Biophysics of Frequency-Dependent Variation in Paresthesia and Pain Relief during Spinal Cord Stimulation.

The neurophysiological effects of spinal cord stimulation (SCS) for chronic pain are poorly understood, resulting in inefficient failure-prone programming protocols and inadequate pain relief. Nonetheless, novel stimulation patterns are regularly introduced and adopted clinically. Traditionally, paresthetic sensation is considered necessary for pain relief, although novel paradigms provide analgesia without paresthesia. However, like pain relief, the neurophysiological underpinnings of SCS-induced paresthesia are unknown. Here, we paired biophysical modeling with clinical paresthesia thresholds (of both sexes) to investigate how stimulation frequency affects the neural response to SCS relevant to paresthesia and analgesia. Specifically, we modeled the dorsal column (DC) axonal response, dorsal column nucleus (DCN) synaptic transmission, conduction failure within DC fiber collaterals, and dorsal horn network output. Importantly, we found that high-frequency stimulation reduces DC fiber activation thresholds, which in turn accurately predicts clinical paresthesia perception thresholds. Furthermore, we show that high-frequency SCS produces asynchronous DC fiber spiking and ultimately asynchronous DCN output, offering a plausible biophysical basis for why high-frequency SCS is less comfortable and produces qualitatively different sensation than low-frequency stimulation. Finally, we demonstrate that the model dorsal horn network output is sensitive to SCS-inherent variations in spike timing, which could contribute to heterogeneous pain relief across patients. Importantly, we show that model DC fiber collaterals cannot reliably follow high-frequency stimulation, strongly affecting the network output and typically producing antinociceptive effects at high frequencies. Altogether, these findings clarify how SCS affects the nervous system and provide insight into the biophysics of paresthesia generation and pain relief.

A systematic review of procedural modalities in the treatment of notalgia paresthetica.

BACKGROUND: Notalgia paresthetica (NP) is a rare condition characterized by localized pain and pruritus of the upper back, associated with a distinct area of hyperpigmentation. Given the lack of standardized treatment and the uncertain efficacy of available options, applying procedural methods is of growing interest in treating NP. AIMS: We sought to comprehensively evaluate the role of procedural treatments for NP. METHODS: We systematically searched PubMed/Medline, Ovid Embase, and Web of Science until November 14th, 2023. We also performed a citation search to detect all relevant studies. Original clinical studies published in the English language were included. RESULTS: Out of 243 articles, sixteen studies have reported various procedural modalities, with or without pharmacological components, in treating NP. Pharmacological procedures, including injections of botulinum toxin, lidocaine, and corticosteroids, led to a level of improvement in case reports and case series. However, botulinum toxin did not show acceptable results in a clinical trial. Moreover, non-pharmacological procedures were as follows: physical therapy, exercise therapy, kinesiotherapy, acupuncture and dry needling, electrical muscle stimulation, surgical decompression, and phototherapy. These treatments result in significant symptom control in refractory cases. Physical therapy can be considered a first-line choice or an alternative in refractory cases. CONCLUSION: Procedural modalities are critical in the multidisciplinary approach to NP, especially for patients who are refractory to topical and oral treatments. Procedural modalities include a spectrum of options that can be applied based on the disease's symptoms and severity.

Investigation of the efficacy of two different laser types in the treatment of lower lip paresthesia after sagittal split ramus osteotomy.

Orthognathic surgery involves invasive and major surgical procedures commonly used to correct maxillofacial deformities. Bilateral sagittal split ramus osteotomy (BSSO) is often used to treat dentofacial anomalies related to the mandible, but it can result in various complications, the most common of which is inferior alveolar nerve damage. Nerve damage-induced paresthesia of the lower lip significantly affects patient comfort. Medical treatments such as steroids and vitamin B, low-level laser therapy (LLLT), and platelet-rich fibrin (PRF) can be used as supportive therapies for nerve regeneration after damage. This study aimed to investigate the effectiveness of two different types of lasers in treating lower lip paresthesia after BSSO. This clinical trial was a controlled, single-center, prospective, single-blind, randomized study. Thirty patients were included in the study and randomly assigned to three groups: Group I (laser GRR, n = 10) received transcutaneous and transmucosal GRR laser treatment, Group II (Epic10 laser, n = 10) received transmucosal and transcutaneous Epic10 laser treatment, and Group III (vitamin B, n = 10) received B-complex vitamin tablets orally once a day. Two-point and brush tests were performed six times at specific intervals, and a visual analog scale was used to evaluate pain and sensitivity. Both vitamin B and laser therapies accelerated nerve regeneration. The contribution of the laser groups to the healing rate was better than that of the vitamin B group. Although there was no statistically significant difference between the two laser groups, clinical observations indicated better results in the GRR laser group.

