Date of Thesis

Spring 2024

Description

Parkinson disease (PD) is a neurodegenerative disorder resulting from the death of dopamine releasing neurons. Levodopa is used to treat PD and has side effects such as dyskinesia, involuntary and uncontrollable movements. When levodopa-induced side effects diminish the effectiveness of treatment, another option for PD patients is deep brain stimulation (DBS). DBS is the implantation of electrodes into the brain to deliver electrical impulses to specific regions. For PD, the standard target is the subthalamic nucleus (STN). Volume of tissue activation (VTA) modeling can be used to quantify the amount of stimulation in and around the target area. STN DBS may reduce dyskinesia indirectly through reducing medication or directly through stimulation. The primary aim of this study was to determine the optimal stimulation locations for levodopa and dyskinesia reduction to see if the locations were distinct or overlapping. Patient-specific STN and VTA point cloud data from 40 PD patients who received bilateral STN DBS were created from Analyze and MATLAB software. Stimulated tissue activation in the dorsal-ventral, lateral-medial, and anterior-posterior subthalamic regions was calculated using STN and VTA point clouds. Levodopa equivalent daily dosage (LEDD) and dyskinesia both reduced significantly from pre- to post-operative appointments; however, LEDD and dyskinesia reduction did not correlate with one another. Overall, stimulation within the STN appears to explain LEDD reduction, whereas stimulation above the STN appears to explain dyskinesia reduction. Dyskinesia reduction after STN DBS may be due to stimulation of the pallidothalamic fibers dorsal to the STN (Kim et al., 2015), specifically the lenticular fasciculus, which originates from the globus pallidus internus (GPi).

Currently, Analyze and MATLAB are both used for medical imaging processing; however, MATLAB has released a medical imaging software that has the same capabilities as Analyze. The secondary aim of this study was to determine if the medical imaging toolbox in MATLAB is comparable to the established Analyze processing. The same protocol for image registration, measuring contacts, and measuring the STN was performed in MATLAB and Analyze. MATLAB processing was not comparable to Analyze. Registration of images did not align skull and anatomical structures as well as Analyze. MATLAB contacts were measured to be multiple millimeters away from measured contacts in Analyze and the STN was larger. Additional refinements to MATLAB processing need to be made.

Keywords

Parkinson, DBS, levodopa, dyskinesia, modeling, VTA

Access Type

Honors Thesis (Bucknell Access Only)

Degree Type

Bachelor of Science

Major

Biology

Minor, Emphasis, or Concentration

Neurpsychology

First Advisor

Karlo Malaga

Second Advisor

Elizabeth Capaldi

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