A 24-year-old man came to the doctor with a weak right shoulder. The shoulder wasn’t painful, but for two weeks the man hadn’t been able to do basic tasks such as put on a seat belt or open the refrigerator door. He hadn’t hurt the shoulder doing anything in particular. Why the sudden weakness?
In order to diagnose the problem, doctors did a physical exam and two special tests. First, they used electromyography to check the activity of the shoulder muscles. This test uses electrical recordings to track muscle activity. The test showed low muscle activity in the man’s right shoulder. The infraspinatus muscle was the problem area. This muscle covers most of the shoulder blade and allows the arm to rotate outward.
Next, the doctors did magnetic resonance imaging (MRI). MRI scans show “slices” of the soft tissues inside the body. The patient’s MRI showed a cyst in his shoulder.
The patient had surgery to remove the cyst. He did range-of-motion and strengthening exercises for six weeks after surgery. Within eight weeks, he was able to go back to volleyball and other activities.
Doctors suspect that intense and repetitive activity such as volleyball, construction, weight lifting, or fencing can upset the normal function of the shoulder. This is thought to form a cyst in the passageway of the suprascapular nerve. This nerve goes to the infraspinatus muscle. As the cyst grows, it can trap the nerve and cause weakness in the infraspinatus muscle. For some unknown reason, this occurs mostly in men. Once diagnosed, the problem can be resolved with surgery and physical therapy.