Defining the Boundaries of Patient Perception in Spinal Cord Stimulation Programming.

OBJECTIVES: Recent developments in spinal cord stimulation (SCS) programming have initiated new modalities of imperceptible stimulation. However, the boundaries of sensory perception are not well defined. The BEnchtop NEuromodulation Following endIng of Trial study aimed to create a map of perceptual threshold responses across a broad range of SCS parameters and programming to inform subperception therapy design. MATERIALS AND METHODS: This multicenter study was conducted at seven US sites. A total of 43 patients with low back and/or leg pain who completed a percutaneous commercial SCS trial were enrolled. Test stimulation was delivered through trial leads for approximately 90 minutes before removal. SCS parameters, including amplitude, frequency, pulse width (PW), electrode configuration, cycling, and multifrequency stimulation were varied during testing. Paresthesia threshold (PT), comfort level (CL), perceptual coverage area, and paresthesia quality (through patient selection of keywords) were collected. Differences were evaluated with analysis of variance followed by post hoc multiple comparisons using t-tests with Bonferroni correction. RESULTS: PT was primarily determined by PW and was insensitive to frequency for constant frequency stimulation (range: 20 Hz-10 kHz; F(1284) = 69.58, p < 0.0001). For all tests, CL was approximately 25% higher than PT. The dominant variable that influenced paresthesia quality was frequency. Sensations described as comfortable and tingling were most common for frequencies between 60 Hz and 2.4 kHz; unpleasant sensations were generally more common outside this range. Increasing distance between active electrodes from 7 mm to 14 mm, or cycling the SCS waveform at 1 Hz, decreased PT (p < 0.0001). Finally, PT for a low-frequency stimulus (ie, 60 Hz) was unaffected by mixing with a sub-PT high-frequency stimulus. CONCLUSIONS: In contrast to previous work investigating narrower ranges, PW primarily influenced PT, independently of frequency. Paresthesia quality was primarily influenced by pulse frequency. These findings advance our understanding of SCS therapy and may be used to improve future novel neuromodulation paradigms.

Postural Changes in Spinal Cord Stimulation Thresholds: Current and Voltage Sources.

OBJECTIVE: Spinal cord stimulation (SCS) thresholds are known to change with body position; however, these changes have not been fully characterized for both "constant-voltage" and "constant-current" pulse generators. This study aimed to evaluate and quantify changes in psychophysical thresholds resulting from postural changes that may affect both conventional paresthesia-based SCS and novel paresthesia-free SCS technologies. MATERIALS AND METHODS: We measured perceptual, usage, and discomfort thresholds in four body positions (prone, supine, sitting, standing) in 149 consecutive patients, with temporary lower thoracic percutaneous epidural electrodes placed for treating persistent low back and leg pain. We trialed 119 patients with constant-voltage stimulators and 30 patients with constant-current stimulators. RESULTS: Moving from supine to the sitting, standing, or prone positions caused all three thresholds (perceptual, usage, and discomfort) to increase by 22% to 34% for constant-voltage stimulators and by 44% to 82% for constant-current stimulators. Changing from a seated to a supine position caused stimulation to exceed discomfort threshold significantly more often for constant-current (87%) than for constant-voltage (63%) stimulators (p = 0.01). CONCLUSIONS: Posture-induced changes in SCS thresholds occurred consistently as patients moved from lying (supine or prone) to upright (standing or sitting) positions. These changes were more pronounced for constant-current than for constant-voltage pulse generators and more often led to stimulation-evoked discomfort. These observations are consistent with postural changes in spinal cord position measured in imaging studies, and with computer model predictions of neural recruitment for these different spinal cord positions. These observations have implications for the design, implantation, and clinical application of spinal cord stimulators, not only for conventional paresthesia-based SCS but also for paresthesia-free SCS.

