A peripheral nerve block is a treatment to prevent the transmission of pain through the nervous system. It involves administration of pain medication through a needle or injection to achieve the elimination of pain impulses that lead to receiving centers. This method for blocking peripheral nerves is frequently supplemented by performing a fluoroscopy (a method of obtaining X-ray images in real time) or CAT (Computerized Axial Tomography) which allow the physician to place the needle in the right place. The effects of this technique are usually immediate but not lasting. Depending on the severity of each patient, some people need several sessions to get real pain relief.