Objectives: Spinal Cord Stimulation (SCS) is an effective treatment for chronic pain. How often pain remission follows SCS has not been evaluated. This is a retrospective analysis of patients who underwent an implantation of spinal cord stimulators for various chronic pain conditions. The objective of the study was to elucidate characteristics and features of patients with pain relief greater than 80% after one year of treatment. Methods: A total of 86 patients with thoracic SCS and 12-month follow-up data were identified. Patients were divided into a remission group (>80% improvement in Numeric Pain Rating Scale [NRS] pain scale), average responders (20-80% improvement) and a non-responder group (less than 20% improvement). These patient groups were compared via the following outcome measures: NRS, Oswestry Disability Index (ODI), Pain Catastrophizing Scale (PCS), McGill Pain Questionnaire (MPQ), and Insomnia Severity Index (ISI). Correlations with age, body mass index (BMI), tobacco and alcohol usage, patient satisfaction with SCS, disability status, and opioid usage were assessed. Results: Nineteen of 86 patients (22%) were remitters at one year follow-up, including 17 patients who had an NRS50 at that time. Upon analyzing the three patient groups (non-responders, average responders, and remitters), remitter patients showed the greatest change over the one-year post-operative period in ODI (F(2) 58.101, p<0.01) and PCS (F(2) = 7.607, p<0.01). Moreover, remission was less likely when the patients were on disability prior to implant (chi(2) (2) = 6.469, p<0.05) and on opioids pre-operatively (chi(2) (2) = 17.688, p < 0.01). Conclusions: Our study demonstrates a remission rate of 22% with SCS at one-year follow with a total of 19.8% of our total patient cohort having an NRS of 0. Greater decreases in PCS and ODI correlate with remission. Further, pre-operative disability and opioid use correlate with lower likelihood of remission.

BACKGROUND Chronic migraine (CM) is a highly debilitating disease, and many patients remain refractory to medicinal therapy. Given the convergent nature of neuronal networks in the ventral posteromedial nucleus (VPM) and the evidence of sensitization of pain circuitry in this disease, we hypothesize CM rats will have increased VPM neuronal firing, which can be attenuated using occipital nerve stimulation (ONS). OBJECTIVE To determine whether VPM firing frequency differs between CM and sham rats, and whether ONS significantly alters firing rates during the application of mechanical stimuli. METHODS Fourteen male Sprague-Dawley rats were infused with inflammatory media once daily through an epidural cannula for 2 wk to induce a CM state. Sham animals (n = 6) underwent cannula surgery but received no inflammatory media. ONS electrodes were implanted bilaterally and single-unit recordings were performed in the VPM of anesthetized rats during mechanical stimulation of the face and forepaw in the presence and absence of ONS. RESULTS CM rats had significantly higher neuronal firing rates (P < .001) and bursting activity (P < .01) in response to mechanical stimuli when compared to shams. ONS significantly reduced neuronal firing in the VPM of CM rats during the application of 0.8 g (P = .04), 4.0 g (P = .04), and 15.0 g (P = .02) Von Frey filaments. ONS reduced bursting activity in CM rats during the 4.0 and 15 g filaments (P < .05). No significant changes in bursting activity or firing frequency were noted in sham animals during ONS. CONCLUSION We demonstrate that neuronal spike frequencies and bursting activity in the VPM are increased in an animal model of CM compared to shams. Our results suggest that the mechanism of ONS may involve attenuation of neurons in the VPM of CM rats during the application of mechanical stimuli.

Invasive analgesic therapies provide an alternative to medical management of chronic pain. With the increasing incidence of chronic pain not only in the United States but worldwide, more therapies have evolved to address the growing need for pain relief options. These therapies include spinal injections, nerve blocks, radiofrequency ablation, neurostimulation, and intrathecal drug delivery.

INTRODUCTION:There is limited evidence regarding the precise location and connections of thermoregulatory centers in humans. We present two patients managed with subthalamic nucleus (STN) Deep Brain Stimulation (DBS) for motor fluctuations in PD that developed reproducible hyperhidrosis with high frequency DBS.OBJECTIVE:To describe the clinical features and analyze the location of the electrodes leading to autonomic activation in both patients.METHODS:We retrospectively assessed the anatomical localization, electrode programming settings and effects of unilateral STN DBS leading to hyperhidrosis.RESULTS:Unilateral stimulation of anterior and medially located contacts within the STN and zona incerta (Zi) caused bilateral, consistent, reproducible, and reversible sweating in our patients. Adequate control of motor symptoms without autonomic side effects was accomplished with alternative programming settings.CONCLUSION:Stimulation of the medial Zi and medial and anterior STN causes hyperhidrosis in a pattern similar to that described in primates and rats. We speculate that central autonomic fibers originating in the lateral hypothalamic area project laterally to the ventral/medial Zi and then to brainstem nuclei following an medial and posterior trajectory in relationship to STN.

BACKGROUND:Although thalamic deep brain stimulation (DBS) has been established as an effective therapy for refractory tremor in Parkinson's disease and essential tremor, reports investigating the efficacy of posterior subthalamic area (PSA) DBS for severe, debilitating tremors continue to emerge. However, questions regarding the optimal anatomical target, surgical approach, programming paradigms and effectiveness compared to other targets remain.OBJECTIVES:In this report, we aimed to review the current literature to assess different stereotactic techniques, anatomical considerations, adverse effects and stimulation settings in PSA DBS.METHODS:A comprehensive literature review was performed searching for articles discussing tremors and PSA stimulation. We performed a quantitative analysis comparing different DBS tremor targets.RESULTS:Tremor improvement is consistently documented in most reports with an average reduction in tremor of 79% depending on the specific tremor syndrome. Tremor benefit in patients with multiple sclerosis (MS) tremor was significantly higher than for other stimulation targets. Transient paresthesias, imbalance, dizziness and dysarthria are the most common side effects with PSA DBS.CONCLUSIONS:PSA DBS is an effective and safe treatment for tremor control and should be considered in patients with refractory tremors with associated cerebellar or dystonic features, proximal tremors and MS tremor.

