The Impact of Deep Brain Stimulation on Speech and Swallow Function in Parkinson Disease

Nearly one-million people in North America are now living with Parkinson's disease (PD), and that number is projected to rise to nearly 1.2 million by 2030. With advancements in neuromodulatory technologies, increasingly more of these individuals elect to undergo deep brain stimulation (DBS) surgery in order to control symptoms of the disease, including refractory tremor, medication-induced dyskinesias, and PD-associated dystonia. The two most common DBS neural targets for controlling these symptoms are the globus pallidus internal segment (GPi) and the subthalamic nucleus (STN). Recent meta-analyses have shown relative equivalence between these two sites at controlling core PD symptoms. To date, there is not conclusive evidence regarding the potential impact of DBS to GPi or STN on laryngeal-mediated functions of voice, swallowing, and cough, and consequently no guidance on whether these outcomes should be considered when selecting DBS target. Therefore, the goal of this project is to determine the impact of DBS neural target (STN versus GPi), lead location within the target, laterality, and stimulation settings on voice, swallow and cough function in people with PD. The larynx is an important player in each of these functions, and our central hypothesis is that spread of stimulation to corticobulbar fibers in the genu of the internal capsule have deleterious effects on laryngeal motor control, resulting in voice, swallow, and cough dysfunction. We have identified three specific aims for this application: 1.) To compare laryngeal function during volitional voice tasks pre-post DBS, and when DBS placement is bilateral versus unilateral for STN and GPi targets. 2.) To compare laryngeal function during volitional and induced cough tasks pre-post DBS, and when DBS placement is bilateral versus unilateral for STN and GPi targets. 3.) To compare airway safety associated with laryngeal onset, degree, and duration of maximum closure during swallowing, pre-post DBS, and when DBS placement is bilateral versus unilateral for STN and GPi targets. These hypotheses were developed based on compelling published and unpublished preliminary data. We will accomplish these aims by enrolling people with PD who are being considered for DBS surgery. We will measure physiologic, functional, and quality of life parameters of voice, swallow and cough pre- and post-surgically. The realization of the proposed aims is significant because it will address a substantial gap in our understanding of DBS outcomes related to communication and airway protection, which are important in terms of morbidity, mortality, and quality of life for patients with PD. The translational potential to provide additional guidance to DBS surgical teams regarding whether voice, swallow or cough functions should be considered with selecting DBS target and/or laterality is high. Ultimately, the project fits squarely within the overarching goal of the research team to deliver the best possible care to people with PD.