The odds of paralysis are very minimal. Is it worth it for temporary relief? Not in my opinion. BUT, if done early enough they can put a patient into remission, and there is no way to know if your relief will only be temporary until you go through a series of them. It is a serious medical procedure that should be done by a skilled and meticulous doc via fluoroscopy, and the patient should have a massage afterwards. Even the meds injected make a big difference. It shouldn't be treated like a block given in child birth, which only needs to be effective for hours and does not need the precision an RSD patient does.
Tens of thousands of patients have undergone SGB for RSD. It's not as if this an untried course of treatment.
The thing with RSD, is spread can happen for a variety of reasons or for no reason. You have to figure out what calms your system down asap when any abnormal pain starts. Lidoderm patches, warm baths with Epsom Salts, prednisone, massage, tens unit, additional pain meds, etc.
Once a person goes beyond the 6-12 month window, your odds of recovery fall. I've had RSD for 10+ years. There is a big difference in coping with severe pain for months as opposed to years, btw. By the time many of us are diagnosed, the window is past. Add to that, the amount of reading required, and learning how to respond to a dysfunctional body, and we're left with wishing we could go back in time with the knowledge we now posses. So please understand that's my prospective. Of course get the best care possible, but don't be so fearful of the what if's that your window closes on you.
And apparently those that start out with a cold limb/s have been found to have more severe cases.