Current steering to control the volume of tissue activated during deep brain stimulation

Department of Biomedical Engineering, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
Brain Stimulation (Impact Factor: 4.4). 02/2008; 1(1):7-15. DOI: 10.1016/j.brs.2007.08.004
Source: PubMed


Over the last two decades, deep brain stimulation (DBS) has become a recognized and effective clinical therapy for numerous neurological conditions. Since its inception, clinical DBS technology has progressed at a relatively slow rate; however, advances in neural engineering research have the potential to improve DBS systems. One such advance is the concept of current steering, or the use of multiple stimulation sources to direct current flow through targeted regions of brain tissue. The goals of this study were to develop a theoretical understanding of the effects of current steering in the context of DBS, and use that information to evaluate the potential utility of current steering during stimulation of the subthalamic nucleus.
We used finite element electric field models, coupled to multi-compartment cable axon models, to predict the volume of tissue activated (VTA) by DBS as a function of the stimulation parameter settings.
Balancing current flow through adjacent cathodes increased the VTA magnitude, relative to monopolar stimulation, and current steering enabled us to sculpt the shape of the VTA to fit a given anatomical target.
These results provide motivation for the integration of current steering technology into clinical DBS systems, thereby expanding opportunities to customize DBS to individual patients, and potentially enhancing therapeutic efficacy.

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    • "In order to enhance the reliability and tolerability of tDCS, we describe a novel method called Within Electrode Current Steering (WECS). This concept is distinct from (across electrode) current steering, as developed for implanted devices such as Deep Brain Stimulation (DBS), where current is steered between electrodes that are each in contact with tissue, with the goal of changing desired brain regions that are activated [2]. WECS adjusts current between electrodes not in contact with tissue but rather embedded in an electrolyte on the body surface. "
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    ABSTRACT: Within Electrode Current Steering (WECS) is a novel method that enhances reliability and tolerability of tDCS. The underlying assumption of WECS is steering current within electrodes but without altering current distribution in brain target. Through an exemplary case example of a realistic electrode and head geometry (FEM), we demonstrated how current flow in the brain is independent of current steering at the electrode. Three current split cases (even, partially uneven, and fully uneven), keeping total current (1 mA) fixed within the electrodes are tested. At the electrode-assembly interface with the skin, the current density distribution varied only incrementally across conditions (e.g. less than would be expected with even minor changes in electrode assembly or skin properties. There was no difference in the predicted electric filed at the brain target under all three cases. Thus, with such electrode assembly design, current steering to any functional electrode would not significantly increase current density in the skin (enhance tolerability during tDCS).
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    • "In conventional, single-source DBS systems (voltage-and current-control systems), precision and stability of therapy delivery may be limited since each contact cannot be controlled independently . In contrast, simulation models of DBS indicate that current steering with multiple stimulation sources might be able to transfer current more precisely and more constant over time [1] [2]. In principle this approach might be a helpful tool for the clinician to control side effects thereby improving the overall outcome of DBS. "

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