Background: Up to 60% of Parkinson's disease (PD) patients suffer from low back pain (LBP) during the course of their disease. How LBP affects daily functional status and how to manage this aspect of PD has not been adequately explored. Methods: We examined 16 patients undergoing bilateral subthalamic nucleus deep brain stimulation (STN DBS) who met the inclusion criteria for moderate disability from LBP, as classified by the Oswestry Low Back Pain Disability Index (OLBPD). Results: Thirteen of 16 patients had attempted additional treatments for LBP, including medical management, massage, chiropractic, epidural steroid injections and/or surgery, with minimal relief. Following DBS, there was a significant improvement in the OLBPD at both the 6-month and 1-year time points (p < 0.02, p < 0.005, respectively). A mean improvement of 31.7% on the OLBPD score was noted. The Visual Analogue Scale (VAS) similarly decreased significantly at 1 year (p = 0.015). There was no correlation between the OLBPD score and other measures, including the Unified Parkinson's Disease Rating Scale (UPDRS), age and other nonmotor symptoms. Conclusion: Given the prevalent yet undertreated disability associated with LBP in PD, these results are novel in that they show that STN DBS has a significant positive effect on disability associated with LBP.

Background: At least 14% of Parkinson disease (PD) patients develop impulse control disorders (ICDs). The pathophysiology behind these behaviors and the impact of deep brain stimulation in a real-life setting remain unclear. Objectives: We prospectively examined the impact of bilateral subthalamic nucleus deep brain stimulation (STN-DBS) on ICDs in PD patients, as well as the relationship between impaired sensorimotor gaiting and impulsivity. Methods: Patients undergoing bilateral STN-DBS were assessed for ICDs preoperatively and 1-year postoperatively using a validated questionnaire (QUIP-RS). A subset of patients completed the Balloon Analogue Risk Task (BART) and auditory prepulse inhibition (PPI) testing. Results: Analysis revealed 12 patients had an improvement in score assessing ICDs (‘good responders'; p = 0.006) while 4 had a worse or stable score (‘poor responders'; p > 0.05). Good responders further exemplified a significant decrease in hypersexual behavior (p = 0.005) and binge eating (p = 0.01). Impaired PPI responses also significantly correlated with impulsivity in BART (r = -0.72, p = 0.044). Discussion: Following bilateral STN-DBS, 75% of our cohort had a reduction in ICDs, thus suggesting deep brain stimulation effectively manages ICDs in PD. The role of impaired PPI in predisposition to ICDs in PD warrants further investigation.

Introduction: High-frequency spinal cord stimulation (HFSCS) offers an alternative treatment for chronic refractory pain syndromes nonresponsive to traditional spinal cord stimulation (SCS). Following the conflicting findings of preliminary HFSCS clinical studies performed at 5-10 kHz, this study is the first to report successful clinical usage of 1-kHz frequency SCS with a standard generator. Patients: We used HFSCS in 2 patients who had inadequate relief with traditional SCS. Patient 1 was initially programmed at 40 Hz and a pulse width of 330 μs with bipolar stimulation. After multiple setting adjustments with inadequate pain relief, the patient was reprogrammed to HFSCS at settings of 1.15 kHz, 120 μs, and 5 V. Patient 2 was initially programmed at a frequency of 1.2 kHz and a pulse width of 120 μs, which she favored over the standard setting of 40 Hz and 390 μs pulse width. HFSCS provided optimal pain alleviation and increased quality of life for both patients. Conclusions: HFSCS at the frequency of 1 kHz offers a new tool for treatment of chronic pain in patients with traditional stimulation settings. Furthermore, most standard SCS batteries are capable of delivering stimulation in this frequency range.

BACKGROUND:High-frequency stimulation (HFS) has recently gained attention as an alternative to parameters used in traditional spinal cord stimulation (SCS). Because HFS is paresthesia free, the gate theory of pain control as a basis of SCS has been called into question. The mechanism of action of HFS remains unclear.OBJECTIVE:We compare the effects of HFS and traditional SCS on quantitative sensory testing parameters to provide insight into how HFS modulates the nervous system.METHODS:Using quantitative sensory testing, we measured thermal detection and pain thresholds and mechanical detection and pressure pain thresholds, as well as vibratory detection, in 20 SCS patients off stimulation (OFF), on traditional stimulation (ON) and on HFS in a randomized order.RESULTS:HFS significantly increased the mechanical detection threshold compared to OFF stimulation (p < 0.001) and traditional SCS (p = 0.01). Pressure pain detection and vibratory detection thresholds also significantly increased with HFS compared to ON states (p = 0.04 and p = 0.01, respectively). In addition, HFS significantly decreased 10- and 40-gram pinprick detection compared to OFF states (both p = 0.01). No significant differences between OFF, ON and HFS states were seen in thermal and thermal pain detection.CONCLUSION:HFS is a new means of modulating chronic pain. The mechanism by which HFS works seems to differ from that of traditional SCS, offering a new platform for innovative advancements in treatment and a greater potential to treat patients by customizing waveforms.