Visual observations of glottal configuration and vocal outcomes in arytenoid adduction

Fluid-structure-acoustic interactions in an ex vivo porcine phonation model

In the clinic, many diagnostic and therapeutic procedures focus on the oscillation patterns of the vocal folds (VF). Dynamic characteristics of the VFs, such as symmetry, periodicity, and full glottal closure, are considered essential features for healthy phonation. However, the relevance of these individual factors in the complex interaction between the airflow, laryngeal structures, and the resulting acoustics has not yet been quantified. Sustained phonation was induced in nine excised porcine larynges without vocal tract (supraglottal structures had been removed above the ventricular folds). The multimodal setup was designed to simultaneously control and monitor key aspects of phonation in the three essential parts of the larynx. More specifically, measurements will comprise (1) the subglottal pressure signal, (2) high-speed recordings in the glottal plane, and (3) the acoustic signal in the supraglottal region. The automated setup regulates glottal airflow, asymmetric arytenoid adduction, and the pre-phonatory glottal gap. Statistical analysis revealed a beneficial influence of VF periodicity and glottal closure on the signal quality of the subglottal pressure and the supraglottal acoustics, whereas VF symmetry only had a negligible influence. Strong correlations were found between the subglottal and supraglottal signal quality, with significant improvement of the acoustic quality for high levels of periodicity and glottal closure.

Effects of Arytenoid Adduction Suture Position on Voice Production and Quality

OBJECTIVES/HYPOTHESIS

Arytenoid adduction (AA) is performed to treat unilateral vocal fold paralysis with a large posterior glottal gap. However, the voice effects of AA suture position remain unclear. This study aimed to evaluate voice production and quality as a function of AA suture position on the thyroid ala in a neuromuscularly intact in vivo larynx.

STUDY DESIGN

Animal model.

METHODS

Unilateral recurrent laryngeal nerve and vagal paralysis were modeled in two canines. AA suture position was varied across five equidistant positions on the anterior inferior thyroid ala, from a paramedian position anteriorly to the oblique line posteriorly. Phonation was performed over 8 × 8 graded level combinations of recurrent and superior laryngeal nerve stimulation per suture position. The primary outcome was percent successful phonatory conditions. Secondary outcomes included fundamental frequency (F0), phonation onset pressure (PTP), cepstral peak prominence (CPP), and laryngeal posture.

RESULTS

Anterior suture positions resulted in a greater percentage of successful phonatory conditions compared to posterior sutures. Suture position 2, located at the anterior inferior thyroid ala, resulted in the highest percentage of successful phonatory conditions, lowest PTP, and lower muscle activation levels to achieve higher CPP. Posterior sutures resulted in wider glottal gap and more effective F0 and vocal fold strain increase with cricothyroid muscle contraction, but with fewer successful phonatory conditions and higher PTP. Trends were consistent across both paralysis types.

CONCLUSIONS

AA suture placed in the anterior inferior thyroid ala resulted in the best acoustic, aerodynamic, and voice quality outcomes. This study provides scientific evidence for maintaining current clinical practice.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:846-852, 2021.

Breathiness and Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) in Patients Undergoing Medialization Laryngoplasty With or Without Arytenoid Adduction

OBJECTIVES

We hypothesized that, in patients with unilateral vocal fold paralysis (UVFP), the auditory-perception of breathiness measured with Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) would be higher preoperatively in patients who undergo medialization laryngoplasty (ML) with arytenoid adduction (AA) compared to ML alone. We further hypothesized that increased breathiness would correlate with increased glottal area at maximum glottal closure.

STUDY DESIGN

Retrospective chart review.

METHODS

CAPE-V recordings were rated by expert judges in 105 subjects with UVFP (47 ML+AA and 58 ML). Component scores of the CAPE-V prior to laryngeal framework surgery and those at 3 and/or 12 months postoperatively were compared. Assessment of glottal area width during maximum glottal closure was attempted.

RESULTS

Breathiness scores prior to laryngeal framework surgery were significantly greater in UVFP patients having ML+AA compared to ML only (P < 0.001). Roughness was greater for ML only (P = 0.003). At 3 months, adjusted for age and previous injection laryngoplasty, the ML+AA group showed greater improvement for breathiness (P <0.001), loudness (P < 0.001), strain (P = 0.037), and pitch (P = 0.039), while the ML only group showed greater improvement in roughness (P = 0.009). Results were similar at 12 months. Only 26% of glottal area widths were ratable using methods previously described; therefore, no further analysis was attempted.

