Combination thyroplasty and the "twisted larynx:" combined type IV and type I thyroplasty for superior laryngeal nerve weakness

Ansa Cervicalis External Branch Anastomosis to Restore High Tone Voice in Thyroid Surgery

OBJECTIVES

Injury to the external branch of the superior laryngeal nerve (EBSLN) causes low-pitch voice and voice fatigue, particularly in female subjects, and available treatments are limited. Here, we assess a novel surgical procedure to restore a high-tone voice: ansa cervicalis to EBSLN anastomosis (A-E anastomosis).

METHODS

Between November 2012 and April 2022, 13 patients (12 female) underwent unilateral EBSLN resection and A-E anastomosis, while 20 (16 female) underwent EBSLN resection during thyroid surgery. Patients (4494 women and 1025 men) with normal laryngoscopy scheduled for thyroid surgery served as normal controls. Phonatory function was examined using a Phonation Analyzer PA-1000 preoperatively and intermittently postoperatively.

RESULTS

In patients who underwent A-E anastomosis, high-tone voice pitch decreased significantly postoperatively (673.9-471.5 Hz, p = 0.047), with restoration achieved within 5 months. The mean voice pitch in female patients who underwent A-E anastomosis, EBSLN resection, and controls were 580.4, 522.8, and 682.0 Hz, respectively, indicating a significant decrease in EBSLN resection patients than controls (p = 0.002). The (mean - 1SD) of high-tone voice pitch in female controls was 497 Hz; exceeding this may indicate recovery to a high-tone voice. Overall, 73% (8/11) of A-E anastomosis patients exceeded this value, which was marginally larger than the 43% (6/14) who underwent EBSLN resection. Data on male subjects are limited. There were no cases of adverse functional or cosmetic events.

CONCLUSIONS

A-E anastomosis, a novel simple procedure, restored high-tone voice to some extent without any adverse events and thus warrants further investigation.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:3868-3873, 2024.

An Integrated Experimental-Computational Study of Vocal Fold Vibration in Type I Thyroplasty

Subject-specific computational modeling of vocal fold (VF) vibration was integrated with an ex vivo animal experiment of type 1 thyroplasty to study the effect of the implant on the vocal fold vibration. In the experiment, a rabbit larynx was used to simulate type 1 thyroplasty, where one side of the vocal fold was medialized with a trans-muscular suture while the other side was medialized with a silastic implant. Vocal fold vibration was then achieved by flowing air through the larynx and was filmed with a high-speed camera. The three-dimensional computational model was built upon the pre-operative scan of the laryngeal anatomy. This subject-specific model was used to simulate the vocal fold medialization and then the fluid-structure interaction (FSI) of the vocal fold. Model validation was done by comparing the vocal fold displacement with postoperative scan (for medialization), and by comparing the vibratory characteristics with the high-speed images (for vibration). These comparisons showed the computational model successfully captured the effect of the implant and thus has the potential for presurgical planning.

Subject-Specific Modeling of Implant Placement for Type I Thyroplasty Surgery

Type I thyroplasty is widely used to improve voice production in patients affected by unilateral vocal fold paralysis. Almost two-thirds of laryngologists report using Silastic® implants to medialize the vocal fold, with implant size, shape, and location determined experientially. However, post-surgical complications arising from this procedure (extrusion, migration, resizing) necessitate revision in 4.5-16% of patients. To improve initial surgical outcomes, we have developed a subject-specific modeling tool, PhonoSim, which uses model reconstruction from MRI scans to predict the optimal implantation location. Eleven vocal fold sample sides from eight larynges of New Zealand white rabbits were randomized to two groups: PhonoSim informed (n = 6), and control (no model guidance, n = 5). Larynges were scanned ex vivo in the abducted configuration using a vertical-bore 11.7 T microimaging system, and images were used for subject-specific modeling. The PhonoSim tool simulated vocal fold adduction for multiple implant location placements to evaluate vocal fold adduction at the medial surface. The best implant placement coordinates were output for the 6 samples in the PhonoSim group. Control placements were determined by the same surgeon based on anatomical landmarks. Post-surgical MRI scans were performed for all samples to evaluate medialization in implanted vocal folds. Results show that PhonoSim-guided implantation achieved higher vocal fold medialization relative to controls (28 to 55% vs. - 29 to 39% respectively, in the glottal area reduction), suggesting that this tool has the potential to improve outcomes and revision rates for type I thyroplasty.

