ECAP-controlled closed-loop versus open-loop SCS for the treatment of chronic pain: 36-month results of the EVOKE blinded randomized clinical trial.

INTRODUCTION: The evidence for spinal cord stimulation (SCS) has been criticized for the absence of blinded, parallel randomized controlled trials (RCTs) and limited evaluations of the long-term effects of SCS in RCTs. The aim of this study was to determine whether evoked compound action potential (ECAP)-controlled, closed-loop SCS (CL-SCS) is associated with better outcomes when compared with fixed-output, open-loop SCS (OL-SCS) 36 months following implant. METHODS: The EVOKE study was a multicenter, participant-blinded, investigator-blinded, and outcome assessor-blinded, randomized, controlled, parallel-arm clinical trial that compared ECAP-controlled CL-SCS with fixed-output OL-SCS. Participants with chronic, intractable back and leg pain refractory to conservative therapy were enrolled between January 2017 and February 2018, with follow-up through 36 months. The primary outcome was a reduction of at least 50% in overall back and leg pain. Holistic treatment response, a composite outcome including pain intensity, physical and emotional functioning, sleep, and health-related quality of life, and objective neural activation was also assessed. RESULTS: At 36 months, more CL-SCS than OL-SCS participants reported ≥50% reduction (CL-SCS=77.6%, OL-SCS=49.3%; difference: 28.4%, 95% CI 12.8% to 43.9%, p<0.001) and ≥80% reduction (CL-SCS=49.3%, OL-SCS=31.3%; difference: 17.9, 95% CI 1.6% to 34.2%, p=0.032) in overall back and leg pain intensity. Clinically meaningful improvements from baseline were observed at 36 months in both CL-SCS and OL-SCS groups in all other patient-reported outcomes with greater levels of improvement with CL-SCS. A greater proportion of patients with CL-SCS were holistic treatment responders at 36-month follow-up (44.8% vs 28.4%), with a greater cumulative responder score for CL-SCS patients. Greater neural activation and accuracy were observed with CL-SCS. There were no differences between CL-SCS and OL-SCS groups in adverse events. No explants due to loss of efficacy were observed in the CL-SCS group. CONCLUSION: This long-term evaluation with objective measurement of SCS therapy demonstrated that ECAP-controlled CL-SCS resulted in sustained, durable pain relief and superior holistic treatment response through 36 months. Greater neural activation and increased accuracy of therapy delivery were observed with ECAP-controlled CL-SCS than OL-SCS. TRIAL REGISTRATION NUMBER: NCT02924129.

DRG FOCUS: A Multicenter Study Evaluating Dorsal Root Ganglion Stimulation and Predictors for Trial Success.

INTRODUCTION: Dorsal root ganglion stimulation (DRGS) is a powerful tool in the treatment of chronic, neuropathic pain. The premise of DRGS is similar to that of conventional spinal cord stimulation (cSCS), however, there is more variability in how it can be utilized. While it is this variability that likely gives it its versatility, DRGS is not as straightforward to implement as cSCS. The purpose of this study was to assess the efficacy of DRGS on a broad number of diagnoses, determine which dorsal root ganglia were associated with better outcomes for particular body parts/diagnoses, and evaluate what factors/parameters were associated with higher rates of trial success. METHODS: This is a physician initiated, multicenter retrospective registry of 217 patients trialed with DRGS. Data were collected via an online questionnaire that assessed specifics regarding the patient's pain, distribution, size, and response to treatment. The data were analyzed to see if there were certain diagnoses and/or parameters that were more or less associated with trial success. RESULTS: DRGS was found to be an effective treatment in all diagnoses evaluated within this study, most of which had statistically significant improvements in pain. The most important predictor of trial success was the amount of painful area covered by paresthesias during the programing phase. The number of leads utilized had a direct and indirect impact on trial success. Pain in the distribution of a specific peripheral nerve responded best and there was no statistical difference based on what body part was being treated. CONCLUSION: DRGS can be an effective treatment for a variety of neuropathic pain syndromes, in addition to CRPS. It is recommended that a minimum of 2 leads should be utilized per area being treated. In addition, this therapy was shown to be equally efficacious in any body part/region so long as the area being treated is focal and not widespread.

