Muscle MRI in Duchenne muscular dystrophy: Evidence of a distinctive pattern

Thrown for a loop: fibro-adipogenic progenitors in skeletal muscle fibrosis

Fibro-adipogenic progenitors (FAPs) are key regulators of skeletal muscle regeneration and homeostasis. However, dysregulation of these cells leads to fibro-fatty infiltration across various muscle diseases. FAPs are the key source of extracellular matrix (ECM) deposition in muscle, and disruption to this process leads to a pathological accumulation of ECM, known as fibrosis. The replacement of contractile tissue with fibrotic ECM functionally impairs the muscle and increases muscle stiffness. FAPs and fibrotic muscle form a progressively degenerative feedback loop where, as a muscle becomes fibrotic, it induces a fibrotic FAP phenotype leading to further development of fibrosis. In this review, we summarize FAPs' role in fibrosis in terms of their activation, heterogeneity, contributions to fibrotic degeneration, and role across musculoskeletal diseases. We also discuss current research on potential therapeutic avenues to attenuate fibrosis by targeting FAPs.

Longitudinal study of multi-parameter quantitative magnetic resonance imaging in Duchenne muscular dystrophy: hyperresponsiveness of gluteus maximus and detection of subclinical disease progression in functionally stable patients

OBJECTIVE

To describe the disease progression of Duchenne muscular dystrophy (DMD) in the pelvic and thigh muscles over 1-year using multiple-parameter quantitative magnetic resonance imaging (qMRI), and to determine the most responsive muscle and predict subclinical disease progression in functionally stable patients.

METHODS

Fifty-four DMD patients (mean age 8.9 ± 2.5, range 5-15 years) completed baseline and 1-year follow-up qMRI examinations/biomarkers [3-point Dixon/fat fraction (FF); T1 mapping/T1; T2 mapping/T2]. Meanwhile, clinical assessments [NorthStar ambulatory assessment (NSAA) score] and timed function tests were performed in DMD patients. Twenty-four healthy male controls (range 5-15 years) accomplished baseline qMRI examinations. Group differences were compared using the Wilcoxon test. The standardized response mean (SRM) was taken as the responsiveness to the disease progression index.

RESULTS

FF, T1, and T2 in all DMD age subgroups changed significantly over 1-year (P < 0.05). Even in functionally stable patients (NSAA score increased, unchanged, or decreased by 1-point) over 1-year, significant increases in FF and T2 and decreases in T1 were observed in gluteus maximus (GMa), gluteus medius, vastus lateralis, and adductor magnus (P < 0.05). Overall, the SRM of FF, T1, and T2 was all the highest in GMa, which were 1.25, - 0.92, and 0.93, respectively.

CONCLUSIONS

qMRI biomarkers are responsive to disease progression and can also detect subclinical disease progression in functionally stable DMD patients over 1-year. GMa is the most responsive to disease progression of all the muscles analyzed.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ( http://www.chictr.org.cn/index.aspx ) ChiCTR1800018340, 09/12/2018, prospectively registered.

A new immunodeficient Duchenne muscular dystrophy rat model to evaluate engraftment after human cell transplantation

Duchenne muscular dystrophy (DMD) is an X-linked fatal muscular disease, affecting one in 3,500 live male births worldwide. Currently, there is no cure for this disease, except for steroid-based treatment to attenuate disease progression. Cell transplantation therapy is a promising therapeutic approach, however, there is a lack of appropriate animal models to conduct large-scale preclinical studies using human cells, including biochemical and functional tests. Here, we established an immunodeficient DMD rat model and performed exhaustive pathological analysis and transplantation efficiency evaluation to assess its suitability to study DMD. Our DMD rat model exhibited histopathological characteristics similar to those observed in human patients with DMD. Human myoblasts demonstrated successful engraftment following transplantation into these rats. Therefore, this immunodeficient DMD rat model would be useful in preclinical studies to develop cellular transplantation therapies for DMD.

The Dystrophinopathies

PURPOSE OF REVIEW

This article reviews the history, epidemiology, genetics, clinical presentation, multidisciplinary management, and established and emerging therapies for the dystrophinopathies.

RECENT FINDINGS

The multidisciplinary care of individuals with dystrophinopathies continues to improve in many ways, including early surveillance and implementation of respiratory, cardiac, and orthopedic health management. The era of genetic therapeutics has altered the treatment landscape in neuromuscular disorders, including the dystrophinopathies.

SUMMARY

The dystrophinopathies are a spectrum of X-linked genetic disorders characterized by childhood-onset progressive weakness and variable cardiac and cognitive involvement. Corticosteroids are the mainstay of therapy to slow disease progression. Additional strategies for disease amelioration and dystrophin restoration, including gene replacement therapy, are under investigation.

Utilization of T1-Mapping for the pelvic and thigh muscles in Duchenne Muscular Dystrophy: a quantitative biomarker for disease involvement and correlation with clinical assessments

BACKGROUND

Little is known about the disease distribution and severity detected by T1-mapping in Duchenne muscular dystrophy (DMD). Furthermore, the correlation between skeletal muscle T1-values and clinical assessments is less studied. Hence, the purposes of our study are to investigate quantitative T1-mapping in detecting the degree of disease involvement by detailed analyzing the hip and thigh muscle, future exploring the predicting value of T1-mapping for the clinical status of DMD.

METHODS

Ninety-two DMD patients were included. Grading fat infiltration and measuring the T1-values of 19 pelvic and thigh muscles (right side) in axial T1-weighted images (T1WI) and T1-maps, respectively, the disease distribution and severity were evaluated and compared. Clinical assessments included age, height, weight, BMI, wheelchair use, timed functional tests, NorthStar ambulatory assessment (NSAA) score, serum creatine kinase (CK) level. Correlation analysis were performed between the muscle T1-value and clinical assessments. Multiple linear regression analysis was conducted for the independent association of T1-value and motor function.

RESULTS

The gluteus maximus had the lowest T1-value, and the gracilis had the highest T1-value. T1-value decreased as the grade of fat infiltration increased scored by T1WI (P < 0.001). The decreasing of T1-values was correlated with the increase of age, height, weight, wheelchair use, and timed functional tests (P < 0.05). T1-value correlated with NSAA (r = 0.232-0.721, P < 0.05) and CK (r = 0.208-0.491, P < 0.05) positively. T1-value of gluteus maximus, tensor fascia, vastus lateralis, vastus intermedius, vastus medialis, and adductor magnus was independently associated with the clinical motor function tests (P < 0.05). Interclass correlation coefficient (ICC) analysis and Bland-Altman plots showed excellent inter-rater reliability of T1-value region of interest (ROI) measurements.

CONCLUSION

T1-mapping can be used as a quantitative biomarker for disease involvement, further assessing the disease severity and predicting motor function in DMD.

Ambulatory Duchenne muscular dystrophy children: cross-sectional correlation between function, quantitative muscle ultrasound and MRI

Duchenne muscular dystrophy (DMD) is a progressive genetic muscle disease. Quantitative muscle ultrasound (US), muscle MRI, and functional tools are important to delineate characteristics of muscle involvement. We aimed to establish correlations between clinical/functional and above-named imaging tools respecting their diagnostic and prognostic role in DMD children. A cross-sectional retrospective study of 27 steroid-naive, ambulant male children/adolescents with genetically-confirmed DMD (mean age, 8.8 ± 3.3 years). Functional performance was assessed using motor function measure (MFM) which assess standing/transfer (D1), proximal (D2) and distal (D3) motor function, and six-minute walk test (6MWT). Imaging evaluation included quantitative muscle MRI which measured muscle fat content in a specific location of right rectus femoris by mDixon sequence. Quantitative muscle US measured right rectus femoris muscle brightness in standardized US image as an indicator of muscle fat content. We found a highly significant positive correlation between the mean MFM total score and 6MWT (R = 0.537, p = 0.007), and a highly significant negative correlation between fat content by muscle US and MFM total score (R = -0.603, p = 0.006) and its D1 subscore (R =-0.712, p = 0.001), and a significant negative correlation between fat content by US and 6MWT (R = -0.529, p = 0.02), and a significant positive correlation between muscle fat content by mDixon MRI and patient's age (R = 0.617, p = 0.01). Quantitative muscle US correlates significantly with clinical/functional assessment tools as MFM and 6MWT, and augments their role in disease-tracking of DMD. Quantitative muscle US has the potential to act as a substitute to functional assessment tools.

Step Activity Monitoring in Boys with Duchenne Muscular Dystrophy and its Correlation with Magnetic Resonance Measures and Functional Performance

BACKGROUND

Muscles of boys with Duchenne muscular dystrophy (DMD) are progressively replaced by fatty fibrous tissues, and weakness leads to loss of ambulation (LoA). Step activity (SA) monitoring is a quantitative measure of real-world ambulatory function. The relationship between quality of muscle health and SA is unknown in DMD.

OBJECTIVE

To determine SA in steroid treated boys with DMD across various age groups, and to evaluate the association of SA with quality of muscle health and ambulatory function.

METHODS

Quality of muscle health was measured by magnetic resonance (MR) imaging transverse magnetization relaxation time constant (MRI-T2) and MR spectroscopy fat fraction (MRS-FF). SA was assessed via accelerometry, and functional abilities were assessed through clinical walking tests. Correlations between SA, MR, and functional measures were determined. A threshold value of SA was determined to predict the future LoA.

RESULTS

The greatest reduction in SA was observed in the 9- < 11years age group. SA correlated with all functional and MR measures.10m walk/run test had the highest correlation with SA. An increase in muscle MRI-T2 and MRS-FF was associated with a decline in SA. Two years prior to LoA, SA in boys with DMD was 32% lower than age matched boys with DMD who maintained ambulation for more than two-year period. SA monitoring can predict subsequent LoA in Duchenne, as a daily step count of 3200 at baseline was associated with LoA over the next two-years.

