Laryngeal somatosensory deficits in Parkinson's disease: implications for speech respiratory and phonatory control

Abstract

Parkinson's disease (PD) is often associated with substantial impairment of speech respiratory and phonatory control. However, the degree to which these impairments are related to abnormal laryngeal sensory function is unknown. This study examined whether individuals with PD exhibited abnormal and more asymmetric laryngeal somatosensory function compared with healthy controls, and whether these deficits were associated with disease and voice severity. Nineteen PD participants were tested and compared with 18 healthy controls. Testing included endoscopic assessment of laryngeal somatosensory function, with aerodynamic and acoustic assessment of respiratory and phonatory control, and clinical ratings of voice and disease severity. PD participants exhibited significantly abnormal and asymmetric laryngeal somatosensory function compared with healthy controls. Sensory deficits were significantly associated with timing of phonatory onset, voice intensity, respiratory driving pressure, laryngeal resistance, lung volume expended per syllable, disease severity, and voice severity. These results suggest that respiratory and phonatory control are influenced by laryngeal somatosensory function, that speech-related deficits in PD are related to abnormal laryngeal somatosensory function, and that this function may degrade as a function of disease severity. Thus, PD may represent a model of airway sensorimotor disintegration, highlighting the important role of the basal ganglia and related neural networks in the integration of laryngeal sensory input for speech-related motor control.

Fig. 1

Block diagram of stimulus delivery paradigm (Hammer 2009) (reprinted with permission, ©2009 IEEE). The air stimulus is directed to the laryngeal mucosa through a port in the laryngoscope as visualized on the monitor. A +5 V signal from a hand-held switch indicates when the participant feels the laryngeal somatosensory stimulus

Fig. 2

Endoscopic assessment of laryngeal somatosensory function for control and PD participants. Bar height represents mean with standard deviation for each group in mm Hg (1 mm Hg = 133.32 Pa). a Laryngeal mechanosensory detection threshold (LMDT, P < 0.001). b Absolute magnitude of LMDT asymmetry (P < 0.002)