Approach to diagnosis, evaluation, and treatment of generalized and nonlocal dysesthesia: A review.

Dysesthesia is an abnormal sensation in the skin that occurs in the absence of any extraordinary stimulus or other primary cutaneous disorders, excluding any delusions or tactile hallucinations. Clinicians have characterized dysesthesias to include sensations such as burning, tingling, pruritus, allodynia, hyperesthesia, or anesthesia. The etiology and pathogenesis of various generalized dysesthesias is largely unknown, though many dysesthesias have been associated with systemic pathologies including malignancy, infection, autoimmune disorders, and neuropathies. Dermatologists are often the first-line clinicians for patients presenting with such cutaneous findings, thus it is crucial for these physicians to be able to methodically work-up generalized dysesthesias to build a working differential diagnosis, follow up with key labs and/or imaging, and offer patients evidence-based treatment to relieve their symptoms. This broad literature review is an attempt to centralize key studies, cases, and series to help guide dermatologists in their assessment and evaluation of complaints of abnormal cutaneous sensations.

Epidural Laterality and Pain Relief With Burst Spinal Cord Stimulation.

INTRODUCTION: Burst spinal cord stimulation (SCS) can achieve excellent clinical reduction of pain, alongside improvements in function, quality of life, and related outcomes. Good outcomes likely depend on good lead placement, thereby enabling recruitment of the relevant neural targets. Several competing approaches exist for lead implantation, such as the use of single vs bilateral leads and leads lateralized vs placed at midline. The objective of this study was to examine the relationship between paresthesia locations and pain relief with burst SCS in a prospective double-blind crossover design. MATERIALS AND METHODS: All participants had bilateral back and leg pain, with more intense pain experienced on one side of the body. A trial SCS system was placed, during which brief intraoperative mapping with conventional stimulation was used to characterize paresthesia locations. Two programs for subperception burst SCS treatment were then applied for two days each, in random order: bilateral paresthesia coverage vs unilateral paresthesia coverage contralateral to the side of the body with more intense pain. Pain ratings (visual analog scale [VAS]) and pain reductions (scaling pain relief [SPR]) were reported for each. RESULTS: Of the 30 participants who completed the study, 24 (80%) had good pain relief with at least one program. A baseline VAS score of 8.75 was reduced to 5.98 with contralateral stimulation and to 2.88 with bilateral stimulation; with SPR, this equated to 31.25% and 67.50% improvement, respectively. The incremental benefit of bilateral stimulation over contralateral stimulation was statistically significant (p < 0.001). Of the 24 participants, 87.5% preferred bilateral stimulation, whereas 12.5% preferred unilateral stimulation. The six participants who failed the trial had no preference. DISCUSSION: When burst stimulation is delivered to spinal targets that can generate paresthesias contralateral to the side of worst pain, suboptimal therapy is achieved. Thus, attention to laterality and pain coverage is critical for successful therapy, and it may be important to carefully consider lead implantation techniques.

Combined Short-Pulse and Directional Deep Brain Stimulation of the Thalamic Ventral Intermediate Area for Essential Tremor.

OBJECTIVE: Novel deep brain stimulation (DBS) systems allow directional and short-pulse stimulation to potentially improve symptoms and reduce side effects. The aim of this study was to investigate the effect of short-pulse and directional stimulation, in addition to a combination of both, in the ventral intermediate thalamus (VIM)/posterior subthalamic area (PSA) on tremor and stimulation-induced side effects in patients with essential tremor. MATERIALS AND METHODS: We recruited 11 patients with essential tremor and VIM/PSA-DBS. Tremor severity (Fahn-Tolosa-Marin), ataxia (International Cooperative Ataxia Rating Scale), and paresthesia (visual analog scale) were assessed with conventional omnidirectional and directional stimulation with pulse width of 60 µs and 30 µs. RESULTS: All stimulation conditions reduced tremor. The best directional stimulation with 60 µs reduced more tremor than did most other stimulation settings. The best directional stimulation, regardless of pulse width, effectively reduced stimulation-induced ataxia compared with the conventional stimulation (ring 60 µs) or worst directional stimulation with 60 µs. All new stimulation modes reduced occurrence of paresthesia, but only the best directional stimulation with 30 µs attenuated paresthesia compared with the conventional stimulation (ring 60 µs) or worst directional stimulation with 60 µs. The best directional stimulation with 30 µs reduced tremor, ataxia, and paresthesia compared with conventional stimulation in most patients. Correlation analyses indicated that more anterior stimulation sites are associated with stronger ataxia reduction with directional 30 µs than with conventional 60 µs stimulation. CONCLUSION: Directional and short-pulse stimulation, and a combination of both, revealed beneficial effects on stimulation-induced adverse effects.

