29. Benign Laryngeal Lesions | Current Diagnosis and Treatment in Otolaryngology

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Current Otolaryngology > VIII. Larynx & Hypopharynx > Chapter 28. Clinical Voice Assessment: The Role & Value of the Phonatory Function Studies >

Clinical Voice Assessment: The Role & Value of the Phonatory Function Studies: Introduction

The purpose of a clinical voice evaluation is to provide the referring laryngologist with patient-specific, clinically relevant pathophysiologic information of the actual voice production process used by the dysphonic patient, the nature of the dysphonic sound generated by a patient, and the physiologic conditions responsible for the sound. The generated report must be clear and explanatory enough to aid the referring laryngologist with differential diagnosis and treatment planning. Moreover, the generated information must be capable of predicting treatment outcomes and powerful enough to warn the treating physician of any possible complications to the voice that may result from the proposed or planned treatmentwhether medical, surgical, therapeutic, or a combination. Clinical voice evaluation is not a quick procedure. It may take up to 1 hour to conduct phonatory function studies (PhFS) on a noncomplicated patient, whereas it may take a substantially longer time to evaluate a patient who is a professional voice user .

The clinical exam comprises a battery of PhFS composed of at least of two primary parts : (1) an acoustic portion that examines the nature of the generated sound (CPT 92520 and 92506), and (2) a visual portion that examines via stroboscopic transoral or transnasal approach the glottis and surrounding area including the subglottis. Visualization of the subglottis is of paramount clinical value when examining papilloma, trauma, and/or subglottic stenosis patients . The exam must result in a clinically relevant description of the parameters that specify and regulate the vibratory patterns of the vocal cords and/or the other vocal tract elements that are causative of dysphonia. This portion of the exam is coded as 35812 using CPT code. ( Note: When examining alaryngeal patient, additional CPT codes apply.)

Phonatory Function Studies

PhFS consist of acoustic and physiologic components . These studies are considered a standard of modern voice care because they provide information beyond subjective clinical impressions ; they also provide objective descriptions of normal and pathologic phonatory processes. These processes include (1) mapping acoustic voice characteristics, (2) correlating voice with physiologic findings, (3) providing guidelines for the development of efficacious treatment plans, (4) predicting the progress and outcomes of treatment plans, (5) providing preoperative -postoperative lesion mappings, and (6) providing documentation for medicolegal purposes. PhFS are reproducible and allow a contrast of individual results to a database specific to the patient's age and gender. The information these studies provide also allows for a frank discussion with the patient and education of the patient, including discussion of the risks and alternatives associated with various treatments .

The acoustic portion (92520, and various modifiers can be used) records and analyzes the voice of the patient. This portion is of paramount value, specifically when a surgical intervention is planned and when the patient uses voice as a tool of labor. Not having a voice recording of a patient as a chart record is simply inexcusable and must be treated as a serious error on the part of the practicing laryngologist. Having a voice recording is a must even if a litigation is not pending. Do not ignore this part of the exam. Acoustic recordingsif possible video recordingsshould encompass content (vocal-text) relevant to the work needs and work conditions of the patient.

The physiologic portion visualizes via stroboscopic exam (phonoscopy) the mechanics of phonation and also maps the location, the extent, and the effects of phonatory lesions (when present), and their contribution to dysphonia. Keep in mind that a mismatch may be present between the acoustic and visual data (ie, large lesion but a relatively good voice, or a small lesion and a very poor voice), that not all glottic lesions require an immediate surgical procedure, and that not having an organic finding warrants a diagnosis of a functional dysphonia or even worse , a finding of malingering. In today's clinical practice, it is necessary to have at your disposal a comprehensive documentation of the phonatory mechanism. Documentation that shows objectively the location of the lesion or the mechanism of dysphonia is a necessity when postoperative dispute occurs. When operating on a patient, one must have preoperative stroboscopic mapping and voice recordings. Once visualization is conducted , the relevant videographs should be taken to the operating room (OR), placed in OR records, and compared with the visualization obtained during direct laryngoscopy.

In addition to these two primary components, special tests may also be a part of the PhFS battery. These include delayed auditory feedback, voice load tests, nerve blocks, manual compression tests, and so on.

In addition to the goals discussed, the information derived through PhFS is crucial in providing pre- postsurgical documentation, in mapping acoustic and visual lesion(s), and in matching the presence or absence of lesions to the voice quality produced. PhFS are also crucial in documenting follow-up and when considering treatment revision in patient education; moreover, they are a must in medicolegal proceedings .

Izdebski K. Magnetic sound recording in laryngology. Am J Otolaryngol. 1981;2:48.

Izdebski K, Manace ED, Skiljo-Haris J. The challenge of determining work- related voice/speech disabilities in California. In: Dejonkere PH, ed. Occupational VoiceCare and Cure. The Hague: Kugler Publishing, 2001:149154.

Izdebski K, Ross JC, Klein JC. Transoral rigid laryngovideostroboscopy (phonoscopy). Semin Speech Lang. 1990;1:16.

Leonnard R, Izdebski K. Laryngeal imaging with stroboscopy: its value in therapeutic assessment. In Pais Clemente M, ed. Voice Update, International Congress Series 1997, The Hague, Netherlands: Elsevier, 1997.

Voice Production

Voice is an acoustic product resulting from the semicyclical vibrations of the two vocal cords (VC) (ie, vocal folds ) that are located in the larynx, commonly referred to as the voice box. Therefore, abnormal voice is a consequence of the underlying phonatory pathophysiology, reflecting the physical conditions of the vocal cords and the rest of the vocal tract, comprising the subglottic and supraglottic structures.

The vibration of the vocal cords is age and gender dependent and is controlled by myoelastic properties and aerodynamic forces; the vibration is generated as the air expelled under pressure from the lungs passes between the vocal cords and sets the cords into an oscillatory motion.

The myoelastic properties consist of the paired intrinsic laryngeal muscles, which are responsible for the size , shape, length, mass, stiffness, and tension characteristics of the vocal cords. The intrinsic laryngeal muscles include the thyroarytenoid muscles, the pairs of lateral cricoarytenoid muscles, the posterior cricoarytenoid muscles, and the interarytenoid muscle, which consists of both transverse and oblique portions. The intrinsic laryngeal muscles are innervated by the recurrent laryngeal nerves and all muscles, with the exception of the posterior cricoarytenoid muscles (the only vocal cord abductor), are responsible for vocal cord adduction and vocal cord approximation needed for the voice to take place. The bilateral cricothyroid musculature is responsible for the thyroid cartilage downward tilt that elongates the vocal cords. These muscles are principally responsible for pitch elevation. The nonmuscular myoelastic properties include membranes (mucosa), ligaments, glandular elements, a blood supply, and nerves, all of which are located within the articulating cartilaginous housing that comprises the thyroid , the cricoid, and the two arytenoid cartilages.