Improving classification of the external branch of the superior laryngeal nerve with neural monitoring: a research appraisal and narrative review

Objective

To review the published literature on external branch of superior laryngeal nerve (EBSLN) neural monitoring and propose a new EBSLN classification system using intraoperative neural monitoring (IONM).

Background

The injury rate of the external branch of the superior laryngeal nerve (EBSLN) in thyroid surgery is 0-58%. Symptoms of EBSLN injury are not consistent, and patients often complain of modification of the voice timbre with the preservation of vocal cord function. Standards for the diagnosis of EBSLN injury are lacking.

Methods

The PubMed database was searched using the terms 'External branch of the superior laryngeal nerve' and 'Intraoperative neuromonitoring' from 2010 through March 2020.

Conclusions

This paper reviewed the anatomy of the EBSLN, the diagnosis and treatment of injury, and the application of IONM in the EBSLN. The traditional EBSLN classification method was analyzed and compared with our new classification method. The diagnosis of EBSLN injury is a problem that still needs to be resolved. For anatomic classifications of the EBSLN, we found that the conventional classification systems may not accurately reflect the real status of the EBSLN and the surgical risks that may occur intraoperatively. Using IONM, we developed an EBSLN classification method that was consistent with conventional diagnosis and treatments and can be widely and easily utilized during surgery.

Numerical and experimental investigations on vocal fold approximation in healthy and simulated unilateral vocal fold paralysis

We have developed a novel surgical/computational model for the investigation of unilateral vocal fold paralysis (UVFP) which will be used to inform future in silico approaches to improve surgical outcomes in type I thyroplasty. Healthy phonation (HP) was achieved using cricothyroid suture approximation on both sides of the larynx to generate symmetrical vocal fold closure. Following high-speed videoendoscopy (HSV) capture, sutures on the right side of the larynx were removed, partially releasing tension unilaterally and generating asymmetric vocal fold closure characteristic of UVFP (sUVFP condition). HSV revealed symmetric vibration in HP, while in sUVFP the sutured side demonstrated a higher frequency (10 - 11%). For the computational model, ex vivo magnetic resonance imaging (MRI) scans were captured at three configurations: non-approximated (NA), HP, and sUVFP. A finite-element method (FEM) model was built, in which cartilage displacements from the MRI images were used to prescribe the adduction and the vocal fold deformation was simulated before the eigenmode calculation. The results showed that the frequency comparison between the two sides were consistent with observations from HSV. This alignment between the surgical and computational models supports the future application of these methods for the investigation of treatment for UVFP.

