PURPOSE: Communication difficulties in Parkinson’s Disease (PD) are multifactorial. Observing cardinal motor symptoms may be insufficient in qualifying speech dysfunction in people with Parkinson’s Disease (PwPD). This study aimed to use high-speed video (HSV) endoscopy to explore the use of three measures of laryngeal kinematics – spatiotemporal index, asymmetry index, and kinematic stiffness ratio – as a novel means of examining vocal motor control in PD, to better understand the pathophysiology of PwPD within the phonatory subsystem.
METHOD: 24 PwPD and 24 age- and sex-matched controls were trained to produce repetitions of a VCV target, /ifi/, while varying their speech rate and vocal effort during simultaneous HSV nasoendoscopic and acoustic recordings. Kinematic measures were calculated from HSV recordings during vocal fold adduction using both manual glottal angle tracking and a semi-automated algorithm. Six separate repeated measures analyses of variance (ANOVAs) were completed to determine the spatiotemporal index, asymmetry index and kinematic stiffness ratio, with main effects of group and condition (fast rate, regular rate, slow rate, mild effort, moderate effort, maximum effort). Alpha levels < .05 were considered statistically significant. Effect sizes of significant differences were calculated by using partial eta squared.
RESULTS: The repeated ANOVAs showed a statistically significant effect of group on spatiotemporal index values across both rate (p < .01) and effort (p <.05) and on asymmetry index values across rate (p < .01). No statistically significant main effect of rate or effort or interaction effects between group × rate or group × effort were observed for all kinematic measures.
CONCLUSION: This study determined that spatiotemporal index, a measure of variability in movement, and asymmetry index, a measure of movement efficiency, are significantly higher for PwPD compared to controls. These findings are consistent with increased variability and reduced efficiency observed in other speech subsystems in PwPD. Further research is recommended to explore the use of laryngeal kinematics in characterizing the pathophysiology of the laryngeal subsystem in PwPD