Normal voice is actually generated by the vibratory wave-generating oscillations of the membranous portion of the vocal cords (the mucosa), which slides/glides in an undulating manner over the underlying muscle. When the mucosa, the submucosal space, the muscles, the vascular elements, the cartilages, or the compression of the glottis are affected, including the subglottic and supraglottic structures, pathologic voice quality results, and voice may not be a product only of the true vocal cords, but may be produced in alternative ways. Therefore, PhFS must be capable of revealing altered phonation and of describing the glottic and the nonglottic mechanism that either generates, confuses, or co-produces the sound of the patient. This description is of paramount importance in differential diagnosis of dysphonia in patients in whom no visible VC pathology is noted, but in whom a dysphonic output is present.

The entire voice box rests on the trachea and is suspended above from the hyoid bone, which communicates with the base of the tongue. When this connection is affected by as little as minor lingual tension or inappropriate vertical larynx positioning, the result may include altered voice production.

In addition to the intrinsic articulation accomplished at the cricoarytenoid and cricothyroid (ie, synovial type) joints, the entire larynx is subject to vertical motions produced by the action of the paired extrinsic laryngeal musculature. These vertical laryngeal motions are crucial in phonation ( singing ), swallowing, respiration, and yawning, and in speech articulation. When this vertical movement is affected, voice production may be severely compromised even if the glottis looks "normal" on a routine ear, nose, and throat exam.

Izdebski K, Dedo HH. Non-glottic phonation in non-laryngectomized patients. A review of compensatory mechanism for alternative phonation sources in humans . In preparation, 2007.

Shipp T, Izdebski K. Vocal frequency and vertical larynx positioning by singers and non-singers. J Acoust Soc Am. 19975;58: 1104.

Titze I. Principles of Voice Production. Englewood Cliffs, NJ: Prentice Hall, 1994.

Motor & Sensory Control

Both voluntary and involuntary phonation occurs after the efferent signals generated in the motor cortex proceed via the brainstem nuclei and the left and right branches of the vagus nerve (CN X) to reach the two vocal cords. Signals terminate in the motor end plates of the intrinsic laryngeal muscles via the left and right recurrent laryngeal nerves, resulting in vocal cord contractions. The entire efferent process can be accomplished within 90 milliseconds , and it requires coordination of all vocal tract and respiratory laryngeal musculature via the central nervous system motor neurons. The coordination of these movements is achieved by a complex neural network with access to phonatory motor neuron pools that receive proprioceptive input from the various receptors associated with these three systems and by control of voluntary vocalization rather than involuntary vocalization involving different brain regions .

The recurrent laryngeal nerve is a mixed nerve containing an average of 1200 myelinated axons and thousands of unmyelinated axons, including some specialized endoneural organs.

The left recurrent laryngeal nerve is longer than the right nerve, but because of the differential axonal composition of both nerves, the efferent impulses manage to arrive at the two vocal cords almost simultaneously , causing the vocal cord vibration to be semi-periodic. This type of vibration makes the sound of the voice "human."

The vagus nerve also branches into the left and right superior laryngeal nerves (SLNs), which mediate the afferent signals from the larynx via their internal branches. The external branches of the SLNs are the motor branches innervating the paired cricothyroid muscles, which function as the primary pitch elevators. This specific vagus nerve branching explains why combined recurrent and superior laryngeal nerve injuries (eg, paralysis) are rare. The action of the cricothyroid musculature is also responsible for the motion of the vocal cords seen in paralysis of the vocal cords due to recurrent laryngeal nerve (RLN) involvement. When some motion of the vocal cord is observed on the paralyzed side, it must be interpreted with caution as a sign of recovery, but rather as motion secondary to the ipsilateral SLN-mediated impulses. When the SLN is out in addition to the RLN, the posterior glottis will not approximate, a wider posterior gap will be present, and the arytenoids will not touch on phonation. Observing and documenting these conditions during clinical PhFS are of paramount importance for treatment planning.

Because of the contra- and ipsilateral innervation of the corticobulbar tract, a unilateral corticobulbar tract lesion will not cause unilateral vocal cord paralysis.

Carlsoo B, Domeij S, Hellstrom S, Dedo HH, Izdebski K. An endoneural microglomus of the recurrent laryngeal nerve. Acta Otolaryngol Suppl. 1982;386:184.

Dedo HH, Townsend JJ, Izdebski K. Current evidence for the organic etiology of spastic dysphonia. Otolaryngology. 1978; 86:87. (Histologic examination of segments of the recurrent laryngeal nerve removed from patients with adductor spasmodic dysphoria revealed myelin abnormalities in 30% of the nerves examined, while neurologic examination indicated brain stem or basal ganglia disturbances.) [PMID: 225708]

Jurgens U. Neural pathways underlying vocal control. Neurosci Biobehav Rev. 2002;26(2):235.

Vocal Cords

With regard to phonation, the vocal cords are subdivided into muscular components (the so-called "body") and nonmuscular components (the so-called "cover"). The body of the vocal cords is formed by the two thyroarytenoid muscles, which contain fast (adductive) and slow (eg, phonatory) fibers that determine the length, contour, and glottic closure shape of the vocal cords and that regulate the tension of the cover that slides over the body of the vocal cords to create the mucosal vibratory wave. The mucosal vibratory wave cannot be observed with simple visualization, but under stroboscopic illumination or super-fast filming , where it is seen to undulate, proceeding from the inferior (ie, lower lip) to the superior surface (ie, upper lip) of the vocal cords (Figure 281).

The area between the upper and lower lips adjusts as pitch and loudness change; therefore, when a phonatory lesion is located within this space, its location and size determine the area of pitch and loudness dysfunction. Typically, more severe symptoms are caused by small but anteriorly located lesions than by larger lesions located toward the upper lip or on the superior phonatory surfaces. Typically, an anterior commissure lesion located 3 mm above the lower lip profoundly affects the voice, whereas even a large inferiorly located web (< 3 mm below the lower lip) does not affect the voice. This is crucial to both treatment and diagnosis. To secure this observation, PhFS are needed.