CONCLUSION

SA monitoring is a feasible and accessible tool to measure functional capacity in the real-world environment.

Sensitivity to behavioral stress impacts disease pathogenesis in dystrophin-deficient mice

Mutation to the gene encoding dystrophin can cause Duchenne muscular dystrophy (DMD) and increase the sensitivity to stress in vertebrate species, including the mdx mouse model of DMD. Behavioral stressors can exacerbate some dystrophinopathy phenotypes of mdx skeletal muscle and cause hypotension-induced death. However, we have discovered that a subpopulation of mdx mice present with a wildtype-like response to mild (forced downhill treadmill exercise) and moderate (scruff restraint) behavioral stressors. These "stress-resistant" mdx mice are more physically active, capable of super-activating the hypothalamic-pituitary-adrenal and renin-angiotensin-aldosterone pathways following behavioral stress and they express greater levels of mineralocorticoid and glucocorticoid receptors in striated muscle relative to "stress-sensitive" mdx mice. Stress-resistant mdx mice also presented with a less severe striated muscle histopathology and greater exercise and skeletal muscle oxidative capacity at rest. Most interestingly, female mdx mice were more physically active following behavioral stressors compared to male mdx mice; a response abolished after ovariectomy and rescued with estradiol. We demonstrate that the response to behavioral stress greatly impacts disease severity in mdx mice suggesting the management of stress in patients with DMD be considered as a therapeutic approach to ameliorate disease progression.

Quantitative Muscle MRI and Clinical Findings in Women With Pathogenic Dystrophin Gene Variants

Objective: To explore fat replacement, muscle strength, and clinical features in women heterozygous for a pathogenic DMD variant, we prospectively examined 53 women, assuming that some of these women—despite of the recessive X-linked inheritance—manifested clinical symptoms.

Methods: We performed a cross-sectional observational study using MRI and stationary dynamometry of lower extremities, extracted blood muscle biomarkers, and investigated subjective complaints. Results were compared with 19 healthy women.

Results:DMD variant carriers were weaker and had higher fat fractions than controls in all investigated muscle groups (p < 0.02). Fat fractions were 18% in carriers vs. 11% in controls in thighs (p = 0.008), and 15 vs. 11% in calf muscles (p = 0.032). Seventy-two percent had fat fractions deviating from controls by two standard deviations (SDs) in one or more of the 16 investigated muscle groups. On strength testing, 40% of the carriers had results deviating from control muscle strength by two SDs in one or more dynamometry assessments. Forty-three carriers (81%) had either reduced muscle strength (<2 SDs from control mean) and/or elevated muscle fat fraction (>2 SDs from control mean). Thirty of these had subjective symptoms. Blood creatine kinase and myoglobin were elevated in 57% of the carriers.

Conclusion: Using quantitative methods, this study shows that both clinically symptomatic and asymptomatic women with pathogenic DMD variants show a high prevalence of muscle affection. Longitudinal studies in female carriers of pathogenic DMD variants are needed to follow the evolution of these changes.

Whole-body muscle MRI characteristics of LAMA2-related congenital muscular dystrophy children: An emerging pattern

Merosin-deficient or LAMA2-related congenital muscular dystrophy (CMD) belongs to a group of muscle diseases with an overlapping diagnostic spectrum. MRI plays an important role in the diagnosis and disease-tracking of muscle diseases. Whole-body MRI is ideal for describing patterns of muscle involvement. We intended to analyze the pattern of muscle involvement in merosin-deficient CMD children employing whole-body muscle MRI. Ten children with merosin-deficient CMD underwent whole-body muscle MRI. Eight of which were genetically-confirmed. We used a control group of other hereditary muscle diseases, which included 13 children (mean age was 13 SD +/- 5.5 years), (8 boys and 5 girls) for comparative analysis. Overall, 37 muscles were graded for fatty infiltration using Mercuri scale modified by Fischer et al. The results showed a fairly consistent pattern of muscle fatty infiltration in index group, which differs from that in control group. There was a statistically significant difference between the two groups in regard to the fatty infiltration of the neck, serratus anterior, intercostal, rotator cuff, deltoid, triceps, forearm, gluteus maximus, gluteus medius, gastrocnemius and soleus muscles. Additionally, the results showed relative sparing of the brachialis, biceps brachii, gracilis, sartorius, semitendinosus and extensor muscles of the ankle in index group, and specific texture abnormalities in other muscles. There is evidence to suggest that whole-body muscle MRI can become a useful contributor to the differential diagnosis of children with merosin deficient CMD. The presence of a fairly characteristic pattern of involvement was demonstrated. MRI findings should be interpreted in view of the clinical and molecular context to improve diagnostic accuracy.

