Provide a practical review of the spectrum of MRI findings in the various, sometimes rare and infrequent, muscular disorders. Depict some atypical and uncommon MRI findings seen in our daily practice.

Abnormal signal intensity within skeletal muscle is a common MRI sign in routine clinical practice. A broad differential diagnosis should be considered, including traumatic, infectious, autoimmune, inflammatory, neoplastic, vascular, neurologic, and iatrogenic conditions. Since MRI findings are similar in many of these conditions, radiologists should pay attention to special issues such as edema pattern distribution, extent and abnormalities of other tissues. Furthermore, knowledge of the potential specific imaging findings in the various, sometimes rare, muscular disorders may also be helpful to reach a closer differential...

In routine management of muscle disorders three recognizable MRI patterns have been described: edema, fat component and mass lesion. 1) EDEMA Characterized by an increase in free water, muscle edema is the most common MRI pattern and is well depicted in fluid-sensitive sequences, either T2-weighted images with chemically selective fat suppression or STIR sequences. Given the many potential causes of muscle edema, it is helpful to subdivide them considering three different groups depending on its distribution: diffuse, focal, or multifocal. - Diffuse edema:Multiple muscles and...

The potential imaging findings in the various, sometimes rare, muscular disorders are helpful for accurate diagnosis. Beyond the common MRI features, we also describe some additional “pearls” that may be key points for reaching the differential diagnosis. Of all our review we emphasize the importance of: - Detection of fatty nodules within cystic muscle lesions may be a pathognomonic finding of intramuscular hydatid disease. -The sign described by us as "butterfly wings" in the gluteal muscle disorders can be a pathognomonic finding of gluteal compartment...

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