Contrast-enhanced Ultrasound in Dermatomyositis- and Polymyositis

Update on muscle imaging in myositis

PURPOSE OF REVIEW

Imaging techniques such as MRI, ultrasound and PET/computed tomography (CT) have roles in the detection, diagnosis and management of myositis or idiopathic inflammatory myopathy (IIM). Imaging research has also provided valuable knowledge in the understanding of the pathology of IIM. This review explores the latest advancements of these imaging modalities in IIM.

RECENT FINDINGS

Recent advancements in imaging of IIM have seen a shift away from manual and qualitative analysis of the images. Quantitative MRI provides more objective, and potentially more sensitive characterization of fat infiltration and inflammation in muscles. In addition to B-mode ultrasound changes, shearwave elastography offers a new dimension to investigating IIM. PET/CT has the added advantage of including IIM-associated findings such as malignancies.

SUMMARY

It is evident that MRI, ultrasound and PET/CT have important roles in myositis. Continued technological advancement and a quest for more sophisticated applications help drive innovation; this has especially been so of machine learning/deep learning using artificial intelligence and the developing promise of texture analysis.

255th ENMC workshop: Muscle imaging in idiopathic inflammatory myopathies. 15th January, 16th January and 22nd January 2021 - virtual meeting and hybrid meeting on 9th and 19th September 2022 in Hoofddorp, The Netherlands

The 255th ENMC workshop on Muscle Imaging in Idiopathic Inflammatory myopathies (IIM) aimed at defining recommendations concerning the applicability of muscle imaging in IIM. The workshop comprised of clinicians, researchers and people living with myositis. We aimed to achieve consensus on the following topics: a standardized protocol for the evaluation of muscle images in various types of IIMs; the exact parameters, anatomical localizations and magnetic resonance imaging (MRI) techniques; ultrasound as assessment tool in IIM; assessment methods; the pattern of muscle involvement in IIM subtypes; the application of MRI as biomarker in follow-up studies and clinical trials, and the place of MRI in the evaluation of swallowing difficulty and cardiac manifestations. The following recommendations were formulated: In patients with suspected IIM, muscle imaging is highly recommended to be part of the initial diagnostic workup and baseline assessment. MRI is the preferred imaging modality due to its sensitivity to both oedema and fat accumulation. Ultrasound may be used for suspected IBM. Repeat imaging should be considered if patients do not respond to treatment, if there is ongoing diagnostic uncertainty or there is clinical or laboratory evidence of disease relapse. Quantitative MRI is established as a sensitive biomarker in IBM and could be included as a primary or secondary outcome measure in early phase clinical trials, or as a secondary outcome measure in late phase clinical trials. Finally, a research agenda was drawn up.

Update of Contrast-enhanced Ultrasound in Musculoskeletal Medicine: Clinical Perspectives - A Review

Contrast-enhanced ultrasound (CEUS) uses an intravascular contrast agent to enhance blood flow signals and assess microcirculation in different parts of the human body. Over the past decade, CEUS has become more widely applied in musculoskeletal (MSK) medicine, and the current review aims to systematically summarize current research on the application of CEUS in the MSK field, focusing on 67 articles published between January 2001 and June 2021 in online databases including PubMed, Scopus, and Embase. CEUS has been widely used for the clinical assessment of muscle microcirculation, tendinopathy, fracture nonunions, sports-related injuries, arthritis, peripheral nerves, and tumors, and can serve as an objective and quantitative evaluation tool for prognosis and outcome prediction. Optimal CEUS parameters and diagnostic cut off values for each disease category remain to be confirmed.

