Hello Adam. I am Dr. Frank, an Adult Neurologist in NYC. Welcome to JA. The problem you describe of pain in a distribution of the shoulder girdle muscles, sounds like it is a transient upper trunk brachial plexus neuropathy, known as a "stinger" injury. I will attach a webpage that describes the usual symptoms, take a look at it, and let me know if you think it matches your problem. Stingers or Burners usually come from traumatic injury, as in football. But in your case, you have a chronic repetitive injury. So the question is do you have any reflex changes or muscle weakness that is focal? My suspicion is no, if your EMG was done of the shoulder girdle, included needle exam and conduction studies, etc. If you have questions about the study, you can upload it here minus your name, as this is a public forum and I can review it further.
Anyway, so if you have a normal exam, and EMG, then this must be a "vascular" type of brachial plexopathy, where the blood supply to the plexus, which comes off the subclavian artery, and the thyrocervical trunk, is somehow lacking. The weakness/numbness is therefore transitory, and not seen on normal testing, but all of this can be evaluated. The brachial plexus gets imaged using a special MRI, you get an MR Neurogram of the plexus to see if you have an ischemic injury.
Take a look at this webpage. http://orthoinfo.aaos.org/topic.cfm?topic=A00027 Then get back to me to discuss and I will reply. Or if satisfied, please remember to rate this service by clicking on the rating stars, as that is how I am compensated for this work thanks *****