Pulsed Radiofrequency

Cha, Young Deog

Abstract

RF treatment of spinal pain was initiated by Shealy, with its subsequent description for lesions of the dorsal root ganglion (DRG) by Uematsu. However, the high tip temperature (75degrees C) and large electrode diameter caused serious damage to the DRG, with numerous deafferentiation sequelae. In 1980, small diameter electrodes and the SMK system were introduced, and it than became possible to choose targets in the anterior compartment without the risk of mechanical damage to the major nerve. A radiofrequency is applied through an electrode, with the formation of heat and an electric field around the electrode tip. Recently, the electric field, rather than the heat formation, is thought to be more important in its clinical effect. Pulsed radiofrequency is a method for reducing the temperature, by interrupting the output, and allows sufficient time for the heat generated to be removed due to its thermal conductivity and circulation. The optimal electrical parameters for PRF are unclear. However, in some pilot studies, a more accurate electrode position and lower impedance have shown better clinical effects, but the tip temperature was not related to the clinical effect when the generator output was in Watts. The following recommended parameters have currently been demonstrated: duration 120 s, 45 volt, 2 x 20 msec/sec pulsed mode and a tip temperature lower than 43degrees C. There are four distinct phases in the clinical course following a PRF procedure. First, the stunning phase, a pain free stage at the end of the procedure. Second, a phase of postoperative discomfort, which lasts for up to three weeks, due to the inherent exposure to the electric field. Third, the beneficial effect phase follows, with duration equal to or a little shorter than that of the heat to the lesion. Lastly, a phase of recurrence of pain is interpreted as a default result due to further exposure. PRF is a non-destructive and painless method, and indicates regions, such as the C8 or sacral root. It can also be used in the treatment of neuropathic pain, peripheral nerves and painful trigger areas.