The cover is subdivided into the outer and the inner layers and the lamina propria; the latter consists of three layers : superficial (the Reinke space), intermediate, and deep. The vocal ligament is the free edge of the conus elasticus, belonging to the deep and intermediate layers of the lamina propria. Obliteration of the Reinke space retards or prevents the mucosal vibratory wave, resulting in dysphonia of varying severity. However, if one vocal cord is stiff but straight (nonvibratory) and the other vibrates and approximates well against the nonvibrating vocal cord, the voice may be remarkably good despite the insufficiency of one cord. Therefore, it is important at times not to "repair" the stiff vocal cord, but to leave it alone or even make it stiffer to improve the overall voice quality. Most benign phonatory mucosal lesions are typically found within the superficial layer. If the lesion is located on the superior surface of the vocal cord away from the vibratory edge, the voice may not be affected at all, even if the lesion is large. These findings are crucial in determining the extent of surgical interventions. A common sense real estate rule of "location, location, location" should prevail. In other words, it is often the location and not the size of the lesion that determines its value to the voice quality.

From the clinical point of view, vocal cords are also subdivided into the vibratory (membranous) and nonvibratory (cartilaginous) portions. At rest, they outline a V-shaped space called the glottis (see Figure 281). The front of this V forms the anterior glottic commissure, and the back of the V forms the posterior glottic commissure. The posterior end of each vocal cord (the thyroarytenoid muscle) inserts into the muscular process of each of the arytenoid cartilages. The maximum width of the posterior commissure occurs during inspiration or cough and measures approximately 912 mm, or three times the most posterior width of the muscular portion of the vocal cord at rest.

After puberty, the length of the vibratory portions of the vocal cords at rest is approximately 13 mm for women and 16 mm for men. When the vocal cords approximate for phonation, the entire glottis is closed in a male, whereas a small posterior chink is often present in a female, giving the female voice quality a slightly softer and airy tone. The specific shapes of glottic phonatory closure allow variations in normal voice qualities.

Furthermore, the vocal cords are clinically subdivided into anterior, middle, and posterior thirds, with nodular lesions usually located at the anterior third juncture and opposite each other if bilateral. An asymmetric location of mucosal lesions is found in mixed-type organic dysphonias.

Dworkin JP, Meleca RJ. Vocal Pathologies: Diagnosis, Treatment and Case Studies. San Diego: Singular Publishing Group , 1997.

Hirano M. Structure and vibratory behavior of the vocal folds. In: Sawashima T, Cooper F, eds. Dynamic Aspects of Speech Production. Tokyo: Tokyo University Press, 1977:3.

Schonharl E. Die Stroboskopie in der Praktischen Laryngologie. Stuttgart: Thieme, 1960.

The Vibratory Process

The two thyroarytenoid muscles, together with the other intrinsic laryngeal muscles and the extrinsic laryngeal muscles, control the relative elasticity and stiffness of the vocal cords. They also determine the shape of the mucosal vibratory wave, which in turn determines the pitch, loudness, and tone of the voice. The amplitude of the mucosal vibratory wave is wider at the lower pitches, whereas reduced mucosal vibratory wave amplitude predominates at high pitches or at any pitch level when the cover is stiff.

The duration and shape of the mucosal vibratory wave cycle form specific opening and closing phases that determine specific vibratory modes or vocal qualities (eg, fry, normal, overpressured, breathy, or falsetto). The time interval between cycles is called the fundamental period (F ), whereas in perceptual terms it is referred to as a pitch period.

The Aerodynamic Properties of Phonation

The aerodynamic properties of phonation include the subglottic air pressure (P _s ), the airflow, the supraglottic pressure (P _s ), the intraoral pressure (P _io ), and the glottal resistance, all of which are responsible for the Bernoulli effect, which separates the approximated vocal cords during phonation.

To generate sound, P _s must reach at least 5 cm H ₂ O, but P _s can exceed 50 cm H ₂ O in loud or overly pressured (ie, pathologic) phonation. Typically, a normal conversational voice is produced between 610 cm H ₂ O P _s at approximately 6570 dB, whereas a loud voice can reach 8595 dB.

The mean airflow in normal phonation ranges from 89 to 141 mL/s and increases as the fundamental period and the loudness are elevated. The glottal resistance cannot be measured directly, but is estimated to vary from 20 to 150 dyne/s/cm ³ depending on the pitch and sound intensity.

Izdebski K. Overpressure and breathiness in spastic dysphonia. An acoustic (LTAS) and perceptual study. Acta Otolaryngol Scand. 1984;97:122. (Pre- and post-recurrent laryngeal nerve section speech segments spoken by adductor spasmodic dysphoria patients were analyzed by long-time-average-spectrum (LTAS) analysis and perceptually for breathiness and overpressure. Breathy phonation corresponded to a steep fall in the LTAS, whereas overpressured phonation produced higher spectral levels and a less steep fall. Correlation with perceptual assessment of weak and strangled voice was shown to be valid.) [PMID: 6720314]

Shipp T, Izdebski K, Schutte H. Subglottic air pressure in adductor spasmodic dysphonia. Folia Phoniatrica. 1985;43:114. (Article explaining the physiologic reasons and the techniques of subglottic pressure measurements and their application in examining pathologic voices.) [PMID: 3220337]

Resonation

When the voice (F ) resonates within the entire vocal tract (ie, the larynx, trachea, pharynx, and oral and nasal cavities) and when the vocal tract articulates, speech, singing, or other forms of communication are formed. Because of specific vocal tract configuration, in the voices of opera singers, specific sound regions are amplified; these areas are referred to as formants (F1F5), and their combination determines the characteristic of each vowel. Opera singers form unique vocal tract shapes to allow noninjurious and efficient singing, and they show a unique clustering of powerful spectral peaks (the so-called singing formants) at about 3 kHz. This clustering results in an acoustic boost that helps a singer to compete with the sound of an orchestra. The production of singers' formants is possible when the entire larynx is lowered in the neck, but not when the larynx goes up as pitch elevates. Other acoustic features are emphasized in different singing styles. Because inappropriate larynx tracking can be potentially injurious to the voice, an examination of the vertical larynx position (VLP) is advised when evaluating the vocal problems of individuals who use their voices professionally. Ornamentation in voice can result from specific vocal tract configurations and specific time-locked acoustic events, with rate approximating 56 Hz for vibrato or vocal tremor. It is interesting to note that tremor-like vocal oscillations having similar rate may be present in deception.

