MRI for the demonstration of subclinical muscle involvement in muscular dystrophy

Usefulness and Clinical Impact of Whole-Body MRI in Detecting Autoimmune Neuromuscular Disorders

Autoimmune neuromuscular diseases are a group of heterogenous pathologies secondary to the activation of the immune system that damage the structures of the peripheric nerve, the neuromuscular junction, or the skeleton muscle. The diagnosis of autoimmune neuromuscular disorders comprises a combination of data from clinical, laboratory, electromyography, imaging exam, and biopsy. Particularly, the whole-body MRI examination in the last two decades has been of great use in the assessment of neuromuscular disorders. MRI provides information about the structures involved and the status of activity of the disease. It can also be used as a biomarker, detect the pattern of specific muscle involvement, and is a useful tool for targeting the optimal muscle site for biopsy. In this work, we summarized the most used technical protocol of whole-body MRI and the role of this imaging technique in autoimmune neuromuscular disorders.

Deformable image registration based on single or multi-atlas methods for automatic muscle segmentation and the generation of augmented imaging datasets

Muscle segmentation is a process relied upon to gather medical image-based muscle characterisation, useful in directly assessing muscle volume and geometry, that can be used as inputs to musculoskeletal modelling pipelines. Manual or semi-automatic techniques are typically employed to segment the muscles and quantify their properties, but they require significant manual labour and incur operator repeatability issues. In this study an automatic process is presented, aiming to segment all lower limb muscles from Magnetic Resonance (MR) imaging data simultaneously using three-dimensional (3D) deformable image registration (single inputs or multi-atlas). Twenty-three of the major lower limb skeletal muscles were segmented from five subjects, with an average Dice similarity coefficient of 0.72, and average absolute relative volume error (RVE) of 12.7% (average relative volume error of -2.2%) considering the optimal subject combinations. The multi-atlas approach showed slightly better accuracy (average DSC: 0.73; average RVE: 1.67%). Segmented MR imaging datasets of the lower limb are not widely available in the literature, limiting the potential of new, probabilistic methods such as deep learning to be used in the context of muscle segmentation. In this work, Non-linear deformable image registration is used to generate 69 manually checked, segmented, 3D, artificial datasets, allowing access for future studies to use these new methods, with a large amount of reliable reference data.

[A case of sporadic amyotrophic lateral sclerosis (ALS) with Senataxin (SETX) gene variant]

A 67-year-old man presented slowly progressive weakness of the extremities visited our hospital. Nerve conduction study showed axonal neuropathy and needle electromyography showed neurogenic changes with denervation findings in multiple limb muscles. While he was diagnosed as Probable amyotrophic lateral sclerosis (ALS), which is defined by the Awaji criteria for diagnosis of ALS, he did not develop either respiratory muscle paralysis or bulbar palsy, which are characteristic symptoms of sporadic ALS. Genetic testing revealed a novel gene variant in senataxin (SETX), the causative gene of ALS4. We could not make a definite diagnosis of ALS4 because he had no relatives who could perform genetic testing (segregation study). However, we considered the variant can be pathogenic because it was not previously reported and absent in at least 1,000 healthy control individuals, the variant site was highly conserved in mammals, and it may impair the function of senataxin protein (in silico analysis).

Whole-body muscle MRI in McArdle disease

This study describes muscle involvement on whole-body MRI (WB-MRI) scans at different stages of McArdle disease. WB-MRI was performed on fifteen genetically confirmed McArdle disease patients between ages 25 to 80. The degree of fatty substitution was scored for 60 muscles using Mercuri's classification. All patients reported an intolerance to exercise and episodes of rhabdomyolysis. A mild fixed muscle weakness was observed in 13/15 patients with neck flexor weakness in 7/15 cases, and proximal muscle weakness in 6/15 cases. A moderate scapular winging was observed in five patients. A careful review of the MRI scans, as well as hierarchical clustering of patients by Mercuri scores, pointed out recurrent muscle changes particularly in the subscapularis, anterior serratus, erector spinae and quadratus femoris muscles. WB-MRI imaging provides clinically relevant information and is a useful tool to orient toward the diagnosis of McArdle disease.

Lower Extremity Muscle Involvement in the Intermediate and Bethlem Myopathy Forms of COL6-Related Dystrophy and Duchenne Muscular Dystrophy: A Cross-Sectional Study

Collagen VI-related dystrophies (COL6-RDs) and Duchenne muscular dystrophy (DMD) cause progressive muscle weakness and disability. COL6-RDs are caused by mutations in the COL6 genes (COL6A1, COL6A2 and COL6A3) encoding the extracellular matrix protein collagen VI, and DMD is caused by mutations in the DMD gene encoding the cytoplasmic protein dystrophin. Both COL6-RDs and DMD are characterized by infiltration of the muscles by fatty and fibrotic tissue. This study examined the effect of disease pathology on skeletal muscles in lower extremity muscles of COL6-RDs using timed functional tests, strength measures and qualitative/ quantitative magnetic resonance imaging/spectroscopy measures (MRI/MRS) in comparison to unaffected (control) individuals. Patients with COL6-RD were also compared to age and gender matched patients with DMD.Patients with COL6-RD presented with a typical pattern of fatty infiltration of the muscle giving rise to an apparent halo effect around the muscle, while patients with DMD had evidence of fatty infiltration throughout the muscle areas imaged. Quantitatively, fat fraction, and transverse relaxation time (T2) were elevated in both COL6-RD and DMD patients compared to unaffected (control) individuals. Patients with COL6-RD had widespread muscle atrophy, likely contributing to weakness. In contrast, patients with DMD revealed force deficits even in muscle groups with increased contractile areas.

MR imaging of inherited myopathies: a review and proposal of imaging algorithms

PURPOSE OF REVIEW

The aims of this review are to discuss the imaging modalities used to assess muscle changes in myopathies, to provide an overview of the inherited myopathies focusing on their patterns of muscle involvement in magnetic resonance imaging (MR), and to propose up-to-date imaging-based diagnostic algorithms that can help in the diagnostic workup.

CONCLUSION

Familiarization with the most common and specific patterns of muscular involvement in inherited myopathies is very important for radiologists and neurologists, as imaging plays a significant role in diagnosis and follow-up of these patients.

KEY POINTS

• Imaging is an increasingly important tool for diagnosis and follow-up in the setting of inherited myopathies. • Knowledge of the most common imaging patterns of muscle involvement in inherited myopathies is valuable for both radiologists and neurologists. • In this review, we present imaging-based algorithms that can help in the diagnostic workup of myopathies.