Injury of the external branch of the superior laryngeal nerve in thyroid surgery

The external branch of the superior laryngeal nerve (EBSLN) innervates the cricothyroid muscle (CTM) to promote lengthening and thinning of the vocal fold, thus increasing voice pitch. The close relation with the superior thyroid vessels (STV) puts the EBSLN in risk every time the superior pole of the thyroid is dissected. It travels downward to innervate the CTM, lateral to the thyroid cartilage and to the inferior pharyngeal constrictor muscle (IPCM), being eventually covered by this muscle fibers as it approaches its entry point. During its descending course, the EBSLN curves and crosses the STV posteriorly. The lower this crossing occurs in the neck, the higher the risk of surgical damage to the nerve by transection, traction, entrapment, thermal damage or disrupted blood supply. The chances of surgical trauma are also increased by size and weight of the specimen, shorter neck length and non-white ethnicity. Voice changes following thyroid surgery are common and multifactorial. The actual rate of vocal impairment due to EBSLN injury is unclear, since changes to the everyday speaking voice can be minimal and laryngeal findings are usually subtle and controversial. CTM electroneuromyography (EMG) is the most accurate tool to diagnose abnormal EBSLN conductivity, but it is technically difficult and barely applicable in routine practice. Recommended approaches to prevent injury include: (I) individual distal ligature of the STV by the thyroid capsule; (II) visual identification of the nerve and its trajectory and (III) electrostimulation with either observation of CTM twitch or intraoperative nerve monitoring (IONM) via dedicated endotracheal tube electrodes. There is accumulating evidence that a combination of visual and standardized electrophysiological EBSLN identification with meticulous division of the STV improves preservation rates. IONM bears the additional benefits of prognostication, quantification and documentation of neural function once it allows intraoperative laryngeal EMG.

Neuromuscular compensation mechanisms in vocal fold paralysis and paresis

OBJECTIVES/HYPOTHESIS

Vocal fold paresis and paralysis are common conditions. Treatment options include augmentation laryngoplasty and voice therapy. The optimal management for this condition is unclear. The objective of this study was to assess possible neuromuscular compensation mechanisms that could potentially be used in the treatment of vocal fold paresis and paralysis.

STUDY DESIGN

In vivo canine model.

METHODS

In an in vivo canine model, we examined three conditions: 1) unilateral right recurrent laryngeal nerve (RLN) paresis and paralysis, 2) unilateral superior laryngeal nerve (SLN) paralysis, and 3) unilateral vagal nerve paresis and paralysis. Phonatory acoustics and aerodynamics were measured in each of these conditions. Effective compensation was defined as improved acoustic and aerodynamic profile.

RESULTS

The most effective compensation for all conditions was increasing RLN activation and decreasing glottal gap. Increasing RLN activation increased the percentage of possible phonatory conditions that achieved phonation onset. SLN activation generally led to decreased number of total phonation onset conditions within each category. Differential effects of SLN (cricothyroid [CT] muscle) activation were seen. Ipsilateral SLN activation could compensate for RLN paralysis; normal CT compensated well in unilateral SLN paralysis; and in vagal paresis/paralysis, contralateral SLN and RLN displayed antagonistic relationships.

CONCLUSIONS

Methods to improve glottal closure should be the primary treatment for large glottal gaps. Neuromuscular compensation is possible for paresis. This study provides insights into possible compensatory mechanisms in vocal fold paresis and paralysis.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:1633-1638, 2017.

Vibratory pattern of vocal folds under tension asymmetry

Objective

The aim of this study was to describe and analyze the vibratory pattern of vocal folds in an asymmetric situation.

Study Design and Setting

Cricothyroid muscle unilateral action was simulated on excised larynges on an experimental bench. Increasing airflow rates were applied to achieve vocal fold vibration. Electroglottography and an optoreflectometer device allowed analysis of separate and simultaneous vocal fold vibration. Spectra of the signals were obtained for each level of airflow variation.

Results

All experiments showed periodic vibration. A phase shift was noted between the two vocal folds. Subharmonics and biphonation were identified in all the experiments.

Conclusion

Lax vocal folds were more susceptible to spectral changes with increasing airflow.

Significance

Knowledge of the consequences of mass, tension, and position asymmetries of the vocal folds is crucial for diagnosis making and defining therapeutic strategies in dysphonic patients. This study may contribute to the understanding of physiology of vocal fold interaction and its compensatory mechanisms.

Superior laryngeal nerve injury: effects, clinical findings, prognosis, and management options

PURPOSE OF REVIEW

The superior laryngeal nerve (SLN) provides motor innervation to the cricothyroid muscle. However, the functions of this muscle and the anatomic variations of the nerve that supplies it are not fully understood. SLN paresis and paralysis (SLNp) is difficult to diagnose because of a lack of consistent laryngeal findings, and its effects on the voice likely go beyond simple pitch elevation control.

