Review the pathophysiology of muscle disorders Highlight the role of imaging in the diagnosis of muscle disorders. Present a pictorial radiologic-pathologic correlation ofsample cases from our institution.

The aetiology and classification of muscle disorders is complex; they can be differentiated into hereditary, acquired,relatedto connective tissuedisorders or secondary to neurogenic disorders1. The clinical presentation is important to the differential diagnosis and often includes symptoms of weakness or pain. However, sometimes the presentationis non-specific and the diagnosis is not always evident. For example, patients may present with symptoms that mimic a surgical abdomen or deep vein thrombosis. The age of symptom onset, family history and sex are also important when considering a likely diagnosis....

MRimaging is now used to confirm a presumptive clinicaldiagnosis and plays a crucial role in determining the extent and pattern of disease. It is also useful when identifying targetsfor musclebiopsy and is some centres,is used as a surveillance tool to monitor response to therapy. Imaging can be performed on either a1.5 or 3 Tesla magnet, based on availability. Fluidsensitive sequences(fast or turbo spin echo T2fat saturated orShort Tau Inversior Recovery, STIR) show the extent and distribution of muscle oedema whereasfast or turbo spin echo non-fat...

This exhibit reviewsthe imagingfeatures ofsome of the better understood myopathies. Ithighlights the contributionof imaging to diagnosis by defining extentand pattern ofmuscle involvement, as well asidentifying targets for biopsy. Achieving a correct diagnosis can be challenging and a multidisciplinary approach is key, aimed atasmuch concordance as possible between the clinical, biochemical, imaging and histological findings.

Neuromuscular Disease Center, Washington University, St. Louis, MO, USA. https://neuromuscular.wustl.edu/antibody/infmyop.htm Dalakas MC (2015) Inflammatory Muscle Disorders. N Engl J Med 372:1734-1747 Pinal-Fernandez I, Casal-Dominguez M, Carrino JA, Lahouti AH, Basharat P, Albayda J et al (2017) Thigh muscle MRI in immune-mediated necrotising myopathy: extensive oedema, early muscle damage and role of anti-SRP autoantibodies as a marker of severity. Ann. Rheum. Dis 76:681-687