The Causes and Laryngeal Electromyography Characteristics of Unilateral Vocal Fold Paralysis

A comparative analysis of laryngeal nerve damage in patients with idiopathic vocal cord paralysis exhibiting different paralytic sides

Objective

To assess the extent of recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN) damage in patients with idiopathic vocal cord paralysis (IVCP) exhibiting different paralytic sides.

Methods

A total of 84 IVCP cases were evaluated using stroboscopic laryngoscopy, voice analysis, and laryngeal electromyography (LEMG). The results were compared between patients with left-sided paralysis and right-sided paralysis based on different disease courses (less than or more than 3 months).

Results

Initially, the average age and disease progression of IVCP patients were found to be similar regardless of the side of paralysis (p > .05). Additionally, there were no significant variations in voice indicators, such as MPT, DSI, and VHI, between IVCP patients with left and right vocal cord paralysis (p > .05). Furthermore, no disparities were detected in the latencies and amplitudes of the paralyzed RLN and SLN, as well as the durations and amplitudes of the action potentials in the paralyzed TM and PCM, among IVCP patients with left and right vocal cord paralysis (p > .05). Notably, the amplitudes of the left paralytic CM were significantly lower than those of the right paralytic CM (0.45 vs. 0.53, Z = -2.013, p = .044). In addition, no disparities were observed in APDs and amplitudes between the ipsilateral PCM and TM, either for patients with left or right vocal fold paralysis (p > .05). Finally, all the IVCP patients were subdivided into two subgroups according to different disease course (less than or more than 3 months), and in each subgroup, the comparison of voice indicators and LEMG results in IVCP patients with left or right vocal fold paralysis were similar with the above findings (p > .05).

Conclusion

Overall, the degree of RLN and SLN damage appeared to be similar in IVCP patients with left and right vocal cord paralysis, provided that the disease course was comparable.

Level of Evidence

4.

Improvement in swallowing safety after injection laryngoplasty in patients with unilateral vocal paralysis complicated with aspiration

BACKGROUND

The benefit of injection laryngoplasty (IL) on voice for unilateral vocal fold paralysis (UVFP) is supported increasingly in literatures, yet less is known for swallowing. Also, prevalence of patient-reported dysphagia is substantially higher than instrumental studies. This prospective study focused on swallowing outcomes, with predetermined flexible endoscopic evaluation of swallowing (FEES) protocol that simulates daily life situation.

METHODS

Adult patients with UVFP and aspiration receiving IL were recruited. Voice outcome measurements, as well as swallowing outcomes including Eating Assessment Tool (EAT-10) and FEES, which challenged patients with different fluid volumes: 10 mL, 20 mL, and 90 mL cup sipping were evaluated.

RESULTS

Significant improvements were demonstrated in all voice outcomes. Significant changes were also presented inEAT-10 (P < 0.01). Pre-operatively, penetration-aspiration scale (PAS) was 1.5 ± 1.3, 1.9 ± 1.7 and 2.3 ± 1.8 for 10 mL, 20 mL and 90 mL serial sipping, and improved to 1.1 ± 0.3, 1.1 ± 0.4 and 1.4 ± 0.7 post-operatively (P < 0.01). Safe swallowing (PAS ≤ 2) was achieved in all, except for one patient, who presented with a post-injection PAS of 4 (material enters the airway, contacts the vocal folds, and is ejected from the airway) on 90 mL cup sipping, whose pre-injection PAS was 7 (residue in trachea).

CONCLUSION

Maintaining swallowing function suitable for social environment is important. Our results demonstrated the feasibility of the predetermined FEES protocol, and positive effects of IL on both voice and swallowing outcomes.

Experimental Injury Rodent Models for Oropharyngeal Dysphagia

Oropharyngeal dysphagia is a disorder that can make swallowing difficult and reduce the quality of life. Recently, the number of patients with swallowing difficulty has been increasing; however, no comprehensive treatment for such patients has been developed. Various experimental animal models that mimic oropharyngeal dysphagia have been developed to identify appropriate treatments. This review aims to summarize the experimentally induced oropharyngeal dysphagia rodent models that can be used to provide a pathological basis for dysphagia. The selected studies were classified into those reporting dysphagia rodent models showing lingual paralysis by hypoglossal nerve injury, facial muscle paralysis by facial nerve injury, laryngeal paralysis by laryngeal and vagus nerve injury, and tongue dysfunction by irradiation of the head and neck regions. The animals used in each injury model, the injury method that induced dysphagia, the screening method for dysphagia, and the results are summarized. The use of appropriate animal models of dysphagia may provide adequate answers to biological questions. This review can help in selecting a dysphagia animal system tailored for the purpose of providing a possible solution to overcome dysphagia.