Prognostic value of the posterior cricoarytenoid muscle atrophy in computerized tomography scans for unilateral vocal fold paralysis recovery

Increased 18F-FDG Uptake in the Posterior Region of Contralateral Vocal Folds in Beagle Dogs With Unilateral Vocal Fold Immobility Disorders

OBJECTIVE

To explore the glycolytic metabolism of contralateral vocal fold compensation by examining the glycolytic metabolism of the posterior region of vocal folds in beagles with unilateral vocal fold immobility disorders and its correlation with acoustic parameters.

STUDY DESIGN

Prospective animal study.

SETTING

Department of Voice METHODS: Ten adult beagles were divided randomly into three groups: a unilateral cricoarytenoid joint dislocation (UCAJD) group (n = 4), a unilateral vocal fold paralysis (UVFP) group (n = 4), and a control group (n = 2). Positron emission tomography-computed tomography (PET/CT) scans of larynx and recordings of vocalizations were collected 4 months after the operations. The maximum standardized uptake values (SUVmax) of 18F-FDG within each posterior region of the vocal folds were obtained from PET/CT and voice recordings were analyzed for acoustic parameters F0, jitter, shimmer, and loudness using PRAAT.

RESULTS

In both UCAJD and UVFP groups, a significant increase of SUVmax was observed in the contralateral vocal fold relative to the impaired fold (P < 0.05). The SUVmax values of the contralateral vocal folds and the SUVmax values of the impaired vocal folds in the UCAJD, UVFP, and control groups were both found to be significantly different (P < 0.05). The SUVmax of the contralateral vocal fold may exhibit a potentially negative correlation with jitter and shimmer, with R2 values of 0.42 and 0.26 and P values of 0.03 and 0.11, respectively.

CONCLUSION

UCAJD and UVFP can cause enhanced glycolytic metabolism of the contralateral vocal fold relative to the impaired vocal fold. The SUVmax of the contralateral vocal fold may be positively correlated with acoustic quality.

Selective Electrical Surface Stimulation to Support Functional Recovery in the Early Phase After Unilateral Acute Facial Nerve or Vocal Fold Paralysis

This article addresses the potential clinical value of surface electrical stimulation in the acute phase of denervation after the onset of facial nerve or recurrent laryngeal nerve paralysis. These two nerve lesions are the most frequent head and neck nerve lesions. In this review, we will work out several similarities concerning the pathophysiology features and the clinical scenario between both nerve lesions, which allow to develop some general rules for surface electrical stimulation applicable for both nerve lesions. The focus is on electrical stimulation in the phase between denervation and reinnervation of the target muscles. The aim of electrostimulation in this phase of denervation is to bridge the time until reinnervation is complete and to maintain facial or laryngeal function. In this phase, electrostimulation has to stimulate directly the denervated muscles, i.e. muscle stimulation and not nerve stimulation. There is preliminary data that early electrostimulation might also improve the functional outcome. Because there are still caveats against the use of electrostimulation, the neurophysiology of denervated facial and laryngeal muscles in comparison to innervated muscles is explained in detail. This is necessary to understand why the negative results published in several studies that used stimulation parameters are not suitable for denervated muscle fibers. Juxtaposed are studies using parameters adapted for the stimulation of denervated facial or laryngeal muscles. These studies used standardized outcome measure and show that an effective and tolerable electrostimulation of facial and laryngeal muscles without side effects in the early phase after onset of the lesions is feasible, does not hinder nerve regeneration and might even be able to improve the functional outcome. This has now to be proven in larger controlled trials. In our view, surface electrical stimulation has an unexploited potential to enrich the early therapy concepts for patients with unilateral facial or vocal fold paralysis.

PCA Atrophy and Synkinesis as the Main Factors for Persistent Vocal Fold Immobility in RLN Paralysis

OBJECTIVES/HYPOTHESIS

An immobile vocal fold due to recurrent laryngeal nerve (RLN) injury usually shows no gross signs of atrophy and lies near the midline. In 1881, Felix Semon proposed that this phenomenon was due to a selective injury of nerve fibers supplying the posterior cricoarytenoid muscle (PCA) and supported this with postmortem proof of selective PCA atrophy. In recent decades, evidence has emerged that the RLN regenerates after injury but does not always result in useful motion of the vocal folds. It has been proposed that this is caused by laryngeal synkinesis. Laryngeal synkinesis describes a random distribution of regenerated nerve fibers to opposing vocal fold muscles. This study was conducted to clarify the relative contribution of these two potential pathomechanisms in our patient population.

STUDY DESIGN

Retrospective case analysis.

METHODS

Retrospective analysis of laryngeal EMG results from cases with RLN paralysis of at least 6 months duration seen at our neurolaryngology clinic.

RESULTS

Out of 118 PCA EMGs, there was not a single normal or near-normal tracing, whilst 33.3% of TA EMGs indicated normal or near normal innervation. PCA EMGs showed signs of persistent high-grade partial denervation (41.5%) as a sign of atrophy, moderate or strong synkinesis (21.2%), or a combination of both (37.3%).

CONCLUSIONS

In chronic RLN paralysis the intrinsic laryngeal muscles are affected to different extents either by atrophy or synkinesis or a combination of both. The PCA is always affected. The lesser damage to TA innervation explains the commonly seen maintenance of vocal fold muscle bulk.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1244-E1248, 2021.