Muscle imaging in myositis: MRI, US, and PET

Imaging is an important tool in the evaluation of idiopathic inflammatory myopathies. It plays a role in diagnosis, assessment of disease activity and follow-up, and as a non-invasive biomarker. Among the different modalities, nuclear magnetic resonance imaging (MRI), ultrasound (US), and positron emission tomography (PET) may have the most clinical utility in myositis. MRI is currently the best modality to evaluate skeletal muscle and provides excellent characterization of muscle edema and fat replacement through the use of T1-weighted and T2-weighted fat suppressed/STIR sequences. Although MRI can be read qualitatively for the presence of abnormalities, a more quantitative approach using Dixon sequences and the generation of water T2 parametric maps would be preferable for follow-up. Newer protocols such as diffusion-weighted imaging, functional imaging measures, and spectroscopy may be of interest to provide further insights into myositis. Despite the advantages of MRI, image acquisition is relatively time-consuming, expensive, and not accessible to all patients. The use of US to evaluate skeletal muscle in myositis is gaining interest, especially in chronic disease, where fat replacement and fibrosis are detected readily by this modality. Although easily deployed at the bedside, it is heavily dependent on operator experience to recognize disease states. Further, systematic characterization of muscle edema by US is still needed. PET provides valuable information on muscle function at a cellular level. Fluorodeoxyglucose (FDG-PET) has been the most common application in myositis to detect pathologic uptake indicative of inflammation. The use of neurodegenerative markers is now also being utilized for inclusion body myositis. These different modalities may prove to be complementary methods for myositis evaluation.

Contrast-enhanced ultrasound for musculoskeletal indications in children

The increasing use of contrast-enhanced ultrasound (CEUS) has opened exciting new frontiers for musculoskeletal applications in adults and children. The most common musculoskeletal-related CEUS applications in adults are for detecting inflammatory joint diseases, imaging skeletal muscles and tendon perfusion, imaging postoperative viability of osseous and osseocutaneous tissue flaps, and evaluating the malignant potential of soft-tissue masses. Pediatric musculoskeletal-related CEUS has been applied for imaging juvenile idiopathic arthritis and Legg-Calvé-Perthes disease and for evaluating femoral head perfusion following surgical hip reduction in children with developmental hip dysplasia. CEUS can improve visualization of the capillary network in superficial and deep tissues and also in states of slow- or low-volume blood flow. In addition, measurements of blood flow imaging parameters performed by quantitative CEUS are valuable when monitoring the outcome of treatment interventions. In this review article we present current experience regarding a wide range of CEUS applications in musculoskeletal conditions in adults and children, with emphasis on the latter, and discuss imaging techniques and CEUS findings in musculoskeletal applications.

The Utility of Shear-Wave Elastography in the Evaluation of Myositis

Changes in muscle elasticity are expected in patients with untreated myositis. The purpose of this study was to define the accuracy of shear-wave elastography (SWE) in diagnosing myositis. This case control study included 21 patients (mean age, 49.4 y; 12 women) with myositis who underwent SWE, magnetic resonance imaging (MRI) and biopsy of the involved muscle group. SWE was performed accordingly in a control group (n = 24; mean age, 51.2 y; 8 women). Blood tests consisted of creatine kinase (CK) and aldolase. Two operators performed SWE in longitudinal and transverse planes of muscular fibers, quantifying the mean shear-wave velocity (SWV) and the pattern of stiffness. On MRI, short-TI inversion recovery (STIR) signal hyperintensity and T1 contrast enhancement of muscle was considered diagnostic for myositis. The patient group suffered from different types of myositis (nine patients with polymyositis, eight with dermatomyositis and four with other types of myositis). Blood tests showed significantly increased CK and aldolase values in patients with myositis (p < 0.001 and p < 0.0001). MRI showed a sensitivity of 0.95. In the patient group, the mean SWVs of longitudinal and transverse measurements were 2.8 ± 1.4 m/s and 3.1 ± 1.2 m/s, respectively. In the control group, SWVs were 2.3 ± 0.5 m/s and 2.4 ± 0.5 m/s, respectively. The difference between transverse measurements was significant (p = 0.02). Increased heterogeneity as a marker for myositis in transverse SWE showed a sensitivity of 0.8, specificity of 0.79, positive predictive value (PPV) of 0.76 and negative predictive value (NPV) of 0.82. Inter-observer difference was very low (κ = 0.92). Increased heterogeneity in both planes compared with histologic results showed a sensitivity of 0.56, specificity of 0.93, PPV of 0.91 and NPV of 0.62. Spearman correlation between CK <1000 U/L and SWE was 0.54. In conclusion, transverse orientation SWE may serve as an imaging biomarker for the diagnosis of myositis through the display of a heterogeneous pattern and increased absolute SWV values of inflamed muscles.

