Continuing Education Activity

Functional voice disorders (FVD) are caused by insufficient or improper use of the phonation apparatus without either anatomical or neurological abnormalities. The most common FVDs include vocal fatigue, muscle tension dysphonia, diplophonia, and ventricular phonation. This activity reviews functional voice disorders by discussing their etiology, epidemiology, and pathophysiology, as well as the role of the interprofessional team in the evaluation and treatment of patients with functional voice disorders.

Objectives:

• Explain the impact that functional voice disorders can have on patients' quality of life.
• Identify the etiology of functional voice disorders.
• Outline the evaluation of functional voice disorders.
• Review the management options available for functional voice disorders.

Introduction

Voice is a critical medium of human communication and social interaction; therefore, partial or total loss of voice may have profound implications for quality of life and safety. Problems with the voice can also lead to severe functional and occupational impairment for professionals who rely heavily on vocalization, such as singers, teachers, lawyers, actors, media personalities, and myriad others. Most people, in fact, would be affected significantly by a major impairment in their speech. 

The human voice is produced by the passage of exhaled air from the lungs over the vibrating vocal folds; this requires synchronization of diaphragmatic and laryngeal function as well as the shaping of the sound by the tongue, cheeks, and lips. In order to preserve optimal function, it is best to avoid activities that can strain the vocal folds, such as prolonged or excessively loud screaming or shouting. Organic abnormalities of the anatomy, such as nodules, scars, cartilage subluxations, and nerve injuries, are likely to cause voice anomalies. A functional voice disorder should be suspected when vocal quality is compromised without any identifiable anatomical or neurological factors.

Voice disorders can be classified as follows:

• Structural organic voice disorders result from physical changes in the laryngeal anatomy, such as edema, vocal nodules, and presbylarynx.
• Neurogenic organic voice disorders include vocal tremors, spasmodic dysphonia, paralysis of the vocal folds, etc. These problems relate to abnormalities of central or peripheral nervous system innervation to the larynx.
• Functional voice disorders (FVD) are caused by insufficient or improper use of the larynx and diaphragm without any identifiable physical structural abnormality or neurological dysfunction. These disorders often have a noticeable adverse impact on social and occupational function. Although there is a vast amount of literature relating to the topic, there is no consensus regarding foundational concepts or methodology of evaluation of voice disorders, as very few authors have rigorously investigated the most effective vocal assessment or video laryngoscopic examination techniques required to produce a consistent and definitive diagnosis of FVD. The most common FVDs are vocal fatigue, muscle tension dysphonia or aphonia, diplophonia, and ventricular phonation.[1][2] Vocal fatigue is caused by overuse of the voice and resultant tiring of the laryngeal musculature. Muscle tension dysphonia or aphonia is caused by hypertonicity of the laryngeal musculature, which in turn limits the vocal folds' ability to abduct and adduct with coordination and rapidity. Diplophonia is the phenomenon in which two separate fundamental frequencies are being produced during phonation, which may result from waves of different phases passing through the vocal fold mucosal surface or from different oscillatory frequencies occurring in the left and right vocal folds. Lastly, ventricular phonation occurs when the false vocal folds, also known as the ventricular folds, become the primary vibratory surfaces of the larynx due to stiffness of the true vocal folds or maladaptive voicing habits. All of these phenomena tend to present with hoarseness.

Etiology

Prolonged and frequent vocal abuse is a significant risk for developing anatomical lesions of the larynx, such as nodules (also known as "singer's nodes") and hematomas and their sequelae. Functional voice disorders also result from vocal misuse or abuse as well as from behavioral health pathology. FVDs may be more easily recognized than other psychosomatic disorders because the clinician can visualize the laryngeal structure and function using a mirror or a flexible fiberoptic endoscopy, and therefore rule out organic disease. Both organic and functional voice disorders can affect multiple vocal parameters, including quality, pitch, and loudness, which can all be very problematic for patients.