Shipp, T, Izdebski K. Letter: Vocal frequency and vertical larynx positioning by singers and nonsingers. J Acoust Soc Am. 1975;58(5):1104. (This article explains the reasons singers and nonsingers adjust their vocal tracts to produce acoustically advantageous effects.) [PMID: 11945621]

Shipp T, Izdebski K. Current evidence for the existence of laryngeal macrotremor and microtremor. J Forensic Sci. 1981;26: 501. (The existence of laryngeal microtremors was tested using vocal vibrato in normal singers and in vocal tremor.) [PMID: 7252466]

Stone RE Jr, Cleveland T, Sundberg J. Formant frequencies in country singers' speech and singing. J Voice. 1999;13:161. (The study describes acoustic differences in voice quality in the same singer when the singer speaks and sings.) [PMID: 10442747]

Laryngologic Conditions

A multitude of laryngologic conditions can cause voice problems. Some of these conditions demonstrate a visible organic pathology on an initial routine ear, nose, and throat (ENT) exam, either with a mirror or fiberoptics. Other conditions do not. Therefore, it is extremely important not to dismiss a patient's claim of "hoarseness," specifically in the absence of a visible pathology. Any voice condition, but specifically when hoarseness is present and the larynx looks normal, calls for PhFS to be performed as soon as possible. Delays in arriving at a diagnosis can result in medical complications (including potential legal consequences), as well as delays in treatment and a potential loss of income to the patient. Unfortunately, the concerns of many patients with dysphonia, especially patients who use their voices professionally, are often dismissed. These patients may be accused of "wrong" singing or poor training because no visible pathology was noted at the initial routine medical or ENT exam and because referrals for in-depth voice evaluations are not always initiated.

The specific conditions that can affect voice production are numerous and include the following: (1) congenital anomalies that can cause dysphonia by changing the shape and form of the mucosal vibratory wave; (2) benign vocal cord lesions that affect the mucosal vibratory wave, resulting in air loss, noise, vocal cord stiffness, and pitch restrictions; (3) premalignant and malignant lesions that restrict or obliterate the mucosal vibratory wave; (4) infectious and inflammatory disorders of the larynx, which can cause a variety of vibratory and approximation changes, depending on the severity and extent of the disease; (5) acquired voice disorders; (6) neurologic disorders that can affect all aspects of phonatory processes; (7) blunt or penetrating trauma to the larynx that causes injury (eg, fractures, dislocations, or crushes) to the laryngeal housing and the neural or vascular supplies ; (8) pharmacologic agents that have either adverse effects (eg, antihistamines, virilizing drugs) or positive effects (eg, hydrating agents , asthma inhalers, corticosteroids, and bronchodilators); (9) iatrogenic dysphonia caused by (a) a clinical intervention in a nondysphonic patient (eg, vocal cord paralysis that results from an unintentional injury to the recurrent laryngeal nerve), (b) the planned treatment (eg, an overinjection of polytef [ie, Teflon] during attempts to correct breathy paralytic dysphonia or irradiation), or (c) a change to the underlying nature of the primary dysphonia as a function of treatment (eg, denervation of the vocal cord to combat vocal spasticity, Botox, and vagal stimulation); (10) functional dysphonia (eg, persistent prepubertal voice in a postpubertal male, elective aphonia, ventricular dysphonia, and inhalational dysphonia); (11) gender euphoria; (12) emotional causes; and (13) environmental-occupational causes.

Gastroesophageal reflux disease (GERD) has been recently linked to a multitude of voice disorders. However, this association is controversial , and cause-effect correlation is far from being established unequivocally. Some clinicians, however, believe that GERD is the primary cause of many voice problems, whereas others minimize its role in the formation of dysphonia. When GERD is perceived as the cause of voice disorders, it is cited as causing changes that range from alterations of vocal cord mucosa to more general supraglottic tissue changes. GERD may cause a chronic or intermittent dysphonia that is characterized by vocal fatigue, voice breaks, cough, globus syndrome, and, occasionally, dysphagia.

Flower RM, Izdebski K. Common Speech Disorders in Otolaryngologic Practice. Rochester, Minnesota: American Academy of Otolaryngology Press, 1979.

Izdebski K, ed. Emotions in the Human Voice. Volumes 13. San Diego: Plural Publishing, 2007.

Izdebski K, Dedo HH, Wenokur R, Johnson J. Voice and vocal cord findings in asthma inhaler (Advair) users. Western Section: Triological Society. San Diego, California. February 3, 2006. In press (2007).

Koufman JA. Gastroesophageal reflux and voice disorders. In: Rubin JS, Sataloff RT, Korovin GS, Gould WJ, eds. Diagnosis and Treatment of Voice Disorders. New York: Ikagu-Shoin, 1995:161.

Rubin JS, Sataloff RT, Korovin GS, Gould WJ. Diagnosis and Treatment of Voice Disorders. New York: Ikagu-Shoin, 1995.

Ylitalo R, Lindestad PA, Ramel S. Symptoms, laryngeal findings, and 24-hour pH monitoring in patients with suspected gastroesophageal-pharyngeal reflux. Laryngoscope. 2001;111(10):1735. (Discussion of controversies of GERD on voice and its role in formation of various dysphonias.) [PMID: 11801936]

Acoustics

An acoustic voice assessment provides information on the nature of the generated sound and should include physical voice recordings (analog, digital, or video) and an objective acoustic analysis; it should also include a subjective psychoacoustic analysis, a psychometric analysis, a phonometric analysis, or all of the above. The psychoacoustic and psychometric analyses require a trained ear and longstanding expertise, not unlike what is needed to assess auscultatory noises. However, the problems with these analyses result from the potential for loose terminology and a non-uniform interpretation. A subjective description of one type of dysphonia used over 350 different clinical terms. Therefore, using numerical perceptual rating scales is preferred when subjectively assessing voice problems. Attempts to use acoustic objective analysis to detect voice quality correlations with underlying pathology continue, but solutions are far from being reached.

