Muscle Muscle Magnetic Resonance Imaging Research Articles

Pre- and post-skeletal muscle biopsy quantitative magnetic resonance imaging reveals correlations with histopathological findings.

Quantitative muscle magnetic resonance imaging (MRI) is a promising non-invasive method in the diagnostic workup as well as follow-up of neuromuscular disorders. The aim of this study was to correlate quantitative MRI (qMRI) parameters to histopathological changes in skeletal muscle tissue and thus to verify the data from our pilot study. Twenty-six patients (eight females, 46.4 ± 15.1 years) were examined within 72 h before and within 24 h after a skeletal muscle biopsy using quantitative muscle MRI. Post-biopsy MRI was employed to pinpoint the exact localization of the biopsy. qMRI parameters including fat fraction, water T2 relaxation time and diffusion metrics including fractional anisotropy, mean diffusivity, axial diffusivity and radial diffusivity were extracted from the localization of the biopsy and correlated with histopathological findings. Additionally, three different segmentation masks were applied to the qMRI dataset, to evaluate whether the whole muscle represents the exact biopsy location. Fat fraction and water T2 relaxation time in qMRI correlated significantly with the fat fraction in the muscle biopsy and histopathological inflammatory markers. Fractional anisotropy correlated with the quantity of type 2 fibres, whilst mean diffusivity correlated with p62. No differences were found using different segmentation masks in qMRI. In this follow-up study, the results from our previous study were verified regarding the correlation of qMRI parameters with histopathological features in muscle biopsies, indicating that qMRI serves as a suitable non-invasive method in the follow-up of patients with neuromuscular disorders. If post-biopsy MRI is not available, whole muscle volume can be used for histopathological correlations.

Current approach to muscle imaging in myositis.

Muscle imaging is commonly utilized in idiopathic inflammatory myopathies (IIM) for diagnostic evaluation, selection of muscle biopsy site, and differentiating between disease activity versus damage. In this review, we discuss the current state and recent developments in the use of muscle imaging modalities including muscle magnetic resonance imaging (MRI), ultrasound (US), and positron emission tomography (PET) scan. Muscle MRI is a clinically useful tool in evaluation of IIM with studies showing good correlations between pattern of morphological changes on MRI and histopathological findings on muscle biopsy. The use of computer aided diagnostics to enable quantification of muscle pathology will be a welcome development for future studies and trials. New studies highlight that muscle US could be a particularly useful point of care tool in longitudinal monitoring of patients with active myositis. Muscle FDG-PET scan shows inflammatory activity in IIM muscle and can also provide additional information on extra-muscular manifestations and cancer screening. Utilization of novel tracers is an exciting development for IIM evaluation. Muscle MRI remains the gold standard for muscle imaging in IIM. Growing literature on muscle US and PET scan highlight their promising applications in IIM.

Whole-body muscle magnetic resonance imaging in inflammatory myopathy with mitochondrial pathology.

Inflammatory myopathy with mitochondrial pathology (IM-Mito) is a rare condition described in a few case series, and it is not clear whether it is a specific disease or a variant of Inclusion Body Myositis (IBM). Radiological data of IM-Mito patients has only been evaluated in one study. To analyze whole-body muscle magnetic resonance imaging (MRI) features in patients with IM-Mito compared with individuals with IBM. Fourteen IM-Mito and ten IBM patients were included. IM-Mito was defined by endomysial inflammatory infiltrate, presence of at least 1% of Cytochrome C Oxidase negative fibers, and absence of rimmed vacuoles in muscle biopsy; and IBM was defined by the presence of dystrophic muscular abnormalities, endomysial inflammatory infiltrate, and rimmed vacuoles. Patients underwent clinical evaluation and whole-body muscle MRI to determine the presence of edema, and fatty infiltration in various muscles. Muscle imaging abnormalities were asymmetric in most patients with IM-Mito and IBM. Muscles with the highest average degree of fatty infiltration in both conditions were the quadriceps and medial gastrocnemius. Most patients with IM-Mito and IBM showed imaging patterns of rectus femoris relatively spared compared to other quadriceps muscles. The flexor digitorum profundus was the most affected muscle of the upper limbs in both IBM and IM-Mito. Although the results suggest some similarities in muscle imaging features between IM-Mito and IBM, there remains uncertainty whether these two conditions are part of the same clinical spectrum.

