Research Insights

Effect of deep brain stimulation on speech performance in Parkinson’s disease.


Effect of deep brain stimulation on speech performance in Parkinson’s disease. Effect of deep brain stimulation on speech performance in Parkinson’s disease. Epub, S. Parkinsons Dis. 2012;2012:850596. doi: 10.1155/2012/850596. Epub 2012 Nov 21.

Intro:  Difficulties with speech are a common finding in people with Parkinson’s (PWP) that can occur at any point in the disease.  Some may have soft, low speech (hypophonia) while others have challenges initiating talking or experience slurring (dysarthria).  All of the speech difficulties can lead to significant frustration for the PWP as well as a reduction in interacting with others.  Speech therapy has shown benefits to improve speech in PWP, while medicinal (e.g. dopamine) and surgical (ablative and stimulation) treatments have shown considerable variability.  The goal of this article was to review the literature regarding DBS, speech, and PWP.

Methods:  The author reviewed 35 studies, completed in 2012 or earlier, that evaluated speech in PWP that underwent DBS.  Most of the studies looked at DBS-STN and the author noted that there were many differences in procedures, as well as the instruments used to measure speech, which made it difficult to compare each study to one another.

Findings/Conclusions:   After review of the available articles, the author discussed continued variability in DBS effects on speech in PWP.  The author attempted to find predictive trends usable to help PWP and their treatment teams plan the most efficacious treatments in regards to motor improvement and speech.  Although no definitive pattern surfaced, the studies suggested that there might be both positive and negative effects of DBS on speech.  Some of the studies showed improvement after DBS in vocal tremor and hypophonia while others showed worsening dysarthria.  The etiology of speech dysfunction also remained elusive in this review.  The author hypothesized, based on the studies, that if a PWP had significant motor impairment prior to DBS that the person had a higher chance of speech difficulties after implantation.  However, such decisions regarding treatment often are made for optimal motor control versus speech symptoms.  The author also noted that attention to speech problems after DBS is necessary and attempts at optimal stimulator settings may alleviate the speech difficulties.  Different stimulator placement sites were also briefly discussed with some indication that there were less dysarthric adverse events with DBS GPi (globus pallidus interna) than DBS STN but the number of studies were small with small numbers of PWP in each study.  Other sites such as caudal zona incerta (cZi) and ventral intermediate nucleus of the thalamus (Vim) simply needed more studies to draw conclusions about speech.  Simply put, more research on speech in PWP is necessary in order to better understand the causes and predict which patients may be at a higher risk of developing or experiencing worsening of speech difficulties.  The studies should look at speech before and after DBS and utilize multiple measurements to evaluate speech, including subjective ratings from the PWP themselves and/or family members.  The goal of DBS ultimately is improved
motor control but ability to talk is quite important in one’s quality of life.

Click here to read the abstract.


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