Expanding the differential of shoulder pain: Parsonage-Turner syndrome.

A 44-year-old man was in his car when it was rear-ended in a minor motor vehicle collision, during which his right forearm contacted the steering wheel. Shortly thereafter, pain in his right shoulder developed, but initial work-up was unremarkable. His pain progressed to shoulder girdle weakness over several months and did not improve after 2.5 years. At the time of consultation, he complained of right-sided neck pain radiating to the right deltoid muscle and axilla as well as right shoulder blade pain with shoulder girdle weakness. Repeated electrodiagnostic studies revealed denervation limited to the serratus anterior and right deltoid muscles without evidence of cervical radiculopathy. He was diagnosed with Parsonage-Turner syndrome, which is a neurologic condition characterized by acute onset of shoulder and arm pain followed by weakness and sensory disturbance. The authors review patient presentation, physical examination, and work-up needed for diagnosis of this syndrome to help physicians avoid administering unnecessary tests and treatment.