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ObjectivesThe aims of this study were to define the pattern of muscle involvement in patients with immune-mediated necrotising myopathy (IMNM) relative to those with other inflammatory myopathies and to compare patients with IMNM with different autoantibodies.MethodsAll Johns Hopkins Myositis Longitudinal Cohort subjects with a thigh MRI (tMRI) who fulfilled criteria for IMNM, dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM) or clinically amyopathic DM (CADM) were included in the study. Muscles were assessed for intramuscular and fascial oedema, atrophy and fatty replacement. Disease subgroups were compared using univariate and multivariate analyses. Patients with IMNM with anti-signal recognition particle (SRP) autoantibodies were compared with those with IMNM with anti-HMG-CoA reductase (HMGCR) autoantibodies.ResultsThe study included 666 subjects (101 IMNM, 176 PM, 219 DM, 17 CADM and 153 IBM). Compared with DM or PM, IMNM was characterised by a higher proportion of thigh muscles with oedema, atrophy and fatty replacement (p<0.01). Patients with IMNM with anti-SRP had more atrophy (19%, p=0.003) and fatty replacement (18%, p=0.04) than those with anti-HMGCR. In IMNM, muscle abnormalities were especially common in the lateral rotator and gluteal groups. Fascial involvement was most widespread in DM. Fatty replacement of muscle tissue began early during the course of disease in IMNM and the other groups. An optimal combination of tMRI features had only a 55% positive predictive value for diagnosing IMNM.ConclusionsCompared with patients with DM or PM, IMNM is characterised by more widespread muscle involvement. Anti-SRP-positive patients have more severe muscle involvement than anti-HMGCR-positive patients.

The purpose of this article is to review calcified or ossified benign soft tissue lesions that may simulate malignancy. We review the clinical presentations, locations, imaging characteristics, and differential diagnostic considerations of myositis ossificans, tophaceous gout, benign vascular lesions, calcific tendinopathy with osseous involvement, periosteal chondroma, primary synovial chondromatosis, Hoffa’s disease, tumoral calcinosis, lipoma with metaplasia, calcifying aponeurotic fibroma, calcific myonecrosis, ancient schwannoma, and Castleman disease.

Background Muscle dysfunction in chronic obstructive pulmonary disease (COPD) represents a significant extrapulmonary manifestation. Yet, the role of muscle fat infiltration (myosteatosis) in paraspinal muscles remains incompletely characterized. This study investigated whether paraspinal myosteatosis and its distribution patterns are associated with COPD and pulmonary function. Methods Within the population-based KORA cohort, 214 participants underwent whole-body magnetic resonance imaging and pulmonary function testing. Paraspinal myosteatosis was quantified by chemical shift-encoded MRI at lumbar vertebra 3 (L3), from which proton density fat fraction (PDFF, in %) maps were derived. Intramyocellular (IMCL) and extramyocellular lipids (EMCL) were determined through voxel-based analysis using validated PDFF thresholds. COPD was defined spirometrically as FEV1/FVC below the lower limit of normal. Associations were examined using multivariable regression models adjusted for age, sex, smoking status, physical activity, and body mass index. Results Among participants (mean age 58.5 ± 5.8 years, 56.1% male), 24 (11.2%) had spirometrically defined COPD. Participants with COPD showed higher paraspinal PDFF (19.9 ± 7.0% vs. 18.3 ± 7.6%) and lower IMCL/EMCL ratios (1.0 ± 0.4 vs. 1.2 ± 0.6) compared to those without COPD. After adjustment, higher PDFF was independently associated with increased odds of COPD (OR 1.69, 95% CI: 1.01–2.84, p  = 0.046), while a higher IMCL to EMCL ratio showed protective associations (OR 0.49, 95% CI: 0.24-1.00, p  = 0.050). Both total paraspinal PDFF and EMCL were negatively associated with pulmonary gas exchange capacity (TLCO/VA: β=-0.19, 95% CI: -0.35–0.04, p  = 0.016 and β=-0.18, 95% CI: -0.33–0.03, p  = 0.022, respectively). Conversely, higher IMCL/EMCL ratios were associated with better gas exchange (TLCO/VA: β = 0.15, 95% CI: 0.01–0.29, p  = 0.031). Conclusions This population-based study demonstrates that while increased total paraspinal muscle fat content is associated with higher COPD risk, its compartmental distribution reveals distinct patterns: A higher proportion of IMCL relative to EMCL shows protective associations, potentially reflecting preserved type I oxidative muscle fiber characteristics. These findings suggest that muscle fat distribution patterns may serve as imaging markers of metabolic adaptation in COPD, offering new perspectives for disease monitoring and therapeutic approaches.

