Defining Speech Subtypes in De Novo Parkinson Disease: Response to Long-term Levodopa Therapy.

Background and Objectives: Patterns of speech disorder in Parkinson9s disease (PD), that are highly variable across individual patients, were not systematically studied. Our aim was to identify speech subtypes in treatment-naive PD patients and examine their response to long-term dopaminergic therapy. Methods: We recorded speech data from a total of 111 de-novo PD participants; 83 of the participants completed the 12-month follow-up (69 PD subjects on stable dopaminergic medication and 14 untreated PD controls). Unsupervised k-means cluster analysis was performed on eight distinctive parameters of hypokinetic dysarthria examined using quantitative acoustic analysis. Results: Three distinct speech subtypes with similar prevalence, symptom duration and motor severity were detected: 9prosodic9, 9phonatory-prosodic9 and 9articulatory-prosodic9. Beside monopitch and monoloudness that were common in each subtype, speech impairment was more severe in phonatory-prosodic subtype with predominant dysphonia and articulatory-prosodic subtype with predominant imprecise consonant articulation than in prosodic subtype. Clinically, the prosodic subtype was characterized by a prevalence of women and younger age while articulatory-prosodic subtype by the prevalence of men, older age, greater severity of axial gait symptoms and poorer cognitive performance. Phonatory-prosodic subtype clinically represented intermediate status in age with mostly men and preserved cognitive performance. While speech of untreated PD controls deteriorated over one year (p = 0.02), long-term dopaminergic medication maintained stable speech impairment severity in prosodic and articulatory-prosodic subtypes and improved speech performance in patients with phonatory-prosodic subtype (p = 0.002). Discussion: Distinct speech phenotypes in de-novo PD reflect divergent underlying mechanisms and allow to predict response of speech impairment to levodopa therapy. Classification of Evidence: This study provides Class II evidence that, in patients with newly diagnosed PD with speech impairment, speech phenotype is associated with levodopa responsiveness.