Characterization of Phenotypic Variability in Becker Muscular Dystrophy for Clinical Practice and Towards Trial Readiness: A Two-Years Follow up Study.

Becker muscular dystrophy (BMD) is a dystrophinopathy due to in-frame mutations in the dystrophin gene (DMD) which determines a reduction of dystrophin at muscle level. BMD has a wide spectrum of clinical variability with different degrees of disability. Studies of natural history are needed also in view of up-coming clinical trials. From an initial cohort of 32 BMD adult subjects, we present a detailed phenotypic characterization of 28 patients, then providing a description of their clinical natural history over the course of 12 months for 18 and 24 months for 13 of them. Each patient has been genetically characterized. Baseline, and 1-year and 2 years assessments included North Star Ambulatory Assessment (NSAA), timed function tests (time to climb and descend four stairs), 6-minute walk test (6MWT), Walton and Gardner-Medwin Scale and Medical Research Council (MRC) scale. Muscle magnetic resonance imaging (MRI) was acquired at baseline and in a subgroup of 9 patients after 24 months. Data on cardiac function (electrocardiogram, echocardiogram, and cardiac MRI) were also collected. Among the clinical heterogeneity, a more severe involvement is often observed in patients with 45-X del, with a disease progression over two years. The 6MWT appears sensitive to detect modification from baseline during follow up while no variation was observed by MRC testing. Muscle MRI of the lower limbs correlates with clinical parameters.Our study further highlights how the phenotypic variability of BMD adult patients makes it difficult to describe an uniform course and substantiates the need to identify predictive parameters and biomarkers to stratify patients.

Comparison of characteristics of muscle magnetic resonance imaging findings in patients with antineutrophilic cytoplasmic antibody-associated vasculitis and polyarteritis nodosa.

This study aimed to analyze the muscle magnetic resonance imaging (MRI) findings of patients with antineutrophilic cytoplasmic antibody-associated vasculitis (AAV) and polyarteritis nodosa (PAN) presenting with clinical symptoms in the extremities. Retrospective analysis was conducted on short tau inversion recovery MRI findings, with a focus on intramuscular vessels displaying abnormal perivascular signals, in 22 and eight patients with AAV and PAN, respectively. The number per unit area (4 cm2) and diameter of abnormal vessels on muscle MRI were compared between patients with AAV and those with PAN. Cut-off values, clinical sensitivity, and specificity for these indices were calculated from the receiver operating characteristic curves to distinguish between AAV and PAN, and the relationship between the indices and clinical findings in AAV was analyzed. The number of abnormal vessels per unit area was significantly higher in AAV compared to PAN (p < .05). Additionally, the diameter of the abnormal vessels was significantly higher in PAN than in AAV (p < .05). The presence of >6.44 abnormal vessels per unit area or ≤3.61 mm diameter of abnormal vessels was able to predict AAV (sensitivity, 0.955; specificity, 0.625). AAV patients with peripheral neuropathy exhibited a significantly higher number of abnormal vessels per unit area than those without peripheral neuropathy (p < .05). Muscle MRI can detect small- to medium-vessel vasculitis and be a valuable tool for distinguishing between patients with AAV and PAN experiencing clinical symptoms in the extremities.

Magnetic Resonance Imaging Patterns Revealing Muscle Pathology and Clinical Features in Idiopathic Inflammatory Myopathies.

