Faculty Bibliography

BACKGROUND:The sympathetic nervous system (SNS) is important in the regulation of perfusion. Dorsal root ganglion stimulation (DRG-S) modulates sympathetic tone and is approved to treat complex regional pain syndrome, a disorder related to SNS dysfunction. We herein present 3 cases of DRG-S therapy to improve blood flow and symptoms of ischemia in peripheral arterial disease (PAD). METHODS:Patient 1 is a 44-year-old female with dry gangrene of the third and fourth digits of her right hand due to Raynaud's syndrome who was scheduled for amputation of the affected digits. DRG-S leads were placed at the right C6, 7, and 8 DRG. Pulse volume recordings (PVR) were measured at baseline and after DRG-S. Patient 2 is a 55-year-old female with a non-healing ulcer of her left foot secondary to PAD scheduled for a below the knee amputation who underwent a DRG-S trial with leads placed at the left L4 and L5 DRG followed by a spinal cord stimulation trial with leads placed at the T9-T10 spinal levels for comparison. Transcutaneous oximetry (TcPO2) was measured at baseline and after 3 days of each therapy. Patient 3 is a 69-year-old female with persistent left foot pain at rest secondary to PAD with DRG-S leads placed at the left L4 and S1 levels. RESULTS:All 3 patients experienced a significant reduction in pain with DRG-S, along with improvements in blood flow of the involved extremities, avoiding or limiting amputation. PVR improved dramatically with DRG-S in patient 1. A greater improvement in TcPO2 was seen with the DRG-S trial compared to spinal cord stimulation trial in patient 2. Patient 3 experienced an increase in walking distance and demonstrated long term efficacy and limb salvage at 32 months postimplantation. CONCLUSIONS:Modulation of SNS output from DRG-S through orthodromic and antidromic autonomic pathways is likely responsible for improving blood flow. DRG-S may be a treatment option for PAD.

BACKGROUND:Dorsal root ganglion neurostimulation (DRG-S) is effective in treating various refractory chronic pain syndromes. In preclinical studies, DRG-S at very low frequencies (<5 Hz) reduces excitatory output in the superficial dorsal horn. Clinically, we have also observed the effectiveness of DRG-S at low frequencies. We conducted a case series to describe the effect of very low-frequency DRG-S stimulation on clinical outcomes. MATERIALS AND METHODS/METHODS:DRG-S for refractory low back pain was initiated at parameters consistent with published values. Thereafter, the stimulation frequency of DRG-S was reduced in a stepwise fashion to the lowest frequency that maintained pain relief. Pain intensity, disability, and general health status data were collected at baseline, prior to initiation of tapering, and at four weeks after each patient's lowest effective stimulation frequency was reached. RESULTS:After device activation (N = 20), DRG-S frequency was tapered from 16 to 4 Hz over a 4- to 17-week period, reducing charge-per-second by nearly two-thirds. Even so, pain relief was maintained at more than 75%, with consistent findings in the other measures. CONCLUSION/CONCLUSIONS:DRG-S may have utility in treating chronic pain at lower stimulation frequencies than previously recognized. We have previously theorized that the mechanism of action may involve preferential recruitment of low-threshold mechanoreceptor fibers via the endogenous opioid system. Of clinical relevance, lower frequency stimulation maintains DRG-S efficacy regarding improvements in pain, disability, and quality of life. It can extend battery life and may potentially lead to the development of smaller implantable pulse generators.

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 to healthy controls. Using quantitative sensory testing (QST), we studied if DRG-S in CLBP patients results in changes in pain processing. METHODS:QST was performed in patients before trial implantation of a DRG-S system for CLBP and just before the trial lead removal or at one-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:(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.

BACKGROUND:Dorsal root ganglion stimulation (DRG-S) is a novel approach to treat chronic pain. Lead placement at L2 has been reported to be an effective treatment for axial low back pain (LBP) primarily of discogenic etiology. We have recently shown, in a diverse cohort including cases of multilevel instrumentation following extensive prior back surgeries, that DRG-S lead placement at T12 is another promising target. Local effects at the T12 DRG, alone, are insufficient to explain these results. MATERIALS AND METHODS/METHODS:We performed a literature review to explore the mechanisms of LBP relief with T12 DRG-S. FINDINGS/RESULTS:Branches of individual spinal nerve roots innervate facet joints and posterior spinal structures, while the discs and anterior vertebrae are carried via L2, and converge in the dorsal horn (DH) of the spinal cord at T8-T9. The T12 nerve root contains cutaneous afferents from the low back and enters the DH of the spinal cord at T10. Low back Aδ and C-fibers then ascend via Lissauer's tract (LT) to T8-T9, converging with other low back afferents. DRG-S at T12, then, results in inhibition of the converged low back fibers via endorphin-mediated and GABAergic frequency-dependent mechanisms. Therefore, T12 lead placement may be the optimal location for DRG-S to treat LBP.