A Novel, Paresthesia-Free Spinal Cord Stimulation Waveform for Chronic Neuropathic Low Back Pain: Six-Month Results of a Prospective, Single-Arm, Dose-Response Study.

OBJECTIVES: The aim of this prospective, single-blinded, dose-response study was to evaluate the safety and efficacy of a novel, paresthesia-free (subperception) spinal cord stimulation (SCS) waveform designed to target dorsal horn dendrites for the treatment of chronic neuropathic low back pain (LBP). MATERIALS AND METHODS: Twenty-seven participants with chronic neuropathic LBP were implanted with a commercial SCS system after a successful trial of SCS therapy. Devices were programmed to deliver the investigative waveform (100 Hz, 1000 µs, T9/T10 bipole) at descending stimulation perception threshold amplitudes (80%, 60%, 40%). Programs were evaluated at six, ten, and 14 weeks, after which participants selected their preferred program, with more follow-up at 26 weeks (primary outcomes). Participants were blinded to the nature of the programming. Pain score (visual analog scale [VAS]), Brief Pain Inventory (BPI), quality of life (EQ-5D-5L), and health status (36-Item Short Form [SF-36]) were measured at baseline and follow-ups. Responder rate, treatment satisfaction, clinician global impression of change, and adverse events (AEs) also were evaluated. RESULTS: Mean (± SD) baseline VAS was 72.5 ± 11.2 mm. At 26 weeks (n = 26), mean change from baseline in VAS was -51.7 mm (95% CI, -60.7 to -42.7; p < 0.001), with 76.9% of participants reporting ≥50% VAS reduction, and 46.2% reporting ≥80% VAS reduction. BPI, EQ-5D-5L, and SF-36 scores were all statistically significantly improved at 26 weeks (p < 0.001), and 100% of participants were satisfied with their treatment. There were no unanticipated AEs related to the study intervention, device, or procedures. CONCLUSIONS: This novel, paresthesia-free stimulation waveform may be a safe and effective option for patients with chronic neuropathic LBP eligible for SCS therapy and is deliverable by all current commercial SCS systems. CLINICAL TRIAL REGISTRATION: This study is registered on anzctr.org.au with identifier ACTRN12618000647235.

Hyperbaric treatment deviations for U.S. Navy divers: Spinal DCS.

Introduction: The United States Navy (USN) developed and refined standardized oxygen treatment tables for diving injuries, but USN tables may not address all situations of spinal decompression sickness (DCS). We describe a detailed recompression treatment regimen that deviated from standard USN protocol for an active-duty USN diver with a severe, delayed presentation of spinal cord DCS. Case Report: A USN diver surfaced from his second of three dives on a standard Navy 'no-Decompression' Air SCUBA dive (Max depth 101 fsw utilizing a Navy Dive Computer) and developed mid-thoracic back pain, intense nausea, paresthesias of bilateral feet, and penile erection. Either not recognizing the con- stellation of symptoms as DCS and after resolution of the aforementioned symptoms, he completed the third planned dive (essentially an in-water recompression). Several hours later, he developed paresthesias and numbness of bilateral feet and legs and bowel incontinence. He presented for hyperbaric treatment twenty hours after surfacing from the final dive and was diagnosed with severe spinal DCS. Based on the severity of clinical presentation and delay to treatment, the initial and follow-on treatments were modified from standard USN protocol. MRI of the spine four days after initial presentation demonstrated a 2.2 cm lesion at the T4 vertebral level extending caudally. Follow-up examinations over two years demonstrated almost complete return of motor and sensory function; however, the patient continued to suffer fecal incontinence and demonstrated an abnormal post-void residual urinary volume. An atypical presenting symptom, a discussion of MRI findings, and clinical correlations to the syndrome of spinal DCS are discussed throughout treatment and long-term recovery of the patient.