Atypical Power Doppler Ultrasound Findings in Juvenile Idiopathic Inflammatory Myositis (JIIM) Flare

Juvenile idiopathic inflammatory myositis (JIIM) is a multisystem inflammatory disease that impacts the muscles, skin, and blood vessels. Gray-scale power Doppler ultrasound is a technique that can be used to assist the diagnosis of JIIM and myositis in general. We report a case of an atypical symptomatic JIIM myositis flare that shows increased muscle echogenicity without the corresponding increase (complete absence) of Doppler flow.

A novel grey Scale and Power Doppler ultrasonographic score for idiopathic inflammatory myopathies: Siena Myositis Ultrasound Grading Scale

OBJECTIVES

No clear-cut guidelines exist about the use of diagnostic procedures for idiopathic inflammatory myopathies (IIM) and only scanty and conflicting data report the use of ultrasound (US). In this regard, we aimed to assess if grey-scale (GS) and Power Doppler (PD) US, graded with a 0-3-points-scale, may be a reliable tool in a cohort of patients affected by IIM.

METHODS

All patients underwent US examination of both thighs in axial and longitudinal scans. Edema and atrophy, both assessed in GS, and PD, were graded with a 0-3-points-scale. Spearman test was used to identify the correlations between US and clinical and serological variables.

RESULTS

A total of 20 patients was included. Six and 2 of them were evaluated twice and 3 times, respectively. Muscle edema was found to be directly correlated with physician global assessment (PhGA), serum myoglobin and PD and negatively with disease duration. PD score was positively correlated to PhGA and negatively to disease duration. Muscle atrophy directly correlated with Myositis Damage Index, disease duration and patients' age. The single-thigh sub-analysis evidenced a direct correlation between PD score and Manual Muscle Test.

CONCLUSIONS

In our cohort, we found that edema and PD are strictly related to early, active myositis, suggesting that an inflamed muscle should appear swollen, thickened and with Doppler signal. Conversely, muscle atrophy reflects the age of the patient and the overall severity of the disease. Such findings shed a new, promising, light in the role of US in diagnosis and monitoring of IIMs.

Juvenile Dermatomyositis: New Clues to Diagnosis and Therapy

PURPOSE OF REVIEW

To identify clues to disease activity and discuss therapy options.

RECENT FINDINGS

The diagnostic evaluation includes documenting symmetrical proximal muscle damage by exam and MRI, as well as elevated muscle enzymes-aldolase, creatine phosphokinase, LDH, and SGOT-which often normalize with a longer duration of untreated disease. Ultrasound identifies persistent, occult muscle inflammation. The myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) are associated with specific disease course variations. Anti-NXP-2 is found in younger children and is associated with calcinosis; anti-TIF-1γ+ juvenile dermatomyositis has a longer disease course. The diagnostic rash-involving the eyelids, hands, knees, face, and upper chest-is the most persistent symptom and is associated with microvascular compromise, reflected by loss of nailfold (periungual) end row capillaries. This loss is associated with decreased bioavailability of oral prednisone; the bioavailability of other orally administered medications should also be considered. At diagnosis, at least 3 days of intravenous methyl prednisolone may help control the HLA-restricted and type 1/2 interferon-driven inflammatory process. The requirement for avoidance of ultraviolet light exposure mandates vitamin D supplementation.

SUMMARY

This often chronic illness targets the cardiovascular system; mortality has decreased from 30 to 1-2% with corticosteroids. New serological biomarkers indicate occult inflammation: ↑CXCL-10 predicts a longer disease course. Some biologic therapies appear promising.