Using MRI to quantify skeletal muscle pathology in Duchenne muscular dystrophy: A systematic mapping review

There is a great demand for accurate non‐invasive measures to better define the natural history of disease progression or treatment outcome in Duchenne muscular dystrophy (DMD) and to facilitate the inclusion of a large range of participants in DMD clinical trials. This review aims to investigate which MRI sequences and analysis methods have been used and to identify future needs. Medline, Embase, Scopus, Web of Science, Inspec, and Compendex databases were searched up to 2 November 2019, using keywords “magnetic resonance imaging” and “Duchenne muscular dystrophy.” The review showed the trend of using T1w and T2w MRI images for semi‐qualitative inspection of structural alterations of DMD muscle using a diversity of grading scales, with increasing use of T2map, Dixon, and MR spectroscopy (MRS). High‐field (>3T) MRI dominated the studies with animal models. The quantitative MRI techniques have allowed a more precise estimation of local or generalized disease severity. Longitudinal studies assessing the effect of an intervention have also become more prominent, in both clinical and animal model subjects. Quality assessment of the included longitudinal studies was performed using the Newcastle‐Ottawa Quality Assessment Scale adapted to comprise bias in selection, comparability, exposure, and outcome. Additional large clinical trials are needed to consolidate research using MRI as a biomarker in DMD and to validate findings against established gold standards. This future work should use a multiparametric and quantitative MRI acquisition protocol, assess the repeatability of measurements, and correlate findings to histologic parameters.

A well-tolerated core needle muscle biopsy process suitable for children and adults

Serial muscle biopsies within clinical trials for Duchenne muscular dystrophy (DMD) are critical to document therapeutic responses. Less invasive means of sampling muscle are needed. We analyzed a retrospective consecutive case-series cohort of vacuum-assisted core needle muscle biopsy procedures performed on healthy and dystrophic individuals at a single institution assessing for safety and reliability of obtaining sufficient high-quality biopsy tissue for histologic assessment in adult and pediatric subjects. Of 471 muscle cores from 128 biopsy procedures, 377-550 mg of total muscle tissue was obtained per procedure with mean core weight of 129 mg (SD, 25.1 mg). All biopsies were adequate for histological assessment. There were no significant adverse events. This core needle biopsy approach, when combined with improved sample processing, provides a safe means to consistently obtain muscle samples for diagnostic and clinical trial applications.

MiRNAs, Myostatin, and Muscle MRI Imaging as Biomarkers of Clinical Features in Becker Muscular Dystrophy

Becker muscular dystrophy (BMD) is an X-linked recessive disorder caused by dystrophin gene mutations. The phenotype and evolution of this muscle disorder are extremely clinical variable. In the last years, circulating biomarkers have acquired remarkable importance in their use as noninvasive biological indicators of prognosis and in monitoring muscle disease progression, especially when associated to muscle MRI imaging. We investigated the levels of circulating microRNAs (myo-miRNAs and inflammatory miRNAs) and of the proteins follistatin (FSTN) and myostatin (GDF-8) and compared results with clinical and radiological imaging data. In eight BMD patients, including two cases with evolving lower extremity weakness treated with deflazacort, we evaluated the expression level of 4 myo-miRNAs (miR-1, miR-206, miR-133a, and miR-133b), 3 inflammatory miRNAs (miR-146b, miR-155, and miR-221), FSTN, and GDF-8 proteins. In the two treated cases, there was pronounced posterior thigh and leg fibrofatty replacement assessed by muscle MRI by Mercuri score. The muscle-specific miR-206 was increased in all patients, and inflammatory miR-221 and miR-146b were variably elevated. A significant difference in myostatin expression was observed between steroid-treated and untreated patients. This study suggests that microRNAs and myostatin protein levels could be used to better understand the progression and management of the disease.

Qualitative and quantitative muscle ultrasound in patients with Duchenne muscular dystrophy: Where do sonographic changes begin?

OBJECTIVE

The number of studies investigating and understanding the disease mechanisms of Duchenne muscular dystrophy (DMD) in human clinical trials have increased substantially over the last decade. Suitable clinical instruments for the measurement of disease progress and drug efficiency are mandatory, but currently not available, especially in the youngest patients. The aim of this study was to detect a reproducible pattern of muscle involvement in early stages potentially preceding evidence of motor regression.

MATERIAL AND METHODS

A cohort of 25 DMD patients aged 1-6 years at the first presentation were examined at multiple timepoints and compared with age-matched healthy controls. Muscle ultrasound was quantified using computer-analyzed gray scale levels (GSL) and blinded visual rating, using a modified Heckmatt scale.

RESULTS

Changes in muscle echogenicity in DMD patients occurred very early, clearly preceding motor regression and in some cases, even before the motor plateau phase was reached. Visual rating and GSL identified the earliest changes in the proximal adductor magnus muscle.

