I have had an MRI x2 neither showed anything up. FOr most people it is a symptom based diagnosis as lots of tests come back negative!....

Like you I also have shoulder blade pain/arm/hand and unless there is an obvious cause like extra rib/cervical rib/fibrous band then mri will unlikely be useful in diagnosing tos. it may show another cause of your pain so worth having even if to elimate other causes/conditions.

I have not received an official diagnosis - more of an "your symptoms derive from the thoracic outlet area" and "you have interscalene spasaming and cervical nerve root irritation". FOr some reason lots of dr's seem unknowledgable in the area of tos and seem reluctant to diagnose it.