This article will review the anatomy and common pathologies affecting the peroneus longus muscle and tendon. The anatomy of the peroneus longus is complex and its long course can result in symptomatology referable to the lower leg, ankle, hindfoot, and plantar foot. Proximally, the peroneus longus muscle lies within the lateral compartment of the lower leg with its distal myotendinous junction arising just above the level of the ankle. The distal peroneus longus tendon has a long course and makes two sharp turns at the lateral ankle and hindfoot before inserting at the medial plantar foot. A spectrum of pathology can occur in these regions. At the lower leg, peroneus longus muscle injuries (e.g., denervation) along with retromalleolar tendon instability/subluxation will be discussed. More distally, along the lateral calcaneus and cuboid tunnel, peroneus longus tendinosis and tears, tenosynovitis, and painful os peroneum syndrome (POPS) will be covered. Pathology of the peroneus longus will be illustrated using clinical case examples along its entire length; these will help the radiologist understand and interpret common peroneus longus disorders.

In 2021, the International Society of Physical and Rehabilitation Medicine (ISPRM) special interest group on sarcopenia included the quadriceps thickness assessed with ultrasound image as an indicator of muscle mass in the diagnosis criteria of sarcopenia. If quadriceps echo intensity of older inpatients is to be a strong predictor of quadriceps thickness, muscle quality of the quadriceps may be estimated by the muscle mass when diagnosing sarcopenia using the criteria of ISPRM. This study aimed to examine the association between muscle mass and fraction of intramuscular adipose tissue of the quadriceps in older inpatients. This cross-sectional study included 399 inpatients aged ≥ 65 years. Primary outcomes were muscle mass and fraction of intramuscular adipose tissue of the quadriceps. Images were acquired using a B-mode ultrasound. Muscle mass and fraction of intramuscular adipose tissue of the quadriceps were assessed based on the muscle thickness and echo intensity, respectively. A multiple regression analysis (forced entry method) was performed to confirm whether quadriceps echo intensity was related to quadriceps thickness even after adjusting for other factors. In the multiple regression analyses for both male and female models, quadriceps echo intensity (male: β = - 0.537, p < 0.001; female: β = - 0.438, p < 0.001), Geriatric Nutritional Risk Index (male: β = 0.236, p < 0.001; female: β = 0.213, p < 0.001), and subcutaneous fat thickness of the thigh (male: β = 0.197, p < 0.001; female: β = 0.248, p < 0.001) were independently and significantly associated with quadriceps thickness. Our results show that there is a negative and significant association between muscle mass and fraction of intramuscular adipose tissue in older inpatients. Muscle quality of the quadriceps in older inpatients may be estimated to some extent by the muscle mass.

Background The diagnosis of patients with mutations in the VCP gene can be complicated due to their broad phenotypic spectrum including myopathy, motor neuron disease and peripheral neuropathy. Muscle MRI guides the diagnosis in neuromuscular diseases (NMDs); however, comprehensive muscle MRI features for VCP patients have not been reported so far. Methods We collected muscle MRIs of 80 of the 255 patients who participated in the “VCP International Study” and reviewed the T1-weighted (T1w) and short tau inversion recovery (STIR) sequences. We identified a series of potential diagnostic MRI based characteristics useful for the diagnosis of VCP disease and validated them in 1089 MRIs from patients with other genetically confirmed NMDs. Results Fat replacement of at least one muscle was identified in all symptomatic patients. The most common finding was the existence of patchy areas of fat replacement. Although there was a wide variability of muscles affected, we observed a common pattern characterized by the involvement of periscapular, paraspinal, gluteal and quadriceps muscles. STIR signal was enhanced in 67% of the patients, either in the muscle itself or in the surrounding fascia. We identified 10 diagnostic characteristics based on the pattern identified that allowed us to distinguish VCP disease from other neuromuscular diseases with high accuracy. Conclusions Patients with mutations in the VCP gene had common features on muscle MRI that are helpful for diagnosis purposes, including the presence of patchy fat replacement and a prominent involvement of the periscapular, paraspinal, abdominal and thigh muscles.

