The impact of STN deep brain stimulation on speech in individuals with Parkinson's disease: The patient's perspective

Background: Speech disturbance is highly prevalent and disabling for individuals with Parkinson's disease (PD). Deep brain stimulation (DBS) has been found to adversely impact speech in a number of individuals with PD. This study investigated the differential speech profiles between individuals with PD with and without DBS from the patient's perspective. Methods: A cross sectional research design was used. A total of 758 individuals with PD participated in this study, including 287 individuals with DBS and 471 individuals without DBS. Participants completed the Voice Handicap Index (VHI) and additional questions regarding speech symptoms and the impact of speech on social interaction. Results: Independent of age and disease duration, there were statistically significant differences in perceived speech disturbance severity between the STN-DBS group and Non-DBS group, with the DBS group reporting more severe symptoms as well as more significant symptom interference with social interaction and with daily experiences encountered relating to functional, physical, and emotional issues of a voice disorder (VHI). Low volume was the most common speech symptom for all individuals with PD patients across both age (younger and older) and disease duration (6-10 years and 11+ years) cohorts. DBS had the greatest adverse impact on slurred speech. Conclusion: DBS therapy's contribution to speech disturbance is gaining more attention, and the speech symptoms ensuing from and/or being exacerbated by DBS are in the incipient stages of being investigated. Implications for DBS therapy on perceived quality of life are discussed. (C) 2014 Elsevier Ltd. All rights reserved.