CONCLUSION

Muscle ultrasound can be used as an additional method to assess the disease progression and for decision-making in paucisymptomatic DMD patients. Sonographic changes in the ad-ductor magnus muscle seem to be the first detectable changes with a recognisable pattern.

Magnetic Resonance Imaging Studies in Duchenne Muscular Dystrophy: Linking Findings to the Physical Therapy Clinic

Duchenne muscular dystrophy (DMD) is a muscle degenerative disorder that manifests in early childhood and results in progressive muscle weakness. Physical therapists have long been an important component of the multidisciplinary team caring for people with DMD, providing expertise in areas of disease assessment, contracture management, assistive device prescription, and exercise prescription. Over the last decade, magnetic resonance imaging of muscles in people with DMD has led to an improved understanding of the muscle pathology underlying the clinical manifestations of DMD. Findings from magnetic resonance imaging (MRI) studies in DMD, paired with the clinical expertise of physical therapists, can help guide research that leads to improved physical therapist care for this unique patient population. The 2 main goals of this perspective article are to (1) summarize muscle pathology and disease progression findings from qualitative and quantitative muscle MRI studies in DMD and (2) link MRI findings of muscle pathology to the clinical manifestations observed by physical therapists with discussion of any potential implications of MRI findings on physical therapy management.

Myostatin Is a Quantifiable Biomarker for Monitoring Pharmaco-gene Therapy in Duchenne Muscular Dystrophy

Recently, several promising treatments have emerged for neuromuscular disorders, highlighting the need for robust biomarkers for monitoring therapeutic efficacy and maintenance of the therapeutic effect. Several studies have proposed circulating and tissue biomarkers, but none of them has been validated to monitor acute and long-term drug response. We previously described how the myostatin (MSTN) level is naturally downregulated in several neuromuscular diseases, including Duchenne muscular dystrophy (DMD). Here, we show that the dystrophin-deficient Golden Retriever muscular dystrophy (GRMD) dog model also presents an intrinsic loss of Mstn production in muscle. The abnormally low levels of Mstn observed in the GRMD dog puppies at 2 months were partially rescued at both mRNA and protein level after adeno-associated virus (AAV)-microdystrophin treatment in a dose-dependent manner. These results show that circulating Mstn is a robust and reliable quantitative biomarker, capable of measuring a therapeutic response to pharmaco-gene therapy in real time in the neuromuscular system, as well as a quantitative means for non-invasive follow-up of a therapeutic effect. Moreover, a 2-year follow-up also suggests that Mstn could be a longitudinal monitoring tool to follow maintenance or decrease of the therapeutic effect.

Muscle MRI: A biomarker of disease severity in Duchenne muscular dystrophy? A systematic review

OBJECTIVE

To assess the evidence of a relationship between muscle MRI and disease severity in Duchenne muscular dystrophy (DMD).

METHODS

We conducted a systematic review of studies that analyzed correlations between MRI measurements and motor function in patients with DMD. PubMed, Cochrane, Scopus, and Web of Science were searched using relevant keywords and inclusion/exclusion criteria (January 1, 1990-January 31, 2019). We evaluated article quality using the Joanna Briggs Institute scale. Information regarding the samples included, muscles evaluated, MRI protocols and motor function tests used was collected from each article. Correlations between MRI measurements and motor function were reported exhaustively.

RESULTS

Seventeen of 1,629 studies identified were included. Most patients included were ambulant with a mean age of 8.9 years. Most studies evaluated lower limb muscles. Moderate to excellent correlations were found between MRI measurements and motor function. The strongest correlations were found for quantitative MRI measurements such as fat fraction or mean T2. Correlations were stronger for lower leg muscles such as soleus. One longitudinal study reported that changes in soleus mean T2 were highly correlated with changes in motor function.

CONCLUSION

The findings of this systematic review showed that MRI measurements can be used as biomarkers of disease severity in ambulant patients with DMD. Guidelines are proposed to help clinicians choose the most appropriate MRI measurements and muscles to evaluate. Studies exploring upper limb muscles, other stages of the disease, and sensitivity of measurements to change are needed.

Value of muscle magnetic resonance imaging in the differential diagnosis of muscular dystrophies related to the dystrophin-glycoprotein complex

BACKGROUND

Dystrophin-glycoprotein complex (DGC)-related muscular dystrophies may present similar clinical and pathological features as well as undetectable mutations thus being sometimes difficult to distinguish. We investigated the value of muscle magnetic resonance imaging (MRI) in the differential diagnosis of DGC-related muscular dystrophies and reported the largest series of Chinese patients with sarcoglycanopathies studied by muscle MRI.

