A 26-year-old man complains that he has noticed increased difficulty moving his right arm that started when he took up volleyball. He also sometimes feels pain in his right shoulder (posterior aspect). Upon visual inspection of his back, you notice that the muscles above and below the spine of the scapula are atrophied. When you perform a motor exam, he has weak abduction and external rotation of the right arm. The nerve that is most likely damaged arises from which of the following divisions of the brachial plexus?
1.Trunks
2.Roots
3.Cords
4.Terminal branches
5.Divisions
Explanation
The patient most likely has suprascapular neuropathy. The suprascapular nerve supplies the supraspinatus and infraspinatus muscles, and its compression at the suprascapular notch can induce weakness and atrophy of both muscles, as well as shoulder pain.
The suprascapular nerve arises from the upper trunk of the brachial plexus.
Motor - innervation of supraspinatus and infraspinatus muscles
Sensory and proprioception - innervation to the posterior glenohumeral joint, acromioclavicular joint, subacromial bursa and scapula.