Semi-Automatic MRI Muscle Volumetry to Diagnose and Monitor Hereditary and Acquired Polyneuropathies

With emerging treatment approaches, it is crucial to correctly diagnose and monitor hereditary and acquired polyneuropathies. This study aimed to assess the validity and accuracy of magnet resonance imaging (MRI)-based muscle volumetry.Using semi-automatic segmentations of upper- and lower leg muscles based on whole-body MRI and axial T1-weighted turbo spin-echo sequences, we compared and correlated muscle volumes, and clinical and neurophysiological parameters in demyelinating Charcot-Marie-Tooth disease (CMT) (n = 13), chronic inflammatory demyelinating polyneuropathy (CIDP) (n = 27), and other neuropathy (n = 17) patients.The muscle volumes of lower legs correlated with foot dorsiflexion strength (p < 0.0001), CMT Neuropathy Score 2 (p < 0.0001), early gait disorders (p = 0.0486), and in CIDP patients with tibial nerve conduction velocities (p = 0.0092). Lower (p = 0.0218) and upper (p = 0.0342) leg muscles were significantly larger in CIDP compared to CMT patients. At one-year follow-up (n = 15), leg muscle volumes showed no significant decrease.MRI muscle volumetry is a promising method to differentiate and characterize neuropathies in clinical practice.

Semi-automated volumetry of MRI serves as a biomarker in neuromuscular patients

BACKGROUND

Muscle MRI is of increasing importance for neuromuscular patients to detect changes in muscle volume, fat-infiltration, and edema. We developed a method for semi-automated segmentation of muscle MRI datasets.

METHODS

An active contour-evolution algorithm implemented within the ITK-SNAP software was used to segment T1-weighted MRI, and to quantify muscle volumes of neuromuscular patients (n = 65).

RESULTS

Semi-automated compared with manual segmentation was shown to be accurate and time-efficient. Muscle volumes and ratios of thigh/lower leg volume were lower in myopathy patients than in controls (P < .0001; P < .05). We found a decrease of lower leg muscle volume in neuropathy patients compared with controls (P < .01), which correlated with clinical parameters. In myopathy patients, muscle volume showed a positive correlation with muscle strength (r_left = 0.79, p_left  < .0001). Muscle volumes were independent of body mass index and age.

CONCLUSIONS

Our method allows for exact and time-efficient quantification of muscle volumes with possible use as a biomarker in neuromuscular patients.

Effectiveness of High-Speed T2-Corrected Multiecho MR Spectroscopic Method for Quantifying Thigh Muscle Fat Content in Boys With Duchenne Muscular Dystrophy

OBJECTIVE. The purpose of this study was to investigate the potential of high-speed T2-corrected multiecho (HISTO) MR spectroscopy (MRS) for rapidly quantifying the fat content of thigh muscles in children with Duchenne muscular dystrophy (DMD). SUBJECTS AND METHODS. This study prospectively enrolled 58 boys with DMD (mean age, 7.5 years; range, 4-11 years) and 30 age-matched healthy boys (mean age, 7.2 years; range, 4-11 years) at one institution over a 1-year period. T1- and T2-weighted, multiecho Dixon, and HISTO sequences were performed on the right adductor magnus and vastus lateralis muscles. The fat fractions of these muscles were acquired from HISTO and multiecho Dixon images. An experienced radiologist graded the degree of fat infiltration of the adductor magnus and vastus lateralis muscles on axial T1-weighted images. The Bland-Altman method was used to assess the consistency and repeatability of the HISTO sequence. Pearson linear correlation analysis was used to determine the correlation coefficient relating HISTO fat fraction to multiecho Dixon fat fraction values. Spearman rank correlation analysis was used to assess the relation between the HISTO fat fraction values and T1-weighted image fat infiltration grades. The independent t test was used to compare the HISTO fat fraction values of the boys with DMD with those of the healthy control subjects. RESULTS. Bland-Altman analysis showed that 95.5% of the HISTO fat fraction values of the adductor magnus were within the 95% CI. HISTO fat fraction and multiecho Dixon fat fraction values of the adductor magnus and vastus lateralis muscles were highly positively correlated (adductor magnus, r = 0.983; vastus lateralis, r = 0.967; p < 0.0001). HISTO fat fraction values were also highly positively correlated with the grades of fat infiltration on T1-weighted images (adductor magnus, r = 0.911; vastus lateralis, r = 0.937; p < 0.0001). The HISTO fat fraction of the adductor magnus muscle was 33.3% ± 22.6% and of the vastus lateralis muscle was 25.6% ± 20.3% in patients with DMD. The corresponding values were 2.9% ± 2.1% and 2.3% ± 1.9% in the control group. The differences were statistically significant (p < 0.0001). CONCLUSION. The HISTO sequence is a rapid and feasible noninvasive MRS technique for quantifying the fat infiltration of thigh muscles in children with known or suspected DMD. It is useful for diagnosis and for assessment of disease activity and prognosis.

Lower extremity muscle pathology in myotonic dystrophy type 1 assessed by quantitative MRI

Objective

To determine the value of quantitative MRI in providing imaging biomarkers for disease in 20 different upper and lower leg muscles of patients with myotonic dystrophy type 1 (DM1).

Methods

We acquired images covering these muscles in 33 genetically and clinically well-characterized patients with DM1 and 10 unaffected controls. MRIs were recorded with a Dixon method to determine muscle fat fraction, muscle volume, and contractile muscle volume, and a multi-echo spin-echo sequence was used to determine T2 water relaxation time (T2_water), reflecting putative edema.

Results

Muscles in patients with DM1 had higher fat fractions than muscles of controls (15.6 ± 11.1% vs 3.7 ± 1.5%). In addition, patients had smaller muscle volumes (902 ± 232 vs 1,097 ± 251 cm³), smaller contractile muscle volumes (779 ± 247 vs 1,054 ± 246 cm³), and increased T2_water (33.4 ± 1.0 vs 31.9 ± 0.6 milliseconds), indicating atrophy and edema, respectively. Lower leg muscles were affected most frequently, especially the gastrocnemius medialis and soleus. Distribution of fat content per muscle indicated gradual fat infiltration in DM1. Between-patient variation in fat fraction was explained by age (≈45%), and another ≈14% was explained by estimated progenitor CTG repeat length (r² = 0.485) and somatic instability (r² = 0.590). Fat fraction correlated with the 6-minute walk test (r = −0.553) and muscular impairment rating scale (r = 0.537) and revealed subclinical muscle involvement.

Conclusion

This cross-sectional quantitative MRI study of 20 different lower extremity muscles in patients with DM1 revealed abnormal values for muscle fat fraction, volume, and T2_water, which therefore may serve as objective biomarkers to assess disease state of skeletal muscles in these patients.

ClinicalTrials.gov identifier

NCT02118779.

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.

Diagnostic Imaging of Inflammatory Myopathies: New Concepts and a Radiological Approach

PURPOSE OF REVIEW

The purpose of this review article is to highlight the current role of diagnostic imaging in the assessment of inflammatory myopathies.

RECENT FINDINGS

Recent research demonstrates that imaging plays an important role in evaluating patients with symptoms of an inflammatory myopathy. In general, MRI is the pivotal imaging modality for assessing inflammatory myopathies, revealing precise anatomic details because of changes in the signal intensity of the muscles. Whole-body MR imaging has become increasingly important over the last several years. US is also a valuable imaging modality for scanning muscles. Together with the clinical history, familiarity with the imaging features of inflammatory myopathies is essential for formulating an accurate diagnosis.

