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Background Dorsal root ganglion stimulation (DRG‐S) is used as a treatment for chronic low‐back pain (CLBP), although its underlying mechanisms remain elusive. CLBP patients have been found to have reduced mechanoreceptive perception, reduced endogenous analgesia, as well as deep‐tissue hyperalgesia when compared with healthy controls. Using quantitative sensory testing (QST), we studied if DRG‐S in CLBP patients results in changes in pain processing. Methods Quantitative sensory testing was performed in patients before trial implantation of a DRG‐S system for CLBP and just before the trial lead removal or at 1‐month follow‐up after the permanent implant. We determined the pressure pain threshold (PPT) and mechanical detection threshold (MDT) at the most painful lower‐back location. PPT was also measured on the contralateral shoulder as a control. We obtained a measure of endogenous inhibitory pain modulation using conditioned pain modulation (CPM). Results We enrolled 11 patients (60 ± 16 years). Pain decreased from 8.5 ± 1.0 at baseline to 2.0 ± 1.5 on a 0‐10 numerical rating scale with DRG‐S (P < 0.01). From baseline to with DRG‐S, PPT on the most painful location on the low back increased from 28.7 ± 13.6 to 43.4 ± 17.2 N/cm2 (P < 0.01). MDT on the same location decreased from 8.1 ± 10.4 to 3.4 ± 4.7 mN (P = 0.07). PPT on the control location and CPM did not change significantly. Conclusions Our results suggest that DRG‐S in CLBP patients reduces deep‐tissue hyperalgesia in the low back, while improving mechanoreceptive perception. These changes in both neuropathic and nociceptive components of CLBP were accompanied by clinical improvements in pain and function.

Dorsal root ganglion stimulation (DRG-S) is a form of neuromodulation that can target specific dermatomes to obtain better coverage of the distal extremity. Previously proposed mechanisms of action for DRG-S focused on the dorsal root ganglion (DRG) itself, without consideration of orthodromic effects in the dorsal horn and antidromic effects on the nerve root and sympathetic chain. Diabetic peripheral neuropathy (DPN) is an axonal neuropathy that affects around half of all patients with diabetes mellitus, causing severe pain and sensory impairment in the distal extremities. We present a case of a patient with DPN in both feet, in addition to low back pain, who underwent a DRG-S trial with right T12 and S1 leads. The trial was performed unilaterally for seven days, allowing the patient to compare the treated versus the untreated (left) side. Pain, disability, general health status, and quality of life measures improved significantly. In addition to the significant pain relief in the low back and feet, the patient had near resolution of other DPN-related symptoms, including numbness, bluish discoloration, and allodynia of both feet. He also demonstrated functional and psychological benefits with only a single-sided lead. Overall, the placement of unilateral T12 and S1 DRG-S leads resulted in symmetric improvement of DPN symptoms. A possible mechanism of action is antidromic propagation of action potential signaling into the sympathetic chain to a central ganglion and then to the contralateral sympathetic chain. Given the DRG's ability to directly affect afferent sympathetic fibers with low-frequency stimulation, DRG-S may be an effective neuromodulatory treatment for DPN.

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Dorsal root ganglion stimulation (DRG-S) has shown promise as a treatment for low back pain. The traditional anterograde placement of DRG-S leads can be challenging in patients with anatomical changes from prior back surgery. We describe an “outside-in” placement technique of DRG-S leads in 4 patients with histories of multiple lumbar surgeries, which made the traditional anterograde placement not feasible. At long-term follow-up, the patients experienced substantial pain relief and improvement in quality of life, with no complications. The outside-in lead placement technique may be an efficacious alternative to the traditional techniques in patients with anomalous anatomy from prior surgery.

Introduction Dorsal root ganglion stimulation (DRG‐S) has recently emerged as a novel therapy in neuromodulation that demonstrated a higher rate of success than spinal cord stimulation (SCS) in a prospective, head‐to‐head randomized comparative trial to treat complex regional pain syndrome (CRPS) and causalgia. In contrast to SCS, DRG‐S also shows promise in treating conditions that are not purely neuropathic such as axial low back pain, which has a prominent nociplastic pain component. It is not known to what extent the effectiveness of DRG‐S for such indications is due to effective treatment of the neuropathic pain component versus the effects of DRG‐S on mechanical pain. Although rarely studied, reporting outcomes of DRG‐S to treat predominantly mechanical/nociceptive pain may help point toward expanding the utility of this therapy. Here, we present five cases of refractory mechanical pain treated with DRG‐S. Methods A retrospective analysis of all patients who underwent a successful DRG‐S trial and implant between September 2017 and September 2021 at our institute was performed. Patients who had intractable joint pain without strong evidence of neuropathic pain were included in this case series. The Budapest criteria for CRPS, the Douleur Neuropathique 4 Questions (DN4) survey, or a definable nerve injury were used to determine the presence of neuropathic pain. Baseline assessments for pain (Numeric Rating Scale [NRS]), function (Oswestry Disability Index [ODI]), quality of life (EuroQol‐5 Dimension [EQ‐5D]), and other applicable joint surveys were extracted from pre‐trial baseline and follow‐up appointments. Results Five patients were identified and included. Patient diagnoses consisted of refractory joint pain of the hip, knee, or ankle. Mean NRS pain scores improved by 74% from 9.2 at baseline to 2.4 at the last follow‐up (mean = 28 months post‐implant). From baseline to the last follow‐up, mean ODI scores improved by 65% from 66 to 23 and EQ‐5D scores more than doubled from an average of 0.371 to 0.797. Conclusion This clinical report illustrates the potential utility DRG‐S has in treating pain that clinically presents as predominantly refractory mechanical joint pain without a significant neuropathic component. The physiological reasons for our observations may be that DRG‐S is able to directly influence the conduction of nociceptive signaling at the DRG and within the spinal cord. Further investigations are warranted to determine if DRG‐S is a potential treatment option for chronic mechanical pain.