RESULTS

Fifty-five patients with DGC-related muscular dystrophies, including 22 with confirmed sarcoglycanopathies, 11 with limb-girdle muscular dystrophy 2I (LGMD2I, FKRP-associated dystroglycanopathy), and 22 with dystrophinopathies underwent extensive clinical evaluation, muscle biopsies, genetic analysis, and muscle MRI examinations. Hierarchical clustering of patients according to the clinical characteristics showed that patients did not cluster according to the genotypes. No statistically significant differences were observed between sarcoglycanopathies and LGMD2I in terms of thigh muscle involvement. The concentric fatty infiltration pattern was observed not only in different sarcoglycanopathies (14/22) but also in LGMD2I (9/11). The trefoil with single fruit sign was observed in most patients with dystrophinopathies (21/22), and a few patients with sarcoglycanopathies (4/22) or LGMD2I (2/11). Hierarchical clustering showed that most patients with sarcoglycanopathies or LGMD2I can be distinguished from dystrophinopathies based on the concentric fatty infiltration pattern and trefoil with single fruit sign at the thigh level on muscle MRI.

CONCLUSIONS

Muscle MRI at the thigh level potentially allows distinction of sarcoglycanopathies or FKRP-associated dystroglycanopathy from dystrophinopathies.

Automatic calculation of Mercuri grades from CT and MR muscle images

BACKGROUND

Mercuri grading of muscle images is a useful method to evaluate the progression of muscular dystrophies. However, because Mercuri grading is skill-based, few competent experts are available. We therefore developed an automated method for Mercuri grade calculations.

METHODS

We used computed tomography (CT) and magnetic resonance (MR) images of the thigh and lower leg muscles taken from a Japanese limb-girdle muscular dystrophy patient database. We calculated muscle impairment ratios based on the CT images, and then converted the ratios to revised Mercuri grades. This method was also applied to T1-weighted MR images. Additionally, radiation absorption doses in muscle and chest CT images from a separate patient group were also analyzed.

RESULTS

We observed a close correlation between our automatically calculated Mercuri grades and skill-based visually determined Mercuri grades in both CT and MR images. The radiation absorption, measured by total dose length product, was lower in muscle CT (121.8 mGy-cm) than in chest CT (524.1 mGy-cm).

CONCLUSIONS

We developed a new automatic Mercuri grading method using values obtained from CT images. This method was also applied to calculate the Mercuri grade of T1-weighted MR images. In addition, the radiation doses from muscle CT were observed to be lower than those from chest CT.

Sonoelastography of the trunk and lower extremity muscles in a case of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a rare genetic disorder typically presenting with muscle weakness and reduced tone of trunk and lower extremities. The sonoelastographic properties of DMD are poorly understood. We describe sonoelastographic characteristics of a patient's trunk and lower extremity musculature. An 8-year-old male presented with a 5-year history of DMD. Sonoelastographic measures of the gluteus maximus and medius, lumbar erector spinae, rectus abdominis, rectus femoris, biceps femoris, tibialis anterior, medial and lateral gastrocnemius muscles were obtained. Sonoelastography demonstrated increased elasticity by elevated kiloPascals (kPa) across all muscles, except the lumbar erector spinae. Patient values were compared to an age-matched healthy control. These abnormal sonoelastographic findings reflected the pathological mechanical properties of DMD. Sonoelastography was valuable for characterizing the mechanical properties of normal and abnormal muscle tissue. There is limited information on the sonoelastography application to DMD. Sonoelastography may serve as a useful measure for diagnosis and monitoring clinical outcomes for DMD.

Whole-body MRI and pathological findings in adult patients with myopathies

Magnetic resonance imaging (MRI) is considered the most sensitive and specific imaging technique for the detection of muscle diseases related to myopathies. Since 2008, the use of whole-body MRI (WBMRI) to evaluate myopathies has improved due to technical advances such as rolling table platform and parallel imaging, which enable rapid assessment of the entire musculoskeletal system with high-quality images. WBMRI protocols should include T1-weighted and short-tau inversion recovery (STIR), which provide the basic pulse sequences for studying myopathies, in order to detect fatty infiltration/muscle atrophy and muscle edema, respectively. High signal intensity in T1-weighted images shows chronic disease with fatty infiltration, whereas high signal intensity in STIR indicates an acute stage with muscle edema. Additional sequences such as diffusion-weighted imaging (DWI) can be readily incorporated into routine WBMRI study protocols. Contrast-enhanced sequences have not been done. This article reviews WBMRI as an imaging method to evaluate different myopathies (idiopathic inflammatory, dystrophic, non-dystrophic, metabolic, and channelopathies). WBMRI provides a comprehensive estimate of the total burden with a single study, seeking specific distribution patterns, including clinically silent involvement of muscle areas. Furthermore, WBMRI may help to select the "target muscle area" for biopsy during patient follow-up. It may be also be used to detect related and non-related pathological conditions, such as tumors.