Dysgeusia in deep brain stimulation for essential tremor.

Dysgeusia, or foul taste, is a rarely reported side effect in patients who have undergone deep brain stimulation (DBS) in the thalamus for essential tremor. This retrospective study evaluated the incidence, nature, neurophysiological and anatomical location of dysgeusia following DBS. Of 52 patients who had undergone DBS for essential tremor, eight (15%) reported dysgeusia, which was described as a "metallic," "sour," "foul," or "cold" taste in the mouth. Dysgeusia was separate and distinguishable from paresthesia. Dysgeusia was more frequently reported with bilateral than unilateral DBS implants (6 of 27 (22%) vs. 2 of 25 (8%) patients, respectively). The anatomical locations of the contacts causing dysgeusia were measured on postoperative MRI, and compared to those from seven control patients who did not experience dysgeusia after receiving bilateral DBS implants. Leads causing dysgeusia were more posterior than non-dysgeusia-associated leads (4.5 ±â€¯1.2 vs. 5.7 ±â€¯1.8 mm anterior to the posterior commissure, respectively, P < .001). Intraoperative microelectrode recording indicated that these contacts were in the sensory region of the thalamus. Intraoperative testing found that low sensory threshold for paresthesia predicted the development of dysgeusia postoperatively (1.5 ±â€¯0.5 V vs. 3.3 ±â€¯1.9 V; P < .05). These data indicate that taste perception can be altered in the human through DBS, with posterior leads likely within the sensory region of the thalamus. Dysgeusia can be reduced by changing stimulation parameters, or surgical revision of the lead.

The Neurostimulation Appropriateness Consensus Committee (NACC): Recommendations on Bleeding and Coagulation Management in Neurostimulation Devices.

INTRODUCTION: The Neurostimulation Appropriateness Consensus Committee (NACC) was formed by the International Neuromodulation Society (INS) in 2012 to evaluate the evidence to reduce the risk of complications and improve the efficacy of neurostimulation. The first series of papers, published in 2014, focused on the general principles of appropriate practice in the surgical implantation of neurostimulation devices. The NACC was reconvened in 2014 to address specific patient care issues, including bleeding and coagulation. METHODS: The INS strives to improve patient care in an evidence-based fashion. The NACC members were appointed or recruited by the INS leadership for diverse expertise, including international clinical expertise in many areas of neurostimulation, evidence evaluation, and publication. The group developed best practices based on peer-reviewed evidence and, in the absence of specific evidence, on expert opinion. Recommendations were based on international evidence in accordance with guideline creation. CONCLUSIONS: The NACC has recommended specific measures to reduce the risk of bleeding and neurological injury secondary to impairment of coagulation in the setting of implantable neurostimulation devices in the spine, brain, and periphery.

Peripheral Nerve Stimulation for Pain in Extremities: An Update.

Pain in extremities may occur in a variety of central and peripheral neuropathic and nociceptive syndromes, some of which may respond to central neuromodulation procedures. Peripheral neuromodulation techniques, either as a stand-alone therapy or as an adjuvant to spinal cord stimulation, may be particularly effective when the pain is localized to a part of a single extremity or when the source of the pain is related to the malfunction of a known peripheral nerve. Further, peripheral neuromodulation is used to treat disorders in which central simulation fails to provide discrete therapeutic paresthesia. Despite the fact that there are only a few neuromodulatory devices designed specifically for the periphery, clinical experiences are growing, and here we provide a clinical update on use of peripheral nerve stimulation (PNS) in management of chronic pain in extremities. Historical PNS strategies and innovative methods are reviewed and highlighted in this chapter. With the upcoming technological advances and new stimulation paradigms, along with clear updated guidelines statements, the utilization of PNS will likely continue to increase and improve the management of chronic pain syndromes in the extremities. The potential success of the novel devices specifically designed to target the peripheral nervous system is expected to positively impact and promote the use of PNS in treatment of chronic pain.