The use of roentgenograms is necessary in performing diagnostic and therapeutic blocks for two reasons: (1) for more accurate placement of the needles and (2) as an objective record of the position of the needles at the time the anesthetic solution was injected.
Since diagnostic nerve blocks are used to determine the pathways of pain impulses, the problems involved are different from those encountered when nerves are blocked for the purpose of producing anesthesia for surgical procedures. When a patient presents himself for the relief of pain, his physician attempts to find the etiological factor that is causing the pain and to give the patient relief by removing the cause. Such an ideal course of events cannot always be achieved, sometimes because the source of the pain cannot be determined and sometimes because the diagnosed source of the pain cannot be eliminated. In such situations the physician's next recourse is