Role of electrode design on the volume of tissue activated during deep brain stimulation

Department of Biomedical Engineering, Cleveland Clinic Foundation, Cleveland, OH, USA.
Journal of Neural Engineering (Impact Factor: 3.42). 04/2006; 3(1):1-8. DOI: 10.1088/1741-2560/3/1/001
Source: PubMed

ABSTRACT Deep brain stimulation (DBS) is an established clinical treatment for a range of neurological disorders. Depending on the disease state of the patient, different anatomical structures such as the ventral intermediate nucleus of the thalamus (VIM), the subthalamic nucleus or the globus pallidus are targeted for stimulation. However, the same electrode design is currently used in nearly all DBS applications, even though substantial morphological and anatomical differences exist between the various target nuclei. The fundamental goal of this study was to develop a theoretical understanding of the impact of changes in the DBS electrode contact geometry on the volume of tissue activated (VTA) during stimulation. Finite element models of the electrodes and surrounding medium were coupled to cable models of myelinated axons to predict the VTA as a function of stimulation parameter settings and electrode design. Clinical DBS electrodes have cylindrical contacts 1.27 mm in diameter (d) and 1.5 mm in height (h). Our results show that changes in contact height and diameter can substantially modulate the size and shape of the VTA, even when contact surface area is preserved. Electrode designs with a low aspect ratio (d/h) maximize the VTA by providing greater spread of the stimulation parallel to the electrode shaft without sacrificing lateral spread. The results of this study provide the foundation necessary to customize electrode design and VTA shape for specific anatomical targets, and an example is presented for the VIM. A range of opportunities exist to engineer DBS systems to maximize stimulation of the target area while minimizing stimulation of non-target areas. Therefore, it may be possible to improve therapeutic benefit and minimize side effects from DBS with the design of target-specific electrodes.

