Faculty Bibliography

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

Introduction As most of the dorsal root ganglion neurostimulation (DRG-SCS) leads are placed in the lumbar spine to treat a variety of chronic pain syndromes, the accepted practice of securing the lead in the lumbar foramen is achieved by forming an 'S' tension loop with the lead inside the epidural space. Tension loop placement reduced the need for the placement of an anchor during permanent implant and a tunneled epidural catheter technique is often used to get the leads to the pocket rather than an incision and anchoring (1). This technique is optimal for less mobile segments of the lumbar spine however as utility of DRG SCS expands to upper lumbar/thoracic regions, concerns regarding migration of leads with a larger distance to travel to the generator and in more mobile parts of the lumbar spine have arisen. Objective To identify migration risk using certain implantation techniques of dorsal root ganglion stimulation at the upper lumbar and lower thoracic regions and to present our DRG-SCS lead anchoring technique to maximize the infrapedicular lead positional stability. Results Two recent papers for the placement of L2 DRG leads for low back pain showed lead migration in 4/12 and 4/15 implants (2,3). Our practice has recently performed two case series of 17 patients each, which had 31 separate patients (3 overlap); we experienced a total of 5 lead migrations out of 31 implants at the T12 level, all of which required revision (4). All migrations were found to be retrograde into the epidural space and one lead migrated out of the epidural space completely. Our implant technique was modified to make a midline incision with anchoring of the leads in the midline. Over 6 months (14 implants) no migrations have been noted as of yet with the anchoring technique. Of the total 13 migrations only one patient did not wish to have the stimulator revised. A relevant migration rate was noted by both Kallewaard et al. (2,4) and our studies and implant techniques were subsequently modified. Multiple factors may play a role in causing migration including the distance travelled from the upper lumbar/lower thoracic spine to generator site, the rotational torque of the thoracolumbar junction, and the improved pain control and degree of disability in these patients leading to more activity. Our group uses a 3 cm incision in the midline (right) after the leads were placed in the usual fashion using 'S' loops. After dissection to the fascia and hemostasis is obtained, the tuohy needle is taken back to the skin and the tuohy needle is advanced to drive the lead into the incision (Figure). Once the lead is in the incision, forceps are used to pull the free end of the lead through the tuohy needle and into the incision site. The tuohy needle is then removed. The Abbot DRG anchor is then placed around the lead and anchored to the fascia with 2.0 Ethibond sutures. This is repeated on the contralateral side if needed, and leads from the level above or below can be driven into the midline incision and anchored if needed. Tunneling to the pocket is performed in the usual fashion with the tunneling device. The Kallewaard group now anchors leads using the traditional Abbot DCSCS anchors with individual incisions at the lead site. Discussion * DRG neurostimulation at the upper lumbar and lower thoracic spine is proving to be an effective therapy to reduce pain for RSD/CRPS as well as truncal pain syndromes including axial low back pain. An increased rate of migration, 13 out of 58 implants in leads between the T12-L3 levels, may be secondary to increased truncal mobility, longer distance from the epidural space lead entry to the pocket, an increase in function and disability leading to more activity, as well as other potential reasons. In our 31 patients, initially the same technique was used for all implantations, which included 'S' loops, no anchor or incision, and tunneled epidural catheter technique to tunnel leads to the pocket. After our first noted migration we changed the technique to using 'S' loops in the epidural space, making a small midline incision, driving the leads to the incision, and anchoring leads with anchors provided in the DRG lead kit (described). As our results are at 9 months thus far with zero migrations, it appears anchoring upper lumbar and lower thoracic DRG leads may be vital to decrease the odds of migration either using the described technique or a two incision technique over the lead puncture sites. The improvements in migration rates with anchoring are consistent with those found by the Kallewaard group

Chronic neuropathic pain is often refractory to conventional medical treatments and leads to significant disability and socio-economic burden. Dorsal root ganglion (DRG) stimulation has recently emerged as a treatment for persistent neuropathic pain, but creating a strain relief loop on the S1 level has thus far been a challenging technical component of DRG lead placement. We describe a refined technique for strain relief loop formation on the S1 level using a transforaminal approach that we employed in a 45-year old patient with intractable foot pain. We successfully placed a strain relief loop in the sacral space in a predictable and easily reproducible manner using a transforaminal anchorless approach. The patient experienced a decrease in visual analogue pain score (85%), and improvement in function during the trial period, and proceeded with permanent implantation. The described sacral transforaminal strain relief loop formation technique appears to be a more reliable and predictable technique of DRG lead placement in the sacrum than those previously documented.