Faculty Bibliography

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) 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.

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.

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.

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.

BACKGROUND:Several pain management guidelines recommend regular urine drug testing (UDT) in patients who are being treated with chronic opioid analgesic therapy (COAT) to monitor compliance and improve safety. Guidelines also recommend more frequent testing in patients who are at high risk of adverse events related to COAT; however, there is no consensus on how to identify high-risk patients or on the testing frequency that should be used. Using previously described clinical risk factors for UDT results that are inconsistent with the prescribed COAT, we developed a web-based tool to adjust drug testing frequency in patients treated with COAT. OBJECTIVE:The objective of this study was to evaluate a risk stratification tool, the UDT Randomizer, to adjust UDT frequency in patients treated with COAT. METHODS:Patients were stratified using an algorithm based on readily available clinical risk factors into categories of presumed low, moderate, high, and high+ risk of presenting with UDT results inconsistent with the prescribed COAT. The algorithm was integrated in a website to facilitate adoption across practice sites. To test the performance of this algorithm, we performed a retrospective analysis of patients treated with COAT between June 2016 and June 2017. The primary outcome was compliance with the prescribed COAT as defined by UDT results consistent with the prescribed COAT. RESULTS:979 drug tests (867 UDT, 88.6%; 112 oral fluid testing, 11.4%) were performed in 320 patients. An inconsistent drug test result was registered in 76/979 tests (7.8%). The incidences of inconsistent test results across the risk tool categories were 7/160 (4.4%) in the low risk category, 32/349 (9.2%) in the moderate risk category, 28/338 (8.3%) in the high risk category, and 9/132 (6.8%) in the high+ risk category. Generalized estimating equation analysis demonstrated that the moderate risk (odds ratio (OR) 2.1, 95% CI 0.9-5.0; P=.10), high risk (OR 2.0, 95% CI 0.8-5.0; P=.14), and high risk+ (OR 2.0, 95% CI 0.7-5.6; P=.20) categories were associated with a nonsignificantly increased risk of inconsistency vs the low risk category. CONCLUSIONS:The developed tool stratified patients during individual visits into risk categories of presenting with drug testing results inconsistent with the prescribed COAT; the higher risk categories showed nonsignificantly higher risk compared to the low risk category. Further development of the tool with additional risk factors in a larger cohort may further clarify and enhance its performance.

Stimulation of the dorsal root ganglion (DRG-S) has been shown to be an efficacious treatment option for refractory neuropathic pain syndromes. However, placement of the percutaneous leads for trial implantation can be challenging in patients with prior spinal surgical interventions resulting in anatomical changes and adhesions. This technical report describes the transgrade placement of DRG-S leads in four patients with back pain surgery histories in whom secondary to specific anatomical pathologies the traditional anterograde placement of DRG-S leads was not feasible. In these patients we used a transgrade placement approach entering superior and contralateral to the target level of placement, resulting in uncomplicated and effective placement of DRG-S leads. Transgrade lead placement for DRG-S may be an efficacious alternative to traditional anterograde DRG lead placement in cases where interlaminar access below the level of the DRG is not available, or desirable. Further studies are needed to clarify the safety and applicability of this approach.

INTRODUCTION/BACKGROUND:Dorsal root ganglion stimulation (DRG-S) is a neuromodulation technique for treating neuropathic pain syndromes. Research has demonstrated DRG-S to be more effective than conventional SCS in treating RSD/CRPS, particularly of the lower extremities. Results from recent case series and prospective studies suggest that DRG-S may be effective in treatment of pain syndromes considered to have non-neuropathic components and characteristics (e.g. nociceptive). There have been multiple, small studies demonstrating efficacy of DRG-S for axial low back pain. There has, however, been no consensus regarding the best location for DRG lead placement in the treatment of low back pain. METHODS:Patients presenting with refractory low back pain in a private pain management practice were considered for DRG-S. Patients were provided a trial stimulator prior to potential implantation. Per standard practice, pain intensity, disability, general health status, and quality of life were followed using the visual analog scale (VAS), Oswestry Disability Index, EQ-5D index, and the SF-36 survey, respectively. Data were collected prior to implantation and at variable follow-ups after DRG-S initiation. RESULTS:Seventeen consecutive patients presented with predominantly axial low back pain with/without a secondary component of lower extremity pain. All were trialed and subsequently implanted for DRG-S. Leads were placed at T12 to target the low back. Stimulation levels were set very low, below that of which patients experienced paresthesias. Last follow-up times averaged 8.3 months. More than half of the patients experienced pain relief ≥80%, with an average low back pain relief of 78% at last follow-up. Additionally, substantial improvements in physical and mental functioning, disability, and quality of life were reported. CONCLUSIONS:T12 DRG-S can be an effective treatment for chronic axial low back pain. Stimulation results in reduced pain and disability, while improving quality of life. These outcomes can be achieved without paresthesias.