Effectiveness of dorsal root ganglion stimulation and dorsal column spinal cord stimulation in a model of experimental painful diabetic polyneuropathy

Aims Conventional dorsal root ganglion stimulation (DRGS) is known to achieve better pain-paresthesia overlap of difficult-to-reach areas like the feet compared to dorsal column spinal cord stimulation (SCS). As in painful diabetic polyneuropathy (PDPN) pain is mostly present in the feet, we hypothesized that DRGS is more effective in relieving pain in PDPN when compared to SCS. Methods Diabetes was induced in female Sprague-Dawley rats with an intraperitoneal injection of 65 mg/kg of streptozotocin (STZ; n = 48). Rats with a significant decrease in mechanical paw withdrawal response to von Frey filaments 4 weeks after injection were implanted with DRGS electrodes (n = 18). Rats were assigned to DRGS (n = 11) or sham-DRGS (n = 7). Mechanical paw withdrawal thresholds (WT, measured in grams) in response to DRGS (50 Hz, 0.18 +/- 0.05 mA) were assessed with von Frey testing. The results of the experiments on these animals were compared to the results of a previous study using exactly the same model on PDPN animals selected for SCS (n = 8) (40-50 Hz, 0.19 +/- 0.01 mA) and sham-SCS (n = 3). Results In the SCS group, the log(10) (10 000 x 50% WT) increased from 4910 to 5211 at t = 15 minutes (P <0.05) and 5264 at t = 30 minutes (P = 0.11). In the DRGS group, the log(10) (10,000 x 50% WT) increased from 4376 to 4809 at t = 15 minutes (P <0.01) and 5042 at t = 30 minutes (P <0.01). Both DRGS and SCS induced a similar and complete reversal of mechanical hypersensitivity. After cessation of stimulation (t = 60), the return of the log(10) (10 000 x 50% WT) response was significantly faster with DRGS than that of SCS (P <0.05). Conclusions We conclude that conventional DRGS is as effective as SCS in reduction of PDPN-associated mechanical hypersensitivity in STZ-induced diabetic rats. The wash-in effect of DRGS and SCS was similar, but DRGS showed a faster washout course. Long-term efficacy should be studied in future animal research.