Fig 1.
Annotated CT image at the level of the glottis depicting the laryngeal measures used in this study. Fiducial markers (shown as yellow crosshairs) are placed at the most medial aspect of the arytenoid cartilages (Ar). The inter-arytenoid distance (IAD) is defined as the Euclidean distance between them, as depicted by the arrow. The arytenoid velocity () is equivalent to the change in IAD between successive timepoints (not illustrated). The glottic area (GA) is the segmented area of air density at the level of the vocal folds. Also shown are the thyroid cartilage (Th) and cricoid cartilage (Cr).
Table 1.
Demographic details.
Fig 2.
Comparison of the laryngeal measures during vocalization between pwPD and controls.
Boxplots comparing measures of laryngeal dynamics in participants with Parkinson’s disease (blue boxes) against controls (black boxes). (1-3A) Comparison of the means of the GA, IAD and IAI during the period of vocalization. (1-3B) Comparison of the values of the laryngeal measures at maximal vocal fold adduction, corresponding with the effective minimum GA, effective minimum IAD and effective maximum IAI. The mean and effective maximum velocities of the arytenoids is assessed in (4A) and (4B) respectively, calculated by assessing the extent of movement of the arytenoids between successive 100 ms volumes. Sub-analysis of the maximal velocities by the direction of vocal fold movements is shown in (5A) (adduction; ) and (5B) (abduction;
). ns p>0.05; * p<0.05; ** p<0.01; *** p<0.001.
Fig 3.
Change in laryngeal measures with disease duration and UPDRS part III scores.
Plots of the raw data of the laryngeal measures against duration in months and UPDRS part-III scores. The linear regression ‘line of best fit’ is marked in blue, with the 95% confidence interval shaded in grey. Spearman correlation coefficients (rs) between the laryngeal measures and disease duration or UPDRS are annotated for each. ns p>0.05; * p<0.05; ** p<0.01; *** p<0.001.
Fig 4.
Actions of the main intrinsic laryngeal muscles and the laryngeal abnormalities in Parkinson’s disease.
Schematic diagrams of the larynx viewed from above. The left panel demonstrates the normal anatomy of the main laryngeal cartilages (Th, thyroid cartilage; Cr, cricoid cartilage; Ar, arytenoid cartilages), as well as the main abductors (LCA, lateral cricoarytenoid muscle; TA, thyroarytenoid muscle) and adductor (PCA, posterior cricoarytenoid muscle), with their primary movements depicted by the accompanying arrows. The right panel highlights the prior laryngoscopic findings, as well as the EMG abnormalities described which account for these. The vocal fold bowing explains the increase in glottic area (GA) and IAD-Area Index (IAI) seen on laryngeal CT, while hyperadduction of the arytenoids causes the reduction in inter-arytenoid distance (IAD).