Theoretical aspects of radiofrequency lesions in the dorsal root entry zone.

The history and physical principles of radiofrequency (rf) lesion making are reviewed. The advantages of the rf lesion method are presented, with emphasis on its importance in small, critical regions such as the dorsal root entry zone (DREZ). The evolution and specifications of a satisfactory DREZ rf electrode are described. DREZ lesion sizes for this electrode at specific electrode tip temperatures were experimentally determined in animals and were used as a guide to determine acceptable clinical lesioning parameters. Emphasis is placed on lesion temperature monitoring and on the stability of electrode penetration into the spinal cord to achieve consistent and safe results.