Idiopathic inflammatory myopathies (IIMs) are autoimmune disorders significantly impacting skeletal muscles; however, the precise correlation between muscle magnetic resonance imaging (MRI) findings, muscle pathology, disease subtypes, and clinical characteristics remains uncertain. Thus, we investigated the association of muscle MRI findings in IIMs with muscle pathology and clinical features. New-onset IIM patients underwent proximal upper and/or lower limb muscle MRI. Patterns of muscle oedema on MRI were categorised into fascial, honeycomb, peripheral, foggy, dense, or coarse dot patterns and compared with inflammatory cell infiltration sites in corresponding muscle biopsies. The incidence of MRI patterns was examined in patient subgroups using myositis-specific antibodies (MSAs) and 2017 EULAR/ACR classification criteria. Univariate and multivariate analyses were conducted to determine the odds ratios (ORs) of MRI findings for clinical characteristics. Fifty-six of 85 patients underwent muscle biopsy. Foggy, honeycomb, and fascial patterns at biopsy sites correlated with inflammatory cell infiltration in the endomysium (OR 11.9, p= 0.005), perimysium (OR 6.0, p= 0.014), and fascia (OR 16.9, p< 0.001), respectively. Honeycomb and foggy patterns were characteristic of patients with anti-TIF1γ or anti-Mi2 antibodies and MSA-negative dermatomyositis, and those with anti-SRP or anti-HMGCR antibodies and MSA-negative polymyositis (PM), respectively. The honeycomb pattern positively correlated with malignancy (OR 6.87, p< 0.001) and Gottron sign (OR 8.05, p= 0.002); the foggy pattern correlated with muscle weakness (OR 11.24, p= 0.005). The dense dot pattern was associated with dysphagia (OR 6.27, p= 0.006) and malignancy (OR 8.49, p= 0.002). Muscle MRI holds promise in predicting muscle pathology, disease subtypes, and clinical manifestations of IIMs.

Clinical and genetic analysis of a patient with Desminopathy manifesting initially with myalgia after lower limb activity

To explore the clinical characteristics and genetic variant of a patient with desminopathy manifesting with atypical symptoms. A patient who was admitted to the Department of Neurology of Jing'an District Central Hospital on February 24, 2021 was selected as the study subject. Clinical data, laboratory tests, muscle pathology, muscle magnetic resonance imaging (MRI) and genetic testing of the patient were retrospectively analyzed. The patient had developed myalgia after lower limb activity, and gradually developed asymmetrical muscle weakness and atrophy of the lower limbs. Cardiac examination revealed atrioventricular block and decreased left ventricular diastolic function. Muscle MRI showed that semitendinosus, sartorius, gracilis, fibula, gastronemius and supinator muscles were selectively involved at the early stage. Muscle biopsy confirmed pathological changes of desmin positive myofibrils. Genetic testing revealed that the patient has harbored a c.1024A>G (p.n342d) missense variant in exon 6 of the DES gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was rated as likely pathogenic (PS4_moderate+PM2_supporting+PP3_moderate+PP1). Desmin disease has a great clinical heterogeneity. Postexercise myalgia of lower limbs is a rare clinical phenotype. For patients harboring the c.1024A>G (p.n342d) variant of the DES gene, in addition to semitendinosus and fibula, Cardiac involvement is relatively insidious and easy to be ignored in clinic. Timely muscle MRI, muscle biopsy and gene detection will help the early diagnosis of the disease.

A novel biomarker of fibrofatty replacement in dystrophinopathies identified by integrating transcriptome, magnetic resonance imaging, and pathology data.

We aimed to analyse genome-wide transcriptome differences between Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) patients and identify biomarkers that correlate well with muscle magnetic resonance imaging (MRI) and histological fibrofatty replacement in both patients, which have not been reported. One hundred and one male patients with dystrophinopathies (55 DMD and 46 BMD) were enrolled. Muscle-derived genome-wide RNA-sequencing was performed in 31 DMD patients, 29 BMD patients, and 11 normal controls. Fibrofatty replacement was scored on muscle MRI and histological levels in all patients. A unique pipeline, single-sample gene set enrichment analysis combined with Spearman's rank correlations (ssGSEA-Cor) was developed to identify the most correlated gene signature for fibrofatty replacement. Quantitative real-time PCR (qRT-PCR) analysis, western blot analysis, and single-nucleus RNA-sequencing (snRNA-seq) were performed in the remaining patients to validate the most correlated gene signature. Comparative transcriptomic analysis revealed that 31 DMD muscles were characterized by a significant increase of inflammation/immune response and extracellular matrix remodelling compared with 29 BMD muscles (P<0.05). The ssGSEA-Cor pipeline revealed that the gene set of CDKN2A and CDKN2B was the most correlated gene signature for fibrofatty replacement (histological rs =0.744, P<0.001; MRI rs =0.718, P<0.001). Muscle qRT-PCR confirmed that CDKN2A mRNA expression in both 15 DMD (median=25.007, P<0.001) and 12 BMD (median=5.654, P<0.001) patients were significantly higher than that in controls (median=1.101), while no significant difference in CDKN2B mRNA expression was found among DMD, BMD, and control groups. In the 27 patients, muscle CDKN2A mRNA expression respectively correlated with muscle MRI (rs =0.883, P<0.001) and histological fibrofatty replacement (rs =0.804, P<0.001) and disease duration (rs =0.645, P<0.001) and North Star Ambulatory Assessment total scores (rs =-0.698, P<0.001). Muscle western blot analysis confirmed that both four DMD (median=2.958, P<0.05) and four BMD (median=1.959, P<0.01) patients had a significantly higher level of CDKN2A protein expression than controls (median=1.068). The snRNA-seq analysis of two DMD muscles revealed that CDKN2A was mainly expressed in fibro-adipogenic progenitors, satellite cells, and myoblasts. We identify CDKN2A expression as a novel biomarker of fibrofatty replacement, which might be a new target for antifibrotic therapy in dystrophinopathies.

