The comparison of neuroablative effects of conventional and pulse radiofrequency techniques

VIII- SUMMARYTHE COMPARISON OF NEUROABLATIVE EFFECTS OF CONVENTIONALAND PULSE RADIOFREQUENCY TECNIQUESRadiofrequency thermocoagulation (RF) has been used for many yearsin pain treatment in order to interrupt pain transmission by mediatingneuroablation. However, this neuroablation caused by high temperatures maylead to deafferantation sequela. During the application, the nerve nearby, due tothe possible damage on it, may have a risk of developing a long-term orirreversible loss of sensory and motor function.Therefore, radiofrequency techniques which maintain the temperaturewithin the physiological limits have been studied and the pulse RF (PRF)technique has been developed. The efficacy of the continous current used inconventional RF (CRF) technique has been increased by changing it into pulsecurrent, two frequencies a second, and therefore there is no need to have atemperature as high as the one applied in conventional RF. As a result, RFapplications, once used on only sensorial nerves, can now also be applied toperipheral nerves with sensory and motor fibers. In our study, we studied on thesciatic nerve, a peripheral nerve which includes all motor, sensory andautonomous fibers, and aimed to compare the neuroablative effects of PRFapplications with conventional RF techniques.In the study, we formed five groups each had six adult male Wistar rats.Any procedure was not applied to the rats in the control group. Following thegeneral anesthesia, RF electrode was placed very close to the sciatic nerve butnot to cause any damage to the nerve. RF energy was not given to the rats inSham group. In the CRF40 group, the rats were applied 400C CRF for 90seconds. In the CRF80 group, the rats were applied 800C CRF for 90 seconds.In the PRF group, the rats were applied 45 V PRF which did not exceed 420Cfor 240 seconds.45Two days later, 2.5% glutaraldehyde phosphate buffered solution wasused for fixation with intracardiac perfusion. The samples, kept in appropriatefixatives, were monitored both with a light and electron microscope (EM).In the light microscopy, HE and Toluidin blue staining revealed nopathological changes in nerve cells in the control group. In the samples of theSham group, there were configurations, endoneural edema and a littledeformation in the myelin sheath in myelin fibers. In the CRF40 group, therewere configurations, deformation and protrusion in the myelin fibers of thesciatic nerves. Edema in perineurium and resolutions in acsoplasma were alsoobserved. Degeneration and protrusion in myelin fibers in the cross section ofsciatic nerves observed in the samples of CRF80 group were more than thosein the CRF40 group. In the samples taken from the PRF group, findings similarto the pathological changes found in other RF applications were comparativelyfewer than those found in other RF applications. In large magnifyingmicroscobic examinations, pathological changes similar to those in smallmagnifying microscobic examinations were studied in details. Corruptions seenin the Sham group increasingly detected in the PRF, CRF40 and CRF80groups.In the studies conducted with an electron microscope, it was detectedthat the findings were similar to those found with a light microscope, and it wasalso found that RF applications caused damage to cell organelles and skeleton.It was also observed that examinations conducted both with the lightmicroscobe and the electron microscope revealed some damage, though notmuch, in the control group but increased in the Sham group and becameincreasingly more distinct in the PRF, CRF40 and CRF80 groups respectively.As a result, in this study the damage to the sciatic nerve caused by RFapplications in the control and Sham groups was compared. Edema, cell andmyelinisian pathological changes due to PRF application were microscopicallyand morphometrically examined. It was concluded that PRF application wassafer than CRF40 and CRF80 applications.The minimal damage determined in the control group suggested thatnerve tissues can be affected even during the any type of procedures applied to46the nerves. The fact that the damage increased more in the Sham group than inthe control group also suggested that the nerve tissues are affected by surgicalapplications as well. It was also considered that, due to high temperature,conventional RF applications caused damage which can not be prevented butdecreased by PRF applications.47