Effects of age, disease, and L-dopa on estimated subglottic pressure in parkinsonian dysarthria
Résumé
Introduction Parkinson’s disease (PD) represents a specific disorder of the central nervous system, characterized by chronic dysfunction of the basal ganglia, which plays an essential role in controlling the execution of learned motor plans. If the motor expression of the symptoms involves mainly the limbs, the muscles involved in speech production are also subject to specific dysfunctions grouped under the term dysarthria (Pinto & Ghio, 2008). The main objective of our study is to compare the aerodynamic performances between healthy and pathological subjects in order to identify if the aerodynamic pa- rameters allow to characterize the parkinsonian speech and what are the parameters of variations (disease, age, sex, L-DOPA treatment).
Methods Our corpus consists of 40 speakers (20 parkinsonian patients + 20 control subjects) recorded in the Neurology Department of the Centre Hospitalier du Pays d’Aix in Aix-en-Provence (Ghio et al., 2012). The speakers were native French-speaking women aged 40 to 90 years. There was no significant difference in age between the two groups. We analyzed subglottic pressure measurements estimated from the peak of intraoral pres- sure during the production of the consonant [p] as well as the pressure decay during the sentence "papa ne m’a pas parlé de beau papa". For Parkinsonian subjects, data were analyzed in the two pharmacological states: with L-DOPA (ON-DOPA) and with with- drawal (OFF-DOPA).
Results & Discussion OFF-DOPA patients have a significantly lower subglottic pressure than controls showing that PD has an impact on the sound pressure level which is significantly lower. In ON-DOPA, the values are similar to those of the controls but only in subjects under 60 years old, after which the pressure is lower. Thus, L-DOPA treatment increases the sound pressure level in subjects under 60 years old but would not improve it consistently. The drop in pressure is greater in the OFF-DOPA condition, particularly at the end of production, indicating a lesser control of pneumo-phonic coordination.
Older healthy subjects produce higher pressure levels than younger healthy subjects with a mean difference of 2 hPa. This increase may be due to two factors: (1) a decrease in lung elasticity that may result in an increase in the value of the pressure measured in the lung volume (Bouhuys, 1977), (2) the need for higher subglottic pressures due to changes in laryngeal airway resistance and vocal fold closure. This increase is not present in ON-DOPA subjects. In contrast, in OFF-DOPA there is an average increase of 0.8 hPa which suggests that people with PD are still able to compensate in vocal efficiency but at much lower levels than control subjects.
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