The role of gray-scale ultrasound in assessment of myositis

Aim: The aim of the study is to analyze whether gray-scale ultrasound is useful in characterizing the skeletal muscle architecture in myositis.

Method: This study group consists 25 patients, aged 19–77 years, examined by greyscale ultrasound with a 7.5–13MHz transducer. The patients had histologically proven polymyositis (13 patients) and dermatomyositis (12 patients). Data from a control group of 25 healthy volunteers were used to define the normal appearance of the muscles. The ultrasound examination was performed at the level of the thigh, shank or arm, in neutral position and with the muscle relaxed. Bilateral, the same level, transverse and longitudinal scans, using both anterior and posterior approach were used. The images were analyzed in conjunction with clinical, biochemical and electromyography data and muscular biopsy. 12 patients were followed-up, after anti-inflammatory therapy.

Results: The different types of inflammatory myopathies presented typical, but not specific ultrasound features. Polymyositis showed atrophy and increased ecogenicity, especially in lower extremity muscles, whereas in dermatomyositis clear muscle atrophy was rare and ecogenicity was higher in the arm muscles. Ecogenicity was lower in dermatomyositis compared to polymyositis.

Conclusion: Grayscale ultrasound contributes to the assessment of patients with myositis by supplying differential diagnostic signs based on the location of atrophy and identification of abnormalities in ecogenicity.