Clinical Reasoning: A 47-year-old woman with left shoulder pain after a fall.

SECTION 1 A 47-year-old right-handed woman fell to the ground while dancing. She hit her head and neck. However, she did not lose consciousness and continued to dance. Three days later, she developed severe sharp and burning left shoulder pain radiating into her left arm. The pain was associated with weakness and numbness. She also noticed right facial numbness. On review of systems, she had no visual, swallowing, speech, or bowel/bladder disturbances. Prior to the incident, she was in good health and took no medications. She drank alcohol only socially, and had a remote history of social smoking. Examination 5 weeks later revealed marked left deltoid, left infraspinatus, and left biceps weakness. Left biceps and brachioradialis reflexes were absent. Sensation to pinprick was decreased in the first 2 digits of the left hand. An MRI of the cervical spine showed no disc herniation, cord lesion, or foraminal stenosis. EMG and nerve conduction studies (NCS) showed fibrillations and loss of motor unit potentials in the C5-6 innervated muscles. Sensory potentials were intact, consistent with a radiculopathy rather than a plexopathy. The working diagnosis was left cervical radiculitis and the patient was prescribed gabapentin, hydrocodone, and prednisone. Three weeks later, the patient’s left shoulder pain and weakness had worsened. The pain prevented her from having good quality sleep. She also had new right shoulder pain and difficulty lifting her right shoulder. The combination of prednisone, gabapentin, and hydrocodone only transiently improved her symptoms. Examination now also revealed weakness in the right deltoid, right biceps, and right infraspinatus.