Scalp dysaesthesia and lichen simplex chronicus: diagnostic and therapeutic update with literature review.

Scalp dysaesthesia, considered a variant of the cutaneous dysaesthesia syndrome, is characterized by chronic sensory symptoms, including pruritus, pain, burning and stinging in a well-defined location, without objective findings. Its aetiology is not well elucidated and treatment options are limited, thus it can be challenging and frustrating for both patient and physician. It can be associated with lichen simplex chronicus. In this paper, we review the literature on the pathogenetic factors, diagnostic methods and therapeutic options in the management of scalp dysaesthesia. Dissociation, cervical spine disease and muscle tension seem to be the most important pathogenetic factors. Trichoscopy, reflectance confocal microscopy and biopsy are all helpful for the diagnosis of the disease. Therapies include high-potency topical or intralesional corticosteroids, capsaicin and topical anaesthetics, sedative antihistamines, tricyclic antidepressants, transcutaneous electric nerve stimulation, botulinum toxin and vitamin B12.

Effect of Lead Position and Polarity on Paresthesia Coverage in Spinal Cord Stimulation Therapy: A Computational Study.

OBJECTIVES: The effect of lead placement and programming strategies on spinal cord stimulation (SCS) therapy has been widely studied; however, there is a need to optimize these parameters to favor dorsal column (DC) over dorsal root (DR) stimulation in complex pain treatment. This study aimed to determine the optimal lateral distance between two leads and the effect of transverse stimulation using a mathematical model. MATERIALS AND METHODS: A three-dimensional computational SCS and a nerve fiber model were used to determine the effect of the lateral distance between two leads at the same vertebral level T8 and the effect of the addition of anodes with two parallel leads at T8 and three different lateral distances on the model-based results (perception thresholds, activated DC fiber area and depth, and position of the first stimulated fiber). RESULTS: With two parallel leads programmed with symmetrical polarities, the maximal DC fiber area stimulated was found for a lateral distance of 5 mm. The results also show a higher preference for DR stimulation as the lateral distance increased. The addition of positive contacts at the same level of active contacts in the second lead produces a displacement of the first stimulated fiber laterally. CONCLUSIONS: A lateral distance of 5 mm shows a DC stimulated fiber area greater than when leads are placed contiguously. The addition of anodes creates an effect whereby the area of paresthesia is not displaced to the midline, but in the opposite direction. This may be useful when the leads are too close and stimulation of one of the sides is compromised.

Intermittent Dorsal Root Ganglion Stimulation Is as Efficacious as Standard Continuous Dosing in Treating Chronic Pain: Results From a Randomized Controlled Feasibility Trial.

INTRODUCTION: Dorsal root ganglion stimulation (DRG-S) is a form of neuromodulation used to treat chronic pain. A spinal cord stimulation (SCS) method with paresthesia-free waveform used in the dorsal columns, burst-SCS, recently demonstrated efficacy using intermittent stimulation, where stimulation is cycled on and off for set durations. Tonic SCS is a paresthesia-based therapy that is ineffective at sub-perception levels and when delivered in a cycled manner. DRG-S also uses a tonic waveform, yet unlike tonic SCS, it is effective at sub-perception levels. This study aimed to determine whether the cycling of stimulation at the DRG could maintain DRG-S efficacy. MATERIALS AND METHODS: This study followed a prospective, randomized, and balanced, double-blinded (assessor) protocol. Twenty DRG-S responders were randomized to a sequence of three programs for consecutive two-week intervals: continuous stimulation; 1 minute on:1 minute off; or 1 minute on:2 minutes off. The primary outcome of this study was change in pain ratings with the cycled programs compared with continuous stimulation. Secondary outcomes included changes in function and scores for quality of life, and stimulation program preference. RESULTS: Mean scores were similar at the end of each two-week stimulation program for Numerical Rating Scale pain (continuous = 2.9 ± 0.8, 1:1 on-off = 2.6 ± 0.7, and 1:2 on-off = 2.7 ± 0.7 cm, p = 0.39), disability (p = 0.72), and general health (p = 0.95). No clinically significant differences were found from the upper boundaries of the 95% confidence intervals of the mean difference in pain, disability, and general health for each intermittent stimulation program vs the continuous program. At the end of the study, the continuous stimulation, 1:1 on-off dosing, and 1:2 on-off dosing programs were preferred by a similar number of patients. CONCLUSIONS: Intermittent DRG-S produces comparable results to continuous stimulation over a two-week period. Intermittent delivery may extend battery life and facilitate a smaller implantable pulse generator.

