild-type (wt, n  =  5) and muscular dystrophy (mdx, n  =  5) mice. Comparisons between wt and mdx mice are performed using Mann-Whitney test, two-tailed, p  <  0.05. The electrical characterization of the EMG electrode in the developed I-EMG needles was performed in vitro on saline solution and through EMG detection in wt animal at rest and during voluntary contractions.

RESULTS

Muscle impedance demonstrate good repeatability (p  <  0.05 and p  <  0.005 for resistance and reactance at 50 kHz, respectively) and agreement between different I-EMG needles. Impedance data allows us to discriminate between mdx and wt muscle (p  <  0.05 and p  <  0.005 for resistance and reactance at 10 kHz, respectively). EMG broadband noise power and peak amplitude using the I-EMG needle were similar to that of a commercial monopolar EMG needle. EMG recordings using the I-EMG needle measured electrical activity similar to a standard monopolar needle with muscle at rest and during voluntary contraction.

SIGNIFICANCE

Needle I-EMG technology may offer the opportunity to enhance the diagnostic capability and quantification of NMD beyond that possible with either impedance or EMG techniques separately. Ultimately, needle I-EMG could serve as a new bedside tool to assess NMD without increasing the complexity or duration of the EMG test.

Rehabilitation in Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease is a potentially debilitating complication of allogeneic hematopoietic stem cell transplantation. Due to the direct inflammatory effects of the disease on tissue, and the impact on muscle and bone of the high-dose glucocorticoid immunosuppression used to treat the disease, patients are at risk of developing multifactorial functional impairment. This review outlines the clinical assessment and rehabilitation interventions to manage aspects of the disease that cause the most impairment: involvement of the skin/fascial and cardiopulmonary organ systems, as well as steroid-induced myopathy and bone and joint destruction.

Associations between apparent diffusion coefficient and electromyography parameters in myositis-A preliminary study

OBJECTIVE

MRI is widely used in several muscle disorders. Diffusion-weighted imaging (DWI) is an emergent imaging modality sensitive to microstructural alterations in tissue. The apparent diffusion coefficient (ADC) is used to quantify the random motion of water molecules. Electromyography (EMG) is a clinically used diagnostic tool in myositis. The aim of this study was to elucidate possible associations between ADC values and EMG findings in myositis patients.

METHOD

Seven patients (eight investigated muscles) with myositis (mean age 51.43 ± 19 years) were included in this study. The diagnosis was confirmed by histopathology in every case. DWI was obtained with a 1.5-T scanner using two b-values 0 and 1000 s/mm². In all patients, a needle electromyography (EMG) was performed within 3 days to the MRI. The following EMG parameters were studied: motor unit action potential (MUAP) amplitudes and durations, as well as pathological spontaneous activity. Spearman's correlation coefficient was used to analyze associations between investigated parameters.

RESULTS

The estimated mean ADC _mean value was 1.51 ± 0.29 × 10^-3 mm²/s, mean ADC _min was 1.28 ± 0.27 × 10^-3 mm²/s, and mean ADC _max was 1.73 ± 0.28 × 10^-3 mm²/s. Correlation analysis identified significant associations between ADC _mean and duration of the MUAP (p = .78 P = .0279) and between ADC _min and duration of the MUAP (p = .85, P = .01). There were no significant differences according to pathological spontaneous activity.

CONCLUSION

ADC _mean and ADC _min showed strong positive correlations with the duration of the MUAP in myositis patients. Both modalities might similarly reflect muscle fiber loss in myositis patients.