Cyclist:
My case is probably a little different than most TOS cases in that there were no issues with my arm until I dislocated my shoulder last summer. I tore my bicep tendon and labrum, and the ortho put 4 screws in the glenoid to reattach. During that procedure, there were complications (punctured artery and vein) which resulted in an axillary arteriovenous fistula (repaired surgically December 2014) and lesions to the brachial plexus (still present). The joint is also frozen. Dr. Lum received my records in advance of the appointment, and ordered a doppler ultrasound and an angiogram with and without contrast. The doppler took place in his office on the same day as my consult and I had the angiogram at my local hospital and sent him the CDs. He confirmed compression of the subclavian artery at the first rib. He also indicated there was a 10% chance of additional compression from the pec minor - since this will be my third surgery in 9 months, I chose to deal with the pec minor now rather than risk needing a fourth surgery later this year. The neurolysis is to deal with entrapment from scar tissue where the fistula was. I did not need to have scalene blocks or botox, etc. I think when the issue is predominantly vascular, the diagnosis is a little bit easier, though I'm not entirely sure. Thankfully, I haven't been dealing with TOS for years on end like many here have, and had a relatively easy time with the diagnosis.
I hope this info is helpful.