------------------------------------------------------------------------------- TITLE: VOICE DISORDERS AND PHONOSURGERY 1995 SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: May 19, 1995 RESIDENT PHYSICIAN: Chris Thompson, M.D. FACULTY: Byron J. Bailey, M.D. DATABASE ADMINISTRATOR: Melinda McCracken, M.S. ------------------------------------------------------------------------------- "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." A. Introduction 1. Physiology of voice 2. Vocal assessment 3. Vocal pathology 4. Phonosurgery 5. New areas of research B. Mechanics of voice 1. Glottic cycle a. begins with the generation of pressure below a closed glottis b. the lower margin of the vocal folds opens, leaving an elliptical pocket of air c. the upper margin opens, followed by a rapid return to midline of the lower margin d. the upper margin closes and the cycle is repeated e. this phenomenon creates puffs of air, followed by rapid glottic closure which produces an acoustic vibration similar to that of the clap of a hand 2. Mucosal wave - because of the phase difference between the movement of the upper and lower vocal fold margins, a rippling, vertical displacement is produced in the mucosa covering the thyroarytenoid muscle(vocalis) 3. Vocal fold mechanics a. anatomy - the vocalis muscle is covered with three layers of lamina propria (deep, intermediate, superficial), and an outer epithelial covering b. functionally, the vocal fold has an outer sheath of mucosa and superficial lamina propria, and a body composed of the muscle and remaining two layers of lamina propria c. cover i. the gliding motion of the cover over the body allows for two discreet areas of vocal fold closure ii. the motion of the cover is responsible for the rippling vertical displacement known as the traveling wave d. body i. the body of the vocal fold determines its stiffness, and is therefore directly related to the velocity of the wave ii. this translates to frequency of vibration and thus the pitch of the voice iii. the stiffness of the body is controlled by the combination of the vocalis and cricothyroid muscles iv. contraction of the vocalis thickens and shortens the vocal fold causing pitch to decrease v. cricothyroid contraction stretches and thins the vocal fold resulting in an increase in pitch 4. The myoelastic-aerodynamic theory behind vocal fold vibration a. the most accepted theory calls on the combination of the myoelastic properties of the vocal folds and the drop in air pressure due to rapid air flow (Bernoulli's effect) b. these two forces bring the vocal folds back into approximation when their magnitude overcomes that of the subglottic pressure c. although the subglottic pressure never drops to zero, it does diminish as the glottic puff traverses past the vocal folds d. as this pressure drops, the vocal folds approximate until the subglottic pressure overcomes the inward forces C. Voice evaluation 1. Laryngoscopy via indirect or fiberoptic methods reveals information about vocal fold anatomy and mobility a. immediate diagnosis for mass lesions or asymmetric stiffness abnormalities (unilateral paralysis) b. subjective evaluation 2. Electromyography a. only objective measurement of laryngeal innervation in the presence of vocal fold paralysis b. invasive test that relies on accurate placement of electrodes into the laryngeal musculature c. provides prognostic information by displaying reinnervation or denervation type signals d. fibrillation potentials usually seen within three weeks of denervation e. reinnervation potentials seen between six and twelve months from injury 3. Electroglottography a. records vocal fold adduction by measuring the current from an electrode on one side of the larynx across the glottis and into the opposite electrode b. a closed glottis provides the least amount of resistance and is associated with the greatest amount of current flow c. when the vocal folds are abducted, the resistance is high and the current is low d. the output is a wave representing glottic resistance plotted against time; and since glottic resistance relates to the area between the folds, the output represents vocal fold position versus time e. mathematical derivation of this output produces a waveform displaying vocal fold velocity versus time f. alterations in the normal pattern can reflect mass lesions or asymmetric stiffness disorders g. electroglottographic records made from normal, breathy, and tense voices show velocity and position versus time i. the peak in the lower tracing represents the closed glottis ii. in the normal voice, the closed time is about 50% of the cycle iii. in