The nerve block is a treatment to prevent the transmission of pain through the nervous system. Consists of administration of analgesic medication through a needle or injection to achieve the suppression of impulses that carry pain until receiving centers. This system is particularly care of handling the peripheral nerves located in a given area. In addition, this procedure for peripheral nerve block is frequently supplemented by central realization of fluoroscopy ( a method of obtaining X-ray images in real time) or CAT (computerized axial tomography ) which will allow the doctor put the needle in the right place. The effects of this technique are usually immediate but not lasting. Besides, depending on the severity of each patient, some people need several sessions to get real pain relief.