T2 Mapping and Fat Quantification of Thigh Muscles in Children with Duchenne Muscular Dystrophy

Quantitative magnetic resonance image (MRI) in individual muscles may be useful for monitoring disease progression in Duchenne muscular dystrophy (DMD). The purpose of this study was to measure T2 relaxation time of thigh muscles in children with DMD and healthy boys, and to correlate the T2 relaxation time of muscles with the fat fraction (FF) at quantitative magnetic resonance and results of clinical assessment. Thirty-two boys with DMD and 18 healthy boys were evaluated with T2 mapping and three-point Dixon MRI. Age, body mass index (BMI), muscle strength assessment, timed functional tests (time to walk or run 10 metres, rise from the floor and ascend four stairs), and the North Star Ambulatory Assessment (NSAA) were evaluated. Spearman's correlation was used to assess the relationships between FF and clinical assessments and T2 relaxation time. The mean T2 relaxation time of thigh muscles in DMD was significantly longer than that in the control group (P<0.05), except for the gracilis (P=0.952). The gracilis, sartorius and adductor longus were relatively spared by fatty infiltration in DMD patients. The T2 relaxation time was correlated significantly with the mean FF in all muscles. Age, BMI, total muscle strength score, timed functional tests and NSAA were significantly correlated with the overall mean T2 relaxation time. T2 mapping may prove clinically useful in monitoring muscle changes as a result of the disease process and in predicting the outcome of DMD patients.

Advances in Quantitative Imaging of Genetic and Acquired Myopathies: Clinical Applications and Perspectives

In the last years, magnetic resonance imaging (MRI) has become fundamental for the diagnosis and monitoring of myopathies given its ability to show the severity and distribution of pathology, to identify specific patterns of damage distribution and to properly interpret a number of genetic variants. The advances in MR techniques and post-processing software solutions have greatly expanded the potential to assess pathological changes in muscle diseases, and more specifically of myopathies; a number of features can be studied and quantified, ranging from composition, architecture, mechanical properties, perfusion, and function, leading to what is known as quantitative MRI (qMRI). Such techniques can effectively provide a variety of information beyond what can be seen and assessed by conventional MR imaging; their development and application in clinical practice can play an important role in the diagnostic process and in assessing disease course and treatment response. In this review, we briefly discuss the current role of muscle MRI in diagnosing muscle diseases and describe in detail the potential and perspectives of the application of advanced qMRI techniques in this field.

Cardiac MRI biomarkers for Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a fatal inherited genetic disorder that results in progressive muscle weakness and ultimately loss of ambulation, respiratory failure and heart failure. Cardiac MRI (MRI) plays an increasingly important role in the diagnosis and clinical care of boys with DMD and associated cardiomyopathies. Conventional cardiac MRI biomarkers permit measurements of global cardiac function and presence of fibrosis, but changes in these measures are late manifestations. Emerging MRI biomarkers of myocardial function and structure include the estimation of rotational mechanics and regional strain using MRI tagging; T1-mapping; and T2-mapping, a marker of inflammation, edema and fat. These emerging biomarkers provide earlier insights into cardiac involvement in DMD, improving patient care and aiding the evaluation of emerging therapies.

Efficacy of stem cell therapy in ambulatory and nonambulatory children with Duchenne muscular dystrophy - Phase I-II

Purpose

Duchenne muscular dystrophy (DMD) is an X-linked recessive pediatric disorder that ultimately leads to progressive muscle degeneration. It has been known that cell-based therapies were used to promote muscle regeneration. The main purpose of this study was to investigate the effects of allogeneic Wharton jelly-derived mesenchymal stem cells therapy in Duchenne muscular dystrophy.

Patients and methods

Four ambulatory and five nonambulatory male patients were assessed as having acceptance criteria. Gene expression and immunohistochemical analysis were performed for dystrophin gene expression. The fluorescent in situ hybridization method was used for detection of chimerism and donor–recipient compatibility. Complement dependent lymphocytotoxic crossmatch test and detection of panel reactive antigen were performed. All patients were treated with 2 × 10⁶ cells/kg dose of allogeneic Wharton jelly-derived mesenchymal stem cells via intra-arterial and intramuscular administration. Stability was maintained in patient follow-up tests, which are respiratory capacity tests, cardiac measurements, and muscle strength tests.

Results

The vastus intermedius muscle was observed in one patient with MRI. Chimerism was detected by fluorescent in situ hybridization and mean gene expression was increased to 3.3-fold. An increase in muscle strength measurements and pulmonary function tests was detected. Additionally, we observed two of nine patients with positive panel reactive antigen result.

Conclusion

All our procedures are well tolerated, and we have not seen any application-related complications so far. Our main purpose of this study was to investigate the effects of allogeneic mesenchymal stem cell therapy and determine its suitability and safety as a form of treatment in this untreatable disorder.

Radiographic Risk Factors and Signs of Abductor Tears in the Hip

PURPOSE

The purpose of this study is to identify radiographic risk factors (RRFs) and radiographic signs of abductor tendon tears.

