Influence on Deep Brain Stimulation from Lead Design, Operating Mode and Tissue Impedance Changes ? A Simulation Study

Abstract

Background: Deep brain stimulation (DBS) systems in current mode and new lead designs are recently available. To switch between DBS-systems remains complicated as clinicians may lose their reference for programming. Simulations can help increase the understanding.Objective: To quantitatively investigate the electric field (EF) around two lead designs simulated to operate in voltage and current mode under two time points following implantation. Methods:The finite element method was used to model Lead 3389 (Medtronic) and 6148 (St Jude) with homogenous surrounding grey matter and a peri-electrode space (PES) of 250 µm. The PES-impedance mimicked the acute (extracellular fluid) and chronic (fibrous tissue) time-point. Simulations at different amplitudes of voltage and current (n=236) were performed using two different contacts. Equivalent current amplitudes were extracted by matching the shape and maximum EF of the 0.2 V/mm isolevel. Results:The maximum EF extension at 0.2 V/mm varied between 2-5 mm with a small difference between the leads. In voltage mode EF increased about 1 mm at acute compared to the chronic PES. Current mode presented the opposite relationship. Equivalent EFs for lead 3389 at 3 V were found for 7 mA (acute) and 2.2 mA (chronic). Conclusions:Simulations showed a major impact on the electric field extension between postoperative time points. This may explain the clinical decisions to reprogram the amplitude weeks after implantation. Neither the EF extension nor intensity is considerably influenced by the lead design. However, the EF distribution is affected by the larger contact of Lead 6148 generating an electric field below the tip.

Refining the Deep Brain Stimulation Target within the Limbic Globus Pallidus Internus for Tourette Syndrome

“…Previous simulations by Yousif et al [31] and Alonso et al [32], however, show that this has little impact at chronic stimulation points, as was the case in our study. Further limitations lie in MRI resolution and the contrast between different tissue types, which introduces some uncertainty in the tissue classification of the voxels and for neural tissue, as well as a dependency from axon activation on the electric conductivity [33].…”

Disaggregation of Amyloid-β Plaques by a Local Electric Field Generated by a Vertical Nanowire Electrode Array

“…The endogenous EFs of brain have steady and slow charging gradients, and produce lower potential values (1 ∼ 2 × 10 2 V/m) , than typical action potentials in neurons. The exogenous EFs are needed to affect the associated functions in the biological system, including the purpose of clinical deep brain stimulation (DBS) (∼6 × 10 2 V/m), , migration of cells for regeneration (∼1 × 10 3 V/m), , healing of bone fractures (∼2 × 10 3 V/m), , induction of action potentials in excitable cells (∼2 × 10 3 V/m), , and electroporation for membrane penetration (∼1 × 10 5 V/m). , The upper bound of biologically relevant EF strengths can be set according to the high-field limit which tends to disintegrate the nuclear membrane and organelles within cells (∼3 × 10 7 V/m). , Considering that the maximum field strength used in this study is 561.1 V/m (applying voltage; 50 mV) generated on the surface of nanowire electrode and those formed between two electrodes is 249.4 V/m, it is clear that the magnitude of EF generated by VNEA sufficiently exceed on the order of endogenous levels, but not exceed the high-field limit which can affect the biological function.…”

How Sample Size Impacts Probabilistic Stimulation Maps in Deep Brain Stimulation

“…This method uses the volume conductor model with a heterogeneous isotropic tissue conductivity based on segmentation of the pre-operative T 2 -weighted MRI. The DBS lead was modeled according to manufacturer specification and placed in the tissue volume according to the post-operative CT. A 250 µm thick peri-electrode space surrounding the lead was modeled as white brain matter [20]. The simulations were computed in a box of size 100 × 100 × 100 mm with a physics-controlled mesh (the finest element size closest to the lead).…”