Functional MRI and DTI Analysis of Post VNS Therapy Rehab Changes

This study will consist of 2‐3 fMRI sessions, depending on group assignment, and span 2 days for each session. It will be done at a single site only, at UTSW. The fMRI tasks will consists of subjects grasping and releasing a handgrip. The VNS implant will be used in this study to determine if having the implant active during physical rehabilitation produces white matter tract changes in the brain visible on fMRI. All subjects in the STU 062017‐071 study will receive a VNS implant. And all subjects in this study are also subjects of the STU 062017‐071 study. Therefore participants of this study will enroll with the implant already in place. Methods: After passing routine MRI screening, patients who are enrolled in the VNS‐REHAB study and consent to participate in the fMRI study will be scanned on a Phillips 3 Tesla Research Magnet (Ingenia, Philips Healthcare, Best, the Netherlands). Patients will be scanned before therapy and the week after therapy. A subset of patients will be scanned 3 times, before therapy, after therapy without activation of the vagal nerve stimulator, and after therapy with activation of the vagal nerve stimulator. Scan Time: Scan time is limited to 15 minutes per session to match manufacture FDA guidelines. Patients will receive two, 15 minute MRI scans over 2 days.