Comparison of Paresthesia Mapping With Anatomic Placement in Burst Spinal Cord Stimulation: Long-Term Results of the Prospective, Multicenter, Randomized, Double-Blind, Crossover CRISP Study.

OBJECTIVES: Spinal cord stimulation (SCS) is an effective therapy for chronic intractable pain. Conventional SCS involves electrode placement based on intraoperative paresthesia mapping; however, newer paradigms like burst may allow for anatomic placement of leads. Here, for the first time, we report the one-year safety and efficacy of burst SCS delivered using a lead placed with conventional, paresthesia mapping, or anatomic placement approach in subjects with chronic low back pain (CLBP). MATERIALS AND METHODS: Subjects with CLBP were implanted with two leads. The first lead was placed to cross the T8/T9 disc and active contacts for this lead were chosen through paresthesia mapping. The second lead was placed at the T9/T10 spinal anatomic landmark. Subjects initially underwent a four-week, double-blinded, crossover trial with a two-week testing period with burst SCS delivered through each lead in a random order. At the end of trial period, subjects expressed their preference for one of the two leads. Subsequently, subjects received burst SCS with the preferred lead and were followed up at 3, 6, and 12 months. Pain intensity (visual analog scale), quality-of-life (EuroQol-5D instrument), and disability (Oswestry Disability Index) were evaluated at baseline and follow-up. RESULTS: Forty-three subjects successfully completed the trial. Twenty-one preferred the paresthesia mapping lead and 21 preferred the anatomic placement lead. Anatomic placement lead was activated in one subject who had no preference. The pain scores (for back and leg) significantly improved from baseline for both lead placement groups at all follow-up time points, with no significant between-group differences. CONCLUSIONS: This study demonstrated that equivalent clinical benefits could be achieved with burst SCS using either paresthesia mapping or anatomic landmark-based approaches for lead placement. Nonparesthesia-based approaches, such as anatomic landmark-based lead placement investigated here, have the potential to simplify implantation of SCS and improve current surgical practice.

Peripheral Nerve Stimulation: A New Treatment for Meralgia Paresthetica.

BACKGROUND: Meralgia paresthetica is a condition caused by entrapment of the lateral femoral cutaneous nerve that leads to paresthesia along the anterolateral portion of the thigh. Because of advancements in neuromodulation, peripheral nerve stimulation (PNS) has been considered a new treatment option for meralgia paresthetica. Newer PNS technology targets peripheral nerves directly yet in a minimally invasive manner. We report a case in which a PNS device provided more than 12 months of complete pain relief in a patient with meralgia paresthetica and helped the patient avoid a neurolysis procedure. CASE PRESENTATION: A 57-year-old male presented to clinic with a 6-year history of "painful numbness [and] burning" along the right lateral thigh. He rated his pain as 8 out of 10, which decreased to a rating of 2 out of 10 with the use of gabapentin, but unwanted side effects motivated him to seek alternative treatment. On the basis of his history, physical exam, and imaging results, he was diagnosed with meralgia paresthetica. He was offered neurolysis; however, after seeing a pain specialist, he agreed to the implantation of a SPRINT peripheral nerve stimulator. After the implantation procedure, his pain reduced to 0 out of 10, and his quality of life improved, with better sleep and less somnolence. The device was removed after 60 days, as planned. He continued to have complete resolution of pain at 12 months after the date of device implantation. CONCLUSION: With recent advancements, PNS can be used to treat meralgia paresthetica in an effective yet minimally invasive manner. As newer PNS technology becomes more familiar to physicians and pain specialists, it is likely to be used as a mainstay treatment for meralgia paresthetica.

