Evaluation of laser and radiofrequency induced dorsal root entry zone lesion for pain control in rats.

BACKGROUND

Dorsal root entry zone (DREZ) lesions have been believed to be effective for control of intractable pain. These lesions are usually made using radiofrequency (RF) technique. Theoretically, laser can provide very fast, precise, reproducible and easy control of photothermal effect, possibly achieving better pain control than RF. The objective here was to learn more about the effect of pain control among the RF, carbon dioxide (CO2) laser and potassium titanyl phosphate (KTP) laser in rats.

METHODS

The adult rat was anesthetized and the dorsal spinal cord from C5 to T1 was exposed under a microscope. The DREZ lesions were created in each group of eight including sham, RF thermocoagulation, CO2 laser and KTP laser. The latency of pain withdrawal in the fore-paw by a hot-plate test was recorded before the DREZ lesions and three weeks afterward.

RESULTS

The data showed that RF, CO2 and KTP laser could significantly reduce pain in rats (p < 0.05, one-way ANOVA and Dunnett's test). Latencies of pain withdrawal in the fore-paw by the hot-plate test before, and three weeks after, DREZ lesions were 13.9 +/- 1.4 sec and 65.2 +/- 4.9 sec in the RF group, 15.9 +/- 1.4 sec and 59.0 +/- 5.9 sec in the CO2 laser group, and 14.1 +/- 0.9 sec and 64.8 +/- 5.7 sec in the KTP group, respectively.

CONCLUSIONS

The density of opioid receptor in DREZ lesions cord showed no significant change three weeks after operation in the sham and CO2 laser groups. It was concluded that DREZ lesions caused by RF, CO2 laser and KTP laser can achieve pain control significantly in the rats. The effect of KTP laser was close to RF, followed by CO2 laser.