Differences among implanted pulse generator waveforms cause variations in the neural response to deep brain stimulation

Abstract

Objective-Two different Medtronic implantable pulse generator (IPG) models are currently used in clinical applications of deep brain stimulation (DBS): Soletra and Kinetra. The goal of this study was to evaluate and compare the stimulation waveforms produced by each IPG model. Methods-We recorded waveforms from a broad range of stimulation parameter settings in each IPG model, and compared them to idealized waveforms that adhered to the parameters specified in the programming device. We then used a previously published computational model to predict the neural response to the various stimulation waveforms.Results-The stimulation waveforms produced by the IPGs differed from the idealized waveforms assumed in previous theoretical and clinical studies, and the waveforms differed among the IPG models. These differences were greater at higher frequencies and longer pulse widths, and caused variations of up to 0.4 V in activation thresholds for model axons located 3 mm from the DBS electrode contact.Conclusions-The specific details of the stimulation waveform directly affect the neural response to DBS and should be accounted for in theoretical and experimental studies of DBS.Significance-While the clinical selection of DBS parameters is individualized to each patient based on behavioral outcomes, scientific analysis of stimulation parameter settings and clinical threshold measurements are subject to a previously unrecognized source of error unless the actual waveforms produced by the IPG are accounted for.

Effect of Dispersive Conductivity and Permittivity in Volume Conductor Models of Deep Brain Stimulation

“…Alternative orientations may be expected to result in changes to the estimated volume of tissue activated. Finally the stimuli do not incorporate non-idealities in the output waveform of currently used stimulators [36].…”

Patient-Specific Model-Based Investigation of Speech Intelligibility and Movement during Deep Brain Stimulation

“…Before implementing the settings into the model, the electric potential settings were normalized from 4 to 3.5 V, and from 2 to 1.7 V according to the voltage threshold correction factors for the Medtronic Kinetra neurostimulation system (Medtronic, Inc. USA) [29] . The distribution of the electric potential in the vicinity of the electrodes was calculated using the equation for steady currents [30] .…”

Simulation of Cortico-Basal Ganglia Oscillations and Their Suppression by Closed Loop Deep Brain Stimulation

“…Changes in tissue properties may also alter threshold stimulation amplitudes for axons and the amplitude of the LFP, however this would remain a numerical scaling since the volume conductor is assumed to be piecewise homogeneous. Further errors in the axonal activation common to all networks could be caused by non-idealities in the stimulation waveform, which have not been considered here [57]. Finally synaptic changes due to DBS have been hypothesized by closed-loop modeling studies [58], but were neglected in this study and may have implications for controller tuning if the effective coupling strength were to change.…”