Tactile stimulation programs in patients with hand dysesthesia after a peripheral nerve injury: A systematic review.

STUDY DESIGN: This is a systematic review performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses standards. INTRODUCTION: Diverse approaches based on tactile stimulation are used in hand rehabilitation settings to treat touch-evoked dysesthesias. However, there is a lack of literature synthesis on the description and the effectiveness of the various approaches based on tactile stimulation that can be used for treating hand dysesthesia after nerve injury. PURPOSE OF THE STUDY: The purpose of the study was to summarize the current evidence on tactile stimulation programs for managing touch-evoked hand dysesthesia due to nerve injury. METHODS: The search was carried out on Medline, Embase, CINAHL, and the Cochrane Library databases. The selected studies had to present patients with touch-evoked dysesthesia after nerve injury who were treated with tactile stimulation approaches to reduce pain. The methodological quality of the included studies was assessed using the methodological index for nonrandomized studies scale, as well as the risk of bias. RESULTS: Eleven studies met the inclusion criteria. These studies present tactile stimulation interventions that are heterogeneous relative to the target populations and the intervention itself (desensitization versus somatosensory rehabilitation method). Painful symptoms appear to diminish in patients with touch-evoked hand dysesthesia, regardless of the tactile stimulation program used. However, the included studies present significant risks of bias that limit the confidence in these results. DISCUSSION: The evidence does not unequivocally support the beneficial effects of tactile stimulation to treat touch-evoked hand dysesthesia. CONCLUSION: Future studies with more rigorous methodological designs, such as randomized controlled trials, are required to verify the potential benefits of these approaches.

Comparison of Paresthesia Mapping to Anatomical Placement in Burst Spinal Cord Stimulation: Initial Trial Results of the Prospective, Multicenter, Randomized, Double-Blinded, Crossover, CRISP Study.

INTRODUCTION: In this prospective, multicenter, double-blinded, randomized, crossover study, we compared the therapeutic efficacy of burst SCS delivered using a lead implanted with the paresthesia mapping approach to a lead implanted with an anatomic placement approach. MATERIALS AND METHODS: Subjects with chronic low back pain were implanted with two leads, one using paresthesia-mapping approach (PM) and the second using anatomical placement procedure (AP). Stimulation contacts were chosen using the standard intraoperative paresthesia-testing procedure for the paresthesia-mapped lead or an activated bipole overlapping the T9-T10 junction for the anatomical lead. Amplitude for either lead was selected such that no sensory percepts were generated. Subjects were assessed at baseline and after a trial period during which they tested each lead for two weeks in random order. Eligible subjects had the option to receive permanent implants using their preferred AP or PM approach at end-of-trial. RESULTS: Of the 53 subjects who completed both trial periods, 43 (81.1%) experienced at least 50% back pain relief with at least one lead. Nearly half of these (20; 46.5%) were profound responders who experienced at least 80% back pain relief with either leads. Primary and secondary outcomes, at the end of trial, showed significant improvements for both AP and PM leads from baseline yet were not significantly different from each other. DISCUSSION: The trial results of this study suggest that similar clinical outcomes can be achieved in burst SCS when performing lead placement either using paresthesia mapping or anatomical placement with imaging references.

Paresthesia-Free Dorsal Root Ganglion Stimulation: An ACCURATE Study Sub-Analysis.

