pudding bowl, why you term this clinical case as a relfex sympathetic dystrophy?? (in my country we call thet Sudeck syndrome!).....I believe the patientu mentioned has a possible history of neck pain which in fact start referring in the arm....And if u say that it is 20 years now is a definite CHRONIC PAIN status...Where exactly u conclude that it is CRPS??? Has your patient any history of injury???? As i see no....And besides this syndrome is establishing quickly after an injury there are some tell-tale symptoms which alert the clinician about sympathetic system involvement, which u didnt mention if there are at all, like sweating,increased temperature in skin etc.
Because your patient is in a CHRONICITY u should embark on self-therapy management with some form of exercises, not rely only on passive modalities....Remember that a chronic patient is in a vicious cycle of "kinesiophobia" that makes him more and more disabled resulting in more pain onwards