I'm not sure if you are looking for our unique description of the hot/cold pain experienced as a symptom of CRPS or referring to the diagnostic difference between hot/cold CRPS?

It was confusing to me to understand what my doctor meant by "cold" CRPS and that it had a poorer prognosis. After discussing it further with my providers this is the way I understand 'hot/cold' CRPS as a diagnostic term rather than a symptom. The term hot/cold is often used if diagnosis is made early or when symptoms appear rapidly after say surgery, laceration, gun shot wounds etc., . This term is added when there is a distinct and verifiable temperature difference in the affected limb vs. non affected limb. The reason this term is not always used is because more cases of CRPS are diagnosed way to late in the game. With CRPS I/RSD most often the affected body part is warmer to the touch than the non affected limb but then over time or when CRPS I/RSD becomes chronic that same affected limb will turn cold due to progressive vasoconstriction. In CRPS II/Causalgia the diagnosis is often made much sooner compared with CRPS/RSD due to the immediate pain from nerve injury and an obvious inciting event. In such cases if the nerve injury is severe this will increase the likely hood that vasoconstriction occurs rapidly and thus causes the cold temperature of the skin right away. If upon early diagnosis 1-3 months there is obvious quantifiable temperature differences then this term is more likely to be added to the diagnosis. It is well documented that chronic or long standing CRPS I/RSD will start with a warm red/purplish limb and then change over time to cold pale/bluish limb overtime.

The hot/cold burning often described is a symptom of the pain and does not really have any correlation to the temperature of the skin because the nerve signals are mixed up so the perception of the pain for each of us is unique to how our brain perceives it. Just like with allodynia where something say like a feather or cotton ball should not cause pain to the touch but for many of us this will cause anguish. Some might feel the burning/cold early on in the disease and others might feel it later. Some with have symptoms constantly and others might experience things more intermittently.. that is part of what makes CRPS so difficult to treat.

For me-my limb is ice cold and bluish and the feeling is as if there is no skin on my legs and the wounds were packed with salt.. in addition to that (and other crappy symptoms) It sometimes feels like cold water is running down my legs when obviously there is not. When I bathe the warm water actually feels cold on my CRPS limbs.. my brain has my sensory input backwards which my doctor refers to as 'true allodynia' not sure I understand why he states it like that but whatever.. I know my brain is broken ;/