Many non TOS specialized drs , have only a basic & biased view of TOS.
Is it is not well understood and no imaging clearly proves it , unless there is a bony anomaly/ extra cervical rib, or if doppler shows compression on a blood supply.

Advanced PT's /chiropractors /bodyworkers often understand it better due to more intensive lessons on muscles, posture , function, fascia....

I did not have high pain which is usually nerve TOS, vascular TOS could be artery or vein related - it usually shows with swelling heaviness , possible clots, and veins showing, whit hands when up in air.. another TOS is called disputed - usually more related to long term chronic RSI's /forward head/forward/hunched shoulders postures.

Just mentioning it in case it may fit for someone.