CONCLUSIONS

In patients with UVFP baseline perception of breathiness is greater in those clinically selected for ML+AA compared to ML only. Glottal area measurements were not representative of the UVFP cohort and more stringent criteria are needed for valid and reliable glottal area assessment when using clinical flexible stroboscopic exams. Findings support the idea that surgeons may be making decisions about AA based, to at least some degree, on auditory perceptual evaluation of voice.

Influence of glottal closure on the phonatory process in ex vivo porcine larynges

Many cases of disturbed voice signals can be attributed to incomplete glottal closure, vocal fold oscillation asymmetries, and aperiodicity. Often these phenomena occur simultaneously and interact with each other, making a systematic, isolated investigation challenging. Therefore, ex vivo porcine experiments were performed which enable direct control of glottal configurations. Different pre-phonatory glottal gap sizes, adduction levels, and flow rates were adjusted. The resulting glottal closure types were identified in a post-processing step. Finally, the acoustic quality, aerodynamic parameters, and the characteristics of vocal fold oscillation were analyzed in reference to the glottal closure types. Results show that complete glottal closure stabilizes the phonation process indicated through a reduced left-right phase asymmetry, increased amplitude and time periodicity, and an increase in the acoustic quality. Although asymmetry and periodicity parameter variation covers only a small range of absolute values, these small variations have a remarkable influence on the acoustic quality. Due to the fact that these parameters cannot be influenced directly, the authors suggest that the (surgical) reduction of the glottal gap seems to be a promising method to stabilize the phonatory process, which has to be confirmed in future studies.

Functional Significance of Arytenoid Adduction with the Suture Attaching to Cricoid Cartilage versus to Thyroid Cartilage for Unilateral Paralytic Dysphonia

OBJECTIVE

In the treatment of unilateral paralytic dysphonia, traditional arytenoid adduction is designed to place suture through the muscular process of the arytenoid attaching anteriorly to the thyroid ala. In contrast with the suture direction of this technique, a new paramedian approach to arytenoid adduction anchors anteroinferiorly to the cricoid cartilage, mimicking the force action of the lateral cricoarytenoid muscle (the major adductor of the larynx). This study investigated the influence of these changes in suture direction on the vocal fold level as well as the vocal outcomes in these two techniques of arytenoid adduction.

STUDY DESIGN

A prospective clinical series.

METHODS

Thirty patients with unilateral paralytic dysphonia underwent medialization laryngoplasty with arytenoid adduction and strap muscle transposition. Under local anesthesia, the thyroid lamina on the involved side was paramedially separated. The inner perichondrium was carefully elevated away from the overlying thyroid cartilage, carrying the dissection posteriorly to the level of the superior and inferior cornua. The lamina was retracted laterally, the inner perichondrium was opened near the midpoint, and the lateral cricoarytenoid muscle identified. Tracing the muscle fibers posterosuperiorly, the muscular process of the arytenoid was identified. A 2-0 Prolene suture was placed through the muscular process and temporarily tied to the anterolateral aspect of the thyroid ala (AA-thyroid suture). Intraoperative acoustic and perceptual assessments were performed. After releasing the tie, the suture was anchored to the cricoid cartilage at the origin of the lateral cricoarytenoid muscle (AA-cricoid suture). Voice assessments were repeated, and the outcomes of the two tests were compared. The choice of the type of arytenoid adduction suture was made intraoperatively according to which condition provided better vocal performance. After securing the suture, a bipedicled strap muscle flap was transposed into the space between the lamina and inner perichondrium and the thyroid cartilages sutured back into place.

RESULTS

The intraoperative acoustic and perceptual assessments revealed the vocal performance was significantly better with AA-cricoid suture than the AA-thyroid suture in this series. No major complications occurred in the study.

CONCLUSION

This study suggests that arytenoid adduction with suture attachment along the longitudinal axis of the lateral cricoarytenoid muscle to the cricoid cartilage is more physiologic and effective than that attaching the suture to the thyroid ala. A paramedian approach to arytenoid adduction with or without strap muscle transposition is a safe and effective method for treatment of unilateral paralytic dysphonia.