Abstract
Purpose. To investigate the impact of deep brain stimulation of the subthalamic nucleus (STN DBS) and levodopa intake on vowel articulation in dysarthric speakers with Parkinson's disease (PD). Methods. Vowel articulation was assessed in seven Quebec French speakers diagnosed with idiopathic PD who underwent STN DBS. Assessments were conducted on- and off-medication, first prior to surgery and then 1 year later. All recordings were made on-stimulation. Vowel articulation was measured using acoustic vowel space and formant centralization ratio. Results. Compared to the period before surgery, vowel articulation was reduced after surgery when patients were off-medication, while it was better on-medication. The impact of levodopa intake on vowel articulation changed with STN DBS: before surgery, levodopa impaired articulation, while it no longer had a negative effect after surgery. Conclusions. These results indicate that while STN DBS could lead to a direct deterioration in articulation, it may indirectly improve it by reducing the levodopa dose required to manage motor symptoms. These findings suggest that, with respect to speech production, STN DBS and levodopa intake cannot be investigated separately because the two are intrinsically linked. Along with motor symptoms, speech production should be considered when optimizing therapeutic management of patients with PD.
Highlights
Parkinson’s disease (PD) is commonly viewed as a multisystemic degenerative disorder [1]
These results show that, independently of each other, STN DBS and medication help reduce motor symptoms in participants
Our results suggest that vowel articulation impairment is associated with high levodopa dose and that articulation impairment could even be a side effect of high levodopa use
Summary
Parkinson’s disease (PD) is commonly viewed as a multisystemic degenerative disorder [1]. Studies examining physiological changes in the speech systems of people with PD reported altered respiratory [3], laryngeal [4], and orofacial [5, 6] functions. These motor manifestations have impacts on the acoustic signal of speech, such as reduced intensity level [7] and fundamental frequency (f0) range [8], altered phonation quality [9], and inaccurate and reduced articulation [10,11,12]. These motor, acoustic, and perceptual changes are grouped under the term “hypokinetic dysarthria” [14]
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