Whole-Body Muscle Magnetic Resonance Imaging in 81 Patients with Spinal and Bulbar Muscular Atrophy: A Prospective Study.

Spinal and bulbar muscular atrophy (SBMA) is characterized by slow, progressive bulbar and limb muscle weakness; however, the pattern of progression of muscle fat infiltration remains unclear. We assessed the progression of muscle involvement in 81 patients with SBMA using whole-body muscle magnetic resonance imaging (MRI), alongside clinical and laboratory findings. This prospective study included patients with genetically confirmed SBMA who underwent whole-body muscle MRI. We analyzed muscle fat infiltration and the pattern of involved muscles using cluster analysis, visualizing the sequential progression of fat infiltration. Muscle clusters demonstrated correlation with clinical scales and laboratory findings. Additionally, linear regression analysis was performed to identify the MRI section most strongly associated with 6-minute walk test (6MWT). We included 81 patients with SBMA (age = 54.3 years). After categorizing the patients into 6 clusters based on the pattern of muscle fat infiltration, we observed that muscle involvement began in the posterior calf and progressed to the posterior thigh, pelvis, trunk, anterior thigh, medial thigh, anterior calf, and upper extremity muscles. These muscle clusters correlated significantly with disease duration (τ = 0.47, p < 0.001), 6MWT (τ = -0.49, p < 0.001), and serum creatinine level (τ = -0.46, p < 0.001). The whole-body MRI indicated the thigh as the section most significantly correlated with 6MWT. We used whole-body muscle MRI to determine the sequential progression of the fat infiltration in SBMA. Our findings may enable the identification of objective and reliable imaging outcome measures in the study of the natural history or future clinical trials of SBMA. ANN NEUROL 2024;95:596-606.

Muscle fibrosis as a prognostic biomarker in facioscapulohumeral muscular dystrophy: a retrospective cohort study

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant epigenetic disorder with highly variable muscle involvement and disease progression. Ongoing clinical trials, aimed at counteracting muscle degeneration and disease progression in FSHD patients, increase the need for reliable biomarkers. Muscle magnetic resonance imaging (MRI) studies showed that the appearance of STIR-positive (STIR+) lesions in FSHD muscles represents an initial stage of muscle damage, preceding irreversible adipose changes. Our study aimed to investigate fibrosis, a parameter of muscle degeneration undetectable by MRI, in relation to disease activity and progression of FSHD muscles. We histologically evaluated collagen in FSHD1 patients’ (STIR+ n = 27, STIR− n = 28) and healthy volunteers’ (n = 12) muscles by picrosirius red staining. All patients (n = 55) performed muscle MRI before biopsy, 45 patients also after 1 year and 36 patients also after 2 years. Fat content (T1 signal) and oedema/inflammation (STIR signal) were evaluated at baseline and at 1- and 2-year MRI follow-up. STIR+ muscles showed significantly higher collagen compared to both STIR− (p = 0.001) and healthy muscles (p < 0.0001). STIR− muscles showed a higher collagen content compared to healthy muscles (p = 0.0194). FSHD muscles with a worsening in fatty infiltration during 1- (P = 0.007) and 2-year (P < 0.0001) MRI follow-up showed a collagen content of 3.6- and 3.7-fold higher compared to FSHD muscles with no sign of progression. Moreover, the fibrosis was significantly higher in STIR+ muscles who showed a worsening in fatty infiltration in a timeframe of 2 years compared to both STIR− (P = 0.0006) and STIR+ muscles with no sign of progression (P = 0.02). Fibrosis is a sign of muscle degeneration undetectable at MRI never deeply investigated in FSHD patients. Our data show that 23/27 of STIR+ and 12/28 STIR− muscles have a higher amount of collagen deposition compared to healthy muscles. Fibrosis is higher in FSHD muscles with a worsening in fatty infiltration thus suggesting that its evaluation with innovative non-invasive techniques could be a candidate prognostic biomarker for FSHD, to be used to stratify patients and to evaluate the efficacy of therapeutic treatments.

