Functional MRI and DTI Analysis of Post VNS Therapy Rehab Changes

The purpose of performing magnetic resonance imaging (MRI) scans on patients undergoing stroke rehabilitation therapy in conjunction with vagal nerve stimulators (VNS) is to determine if the patients clinical improvement correlates to changes that can be identified on MRI of the brain such as degree of blood oxygen level dependent (BOLD) signal, changes in resting state connectivity, and corticospinal tract fiber density. Subjects will be randomized at implant surgery to either the device treatment (rehabilitation and VNS) or control (rehabilitation and Control VNS) groups. All participants of this study are also participants of the STU 062017-071 study and chose to participate in this functional magnetic resonance imaging (fMRI) sub-study. Rehabilitation is standard of care. Both experimental groups and control groups will receive pre-rehabilitation and post-rehabilitation fMRI and diffusion tensor imaging (DTI) scans to quantify their white matter track density. We will analyze this data using the University of Texas Southwestern (UTSW) Advanced Neuroscience Imaging Research (ANSIR) pipeline which can automatically quantify white matter track density on both sides of the brain given the appropriate scans. In this study the VNS device specifically will not be studied. Rather we will be looking at the changes that occur in the brain as a result of using the VNS device during physical rehabilitation. Once the post-rehabilitation scans are completed the patients in the control group will be given the opportunity to crossover into the experimental group and receive physical rehabilitation with the VNS implant turned on. They will have a third MRI session after their round of rehabilitation with the implant turned on in order to quantify their white matter tract density.