    • "Improvements in selectivity may be possible by altering the configuration (i.e., the geometry and polarity) of the stimulation electrodes. For example, with a standard clinical lead, such as the Medtronic Model 3387 or Model 3389, selectivity may be improved by altering the geometry of the individual electrodes (Butson and McIntyre 2006), segmenting the electrodes into many smaller electrodes (Buhlmann et al 2011, Martens et al 2011), or by combining the electrodes in multipolar configurations to shape the volume of tissue activated (Keane et al 2012). "
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    ABSTRACT: Deep brain stimulation (DBS) is an effective treatment for movement disorders and a promising therapy for treating epilepsy and psychiatric disorders. Despite its clinical success, the efficiency and selectivity of DBS can be improved. Our objective was to design electrode geometries that increased the efficiency and selectivity of DBS. We coupled computational models of electrodes in brain tissue with cable models of axons of passage (AOPs), terminating axons (TAs), and local neurons (LNs); we used engineering optimization to design electrodes for stimulating these neural elements; and the model predictions were tested in vivo. Compared with the standard electrode used in the Medtronic Model 3387 and 3389 arrays, model-optimized electrodes consumed 45-84% less power. Similar gains in selectivity were evident with the optimized electrodes: 50% of parallel AOPs could be activated while reducing activation of perpendicular AOPs from 44 to 48% with the standard electrode to 0-14% with bipolar designs; 50% of perpendicular AOPs could be activated while reducing activation of parallel AOPs from 53 to 55% with the standard electrode to 1-5% with an array of cathodes; and, 50% of TAs could be activated while reducing activation of AOPs from 43 to 100% with the standard electrode to 2-15% with a distal anode. In vivo, both the geometry and polarity of the electrode had a profound impact on the efficiency and selectivity of stimulation. Model-based design is a powerful tool that can be used to improve the efficiency and selectivity of DBS electrodes.
    Journal of Neural Engineering 07/2015; 12(4):046030. DOI:10.1088/1741-2560/12/4/046030 · 3.42 Impact Factor
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    • "Butson and McIntyre (2006) on the other hand investigated the effect of contact height and diameter of DBS electrodes on the volume of tissue activated (VTA). They found that an increase in electrode height caused a linear increase in the VTA, while an increase in the electrode diameter resulted in a logarithmic decrease in the VTA (Butson and McIntyre, 2006). Recently, Howell and Grill (2014) reported that electric potential distribution in the tissue is another factor besides electrode impedance that determines stimulation efficiency. "
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    ABSTRACT: Background Microelectrode arrays have been used successfully for neuronal stimulation both in vivo and in vitro. However, in most instances currents required to activate the neurons have been in un-physiological ranges resulting in neuronal damage and cell death. There is a need to develop electrodes which require less stimulation current for neuronal activation with physiologically relevant efficacy and frequencies. New method The objective of the present study was to examine and compare the stimulation efficiency of different electrode geometries at the resolution of a single neuron. We hypothesized that increasing the electrode perimeter will increase the maximum current density at the edges and enhance stimulation efficiency. To test this postulate, the neuronal stimulation efficacy of common circular electrodes (smallest perimeter) was compared with sinusoidal (medium perimeter), and spiral (largest perimeter with internal boundaries) electrodes. We explored and compared using both a finite element model and in vitro stimulation of neurons isolated from Lymnaea central ganglia. Results Interestingly, both the computational model and the live neuronal stimulation experiments demonstrated that the common circular microelectrode requires less stimulus to activate a cell compared to the other two electrode shapes with the same surface area. Our data further revealed that circular electrodes exhibit the largest sealing resistance, stimulus transfer, and average current density among the three types of electrodes tested. Comparison with existing methods Average current density and not the maximum current density at the edges plays an important role in determining the electrode stimulation efficiency. Conclusion Circular shaped electrodes are more efficient in inducing a change in neuronal membrane potential. Copyright © 2015 Elsevier B.V. All rights reserved.
    Journal of neuroscience methods 04/2015; 248. DOI:10.1016/j.jneumeth.2015.03.024 · 1.96 Impact Factor
    • "The models predicted much lower levels of activation from all other guidewire electrodes targeting fornix. Previous modeling work has shown electrode length to be an important factor for optimizing the volume of tissue activated by DBS (Butson and McIntyre 2006). To evaluate the effect of electrode length in endovascular stimulation in these two targets, model predictions of neuronal activation of SgCwm and fornix were calculated for ring and guidewire electrodes measuring 0.5, 1.5, 2.5, 3.5, and 4.5 mm in length at stimulation amplitudes between 0 and 10 V. "
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    ABSTRACT: Objective. Deep brain stimulation (DBS) therapy currently relies on a transcranial neurosurgical technique to implant one or more electrode leads into the brain parenchyma. In this study, we used computational modeling to investigate the feasibility of using an endovascular approach to target DBS therapy. Approach. Image-based anatomical reconstructions of the human brain and vasculature were used to identify 17 established and hypothesized anatomical targets of DBS, of which five were found adjacent to a vein or artery with intraluminal diameter ≥1 mm. Two of these targets, the fornix and subgenual cingulate white matter (SgCwm) tracts, were further investigated using a computational modeling framework that combined segmented volumes of the vascularized brain, finite element models of the tissue voltage during DBS, and multi-compartment axon models to predict the direct electrophysiological effects of endovascular DBS. Main results. The models showed that: (1) a ring-electrode conforming to the vessel wall was more efficient at neural activation than a guidewire design, (2) increasing the length of a ring-electrode had minimal effect on neural activation thresholds, (3) large variability in neural activation occurred with suboptimal placement of a ring-electrode along the targeted vessel, and (4) activation thresholds for the fornix and SgCwm tracts were comparable for endovascular and stereotactic DBS, though endovascular DBS was able to produce significantly larger contralateral activation for a unilateral implantation. Significance. Together, these results suggest that endovascular DBS can serve as a complementary approach to stereotactic DBS in select cases.
    Journal of Neural Engineering 03/2014; 11(2):026011. DOI:10.1088/1741-2560/11/2/026011 · 3.42 Impact Factor
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