Is the Introduction of Another Variable to the Strength–Duration Curve Necessary in Neurostimulation?

Intensity Modulation: A Novel Approach to Percept Control in Spinal Cord Stimulation

“…When applied directly to sensory nerves, this paradigm produces natural sensations of light touch, pressure, and hair movement, which is different from the electrical paresthesia experienced with continuous stimulation at a uniform pulse width (as is currently used for SCS) . Using a surgically implanted peripheral nerve‐stimulating electrode , it has been demonstrated that continuous TS of peripheral sensory nerves produces a tingling sensation that is described as uncomfortable and electrical , similar to what is seen during conventional SCS. Alteration of the amplitude or pulse width can change the intensity of the perceived stimulation, but it is consistently described as unnatural.…”

“…Using MATLAB (Mathworks, Inc., Natick, MA, USA), an axonal activation model was developed to explore the effect of TS and IMS parameter space for each participant. This model was based on several assumptions: 1) individual axon activation thresholds are randomly distributed from I p to I d ; 2) the subpopulation of axons activated is directly proportional to the product of pulse width and intensity (i.e., pulse width and intensity have identical effects with respect to neural activation) ; and 3) axons are activated in an all‐or‐none fashion, so that stimulation with an intensity/pulse width combination below threshold for axon depolarization will have no effect . Each simulation was designed with 10,000 axons such that I p and I d and would activate 0% and 100%, respectively, and I t would activate a proportional subset of the axons activated at I d .…”

High-Resolution Multi-Scale Computational Model for Non-Invasive Cervical Vagus Nerve Stimulation

“…We developed an approach whereby we modeled rheobase thresholds, namely the response to a long duration pulse. This allowed us, as a first approximation, to remove considerations of neuron dynamics and stimulation train parameters such a number, pulse shape, frequency, and duty‐cycle which while important would incur a large set of additional fiber specific parameterizations —whereas our focus was to address the role of tissue modeling. The assumption also supports future efforts to optimize stimulation approaches leveraging linearity (see “Discussion” section).…”

Parameters of Spinal Cord Stimulation and Their Role in Electrical Charge Delivery: A Review

“…The strength-duration curve demonstrates that narrow pulse widths require high amplitudes to activate a neuron, while wider pulse widths need lower amplitudes. for paresthesia perception and discomfort thresholds, at increasing pulse width (27,28). The resulting "therapeutic window" may guide SCS programming for amplitude and pulse width to optimize pain relief while minimizing discomfort.…”

“…The wide range of frequencies used in commercially available SCS devices have been explored for various indications, in low (<5 Hz) and high‐frequency ranges (up to 1400 Hz) . The clinical effects of various pulse widths have also been examined . Programming strategies have often considered parameters as separate and discrete variables, and less consideration has been given to how these variables interact to modulate pain pathways within the nervous system.…”