Conventional ultrasound and elastography as imaging outcome tools in autoimmune myositis: A systematic review by the OMERACT ultrasound group

AIMS

To analyze whether there is sufficient data from published literature to demonstrate that ultrasound, including elastography, present good metric properties (truth, discrimination and feasibility) in autoimmune myositis (AIM).

METHODS

A population, intervention, comparator and outcome-structured (PICO) search was performed in Medline, Cochrane Library and Embase database from 01/01/1973 to 08/05/2019. The inclusion criteria required original research involving adult humans, reported in English, assessing ultrasound and elastography in patients with an AIM. Conference abstracts and computer-assisted diagnostics that focused on technique and not ultrasound domains were excluded.

RESULTS

Approximately 2670 articles were identified. Forty-one full-text articles were included in the final analysis. There were 551 AIM patients studied. Eighteen studies (43.9%) had a control group, of which 15 (63.3%) were healthy controls. The age of participants (including controls) varied from 18 to 86 years, and most were females (59%). Diagnosis of AIM was largely biopsy-proven, although some were derived through clinical presentation, positive clinical imaging (ultrasound or otherwise) and/or electromyography and steroid responsiveness. The features examined with ultrasound in the 41 included articles consisted of: muscle echogenicity, bulk, atrophy, architecture, power Doppler, perfusion characteristics, shear wave modulus, shear wave velocity, elasticity index and fasciculations. Twelve studies (29.2%) used quantitative methods to assess these characteristics, whilst others used semi-quantitative, dichotomous/binary and descriptive scoring systems. Criterion validity was met in 14 studies (12/14, 85.7%) and construct validity in 22 studies (22/25, 88.0%). Most published articles reported Level 3b to Level 5 evidence with varying degrees of bias. There was only one longitudinal study examining discrimination. Reliability and feasibility were under-reported.

CONCLUSION

This is the first systematic review studying the utility of ultrasound, including elastography, in AIM. There is some evidence for criterion and construct validity, suggesting that ultrasound may be a promising outcome measurement instrument in AIM. Agreement on the standardization of acquisition, and the definitions of target domains, is required. Additionally, further validation studies are required to determine discrimination, reliability and feasibility.

Diagnostic Value of Muscle Ultrasound for Myopathies and Myositis

Purpose of Review

The purpose of this review is to critically discuss the use of ultrasound in the evaluation of muscle disorders with a particular focus on the emerging use in inflammatory myopathies.

Recent Findings

In myopathies, pathologic muscle shows an increase in echogenicity. Muscle echogenicity can be assessed visually, semi-quantitatively, or quantitatively using grayscale analysis. The involvement of specific muscle groups and the pattern of increase in echogenicity can further point to specific diseases. In pediatric neuromuscular disorders, the value of muscle ultrasound for screening and diagnosis is well-established. It has also been found to be a responsive measure of disease change in muscular dystrophies. In chronic forms of myositis like inclusion body myositis, ultrasound is very suitable for detecting markedly increased echogenicity and atrophy in affected muscles. Acute cases of muscle edema show only a mild increase in echogenicity, which can also reverse with successful treatment.

Summary

Muscle ultrasound is an important imaging modality that is highly adaptable to study various muscle conditions. Although its diagnostic value for neuromuscular disorders is high, the evidence in myositis has only begun to accrue in earnest. Further systematic studies are needed, especially in its role for detecting muscle edema.

Contrast-Enhanced Ultrasound for Musculoskeletal Applications: A World Federation for Ultrasound in Medicine and Biology Position Paper

This World Federation for Ultrasound in Medicine and Biology position paper reviews the diagnostic potential of ultrasound contrast agents for clinical decision-making and provides general advice for optimal contrast-enhanced ultrasound performance in musculoskeletal issues. In this domain, contrast-enhanced ultrasound performance has increasingly been investigated with promising results, but still lacks everyday clinical application and standardized techniques; therefore, experts summarized current knowledge according to published evidence and best personal experience. The goal was to intensify and standardize the use and administration of ultrasound contrast agents to facilitate correct diagnoses and ultimately to improve the management and outcomes of patients.

