The morphological effects of a radio frequency lesion adjacent to the dorsal root ganglion (RF-DRG) - an experimental study in the goat

Radiofrequency (RF) lesions adjacent to the dorsal root ganglion (DRG) are increasingly used in the treatment of intractable chronic pain of spinal or igin. Opinions differ on which nerve Fibres are affected by these lesions. Morphological studies have been carried out to assess the effects of radiof requency lesions on nervous tissue. Interpretation has been difficult, sinc e most studies have been performed under circumstances which are not compar able to the clinical situation. This study was undertaken to investigate mo rphological effects of RF lesions as they develop in the normal clinical si tuation. In two goats 22 G 100 mm SMK electrodes with a 5 mm active tip (Ra dionics) were positioned posterior to the lumber dorsal root ganglia (DRG). Sixty-second 67 degreesC lesions were made on one side. The contralateral side was used as sham operation. The goats were sacrificed 2 weeks after th e procedure. The lesions were studied for size as well as for effects on pr oliferation and regeneration using Ki-67 (MIB-1). Lesions made inside the D RG (2x) were 1.8-2.0 mm in size. In these lesions there was a total loss of myelinated fibres. In lesions made adjacent to the DRG there was a signifi cantly higher MIB-1 labelling on the treated side as compared to the sham-t reated side. An RF lesion inside the DRG destroys myelinated Fibres. A lesi on adjacent to the DRG increases MIB-1 activity, indicating proliferation a nd regeneration after 2 weeks, despite the fact that the lesion was made ou tside the ganglion. (C) 2001 European Federation of Chapters of the Interna tional Association for the Study of Pain.