Pathophysiological Mechanisms Underlying Unilateral Vocal Fold Paralysis in Female Patients: An Ultrasonographic Study.

OBJECTIVE: Laryngeal ultrasonography has been suggested as an alternative diagnostic tool for unilateral vocal fold paralysis (UVFP). The present study applied laryngeal ultrasonography (LUS) and quantitative laryngeal electromyography (LEMG) in female UVFP patients to investigate the pathophysiologic mechanisms of UVFP.

STUDY DESIGN: prospective cohort study.

METHODS: The vocal fold (VF) length parameters included resting and phonating VF length measured by B-mode LUS, and color Doppler vibrating length (CDVL) measured by color Doppler mode.

RESULTS: Forty female patients with UVFP were enrolled, among whom eleven and 29 were assigned to the TA (thyroarytenoid muscle) +CT (cricothyroid muscle) (with CT involvement) and TA (without CT involvement) groups, respectively. In the TA group, the turn frequency in thyroarytenoid-lateral cricoarytenoid (TA-LCA) on the paralysis side, as observed through LEMG, correlated with the VF length during the resting phase (R=0.368; P=0.050) and CDVL values (R=0.636; P=0.000) on the paralysis side. In the TA+CT group, the turn ratio in the CT muscle correlated with the normalized phonatory vocal length change (nPLC) (R=0.621; P=0.041) on the paralysis side.

CONCLUSION: CDVL and nPLC are two parameters that can be utilized to predict the turn frequencies of TA-LCA in UVFP cases without CT involvement, and the turn ratio of CT in cases of UVFP with CT involvement, respectively. The findings suggest that LUS, as a non-invasive tool, can serve as an alternative method for assessing the severity of laryngeal nerve injury and offer valuable insights into the pathophysiology of UVFP.