Faculty Bibliography

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.

Dorsal root ganglion (DRG) stimulation has recently emerged as a treatment for persistent neuropathic pain, but the permanent implantation of stimulator leads and the pulse generator can be difficult and is sometimes associated with complications. We used a single-incision approach to tunnel and implant the leads and pulse generator for DRG stimulation treatment in a patient suffering from intractable foot pain. At long-term follow-up, the patient experienced a decrease in pain intensity and improvement in function, without any complications. A single-incision implantation technique for DRG stimulator implantation may simplify implantation and decrease the risk of complications.

Coccydynia can be difficult to resolve with conventional treatment options. Dorsal root ganglion (DRG) stimulation has recently emerged as a treatment for chronic pain, but its application has not been described in the context of coccydynia. We used DRG stimulation treatment in a patient suffering from intractable coccyx pain. At long-term follow-up, the patient experienced a decrease in pain intensity and improvement in function, without any complications. DRG stimulation may be a treatment modality for coccydynia refractory to other approaches.

BACKGROUND: The current American Society of Regional Anesthesia (ASRA) guidelines recommend discontinuing anti-thrombotic therapy prior to any interventional spine procedures to decrease the incidence of bleeding complications. However, discontinuing anti-thrombotics may pose considerable danger in terms of cerebrovascular and cardiovascular events. Recent evidence suggests that some spinal interventions may still be performed safely with anti-thrombotics on board and some practitioners thus elect to continue certain anti-thrombotics for these procedures. OBJECTIVE: To assess the rate of adverse events in patients undergoing spine procedures that are currently classified by the ASRA guidelines as "low-to-intermediate bleeding risk," while being on continued anti-thrombotic therapy. STUDY DESIGN: Retrospective cohort study. SETTING: Interventional pain management practice. METHODS: A retrospective chart review was performed on patients who underwent low-to-intermediate risk spine procedures with variable anti-thrombotic medications continued throughout the course of treatment. RESULTS: Between October 2015 and May 2016, out of 2,204 patients who underwent low-to-intermediate risk spine procedures, we identified 490 patients on anti-thrombotic medications. These included aspirin (N = 275), P2Y12 inhibitors (N = 129), warfarin (N = 62), heparin (N = 10), factor Xa inhibitors (N = 55), and dipyridamole (N = 1). Forty-two patients were on multiple anti-thrombotics. Anti-thrombotics were continued throughout the procedure for 467 of 490 patients (88%). One bleeding complication (injection site bleeding) occurred in a patient that continued clopidogrel and aspirin during a lumbar radiofrequency ablation. We encountered no bleeding complications attributable to anti-thrombotics in the other 466 procedures in which anti-thrombotics were continued during lumbar (N = 260), thoracic (N = 18), and cervical (N = 40) medial branch injections, sacroiliac injections (N = 47), and during lumbar (N = 87) thoracic (N = 2), and cervical (N = 12) medial branch radiofrequency ablations. LIMITATIONS: The retrospective nature of the study and its reliance on electronic medical records are potential limitations. CONCLUSIONS: Continuing anti-thrombotic medication during medial branch and sacroiliac injections may be possible. KEY WORDS: Interventional pain management, thrombotic complications, hemostasis, anti-coagulation, bleeding complications.

Spinal cord stimulation is an effective treatment modality for refractory neuropathic pain conditions, but the placement of leads can be challenging due to unforeseen anatomical variations. We used a retrograde C7-T1 approach to place a lead at the bottom of T8 in a patient suffering from failed back surgery syndrome. We were able to achieve adequate stimulation in her lower back and legs, which resulted in significant reduction in pain intensity during the spinal cord stimulation trial. Cervical retrograde placement of leads may represent an alternative method for successful placement of percutaneous leads in patients with abnormal anatomy due to thoracic postsurgical changes.

BACKGROUND AND PURPOSE/OBJECTIVE:Changes in extracellular fluid osmolarity, which occur after tissue damage and disease, cause inflammation and maintain chronic inflammatory states by unknown mechanisms. Here, we investigated whether the osmosensitive channel, transient receptor potential vanilloid 4 (TRPV4), mediates inflammation to hypotonic stimuli by a neurogenic mechanism. EXPERIMENTAL APPROACH/METHODS:TRPV4 was localized in dorsal root ganglia (DRG) by immunofluorescence. The effects of TRPV4 agonists on release of pro-inflammatory neuropeptides from peripheral tissues and on inflammation were examined. KEY RESULTS/RESULTS:Immunoreactive TRPV4 was detected in DRG neurones innervating the mouse hindpaw, where it was co-expressed in some neurones with CGRP and substance P, mediators of neurogenic inflammation. Hypotonic solutions and 4alpha-phorbol 12,13-didecanoate, which activate TRPV4, stimulated neuropeptide release in urinary bladder and airways, sites of neurogenic inflammation. Intraplantar injection of hypotonic solutions and 4alpha-phorbol 12,13-didecanoate caused oedema and granulocyte recruitment. These effects were inhibited by a desensitizing dose of the neurotoxin capsaicin, antagonists of CGRP and substance P receptors, and TRPV4 gene knockdown or deletion. In contrast, antagonism of neuropeptide receptors and disruption of TRPV4 did not prevent this oedema. TRPV4 gene knockdown or deletion also markedly reduced oedema and granulocyte infiltration induced by intraplantar injection of formalin. CONCLUSIONS AND IMPLICATIONS/CONCLUSIONS:Activation of TRPV4 stimulates neuropeptide release from afferent nerves and induces neurogenic inflammation. This mechanism may mediate the generation and maintenance of inflammation after injury and during diseases, in which there are changes in extracellular osmolarity. Antagonism of TRPV4 may offer a therapeutic approach for inflammatory hyperalgesia and chronic inflammation.