Godino-Llorente JI, Gomez-Vilda P, Blanco-Velasco M. Dimensionality reduction of a pathological voice quality assessment system based on Gaussian mixture models and short- term cepstral parameters. IEEE Trans Biomed Eng. 2006;53(10):1943. (Paper demonstrates promising acoustic technique in detecting voice pathologies.) [PMID: 17019858]

Izdebski K. Spastic dysphonia. In: Darby J, ed. Speech Evaluation in Medicine and Psychiatry, Vol. II: Medicine. New York: Grune & Stratton, 1981.

Izdebski K, Shipp T, Dedo HH. Predicting postoperative voice characteristics of spastic dysphonia patients. Otolaryngol Head Neck Surg. 1979;87:428. (Describes techniques of predicting surgical voice outcomes of selected dysphonic patients based on presurgical phonatory function studies.) [PMID: 503503]

Subjective Assessment

The subjective assessment often uses a mixture of perceptual and musical terms to describe the patient's voice quality, pitch, loudness, the duration and rate of phonation, prosody , registration, tessitura, and respiratory characteristics.

Common Assessment Findings

Below is a review of terms used to clinically describe the various dysphonic qualities. These semantic descriptors can be quite accurate, but when the voice is abnormal the term hoarseness is a generic word used by most clinicians (and lay people) when referring to or describing many kinds of dysphonia. Hoarseness is frequently used as a wastebasket term and leads to a wrong impression or diagnosis. It is especially used in error when one is attempting to define a rough or harsh voice quality, since this is typically associated with vocal cord stiffness and possibly cancer.

Breathy or soft voice is used to describe a voice that is generated by incomplete glottic closure (eg, in unilateral vocal cord paralysis, vocal cord bowing, neurologic disorders, benign mucosal lesions, and psychogenic voice disorders).

A tight, strangled, or strained voice represents an overclosed glottis and is found in dystonias and pseudobulbar palsies, including psychogenic disorders.

A diplophonic or multiphonic voice is present when the vibratory pattern between the vocal cords or within a single vocal cord is unequal . This condition can be caused by a myriad of benign and malignant mucosal lesions, neurologic complications, laryngeal fractures, or psychosomatic problems.

A wet, gargling voice, also referred to as hydrophonia, describes phonation that is produced by excessive mucus within the glottic space.

A rough voice may describe a true vocal cord vibration that is mixed with a ventricular vibration. This may be present when mucosal lesions are found between the lower and upper phonatory lips and when mucosal wave is partially obliterated.

A harsh, rough, and stiff voice quality with a short maximum phonation time should be used to refer to voices that are produced with adynamic "cover." This can be found in invasive carcinoma or in Teflon overinjection, or when mucosa is prevented from vibration by lesions pressing on the vocal cord from above.

A shrill, metallic voice with abrupt onset can be associated with muscular tension dysphonia, a benign phonatory lesion, and hyperfunctional dysphonia.

Sudden pitch or loudness breaks in the absence of clearly visible phonatory mucosal lesions may be an indicator of functional problems, postpubertal dysphonia, or virilization of the female voice.

A limited upper pitch range with soft breathy phonation, no mucosal lesions, and rotation of the posterior larynx can indicate superior laryngeal nerve involvement.

Rapid pitch (at about 56 Hz) and intensity oscillations reflect vocal tremor, whereas pitch-dependent oscillations or vocal arrests reflect specific movement disorders, while in muscular tension dysphonia, or functional (psychosomatic) dysphonia oscillations my be random.

Odynophonia describes a sensation rather than voice quality and is associated with pain or discomfort when speaking or vocalizing.

Total aphonia, or lack of voice in the absence of a phonatory cough, can indicate severe separation of the glottis either caused by organic and functional origins or following total laryngectomy. Ankylosis of the arytenoid cartilages can be suspected, but when a phonatory cough is present, total aphonia should arouse suspicion of a psychosomatic conversion dysphonia.

Stridor should be reserved to describe uncontrollable vocal production ("voicing") during inhalation, when the glottis is not abducting. Asthma-like wheezing happens only on exhalation when the vocal cords are open . When female patients inhale asthma medications, vocal cord mucosa can be affected and severe dysphonia can occur. Typically, stopping medication is enough to reverse the condition.

No matter how the voice sounds, the sound of the pathologic voice may evoke negative emotions that are noncongruent with the emotions intended by the patient. This incongruence can be very frustrating and may cause a patient to react as if the condition has a functional cause, when it clearly does not. An understanding of these factors by the examining clinician goes a long way toward enhancing bedside manners.

Acoustic Analysis

Acoustic analysis provides an objective and quantitative description of the generated sound in a reliable and noninvasive way. The purpose is to map out phonatory characteristics, demonstrate phonatory deficits, and correlate findings with visual (ie, physiologic) data. Barring minor technical problems, either dedicated instrumentation or a computerized approach can be used for a fast, reliable, and reproducible acoustic analysis. Acoustic analysis provides information on sound duration, loudness, pitch, and spectral context, including static and dynamic pitch changes of the voice during speech.

Izdebski K. Pathologic voice evokes wrong emotions. In: Izdebski K, ed. Emotions in the Human Voice. San Diego: Plural Publishing, to be published in 2007.

Shipp T, Izdebski K. Current evidence for the existence of laryngeal macrotremor and microtremor. J Forensic Sci. 1981;26:501. (Analyzes the existence of laryngeal microtremors detected during deception versus the macrotremors found in the voice of singers and also found in vibrato and subjects with pathologic vocal tremor, using electromyographic and acoustic signals from laryngeal muscles.) [PMID: 7252466]

Wheeler KM, Collins SP, Sapienza CM. The relationship between VHI scores and specific acoustic measures of mildly disordered voice production. J Voice. 2006;20(2):308. (Elucidates the relation between the Voice Handicap Index and laboratory measurements and shows that these two methods give independent information and essentially correlate poorly.) [PMID: 16126368]

Pitch Assessment

Pitch expressed in musical intervals is a perceptual and therefore subjective measure. However, in objective acoustic terms, pitch refers to the fundamental frequency of the voice or the speaking fundamental frequency, both of which are recorded in vocal cycles per second or hertz (Hz). Deviations in the fundamental frequency are expressed by jitter measures, or a pitch perturbation factor. Jitter is defined as a fundamental frequency value that is obtained by subtracting the duration of the pitch period from the duration of the period immediately preceding it. Because pitch changes over time, serial correlation coefficients may be used to more accurately represent these changes. The pitch pattern is related to the intensity profile as shown in Figure 282.

