Three-dimensional vocal fold structural change due to implant insertion in medialization laryngoplasty

Acoustics and aerodynamic effects following glottal and infraglottal medialization in an excised larynx model

OBJECTIVE

This study aimed to investigate the impact of the implant's vertical location during Type 1 Thyroplasty (T1T) on acoustics and glottal aerodynamics using excised canine larynx model, providing insights into the optimal technique for treating unilateral vocal fold paralysis (UVFP).

METHODS

Measurements were conducted in six excised canine larynges using Silastic implants. Two implant locations, glottal and infraglottal, were tested for each larynx at low and high subglottal pressure levels. Acoustic and intraglottal flow velocity field measurements were taken to assess vocal efficiency (VE), cepstral peak prominence (CPP), and the development of intraglottal vortices.

RESULTS

The results indicated that the implant's vertical location significantly influenced vocal efficiency (p = 0.045), with the infraglottal implant generally yielding higher VE values. The effect on CPP was not statistically significant (p = 0.234). Intraglottal velocity field measurements demonstrated larger glottal divergence angles and stronger vortices with the infraglottal implant.

CONCLUSION

The findings suggest that medializing the paralyzed fold at the infraglottal level rather than the glottal level can lead to improved vocal efficiency. The observed larger divergence angles and stronger intraglottal vortices with infraglottal medialization may enhance voice outcomes in UVFP patients. These findings have important implications for optimizing T1T procedures and improving voice quality in individuals with UVFP. Further research is warranted to validate these results in clinical settings.

Effects of implant and vocal fold stiffness on voice production after medialization laryngoplasty in an MRI-based vocal fold model

Medialization laryngoplasty is one of the primary surgical interventions in the treatment of glottal insufficiency due to vocal fold paralysis, paresis, or atrophy. During the surgery, an implant is laterally inserted into the larynx to medialize the affected vocal fold toward glottal midline, with the goal of improving glottal closure during phonation and voice production efficiency. While implants of different materials and geometry designs have been used, the effect of implant design on the voice outcome remains unclear. In this simulation study, the effect of implant stiffness was investigated in an MRI-based model of the vocal folds after medialization laryngoplasty. The results showed that implant stiffness had a significant impact on the phonation threshold pressure, glottal area waveform, and fundamental frequency, but only small effect on the closed quotient and other acoustic measures of the produced voice. The effect of implant stiffness also exhibited variability, depending on the stiffness conditions of the vocal fold and paraglottic tissues, indicating that individual differences need to be considered during the planning of medialization laryngoplasty.

Anisotropic minimum dissipation subgrid-scale model in hybrid aeroacoustic simulations of human phonation

This article deals with large-eddy simulations of three-dimensional incompressible laryngeal flow followed by acoustic simulations of human phonation of five cardinal English vowels, /ɑ, æ, i, o, u/. The flow and aeroacoustic simulations were performed in OpenFOAM and in-house code openCFS, respectively. Given the large variety of scales in the flow and acoustics, the simulation is separated into two steps: (1) computing the flow in the larynx using the finite volume method on a fine moving grid with 2.2 million elements, followed by (2) computing the sound sources separately and wave propagation to the radiation zone around the mouth using the finite element method on a coarse static grid with 33 000 elements. The numerical results showed that the anisotropic minimum dissipation model, which is not well known since it is not available in common CFD software, predicted stronger sound pressure levels at higher harmonics, and especially at first two formants, than the wall-adapting local eddy-viscosity model. The model on turbulent flow in the larynx was employed and a positive impact on the quality of simulated vowels was found.

Challenge of Lung Isolation in Patients with Vocal Cord Implants

Glottic closure insufficiency increases the risk of aspiration and pneumonia, particularly in the elderly. Medialization thyroplasty is an open surgical procedure for treating glottic incompetency by approximating both vocal folds. The vocal fold medialization is achieved by inserting an implant to bring the nonmobile fold to the unaffected side. Lung isolation in patients with vocal cord implantation poses a unique challenge. Understanding the risks of different modalities of lung isolation and their impacts on the vocal cord implant is crucial to implementing a specifically tailored plan. Preoperative bronchoscopy, intraoperative video laryngoscopy, and bronchoscopy are ideal methods for assessing the vocal fold implants and guiding the lung isolation technique. Bronchial blocker through a single-lumen endotracheal tube may be the preferred choice to avoid the injury of the stretched vocal cords and dislodgement of the implant by a larger diameter double-lumen tube.

