Faculty Bibliography

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.

Introduction: Dorsal root ganglion neurostimulation (DRG-SCS) has been demonstrated to be effective in treating various refractory chronic pain syndromes and has shown promise recently for the treatment of discogenic low back pain (LBP) via L2 DRG lead placement. We previously performed T12 DRG-SCS in 17 consecutive patients with predominantly axial LBP. At an average of 8 months follow-up there was an average LBP relief of 81%. Improvements in physical and mental functioning, disability and quality of life far surpassed improvements seen in traditional DC-SCS. Based on these results in a patient population with diverse LBP etiology, T12 DRG may be the optimal location for DRG-SCS to cover the low back. Materials/Methods: A review of the literature was conducted to assess an anatomical and neurophysiological basis for T12 DRG-SCS in LBP treatment. Over 300 papers were full-text reviewed and more than 135 (>95% preclinical) were deemed relevant and included in a narrative review manuscript. The condensed findings of this manuscript are presented in this abstract.
Result(s): Discussion: DRG-SCS at the T12 level in our case series showed a high level of promise for the treatment of severe LBP. A literature review led us to hypothesize that the low back fibers leave their individual spinal levels and travel in Lissauer's tract. Inhibition of LBP occurs at the T8/9 level by the incoming cutaneous fibers of the T12 spinal nerve when they converge with the low back fibers through a mechanism similar to that seen in somatovisceral inhibition. T8-9 level is also the most common location for DC-SCS for LBP coverage, DRG-SCS at the T12 level may provide a more direct inhibition of the nerve fibers of the deep lumbar structures as compared to traditional SCS. A-delta and C fiber very low frequency stimulation (<20Hz) activating enkephalin mediated pre and post synaptic inhibition is likely mechanism for the inhibition of the pain signal.
Conclusion(s): Compared to traditional SCS, T12 DRG-SCS may provide a more effective inhibition of pain fibers conducting nociceptive, as well as neuropathic, nerve traffic. By using very low frequency stimulation, we are applying a low dose, targeted application of electrical current to achieve these results. Objectives 1. To apply results of 12 DRG-SCS case series to current literature to identify a potential mechanism of action. 2. Compared to conventional SCS, T12 DRG-SCS may be able to address both neuropathic and nociceptive elements of LBP more effectively. 3. Compare DRG-SCS MOA to other types of SCS