Common causes of functional voice disorders include:

• Phonotrauma, which is caused by misuse, abuse, and overuse of the voice (yelling, screaming, excessive throat-clearing, and talking with increased loudness).
• Psychogenic aphonia and dysphonia, which are most commonly encountered in patients with underlying behavioral health issues, such as anxiety, depression, and conversion disorder. Associated symptoms may include blindness, paralysis, and other apparent neurological symptoms.[3]

Epidemiology

Voice disorders have an estimated prevalence of 20 million (0.98%) in the United States.[4][5] Vocal abuse is the most common etiology among adults and children. Among adults, teachers represent the most at-risk population.[6][7][8] A 2008 case-control study was conducted with 905 teachers in Spain in order to calculate the prevalence of voice disorders among educators and determine the associated risk factors.[7] All the teachers were given a questionnaire to fill out, followed by a complete head and neck examination and videolaryngostroboscopy. The study concluded that 57% of the teachers suffered from voice disorders, including vocal overstrain, which was the most prevalent (18%). Another study compared voice disorders between daycare center teachers and nursing staff, demonstrating a higher risk of voice disorders in teachers relative to the nursing staff.[8] The prevalence of voice disorders among teachers was 11.6%, but it was only 7.5% in the nonteacher population. Teachers also reported current and past voice disorder symptoms in higher numbers compared to nonteachers.

Pathophysiology

Thus far, no consensus on nomenclature for specific voice disorder pathology has been adopted in the literature.[9] That said, most voice pathologies appear to result from aberrant vocal use, particularly poor vocal technique (straining the voice, inadequate hydration, failing to rest when necessary), poor oral care and hygiene, repeated laryngeal infection, and excessive throat clearing.[10] Patients with chronic vocal problems frequently complain of a "lump in the throat," technically known as globus hystericus, which often indicates laryngopharyngeal reflux that may present even in the absence of noticeable heartburn.[11]

History and Physical

Taking a patient history to help diagnose voice disorders requires determining the frequency, duration, and severity of symptoms as well as any exacerbating or alleviating factors. Environmental factors are important to elicit as well, and these may include low humidity, alcohol use, cigarette smoke, and other airborne particulates like dust or chemical agents. Achieving an understanding of a patient's vocal habits and needs is likewise crucial to developing a working diagnosis and an individualized treatment plan. Including an evaluation of the patient's medical, surgical, psychological, traumatic, and pharmaceutical history can also be very informative in many cases.

The physical examination should include a standard head and neck evaluation as well as palpation of the larynx and trachea and videostroboscopic evaluation of phonation.

Evaluation

A systematic and thorough evaluation of the laryngeal structures and the patient's voice is vital in order to determine an effective strategy for vocal therapy exercises. Clinical evaluation for dysphonic patients is carried out in three steps:

1. History Taking
2. Physical Evaluation
3. Examination

The history-taking involves ascertaining medical, surgical, psychological, or traumatic information that leads to diagnosing and tailoring treatment to the patient. Part of this process is the vocal evaluation, which requires understanding the anomaly and how it affects activities of daily life, such as professional commitments or personal communication. Listening to the pitch, volume, and quality of the voice will help the clinician determine the type of problem. Detailed vocal evaluation leads to a better understanding of the underlying pathology and, therefore, a more appropriate intervention.[12]

Physical examination includes a complete ear, nose, and throat examination after assessing voice quality, loudness, and range. The purpose of the assessment is to focus on nasal airway patency, pharyngeal function, and velopharyngeal competency. Some patients may need pulmonary function studies if they exhibit insufficient expiratory force or volume that leads to an alteration of the voice, compromising the normal pattern of synchronized respiration and phonation. Hearing evaluation may also be important, as hearing loss can influence a patient's perception of their own voice and therefore alter its production.

Laryngoscopy is the most important step in the diagnosis of vocal dysfunction. There are multiple methods of visualizing the larynx, including mirror laryngoscopy, flexible fiberoptic laryngoscopy, distal chip laryngoscopy, digital transoral laryngoscopy, and stroboscopy. Stroboscopy provides the greatest amount of information when evaluating the mucosal wave of the vocal cords.[13][14]

Due to the heterogeneity of functional voice disorders, assessment should also be evaluated for psychogenic and muscle tension pathologies. Psychogenic voice disorders and muscle tension voice disorders are treated by speech-language pathologists (SLPs) who use symptomatic behavioral voice therapy along with counseling and, potentially, psychotherapy.[15]

The presentation of functional voice disorders can take many forms (dysphonia, stuttering, or prosodic abnormalities) and may mimic organic disorders, such that diagnosis can be difficult. A thorough examination, correct diagnosis, and proper treatment are critical. Functional or psychogenic disorders and behavioral movement disorders can be challenging to differentiate based solely on observable speech and voice disturbances; many behavioral and neurological conditions can mimic symptoms of organic voice conditions.[1]

Treatment / Management

The first step in FVD management is determining the correct diagnosis, and treatment may require multiple modalities depending on the cause, type, and severity of the disorder. Most problems can be managed simply by identifying the etiology and modifying patient behavior to avoid it.

