Clin Exp Otorhinolaryngol.  2023 Nov;16(4):395-402. 10.21053/ceo.2023.01046.

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

• Lu YA
• Tsai YC
• Lin WN
• Pei YC
• Fang TJ

• KMID: 2548368
• DOI: http://doi.org/10.21053/ceo.2023.01046

Abstract

Objectives
. Laryngeal ultrasonography (LUS) has been suggested as an alternative diagnostic tool for unilateral vocal fold paralysis (UVFP). The present study applied LUS and quantitative laryngeal electromyography (LEMG) in female UVFP patients to investigate the pathophysiologic mechanisms of UVFP.
Methods
. In this cross-sectional study, vocal fold (VF) length parameters included resting and phonating VF length measured using B-mode LUS, and color Doppler vibrating length (CDVL) measured using the color Doppler mode.
Results
. Forty female patients with UVFP were enrolled, among whom 11 and 29 were assigned to the thyroarytenoid (TA) muscle+cricothyroid (CT) muscle group (with CT involvement) and the TA (without CT involvement) group, respectively. In the TA group, the turn frequency in thyroarytenoid-lateral cricoarytenoid (TA-LCA) on the paralyzed side, as observed through LEMG, correlated with the VF length during the resting phase (R=0.368, P=0.050) and CDVL values (R=0.627, P=0.000) on the paralyzed 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 paralyzed 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 noninvasive tool, can serve as an alternative method for assessing the severity of laryngeal nerve injury and offer valuable insights into the pathophysiology of UVFP.

Keyword

Vocal Fold Paralysis; Ultrasonography; Laryngeal Electromyography; Doppler; Color; Superior Laryngeal Nerve

Figure

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  Fig. 1. Experimental flowchart of subject enrollment, exclusion, allocation, and analysis. UVFP, unilateral vocal fold paralysis; LEMG, laryngeal electromyography; TA, thyroarytenoid; CT, cricothyroid.

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  Fig. 2. (A) Patients were seated on a reclining laryngeal examination chair with their neck extended and head supported by an adjustable neck-head set. (B) The transducer was placed transversely over the thyroid cartilage lamina as the acoustic window. (C) The hyperechoic dot located behind the thyroid cartilage represents the anterior commissure (arrow). The arytenoid cartilages are observed as hyperechoic structures behind the vocal folds (VFs; arrowhead). The distance between the anterior commissure and arytenoid cartilages is defined as the VF length. (D) A schematic demonstration of color Doppler vibrating length (CDVL) measurements. During phonation, the anterior end is the point of attachment to the anterior commissure (arrow). The posterior end of the VF is the crossing point between the air-mucosa interface (solid line) and the lateral boundary of the color artefact contour (dashed line). CDVL is as the distance between the anterior and posterior ends.

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  Fig. 3. (A) Vocal fold length on the healthy and paralyzed sides during resting and phonation phase. (B) Normalized phonatory length change (nPLC) on the healthy and paralyzed sides. *P<0.05, ***P<0.01.

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