An Aerodynamic Evaluation of Parkinsonian Dysarthria: Laryngeal and Supralaryngeal Manifestations*

The speech of individuals with Parkinson's Disease (PD) is characterized by reduced stress, increased rate, monotonic pitch and loudness and imprecise consonant production (see Darley, Aronson, & Brown, 1975 for review). Acoustically, speech has decreased duration of voiced segments, reduced fundamental frequency variations and limited formant trajectories at consonant-vowel transitions as compared to normal age-matched controls (Canter, 1967; Darley et al., 1975; Forrest, Weismer, & Turner, 1989; Logeman, Fisher, & Boshes, 1978; Ludlow, Bassich, Connor, Coulter, & Lee, 1987; Ludlow & Schulz, 1989; Ramig, Scherer, Titze, & Ringel, 1988; Weismer, 1983). Although specific and detailed analysis of Parkinsonian deficits have been limited, existing studies of larygneal and supralaryngeal structures suggest that the reduction in intelligibility characteristic of Parkinson's disease may be a result of manifestations of this disorder throughout the entire vocal tract musculature. For example, studies of lip and jaw movements have reduced amplitude and velocity (Caligiuri, 1987; Connor, Abbs, Cole, & Gracco, 1989) while cinegraphic studies of laryngeal kinematics in PD (Hanson, Gerratt, & Ward, 1984) reveal a correlation between abnormalities in the phonatory posture of laryngeal structures and voicing deficits. These manifestations may involve the control and coordination of laryngeal and supralaryngeal events. Taken together, these factors result in the overall reduction in speech intelligibility in individuals with PD. Hence, the simultaneous evaluation of upper articulator and laryngeal dynamics may give a more complete