Local pathological findings in experimental dorsal root entry zone lesions performed by mechanical section, laser and radiofrequency. A comparative study.

Dorsal root entry zone lesions are nowadays accepted as a first choice of treatment to alleviate certain types of chronic pain though it is still controversial to decide proper procedure for lesioning. Based on this last argument in 15 mongrel dogs different types of lesions using mechanical microsection, radiofrequency and laser were done. Under general anaesthesia a C-3 to C-7 laminectomy was performed in all animals and after open the dura mater the posterior nerve rootlets and posterolateral sulcus were identified using magnification. In 5 dogs, a longitudinal 1 mm deep incision from C-4 to C-6 spinal cord segments coinciding with the sulcus was carried out with a microknife; in other 5, a sequence of thermocoagulations produced by a radiofrequency current lower than 35 mA was done at same places and level with intervals of 2 mm; and in the rest of animals, an alike incision in depth, location and level was realised by carbon dioxide laser. Four days and three months after lesioning 2 and 3 animals of each group were sacrificed and spinal cord specimens submitted for histological and ultrastructural studies. Low-power microscopic examination showed that all lesioning methods were able to produce a reasonable well delimited necrotic area involving the whole dorsal root entry zone structures, slightly more diffuse with the laser. Acute perilesional changes as well as chronic ones were nevertheless more evident in mechanical and radiofrequency lesions, over all regarding oedema, perivascular haemorrhage, intraluminal thrombosis and ischaemic alterations.