Myonecrosis

Last revised by Daniel J Bell on 21 Jun 2021

Myonecrosis is a myopathy involving infarction of skeletal muscle and can have the appearances of an intramuscular mass. 

Myonecrosis represents an infarction of the skeletal muscles. It has a variety of causes 1-3:

Calcific myonecrosis is a specific form, most commonly observed as a complication of posttraumatic compartment syndrome in the anterior compartment of the leg, and is characterized by dense, dystrophic calcifications

Plain film can usually only demonstrate the late sequelae of myonecrosis characterized by dystrophic soft tissue calcifications 3.

Also relatively insensitive, it can better assess the exact position and extent of calcifications within the muscles. 

Non-contrast, fluid-sensitive sequences may show a specific swelling and edema of the muscles. 

Absent enhancement of the affected muscle following IV contrast administration is virtually pathognomonic for myonecrosis. Focal enhancement is suggestive of partial viability of the muscle tissue 3. Subacute myonecrosis may show rim enhancement, which can be mistaken for an abscess. Administration of IV contrast is contraindicated in rhabdomyolysis. 

The stipple sign, whereby there are foci of enhancement surrounded by an area of non-enhancing muscle, itself with a ring of enhancement, is characteristic of myonecrosis 4.

In chronic myonecrosis, muscle atrophy, scar tissue formation, or dense calcifications may dominate the picture. 

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