Fundamental frequency is age and gender dependent. The average level of fundamental frequency for a child is approximately 250 Hz; it is 200 Hz for an adult female, and for an adult male, it is approximately 120 Hz. The maximum fundamental frequency range for both genders is from 36 Hz to 1760 Hz, or roughly the distance from D1 to A6 on a piano. Vocal training can develop an individual's voice to be an exquisite instrument; an extreme vocal span can range over four octaves (eg, from E3, which is approximately 164 Hz, up to F6, which is approximately 1760 Hz).

The speaking fundamental frequency of males typically drops with the termination of a spoken sentence without constituting a pathologic condition. In contrast, the fundamental frequency of females is often elevated at the end of a spoken sentence. This distinction is of import when examining patients with gender reassignment, patients on psychotropic medications, or those with a history of using virilizing drugs. The speaking fundamental frequency of females drops over the life span, whereas this frequency becomes elevated in male geriatric populations.

When assessing patients who sing professionally, their vocal registration should be included in the evaluation. Using a musical scale notation is a preferred method of communicating clinical findings to these patients.

Baken RJ. Clinical Measurements of Speech and Voice. San Diego: College Hill Press, 1997.

Izdebski K, Ross JC, Klein JC. Rigid transoral laryngovideostroboscopy (phonoscopy). Semin Speech Lang. 1990;1:16.

Loudness Assessment

Loudness represents acoustic intensity that is measured in decibels and is dependent on both the subglottic air pressure and the airflow exiting the glottis. Obtaining the absolute phonatory intensity is difficult; therefore, it is typically reported in relative rather than in absolute decibels. Moreover, because the acoustic intensity is affected by the fundamental frequency, normal loudness is actually greatest at mid-frequency ranges and lowest at both the low and high levels of fundamental frequency. As with fundamental frequency, means, medians, standard deviations, coefficients of variation, and loudness perturbation factors (known as "shimmer") are used to describe acoustic intensity variation and dispersion. The typical loudness level of speaking is approximately 6575 dB. Values below or above this measure are considered pathologic.

Phonetogram

To make a more orderly representation of pitch and loudness, a profile of the fundamental frequency, measured in decibels and referred to as a phonetogram, has been developed. The phonetogram, which is a voice range profile, represents the minimums and the maximums of vocal loudness at selected levels of fundamental frequency within the total frequency range of a speaker (Figure 283). Clinically, a phonetogram is a reflection of the vocal capacities rather than the measurement of the glottic function. Vocal intensity profiles are used to assess vocal cord paralysis, vocal cord bowing, presbyphonia, odynophonia, functional disorders, and patients who use their voices professionally.

Spectral Analysis

Spectrography

Spectrography (Figure 284) provides a three-dimensional representation of sound: time, intensity, and frequency. Narrow-filter spectrography shows the harmonic structure ( partials ) of the sound, from which values of fundamental frequency can be derived. Wide-filter spectrography shows vocal tract resonation, represented by the formants (ie, F1F5).

Spectrography provides information on (1) noise; (2) phonatory breaks; (3) vocal discontinuity; (4) diplophonia; (5) the size and speed of fluctuations in the fundamental frequency; (6) the size and speed of amplitude fluctuations; (7) the richness of harmonics; (8) the relative noise level; (9) an analysis of rising and falling tones, as well as voice efficiency over time; and (10) glottic air transfer. These features are critical when analyzing vocal cord stiffness, vibratory irregularity due to lesions that are benign, mucosal, iatrogenic (eg, with the use of Teflon or thyroplasty), or that cause adynamic vibration. These features are also significant when evaluating patients who use their voices professionally, have neurologic or functional dysphonias, have carcinoma, or experience stridor, noise, wheezing, or obstructive airway problems (eg, snoring).

Long-Time Average Spectrum

The long-time average spectrum technique is used to plot compressed speech spectrum levels over time. This technique relates the acoustic parameters to perceptual observations and has been used successfully to describe various dysphonias.

Izdebski K. Overpressure and breathiness in spastic dysphonia: an acoustic and perceptual study. Acta Otolaryngol. 1984;97:373. (Pre- and post-recurrent laryngeal nerve section speech segments spoken by adductor spasmodic dysphoria patients were analyzed by long-time-average-spectrum (LTAS) analysis and perceptually for breathiness and overpressure. Breathy phonation corresponded to a steep fall in the LTAS, whereas overpressured phonation produced higher spectral levels and a less steep fall. Correlation with perceptual assessment of weak and strangled voice was shown to be valid.) [PMID: 6720314]

Multidimensional Voice Profile

The multidimensional voice profile displays, in a graphic form, multiple vocal parameters all at one time (Figure 285). The use of the multidimensional voice profile is advantageous in comparing pretreatment and post-treatment results. It also provides an overall description of dysphonia, because single acoustic parameters alone are insufficient in delineating the complexity of phonatory pathologies. The multidimensional voice profile can compare individual clinical data with a built-in database adjusted to age and gender. Therefore, this profile is very useful in analyzing changes over time.

Rate Analysis

Instrumentally based rate analyses are used to define the rate and extent of specific acoustic variations (ie, vocal tremor, vocal arrests, or vibrato). Rate analysis is used in the differential diagnosis of vocal movement disorders and in assessing the vocal problems of singers. Pathologic vocal rates are between 5 Hz and 6 Hz, a rate similar to the vibrato rate.

Dejonckere PH, Hirano M, Sundberg J. Vibrato. San Diego: Singular Publishing Group, 1995.

Vocal Cord Contact Area

A normal voice is produced when the glottic approximation is normal during sustained phonation. The percentage of vocal cord contact area loss can be derived from acoustic measures. When a voice is hoarse, the percentage of phonatory contact (ie, perturbations) goes down. Values below 90% are considered abnormal.

Vowel Space

Vowel quality is affected by the fundamental frequency and loudness. Therefore, substantial difficulties in maintaining vowels on target are encountered when singers must sing loudly. These elevated levels make for the poor intelligibility of sung text. Therefore, vowel production should be examined when studying patients who sing professionally.

Maximum Phonation Time

The maximum phonation time corresponds to the time an individual can phonate per each inhalation. Normal maximum phonation time values are between 17 and 35 seconds for adult males and between 12 and 26 seconds for adult females. A reduction of the maximum phonation time is expected in a hypofunctional glottis, whereas prolonging this time is characteristic for an overapproximated glottis. Although the maximum phonation time lacks diagnostic capabilities, it is useful in the preoperative and postoperative assessments of unilateral vocal cord paralysis and bowing, in monitoring medialization (eg, thyroplasty or various intracordal injections), and in lateralization procedures (eg, Botox injections, as well as nerve resections, blocks, or stimulation).

