Block of peripheral pain response by high-frequency sinusoidal stimulation

Analysis of Variable Frequency Stimulation Sacral Neuromodulation for Different Genders: A Chinese Multicentric Prospective Clinical Study

AIM

Sacral neuromodulation (SNM) is widely recognized as the essential treatment modality for patients suffering from various lower urinary tract disorders, particularly overactive bladder (OAB). This prospective study recruited patients who underwent variable frequency SNM treatment at six Chinese medical centers, aiming to evaluate the gender-specific effects of this intervention and provide precise guidance on its application for clinical management.

METHODS

This prospective study was managed by Beijing Hospital, and six Chinese medical centers participated in this prospective research. Inclusion and exclusion criteria were established to screen patients based on the indication for SNM. During the research, all patients were required to record 72-h voiding diaries, urgency scores, and visual analogue scale (VAS) scores to reflect their disease symptoms. Additionally, subjective questionnaire surveys such as OAB symptom score (OABSS) and quality-of-life (Qol) score were recorded to reflect the patients' quality of life and treatment satisfaction.

RESULTS

In this study, 52 patients (male patients: 25; female patients: 27) with OAB symptoms agreed to undergo variable frequency stimulation SNM therapy and finally convert to Stage II. Regarding the baseline outcomes, no significant differences were observed between the male and female groups. In terms of postoperative indicators, male patients showed a greater improvement in Qol scores compared to their female counterparts (20.06 ± 13.12 vs. 40.83 ± 26.06, p = 0.005). The results from VAS scores indicated that pain remission was more pronounced in male patients than in female patients (0.31 ± 0.87 vs. 1.67 ± 2.16, p = 0.02). Importantly, there was a statistically significant disparity in urinary urgency between males and females (male patients: 1.19 ± 1.56; female patients: 2.17 ± 1.52, p = 0.04).

CONCLUSIONS

In our study, we found that variable frequency SNM treatment yielded sex-specific differences in therapeutic effects, with male patients having a better outcome in some metrics. This suggests that a patient's sex may influence when variable frequency SNM is used, and in the patient's follow-up.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: ChiCTR2000036677.

Nonlinear analysis of neuronal firing modulated by sinusoidal stimulation at axons in rat hippocampus

Introduction

Electrical stimulation of the brain has shown promising prospects in treating various brain diseases. Although biphasic pulse stimulation remains the predominant clinical approach, there has been increasing interest in exploring alternative stimulation waveforms, such as sinusoidal stimulation, to improve the effectiveness of brain stimulation and to expand its application to a wider range of brain disorders. Despite this growing attention, the effects of sinusoidal stimulation on neurons, especially on their nonlinear firing characteristics, remains unclear.

Methods

To address the question, 50 Hz sinusoidal stimulation was applied on Schaffer collaterals of the rat hippocampal CA1 region in vivo. Single unit activity of both pyramidal cells and interneurons in the downstream CA1 region was recorded and analyzed. Two fractal indexes, namely the Fano factor and Hurst exponent, were used to evaluate changes in the long-range correlations, a manifestation of nonlinear dynamics, in spike sequences of neuronal firing.

Results

The results demonstrate that sinusoidal electrical stimulation increased the firing rates of both pyramidal cells and interneurons, as well as altered their firing to stimulation-related patterns. Importantly, the sinusoidal stimulation increased, rather than decreased the scaling exponents of both Fano factor and Hurst exponent, indicating an increase in the long-range correlations of both pyramidal cells and interneurons.

Discussion

The results firstly reported that periodic sinusoidal stimulation without long-range correlations can increase the long-range correlations of neurons in the downstream post-synaptic area. These results provide new nonlinear mechanisms of brain sinusoidal stimulation and facilitate the development of new stimulation modes.

Selective neuromodulation of retinal ganglion cells via a hybrid optic-nerve and retinal neuroprosthesis for visual restoration

A visual neuroprosthesis delivers electrical stimulation to the surviving neural cells of the visual pathway to produce prosthetic vision. While the retina is often chosen as the stimulation site, current retinal prostheses are hindered by the lack of functional selectivity that impairs the resolution. A possible strategy to improve the resolution is to combine the retinal stimulation and the stimulation of the optic nerve bundle, which contains myelinated fibres of retinal ganglion cells (RGCs) axons that vary in diameter. In this study, we used a computational model of retinal ganglion cells (RGCs) with myelinated axons to predict whether the frequency of electrical stimulation delivered to the optic nerve can be modulated to preferentially inhibit a subset of optic nerve fibres classified by diameter. The model combined a finite element model of bipolar penetrating electrodes delivering sinusoidal stimulation in the range of 25-10000 Hz to the optic nerve, and a double-cable model, to represent an optic nerve fibre. We found that the diameter of the axon fibre and ion kinetic properties of the RGC affect the neuron's frequency response, demonstrating the potential of an optic nerve stimulation to produce selective inhibition based on the axon fibre size. Clinical Relevance-This establishes the importance of considering the size of the nerve cell axons, as well as the functional type of the RGC, in stimulating the optic nerve. This can be exploited to facilitate functionally selective neuromodulation when used in conjunction with retinal stimulation.

