Histopathological Appraisal of Carbon-dioxide Laser Dorsal Root Entry Zone (DREZ) Lesions in Primates

Dorsal Root Entry Zone (DREZ) thermocoagulation using radiofrequency has sucessfully been employed in the treatment of various deafferentation pain syndromes. The ability of surgical lasers to produce discrete lesions with precision has prompted their use in DREZ lesioning. The effects of carbon-dioxide laser induced DREZ lesions in the primate spinal cord were studied in the Bonnet monkey and the parameters necessary to produce a histologically ideal DREZ lesion were evaluated. Lesions were made with 10, 15 and 20 Watts power for pulse durations of 100 to 400 milliseconds at a constant beam spot size of 0.4 mm. It was found that histologically ideal lesions were produced with 20 Watts of power and a pulse duration of 300 milliseconds and with 15 Watts power and 400 millisecond pulse duration. The lesion lengths and widths at different parameters were also comparativly evaluated. The postulated mechanisms of deafferentation pain and the possible mode of action of DREZ lesions in management of pain are also reviewed.