Baken RJ. Clinical Measurements of Speech and Voice. San Diego: College Hill Press, 1997.

Hirano M. Clinical Examination of Voice. New York: Springer-Verlag, 1981.

Physiologic Voice Evaluation

Physiologic voice evaluation comprises rigid or flexible stroboscopic visualization, aerodynamics, glottography, electromyography, and special studies.

Phonoscopy

Phonoscopy refers to stroboscopic (or laryngovideostroboscopic) visualization of the vocal cords during vibration (Figure 286). It is considered to be a principal procedure among PhFS studies. The technique is based on the principle of illuminating a vibrating object with light flashes just below or above the frequency at which it vibrates, therefore making the vibrating object appear at a standstill or as if it is vibrating in slow motion. Laryngovideostroboscopy or digital stroboscopy provides an image of the vocal cord vibrations averaged over many vibratory cycles while newly introduced high speed stroboscopy shows consective cycles and not averages it can only show short sign duration. The most detailed images are obtained either via a 90 or a 70 rigid transoral scope. The images are captured on videotape or in digital form and are displayed on a monitor for either immediate or subsequent viewing and analysis.

Phonoscopy provides the clinician with a wealth of information. Among the large amount of information it provides, phonoscopy (1) maps the location of the phonatory lesion in relationship to the acoustic findings, (2) gives fundamental frequency values, (3) shows the symmetry of vocal cord vibrations, (4) reveals the configuration of the glottic closure, (5) shows the horizontal excursion of the vocal cords (ie, their amplitude), (6) reveals the appearance and the workings of the upper and lower phonatory lips, (7) shows the type and the nature of the glottic closure, and (8) demonstrates the nature of the mucosal vibratory wave (including the presence or absence of adynamic segments). Compared with traditional exams, a phonoscopic exam significantly increases the diagnostic accuracy and therefore provides for more effective treatment options.

Colton R, Casper JK. Understanding Voice Problems: A Physiological Perspective for Diagnosis and Treatment. Baltimore: Williams & Wilkins, 1996.

Dworkin JP, Meleca RJ. Vocal Pathologies: Diagnosis, Treatment and Case Studies. San Diego: Singular Publishing Group, 1997.

Hertegard S, Larsson H, Wittenberg T. High-speed imaging: applications and development. Logopedics Phoniactrics Vocology 2003;28:3,133139.

Hirano M. Clinical Examination of Voice. New York: Springer-Verlag, 1981.

Izdebski K, Ross JC, Klein JC. Rigid transoral laryngovideostroboscopy (phonoscopy). Semin Speech Lang. 1990;1:16.

Remacle M. The contribution of videostroboscopy in daily ENT practice. Acta Oto Rhino Laryngologica Belg. 1996;50:265. [PMID: 9001636]

Electroglottography

Electroglottography is another method of evaluating vocal cord vibration. This technology uses the principle of electrical impedance across tissue and open space. Electrodes are placed on the neck over the lamina of the thyroid cartilages; a weak current is passed between the electrodes, which generate an impedance curve that corresponds to the shape and nature of the vibratory cycle.

Other forms of glottographic technology include photoelectric and ultrasound glottography. A new technique of assessing vocal cord cycles based on the kymography principle has been recently introduced; however, its clinical value remains questionable at this time.

Guimaraes I, Abberton E. Fundamental frequency in speakers of Portuguese for different voice samples. J Voice. 2005; 19(4):592. (This article shows usage of electroglottography to assess voice qualities across gender and age.) [PMID: 16301105]

Larsson H, Hertegard S, Lindestad PA, Hammarberg B. Vocal fold vibrations: high-speed imaging, kymography, and acoustic analysis: a preliminary report. Laryngoscope. 2000;110 (12): 2117. (This article suggests that combined high-speed acoustic-kymographic analysis package can be helpful for specification of the terminology of voice qualities.) [PMID: 11129033]

Yan Y, Ahmad K, Kunduk M, Bless D. Analysis of vocal-fold vibrations from high-speed laryngeal images using a Hilbert transform-based methodology. J Voice. 2005;19(2):161. (This article assesses potential use of this tool for voice pathology analysis.) [PMID: 15907431]

Zagolski O, Carlson E. Electroglottographic measurements of glottal function in vocal fold paralysis in women. Clin Otolaryngol Allied Sci. 2002;27(4):246. (This article suggests that electroglottography is a suitable noninvasive tool for tracking the patients' long-term progress.) [PMID: 12169125]

Aerodynamic Tests

The purpose of aerodynamic tests is to evaluate how air"the voice fuel"behaves during phonation. Aerodynamics measure subglottic and supraglottic (ie, intraoral) air pressures as well as the glottic air impedance and the type of airflow at the glottis, including the volume velocity.

Aerodynamics is important when assessing vocal cord paralysis, stenosis, webs, or patients who use their voices professionally (ie, singers). Aerodynamic tests are important when examining a voice that may have been affected by the inhalation of noxious gases or stage smoke. They are also useful when the volume of gas expired during the first second (the forced expiratory volume in the first second, or FEV ₁ ) from the beginning of the forced vital capacity (FVC) shows deficits (eg, methacholine challenge).

Measurements of phonatory airflow are performed via pneumotachography on vocalic segments; they differ from pulmonary function studies in that airflow is measured as a function of phonation. The individual values can be fitted against expected age and gender values, with critical values for a normal population ranging from 40 to 200 mL/s. The interpretation of aerodynamic tests should be conducted with caution because these tests are subject to voluntary motor responses and are affected by variations in vocal intensity and vocal register.

Granqvist S, Hertegard S, Larsson H, Sundberg J. Simultaneous analysis of vocal fold vibration and transglottal airflow: exploring a new experimental setup. J Voice. 2003;17(3):319. (This article critically reviews airflow across the glottis. The article points that relationships between these two entities is complex specifically with respect to phonation modes.) [PMID: 14513955]

Electromyography

An electromyogram (EMG) examines the neuromuscular integrity of a striated muscle by recording in a visual form, an auditory form, or both, the electrophysiologic properties (ie, discharges) of the muscle. These discharges provide information on the characteristics of single motor unit potential as well as on the interference pattern representing serial muscle discharges over time (Figure 287).

