Laryngeal muscle activity in unilateral vocal fold paralysis patients using electromyography and coronal reconstructed images

Scaffold-Forming Collagen and Motor-Endplate Expressing Muscle Cells for Porcine Laryngoplasty

OBJECTIVE

Vocal fold paralysis impairs quality of life, and no curative injectable therapy exists. We evaluated injection of a novel in situ polymerizing (scaffold-forming) collagen in the presence and absence of muscle-derived motor-endplate expressing cells (MEEs) to promote medialization and recurrent laryngeal nerve (RLN) regeneration in a porcine model of unilateral vocal fold paralysis.

METHODS

Twelve Yucatan minipigs underwent right RLN transection. Autologous muscle progenitor cells were isolated from muscle biopsies, differentiated, and induced to MEEs. Three weeks after RLN injury, animals received injections of collagen, collagen containing MEEs, or saline into the paralyzed right vocal fold. Stimulated laryngeal electromyography and acoustic vocalization were used for function assessments. Larynges were harvested and underwent histologic, gene expression, and further quantitative analyses.

RESULTS

Injections were well-tolerated, with the collagen scaffold showing immunotolerance and collagen-encapsulated MEEs remaining viable. Collagen-treated paralyzed vocal folds showed increased laryngeal adductor muscle volumes relative to that of the uninjured side, with those receiving MEEs and collagen showing the highest volumes. Muscles injected with MEEs and collagen demonstrated increased expression of select neurotrophic (BDNF and NTN1), motor-endplate (DOK7, CHRNA1, and MUSK), and myogenic (MYOG and MYOD) related genes relative to saline controls.

CONCLUSION

In a porcine model of unilateral vocal fold paralysis, injection of in situ polymerizing collagen in the absence and presence of MEEs enhanced laryngeal adductor muscle volume, modulated expression of neurotrophic and myogenic factors, and avoided adverse material-mediated immune responses. Further study is needed to determine long-term functional outcomes with this novel therapeutic approach.

LEVEL OF EVIDENCE

NA Laryngoscope, 2024.

Dynamic CT Study on the Morphology and the Motor Ability of Unilateral Vocal Fold Paralysis

OBJECTIVE

To investigate the morphological changes and motor functions of the larynx in unilateral vocal fold paralysis by using dynamic three-dimensional CT, and to explore the differences between vocal fold paralysis with different nerves involved.

METHODS

Twenty-five patients with unilateral vocal fold paralysis and 10 healthy subjects were selected as the paralytic group and the normal group, respectively. Ten dynamic sequence images of laryngeal movement from inhalation to phonation were reviewed, and the glottic morphology at the coronal position, the minimum glottic area at the horizontal position, and the overall activity of the two groups were compared. The 25 patients with unilateral vocal fold paralysis were divided into the thyroarytenoid (TA) muscle group, the TA and posterior cricoarytenoid (PCA) (TA + PCA) muscle group, and the PCA muscle group. The coronal and horizontal parameters of the three types were compared as noted above and the dynamic parameter changes were also compared between the groups.

RESULTS

The height and thickness of bilateral vocal cords, the minimum glottic area, and the whole glottic activity were different in the paralysis group and were significantly different from those of the normal group (P < 0.05). The value of the glottic gap ratio and its decrease rate in the TA + PCA group was smaller than those in the TA and PCA group, and the glottic gap ratio was the largest in the PCA group.

CONCLUSION

Dynamic CT can provide a qualitative evaluation of laryngeal morphology and quantitative evaluation of motor function in vocal fold paralysis.

LEVEL OF EVIDENCE: 4

Phonation Threshold Pressure/Flow for Reflecting Glottal Closure in Unilateral Vocal Fold Paralysis

OBJECTIVE

Previous theoretical analysis predicted that phonation threshold flow (PTF) could be a more sensitive aerodynamic measure than phonation threshold pressure (PTP) for reflecting glottal incompetence. This study investigated the feasibility of whether PTP and PTF may differentiate subjects with unilateral adductor vocal fold paralysis and paresis (UAVFP) from those without, and whether PTP and PTF could reflect the extent of incomplete glottal closure associated with UAVFP.

METHODS

PTP and PTF were quantified for 13 subjects with UAVFP and 21 control subjects with normal voice, and the normalized glottal gap area (NGGA) based on videostroboscopic image analysis was quantified for subjects with UAVFP.

RESULTS

Significant differences in both PTP and PTF were found between subjects with UAVFP and control subjects. Receiver operating characteristic analysis indicated a higher discriminatory ability of PTP for differentiating subjects with UAVFP from those without (area under the curve of 0.905 for PTP, 0.678 for PTF), yet a significant positive correlation was found between PTF and NGGA (Spearman's ρ = 0.571) but not between PTP and NGGA (ρ = -0.364).