Imaging in the diagnosis of idiopathic inflammatory myopathies; indications and utility

INTRODUCTION

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of muscle diseases that carry a significant morbidity and mortality risk. The utilization of imaging in the diagnostic pathway of IIM is therefore important to obtain early diagnosis and even monitor patients over time. Areas covered: Magnetic resonance imaging (MRI) has been the main imaging modality used to detect myositis but limitations include cost and accessibility, leading to delays in time to scan, and patient contraindications. This has led to the exploration of other imaging techniques to diagnose and monitor response to therapy. This article is based primarily on a literature search via PubMed using Boolean terms 'myositis' and the various imaging modalities. Expert opinion: Imaging is sensitive to pathology in IIM and may contribute to the diagnostic process. Learning how specific imaging features can distinguish different forms of IIM may allow more rapid diagnosis of myositis subtype and treatment planning, and to monitor disease activity particularly in patients who respond poorly to treatment. However, more work is needed to investigate the validity and relative utility of these imaging modalities.

Texture Analysis for Muscular Dystrophy Classification in MRI with Improved Class Activation Mapping

The muscular dystrophies are made up of a diverse group of rare genetic diseases characterized by progressive loss of muscle strength and muscle damage. Since there is no cure for muscular dystrophy and clinical outcome measures are limited, it is critical to assess the progression of MD objectively. Imaging muscle replacement by fibrofatty tissue has been shown to be a robust biomarker to monitor disease progression in DMD. In magnetic resonance imaging (MRI) data, specific texture patterns are found to correlate to certain MD subtypes and thus present a potential way for automatic assessment. In this paper, we first apply state-of-the-art convolutional neural networks (CNNs) to perform accurate MD image classification and then propose an effective visualization method to highlight the important image textures. With a dystrophic MRI dataset, we found that the best CNN model delivers an 91.7% classification accuracy, which significantly outperforms non-deep learning methods, e.g., >40% improvement has been found over the traditional mean fat fraction (MFF) criterion for DMD and CMD classification. After investigating every single neuron at the top layer of CNN model, we found the superior classification ability of CNN can be explained by its 91 and 118 neurons were performing better than the MFF criterion under the measurements of Euclidean and Chi-square distance, respectively. In order to further interpret CNNs predictions, we tested an improved class activation mapping (ICAM) method to visualize the important regions in the MRI images. With this ICAM, CNNs are able to locate the most discriminative texture patterns of DMD in soleus, lateral gastrocnemius, and medial gastrocnemius; for CMD, the critical texture patterns are highlighted in soleus, tibialis posterior, and peroneus.

Detecting Toxic Myopathies as Medication Side Effect

The goal of this article is to provide physiatrists, neurologists, and neuromuscular medicine physicians a framework that can be easily used in the process of evaluating, identifying, and treating patients with toxic myopathies. This review attempts to classify these rare but potentially deadly conditions in clinical patterns and distinguishes the cellular mechanisms in which the offending agents tend to impact the structure and function of myocytes.

In vivo measurement of membrane permeability and myofiber size in human muscle using time-dependent diffusion tensor imaging and the random permeable barrier model

The time dependence of the diffusion coefficient is a hallmark of tissue complexity at the micrometer level. Here we demonstrate how biophysical modeling, combined with a specifically tailored diffusion MRI acquisition performing diffusion tensor imaging (DTI) for varying diffusion times, can be used to determine fiber size and membrane permeability of muscle fibers in vivo. We describe the random permeable barrier model (RPBM) and its assumptions, as well as the details of stimulated echo DTI acquisition, signal processing steps, and potential pitfalls. We illustrate the RPBM method on a few pilot examples involving human subjects (previously published as well as new), such as revealing myofiber size derived from RPBM increase after training in a calf muscle, and size decrease with atrophy in shoulder rotator cuff muscle. Finally, we comment on the potential clinical relevance of our results. Copyright © 2016 John Wiley & Sons, Ltd.

Ultrasound in the Assessment of Myopathic Disorders

Neuromuscular ultrasound (US) augments a careful physical examination and electrodiagnostic evaluation in the evaluation of suspected myopathy. Ultrasound evaluation of muscle can identify abnormal echo intensity, size, and movement. Because it is painless and noninvasive, US can be used to evaluate multiple muscles to direct the electrodiagnostic examination or muscle biopsy. Some patterns of muscle involvement can suggest specific etiologies. Most muscular dystrophies show homogenously increased muscle echo intensity with attenuation of the US signal, likely resultant from increased intramuscular fat and fibrosis. Inflammatory myopathies can also show homogenously increased echogenicity but lack the signal attenuation seen in muscular dystrophies. In contrast, denervation can show "moth-eaten," atrophic muscles with fasciculations. Advanced age and obesity also impacts muscle size and echo intensity and can hamper efforts to detect mild pathologies. The sensitivity and specificity of US for detecting neuromuscular disease have been best studied in children and depend on the type and severity of the disorder. In general, muscle US yields sensitivities and specificities of 67% to 100% for detecting neuromuscular disorders in children and is similar to electromyogram for detection of myopathy. Ultrasound is most sensitive for detecting muscular dystrophies and is less sensitive in metabolic myopathies and very young children.

MRI as outcome measure in facioscapulohumeral muscular dystrophy: 1-year follow-up of 45 patients

There is no effective treatment available for facioscapulohumeral muscular dystrophy type 1 (FSHD1), but emerging therapies are under way that call for a better understanding of natural history in this condition. In this prospective, longitudinal study, we used quantitative MRI to assess yearly disease progression in patients with FSHD1. Ambulatory patients with confirmed diagnosis of FSHD1 (25/20 men/women, age 20-75 years, FSHD score: 0-12) were tested with 359-560-day interval between tests. Using the MRI Dixon technique, muscle fat replacement was evaluated in paraspinal, thigh, and calf muscles. Changes were compared with those in FSHD score, muscle strength (hand-held dynamometry), 6-minute-walk-distance, 14-step-stair-test, and 5-time-sit-to-stand-test. Composite absolute fat fraction of all assessed muscles increased by 0.036 (CI 0.026-0.046, P < 0.001), with increases in all measured muscle groups. The clinical severity FSHD score worsened (10%, P < 0.05), muscle strength decreased over the hip (8%), neck (8%), and back (17%) (P < 0.05), but other strength measures, 6-minute-walk-distance, 5-times-sit-to-stand-test, and 14-step-stair-test were unchanged. Changes in muscle strength, FSHD score, and fat fraction did not correlate. This first study to systemically monitor quantitative fat replacement longitudinally in FSHD1 shows that MRI provides an objective measure of disease progression, often before changes can be appreciated in strength and functional tests. The study indicates that quantitative MRI can be a helpful end-point in follow-up and therapeutic trials of patients with FSHD1.

