Muscle Ultrasound in Inflammatory Myopathies: A Critical Review

Muscle ultrasonography is an upcoming tool in the evaluation of neuromuscular disorders. It is easily applicable in multiple clinical settings, has no contraindications, and provides a cost-effective alternative to other imaging modalities such as MRI. However, a known disadvantage of ultrasound is its dependence on examiner expertise. Furthermore, the assessment of muscle quality is done mainly through an assessment of muscle echo intensity, which is affected by machine/system settings, hampering comparison across centers. Over the years new methods have been developed to make results more objective and comparable for the assessment of myopathies. In this review, we will examine the role of ultrasound in the evaluation of idiopathic inflammatory myopathies (IIM), a heterogeneous group of autoimmune disorders which may be treatment-responsive. Studies have shown that ultrasound can be useful both for diagnosis and follow-up of IIM, particularly for dermatomyositis and inclusion body myositis. The addition of other ultrasound modalities such as Doppler and elastography, as well as the application of machine learning, appear promising for IIM. Further developments of these techniques are expected and will lead to more widespread use of ultrasound in the clinical assessment of IIM.