Muscle magnetic resonance imaging of a large cohort of distal hereditary motor neuropathies reveals characteristic features useful for diagnosis

Distal motor neuropathies (dHMN) are an heterogenous group of diseases characterized by progressive muscle weakness affecting predominantly the distal muscles of the lower and upper limbs. Our aim was to study the imaging features and pattern of muscle involvement in muscle magnetic resonance imaging (MRI) in dHMN patients of suspected genetic origin (dHMN). We conducted a retrospective study collecting clinical, genetic and muscle imaging data. Muscle MRI included T1-weighted and T2 weighted Short Tau Inversion Recovery images (STIR-T2w) sequences. Muscle replacement by fat was quantified using the Mercuri score. Identification of selective patterns of involvement was performed using hierarchical clustering. Eighty-four patients with diagnosis of dHMN were studied. Fat replacement was predominant in the distal lower leg muscles (82/84 cases), although also affected thigh and pelvis muscles. Asymmetric involvement was present in 29% of patients. The superficial posterior compartment of the leg, including the soleus and gastrocnemius muscles, was the most affected area (77/84). We observed a reticular pattern of fatty replacement progressing towards what is commonly known as “muscle islands” in 79.8%. Hyperintensities in STIR-T2w were observed in 78.6% patients mainly in distal leg muscles. Besides features common to all individuals, we identified and describe a pattern of muscle fat replacement characteristic of BICD2, HSPB1 and DYNC1H1 patients. We conclude that muscle MRI of patients with suspected dHMN reveals common features helpful in diagnosis process.

Magnetic resonance imaging findings of the lower limb muscles in anti-mitochondrial M2 antibody-positive myositis

Anti-mitochondrial M2 antibody (AMA-M2)-positive myositis is an idiopathic inflammatory myopathy (IIM). Of all patients with myositis, 2.5–19.5% have AMA-M2 antibodies. However, the detailed distribution of muscles affected in AMA-positive myositis is unknown. Therefore, we examined lower muscle magnetic resonance imaging (MRI) findings of patients with AMA-positive myositis. Among the 63 patients with IIM at our institute, 5 (7.9%) were positive for AMA-M2 antibodies. However, one was also positive for anti-Jo1 antibodies; therefore, four patients were finally participated in this study. All patients had high-intensity MRI signals in the proximal muscles, including the gluteus maximus and iliopsoas muscles, and in the thigh muscles, including the vastus lateralis, vastus medialis, adductor magnus, and semimembranosus muscles. Lower leg muscles were relatively spared. Fascial edema was observed in all patients and was also present in the lower leg muscles. Subcutaneous edema was observed, particularly in the proximal portion of the lower limbs. In AMA-positive myositis, proximal muscles, including the gluteus maximus, vastus lateralis, adductor magnus, and the semimembranosus, were markedly affected, while the lower leg muscles were relatively preserved. Additionally, fascial edema was evident even in lower leg muscles. Therefore, muscle MRI can be a useful diagnostic aid for AMA-positive myositis.

Five-year follow-up study on quantitative muscle magnetic resonance imaging in facioscapulohumeral muscular dystrophy: The link to clinical outcome.

