The myositides: the role of imaging in diagnosis and treatment.

The entities encompassing the syndromes collectively known as myopathies and myositis are composed of numerous separate and distinct disorders with a vast spectrum of clinical signs, symptoms, immunopathology, genetic and environmental influences, as well as overall clinical outcome. Classification of the myositides (diseases of skeletal muscle) remains a rather controversial subject due to our lack of complete understanding of this divergent group of disorders. The mainstay of achieving diagnosis of a myopathy has until relatively recently been with a combination of clinical acumen, laboratory assessment, electromyography, and muscle biopsy. The use of modern high-resolution cross-sectional imaging studies is of particular value in confirming the physical findings and identifying suitable sites for biopsy. Imaging is fast becoming an established part of the overall evaluation of myopathies and myositis, helping to delineate the location and extent of the disease process, and it is being recognized as central to a prompt and accurate diagnosis in some cases. Although radiology has mainly been seen to have a subsidiary role in the diagnosis of myositides, newer imaging techniques following recent determined research interests have began to spark a renewed interest in the complex field of skeletal muscle imaging.