Comparing Current Steering Technologies for Directional Deep Brain Stimulation Using a Computational Model That Incorporates Heterogeneous Tissue Properties

Abstract

Objective A computational model that accounts for heterogeneous tissue properties was used to compare multiple independent current control (MICC), multi‐stim set (MSS), and concurrent activation (co‐activation) current steering technologies utilized in deep brain stimulation (DBS) on volume of tissue activated (VTA) and power consumption. Methods A computational model was implemented in Sim4Life v4.0 with the multimodal image‐based detailed anatomical (MIDA) model, which accounts for heterogeneous tissue properties. A segmented DBS lead placed in the subthalamic nucleus (STN). Three milliamperes of current (with a 90 μs pseudo‐biphasic waveform) was distributed between two electrodes with various current splits. The laterality, directional accuracy, volume, and shape of the VTAs using MICC, MSS and co‐activation, and their power consumption were computed and compared. Results MICC, MSS, and coactivation resulted in less laterality of steering than single‐segment activation. Both MICC and MSS show directional inaccuracy (more pronounced with MSS) during radial current steering. Co‐activation showed greater directional accuracy than MICC and MSS at centerline between the two activated electrodes. MSS VTA volume was smaller and more compact with less current spread outside the active electrode plane than MICC VTA. There was no consistent pattern of power drain between MSS and MICC, but electrode co‐activation always used less power than either fractionating paradigm. Conclusion While current fractionalization technologies can achieve current steering between two segmented electrodes, this study shows that there are important limitations in accuracy and focus of tissue activation when tissue heterogeneity is accounted for.

Steering the Volume of Tissue Activated With a Directional Deep Brain Stimulation Lead in the Globus Pallidus Pars Interna: A Modeling Study With Heterogeneous Tissue Properties

“…However, as the current increases from 1 to 2 mA, VTAs enlarged and exceeded the GPi boundary from the ventral side (and sometimes medial side) into undesired side effect regions such as the optic tract or the internal capsule (Figure 3C, blue). Consistent with previous findings, the VTAs with the single-segment monopole (configuration 1) generated the most axially asymmetric and largest VTA at the cathodic contact (Zhang et al, 2019). For the vertically stacked two-segment monopole configuration (configuration 2b), at 1 mA current amplitude, the VTA elongated dorsally along the lead and activates more structures dorsal to the GPi such as the medial medullary lamina FIGURE 3 | VTAs for various configurations: (A) 1.5 mm vertical spacing with 1 mA current, settings 1, 2a, and 3 (see methods), (B) 1.5 mm vertical pacing with 1 mA current, settings 2b, 4, and 5, (C) 1.5 mm vertical spacing with 2 mA current, settings 1, 2a, and 3, (D) 1.5 mm vertical pacing with 2 mA current, settings 2b, 4, and 5, (E) 0.5 mm vertical spacing with 1 mA current, settings 2b, 4, and 5, (F) 0.5 mm vertical spacing with 2 mA current, settings 2b, 4, and 5, marron = VTA inside of GPi, orange = VTA between GPe and GPi (medial medullary lamina), yellow = VTA inside of GPe, blue = VTA outside of GP.…”

“…Recent modeling studies have now extended the VTA calculation to segmented DBS leads. Activation of a single electrode segment of these leads resulted in a shift in laterality of the VTA, sometimes known as directional DBS (Buhlmann et al, 2011 ; Zhang et al, 2019 ). However, there have been very few studies where bipolar settings have been used to model the VTA (Buhlmann et al, 2011 ; Duffley et al, 2019 ), and among those that have, homogeneous tissue models were used.…”

“…By leveraging our previous work calculating VTAs in the STN (Zhang et al, 2019 ), we hereby report a computational model for VTAs in the globus pallidus (GP) using directional leads. Here, we demonstrate the utility and potential advantages of using two vertical electrode spacing options (0.5 mm and 1.5 mm) with various monopolar and bipolar settings, and their effects on the size and shape of the resultant VTA in a heterogeneous tissue model.…”

Update on Current Technologies for Deep Brain Stimulation in Parkinson’s Disease

“…Coactivation allows for multiple contacts to be stimulated as if they were a single electrode (see below). In a modeling study, coactivation was shown to be associated with lower power consumption than MICC due to lowered impedance at the electrode-tissue interface [ 32 ].…”

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

“…The use of simple programming protocols, such as the activation of a single directional segment, has proved to be effective in the vast majority of cases [13]. Directional multiple-electrode programming configurations, whether using independent current controllers or interleaving, may provide additional nuances in programming strategies, but may also result in increased programming complexity [59], changes to battery power consumption, and reduction in the laterality of the volume of activation [60]. To assist with DBS programming, DBS producers developed innovative software platforms for functional mapping, as well as tools for visualization of the volume of neural activation.…”