3. Subject has had interventional procedures that may alter the results of QST. Such procedures include neuroablation (chemical or electrothermal) at any time, neuraxial (e.g., epidural) or local anesthetic block within the last eight weeks, and lumbar sympathetic or hypogastric block within the last six months. We consider eight weeks and six months as the minimal time period that must have elapsed after neuraxial injection and lumbar sympathetic block, respectively, in order to minimize the possible influence from a previous interventional procedure.