MAGNETIC-RESONANCE FINDINGS IN SKELETAL-MUSCLE TEARS

Magnetic resonance (MR) images of skeletal muscle tears can clearly de lineate the severity of muscle injury. Although MR imaging is seldom n ecessary in patients with acute muscle trauma, it can be helpful in de ciding on clinical management. The two major MR findings in acute musc le tears are deformity of the muscle and the presence of abnormal sign al reflecting hemorrhage and edema. In acute tears, methemoglobin with in the extravascular blood causes high-signal areas on both T1- and T2 -weighted images. With partial tears, the blood may dissect in a disti nctive linear pattern along the muscle bundles and fibers. As healing begins, the muscle signal diminishes, first on the T1-weighted images and then on the T2-weighted images. When there is residual abnormal si gnal on images obtained more than several months after the injury, it is presumed to represent hemorrhage from recurrent tears. In patients with a questionable history of a remote injury, the clinical presentat ion may be that of persistent pain or a soft tissue mass. In these cas es MR imaging may identify the cause of the pain and can exclude a neo plasm by proving that the mass is a hypertrophied or retracted muscle. Thus, MR imaging has a limited, but occasionally important role in se lected patients with skeletal muscle tears.