Muscle MRI of facioscapulohumeral dystrophy (FSHD): A growing demand and a promising approach

Facioscapulohumeral muscular dystrophy (FSHD), an inherited and progressive muscle disorder, is among the most common hereditary muscle disorders. From a clinical vantage point, FSHD is characterized by weakness of the facial, shoulder (often with scapular winging), arm (including biceps and triceps) and abdominal muscles. Forearm muscles are usually spared and weakness is usually asymmetrical. Over the past few decades, muscle magnetic resonance imaging (MRI) has become established as a reliable and accurate noninvasive tool for the diagnosis and assessment of progression in neuromuscular diseases, showing specific patterns of muscle involvement for a number of myopathies. More recently, MRI has been used to noninvasively identify quantitative biomarkers, allowing evaluation of the natural progression of disease and assessment of therapeutic interventions. In the present review, the intention was to present the most significant MRI developments related to diagnosis and pattern recognition in FSHD and to discuss its capacity to provide outcome measures.

Quantitative Skeletal Muscle MRI: Part 1, Derived T2 Fat Map in Differentiation Between Boys With Duchenne Muscular Dystrophy and Healthy Boys

OBJECTIVE

The purpose of this study was to validate derived T2 maps as an objective measure of muscular fat for discrimination between boys with Duchenne muscular dystrophy (DMD) and healthy boys.

SUBJECTS AND METHODS

Forty-two boys with DMD (mean age, 9.9 years) and 31 healthy boys (mean age, 11.4 years) were included in the study. Age, body mass index, and clinical function scale grade were evaluated. T1-weighted MR images and T2 maps with and without fat suppression were obtained. Fatty infiltration was graded 0-4 on T1-weighted images, and derived T2 fat values (difference between mean T2 values from T2 maps with and without fat suppression) of the gluteus maximus and vastus lateralis muscles were calculated. Group comparisons were performed. The upper limit of the 95% reference interval of T2 fat values from the control group was applied.

RESULTS

There was no significant difference in age or body mass index between groups. All healthy boys and 19 boys (45.2%) with DMD had a normal clinical function scale grade. Grade 1 fatty infiltration was seen in 90.3% (gluteus maximus) and 71.0% (vastus lateralis) of healthy boys versus 33.3% (gluteus maximus) and 52.4% (vastus lateralis) of boys with DMD. T2 fat values of boys with DMD were significantly longer than in the control group (p < 0.001). Using a 95% reference interval for healthy boys for the gluteus maximus (28.3 milliseconds) allowed complete separation from boys with DMD (100% sensitivity, 100% specificity), whereas the values for the vastus lateralis (7.28 milliseconds) resulted in 83.3% sensitivity and 100% specificity.

CONCLUSION

Measurement of muscular fat with T2 maps is accurate for differentiating boys with DMD from healthy boys.

Muscle Quantitative MR Imaging and Clustering Analysis in Patients with Facioscapulohumeral Muscular Dystrophy Type 1

BACKGROUND

Facioscapulohumeral muscular dystrophy type 1 (FSHD1) is the third most common inherited muscular dystrophy. Considering the highly variable clinical expression and the slow disease progression, sensitive outcome measures would be of interest.

METHODS AND FINDINGS

Using muscle MRI, we assessed muscular fatty infiltration in the lower limbs of 35 FSHD1 patients and 22 healthy volunteers by two methods: a quantitative imaging (qMRI) combined with a dedicated automated segmentation method performed on both thighs and a standard T1-weighted four-point visual scale (visual score) on thighs and legs. Each patient had a clinical evaluation including manual muscular testing, Clinical Severity Score (CSS) scale and MFM scale. The intramuscular fat fraction measured using qMRI in the thighs was significantly higher in patients (21.9 ± 20.4%) than in volunteers (3.6 ± 2.8%) (p<0.001). In patients, the intramuscular fat fraction was significantly correlated with the muscular fatty infiltration in the thighs evaluated by the mean visual score (p<0.001). However, we observed a ceiling effect of the visual score for patients with a severe fatty infiltration clearly indicating the larger accuracy of the qMRI approach. Mean intramuscular fat fraction was significantly correlated with CSS scale (p ≤ 0.01) and was inversely correlated with MMT score, MFM subscore D1 (p ≤ 0.01) further illustrating the sensitivity of the qMRI approach. Overall, a clustering analysis disclosed three different imaging patterns of muscle involvement for the thighs and the legs which could be related to different stages of the disease and put forth muscles which could be of interest for a subtle investigation of the disease progression and/or the efficiency of any therapeutic strategy.

CONCLUSION

The qMRI provides a sensitive measurement of fat fraction which should also be of high interest to assess disease progression and any therapeutic strategy in FSHD1 patients.

Gait propulsion in patients with facioscapulohumeral muscular dystrophy and ankle plantarflexor weakness

Facioscapulohumeral muscular dystrophy is a slowly progressive hereditary disorder resulting in fatty infiltration of eventually most skeletal muscles. Weakness of trunk and leg muscles causes problems with postural balance and gait, and is associated with an increased fall risk. Although drop foot and related tripping are common problems in FSHD, gait impairments are poorly documented. The effect of ankle plantarflexor involvement on gait propulsion has never been addressed. In addition to ankle plantarflexion, gait propulsion is generated through hip flexion and hip extension. Compensatory shifts between these propulsion sources occur when specific muscles are affected. Such a shift may be expected in patients with FSHD since the calves may show early fatty infiltration, whereas iliopsoas and gluteus maximus muscles are often spared for a longer time. In the current study, magnetic resonance imaging was used to assess the percentage of unaffected calf, iliopsoas and gluteus maximus muscles. Joint powers were analyzed in 10 patients with FSHD at comfortable and maximum walking speed to determine the contribution of ankle plantarflexor, hip flexor and hip extensor power to propulsion. Associations between muscle morphology, power generation and gait speed were assessed. Based on multivariate regression analysis, ankle plantarflexor power was the only factor that uniquely contributed to the explained variance of comfortable (R(2)=80%) and maximum (R(2)=86%) walking speed. Although the iliopsoas muscles were largely unaffected, they appeared to be sub-maximally recruited. This submaximal recruitment may be related to poor trunk stability, resulting in a disproportionate effect of calf muscle affliction on gait speed in patients with FSHD.

Magnetic resonance imaging phenotyping of Becker muscular dystrophy

INTRODUCTION

There is little information on magnetic resonance imaging (MRI) phenotypes of Becker muscular dystrophy (BMD). This study presents the MRI phenotyping of the upper and lower extremities of a large cohort of BMD patients.

METHODS

In this retrospective study, MRI images of 33 BMD subjects were evaluated for severity, distribution, and symmetry of involvement.

RESULTS

Teres major, triceps long head, biceps brachii long head, gluteus maximus, gluteus medius, vasti, adductor longus, adductor magnus, semitendinosus, semimembranosus, and biceps femoris muscles showed the highest severity and frequency of involvement. All analyzed muscles had a high frequency of symmetric involvement. There was significant variability of involvement between muscles within some muscle groups, most notably the arm abductors, posterior arm muscles, medial thigh muscles, and lateral hip rotators.