the breathy voice, the closed time represents a significantly decreased portion of the cycle iv. in the tense voice, the closed time occupies a greater portion of the cycle h. the disadvantage of this technique is that the information is a product of both vocal folds and is therefore imprecise 4. Photoglottography a. similar to EGG in that the amount of light trans- illuminated through the glottis is measured and plotted against time b. complementary to EGG because the peaks of the cycle correspond to the abducted glottis and therefore measures vocal fold opening 5. Aerodynamic measurements a. subglottic pressure and translaryngeal airflow can be measured noninvasively with a facemask b. since pressure is equivalent to the product of flow and resistance, the resistance can be calculated c. glottic resistance is often altered in vocal fold stiffness pathology i. increased resistance usually indicates an increase in vocal fold stiffness ii. decreased resistance often accompanies the paralyzed larynx 6. Acoustic analysis a. analysis of vocal output can be separated into its frequency components using mathematical techniques such as the Fourier transformation b. the frequency can be plotted against time or amplitude c. one can represent the analysis of a normal voice by plotting frequency versus time above, and intensity versus time below; the fundamental frequency is labeled Fo and the first harmonic labeled 4Fo d. this plot can display the same data for a pathologic voice with obvious frequency and intensity fluctuation e. cycle-to-cycle frequency variation or jitter can be demonstrated on one plot while shimmer, or amplitude variation, is pictured on the second graph f. another area where pathology is demonstrated is in the relative level of noise; soft, breathy voices often have more associated noise and tend to have more energy in the fundamental frequency and less in the harmonics 7. Videostroboscopy a. utilizes flashes of light at a frequency determined by either the pitch of phonation or a frequency generator b. this creates the impression that the folds are vibrating in slow motion c. provides detailed information about vocal fold mobility, mass lesions, and the status of the mucosal wave D. Definition and history of phonosurgery 1. this is really a number of different procedures that can be categorized into the following subsets a. excision of mass lesions using microsurgical techniques b. injection of vocal fold for augmentation c. laryngeal reinnervation techniques d. laryngeal framework procedures e. reconstruction after tumor excision 2. relatively young field with the first medialization procedure coming in 1911 and our modern concept of laryngeal framework surgery arising only 20 years ago a. 1911 - Brunings introduces the injection of paraffin into the body of the vocal fold for medialization b. 1915 - Payr describes a technique which relies on a posterior, vertical incision through the thyroid cartilage to allow medialization with lateral pressure c. 1952 - Meurman uses anterior, vertical thyroid cartilage incision to allow the placement of autologous rib d. 1962 - Arnold describes Teflon injections for medialization e. 1975 - Isshiki introduces the concept of alloplastic materials to implant for medialization procedures E. Surgery for mucosal lesions 1. encompasses a variety of conditions including polyps, nodules, granulomas, malignancies, and premalignancies 2. produce hoarseness by interfering with glottic competency and attendant alteration in the mucosal wave 3. usually indicated only after the patient has had a prolonged attempt at stopping the inciting factor 4. best results usually with a cold knife although laser surgery is helpful in vascular lesions 5. laser energy is difficult to control and is often associated with heat transfer to surrounding tissues F. Vocal fold paralysis 1. etiologies of paralysis a. 34% idiopathic b. 25% malignancy c. 23% iatrogenic/trauma (nonthyroidectomy) d. 10% thyroidectomy e. 8% neurologic 2. natural history of the paralyzed fold a. dependant on the etiology, severity, and the effects of reinnervation and compensation b. transection of the nerve produces immediate flaccid paralysis followed by atrophy and fibrillation potentials c. if the cut ends are close, reinnervation usually occurs in 6 - 12 months and polyphasic potentials are then detectable d. synkinesis is the rule, as the appropriate fibers do not randomly match up with each other 3. examination of the paralyzed fold a. most laryngeal nerve injuries do not involve transection so some fibers are usually intact b. this, in combination with variable reinnervation, atrophy, and