A computational framework for patient-specific surgical planning of type 1 thyroplasty

A computational framework is proposed for virtual optimization of implant configurations of type 1 thyroplasty based on patient-specific laryngeal structures reconstructed from MRI images. Through integration of a muscle mechanics-based laryngeal posturing model, a flow-structure-acoustics interaction voice production model, a real-coded genetic algorithm, and virtual implant insertion, the framework acquires the implant configuration that achieves the optimal acoustic objectives. The framework is showcased by successfully optimizing an implant that restores acoustic features of a diseased voice resulted from unilateral vocal fold paralysis (UVFP) in producing a sustained vowel utterance. The sound intensity is improved from 62 dB (UVFP) to 81 dB (post-correction).

Contribution of laryngeal size to differences between male and female voice production

In this study we investigated the effect of sex- and age-related differences in vocal fold length, thickness, and depth on voice production in a three-dimensional vocal fold model. The results showed that the cause-effect relationships between vocal fold physiology and voice production previously identified in an adult male-like vocal fold geometry remained qualitatively the same in vocal folds with geometry representative of adult females and children. We further showed that the often-observed differences in voice production between adult males, adult females, and children can be explained by differences in length and thickness. The lower F0, higher flow rate, larger vocal fold vibration amplitude, and higher sound pressure level (SPL) in adult males as compared to adult females and children can be explained by differences in vocal fold length. In contrast, the thickness effect dominated and contributed to the larger closed quotient of vocal fold vibration, larger normalized maximum flow declination rate, and lower H1-H2 in adult males as compared to adult females and children. The effect of differences in vocal fold depth was generally small. When targeting a specific SPL, adult males experienced a lower peak vocal fold contact pressure during phonation than adult females and children.

Phonation Threshold Pressure Revisited: Effects of Intrinsic Laryngeal Muscle Activation

OBJECTIVES/HYPOTHESIS

Phonation threshold pressure (P_th ) is the minimum subglottic pressure required to reach phonation onset and is considered a marker for vocal efficiency and health. We investigated the effects of intrinsic laryngeal muscle (ILM) activation on P_th .

STUDY DESIGN

In vivo animal study.

METHODS

In an in vivo canine phonation model, laryngeal adductor muscles were activated together by stimulation of the recurrent laryngeal nerves (RLNs) and individually via stimulation of respective terminal nerve branches. Cricothyroid (CT) muscles were activated via stimulation of the superior laryngeal nerves. ILMs were activated in a graded manner at various combinations as transglottal airflow was gradually increased. Aerodynamic and glottal posture parameters were measured at phonation onset.

RESULTS

Graded RLN stimulation decreased glottal distance and increased P_th . Thyroarytenoid (TA) muscle activation alone increased P_th . Lateral cricoarytenoid (LCA) muscle activation alone had minimal effects. However, graded TA activation as a function of LCA activation level revealed a synergistic relationship between the two muscles in increasing P_th . Effects of CT activation were dependent on adductor stimulation level: CT activation increased P_th at low RLN stimulation levels and decreased P_th at high RLN levels.

CONCLUSIONS

The effects of ILM activation on P_th were consistent with their expected effects on vocal fold stiffness and tension. TA was the primary adductor controlling P_th . While LCA alone had minimal effects on P_th , it enhanced the role of TA in controlling P_th . TA and CT have antagonistic roles in controlling P_th . These relationships should be considered in clinical efforts to improve ease of phonation and vocal efficiency.

LEVEL OF EVIDENCE

N/A, basic science Laryngoscope, 2021.

Patient-Related Factors of Medialization Laryngoplasty with Autologous Thyroid Cartilage

(1) Background: Medialization laryngoplasty with autologous thyroid cartilage (MLATC) is a surgical treatment for glottal closure insufficiency (GCI) resulted from unilateral vocal fold paralysis/paresis (UVFP) and vocal fold atrophy. We aimed to survey the influence of patient-related factors on the outcomes after MLATC. (2) Methods: The study enrolled 35 patients with GCI who underwent MLATC. Patient voice data were recorded before and after MLATC by using multiple acoustic parameters and subjective assessment in a computerized speech laboratory. GCI patients were characterized into subgroups based on three factors: age, ≥60 vs. <60 years; sex, men vs. women; and BMI, ≥24 vs. <24. (3) Results: When the subgroups were compared, men did not have better results after surgery than women. Patients ages < 60 years did not exhibit any significantly different outcome compared with those aged ≥ 60 years. Patients with BMI ≥ 24 did not have any significantly different outcome compared with those with BMI < 24. The subgroups of age, sex, and BMI had no significant difference in cumulative voice recovery and summation of GRBAS (G = grade, R = roughness, B = breathiness, A = asthenia, and S = strain). (4) Conclusions: MLATC is a good alternative surgery with long-term improvement in GCI patients. There is no evidence that age, sex, or BMI affect the functional outcome.