shoulder imaging: MRI arthrogram

they inject contrast into the shoulder capsule to get a better look at the shoulder structure

Dr. Smith has a good suggestion regarding the shoulder. another possibility is thoracic outlet syndrome (TOS).

I developed TOS from a car accident and had similar symptoms on the affected side. surgery fixed that issue but I still had problems with strength in the upper arm and neck spasms after surgery. about 4 yrs later, they discovered a problem with the shoulder stemming from the same car accident. once the shoulder was fixed, the neck settled down. so you could have a couple of problems going on.

nerve conduction studies are rarely positive.