pianoplayer - hi and welcome aboard, although we're always sorry to know someone else is suffering with this freaking condition.
Things are pretty slow around here because of the holidays, and you'll get more replies by starting your own "newbie" post, I suspect, as this was bumped up in particular for a person who was asking about the subject.
Yeah, double and even triple crush are problematic - BUT - most TOS surgeons agree that if you have problems ABOVE the elbow at the thoracic outlet (brachial plexus, scalenes) or pec minor, those problems need to be resolved FIRST. If a serious effort at therapy can do that (correct PT, massage, posture, ultrasound, rib mobilization/ muscle release by a chiro/DO, warm water therapy, proper nutrition, breathing, pain management, Feldenkrais, Alexander Technique, Tai Chi or the like, whichever YOUR body responds to best), that is the best possible outcome. If therapy does not bring you enough recovery or relief so that you can you can enjoy any quality of life with TOS, or you can't tolerate the level of pain and disfunction you are living with on a daily basis, then surgery is an option.
Depending on the type of TOS ( veinous, arterial, true neurogenic, disputed neurogenic) and the cause (accident, work, thrombosis, broken collarbone, anatomy, etc) surgery has better odds for some than others. It also has some major risks, although these are fairly low if you select a very experienced TOS surgeon. And while many are much better after surgery, others see modest to slight relief of pain and sx, and some little to no relief at all. A very few have worse pain due to developing RSD, a neuropathic pain syndrome that is a risk of any surgery, but that seems to be more of a risk for those with existing neuropathic pain.
Anyway, if the TOS is treated successfully, often the problems at elbow and even wrist will disappear. The analogy often used is a garden hose. When it is kinked in one place, it tends to kink further down the line. Remove the kink that caused the problem to begin with, and the hose will often straighten out.
The nerve is ONE cell from the neck to the fingertip, with many branches. If it is inflamed and becomes trapped, so it can't move freely, in the brachial plexus or pec minor space, it is more likely to move abnormally and become irritated in other areas, particularly where it must bend, at the joints. Free up the primary entrapment, and the nerve should be able to glide freely along the entire path again.
Look forward to getting to know you better. My cousin is also a piano player, though he's playing little at present. He supported himself tuning pianos for a few years, and playing nights with a group for every kind of gig. His sister's boy plays sax professionally, and some piano as well. My girls (16 and 12) have taken piano 6 yrs and 4 yrs but are not taking lessons this year. I'm determined the older one will take them next year again - she plays beautifully, and can pick up by ear songs she knows from CD or radio. The younger is just NOT into practicing. But both have beautiful voices and sing in choir at school and church and musicals, and reading music is a great skill to have. My husband is a bass guitarist, although work and family keep him too busy to play these days unfortunately. At any rate, music is a big part of our lives, and I can imagine how difficult it must be when you're a musicial afflicted with this BEAST! I'm SO sorry!!
Is it at all possible to try playing seated in a chair with arms, like a computer chair, adjusted to the right height for your piano? Or only playing a keyboard for now? I'd try to rest the arms as much as possible, if you're not playing, try limiting yourself to 1/2 hour of practice or playing. If that's not practical, make it an hour, but split it into 2 1/2 hour sessions. When you're done for the day, soak in a moderately warm - but not boiling hot - bath, to relax the muscles. Add some Epsom salts to the water.
A medium-light massage is good too, but NOT the deep-tissue stuff - your nerves will FREAK! You can get rice-filled microwave hot/cold packs at Walgreens or CVS drugstores. Pop them in the microwave for a minute then wrap around your elbow, wrist or neck. You can get pain creams or gels online, either Sombra, (menthol smell, but works great) or Biofreeze (not much smell, wear anywhere), rub into trouble spots. Or ask Dr about prescription for ketamine cream or lotion, or Lidocaine patches. Also about triggerpoint injections for hard pea-like painful knots in upper back and neck muscles.
That's all my advice for the moment - hope something helps!
beth