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

Abstract

BACKGROUND AND OBJECTIVES\nPatterns of speech disorder in Parkinson s disease (PD), that are highly variable across individual patients, were not systematically studied. Our aim was to identify speech subtypes in treatment-naïve PD patients and examine their response to long-term dopaminergic therapy.\n\n\nMETHODS\nWe 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.\n\n\nRESULTS\nThree distinct speech subtypes with similar prevalence, symptom duration and motor severity were detected: prosodic , phonatory-prosodic and articulatory-prosodic . 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).\n\n\nDISCUSSION\nDistinct speech phenotypes in de-novo PD reflect divergent underlying mechanisms and allow to predict response of speech impairment to levodopa therapy.\n\n\nCLASSIFICATION OF EVIDENCE\nThis study provides Class II evidence that, in patients with newly diagnosed PD with speech impairment, speech phenotype is associated with levodopa responsiveness.