[CEUS-application possibilities in the musculoskeletal system]

METHODICAL ISSUE

Contrast-enhanced ultrasound (CEUS) offers easily accessible visualization and quantification of the skeletal muscle microcirculation and other tissues in vivo and in real-time with almost no side effects.

AIM

The aim of this review is to present the increasing number of musculoskeletal CEUS applications.

METHODICAL INNOVATIONS/PERFORMANCE

CEUS applications regarding the musculoskeletal system include applications at bone and joints extending beyond the visualization of only the muscular microcirculation. Besides basic muscle physiology, impaired microcirculation in patients with peripheral artery disease or diabetes mellitus and the diagnosis of inflammatory myopathies have been the subject of previous CEUS studies. More recent studies in orthopedics and traumatology have focused on osseous and muscular perfusion characteristics, e. g., in differentiating infected and aseptic non-unions or the impact of different types of implants and prostheses on muscular microcirculation as a surrogate marker of clinical success.

PRACTICAL RECOMMENDATIONS

CEUS of the musculoskeletal system is used in clinical trials or off-label. Therefore, it is not well established in clinical routine. However, considering the increasing number of musculoskeletal CEUS applications, this could change in the future.

Neuromuscular ultrasound in clinical practice: A review

Neuromuscular ultrasound (NMUS) is becoming a standard element in the evaluation of peripheral nerve and muscle disease. When obtained simultaneously to electrodiagnostic studies, it provides dynamic, structural information that can refine a diagnosis or identify a structural etiology. NMUS can improve patient care for those with mononeuropathies, polyneuropathy, motor neuron disease and muscle disorders. In this article, we present a practical guide to the basics of NMUS and its clinical application. Basic ultrasound physics, scanning techniques and clinical applications are reviewed, along with current challenges.

Relevance of ultrasonography in assessing disease activity in patients with idiopathic inflammatory myopathies

AIM

Idiopathic inflammatory myopathies (IIM) comprise a group of rare and heterogeneous diseases difficult to diagnose and follow up. Precise measures for assessing disease activity are not available at the moment. Our objective was to evaluate the usefulness of ultrasonography (US) as a monitoring tool in IIM.

METHOD

The study evaluated IIM patients diagnosed and followed up from 2005 to 2015 in our department. Fifteen patients with a mean age of 52.2 ± 22.09 years and mean disease duration of 4.6 ± 3.20 years were included. Physical examination including muscle strength tests, laboratorial analysis and a selective muscle US assessment were performed for each patient at a scheduled visit.

RESULTS

Nine of the 15 patients were in clinical remission and US assessment revealed a preserved muscle pattern. Symmetrical proximal muscle atrophy was found on US in one patient with longstanding polymyositis (PM) with proximal weakness. Inflammation and focal or generalized muscle edema were present on US in the remaining five patients with muscular weakness suggesting active disease. One of these patients in acute flare presented with atrophy changes in addition to edema. Early untreated myositis presented in one patient with moderate power Doppler (PD) signal.

CONCLUSION

As far as muscle US assessment is concerned, a single specific pattern was not observed in our study. A mixture of muscle edema and atrophy was detected depending on disease activity and duration. US findings seem to correlate well with disease activity, suggested by clinical data, and may be a useful tool to complement patient evaluation.

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.