As a general rule, there are three primary treatment strategies:

1. Medical Treatment
2. Surgical Treatment
3. Voice Therapy

Speech-language pathologists employ a holistic approach to treatment, striving to balance respiration, phonation, and resonance instead of directly addressing the symptoms of voice problems. Multiple rehabilitative strategies, such as auditory masking, the accent method, conversation training therapy (CTT), Lax Vox speech therapy, expiratory muscle strength training, phonation resistance training, chant speech, and confidential voice are used to manage FVDs. Multiple facilitative techniques are leveraged by SLPs to restore a normal voice, depending on the type of voice disorder, while also trying to determine the underlying causality.[16] Correct positioning, relaxation, hydration, vocal functioning exercises, counseling, patient education, and behavioral modification may all play roles in achieving optimal outcomes. 

In some cases, vocal fold nodules are successfully treated with voice therapy alone. However, many other types of lesions (laryngeal webs, polyps, contact ulcers, and papilloma) require surgical management. Identification of the cause of the dysfunction is the key to a successful treatment. Voice therapy is the standard of care for many of the nearly 140 million people in the United States who suffer from voice disorders; unfortunately, current therapies are not always effective for a number of reasons: incorrect diagnosis, patient noncompliance, and severity of the pathology being chief among them.

Differential Diagnosis

The following clinical entities should be considered potential diagnoses in patients with dysphonia:[17][18]

• Somatoform disorder
• Conversion disorder
• Abuse
• Anxiety disorder
• Depression
• Munchausen syndrome
• Malingering
• Allergic and environmental asthma
• Anaphylaxis
• Bilateral vocal fold paralysis
• Exercise-induced asthma
• Foreign body obstruction
• Laryngeal abnormalities (e.g., neoplasm, polyps, cyst)

Prognosis

Good prognostic indicators include acute onset of symptoms, absence of underlying organic pathology, ability to eliminate the trigger (particularly if it is a life stressor), male gender, young age, and good general health status. Poor prognostic indicators include personality disorders, poor perception of the patient's own wellbeing, associated motor symptoms, and psychogenic nonepileptic seizures.

To optimize outcomes, it is essential to arrive at the correct diagnosis through thorough evaluation and careful consideration. Unless the treatment is tailored to the underlying pathology, the results will not be satisfactory for either the patient or the clinician; voice therapy, for example, will not significantly help a patient with a glottic mass that requires surgical excision. A multidisciplinary approach, typically involving an otorhinolaryngologist or fellowship-trained laryngologist and an SLP, is likely to be most effective at alleviating symptoms and improving quality of life.[19]

Complications

The primary complications associated with FVD relate to the barriers to communication and social isolation that ineffective phonation may produce. When speaking is difficult or results in ineffective communication, frustration, low self-esteem, anxiety, and depression may result. In psychogenic FVD, the longer the FVD exists, the worse the underlying behavioral health problem may become, which can further exacerbate the FVD.[20]

Deterrence and Patient Education

The mainstay of treatment of functional voice disorders is vocal rehabilitation, which is tailored according to patient presentation and prognosis. The most significant drawback to this approach is the inherent difficulty in maintaining patient compliance for regular follow-up and long-term self-directed treatment. Outcomes are improved when barriers to compliance are identified and addressed, often through the use of patient-centered questionnaires. Additionally, patient motivation can be improved with a thorough understanding of the diagnosis and etiopathogenesis of the condition, which facilitates insight into the factors that contribute to the problem.[21]

Enhancing Healthcare Team Outcomes

Delivering healthcare via multidisciplinary teams reduces the number of medical errors that occur and improves patient safety. An interprofessional team that provides a holistic and integrated approach to patient care will ultimately optimize outcomes for FVD patients. Patients with voice disorders may require a treatment team consisting of an otorhinolaryngologist or laryngologist, psychologist or psychiatrist, SLP, and other health professionals. Multidisciplinary collaboration plays a vital role in providing long-term patient-centered care that improves individual health outcomes and enhances the chances of rapid functional recovery.[22]