Experimental Study on Nerve Signals Block for Spasticity Based on Antimissile Strategy

A method of blocking neural signal for spasticity which is based on the antimissile strategy was proposed. When the pathological nerve action potential signal is detected at the proximal end of the nerve, such a potential signal that is opposite to the signal of the primary neural activity is applied at the distal end of the nerve at a proper delay so as to block the pathological nerve signal. Preliminary tests were performed on toad sciatic nerve-gastrocnemius specimens. Firstly, the effect of the distance between blocking electrodes on the blocking pulse voltage threshold was studied based on the electrical tension induced by the nerve signal on the controlled muscle. Then, the effective parameters of the blocking waveform were studied. Finally, the delay range of the blocking pulse compared to the pathogen action potential was studied. The results showed that in the sciatic nerve-gastrocnemius specimens, the most effective distance between the blocking electrode pairs was 5 mm and the anodic block required an inverted triangle waveform. The voltage threshold of an effective anodic blocking pulse was 1 V and the minimum pulse width was 90 ms. Under the condition of voltage threshold and minimum pulse width, the time shifting value of blocking pulse was greater than 1ms. It is concluded from the study that the spastic action potential caused by the disease can be effectively blocked, and limb muscle spasms can be eliminated under the action of appropriate electrode configuration and blocking signal waveforms.

High-Frequency Spinal Cord Stimulation for Chronic Pain: Pre-Clinical Overview and Systematic Review of Controlled Trials

OBJECTIVE

To assess the evidence base for high-frequency spinal cord stimulation (HFSCS). HFSCS has the potential to provide paresthesia-free pain relief for patients with chronic pain, in contrast to conventional spinal cord stimulation, which produces distracting and potentially unpleasant paresthesias.

DESIGN

A systematic review following standard methodological guidelines (Prospero #CRD42015029215).

METHODS

We searched PubMed to March 14, 2016 without language restriction and hand-checked reference lists. Two authors independently performed study selection, bias evaluations, and data extraction. The pre-clinical review selected studies focusing on the mechanism and non-human experience with HFSCS. Clinically, any prospective study of adults using HFSCS (≥ 1000 Hz) was included.

RESULTS

Pre-clinical studies have characterized many aspects underlying the mechanism of HFSCS. For the clinical systematic review, eight trials (236 participants randomized or 160 followed prospectively) met inclusion criteria. All trials of HFSCS focused on patients with chronic low back pain with one exception, which included patients with chronic migraine. All but one trial documented funding by industry. Performance bias due to unmasked participants, physicians, and outcome assessors limited the quality of all but one study.

CONCLUSIONS

Significant growth in the preclinical and clinical evidence base for HFSCS suggests that HFSCS may differ from conventional SCS in mechanism of action and efficacy of treatment, respectively. Addressing current knowledge gaps in clinical evidence will require standardization in trial reporting and leveraging the paresthesia-free characteristic of HFSCS to enable masking in high-quality randomized controlled trials.

Implantable neurotechnologies: electrical stimulation and applications

Neural stimulation using injected electrical charge is widely used both in functional therapies and as an experimental tool for neuroscience applications. Electrical pulses can induce excitation of targeted neural pathways that aid in the treatment of neural disorders or dysfunction of the central and peripheral nervous system. In this review, we summarize the recent trends in the field of electrical stimulation for therapeutic interventions of nervous system disorders, such as for the restoration of brain, eye, ear, spinal cord, nerve and muscle function. Neural prosthetic applications are discussed, and functional electrical stimulation parameters for treating such disorders are reviewed. Important considerations for implantable packaging and enhancing device reliability are also discussed. Neural stimulators are expected to play a profound role in implantable neural devices that treat disorders and help restore functions in injured or disabled nervous system.

Reversible nerve conduction block using kilohertz frequency alternating current

OBJECTIVES

The features and clinical applications of balanced-charge kilohertz frequency alternating currents (KHFAC) are reviewed. Preclinical studies of KHFAC block have demonstrated that it can produce an extremely rapid and reversible block of nerve conduction. Recent systematic analysis and experimentation utilizing KHFAC block have resulted in a significant increase in interest in KHFAC block, both scientifically and clinically.

MATERIALS AND METHODS

We review the history and characteristics of KHFAC block, the methods used to investigate this type of block, the experimental evaluation of block, and the electrical parameters and electrode designs needed to achieve successful block. We then analyze the existing clinical applications of high-frequency currents, comparing the early results with the known features of KHFAC block.

RESULTS

Although many features of KHFAC block have been characterized, there is still much that is unknown regarding the response of neural structures to rapidly fluctuating electrical fields. The clinical reports to date do not provide sufficient information to properly evaluate the mechanisms that result in successful or unsuccessful treatment.

CONCLUSIONS

KHFAC nerve block has significant potential as a means of controlling nerve activity for the purpose of treating disease. However, early clinical studies in the use of high-frequency currents for the treatment of pain have not been designed to elucidate mechanisms or allow direct comparisons to preclinical data. We strongly encourage the careful reporting of the parameters utilized in these clinical studies, as well as the development of outcome measures that could illuminate the mechanisms of this modality.