Role of bone scan in the assessment of polymyositis/dermatomyositis

The aim of this study was to determine the significance of bone scan findings in Korean polymyositis/dermatomyositis (PM/DM) patients. The participants in this study were 26 PM/DM patients who fulfilled the proposed criteria for definite or probable PM/DM. All patients had been examined by bone scan. The results were analyzed visually and quantitatively using the uptake ratios. Correlations between the bone scan parameters of six proximal muscle groups (trapezius, deltoid, biceps, iliopsoas, quadriceps, and gluteus medius and maximus) and clinical parameters (laboratory values and manual muscle test) representing disease activities were assessed. Based on visual analyses of their bone scans, 10 of 14 (71.4 %) patients with active PM/DM had abnormal muscle uptake. Visual grading of the bone scans had a sensitivity and specificity of 74 and 90.9 %, respectively, for the assessment of muscle inflammation. Maximal proximal muscle uptake ratios, as determined on the bone scans, were significantly higher in patients with active PM/DM than in those with inactive disease (median 1.97 vs. 1.02, p = 0.046). Maximal proximal uptake ratios correlated significantly with creatine kinase (r = 0.394, p = 0.046), lactate dehydrogenase (LDH, r = 0.473, p = 0.015), aldolase (r = 0.428, p = 0.029), erythrocyte sedimentation rate (r = 0.412, p = 0.036), C-reactive protein (r = 0.454, p = 0.002), and manual muscle test results (r = -0.399, p = 0.044). Mean proximal muscle uptake ratios correlated significantly with LDH (r = 0.438, p = 0.025) and aldolase (r = 0.572, p = 0.002). Visually assessed proximal muscle uptake grades and maximal proximal muscle uptake ratios as determined by bone scan correlated significantly with the levels of known PM/DM disease activity markers. The findings of this study suggest that bone scan is a useful imaging technique for the evaluation of PM/DM patients.

Classification, diagnosis, and management of idiopathic inflammatory myopathies

The detection and characterization of a large array of autoantibodies, including at least 8 different antisynthetase, anti-SRP, -200/100 (HMGCR), -Mi-2, -CADM-140 (MDA5), -SAE, -p155, -MJ (NXP-2), and -PMS1, frequently associated with distinct and well-defined clinicopathological features, allowed for significant improvement in the definition and diagnosis of idiopathic inflammatory myopathies (IIM). Classification remains difficult, with lingering divergence between the different specialties involved in IIM care, but several categories clearly stand out, including dermatomyositis (DM), overlap myositis (OM), polymyositis, necrotizing myositis, and sporadic inclusion body myositis (s-IBM). Biopsy and histological analysis remain crucial, particularly in the absence of autoantibodies, to accurately specify the diagnosis and rule out mimics such as muscular dystrophies and metabolic myopathies. Numerous infectious agents (in particular human immunodeficiency virus and human T cell lymphotrophic virus-1) and drugs (statins, tumor necrosis factor inhibitors, and proton pump inhibitors) can cause mimic IIM that must also be excluded. Pharmacological treatment, in addition to glucocorticoids and immunoglobulins, now includes mycophenolate mofetil and rituximab, which proved helpful in resistant cases, particularly rituximab in DM and OM. Exercise, initially seen as potentially deleterious, recently was shown to be efficacious and safe. IIM can thus be reasonably well controlled in most cases, although aggressive disease remains refractory to treatment, including some cases of necrotizing myopathy. Sporadic IBM still seems resistant to all medications tested to date.

PET/CT imaging in inflammatory myopathies

Inflammatory muscle diseases are a group of muscle disorders characterized by muscle weakness, fatigue, and an association with malignancy and paraneoplastic syndrome. A diagnosis of idiopathic inflammatory myopathy is suggested by abnormal myometry and rising creatine kinase, but tissue diagnosis is also needed. Magnetic resonance imaging (MRI) helps localize the appropriate site of biopsy, demonstrate the extent of muscle involvement, and monitor the response to therapy. However, the sensitivity of magnetic resonance (MR) is limited, and whole-body imaging is still far from routine. [(18) F]Fluoro-desoxy-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) is currently the ultimate metabolic imaging technique for the management of cancer. It has also been shown to detect inflammatory conditions and to monitor their response to treatment. The use of FDG PET in screening for underlying malignancies is widely reported and recommended in patients with paraneoplastic syndrome. Unfortunately, only a few reports have been published to show the value of FDG PET in inflammatory muscle diseases, which as we show herein, deserve further pursuit.