Specialized equipment is needed to conduct an EMG. Typically, either needle or hooked-wire electrodes are used. Surface electrodes can only be used to sample muscles that are close to the skin's surface (ie, the cricothyroid muscle or the extrinsic laryngeal muscles). When examining the motor unit potential, needle electrodes, preferably bipolar, should be used.

The usefulness of laryngeal EMG in diagnosing dysphonia has not been well established, including assessing unilateral or bilateral vocal cord paralysis. It is difficult at times to conclude whether the muscle is undergoing denervation or reinnervation; in this circumstance, the clinical experience of the examiner plays an important role.

Blitzer A. Laryngeal electromyography. In: Rubin JS, Sataloff RT, Korovin GS, Gould WJ, eds. Diagnosis and Treatment of Voice Disorders. New York, Tokyo: Ikagu-Shoin, 1995.

Dedo HH, Hall WN. Electrodes in laryngeal electromyography: reliability comparison. Ann Otol Rhinol Laryngol. 1969;78: 172. (Article discusses that using unipolar electrodes will provide word information.) [PMID: 5763185]

Jacobs IN, Finkel RS. Laryngeal electromyography in the management of vocal cord mobility problems in children. Laryngoscope. 2002;112:1243. (Evaluates the efficacy and usefulness of electromyography, with a specific focus on the pediatric patient as well as in determining the differential diagnosis of vocal cord paralysis versus vocal cord fixation.) [PMID: 12169907]

Shipp T, Izdebski K, Reed C, Morrisey P. Intrinsic laryngeal muscle activity in a spastic dysphonia patient. J Speech Hearing Dis. 1985;50:54. (Description of electromyography activity from intrinsic laryngeal muscles in adductor spasmodic dysphoria demonstrated normal morphology of recurrent laryngeal nerves and intrinsic laryngeal muscles and suggested a neurologic cause for this disorder .) [PMID: 3974213]

Sittel C, Stennert E, Thrumfart WF, Dapunt U, Eckel HE. Prognostic value of laryngeal electromyography in vocal fold paralysis. Arch Otolaryngol Head Neck Surg. 2001; 127:155. (This article analyzes the value of electromyography in predicting vocal function recovery from acute neurogenic injuries [ie, paralysis] of the vocal cords.) [PMID: 11177032]

Woo P. Laryngeal electromyography is a cost-effective clinically useful tool in the evaluation of vocal fold function. Arch Otolaryngol Head Neck Surg. 1998;124:471. (Outlines the clinical usefulness of electromyography in evaluating various vocal cord dysfunctions in the absence of visible organic mucosal lesions.) [PMID: 9559701]

Yin SS, Quu WW, Stucker FJ. Major patterns of laryngeal electromyography and their clinical applications. Laryngoscope. 1997;107:126. ( Presents detailed electromyographic [EMG] techniques and describes physiologic tasks needed to study the actions of the intrinsic laryngeal muscles by EMG in various groups of dysphonic patterns.) [PMID: 9001277]

Special Studies

When studying complex voice problems, specially tailored voice tests often need to be designed or conducted. These special tests include acoustic, physiologic, and radiographic studies.

Acoustic Tests

Special acoustic tests include the voice load test, auditory masking, voice performance tests, phonetically balanced tests, delayed auditory feedback, and the use of an electrolarynx. These tests are useful when determining the differential diagnoses of psychogenic dysphonias.

Izdebski K. The voice load test: an objective acoustic test to assess voice quality as a factor of voice usage over time. In Proceedings of the 2nd World Voice Congress and 5th International Symposium on Phonosurgery. Sao Paulo, Brazil. 1999.

Physiologic Tests

Special physiologic tests include aerodynamic tests, manual pressure tests, and temporary denervation procedures. An upper esophageal insufflation test is used to test failures in acquiring voice after tracheal puncture procedures. Because sudden change in aerodynamics affects the glottic biomechanics, as does inhaling gases of other density than air (eg, helium), such tests are useful when examining a suspected psychogenic voice disorder.

The manual pressure test, also known as the laryngeal circumference pressure test, is useful in testing for muscular tension dysphonia as well as psychogenic dysphonia. It is also useful in assessing the viability of medialization procedures. Similarly, the head-positioning test, which can cause changes in vocal cord approximation, can be used as a predictor of the correction potential (therapeutic, surgical, or both) of breathy dysphonia. A neck pressure test can also be used to test failures in acquiring voice after esophageal injection (eg, following total laryngectomy).

An array of nerve blocks, as well as the so-called oral lidocaine bath, can be very useful in the differential diagnosis of psychogenic dysphonia. In addition, a recurrent laryngeal nerve block is often crucial in testing for adductor spasmodic dysphonia and vocal tremor. A temporary block of the superior laryngeal nerves can be used in testing for abductor spasmodic dysphonia and in persistent postpubertal infantile dysphonia. The neural block test can also be used to test problems with air insufflation in patients after a total laryngectomy.

Radiologic PhFS include a videofluoroscopic exam of a nonfunctional phonatory segment after total laryngectomy. It also appears that neuroradiographic studies that use enhanced viewing to reveal fat deposits in vocal cords may be useful in studying nonmobile vocal cords. With additional testing, this technique may prove to be excellent in the differential diagnosis of voice disorders due to vocal cord paralysis or due to mechanical problems (eg, arytenoid joint dislocation or vocal cord fixation, or ankylosis).

Izdebski K, Dedo HH. Selecting the side of the RLN section for spastic dysphonia. Otolaryngol Head Neck Surg. 1981;89:423.

Izdebski K, Manace ED, Skiljo-Haris J. The challenge of determining work-related voice and speech disabilities in California. In: Dejonkere PH, ed. Occupational Voice: Care and Cure. Hague, Netherlands: Kugler Publishers, 2001.

Izdebski K, Ward R. Differential diagnosis of ADD-ABDuctor spasmodic dysphonia, vocal tremor and ventricular dysphonia by auditory and phonoscopic observations. In: Clemente M, ed. Voice Update, International Congress Series. The Hague, Netherlands: Elsevier, 1997.

Shipp T, Izdebski K, Morrisey P. Physiologic stages of vocal reaction times. J Speech Hear Res. 1984;27:14. (Describes the cortical and mechanical muscular speeds with which humans process and execute sensory motor processes to initiate phonation.) [PMID: 6330455]