RECENT FINDINGS

Although SLNp has traditionally been thought to lead to voice pitch limitation, recent research findings reveal multiple roles for this nerve in voice and speech. Cricothyroid muscles are the primary controls of fundamental frequency of voice. SLNp can lead to significant contraction of pitch range, vocal fold vibratory phase asymmetry, and acoustic aperiodicity, thus leading to an overall poor vocal quality. In addition, cricothyroid muscles may also play a role in pitch lowering and shifting from voiced to unvoiced sounds during speech.

SUMMARY

Subtle signs, symptoms, and diagnostic findings associated with SLNp make this disorder difficult to characterize clinically. Lack of treatment methodologies to restore the dynamic action of the cricothyroid muscles poses difficulties in treating patients with this condition. A more thorough understanding of the effects of SLNp will improve diagnosis and treatment.

Defining phonosurgery: a proposal for classification and nomenclature by the Phonosurgery Committee of the European Laryngological Society (ELS)

The term phonosurgery (PS) refers to any operation designed primarily for the improvement or restoration of voice. It is defined by the intended operative goal, which pertains to quality of life rather than its preservation, and informed consent needs to account for this emphasis. Since the aim is improvement or maintenance of vocal function, it is essential to document voice accurately pre-operatively. As important as the surgery itself is a team approach to perioperative care and rehabilitation. Although not a new concept, the PS portfolio of operations continues to grow rapidly, making this one of the most dynamic field in Laryngology. However, this has also led to confusion regarding terminology and classification, with the result that it is presently difficult to compare results between institutions. The aim of this paper is to establish a practical classification system for PS and to thereby establish a common language for reporting results. We propose four groups of operation: vocal fold surgery (VFS), laryngeal framework surgery (LFS), neuromuscular surgery (NHS) and reconstructive surgery (RCS) (for either partial or total laryngeal replacement).

[Therapy for unilateral vocal fold palsy]

The main symptom of unilateral vocal fold palsy is hoarseness, which can cause considerable disturbance to the patient depending on its extent and the patient's individual situation. Therapy aims at the restitution of a tuneful and resilient voice, which can be achieved by surgical or conservative means, improving the glottal closure and synchronizing the vocal fold vibrations during phonation. Vocal therapy is a common conservative method that may be supported by psychotherapeutic or physical procedures. In surgical therapy, there is a distinction between techniques of endoscopic augmentation by injecting different materials into the vocal folds and transcutaneous laryngeal framework surgery, i.e., transferring the paralyzed vocal fold to the glottal midline. Particularly apt for injection are biocompatible materials amount and position whose can easily be controlled. However, the inevitable resorption of many materials causes deterioration in voice quality. Furthermore, the change of vocal fold morphology obstructs regular phonatory vibration. On the other hand, medialization thyroplasty leads to permanent voice amelioration without a substantial complication rate when performed by experienced surgeons.

The superior laryngeal nerve: function and dysfunction

Despite long-standing clinical interest in SLN dysfunction, most aspects of this entity continue to require clarification. The replacement of the laryngeal mirror by flexible fiberoptic and rigid rod-lens laryngoscopy (including stroboscopy) and the resulting improvement in laryngeal visualization and documentation of examination has not resulted in a better definition of characteristic signs. Symptoms are often vague, and most are shared with other voice disorders. Under the circumstances, there is good reason to suppose that SLN dysfunction yields a clinical picture at least as heterogeneous as recurrent laryngeal nerve injury and a good deal more subtle. Faced with significant inconsistencies in clinical presentation, the clinician is hard-pressed to draw conclusions regarding prevalence, patterns of dysfunction, natural history, treatment, and even about its overall significance. EMG. used judiciously and complemented by frequency range testing, seems to hold more promise as a means of reliable diagnosis than laryngoscopic examination and may serve to resolve some of the confusion surrounding SLN dysfunction. It is equally important that the otolaryngologist guard against falling into the easy habit of attributing vocal disturbance that cannot be otherwise explained to SLN dysfunction in the absence of EMG evidence. If ambiguities surrounding SLN paralysis and paresis are to be clarified, diagnostic rigor is essential.

