An Aerodynamic Study of Phonations in Patients With Parkinson Disease (PD)

The precise comparison of the voice characteristics of Parkinson disease (PD) patients with age-matched normal subjects is still one of the important research projects. The present study aimed at comparing the voice characteristics in sustained phonations of PD patients with an age-matched control group.

The subjects were 30 Japanese PD patients (15 males and 15 females). The control group consisted of 30 age-matched normal Japanese subjects (15 males and 15 females). Each subject was required to phonate into a mouthpiece attached to Vocal Function Analyzer (PS-77E; Nagashima Medical Instrumental Corporation, Tokyo, Japan) with the airway interruption system, and expiratory lung pressure, mean flow rate, fundamental frequency and intensity of voice, and pitch range were measured. Maximum phonation time was also assessed.

The highest pitch level was significantly lower in the PD group than that of the control group in both sexes, whereas the lowest pitch level was significantly higher in the PD group only in males. In both sexes, the pitch range was significantly narrower in the PD group than in the control group. There was no significant difference in intensity, mean flow rate, expiratory pressure, or maximum phonation time between the two groups, for both males and females.

Only remarkable difference in the voice characteristics between PD patients and age-matched normal elderlies was limited to the narrowing of the pitch range in PD patients. The restriction in pitch regulation in PD patients was considered to be because of difficulty in reciprocal control of the laryngeal muscles secondary to latent rigidity.