Amplitude Performance Subtypes in Parkinson's Disease

Purpose: The purpose of this study was to identify subgroups of talkers with Parkinsons disease (PD) with shared tongue, lip, and jaw articulatory amplitude behaviors. The study also sought to identify demographic and clinical features that can distinguish the identified kinematic subgroups. Methods: 53 talkers with PD and 54 controls participated. Articulatory amplitudes of the tongue, lip, and jaw were measured during a paragraph reading task using three-dimensional electromagnetic articulography. Amplitude performance profiles of the tongue, lip, and jaw were established for each talker with PD by referencing their performance to that of controls. These profiles were submitted to a hierarchical cluster analysis to identify kinematic-based subgroups. Amplitude performances were compared across subgroups to determine between-group patterns. Demographic and clinical features (e.g., age, sex, disease duration, selected perceptual speech characteristics, dysarthria severity) were compared across the identified kinematic subgroups. Results: Four main kinematic subgroups with differing amplitude performance profiles were identified. One subgroup exhibited normal to mildly exaggerated or mildly reduced amplitudes and was labeled preclinical subgroup (n = 16). Three subgroups exhibited pronounced amplitude reductions of either the tongue (n = 10), the tongue and lips (n = 12), or the tongue, lips, and jaw (n = 10). In addition, there were five talkers with PD whose performance profiles did not align with the identified four subgroups. Their performance was characterized by either pronounced amplitude exaggerations or mildly reduced jaw and lip amplitudes and exaggerated tongue amplitudes. None of the demographic or clinical features differed significantly between the main four subgroups. Conclusion: Findings suggest that the extent to which hypokinesia manifests within the articulatory subsystem can vary in talkers with PD. Longitudinal studies are needed to determine if these subgroups represent different stages of disease progression or distinctly different manifestations of the disease within the articulatory subsystem.