CONCLUSIONS

This study showed a distinctive pattern of involvement of extremity muscles in BMD subjects.

Diffusion tensor imaging in evaluation of thigh muscles in patients with polymyositis and dermatomyositis

OBJECTIVE

To explore the diffusion tensor imaging (DTI) characteristics of thigh muscles in patients with polymyositis (PM) and dermatomyositis (DM).

METHODS

12 patients with known PM/DM and 10 healthy volunteers were enrolled in this study. Both DTI and conventional MR sequences were performed on both thighs of all subjects. Apparent diffusion coefficient (ADC), fractional anisotropy (FA) and three eigenvalues were compared between the PM/DM group and the healthy group. One-way analysis of variance and Student's t-test were used for statistical analyses with a significance of p < 0.05.

RESULTS

In the healthy group, the vastus intermedius muscle showed the highest ADC value and the gracilis (GA) muscle showed the lowest ADC value. These results were statistically significant when compared with other muscles (p < 0.05). The GA, semi-tendinosus and semi-membranosus muscles showed higher FA values than the other three thigh muscles (p < 0.05). The mean ADC value and three eigenvalues of oedematous muscles in the PM/DM group were higher on average and showed a statistically significant difference when compared with unaffected (non-oedematous muscles in patients) and normal muscles (p < 0.05). There was no statistical difference in the mean FA value between oedematous and normal muscles. The mean ADC, FA and three eigenvalues in unaffected muscles (in patients) showed no statistical differences from those in normal muscles (p > 0.05).

CONCLUSION

DTI can be used to quantitatively evaluate the anisotropic diffusion characteristics of muscles in patients with PM/DM.

ADVANCES IN KNOWLEDGE

A new application of DTI is proposed for inflammatory myopathies. The results show that ADC and the three eigenvalues were significantly different between diseased and normal muscles, a finding of potential value in both diagnosis and treatment monitoring of myopathies.

Influence of immune responses in gene/stem cell therapies for muscular dystrophies

Muscular dystrophies (MDs) are a heterogeneous group of diseases, caused by mutations in different components of sarcolemma, extracellular matrix, or enzymes. Inflammation and innate or adaptive immune response activation are prominent features of MDs. Various therapies under development are directed toward rescuing the dystrophic muscle damage using gene transfer or cell therapy. Here we discussed current knowledge about involvement of immune system responses to experimental therapies in MDs.

Quantitative magnetic resonance imaging in limb-girdle muscular dystrophy 2I: a multinational cross-sectional study

We conducted a prospective multinational study of muscle pathology using magnetic resonance imaging (MRI) in patients with limb-girdle muscular dystrophy 2I (LGMD2I). Thirty eight adult ambulant LGMD2I patients (19 male; 19 female) with genetically identical mutations (c.826C>A) in the fukutin-related protein (FKRP) gene were recruited. In each patient, T1-weighted (T₁w) imaging was assessed by qualitative grading for 15 individual lower limb muscles and quantitative Dixon imaging was analysed on 14 individual lower limb muscles by region of interest analysis. We described the pattern and appearance of muscle pathology and gender differences, not previously reported for LGMD2I. Diffuse fat infiltration of the gastrocnemii muscles was demonstrated in females, whereas in males fat infiltration was more prominent in the medial than the lateral gastrocnemius (p = 0.05). In the anterior thigh of males, in contrast to females, median fat infiltration in the vastus medialis muscle (45.7%) exceeded that in the vastus lateralis muscle (11.2%) (p<0.005). MRI is non-invasive, objective and does not rely on patient effort compared to clinical and physical measures that are currently employed. We demonstrated (i) that the quantitative Dixon technique is an objective quantitative marker of disease and (ii) new observations of gender specific patterns of muscle involvement in LGMD2I.

Distinct disease phases in muscles of facioscapulohumeral dystrophy patients identified by MR detected fat infiltration

Facioscapulohumeral muscular dystrophy (FSHD) is an untreatable disease, characterized by asymmetric progressive weakness of skeletal muscle with fatty infiltration. Although the main genetic defect has been uncovered, the downstream mechanisms causing FSHD are not understood. The objective of this study was to determine natural disease state and progression in muscles of FSHD patients and to establish diagnostic biomarkers by quantitative MRI of fat infiltration and phosphorylated metabolites. MRI was performed at 3T with dedicated coils on legs of 41 patients (28 men/13 women, age 34-76 years), of which eleven were re-examined after four months of usual care. Muscular fat fraction was determined with multi spin-echo and T1 weighted MRI, edema by TIRM and phosphorylated metabolites by 3D (31)P MR spectroscopic imaging. Fat fractions were compared to clinical severity, muscle force, age, edema and phosphocreatine (PCr)/ATP. Longitudinal intramuscular fat fraction variation was analyzed by linear regression. Increased intramuscular fat correlated with age (p<0.05), FSHD severity score (p<0.0001), inversely with muscle strength (p<0.0001), and also occurred sub-clinically. Muscles were nearly dichotomously divided in those with high and with low fat fraction, with only 13% having an intermediate fat fraction. The intramuscular fat fraction along the muscle's length, increased from proximal to distal. This fat gradient was the steepest for intermediate fat infiltrated muscles (0.07±0.01/cm, p<0.001). Leg muscles in this intermediate phase showed a decreased PCr/ATP (p<0.05) and the fastest increase in fatty infiltration over time (0.18±0.15/year, p<0.001), which correlated with initial edema (p<0.01), if present. Thus, in the MR assessment of fat infiltration as biomarker for diseased muscles, the intramuscular fat distribution needs to be taken into account. Our results indicate that healthy individual leg muscles become diseased by entering a progressive phase with distal fat infiltration and altered energy metabolite levels. Fat replacement then relatively rapidly spreads over the whole muscle.

Analysis of fatty infiltration and inflammation of the pelvic and thigh muscles in boys with Duchenne muscular dystrophy (DMD): grading of disease involvement on MR imaging and correlation with clinical assessments

BACKGROUND

Prior reports focus primarily on muscle fatty infiltration in Duchenne muscular dystrophy (DMD). However, the significance of muscle edema is uncertain.

OBJECTIVE

To evaluate the frequency and degree of muscle fat and edema, and correlate these with clinical function.

MATERIALS AND METHODS

Forty-two boys (ages 5-19 years) with DMD underwent pelvic MRI. Axial T1- and fat-suppressed T2-weighted images were evaluated to grade muscle fatty infiltration (0-4) and edema (0-3), respectively. Degree and frequency of disease involvement were compared to clinical evaluations.

RESULTS

Gluteus maximus had the greatest mean fatty infiltration score, followed by adductor magnus and gluteus medius muscles, and had the most frequent and greatest degree of fatty infiltration. Gluteus maximus also had the greatest mean edema score, followed by vastus lateralis and gluteus medius muscles. These muscles had the most frequent edema, although the greatest degree of edema was seen in other muscles. There was correlation between cumulative scores of fatty infiltration and all clinical evaluations (P < 0.05).

