Nomenclature proposal to describe vocal fold motion impairment

The terms used to describe vocal fold motion impairment are confusing and not standardized. This results in a failure to communicate accurately and to major limitations of interpreting research studies involving vocal fold impairment. We propose standard nomenclature for reporting vocal fold impairment. Overarching terms of vocal fold immobility and hypomobility are rigorously defined. This includes assessment techniques and inclusion and exclusion criteria for determining vocal fold immobility and hypomobility. In addition, criteria for use of the following terms have been outlined in detail: vocal fold paralysis, vocal fold paresis, vocal fold immobility/hypomobility associated with mechanical impairment of the crico-arytenoid joint and vocal fold immobility/hypomobility related to laryngeal malignant disease. This represents the first rigorously defined vocal fold motion impairment nomenclature system. This provides detailed definitions to the terms vocal fold paralysis and vocal fold paresis

Successful retrieval of a dislodged tracheoesophageal prosthesis distal to a neopharyngeal stricture

Objective: Tracheoesophageal prostheses (TEPs) can easily become airway or esophageal foreign bodies. We present a challenging case of TEP dislodgement in order to stimulate discussion of management and technical removal of these uniquely shaped foreign bodies. Methods: Case report and literature review. Results: A 74-year-old female presented with TEP displacement after laryngectomy tube change. Chest imaging revealed the prosthesis in the mid-esophagus, with failure of the prosthesis to pass after 24 hours. During flexible transoral esophagoscopy at the bedside, a 10-mm diameter stricture was encountered in the neopharynx just proximal to the tracheoesophageal puncture. Initial attempts to retrieve the TEP using a 13 mm short throw snare and flexible jumbo alligator forceps were unsuccessful. As an alternative strategy, the prosthesis lumen was cannulated with the forceps (jaws closed), then advanced past the distal flange of the TEP. The jaws were opened and pulled back against the distal flange, successfully dislodging the prosthesis proximally, allowing retrieval past the neopharyngeal stricture. Conclusion: TEPs are foreign bodies with slippery flanges that may not lend themselves to conventional small grasping instruments. Given its unique shape, catheterization of the TEP lumen can be taken advantage of to gain purchase for retrieval

Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species.

Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations

Rheometric properties of canine vocal fold tissues: Variation with anatomic location

[[abstract]]Objective To evaluate the in vitro rheometric properties of the canine vocal fold lamina propria and muscle at phonatory frequencies, and their changes with anatomic location. Methods Six canine larynges were harvested immediately postmortem. Viscoelastic shear properties of anterior, middle, and posterior portions of the vocal fold cover (lamina propria) as well as those of the medial thyroarytenoid (TA) muscle (vocalis muscle) were quantified by a linear, controlled-strain simple-shear rheometer. Measurements of elastic shear modulus (G′) and dynamic viscosity (η′) of the specimens were conducted with small-amplitude sinusoidal shear deformation over a frequency range of 1–250 Hz. Results All specimens showed similar frequency dependence of the viscoelastic functions, with G′ gradually increasing with frequency and η′ decreasing with frequency monotonically. G′ and η′ of the canine vocalis muscle were significantly higher than those of the canine vocal fold cover, and η′ of the canine vocal fold cover was significantly higher than that of the human vocal fold cover. There were no significant differences in G′ and in η′ between different portions of the canine vocal fold cover. Conclusion These preliminary data based on the canine model suggested that the vocalis muscle, while in a relaxed state in vitro, is significantly stiffer and more viscous than the vocal fold cover during vibration at phonatory frequencies. For large-amplitude vocal fold vibration involving the medial portion of the TA muscle, such distinct differences in viscoelastic properties of different layers of the vocal fold should be taken into account in multi-layered biomechanical models of phonation

