Neural Selectivity, Efficiency, and Dose Equivalence in Deep Brain Stimulation through Pulse Width Tuning and Segmented Electrodes

Abstract

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Achieving deep brain stimulation (DBS) dose equivalence is challenging, especially with pulse width tuning and directional contacts. Further, the precise effects of pulse width tuning are unknown.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We created multicompartment neuron models for two axon diameters and used finite element modeling to determine extracellular influence from standard and segmented electrodes. We analyzed axon activation profiles and calculated volumes of tissue activated.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Long pulse widths focus the stimulation effect on small, nearby fibers, suppressing white matter tract activation (responsible for some DBS side effects) and improving battery utilization. Directional leads enable similar benefits to a greater degree. We derive equations for equivalent activation with pulse width tuning and segmented contacts.</jats:p></jats:sec><jats:sec><jats:title>Interpretations</jats:title><jats:p>We find agreement with classic studies and reinterpret recent articles concluding that short pulse widths focus the stimulation effect on small, nearby fibers, decrease side effects, and improve power consumption. Our field should reconsider shortened pulse widths.</jats:p></jats:sec>

Tract-based analysis of target engagement by subcallosal cingulate deep brain stimulation for treatment resistant depression

“…Long pulse width (210e450 ms) and short pulse width (90 ms) stimulation were compared in our clinical study. Short pulses stimulate large fibers preferentially, while long pulses can activate both large and smaller fibers [33,34]. Pulse width was taken into account when modelling the volume of activated tissue but our current imaging techniques cannot resolve the actual diameter of fibers distributed within the target area for each patient; therefore, it remains unclear whether pulse width tuning affected our results.…”

Current Directions in Deep Brain Stimulation for Parkinson’s Disease—Directing Current to Maximize Clinical Benefit

“…In this domain, this is applied by positioning an appropriate model of a stimulating electrode, configuring it with appropriate stimulation parameters (polarities, stimulus amplitude), and determining the resulting current flows and voltage gradients in the surrounding tissue. These electromagnetic gradients can then be applied, in a second step, to a population of simulated neurons positioned and oriented preferentially around the stimulating electrode so as to determine points at which neurons may be activated by a given stimulation regime [38]. These neurons may be modeled such that they respond both to the intensity of the stimulation (current amplitude) and the time-dependent parameters such as the width of a stimulation pulse [38].…”

A retrospective evaluation of automated optimization of deep brain stimulation parameters

“…For the avoidance of the IC, we make use of the fiber orientations obtained from tractography. We denote the fiber orientation at position x by n f (x) and define a f according to (2) with n p replaced by n f . As for the avoidance of the Vc, a f is kept below α to avoid stimulation of the IC.…”

“…The choice of stimulation frequency and pulse width remains up to the physician. As the firing threshold of axons changes with frequency and pulse width [14,2], a change of these parameters during a programming session might require adjustements of α.…”

“…The proposed algorithms focus on optimizing the stimulation voltages for optimal target activation, but they do not directly take into account stimulation pulse width and frequency, which can also have a significant influence on the stimulation effects [52,10,2]. For now, the choice of pulse width and frequency remains the responsibility of the clinician.…”