CONCLUSION

In DMD, the muscles with the most frequent fatty infiltration had the greatest degree of fatty infiltration and correlated with patient function. However, the muscles with the most frequent edema were different from those with the greatest degree of edema. Thus, edema may not predict patient functional status.

Quantitative muscle MRI as an assessment tool for monitoring disease progression in LGMD2I: a multicentre longitudinal study

BACKGROUND

Outcome measures for clinical trials in neuromuscular diseases are typically based on physical assessments which are dependent on patient effort, combine the effort of different muscle groups, and may not be sensitive to progression over short trial periods in slow-progressing diseases. We hypothesised that quantitative fat imaging by MRI (Dixon technique) could provide more discriminating quantitative, patient-independent measurements of the progress of muscle fat replacement within individual muscle groups.

OBJECTIVE

To determine whether quantitative fat imaging could measure disease progression in a cohort of limb-girdle muscular dystrophy 2I (LGMD2I) patients over a 12 month period.

METHODS

32 adult patients (17 male;15 female) from 4 European tertiary referral centres with the homozygous c.826C>A mutation in the fukutin-related protein gene (FKRP) completed baseline and follow up measurements 12 months later. Quantitative fat imaging was performed and muscle fat fraction change was compared with (i) muscle strength and function assessed using standardized physical tests and (ii) standard T1-weighted MRI graded on a 6 point scale.

RESULTS

There was a significant increase in muscle fat fraction in 9 of the 14 muscles analyzed using the quantitative MRI technique from baseline to 12 months follow up. Changes were not seen in the conventional longitudinal physical assessments or in qualitative scoring of the T₁w images.

CONCLUSIONS

Quantitative muscle MRI, using the Dixon technique, could be used as an important longitudinal outcome measure to assess muscle pathology and monitor therapeutic efficacy in patients with LGMD2I.

A novel MYH7 mutation with prominent paraspinal and proximal muscle involvement

Laing distal myopathy (LDM) is caused by mutations in the MYH7 gene, and known to have muscle weakness of distal limbs and neck flexors. Through whole exome sequencing, we identified a novel p.Ala1439Pro MYH7 mutation in a Korean LDM family. This missense mutation is located in more N-terminal than any reported rod domain LDM mutations. In the early stage of disease, the present patients showed similar clinical patterns to the previously described patients of LDM. However, in the later stage, fatty replacement and atrophy of paraspinal or proximal leg muscles was more severely marked than lower leg muscles, and asymmetric atrophies were observed in trapezius, subscapularis and adductor magnus muscles. Distal myopathy like LDM showed marked and predominant fatty infiltrations in paraspinal or proximal leg muscles with marked asymmetry. These observations expand the clinical spectrum of LDM with the MYH7 mutation.

Myotonic dystrophy type 1 and de novo FSHD mutation double trouble: a clinical and muscle MRI study

Here we describe the first case of myotonic dystrophy type 1 (DM1) associated with facio-scapulo-humeral dystrophy (FSHD). From a clinical point of view, the patient displayed a pattern of muscle involvement reminiscent of both disorders, including hand-grip myotonia, facial, axial and distal limbs muscle weakness as well as a bilateral winged scapula associated with atrophy of the pectoralis major muscle and lumbar lordosis; pelvic muscles were mostly spared. An extensive muscle MRI assessment including neck, shoulder, abdominal, pelvic and lower limb muscles documented radiological features typical of DM1 and FSDH. Molecular genetic studies confirmed that the proband carried both a pathologically expanded DMPK allele, inherited from his father, and a de novo shortened D4Z4 repeat fragment at 4q35 locus.

Whole-Body muscle MRI in a series of patients with congenital myopathy related to TPM2 gene mutations

Beta-tropomyosin 2 (TPM2) gene mutations are a rare cause of congenital myopathy with variable clinical and histological features. We describe muscle involvement using Whole-Body muscle Magnetic Resonance Imaging (WBMRI) in 8 individuals with genetically proven TPM2 mutations and different clinical and histological features (nemaline myopathy, 'cap disease', Bethlem-like phenotype, arthrogryposis). Most patients shared a recognizable MRI pattern with the involvement of masticatory and distal lower leg muscles. The lower leg showed constant soleus muscle involvement, and often also involvement of peroneus, tibialis anterior, and toe flexor muscles. Pelvic and shoulder girdles, and upper limbs muscles were quite spared. Two adult subjects (a patient and a paucisymptomatic parent) had a more diffuse involvement with striking fat infiltration of the rectus femoris muscle. Two children showed variant findings: one presented with masseter involvement associated with severe axial fat infiltration, the second had masticatory and distal leg muscle involvement (soleus and gastrocnemius muscles). Our study suggests that, independently of the clinical and histological presentation, most patients with TPM2 mutations show a predominant involvement of masticatory and distal leg muscles with the other regions relatively spared. More spread involvement may be observed. This cephalic-distal MRI pattern is not frequent in other known myopathies.

Skeletal muscle disease: patterns of MRI appearances

Although the presumptive diagnosis of skeletal muscle disease (myopathy) may be made on the basis of clinical-radiological correlation in many cases, muscle biopsy remains the cornerstone of diagnosis. Myopathy is suspected when patients complain that the involved muscle is painful and tender, when they experience difficulty performing tasks that require muscle strength or when they develop various systemic manifestations. Because the cause of musculoskeletal pain may be difficult to determine clinically in many cases, MRI is increasingly utilised to assess the anatomical location, extent and severity of several pathological conditions affecting muscle. Infectious, inflammatory, traumatic, neurological, neoplastic and iatrogenic conditions can cause abnormal signal intensity on MRI. Although diverse, some diseases have similar MRI appearances, whereas others present distinct patterns of signal intensity abnormality. In general, alterations in muscle signal intensity fall into one of three cardinal patterns: muscle oedema, fatty infiltration and mass lesion. Because some of the muscular disorders may require medical or surgical treatment, correct diagnosis is essential. In this regard, MRI features, when correlated with clinical and laboratory findings as well as findings from other methods such as electromyography, may facilitate correct diagnosis. This article will review and illustrate the spectrum of MRI appearances in several primary and systemic disorders affecting muscle, both common and uncommon. The aim of this article is to provide radiologists and clinicians with a collective, yet succinct and useful, guide to a wide array of myopathies.

Muscle fat-fraction and mapping in Duchenne muscular dystrophy: evaluation of disease distribution and correlation with clinical assessments. Preliminary experience

PURPOSE

To examine the usefulness of dual-echo dual-flip angle spoiled gradient recalled (SPGR) magnetic resonance imaging (MRI) technique in quantifying muscle fat fraction (MFF) of pelvic and thighs muscles as a marker of disease severity in boys with Duchenne muscular dystrophy (DMD), by correlating MFF calculation with clinical assessments. We also tried to identify characteristic patterns of disease distribution.