Functional imaging in muscular diseases

OBJECTIVE: The development of morphological and functional imaging techniques has improved the diagnosis of muscular disorders. METHODS: With the use of whole-body magnetic resonance imaging (MRI) the possibility of imaging the entire body has been introduced. In patients with suspected myositis, oedematous and inflammatory changed muscles can be sufficiently depicted and therefore biopsies become more precise. RESULTS: Functional MR methods visualise different aspects of muscular (patho)physiology: muscular sodium (Na(+)) homeostasis can be monitored with (23)Na MRI; the muscular energy and lipid metabolism can be monitored using (31)P and (1)H MR spectroscopy. (23)Na MRI has reached an acceptable value in the diagnosis and follow-up of patients with muscular Na(+) channelopathies that are characterised by myocellular Na(+) overload and consecutive muscle weakness. Besides MRI, low mechanical index contrast-enhanced ultrasound (CEUS) methods have also been introduced. For evaluation of myositis, CEUS is more efficient in the diagnostic work-up than usual b-mode ultrasound, because CEUS can detect the inflammatory-induced muscular hyperperfusion in acute myositis. Moreover, the arterial perfusion reserve in peripheral arterial disease can be adequately examined using CEUS. CONCLUSION: Modern muscular imaging techniques offer deeper insights in muscular (patho)physiology than just illustrating unspecific myopathic manifestations like oedematous or lipomatous changes, hypertrophy or atrophy.

Ultrasound in the evaluation of the inflammatory myopathies

The lack of precise measures of disease activity may complicate the care of patients with inflammatory myopathies (IM). Techniques currently available to physicians in practice rely on measurement of function, strength, laboratory indices, muscle biopsy, and imaging techniques. Although MRI has become the method of choice to assess IM, it is expensive, difficult for some patients to tolerate, and contraindicated in those with pacemakers, aneurysm clips, and other ferromagnetic biomedical implants. Ultrasonography is an alternative approach to image the muscular system. Newer applications of ultrasound, such as power Doppler sonography (PDS), contrast-enhanced ultrasound, and sonoelastography, show some promising results in further characterizing normal and pathologic states. Technical improvements, including extended field-of-view, compound imaging, and harmonic imaging, further enhance one's ability to display changes in muscle morphology. This article reviews the sonographic appearances of normal and pathologic muscle with respect to inflammatory myopathies.

[Imaging techniques and electromyography in inflammatory myopathies]

Different imaging techniques are used for the diagnosis, evaluation and follow-up of inflammatory myopathies; of these techniques, the ones that provide the largest amount of information are ultrasonography and magnetic resonance imaging. Electrodiagnosis in inflammatory myopathies is based mainly on electromyography (EMG), which shows different patterns according to the different disease presentations. In the acute phase, polyphasic potentials with diminished amplitude and duration are seen, whereas in its chronic phases, mixed neuropathic and myopathic patterns are found. After corticosteroid treatment, EMG tends to return to normal.

Skeletal muscle microvascular flow in progressive peripheral artery disease: assessment with continuous arterial spin-labeling perfusion magnetic resonance imaging

OBJECTIVES

We present the novel application of continuous arterial spin-labeling (CASL) magnetic resonance imaging (MRI) for the measurement of calf muscle perfusion in subjects with progressive peripheral arterial disease (PAD).

BACKGROUND

Peripheral arterial disease is largely considered to be a disease of conduit vessels. The impact of PAD upon microvascular flow in the end-organ, muscle, remains unknown. Continuous arterial spin-labeling is a noninvasive MRI method capable of measuring microvascular flow and might assist in our understanding of the impact of PAD upon the microvasculature.

METHODS

Forty subjects with varying degrees of PAD and 17 age-matched PAD-free subjects were recruited and underwent measurement of the ankle-to-brachial index (ABI) and CASL. Peak hyperemic flow (PHF) and time-to-peak (TTP) were computed and assessed as a function of ABI and calf muscle group.

RESULTS

An ABI dependence was found in both PHF (p = 0.04) and TTP (p < 10(-4)). Whereas TTP increased almost immediately with increasing PAD severity, PHF was, in contrast, relatively well preserved until later stages of disease.

CONCLUSIONS

The CASL flow measurements correlate with disease state as measured by ABI and demonstrate preserved microvascular flow reserve in the presence of early to intermediate vascular disease.

Ultrasound in the inflammatory myopathies

Dermato- or polymyositis must be diagnosed or ruled out early because early immunosuppressive therapy prevents irreversible muscle degeneration. Acute poly- and dermatomyositis are accompanied by normal or increased size, low echogenicity, and elevated perfusion of affected muscles, whereas in chronic poly- and dermatomyositis, the size and perfusion of affected muscles are reduced and echogenicity is increased. Although magnetic resonance imaging is more sensitive in detecting edema-like muscular changes and thereby acute myositis, contrast-enhanced ultrasound with its capability of measuring perfusion has become a useful diagnostic tool in diagnosing acute inflammation in poly- and dermatomyositis.

Limits and perspectives of ultrasound in the diagnosis and management of rheumatic diseases

Musculoskeletal sonography (MSUS) has played a growing role in the diagnosis and management of rheumatic diseases, enabling the imaging of synovitis, bone erosion, and cartilage damage in the early phase of arthritis. "Dynamic" evaluation of tendons and help in guiding needle positioning in interventional manoeuvres are some of the other reasons for its success. MSUS, particularly when coupled with power Doppler (PD) examination, has recently been shown to be an efficient tool for monitoring disease activity and progression in rheumatoid arthritis, spondyloarthritis, crystal-related arthropathy, and osteoarthritis, with general consensus on its interesting results. More specifically, the PD signal has proved to be a simple and promising tool for short-term monitoring of synovial vascularity changes induced by steroids or biological agents in RA patients. MSUS has some limits, because of the physical properties of US and the quality of the equipment; it is, moreover, an operator-related imaging technique, with few standardized protocols. Future goals should be standardization of the examining approach in grey scale and Doppler ultrasound (US), including use of new equipment (3D US), extensive use in other fields (i.e. connective tissue diseases and vasculitis), and possible new applications (e.g. thoracic US).

Inflammatory muscle disease: clinical presentation and assessment of patients

Muscle weakness and muscle fatigue are the most common manifestations in patients with idiopathic inflammatory myopathies (ie, myositis), but other organs are frequently involved such as skin, lungs, joints, and the heart. These could occur before, simultaneously with, or after the onset of muscle symptoms. One tool to structure outcome measure is the International Classification of Functioning, Disability, and Health. Measures of "disability" can be divided into impairment and activity limitation/participation restriction. Most of the available outcome measures for myositis could be classified as measures of impairment, such as muscle strength, serum levels of muscle enzymes, and pulmonary function tests. Measures of activity limitation/participation restriction are also important, such as the myositis activities profile, the visual analog scale to assess impact on general well-being, and the generic short form-36 to capture impact on health-related quality of life.

Quantitative evaluation of muscle perfusion with CEUS and with MR

Functional imaging might increase the role of imaging in muscular diseases, since alterations of muscle morphology alone are not specific for a particular disease. Perfusion, i.e., the blood flow per tissue and time unit including capillary flow, is an important functional parameter. Pathological changes of skeletal muscle perfusion can be found in various clinical conditions, such as degenerative or inflammatory myopathies or peripheral arterial occlusive disease. This article reviews the theoretical basics of functional radiological techniques for assessing skeletal muscle perfusion and focuses on contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging (MRI) techniques. Also, the applications of microvascular imaging, such as in detection of myositis and for discriminating myositis from other myopathies or evaluating peripheral arterial occlusive disease, are presented, and possible clinical indications are discussed. In conclusion, dedicated MR and CEUS methods are now available that visualize and quantify (patho-)physiologic information about microcirculation within skeletal muscles in vivo and hence establish a useful diagnostic tool for muscular diseases.