![]() Activation and conduction block thresholds were calculated for each axon model. ( C) The direct axonal response to KHFSCS was examined following the same procedure. This figure shows the time-dependent transmembrane voltages at several nodes in a dorsal column (DC) axon model and illustrates action potential generation with a conventional 50-Hz SCS waveform. With sufficient depolarization, action potentials were initiated in an axon and propagated in both directions. ( B) To estimate the direct axonal response to SCS, the SCS-induced extracellular voltages were interpolated onto the axon models. The voltage distributions were calculated from the finite element model. ( A) Isopotential lines of the extracellular voltages generated by bipolar spinal cord stimulation (SCS). If the KHFSCS amplitude is at or above the conduction block threshold, the action potential is unable to propagate past the stimulation electrode(s) (as demonstrated in the right column).ĭirect axonal response to kilohertz frequency spinal cord stimulation (KHFSCS). This test pulse produces an action potential that propagates along the axon. To test for conduction block, a test pulse is applied at one end of the axon. The left column shows the time-dependent transmembrane voltages in an axon model in response to a subthreshold stimulus, whereas the middle and right columns demonstrate the responses to KHFSCS stimuli at activation and conduction block thresholds, respectively. ![]() Materials and Methodsĭirect axonal response to kilohertz frequency spinal cord stimulation (KHFSCS). The data indicate that direct activation of the spinal cord elements may be possible with KHFSCS however, it is unlikely that clinical KHFSCS generates direct conduction block within the spinal cord. This approach permitted systematic characterization of numerous variables and their influence on the direct effects of KHFSCS: waveform shape, dorsal cerebrospinal fluid (dCSF) thickness, lead location, fiber collateralization, and fiber size. Our model infrastructure consisted of a finite element model (FEM) of an SCS lead implanted in the epidural space along with multicompartment cable models of dorsal root (DR) and dorsal column (DC) fibers in the spinal cord. 16–23 The goal of this study was to use similar theoretical techniques to investigate the effects of KHFSCS on the spinal cord. This knowledge can be difficult to gain experimentally, and, in the past, several groups have used computational models to study conventional SCS. To determine the pain relief mechanisms of KHFSCS, we must understand the electric fields generated by the stimulation waveform and its direct effects on the neural elements of the spinal cord. A recent double-blind, placebo-controlled crossover trial concluded that KHFSCS was not better than sham treatment. However, results with KHFSCS remain inconsistent. 9–12 These studies have also shown a patient preference for KHFSCS over conventional SCS and the ability of KHFSCS to provide pain relief in patients who failed conventional SCS. Initial clinical data with a novel device capable of delivering kilohertz frequency SCS (KHFSCS) suggest promising clinical benefits and paresthesia-free effects. ![]() Kilohertz stimulation frequencies have shown the ability to generate rapid and reversible conduction block in peripheral nerve models 6–8 and have gained significant attention in recent years. 5 There has been recent interest in the use of much higher frequencies in an attempt to improve the clinical results with SCS. Although conventional SCS applied at a rate between 40 and 80 Hz has been a widely used clinical therapy for decades, it has a limited success rate (approximately 50% of patients receive ≥50% reduction in pain).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |