Benign Vocal Pathologies

Our 22nd episode focuses on a puzzling clinical entity for many: Benign Vocal Cord Pathologies. Tune in to learn all about the unique ways voice pathology can manifest!

Show Notes

Introduction 

Welcome to The Oto Approach, a podcast created by medical students for medical students, to teach you about all things otolaryngology. I'm your host Yousef, and today we're going to talk about Vocal Pathologies. Tag along for a discussion about this common presentation.

Hoarseness, also known as Dysphonia, refers to the impaired ability to produce voice. [2] The American Speech-Language-Hearing Association characterizes voice disorders as voice quality, pitch, and volume that is different or inappropriate for an individual’s age, gender, cultural background, or geographic location. [1]

Anatomy

Let’s first review the relevant anatomy. Voice production results from vibrations of the “vocal folds”, also known as “vocal cords”, which are located in the larynx, also known as the “voice box”. The larynx is 4-5cm in length and width. A larger larynx correlates with a deeper voice. [13] Therefore, the larynx is commonly larger in men compared to women, and larger in adults compared to children. [13] 

The larynx contains four folds of fibroelastic tissue. [13] These folds are inserted anteriorly into the thyroid cartilage and posteriorly into arytenoid cartilage. [13] The two superior folds are thin and have no muscular element, these are referred to as the vestibular folds or the false vocal folds. [13] The two inferior folds are wider and covered with a muscular fascicle, they are referred to as the true vocal folds. [13] Only the true vocal folds can produce phonation. This is because the space between these folds is smaller which allows them to contact each other, producing sound. [13] The region formed between the four vocal folds is referred to as the glottis.  

The true vocal folds have three functional layers: 1. the Cover, made of the epithelium and superficial lamina propria, 2. the Transition, made of the intermediate and deep lamina propria or vocal ligament, and 3. the thyroarytenoid muscle. The superficial lamina propria in the cover is what allows the epithelium to decouple from the deeper layers for vibration. [27] The thickness of the cover layer varies according to several factors such as sex, age, temperature, hydration, and pathological state. [27] Changes in the thickness of the cover layer alter vibration of the vocal folds such that thicker cover layers result in a lower fundamental frequency of voice. [27]

The process of producing voiced sound is referred to as phonation. Phonation has five requirements: 1. Adequate power (breath), 2. Ability to approximate the vocal folds, 3. Favorable vibratory properties, 4. Factorable vocal fold shape, and 5. Control of vocal fold length and tension. [14] Voice production is determined by the length and position of the vocal folds, their vibratory capacity, and the expiratory force acting to move them. [14] Movement of the true vocal folds occurs through the coordination of several pairs of intrinsic laryngeal muscles, including the cricothyroid, thyroarytenoid, (lateral and posterior) cricoarytenoid, and (transverse and oblique) arytenoids. The names of these muscles correspond to their origin and insertion. The cricothyroid muscle elongates the vocal folds, increasing the pitch of phonation. [13] The thyroarytenoid muscles serve as an adductor of the vocal folds, relax the vocal folds, resulting in a softer voice. [13] The posterior cricoarytenoid muscle abducts or opens the vocal folds, it is the sole abductor of the vocal fold, while the lateral cricoarytenoid muscles adduct or close the vocal folds. [13] The transverse and oblique arytenoid muscles also adduct the vocal folds. [25] The cricothyroid muscle is innervated by the external branch of the superior laryngeal nerve while the remaining intrinsic laryngeal muscles are innervated by the recurrent laryngeal nerve. [26]

The myoelastic-aerodynamic theory of voice production states that when the true vocal folds are adducted by the lateral cricoarytenoid muscles, the subglottic pressure increases until the vocal folds vibrate. [14] This closes the glottis from inferiorly to superiorly. When the posterior cricoarytenoid muscles abduct the vocal folds, the glottis opens from an inferior to superior direction. [14]

As mentioned, the other two components of phonation are articulation and resonation. Articulation is the physical act of clear vocal expression. [14] Articulation is determined by the vocal tract articulators, being the tongue, soft palate, lips, and jaw musculature and it acts as another process that modifies voice sound. [14] Resonation is the amplification and modification of sound by vocal tract resonators, including the throat, oral cavity, nasal cavity and the nasopharynx. [14] Resonation involves a balance between oral and nasal speech which is determined by the velopharyngeal musculature valving which consists of a muscular valve extending from the posterior hard palate to the posterior pharyngeal wall. [15] Resonators and articulators are very important aspects of voice physiology because they are what make each of our voices unique and recognizable.

Prevalence

Voice disorders are one of the most common speech and language pathologies. Roughly 10% of the general population and 50% of vocal professionals will present with a voice disorder. [16] However, less than 1% of people with dysphonia actually seek out treatment. [1] Of those who do seek treatment, the prevalence of voice disorders has been shown to vary by sex, age, and occupation. The prevalence is higher in the adult population, with voice disorders affecting roughly 3-9% of the adult population and 6% of children under the age of 146. In the adult population, voice disorders are 1.5X more common in females [9, 16] whereas in paediatrics the prevalence is higher in males.

Etiology

The common classification for voice disorders is divided into two general categories, organic dysphonia and functional dysphonia. Functional dysphonia refers to dysphonia caused by improper use of the vocal mechanism that cannot be explained by anatomical pathology. [1,2] It is subdivided into psychogenic dysphonia, vocal fold misuse, and idiopathic vocal fold dysfunction. [2] Dysphonia is classified as organic when there is an anatomic pathology to explain the voice dysfunction. Organic dysphonia consists of an extensive differential diagnosis. These diagnoses can be divided into two general categories: structural and neurogenic. 

Common risk factors for developing dysphonia include working long hours, working in professions that have high voice demands, smoking, frequent exposure to air conditioning, and inhaled pollutants such as dust and chalk. [16] In adults, the most common etiologies of dysphonia were functional dysphonia, accounting for 20.5%, followed by acid laryngitis at 12.5% and vocal polyps at 12%. [9, 16]  

In early childhood, dysphonia is commonly due to acute viral laryngitis. [16] The condition is usually self-limiting and rarely progresses to bacterial laryngotracheal bronchitis. [16] In children between the ages of 5-10, vocal nodules are the most common cause of vocal fold disorders, accounting for 16.9% of all diagnoses. [10,16] These lesions are the result of vocal fold overuse and are most common in male children. [16] They are treated with voice therapy. [16] The second most common cause of pediatric dysphonia is vocal cysts. These cysts can be mucosal or epidermal in nature. [16] Epidermal cysts are congenital and develop on the vocal ligament. [16] Laryngeal papillomatosis is another common etiology of dysphonia in children, which presents with progressive dysphonia and respiratory discomfort. [16] These lesions will always reoccur and are treated with repeated surgical removal. [16]

History: Signs and symptoms

While taking a history for suspected dysphonia, you should ask your patient about their occupation and daily voice use, their use of tobacco and alcohol, any prior laryngeal surgery or surgery involving intubation, and a history of acid reflux or difficulty breathing. [11]

We will take a look at the signs and symptoms of the three most common vocal fold pathologies: functional dysphonia, acid laryngitis, and vocal polyps. 

As we discussed, functional dysphonia is poor voice quality without any obvious anatomical, neurological, or other organic mechanism affecting the larynx. [17] Symptoms of Functional Dysphonia involve a voice that sounds rough, hoarse, raspy, or simply “gives out” when attempting to phonate. [19]

The second most common etiology of dysphonia is acid laryngitis. When working up a patient presenting with dysphonia, be sure to ask about a history of gastroesophageal reflux disease (GERD). Symptoms of acid laryngitis can be acute, chronic, or episodic and include frequent throat clearing, coughing, hoarseness of voice, and globus pharyngeus sensation. [20] Globus pharyngeus is the painless sensation of a lump or tightening of the throat. [21]  

Finally, vocal fold polyps are benign lesions that develop on the vocal folds and are characterised by thickening of the epithelium with a variable degree of inflammation in the underlying superficial lamina propria. Otolaryngologists often use laryngoscopy to visualize polyps in clinic. Vocal polyps interfere with normal vibrations of the vocal folds, thus leading to dysphonia. [23] Common symptoms of vocal fold polyps are hoarseness, breathiness, lower pitch speech, reduced vocal range, vocal fatigue, and throat dryness. [23] However, some patients will be asymptomatic and upon coming in for other reasons, will have vocal polyps found incidentally upon physical exam. [23]  

Let’s briefly discuss the red flags that should lower your threshold to refer a patient with hoarseness to otolaryngology. One or more of the following points along with hoarseness should heighten your suspicion for a more sinister presentation: history of smoking, especially over 10-pack-years, enlarged cervical lymph nodes, progression of hoarseness without fluctuation, referred otalgia or ear pain, dysphagia or aspiration, hemoptysis, stridor or dyspnea, unexpected weight loss, or excessive alcohol consumption. [28] 

Physical Exam and Diagnosis

Now that we have discussed some of the signs and symptoms that can help clue you into a voice pathology differential, we will discuss tools used by practitioners to diagnose dysphonia.. A thorough history and physical examination should be conducted. There are a variety of diagnostic tools an otolaryngologist may use when working with a patient presenting with dysphonia. These tools include nasolaryngoscopy for visualization and videostroboscopy for mucosal wave abnormalities. [2] There is no substitute for a complete head and neck exam. A thorough step-wise approach to physical examination of the head and neck is essential to ensure that important findings have not been missed. A detailed description of the head and neck examination along with videos can be found in the Bate’s Guide to Complete Physical Examination. 

On visualisation of the oral cavity with flexible laryngoscopy, signs of acute inflammation such as mucosal erythema and adhesion of purulent mucous should be noted. [11] A careful inspection of the vocal folds should be done, which includes any erythema, nodules, ulcerations, as well as the ability of the vocal folds to fully abduct and adduct; to make the vocal folds abduct, instruct the patient breath in, and to make the vocal folds adduct, instruct the patient to say “eee.”

Ancillary tests to support a diagnosis of dysphonia include acoustic analysis, speech aerodynamic studies, laryngeal electromyography, computed tomography, and magnetic resonance imaging. [2] A maximum phonation time (MPT) test may also be used in working up a patient presenting with dysphonia. MPT measures the maximum amount of time a patient can maintain phonation of a vowel sound, often pronouncing the letter “a”.[12]

One helpful evaluation system is the GRBAS scale. This is an auditory perceptual evaluation system that has been created to assess voice quality in patients with dysphonia. [11] This system considers six components of voice: the grade, roughness, breathiness, asthenia, strain, and instability. This scale ranks these qualities from zero to three where 0 is normal, 1 is a small degree of change in quality, 2 is a medium degree, and 3 is a high degree. [11] Other possible diagnostic tests employed in the work up of vocal fold pathology include voice pitch and strength tests, aerodynamic tests, and acoustic analysis tests. [11] 

The exact diagnostic criteria of vocal fold pathologies is outside the scope of this podcast. However, a thorough history and physical, in combination with the aforementioned diagnostic tools may lead you to one of many differential diagnoses for voice dysfunction. 

Treatment

The final topic of this episode will cover treatment options for dysphonia, which depends on the specific etiology. One of the  important forms of treatment is vocal rest, as voice use disturbs the healing process, ultimately leading to more severe dysphonia and longer recovery time. [25] It is also important to remind your patients to stay hydrated throughout the recovery process. Unfortunately, medical treatment rarely resolves symptoms. Thus, surgical treatment and voice therapy are often warranted. [2] Treatment of functional dysphonia will commonly involve speech language therapy, behavioural therapy, psychotherapy, and in some cases, hypnosis. [2]

The first line treatment of vocal polyps and lesions involves behavioural measures such as voice therapy, where patients can be taught to properly project their voice in order to avoid belting or straining, which will minimize the effects of the lesion. [24] Voice therapy has been shown to provide a significant perceptual improvement in speech but is unlikely to resolve the lesion. [24] After conservative treatment has been exhausted, microsurgery to remove vocal fold lesions may be warranted. [24] 

For acid laryngitis, treatment is often supportive and dependant on the severity of laryngeal inflammation. [25] Steam inhalation and avoidance of irritants such as tobacco smoke and alcohol aid the treatment of acid laryngitis. [25] Dietary modifications such as avoidance of late meals, reducing intake of caffeine, spicy and fatty foods, chocolate, and peppermint is reccomended. [25] Also, liquid alginate preparations have been shown to be effective in treatment of  symptoms and signs of acid and non-acid reflux. [30] Furthermore, frequent and adequate hydration is encouraged. Medications that reduce acid reflux such as H2 receptor blockers and proton-pump inhibitors may be warranted if lifestyle modifications are insufficient, however, routine antibiotics and steroid medications are not recommended. [25] 

For patients who are at risk of vocal pathologies, based on their lifestyle choices, should be educated on prevention of dysphonia, which includes remaining adequately hydrated, maintaining a humid living environment, avoiding smoking and alcohol, and allowing for vocal rest between periods of voice strain.

Clinical Pearls

Both nodules and polyps can be caused by different forms of trauma which include singing (especially in career singers), screaming, cheerleading, and excessive speaking. [29] Further, smoking, alcohol use, sinusitis, and allergies can contribute to both nodules and polyps. [29] Vocal nodules are growths that occur on the midpoint of the vocal folds that often resemble callouses under microscope and are associated with abnormal blood vessels. [29] Vocal nodules are, by definition,bilateral and occur more frequently in women between the ages of twenty and fifty. [29] Although they vary, vocal polyps are often larger than vocal nodules and resemble blisters as opposed to callouses. [29] A classic differentiating factor is that vocal polyps can occur on one, or both vocal folds, whereas vocal nodules are bilateral. Polyps are more vascularized than nodules and, hence, can appear more red upon examination. [29] Of note, a single event of voice misuse such as yelling at a sporting event or concert could form a polyp. [29] Although quite similar, vocal nodules and polyps differ in subtle ways. A complete physical examination and a keen eye is helpful in picking out the difference! 

Thank you to Gizelle Francis and Yousef Omar for development of this script.

We would like to extend our sincerest thanks to the Saint John Regional Hospital Department of Surgery within the Horizon Health Network for their generous support. 

Thank you so much for listening to our podcast! We hope you’ll tune in to our next episode! Please head to our website at www.theotoapproach.com for our show notes, and to sign up for our newsletter to stay up to date with our latest episodes.

References

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