It is unclear how changes in quantitative muscle magnetic resonance imaging (MRI) relate to changes in clinical outcome in facioscapulohumeral muscular dystrophy (FSHD), although this information is crucial for optimal use of MRI as imaging biomarker in trials. We therefore assessed muscle MRI and clinical outcome measures in a large longitudinal prospective cohort study. All patients were assessed by MRI at baseline and at 5-year follow-up, employing 2pt-Dixon and turbo inversion recovery magnitude (TIRM) sequences, after which fat fraction and TIRM positivity of 19 leg muscles were determined bilaterally. The MRI compound score (CoS) was defined as the mean fat fraction of all muscles weighted for cross-sectional area. Clinical outcome measures included the Ricci-score, FSHD clinical score (FSHD-CS), MRC sumscore (MRC-SS), and motor-function-measure (MFM). We included 105 FSHD patients [mean age 54±14years, median Ricci-score 7 (range 0-10)]. The median change over 5years' time in the MRI-CoS was 2.0% (range -4.6 to +12.1; P<0.001). The median change over 5years' time in clinical outcome measures was small in all measures, with z-scores ranging from 5.0 to 7.2 (P<0.001). The change in MRI-CoS correlated with change in FSHD-CS and Ricci-score (ρ=0.25, respectively; ρ=0.23, P<0.05). The largest median increase in MRI-CoS was seen in baseline subgroups with an MRI-CoS 20-40% (6.1%), with ≥2 TIRM positive muscles (3.5%) or with an FSHD-CS 5-10 (3.1%). This 5-year study showed significant changes in MRI and clinical outcome measures and a significant correlation between changes in MRI-CoS and changes in clinical outcome measures. In addition, we identified subgroups of patients that are most prone to radiological disease progression. This knowledge further establishes quantitative MRI parameters as prognostic biomarkers in FSHD and as efficacy biomarkers in upcoming clinical trials.

Clinical-pathological features and muscle imaging findings in 36 Chinese patients with rimmed vacuolar myopathies: case series study and review of literature.

Rimmed vacuolar myopathies (RVMs) are a group of genetically heterogeneous diseases that share histopathological characteristics on muscle biopsy, including the aberrant accumulation of autophagic vacuoles. However, the presence of non-coding sequences and structural mutations, some of which remain undetectable, confound the identification of pathogenic mutations responsible for RVMs. Therefore, we assessed the clinical profiles and muscle magnetic resonance imaging (MRI) changes in 36 Chinese patients with RVMs, emphasizing the role of muscle MRI in disease identification and differential diagnosis to propose a comprehensive literature-based imaging pattern to facilitate improved diagnostic workup. All patients presented with rimmed vacuoles with varying degrees of muscular dystrophic changes and underwent a comprehensive evaluation using clinical, morphological, muscle MRI and molecular genetic analysis. We assessed muscle changes in the Chinese RVMs and provided an overview of the RVMs, focusing on the patterns of muscle involvement on MRI. A total of 36 patients, including 24 with confirmed distal myopathy and 12 with limb-girdle phenotype, had autophagic vacuoles with RVMs. Hierarchical clustering of patients according to the predominant effect of the distal or proximal lower limbs revealed that most patients with RVMs could be distinguished. GNE myopathy was the most prevalent form of RVMs observed in this study. Moreover, MRI helped identify the causative genes in some diseases (e.g., desminopathy and hereditary myopathy with early respiratory failure) and confirmed the pathogenicity of a novel mutation (e.g., adult-onset proximal rimmed vacuolar titinopathy) detected using next-generation sequencing. Collectively, our findings expand our knowledge of the genetic spectrum of RVMs in China and suggest that muscle imaging should be an integral part of assisting genetic testing and avoiding misdiagnosis in the diagnostic workup of RVM.

Expanding the muscle imaging spectrum in dysferlinopathy: description of an outlier population from the classical MRI pattern

Dysferlinopathy is a muscle disease characterized by a variable clinical presentation and is caused by mutations in the DYSF gene. The Jain Clinical Outcome Study for Dysferlinopathy (COS) followed the largest cohort of patients (n=187) with genetically confirmed dysferlinopathy throughout a three-year natural history study, in which the patients underwent muscle function tests and muscle magnetic resonance imaging (MRI). We previously described the pattern of muscle pathology in this population and established a series of imaging criteria for diagnosis. In this paper, we describe the muscle imaging and clinical features of a subgroup of COS participants whose muscle imaging results did not completely meet the diagnostic criteria. We reviewed 184 T1-weighted (T1w) muscle MRI scans obtained at the baseline visit of the COS study, of which 106 were pelvic and lower limb only and 78 were whole-body scans. We identified 116 of the 184 patients (63%) who did not meet at least one of the established imaging criteria. The highest number found of unmet criteria was four per patient. We identified 24 patients (13%) who did not meet three or more of the nine established criteria and considered them as “outliers”. The most common unmet criterion (27.3% of cases) was the adductor magnus being equally or more affected than the adductor longus. We compared the genetic, demographic, clinical and muscle function data of the outlier patients with those who met the established criteria and observed that the outlier patients had an age of disease onset that was significantly older than the whole group (29.3 vs 20.5 years, p=0.0001). This study expands the phenotypic muscle imaging spectrum of patients with dysferlinopathy and can help to guide the diagnostic process in patients with limb girdle weakness of unknown origin.