MATERIALS AND METHODS

Twenty consecutive boys (mean age, 8.6 years ± 2.3 [standard deviation, SD]; age range, 5-15 years; median age, 9 years;) with DMD were evaluated using a dual-echo dual-flip angle SPGR MRI technique, calculating muscle fat fraction (MFF) of eight muscles in the pelvic girdle and thigh (gluteus maximus, adductor magnus, rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, and gracilis). Color-coded parametric maps of MFF were also obtained. A neurologist who was blinded to the MRI findings performed the clinical assessments (patient age, Medical Research Council score, timed Gower score, time to run 10 m). The relationships between mean MFF and clinical assessments were investigated using Spearman's rho coefficient. Positive and negative correlations were evaluated and considered significant if the P value was < 0.05.

RESULTS

The highest mean MFF was found in the gluteus maximus (mean, 46.3 % ± 24.5 SD), whereas the lowest was found in the gracilis muscle (mean, 2.7 % ± 4.7 SD). Mean MFF of the gluteus maximus was significantly higher than that of the other muscles (P < 0.01), except for the adductor magnus and biceps muscles. A significant positive correlation was found between the mean MFF of all muscles and the patients age (20 patients; P < 0.005), Medical Research Council score (19 patients; P < 0.001), timed Gower score (17 patients; P < 0.03), and time to run 10 m (20 patients; P < 0.001). A positive correlation was also found between the mean MFF of the gluteus maximus muscle and the timed Gower score. Color-coded maps provided an efficient visual assessment of muscle fat content and its heterogeneous distribution.

CONCLUSION

Muscle fat fraction calculation and mapping using the dual-echo dual-flip angle SPGR MRI technique are useful markers of disease severity and permit patterns of disease distribution to be identified in patients with DMD.

Lower leg muscle involvement in Duchenne muscular dystrophy: an MR imaging and spectroscopy study

OBJECTIVE

To describe the involvement of lower leg muscles in boys with Duchenne muscular dystrophy (DMD) by using MR imaging (MRI) and spectroscopy (MRS) correlated to indices of functional status.

SUBJECTS AND METHODS

Nine boys with DMD (mean age, 11 years) and eight healthy age- and BMI-matched boys (mean age, 13 years) prospectively underwent lower leg MRI, 1H-MRS of tibialis anterior (TA) and soleus (SOL) for lipid fraction measures, and 31P-MRS for pH and high-energy phosphate measures. DMD subjects were evaluated using the Vignos lower extremity functional rating, and tests including 6 min walk test (6MWT) and 10 m walk.

RESULTS

DMD subjects had highest fatty infiltration scores in peroneal muscles, followed by medial gastrocnemius and soleus. Compared to controls, DMD boys showed higher intramuscular fat (P = 0.04), lipid fractions of TA and SOL (P = 0.02 and 0.003, respectively), pH of anterior compartment (P = 0.0003), and lower phosphocreatine/inorganic phosphorus ratio of posterior compartment (P = 0.02). The Vignos rating correlated with TA (r = 0.79, P = 0.01) and SOL (r = 0.71, P = 0.03) lipid fractions. The 6MWT correlated with fatty infiltration scores of SOL (r = -0.76, P = 0.046), medial (r = -0.80, P = 0.03) and lateral (r = -0.84, P = 0.02) gastrocnemius, intramuscular fat (r = -0.80, P = 0.03), and SOL lipid fraction (r = -0.89, P = 0.007). Time to walk 10 m correlated with anterior compartment pH (r = 0.78, P = 0.04).

CONCLUSION

Lower leg muscles of boys with DMD show a distinct involvement pattern and increased adiposity that correlates with functional status. Lower leg MRI and 1H-MRS studies may help to noninvasively demonstrate the severity of muscle involvement.

Use of skeletal muscle MRI in diagnosis and monitoring disease progression in Duchenne muscular dystrophy

Studies have shown promise in using various approaches of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy to evaluate skeletal muscle involvement in Duchenne muscular dystrophy. However, these studies have mainly been performed using a cross-sectional design, and the correlation of these MRI changes with disease progression and disease severity has not been fully elucidated. Overall, skeletal muscle MRI is a powerful and sensitive technique in the evaluation of muscle disease, and its use as a biomarker for disease progression or therapeutic response in clinical trials deserves further study.

Quantitative assessment of skeletal muscle degeneration in patients with myotonic dystrophy type 1 using MRI

PURPOSE

To identify MRI biomarkers that could be used to follow disease progression and therapeutic efficacy in one individual muscle in patients with myotonic dystrophy type 1 (DM1).

MATERIALS AND METHODS

Lower limb MRI and maximal ankle dorsiflexor strength assessment, using a hand-held dynamometer, were performed in 19 DM1 patients and 6 control subjects. The volume of residual muscle tissue of Tibialis Anterior (TA) muscle was chosen as an index for muscle atrophy, and the T2-relaxation-time of the residual muscle tissue was measured to evaluate edema-like lesions. The fat-to-water ratio was assessed using three-point Dixon images to quantify fat infiltration in the entire muscle.

RESULTS

The intra-observer variability of MRI indices (∼5.2% for the residual muscle tissue volume and 2.5% for the fat-to-water ratio) was lower than that of the dorsiflexor torque measurement (∼11.5%). A high correlation (r = 0.91) was found between maximal ankle dorsiflexor strength and residual TA muscle tissue volume in DM1 patients. Increases in the fat-to-water ratio and T2-relaxation-time were associated with a decrease in maximal ankle dorsiflexor strength.

CONCLUSION

MRI appears as a noninvasive method which can be used to follow disease progression and therapeutic efficacy.

Cardiac and muscle imaging findings in a family with X-linked Emery-Dreifuss muscular dystrophy

The following is a report on a large family with 5 males affected by the X-linked recessive form of Emery-Dreifuss muscular dystrophy with mutation in the STA gene. A detailed longitudinal cardiological evaluation and muscle imaging studies allowed for the assessment of intrafamilial variability of cardiac and muscle involvement. Long term cardiological follow up in the 5 affected males and in 7 female carriers revealed different degrees of severity, ranging from tachycardia-bradycardia syndrome and variable biatrial and left ventricle dilatation, to an episode of isolated symptomatic sustained ventricular tachycardia requiring a device implantation. Muscle imaging in the affected males showed involvement of the soleus and medial head of gastrocnemius on leg muscles and variable involvement on thigh muscles that have not been previously reported. In some cases, imaging showed clear signs of muscle involvement even when no overt signs of weakness could be detected during clinical examination.

[Role of MRI in the diagnosis of neuromuscular disorders]

Recently, the assessment of the muscles using limb MRI and whole body MRI has become widely available and more frequent. In cases of muscular dystrophies it may help to select the optimal muscles for biopsy, because the severely atrophic and degenerated muscles are not suitable for histological tests. It is also known that the pattern of muscle involvement is characteristic for a certain neuromuscular disease, and clinically silent muscle damage can be visualized, as well. Therefore, imaging of muscles is helpful in neuromuscular differential diagnosis and planning genetic tests.