compensatory hypertrophy make the physical examination of the larynx imprecise c. the literature generalizes the location of a vocal fold with a recurrent laryngeal paralysis to be in the paramedian position d. superior laryngeal paralysis is described as resulting in the posterior glottis shifting towards the lesion with bowing and flaccidity in the affected fold 4. workup and conservative therapy a. define the etiology if possible with history, physical exam and appropriate studies b. of the previously described vocal evaluation studies, stroboscopy will consistently provide useful additional information c. assessment and therapy by a speech-language pathologist will be beneficial almost universally d. additionally, by timing the patient's ability to maintain a vocal tone or assessing how many inhalations he needs to count to ten will provide some simple, objective evaluation of the pathology 5. timing of surgery a. acute medialization is indicated at the time of skull- base surgery if resection of the vagus is carried out, and may prevent a tracheotomy b. if no etiology is identified it is advisable to wait a year before any medialization technique is performed c. for other, identifiable pathologies six to twelve months is often said to be reasonable d. reversible procedures such as Gelfoam medialization may be done more acutely G. Injection medialization 1. a variety of substances are now used including Teflon (polytef), autogenous fat, collagen, and Gelfoam 2. Teflon has been the primary method of treatment for the past thirty years, but is now relegated to those patients with terminal malignancies or who are poor surgical candidates 3. autogenous fat injection has been shown to produce good results with follow-up out to forty-two months 4. collagen was also found to be suitable for medialization and may be useful in vocal fold scarring to help restore vocal fold vibration 5. gelfoam provides a temporary material for medialization and can help predict surgical results, provide palliation, and aid biofeedback techniques 6. proper technique is essential in injection medialization, and poor results can usually be traced to errors here 7. one can find advocates of local anesthesia, or general anesthesia with and without an endotracheal tube for this procedure 8. once the larynx is reached, the needle is obliquely directed through the floor of Morgagni's ventricle three millimeters in depth 9. the injected material in instilled in one milliliter aliquots in the space between the vocalis muscle and thyroid cartilage 10. complications include overinjection, underinjection, improper placement, migration, and granuloma formation H. Laryngeal framework surgery 1. modern techniques are attributed to Isshiki and have been categorized into four types a. Type 1 pushes the paralytic vocal fold towards the midline b. Type 2 causes laterally directed displacement of the vocal folds c. Type 3 bilaterally shortens and decreases the tension on the vocal folds d. Type 4 increases the tension and elongates the folds 2. Type 1 thyroplasty a. performed under local anesthesia to allow vocal feedback during manipulation b. the thyroid cartilage is exposed through a small neck incision and the outer perichondrium is elevated c. depending on available instrumentation, a window is cut in the cartilage; one places a template (6x13mm) positioned five to eight mm posterior to the anterior commissure and four mm superior to the inferior border d. the inner perichondrium is usually left intact although some authors advocate incising it to accent medialization e. using a depth gauge, or the carved silastic block, the fold is medialized until the optimal vocal response is achieved f. the vocal fold lies adjacent to the lower aspect of the window which should be kept in mind while carving the silastic; applying pressure more superiorly will involve the false cord g. for best results it is important to minimize the time spent manipulating the endolarynx; edema develops quickly and will interfere with the quality of the voice h. the major limitation of this technique is medialization of the posterior glottis; the application of lateral pressure in this area will encounter the signet ring of the cricoid cartilage i. complications include silastic extrusion, persistent inflammation, and improper placement of the implant 3. Arytenoid adduction a. an adjunctive procedure for instances in which the type I thyroplasty fails to provide adequate medialization of the posterior glottis or when the vocal folds are at a different level b. often combined with type I when the injury is a high vagal lesion because the