BackgroundMyosin heavy chain 7 (MYH7)-related myopathies (MYH7-RMs) are a group of muscle disorders linked to pathogenic variants in the MYH7 gene, encoding the slow/beta-cardiac myosin heavy chain, which is highly expressed in skeletal muscle and heart. The phenotype is heterogeneous including distal, predominantly axial or scapuloperoneal myopathies with variable cardiac involvement.MethodsWe retrospectively analysed the clinical, muscle MRI, genetic and myopathological features of 57 MYH7 patients. Patients received a thorough neurological (n=57, 100%), cardiac (n=51, 89%) and respiratory (n=45, 79%) assessment. Muscle imaging findings and muscle biopsies were reappraised in 19 (33%) and 27 (47%) patients, respectively.ResultsWe identified three phenotypes with varying degrees of overlap: distal myopathy (70%), scapuloperoneal (23%) and axial with peculiar cervical spine rigidity called the ‘sphinx’ phenotype (7%). 14% of patients had either dilated cardiomyopathy, hypertrophic cardiomyopathy or left ventricular non-compaction cardiomyopathy. 31% of patients had prominent respiratory involvement, including all patients with the ‘sphinx’ phenotype. Muscle MRI showed involvement of tibialis anterior, followed by quadriceps, and erector spinae in patients with axial phenotype. Cores represented the most common myopathological lesion. We report 26 pathogenic variants of MYH7 gene, 9 of which are novel.Conclusions MYH7-RMs have a large phenotypic spectrum, including distal, scapuloperoneal or axial weakness, and variable cardiac and respiratory involvement. Tibialis anterior is constantly and precociously affected both clinically and on muscle imaging. Cores represent the most common myopathological lesion. Our detailed description of MYH7-RMs should improve their recognition and management.

A growing body of the literature supports the use of magnetic resonance imaging as a potential biomarker for disease severity in the hereditary myopathies. We performed a systematic review of the medical literature to evaluate patterns of fat infiltration observed in magnetic resonance imaging studies of muscular dystrophy and congenital myopathy. Searches were performed using MEDLINE, EMBASE, and grey literature databases. Studies that described fat infiltration of muscles in patients with muscular dystrophy or congenital myopathy were selected for full-length review. Data on preferentially involved or spared muscles were extracted for analysis. A total of 2172 titles and abstracts were screened, and 70 publications met our criteria for inclusion in the systematic review. There were 23 distinct genetic disorders represented in this analysis. In most studies, preferential involvement and sparing of specific muscles were reported. We conclude that magnetic resonance imaging studies can be used to identify distinct patterns of muscle involvement in the hereditary myopathies. However, larger studies and standardized methods of reporting are needed to develop imaging as a diagnostic tool in these diseases.

As the use of cross-sectional abdominal and pelvic imaging has increased exponentially in the past several decades, incidental musculoskeletal findings have become commonplace. These are often unrelated to the indication for the examination and are frequently referred to as the “radiologist’s blind spot” on these studies. The differential diagnosis for abnormalities of the paraspinal and pelvic musculature is, in many cases, quite different from the anterior abdominal wall muscles. Furthermore, due to their relatively deep location, pathology involving the former muscle groups is more likely to be clinically occult, often presenting only incidentally when the patient undergoes cross-sectional imaging. Effective treatment of diseases of these muscles is dependent on adherence to a diverse set of diagnostic and treatment algorithms. The purpose of this review article is to familiarize the radiologist with the unique pathology of these often-overlooked muscles of the abdomen and pelvis.