Aerodynamic Performance and Neuromuscular Control in Patients with Unilateral Vocal Fold Paralysis

Area of Science:

• Laryngology
• Neurology
• Speech Science
• Biomedical Engineering

Background:

• Unilateral vocal fold paralysis (UVFP) impairs glottal function and vocal efficiency.
• The precise relationship between laryngeal neuromuscular control and voice aerodynamics in UVFP is not fully understood.
• Understanding these mechanisms is crucial for developing targeted therapeutic strategies.

Purpose of the Study:

• To investigate the correlation between laryngeal muscle activity, quantified via laryngeal electromyography (LEMG), and aerodynamic parameters in patients with UVFP.
• To identify specific muscle activation patterns that influence aerodynamic outcomes in UVFP.
• To elucidate the compensatory mechanisms of laryngeal muscles in UVFP and their aerodynamic consequences.

Main Methods:

• Prospective study involving 134 UVFP patients without concurrent cricothyroid (CT) muscle involvement.
• Diagnosis confirmed using videolaryngostroboscopy and LEMG.
• Aerodynamic assessment and quantitative LEMG of the thyroarytenoid-lateral cricoarytenoid (TA-LCA) and CT muscles were performed.
• Stepwise linear regression analysis was employed to determine relationships between LEMG and aerodynamic parameters.

Main Results:

• The lesioned vocal fold side exhibited lower peak turn frequency in both TA-LCA and CT muscles compared to the normal side.
• TA-LCA muscle turn ratio was significantly associated with decreased peak expiratory airflow, mean airflow during voicing, and aerodynamic power, but increased aerodynamic efficiency.
• CT muscle turn ratio was significantly associated with increased aerodynamic resistance.
• Even without direct CT involvement, UVFP showed CT muscle suppression on the lesioned side, indicating neurological influence.

Conclusions:

• Neurological impairment of the TA-LCA complex can lead to asymmetrical CT muscle compensation, negatively impacting voice aerodynamics.
• Residual TA-LCA muscle function is beneficial, reducing air leakage and power dissipation, thereby enhancing aerodynamic efficiency.
• Symmetrical compensation of CT muscles appears to improve aerodynamic resistance, highlighting the complex interplay of laryngeal muscle function in UVFP.