Quantification of fat infiltration in oculopharyngeal muscular dystrophy: comparison of three MR imaging methods

PURPOSE

To analyze and compare three quantitative MRI methods to determine the degree of muscle involvement in oculopharyngeal muscular dystrophy (OPMD).

MATERIALS AND METHODS

Muscle fat content (MFC) was determined based on water-fat quantification using a 2-point Dixon (2PD) method and on a histogram analysis of the free induction decay (FID) signal of a gradient-spoiled steady-state free precession (SSFP) sequence. In addition, transverse relaxation times (T₂) of muscle tissue were calculated using a monoexponential decay model.

RESULTS

We observed an increased mean MFC in OPMD patients as compared to healthy controls with the adductor magnus and soleus muscles being the most involved muscles in the thigh and calf, respectively. Furthermore, strong correlations (0.78 < R² < 0.94) between different quantitative MR methods were observed. Fewer outliers, however, were obtained by the 2PD method and T₂ measurements, suggesting these methods being superior to the SSFP-FID method.

CONCLUSION

Quantitative MR techniques, such as fast multiecho Dixon methods and T₂ imaging, can reliably differentiate between healthy and dystrophic muscles in OPMD, even if muscles are only marginally affected. Quantitative methods thus represent a promising tool that may be able to monitor more objectively the individual disease progression and treatment response in future clinical trials in muscular dystrophies.

Aberrant splicing in the LMNA gene caused by a novel mutation on the polypyrimidine tract of intron 5

INTRODUCTION

Familial dilated cardiomyopathy with conduction system defects variably associated with skeletal muscle abnormalities is frequently caused by LMNA gene mutations.

METHODS

A family affected by cardiac abnormalities, either isolated or variably associated with skeletal muscle compromise, was identified. LMNA gene analysis was applied to all family members.

RESULTS

A novel intron 5 (c.937-11 C > G) mutation was identified. mRNA transcription analysis was subsequently performed, and cDNA was obtained from mutated patients. It displayed an aberrant splice product featuring the insertion of 40 nucleotides from intron 5, leading to a frameshift. Computational predictions identified a cryptic splice site 40 bp upstream from the canonical site; this alternative splicing event was elicited by intronic mutation, which seems to interfere with the polypyrimidine tract of the canonical site.

CONCLUSIONS

We have described the first mutation on the LMNA gene interfering with the polypyrimidine tract. Our findings underline the importance of including introns in the search for mutations.

CD8(+) T cells in facioscapulohumeral muscular dystrophy patients with inflammatory features at muscle MRI

Facioscapulohumeral muscular dystrophy (FSHD) is an inherited disease, and although strongly suggested, a contribution of inflammation to its pathogenesis has never been demonstrated. In FSHD patients, we found by immunohistochemistry inflammatory infiltrates mainly composed by CD8(+) T cells in muscles showing hyperintensity features on T2-weighted short tau inversion recovery magnetic resonance imaging (T2-STIR-MRI) sequences. Therefore, we evaluated the presence of circulating activated immune cells and the production of cytokines in patients with or without muscles showing hyperintensity features on T2-STIR-MRI sequences and from controls. FSHD patients displaying hyperintensity features in one or more muscles showed higher CD8(+)pSTAT1(+), CD8(+)T-bet(+) T cells and CD14(+)pSTAT1(+), CD14(+)T-bet(+) cells percentages and IL12p40, IFNγ and TNFα levels than patients without muscles displaying hyperintense features and controls. Moreover, the percentages of CD8(+)pSTAT1(+), CD8(+)T-bet(+) and CD14(+)pSTAT1(+) cells correlated with the proportion of muscles displaying hyperintensity features at T2-STIR sequences. These data indicate that circulating activated immune cells, mainly CD8(+) T cells, may favour FSHD progression by promoting active phases of muscle inflammation.

T2 mapping in Duchenne muscular dystrophy: distribution of disease activity and correlation with clinical assessments

PURPOSE

To analyze T2 maps of pelvic and thigh muscles in Duchenne muscular dystrophy (DMD), to identify the most severely affected muscle, and to correlate the T2 of muscle with the grade of fatty infiltration at nonquantitative magnetic resonance (MR) imaging and results of clinical assessment.

MATERIALS AND METHODS

This prospective study was HIPAA compliant and was approved by the institutional review board; written consent was obtained from all participants' parents or guardians. Thirty-four boys with DMD (mean age, 8.4 years) were evaluated clinically (age, clinical function score, timed Gower score, time to run 30 feet, and serum creatine kinase [CK] level) and with nonquantitative MR imaging and axial T2 mapping from the iliac crest to the mid thigh. The T2 maps and mean T2 of 18 muscles in the pelvis and thighs were analyzed to identify the most severely involved muscle. The amount of fatty infiltration was assigned a grade of zero to four for all pelvic and thigh muscles by using T1-weighted nonquantitative MR images. The Spearman correlation coefficients model was used to correlate the mean T2, nonquantitative MR imaging score and clinical assessments.

RESULTS

The gluteus maximus muscle had the highest T2. The mean T2 for this muscle showed a significant correlation with the nonquantitative MR imaging score for fatty infiltration (P < .001) and with all clinical assessments except CK level.

CONCLUSION

Gluteus maximus muscles are most severely affected in patients with DMD. The T2 of the gluteus maximus muscle can be used as a quantitative and objective measure of disease severity.

Only fat infiltrated muscles in resting lower leg of FSHD patients show disturbed energy metabolism

Facioscapulohumeral muscular dystrophy (FSHD) is characterized by asymmetric dysfunctioning of individual muscles. Currently, it is unknown why specific muscles are affected before others and more particularly what pathophysiology is causing this differential progression. The aim of our study was to use a combination of (31)P magnetic resonance spectroscopic imaging (MRSI) and T1-weighted MRI to uncover metabolic differences in fat infiltrated and not fat infiltrated muscles in patients with FSHD. T1-weighted images and 3D (31)P MRSI were obtained from the calf muscles of nine patients with diagnosed FSHD and nine healthy age and sex matched volunteers. Muscles of patients were classified as fat infiltrated (PFM) and non fat-infiltrated (PNM) based on visual assessment of the MR images. Ratios of phosphocreatine (PCr), phosphodiesters (PDE) and inorganic phosphate (Pi) over ATP and tissue pH were compared between PFM and PNM and the same muscles in healthy volunteers. Of all patients, seven showed moderate to severe fatty infiltration in one or more muscles. In these muscles, decreases in PCr/ATP and increases in tissue pH were observed compared to the same muscles in healthy volunteers. Interestingly, these differences were absent in the PNM group. Our data show that differences in metabolite ratios and tissue pH in skeletal muscle between healthy volunteers and patients with FSHD appear to be specific for fat infiltrated muscles. Normal appearing muscles on T1 weighted images of patients showed normal phosphoryl metabolism, which suggests that in FSHD disease progression is truly muscle specific.