Yes - there are two types of RSD, hot and cold, and a doctor will feel your extremity on examination and compare your RSD impacted extremity to your normal extremity for differences.

I have seen this used for two purposes. First, I have seen the difference in temperature change used to diagnose RSD. In my case, my impacted right extremeties became extremely cold upon the onset of RSD. The neurologist used this differential as input to her diagnosis.

Secondly, I have seen the difference in temperature change used to diagnose the effectiveness of Stellate Ganglion Blocks. Following each Stellate Ganglion Block for my right arm, the neurologist evaluated the temperature of my right arm as one criteria as to whether the block had "taken". Each time, the temperature increased. She told me that we knew that the RSD in my arm was sympathetically mediated.

When my RSD spread to my right leg, I also had "cold" RSD. However, following my blocks, there was no temperature change. This, among other inputs, led my neurologist to conclude that the RSD in my leg was not sympathetically mediated. Sadly, this eliminated blocks as a treatment option.

It's interesting - temperature can be a useful diagnostic tool and treatment tool for us. Hope my experience is helpful to you. Many well wishes.