We present 4 cases of dorsal root ganglion stimulation lead fracture. In these cases, the surgical technique involved (1) traversing fascial layers for placement of leads via a Tuohy needle in the upper low back, (2) subcutaneous tunneling from the implantable pulse generator site to the lead puncture site without dissecting below the superficial fascial plane at the puncture site, and (3) connection of the lead/extension with the generator. All fractures occurred adjacent to the original lead puncture site. These cases suggest lead entrapment within the membranous fascial plane, with tension on a thin lead, is a mechanism underlying lead fracture.

BACKGROUND:Radiofrequency ablation (RFA) of the medial branches of the dorsal rami has been reported to relieve facet joint-related back pain for 6 months to 1 year in 60% of patients. Although providing benefit in a significant proportion of patients, there remains a group of patients who do not experience any pain relief from RFA or experience only benefit from the ablation for a short period. Failure of RFA has been attributed to technical failure of coagulating the nerve or coagulation of a minimal section of the nerve, allowing for early reinnervation. Increasing the success rate and duration of relief may require techniques that increase the likelihood of successful nerve ablation over a relevant distance by maximizing lesion size. OBJECTIVES:The aim of this technical note is to detail a modification to the current commonly used lumbar medial branch radiofrequency (RF) denervation approach to increase lesion size. STUDY DESIGN:This is a technical report describing a novel two-needle approach to lumbar RF medial branch denervation. SETTING:Large private interventional pain management institute. METHODS:A dual needle placement of two 10-mm active tip RF cannulas separated by 6 mm is used to optimally contact the superior articular process (SAP) from its ventral to dorsal borders, which encompasses the anticipated course of the medial branch nerves. RESULTS:The described technique creates a lesion that we estimate to be 11.0-mm wide and 11.6-mm long along the course of the medial branch adjacent to the SAP ensuring adequate coverage and treatment. LIMITATIONS:This report does not encompass a systematic evaluation of the clinical safety and efficacy of the two-needle RFA approach. Future studies will have to assess the long-term efficacy and safety of the approach. CONCLUSIONS:The detailed two-needle approach to lumbar RF medial branch denervation appears to be promising in terms of projected treatment success by coagulating a large volume of tissue, in a cost- and time-efficient manner.

BACKGROUND:Dorsal root ganglion stimulation (DRG-S) has emerged as a treatment for complex regional pain syndrome (CRPS) of the lower extremities and recent small studies are demonstrating its potential efficacy in pain syndromes that are traditionally considered nociceptive in nature, such as axial low back pain. While improvements in neuromodulation technology have been substantial over the last decade, patients occasionally require additional interventional pain treatments after implantation of DRG-S systems for treatment of pain from other sources. Radiofrequency ablation (RFA) of medial branch nerves innervating the facet joints is an accepted therapy for pain arising from the facet joints. METHODS:We describe two cases from the same practice where we observed similar phenomena while performing a two-needle monopolar lumbar RFA in patients with a DRG-S system implanted with leads positioned bilaterally at the S1 DRGs. RESULTS:Initiation of RFA resulted in motor activation and discomfort in an S1 distribution in the legs in both individual cases. CONCLUSIONS:RFA can interfere with implanted DRG-S systems resulting in overstimulation with motor recruitment. Specific anatomical considerations and device settings that may prevent interference are discussed.

OBJECTIVE:To conduct a systematic literature review of dorsal root ganglion (DRG) stimulation for pain. DESIGN/METHODS:Grade the evidence for DRG stimulation. METHODS:An international, interdisciplinary work group conducted a literature search for DRG stimulation. Abstracts were reviewed to select studies for grading. General inclusion criteria were prospective trials (randomized controlled trials and observational studies) that were not part of a larger or previously reported group. Excluded studies were retrospective, too small, or existed only as abstracts. Studies were graded using the modified Interventional Pain Management Techniques-Quality Appraisal of Reliability and Risk of Bias Assessment, the Cochrane Collaborations Risk of Bias assessment, and the US Preventative Services Task Force level-of-evidence criteria. RESULTS:DRG stimulation has Level II evidence (moderate) based upon one high-quality pivotal randomized controlled trial and two lower-quality studies. CONCLUSIONS:Moderate-level evidence supports DRG stimulation for treating chronic focal neuropathic pain and complex regional pain syndrome.

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.