METHODS

Between April 2008 and October 2015, patients with intraoperative diagnosis of partial- or full-thickness abductor tear noted at the time of open or endoscopic treatment were included in this study. Exclusion criteria included lack of preoperative standard supine pelvic radiograph, lack of preoperative magnetic resonance imaging (MRI), or abductor tear not present at the time of operative intervention. Patients were matched by age ±5 years, gender, and body mass index ±5 with patients with no abductor pathology by clinical exam and MRI. A standardized supine anterior-posterior pelvis radiograph was performed on all patients. The radiographs were evaluated for RRF (pelvic width, body weight moment arm, abductor moment arm, abductor angle, pelvic height) and signs of abductor tendon pathology (greater trochanteric enthesophyte). Femoral version was measured on MRI when images were available. Statistical analysis was performed and included bivariate and multivariate analyses.

RESULTS

There were 152 patients with abductor tears identified at the time of surgery out of 2,838 eligible patients matched with 125 patients without abductor tendon pathology. The study institution was unable to perform a 1:1 match because of the advanced age of the abductor tendon group, which led to a greater age in the abductor group (n = 58) versus the control group (n = 54; P = .01. In abductor group the average age was 58, and 137 of 152 (90%) patients were female; in the control group the average age was 54, with 111 of 125 (89%) patients being female. Abductor tear patients were treated with surgical repair. The RRFs found with bivariate analysis were an increased pelvic width (14.8 cm for abductor tears vs 14.3 cm for control; P < .001), body weight moment arm (11.1 cm vs 10.9 cm; P < .001), and abductor moment arm (7.8 cm vs 7.6 cm; P < .001); decreased femoral anteversion (7.6° vs 10.6°; P = .045); and enthesophyte presence (41% vs 3%; P < .001). Multivariate regression analysis of all variables showed that teardrop distance and enthesophyte presence were the 2 variables most predictive of abductor tears, and other variables did not significantly increase or decrease the likelihood of tear when these 2 variables were considered. The presence of an enthesophyte on the greater trochanter was notable for an odds ratio of 20.7 of having an abductor tear.

CONCLUSIONS

Patients with abductor tears have a wider pelvis, longer abductor moment arm, and longer body weight moment arm and have greater trochanteric enthesophyte as noted on nearly half of patients with an abductor tear. Presence of an enthesophyte was noted to have an odds ratio of 20.7 and a positive predictive value of 94% for having an abductor tendon tear. The 2 variables predictive of abductor tendon tear when controlling for all variables were enthesophyte presence and teardrop distance, with no other variables significantly increasing or decreasing the likelihood of tear when these 2 variables were considered.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Advanced MRI Techniques for Muscle Imaging

Advanced magnetic resonance imaging (MRI) techniques can evaluate a wide array of muscle pathologies including acute or chronic muscle injury, musculotendinous response to injury, intramuscular collections and soft tissue masses, and others. In recent years, MRI has played a more important role in muscle disease diagnosis and monitoring. MRI provides excellent spatial and contrast resolution and helps direct optimal sites for muscle biopsy. Whole-body MRI now helps identify signature patterns of muscular involvement in large anatomical regions with relative ease. Quantitative MRI has advanced the evaluation and disease tracking of muscle atrophy and fatty infiltration in entities such as muscular dystrophies. Multivoxel magnetic resonance spectroscopy (MRS) now allows a more thorough, complete evaluation of a muscle of interest without the inherent sampling bias of single-voxel MRS or biopsy. Diffusion MRI allows quantification of muscle inflammation and capillary perfusion as well as muscle fiber tracking.

Muscle MRI findings in a one-year-old girl with merosin-deficient congenital muscular dystrophy type 1A due to LAMA2 mutation: A case report

The objective of the present study was to characterize the muscle magnetic resonance imaging (MRI) features of a 1-year-old girl with merosin-deficient congenital muscular dystrophy type 1A (MDC1A). Beginning as an infant, this patient exhibited severe hypotonia and proximal weakness, as well as delays in developmental milestones. Her serum creatine kinase levels at 3 months, 8 months and 1 year were 2,959, 1,621 and 1,659 U/l, respectively. Brain MRI indicated symmetric, mild T1WI low, mild T2WI and FLAIR high radial patterns in the white matter of the Cornu posterius of the ventricular lateral. Gene sequencing demonstrated a heterozygous frame-shift mutation in the LAMA2 gene, consisting of an AG deletion at nucleotides 2049-2050 (LAMA2 c.2049_2050delAG). Lower limb muscle MRI presented obvious fatty infiltration of the muscles and muscle atrophy during the early stage of the disease. The gluteus maximus, erector spinae, vastus intermedius, vastus lateralis, adductor magnus, soleus and gastrocnemius muscles were involved, whereas the piriformis, obturator internus, pectineus, adductor longus, adductor brevis and sartorius muscles presented mild or no involvement. Fatty infiltration of the erector spinae was observed during the early stage of the disease. As an additional tool in the differential diagnosis of muscle disorders, muscle MRI can delay the need for muscle biopsy.

Magnetic resonance imaging patterns of muscle involvement in genetic muscle diseases: a systematic review

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.