Suprascapular nerve injury restricted to the infraspinatus muscle is an uncommon condition. We present a 29 year-old man who complained of right shoulder pain and weakness for 8 months. Physical examination revealed atrophy of right infraspinatus muscle and T2 weighted MRI of the right shoulder revealed a mass with homogeneous high intensity at the spinoglenoid notch and atrophy of right infraspinatus muscle. EMG study revealed abnormal spontaneous activities and reduced recruitment pattern of motor units in right infraspinatus muscle. Symptoms improved after the excision of a mass which was a ganglion cyst by pathologic examination. We were reporting a case of suprascapular nerve injury restricted to the infraspinatus muscle. (J Korean Acad Rehab Med 2002; 26: 819-821)
