Swallowing Evaluation in Patients With Unilateral Vocal Fold Immobility

Assessment of vocal fold movement through anterior-posterior view of videofluoroscopic swallowing study

Objective

The aim of this study is to assess the value of using videofluoroscopic swallowing study (VFSS) for assessing vocal fold paralysis.

Methods

This was a retrospective study of patients who underwent VFSS with a vocal fold testing maneuver from June 2020 to February 2022, and who had undergone laryngoscopy within 2 weeks before or after VFSS. The vocal fold testing maneuver consisted of making an 'e' sound for about 2-3 seconds during VFSS anterior-posterior (AP) view. The diagnostic value of the VFSS was evaluated by a trained reviewer, who assessed the presence and laterality of vocal fold paralysis by examining videos of the patients performing the vocal fold testing maneuver. Intra-rater reliability was determined by evaluation of the videos by the same reviewer 2 weeks later, and inter-rater reliability was determined by evaluation by a second reviewer.

Results

Seventy patients were enrolled in the study. The positive predictive value was 91.43% and the intra-rater and inter-rater reliabilities, as determined by Cohen's kappa value, were 0.746 and 0.824 respectively.

Conclusions

The presence and laterality of vocal fold paralysis were identified accurately and reliably by the reviewers, showing that VFSS can be used to assess vocal fold paralysis.

Level of evidence

2.

Recurrent laryngeal nerve transection in mice results in translational upper airway dysfunction

The recurrent laryngeal nerve (RLN) is responsible for normal vocal-fold (VF) movement, and is at risk for iatrogenic injury during anterior neck surgical procedures in human patients. Injury, resulting in VF paralysis, may contribute to subsequent swallowing, voice, and respiratory dysfunction. Unfortunately, treatment for RLN injury does little to restore physiologic function of the VFs. Thus, we sought to create a mouse model with translational functional outcomes to further investigate RLN regeneration and potential therapeutic interventions. To do so, we performed ventral neck surgery in 21 C57BL/6J male mice, divided into two groups: Unilateral RLN Transection (n = 11) and Sham Injury (n = 10). Mice underwent behavioral assays to determine upper airway function at multiple time points prior to and following surgery. Transoral endoscopy, videofluoroscopy, ultrasonic vocalizations, and whole-body plethysmography were used to assess VF motion, swallow function, vocal function, and respiratory function, respectively. Affected outcome metrics, such as VF motion correlation, intervocalization interval, and peak inspiratory flow were identified to increase the translational potential of this model. Additionally, immunohistochemistry was used to investigate neuronal cell death in the nucleus ambiguus. Results revealed that RLN transection created ipsilateral VF paralysis that did not recover by 13 weeks postsurgery. Furthermore, there was evidence of significant vocal and respiratory dysfunction in the RLN transection group, but not the sham injury group. No significant differences in swallow function or neuronal cell death were found between the two groups. In conclusion, our mouse model of RLN injury provides several novel functional outcome measures to increase the translational potential of findings in preclinical animal studies. We will use this model and behavioral assays to assess various treatment options in future studies.