Quantitative muscle magnetic resonance imaging depicts microstructural abnormalities but no signs of inflammation or dystrophy in post-COVID-19 condition.

Post-COVID-19 condition (PCC) has high impact on quality of life, with myalgia and fatigue affecting at least 25% of PCC patients. This case-control study aims to noninvasively assess muscular alterations via quantitative muscle magnetic resonance imaging (MRI) as possible mechanisms for ongoing musculoskeletal complaints and premature exhaustion in PCC. Quantitative muscle MRI was performed on a 3 Tesla MRI scanner of the whole legs in PCC patients compared to age- and sex-matched healthy controls, including a Dixon sequence to determine muscle fat fraction (FF), a multi-echo spin-echo sequence for quantitative water mapping reflecting putative edema, and a diffusion-weighted spin-echo echo-planar imaging sequence to assess microstructural alterations. Clinical examination, nerve conduction studies, and serum creatine kinase were performed in all patients. Quantitative muscle MRI results were correlated to the results of the 6-min walk test and standardized questionnaires assessing quality of life, fatigue, and depression. Twenty PCC patients (female: n= 15, age=48.8±10.1 years, symptoms duration=13.4± 4.2months, body mass index [BMI] = 28.8±4.7kg/m2 ) were compared to 20 healthy controls (female: n= 15, age=48.1± 11.1 years, BMI=22.9± 2.2kg/m2 ). Neither FF nor T2 revealed signs of muscle degeneration or inflammation in either study groups. Diffusion tensor imaging (DTI) revealed reduced mean, axial, and radial diffusivity in the PCC group. Quantitative muscle MRI did not depict any signs of ongoing inflammation or dystrophic process in the skeletal muscles in PCC patients. However, differences observed in muscle DTI depict microstructural abnormalities, which may reflect potentially reversible fiber hypotrophy due to deconditioning. Further longitudinal and interventional studies should prove this hypothesis.

Magnetic resonance imaging for the diagnosis of muscular dystrophy

To summarize the skeletal muscle magnetic resonance imaging (MRI) features of the lower limbs in common subtypes of muscular dystrophy (MD) and the experience in the application of MRI in the diagnosis of MD. A total of 48 children with MD who were diagnosed by genetic testing were enrolled as subjects. The muscle MRI features of the lower limbs were analyzed. Cumulative fatty infiltration score was calculated for each subtype, and the correlation of cumulative fatty infiltration score with clinical indices was analyzed for Duchenne muscular dystrophy (DMD). DMD was characterized by the involvement of the gluteus maximus and the adductor magnus. Becker muscular dystrophy was characterized by the involvement of the vastus lateralis muscle. Limb-girdle muscular dystrophy was characterized by the involvement of the adductor magnus, the vastus intermedius, the vastus medialis, and the vastus lateralis muscle. For DMD, the cumulative fatty infiltration score of the lower limb muscles was significantly correlated with age, course of the disease, muscle strength, and motor function (P<0.05), while it was not significantly correlated with the serum creatine kinase level (P>0.05). Different subtypes of MD have different MRI manifestations, and MRI may help with the diagnosis and assessment of MD.

Muscle magnetic resonance imaging abnormality in neuroleptic malignant syndrome: a case report

BackgroundNeuroleptic malignant syndrome (NMS) is a rare and occasionally fatal undesirable reaction to dopamine antagonists, and its phenotype is diverse owing to causative drugs. Classically, elevation of serum creatine kinase is described in NMS. Some reports have described muscular pathological findings; however, muscle magnetic resonance imaging (MRI) has not been reported previously.Case presentationA 63-year-old woman with a history of schizophrenia presented to our hospital with a high fever, excessive sweating, muscle weakness, and elevated serum creatine kinase levels. Muscle MRI revealed T2 high-intensity lesions in several muscles with gadolinium enhancement, and the pathology of the muscle biopsy showed a very mild presence of muscle fiber necrosis and regeneration with type 2c fibers without inflammation. Her symptoms resolved by treatment with levodopa/carbidopa, dantrolene. Finally, the patient was diagnosed with NMS.ConclusionsThis is the first report of muscle MRI abnormalities in a patient with NMS. Muscle MRI abnormalities in NMS may be associated with non-inflammatory myopathic changes. The cause of creatine kinase elevation cannot be explained by abnormal strong muscle contraction nor inflammation.