CONCLUSION

Results supported the feasibility of using PTP and PTF as potential diagnostic indicators for reflecting glottal closure in UAVFP, with PTP potentially more sensitive for differentiating subjects with and without incomplete glottal closure. These preliminary findings were limited by the small sample size, with further studies needed to verify whether PTF could be more sensitive for reflecting the extent of incomplete glottal closure, as predicted theoretically.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:E1598-E1604, 2021.

Volumetric measures of the paralyzed vocal fold using computerized tomography; its clinical implication

OBJECTIVE

To report the volumetric measures of the paralyzed vocal fold in patients undergoing injection laryngoplasty.

MATERIAL AND METHOD

All the medical records of patients with unilateral vocal fold paralysis who had high resolution computerized tomography scan of the neck and chest prior to injection laryngoplasty between October 2015 and May 2018 were included. Volumetric evaluation of the vocal folds was performed by measuring the vocal fold height using coronal images and the vocal fold length and width using axial images.

RESULTS

A total of 21 patients divided into 13 males and 8 females were identified. The mean age was 56.66 ± 20.94 years. The mean volume of the paralyzed vocal fold was significantly smaller than that of the non-paralyzed vocal fold (p < .05). Similarly, the mean length and height of the paralyzed vocal folds were smaller than those of the non-paralyzed vocal folds (p < .05).

CONCLUSION

Volumetric measurements of the paralyzed vocal fold in comparison to the normal vocal fold in a group of 21 patients with unilateral vocal fold paralysis shows the presence of significant difference between the normal and affected site, and the presence of large inter-subject variation. Information on the volume difference between the two vocal folds may be used to better estimate the amount that needs to be injected in medialization procedures.

Laryngeal Reinnervation Featuring Refined Nerve-Muscle Pedicle Implantation Evaluated via Electromyography and Use of Coronal Images

Objective

To evaluate the long-term efficacy of laryngeal reinnervation via refined nerve-muscle pedicle (NMP) flap implantation combined with arytenoid adduction to treat unilateral vocal fold paralysis (UVFP), employing laryngeal electromyography (LEMG), coronal imaging, and phonatory function assessment.

Study Design

Case series with chart review.

Setting

University hospital.

Subjects and Methods

We retrospectively reviewed 12 UVFP patients who underwent refined NMP implantation with arytenoid adduction. Videostroboscopy, phonatory functional analysis, LEMG, and coronal imaging were performed before and 2 years after surgery. In LEMG analysis, a 4-point scale was employed to grade motor unit (MU) recruitment: 4+ reflected no recruitment, 3+ greatly decreased recruitment, 2+ moderately decreased recruitment, and 1+ mildly decreased activity, associated with less than the full interference pattern. Coronal images were assessed in terms of differences in thickness and the vertical positions of the vocal folds.

Results

Phonatory function improved significantly after operation in all patients. In terms of LEMG findings, the preoperative MU recruitment scores were 1+ in no patients, 2+ in 4 patients, 3+ in 1 patient, and 4+ in 7 patients. Postoperative MU recruitment results were 1+ in 6 patients, 2+ in 5 patients, 3+ in 1 patient, and 4+ in no patients. Thinning of the affected fold during phonation was evident preoperatively in 9 of 10 patients. The affected and healthy folds were equal in volume in 4 of 9 patients postoperatively.

Conclusion

The LEMG findings and coronal imaging suggest that NMP implantation may have enabled successful reinnervation of the laryngeal muscles of UVFP patients.

Vocal fold paralysis: improved adductor recovery by vincristine blockade of posterior cricoarytenoid

OBJECTIVES/HYPOTHESIS

A new treatment for acute unilateral vocal-fold paralysis (UVFP) was proposed in which a drug is injected into the posterior cricoarytenoid muscle (PCA) shortly after nerve injury, before the degree of natural recovery is known, to prevent antagonistic synkinetic reinnervation. This concept was tested in a series of canine experiments using vincristine as the blocking agent.

STUDY DESIGN

Animal experiments.

METHODS

Laryngeal adductor function was measured at baseline and at 6 months following experimental recurrent laryngeal nerve (RLN) injuries, including complete transection, crush injury, and cautery. In the treatment animals, the PCA was injected with vincristine at the time of RLN injury.

RESULTS

Adductor function in the vincristine-treated hemilarynges was significantly improved compared with injury-matched noninjected controls (total n = 43). Transection/repair controls recovered 56.1% of original adductor strength; vincristine-treated hemilarynges recovered to 73.1% (P = 0.002). Cautery injuries also improved with vincristine block (60.7% vs. 88.7%; P = 0.031). Crush injuries recovered well even without vincristine (104.8% vs. 111.2%; P = 0.35).

CONCLUSION

These findings support a new paradigm of early, preemptive blockade of the antagonist muscle (PCA) to improve ultimate net adductor strength, which could potentially improve functional recovery in many UVFP patients and avoid the need for medialization procedures. Possible clinical aspects of this new approach are discussed.