INTRODUCTION: ACCURATE, a randomized controlled trial comparing dorsal root ganglion (DRG) stimulation to spinal cord stimulation, showed that DRG stimulation is a safe and effective therapy in individuals with lower extremity chronic pain due to complex regional pain syndrome (CRPS) type I or II. Investigators noted that DRG stimulation programming could be adjusted to minimize, or eliminate, the feeling of paresthesia while maintaining adequate pain relief. The present study explores treatment outcomes for DRG subjects who were paresthesia-free vs. those who experienced the sensation of paresthesia, as well as the factors that predicted paresthesia-free analgesia. METHODS: A retrospective analysis of therapy outcomes was conducted for 61 subjects in the ACCURATE study who received a permanent DRG neurostimulator. Outcomes of subjects who were paresthesia-free were compared to those who experienced paresthesia-present therapy at 1, 3, 6, 9, and 12-month follow-ups. Predictor variables for the presence or absence of paresthesias with DRG stimulation were also explored. RESULTS: The percentage of subjects with paresthesia-free pain relief increased from 16.4% at 1-month to 38.3% at 12-months. Paresthesia-free subjects generally had similar or better outcomes for pain severity, pain interference, quality of life, and mood state as subjects with paresthesia-present stimulation. Factors that increased the odds of a subject feeling paresthesia were higher stimulation amplitudes and frequencies, number of implanted leads, and younger age. CONCLUSIONS: Some DRG subjects achieved effective paresthesia-free analgesia in the ACCURATE trial. This supports the observation that paresthesia is not synonymous with pain relief or required for optimal analgesia with DRG stimulation.

Computational Study of the Effect of Electrode Polarity on Neural Activation Related to Paresthesia Coverage in Spinal Cord Stimulation Therapy.

OBJECTIVE: Using computer simulation, we investigated the effect of electrode polarity on neural activation in spinal cord stimulation and propose a new strategy to maximize the activating area in the dorsal column (DC) and, thus, paresthesia coverage in clinical practice. MATERIALS AND METHODS: A new three-dimensional spinal cord model at the T10 vertebral level was developed to simulate neural activation induced by the electric field distribution produced by different typical four-contact electrode polarities in single- and dual-lead stimulation. Our approach consisted of the combination of a finite element model of the spinal cord developed in COMSOL Multiphysics and a nerve fiber model implemented in MATLAB. Five evaluation parameters were evaluated, namely, the recruitment ratio, the perception and discomfort thresholds, and the activating area and depth. The results were compared quantitatively. RESULTS: The dual-guarded cathode presents the maximum activating area and depth in single- and dual-lead stimulation. However, the lowest value of the ratio between the perception threshold in DC and the perception threshold in the dorsal root (DR) is achieved when the guarded cathode is programmed. Although the two versions of bipolar polarity (namely bipolar 1 and bipolar 2) produce higher activating area and depth than the guarded cathode, they are suitable for producing DR stimulation. Similarly, dual-lead stimulation is likely to activate DR fibers because the electrodes are closer to these fibers. CONCLUSIONS: The results suggest that the activating area in the DC is maximized by using the dual-guarded cathode both in single- and dual-lead stimulation modes. However, DC nerve fibers are preferentially stimulated when the guarded cathode is used. According to these results, the new electrode programming strategy that we propose for clinical practice first uses the dual-guarded cathode, but, if the DR nerve fibers are activated, it then uses guarded cathode polarity.

Implanter's Integrated Information (I3) System: An Aid for Spinal Cord Stimulation Procedures.

OBJECTIVES: In spinal cord stimulation (SCS), the electrical stimulation of the spinal cord with an implanted lead evokes a tingling peripheral sensation known as paresthesias. Newer stimulation paradigms allow paresthesia-free treatment, but during the implantation of the lead, paresthesias must cover the painful area to achieve optimal treatment effect. The localization of the evoked paresthesias can be difficult to accurately describe for the patient, and furthermore depends on a complex and only partially predictable set of parameters that includes the anatomical localization and the programming of the electrical field. We aimed to optimize SCS implantation procedures by devising a way to aid the patient in making useful descriptions of the evoked paresthesias, then to visually convey the full set of information-anatomical position of the lead, programming parameters, and evoked paresthesias-directly to the implanting physician. MATERIALS AND METHODS: To aid the patient in making accurate descriptions of the evoked paresthesia, we use an app dedicated to creating pain drawings on a tablet. We used Chromecast and Apple TV to project the information from the pain drawing tablet and the programming device to two monitors placed in the implanter's field of vision, right next to the fluoroscopy monitor. RESULTS: The three monitors combined provide a direct visual representation of the dynamic dataset used during SCS implantation: Position, Programming, and Paresthesias, essentially creating the equivalent of the dashboard of a car. CONCLUSIONS: We present an Implanter's Integrated Information (I3) system; a simple, inexpensive solution for gathering, integrating, and conveying the complex set of information necessary for a successful SCS procedure.