asymmetric cricothyroid contraction places the folds at different levels, along with creating a large posterior glottic gap c. technically difficult and requires the opening of the cricoarytenoid joint, making it irreversible d. the incision of the pharyngeal constrictor muscle is made at its attachment to the thyroid lamina e. one follows with disarticulation of the cricothyroid joint f. in order to gain access to the cricoarytenoid joint the posterior and lateral cricoarytenoid muscles are separated g. two 4-0 nylon sutures are passed around the muscular process of the arytenoid and the ends are passed through the thyroid cartilage at an angle that will provide adduction 4. Type III thyroplasty a. designed to shorten the vocal folds and decrease pitch b. indicated for gender transformation, mutational falsetto, and has been advocated for spasmodic dysphonia although in controlled studies it has not been shown to be effective c. approach is identical to that of the type I thyroplasty d. one continues by removing bilateral cartilaginous strips to reduce the antero-posterior dimension of the glottis e. as in type I, the patient is asked to vocalize, and modifications are carried out as needed 5. Type IV thyroplasty a. performed to lengthen the vocal folds and elevate pitch b. indicated pathology include vocal fold laxity from trauma, postoperative defects, and androphonia as well as gender transformation c. the technique of Isshiki involves the implantation of silastic strips to lengthen the antero-posterior dimension of the larynx d. the LeJeune procedure creates an inferiorly based cartilaginous flap with an intervening shim used to lengthen the vocal folds e. cricothyroid approximation also effectively lengthens the vocal folds 6. Reinnervation procedures a. described by Tucker in 1977 and modified by Crumley in 1988, these techniques allow a more physiologic approach to rehabilitation of the paralyzed vocal fold b. not useful in patients with aspiration because of limited medialization, this procedure can improve stabilization of the arytenoid cartilage, and present a more normal mass, tension, and position of the paralyzed vocal fold c. the procedure described by Tucker involves taking a segment of omohyoid muscle with its attached ansa hypoglossus nerve and placing it adjacent to the vocalis muscle via a window in the thyroid cartilage identical to that of a type I thyroplasty d. Crumley's modification involves attaching the proximal ansa cervicalis to the distal stump of the recurrent laryngeal nerve e. these reinnervation procedures are performed rarely and can be done in combination with other medialization procedures I. Future considerations 1. Laryngeal modeling - from canine larynges to mathematical modeling, the ultimate goal is a mechanical neolarynx 2. Implant materials a. autologous fat b. collagen - improvements in the mucosal wave in scarred vocal folds 3. Reinnervation techniques - ultimately selective reinnervation of adductors and abductors J. Summary 1. The body/cover and myoelastic/aerodynamic theories explain the glottic cycle and voice production 2. The practical assessment of the voice includes laryngoscopy, speech pathology evaluation, and videostroboscopy 3. Medialization thyroplasty has virtually replaced teflon injections, but newer autologous fat and collagen injections may become more useful 4. reinnervation techniques remain investigative, but hold promise for the future ------------------------------------------------------------------- BIBLIOGRAPHY 1. Kazuhiko Shoji. High-Frequency power ratio of breathy voice. Laryngoscope 1992;102:267. 2. Neterville James. Thyroplasty in the functional rehabilitation of neurotologic skull base surgery patients. Am J. Otology 1993;14(5):460. 3. Mahieu Hans. Indirect microlaryngostroboscopic surgery. Arch Otolaryngol Head Neck Surg 1992;118:21. 4. Tran Quang. Measurement of Young's modulus in the in vivo human vocal folds. Ann Otol Rhinol Laryngol 1993;102:584. 5. Shumrick Kevin. Phonosurgery for voice improvement and restoration In: Medical Clinics of North America 1993 77(3):633. 6. Brandenburg James. Vocal cord augmentation with autogenous fat. Laryngoscope 1992;102:495. 7. Bouchayer Marc. Microsurgical treatment of benign vocal fold lesions: indications, technique, results. Folia Phoniatr 1992;44:155. 8. Ford Charles. Role of injectable collagen in the treatment of glottic insufficiency: a study of 119 patients. Ann Otol Rhinol Laryngol 1992;101:237. 9. Berke Gerald. Laryngeal modeling: theoretical, in vitro, in vivo. Laryngoscope 1987;97:871. 10. Tucker Harvey. 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