I am sorry if I am confused about your question. Some doctors for ex if you don't respond to a certain type of treatment like a block they will state that it is cause the pain is coming from the brain not the spine. I am not sure though and I think since people with rsd all respond different it is hard to know.
Many people like stated on here don't have all symptoms of rsd.I don't though some symptoms have changed or happened since the 4 years I have had it. Also for me I did not get rsd the typical way from an injury or accident.
Have you had treatments like blocks and worked with meds? What was your response to those? I am not sure with ketamine but what I feel is we all respond different like I said so it is hard to know.