Fiber Activation by Bipolar Stimulation in Deep Brain Stimulation: A Patient Case Study

TL;DR

This study compares two computational models to understand how bipolar deep brain stimulation affects neural fibers in a patient with Essential Tremor, highlighting the limitations of traditional models and the potential of fiber activation modeling.

Contribution

It demonstrates that neural fiber activation models better capture bipolar stimulation effects than conventional VTA models in DBS therapy.

Findings

VTA models do not accurately reflect bipolar stimulation effects.

Neural fiber activation models show promise in modeling DBS outcomes.

Neither model fully explains bilateral effects from unilateral stimulation.

Abstract

Deep Brain Stimulation (DBS) is a therapy widely used for treating the symptoms of neurological disorders. Electrical pulses are chronically delivered in DBS to a disease-specific brain target via a surgically implanted electrode. The stimulating contact configuration, stimulation polarity, as well as amplitude, frequency, and pulse width of the DBS pulse sequence are utilized to optimize the therapeutic effect. In this paper, the utility of therapy individualization by means of patient-specific mathematical modeling is investigated with respect to a specific case of a patient diagnosed with Essential Tremor (ET). Two computational models are compared in their ability to elucidate the impact of DBS stimulation on the dentato-rubrothalamic tract: (i) a conventional model of Volume of Tissue Activated (VTA) and (ii) a well-established neural fiber activation modeling framework known as OSS-DBS. The simulation results are compared with tremor measured in the patient under different DBS settings using a smartphone application. The findings of the study highlight that temporally static VTA models do not adequately describe the differences in the outcomes of bipolar stimulation settings with switched polarity, whereas neural fiber activation models hold potential in this regard. However, it is noted that neither of the investigated models fully accounts for the measured symptom pattern, particularly regarding a bilateral effect produced by unilateral stimulation.