Evidence-based treatment of paralytic dysphonia: making sense of outcomes and efficacy data

The criteria used to determine the success or failure of a given treatment for vocal fold paralysis are fundamental components of routine clinical practice and treatment outcomes research for the surgeon and voice therapist. The purpose of this article is to offer a guide to the critical interpretation of available measures of out-come and efficacy for this patient population. Such data form the basis for the practice of evidence-based medicine and voice therapy,essential if the standard of care is to evolve to the benefit of the patient. A better understanding of the potentials and limitations of each measure is important for treatment planning and patient counseling and, ultimately, for the conception of future well-designed clinical research. The complex issues regarding outcomes measurement are addressed here within the context of current treatment literature on vocal fold paralysis. Particular emphasis is placed on realistic data gathering within clinical practice.

Thyroplasty revisions: frequency and predictive factors

Thyroplasty is the most commonly performed type of laryngeal framework surgery, and the surgical indications are gradually being expanded. Although many reports have described thyroplasty results and rates of success, no study has attempted to determine predictors of the need for revisions or other secondary surgical procedures.

METHODS

Retrospective review of 118 primary thyroplasty procedures performed on 96 patients. Secondary surgical procedures were divided into planned second-stage procedures (all fat implantation due to scarring), touchup procedures (primarily fat or collagen injections to close localized glottic gaps), and thyroplasty revisions (for implant extrusion or slippage). Statistical analysis was performed via the chi-squared technique with p < 0.05 considered significant.

RESULTS

96 patients underwent thyroplasty, 58 for vocal fold paresis or paralysis and 38 for other indications. Thirty-two (33%) patients underwent secondary surgical procedures, including 4 planned second stage procedures, and 6 patients with progression of their underlying disease. Thirty-two secondary procedures were performed in the other 22 patients. Professional singers were found to be more likely to require touchup or planned second-stage procedures (p = 0.029). Patients with abnormal preoperative noise-toharmonic ratios were more likely to undergo secondary surgeries (p = 0.039). Maximum phonation time was not associated with need for secondary surgery. Implant material did not influence revision rates.

CONCLUSIONS

Professional singers and those patients with severe voice disorders (as measured by more abnormal noise-to-harmonic ratios) are more likely to undergo secondary surgical procedures. The choice of implant material does not affect need for secondary surgical procedures.

Revision thyroplasty

To document surgical techniques for performing a revision thyroplasty operation and to describe the subjective and objective results of these operations. I undertook a retrospective review of all patients who have undergone thyroplasty in my practice. I identified patients who required revision of a previous thyroplasty and evaluated preoperative and postoperative video and audio analyses of the voice. I identified the surgical steps necessary for successful completion of a revision operation and noted any special findings made at surgery. Charts were reviewed and tabulated for reasons for failure of the first operation, efficacy of the second surgical approach, specific anatomic findings made at revision surgery, and types of surgery available for revision. Of 625 total thyroplasties in 331 patients, revision operations accounted for 61 operations in 48 patients. All thyroplasty operations were found to be revisable or reversible. Objective voice analysis for 35 operations in 32 patients revealed a statistically significant improvement in shimmer in women, and in harmonics-to-noise ratio in all patients. Subjective voice improvement occurred in 80% of patients after revision surgery. I conclude that revision thyroplasty is possible with all thyroplasty types, giving significant improvement in both shimmer (women) and harmonics-to-noise ratio (all patients). Although most voices are still abnormal on postoperative objective voice analysis, 80% of patients are subjectively improved.