Subthalamic Nucleus Deep Brain Stimulation in Speech Study

Parkinson's disease (PD) patients treated with deep brain stimulation (DBS) of the subthalamic nucleus (STN) have unpredictable and varied speech outcomes after this treatment. Our research will prospectively document speech performance before, during and 6- and 12-months after STN-DBS in 80 surgically treated patients and compared with 40 non-surgical controls with Parkinson's disease. This study will provide unique insights into the role of STN in speech production, document speech outcome in a comprehensive fashion, identify factors that predict functional communication ability 12 months after STN-DBS, and test the feasibility of low frequency DBS in reversing DBS-induced speech declines in order to optimize treatment strategies for those living with Parkinson's disease.

Aim 1. Define the mechanistic role of STN in speech using direct intraoperative brain recordings. For the first time, we will define STN neuronal physiology for both speech and limb tasks. Through multichannel microelectrode recording (MER) during awake STN-DBS implantation surgery, we will test the hypothesis suggested by our pilot data that STN firing rate during speech will be significantly different from the firing rate during a limb motor task.

Aim 2. Advance understanding of speech outcomes associated with STN-DBS. Intelligibility will serve as the primary functional communication outcome, with communication participation as a secondary metric. Acoustic measures of articulation, phonatory-respiratory behavior and tempo-fluency will be obtained.

Aim 2A. Determine differential effects of DBS stimulation (ON vs. OFF) on speech outcomes. ON vs. OFF stimulation changes in acoustic measures of speech will be used to inform potential reasons for observed changes in intelligibility.

Aim 2B. Define longitudinal effects of STN-DBS on speech outcomes. Speech outcomes and limb measures obtained pre-surgery will be compared to those at 6 and 12 months post-surgery when DBS stimulation is ON. Change in communication participation also will be defined. The control group studied at similar time points will control for disease progression.

Aim 2C. Determine associations between acoustic measures and intelligibility in STN-DBS.

Aim 3. Explore factors associated with changes in intelligibility post STN-DBS. As initial endeavors to guide future studies, we will:

Aim 3A. Use our metrics from Aims 1 and 2 (e.g. disease-specific characteristics, microelectrode recording data, pre-operative intelligibility) to identify factors that predict intelligibility at 12 months following STN-DBS.

Aim 3B. Test the feasibility of manipulating DBS stimulation parameters to improve intelligibility in a subset of participants with DBS-induced intelligibility declines.

Eligibility Criteria:
Inclusion Criteria:

For inclusion in this study, participants must

* have a confirmed diagnosis of idiopathic Parkinson's disease and no atypical Parkinsonism features
* experience significant motor fluctuations
* currently taking and responsive to dopaminergic medications (e.g. Levodopa)
* use English as their primary language
* lack significant cognitive impairment and be able to consent to participate

Exclusion Criteria:

* Significant hearing loss/reliance on hearing aids