Motor cortex stimulation for Parkinson's disease: a modelling study

Abstract

Chronic motor cortex stimulation (MCS) is currently being investigated as a treatment method for Parkinson's disease (PD). Unfortunately, the underlying mechanisms of this treatment are unclear and there are many uncertainties regarding the most effective stimulation parameters and electrode configuration. In this paper, we present a MCS model with a 3D representation of several axonal populations. The model predicts that the activation of either the basket cell or pyramidal tract (PT) type axons is involved in the clinical effect of MCS. We propose stimulation protocols selectively targeting one of these two axon types. To selectively target the basket cell axons, our simulations suggest using either cathodal or bipolar stimulation with the electrode strip placed perpendicular rather than parallel to the gyrus. Furthermore, selectivity can be increased by using multiple cathodes. PT type axons can be selectively targeted with anodal stimulation using electrodes with large contact sizes. Placing the electrode epidurally is advisable over subdural placement. These selective protocols, when practically implemented, can be used to further test which axon type should be activated for clinically effective MCS and can subsequently be applied to optimize treatment. In conclusion, this paper increases insight into the neuronal population involved in the clinical effect of MCS on PD and proposes strategies to improve this therapy.

Computational Study on Subdural Cortical Stimulation - The Influence of the Head Geometry, Anisotropic Conductivity, and Electrode Configuration

“…In the results of [26], neuronal responses elicited by cortical stimulation were very sensitive to the position of the stimulation electrodes, geometry, and polarity. Also, the investigation of neuronal responses is based on finite element analysis [23], [24], [26], [27], [43]. Thus, precise finite element analysis based on reasonable brain model selection should be conducted before analyzing neuronal response.…”

“…Due to safety issues (seizures [20]), ECS has been performed widely in clinical surgery for cortical stimulation [6], [8], [9], [21], [22]. For this reason, the effects of ECS have been investigated by computational studies and clinical trials [6], [8], [23]–[27]. However, in some cases, if brain atrophy–which is observed frequently in candidates for ECS–is moderate or severe, the cerebrospinal fluid-filled space can be a barrier to delivery of electrical stimulation to the cortex despite its electrical conductance.…”

Validation of Computational Studies for Electrical Brain Stimulation With Phantom Head Experiments

“…Restricting study to a specific area of the brain, and considering anatomical shape to some extent, extruded slab models that represent the motor cortex have also been generated to investigate the effects of motor cortex stimulation [18][19][20]. These modelling studies may elucidate the neuromodulation effects in more focused target areas; however, the prediction of overall current density in the whole brain may be misinterpreted due to non-negligibly significant mismatches between these models.…”

Effect of Anatomically Realistic Full-Head Model on Activation of Cortical Neurons in Subdural Cortical Stimulation—A Computational Study

“…A computational study is one of the most useful approaches in investigating the influence of these various parameters. Such investigations have primarily used two kinds of volume conduction models; these are represented by a simplified partial-head model13141516171819 or a full-head model20212223242526 that considers the complex geometry of the brain. The simplified partial head model is an extruded slab model that represents a part of the brain, typically the precentral gyrus area.…”