Laryngeal and phonatory dysfunction in Parkinson's disease

Abstract

The vocal function of 20 speech-disordered subjects with idiopathic Parkinson's disease (PD) was assessed using both perceptual and instrumental techniques. The instrumental analysis included electroglottography and the use of a computerized airflow/air pressure analysis system (Aerophone II). Variables measured included parameters of the Lx waveform (F0, duty cycle, and closing time) as well as aerodynamic parameters such as subglottal pressure, laryngeal airway resistance, average phonatory sound pressure level, phonatory flow rate and ad/abduction rate. Values were compared to those recorded from a group of non-neurologically impaired controls matched for age and sex. Perceptual assessment revealed that 89·5% of the PD subjects exhibited deviant laryngeal features. None of the electroglottography (EGG) parameters differed significantly between the PD and control groups. However four of the five aerophone parameters did differentiate between the two subject groups. The PD group was characterized by higher levels of glottal resistance than the control subjects and lower values for subglottal pressure, average phonatory sound pressure level and phonatory flow rate. A cluster analysis based on the EGG and aerodynamic measures identified the presence of four subgroups, two which represented different expressions of hyperfunction of the larynx within the PD group. The results are discussed with reference to the expected effects of PD on vocal function.