FP.09 Analysis of muscle MRI of a large cohort of chronic motor neuropathy/neuronopathy patients reveals characteristic features useful for diagnosis

Chronic motor neuropathy/neuronopathy (CMNs) encompass a group of rare diseases characterized by muscle weakness mainly affecting distal muscles of the limbs. Muscle magnetic resonance imaging (MRI) can be a useful tool for the diagnostic workup but has not been explored systematically in these patients. This is a retrospective study collecting clinical, genetic and imaging data. Muscle MRI included T1-weighted and Short Tau Inversion Recovery (STIR) sequences. Fat replacement was quantified using the Mercuri score. Identification of patterns was performed using hierarchical clustering. We included 76 patients with a clinical and electrophysiological diagnosis of CMN. A pathogenic gene variant was identified in 29 subjects, a VUS was identified in 15 and 32 subjects remained without molecular diagnosis. We collected 25 whole-body and 51 lower limb (LL) MRIs. All patients but one had pathological findings. We identified features common to all patients regardless of the genetic diagnosis. Muscle fat replacement was predominant in the LL distal muscles (75/76 cases), but also affected the thigh in 59, the pelvis in 18 and the trunk/upper limb muscles in seven. The posterior compartment of the leg, including soleus and gastrocnemius, was the most affected (71/76) followed by the peronei (63/76). Asymmetric involvement was found in 19 patients. A distal to proximal gradient of fat replacement was observed in 39 patients (52%). Texture analysis showed a reticular pattern or "muscle islets" in 63 patients (83%). Hyperintensities on STIR were observed in 49/59 and were predominantly located in the distal LL muscles. A distal to proximal gradient in STIR was observed in 25 subjects. Besides features common to all individuals, we identified a pattern of muscle fat replacement characteristic of BICD2 and HSPB1 patients. We did not identify a correlation between fat content and age, disease duration or motor functionality. Muscle MRI of CMN patients reveals common features that could be helpful for the diagnosis of patients. We have observed a pattern of MRI involvement characteristic of patients with mutations in specific genes. There was no correlation between fat content and functional status or time of disease progression.

An Automated Deep Learning Based Muscular Dystrophy Detection and Classification Model

Muscular Dystrophy (MD) is a group of inherited muscular diseases that are commonly diagnosed with the help of techniques such as muscle biopsy, clinical presentation, and Muscle Magnetic Resonance Imaging (MRI). Among these techniques, Muscle MRI recommends the diagnosis of muscular dystrophy through identification of the patterns that exist in muscle fatty replacement. But the patterns overlap among various diseases whereas there is a lack of knowledge prevalent with regards to disease-specific patterns. Therefore, artificial intelligence techniques can be used in the diagnosis of muscular dystrophies, which enables us to analyze, learn, and predict for the future. In this scenario, the current research article presents an automated muscular dystrophy detection and classification model using Synergic Deep Learning (SDL) method with extreme Gradient Boosting (XGBoost), called SDL-XGBoost. SDL-XGBoost model has been proposed to act as an automated deep learning (DL) model that examines the muscle MRI data and diagnose muscular dystrophies. SDL-XGBoost model employs Kapur's entropy based Region of Interest (RoI) for detection purposes. Besides, SDL-based feature extraction process is applied to derive a useful set of feature vectors. Finally, XGBoost model is employed as a classification approach to determine proper class labels for muscle MRI data. The researcher conducted extensive set of simulations to showcase the superior performance of SDL-XGBoost model. The obtained experimental values highlighted the supremacy of SDL-XGBoost model over other methods in terms of high accuracy being 96.18% and 94.25% classification performance upon DMD and BMD respectively. Therefore, SDL-XGBoost model can help physicians in the diagnosis of muscular dystrophies by identifying the patterns of muscle fatty replacement in muscle MRI.