It also depends on whether you are talking about a sympathetic block rather than a true surgical or chemical sympathectomy. Often a sympathetic block is referred to by docs as a sympathectomy. Tha sympathetic block is a diagnostic procedure which may have some temporary therapeutic benefits for some people but is nothing like the sort of sympathectomy that the other posters have been describing. It is common to have at least one such block done and if it is done properly and carefully it should cause no harm or CRPS symptoms in the area of the needle.