Viscoelastic properties of phonosurgical biomaterials at phonatory frequencies

[[abstract]]Objectives/Hypothesis: The purpose of this study was to examine the functional biomechanical properties of several injectable biomaterials currently or potentially used for vocal fold augmentation. Study Design: Rheometric investigation of phonosurgical materials in vitro. Methods: Linear viscoelastic shear properties of 3% bovine collagen (atelocollagen), micronized AlloDerm (Cymetra; LifeCell Corp., Branchburg, NJ), calcium hydroxylapatite (CaHA) (Radiesse; BioForm Medical, San Mateo, CA), and 2.4% cross‐linked hyaluronic acid (HA) gel (Juvéderm; Allergan, Inc., Irvine, CA) were quantified as functions of frequency covering the phonatory range, and compared to those of the human vocal fold cover. Measurements of elastic shear modulus (G′) and dynamic viscosity (η′) were made at up to 250 Hz with a controlled‐strain simple‐shear rheometer. Linear least‐squares regression was conducted to curve‐fit log G′ and log η′ versus log frequency, and statistical analysis was performed with one‐way analysis of variance. Results: Radiesse and Cymetra were found to be the stiffest and the most viscous materials, followed by Juvéderm and atelocollagen. There were significant differences in the magnitudes of G′ and η′ among the phonosurgical materials and the normal human vocal fold cover (p < .001), whereas there was no significant difference in the frequency dependence of G′ and η′ among the materials. Post hoc Tukey tests revealed significant differences (p < .05) in pairwise comparisons of the magnitudes of G′ and η′ among all materials and the vocal fold cover. Conclusions: These findings suggested that although these biomaterials may be injected lateral to the lamina propria for the treatment of glottic insufficiency, none of them are rheologically optimal for the functional reconstruction of the vocal fold lamina propria. Laryngoscope, 201

Raw data of body mass, vocal fold length (<i>L</i>₀), stress-strain relationship for vocal fold tissue, and average fundamental frequency range.

<p>Vocal fold lengths were measured in specimen available to us (unpublished data), except for the African elephant. The variable <i>ε</i> = (<i>L</i>-<i>L</i>₀) / <i>L</i>₀.</p

Relations between logarithmic fundamental frequency ratio (high/low) and the respective vocal fold length ratio (long/short) for vocal fold tissue characterized by different B-values (from Eq 3).

<p>A value of <i>L</i>₁ = 0.7<i>L</i>₀ was assumed.</p

Modulating phonation through alteration of vocal fold medial surface contour

[[abstract]]Objectives/Hypothesis: 1) To test whether alteration of the vocal fold medial surface contour can improve phonation and 2) to demonstrate that implant material properties affect vibration even when implantation is deep to the vocal fold lamina propria. Study Design: Induced phonation of excised human larynges. Methods: Thirteen larynges were harvested within 24 hours postmortem. Phonation threshold pressure (PTP) and flow (PTF) were measured before and after vocal fold injections using either calcium hydroxylapatite (CaHA) or hyaluronic acid (HA). Small‐volume injections (median, 0.0625 mL) were targeted to the inferomedial aspect of the thyroarytenoid muscle. Implant locations were assessed histologically. Results: The effect of implantation on PTP was material dependent. CaHA tended to increase PTP, whereas HA tended to decrease PTP (Wilcoxon test, P = .00013 for onset). In contrast, the effect of implantation on PTF was similar, with both materials tending to decrease PTF (P = .16 for onset). Histology confirmed implant presence in the inferior half of the vocal fold vertical thickness. Conclusions: Taken together, these data suggested the implants may have altered the vocal fold medial surface contour, potentially resulting in a less convergent or more rectangular glottal geometry as a means to improve phonation. An implant with a closer viscoelastic match to vocal fold cover is desirable for this purpose, as material properties can affect vibration even when the implant is not placed within the lamina propria. This result is consistent with theoretical predictions and implies greater need for surgical precision in implant placement and care in material selection

Contour plot of predicted fundamental frequency range (high/low, <i>f</i>_o2/<i>f</i>_o1 ratio) for morphological variables <i>B</i> and <i>L</i>₂/<i>L</i>₁.

<p>The range depends on two important factors: the rotational flexibility of the laryngeal framework, which facilitates <i>L</i>₂/<i>L</i>₁; and the <i>B</i> value that quantifies the tissue stress response to elongation. For a given B value, a larger fundamental frequency range can be achieved with greater rotational flexibility. For a given <i>L</i>₂/<i>L</i>₁ ratio, a larger frequency range can be achieved with a greater <i>B</i> value. Note that the changes in the <i>B</i> value are not large to achieve a larger frequency range for a given a given <i>L</i>₂/<i>L</i>₁ ratio.</p