Vocal Cord Dysfunction

Background

Vocal cord dysfunction (VCD), also commonly known as paradoxical vocal fold motion, can be characterized as an abnormal adduction of the vocal cords during the respiratory cycle (especially during the inspiratory phase) that produces airflow obstruction at the level of the larynx.^{[1, 2, 3]}

The larynx receives very extensive sensory and motor innervation. With repeated stimulation and excitation by noxious intrinsic and extrinsic irritants, these nerve fibers may become hyperexcitable and hyperresponsive. Consequently, the threshold for activation of the reflex responsible for vocal cords closure is lowered. The underlying pathophysiology of VCD involves a hyperfunctional and inappropriate laryngeal closure reflex.^{[66, 67]}

VCD frequently mimics persistent asthma and is often treated with high-dose inhaled or systemic corticosteroids, bronchodilators, multiple emergency department visits, hospitalizations, and, in some cases, tracheostomies and intubation.^{[2, 4, 5, 6]}

The patients considered here have problems associated with abnormal vocal cord movement without an organic basis. Flow-volume loops obtained during symptomatic periods of wheezing show a limitation of inspiratory flow suggestive of variable extrathoracic obstruction (inspiratory loop flattening). Paradoxical vocal cord motion can be confirmed on laryngoscopy performed when patients are symptomatic.

The clinical history provides limited opportunity to distinguish between patients with VCD and patients with asthma because both groups present with symptoms of wheezing, cough, and dyspnea.^{[7, 8]} The localization of airflow obstruction to the laryngeal area is an important clinical discriminatory feature in patients with VCD.

Another clinical clue may be that patients with VCD often seem to have refractory asthma with poor response to beta-agonists or inhaled corticosteroids.^{[9, 10]} They do not usually report nocturnal awakening due to breathlessness.

Objectively, the data reveal absence of hypoxemia in this subset as compared to compromised persons with asthma.^[10]

The hallmark of diagnosis is noted on direct rhinolaryngoscopy; a glottic chink is present along the posterior portion of the vocal cords, while the anterior portion of the vocal cords is adducted.

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Pathophysiology

During the normal respiratory cycle, the vocal cords partially abduct with inhalation and partially adduct with end-exhalation. This phasic vocal cord movement is physiologic, and it allows the unimpeded movement of air inward to the lungs and outward to the atmosphere while maintaining the alveolar patency of the lungs by providing positive airway pressure during expiration (ie, positive end-expiratory pressure [PEEP]).

The larynx, therefore, serves as an upper airway valve to help keep the lungs expanded. For this function, the larynx is richly innervated, and its size is regulated by the activation of striated muscles that are under voluntary and reflexive control. Both laryngeal and respiratory motor neurons influence glottic size, and they, in turn, may be influenced by vagal reflex activity arising from pulmonary and laryngeal receptors.

The mechanisms that cause glottic chink narrowing or intermittent closing during inspiration independent of any changes in lower airway caliber are unknown. In affected patients, the integrated function of the vocal cords ceases episodically, leading to acute intermittent episodes of functional airway obstruction. The clinical signs and symptoms resemble those observed in disorders such as vocal cord paralysis, asthma, epiglottitis, laryngospasm, and angioedema secondary to anaphylaxis.

Recent case reports have described other causes of VCD, such as an inlet patch of heterotopic gastric mucosa in the upper esophagus^[11] and exposure to agents such as glutaraldehyde and chlorine inhalation by swimmers or divers.

VCD appears to be part of the spectrum of airway disorders caused by occupational exposures, including irritant exposures and psychological stressors, at the World Trade Center disaster. A recent study evaluating the role of formal psychological testing in patients with paradoxical vocal cord dysfunction found a pattern consistent with conversion disorder in some patients; however, a subset of patients did not appear to be associated with psychopathology.^[12]

To summarize, the exact cause of this condition is not clearly evident and may be multifactorial.^{[10, 13]} A hypothesis is that mediation of the vagus nerve may alter the laryngeal tone and lower the threshold for stimuli to produce vocal cord spasm or to precipitate the abnormal adduction of vocal cords. Recent literature suggests a greater emphasis on organic causes such as gastroesophageal reflux and laryngopharyngeal reflux since the laryngopharynx is highly sensitive to gastric acid irritation.

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Epidemiology

Frequency

United States

This condition is observed in up to 10% of patients at referral centers seeking evaluation of asthma that is unresponsive to aggressive therapy. The literature reveals a high incidence of VCD in persons with psychiatric conditions (eg, depression, obsessive-compulsive disorder, borderline personality disorder, neuroses induced by childhood sexual abuse),^{[1, 14]} persons with an increased body mass index^[6] and medical personnel. VCD may complicate true asthma in a small number of patients.

Mortality/Morbidity

Mortality rates are unknown, but morbidity is often significant from years of corticosteroid use, resulting in iatrogenic Cushing-like syndrome, bone density loss, and growth suppression in the pediatric population.^[10]

Misdiagnosis of VCD as asthma may lead to significant morbidity and increased costs, and misuse of measures of asthma control may be contributing to these findings.^[72]

Sex

This condition is predominantly observed in females.^[12] The authors' review of the published literature indicates a female-to-male ratio of approximately 3:1.

Age

This condition predominates in people aged 20-40 years, but it can occur in people aged 6-83 years. Recent literature suggests an increase of this condition in children and adolescents.

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History

See the list below:

• Wheezing
• Cough
• A feeling of tightness in the throat
• Hoarseness and voice change
• Stridor
• Shortness of breath
• Dyspnea on exertion
• Inspiratory difficulty
• Sudden episodes of shortness of breath
• Unresponsiveness to bronchodilators and corticosteroids

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Physical

See the list below:

• Laryngeal auscultation may reveal harsh stridulous sounds during symptoms.
• Wheezing may be heard in the chest (transmitted from the upper airway).

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Causes

Problems associated with vocal cord dysfunction (VCD) include the following:

• Gastroesophageal reflux disease, laryngopharyngeal reflux
• Upper airway inflammation due to allergies (rhinitis), sinusitis, or recurrent viral infections
• Strenuous exercise^{[15, 16, 17, 18, 19]}
• Occupational or other exposure to irritant fumes^{[20, 9, 3]}
• Environmental allergens and/or pollutants
• Psychogenic causes (eg, severe emotional stress)

Bodily sensations such as throat tightening, wheeze, and cough can feed into a cycle of panic that exacerbates symptoms.^[68]

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Laboratory Studies

Laboratory studies may be indicated to exclude other diagnoses.

Eosinophil count

Eosinophilia may suggest the diagnosis of asthma if levels are greater than 5%, but absence of this sign does not clearly exclude the diagnosis, especially if the patient has been frequently treated with oral corticosteroids.

Elevated eosinophil counts may also be observed in skin diseases such as atopic dermatitis and in clinical entities such as pulmonary infiltrates with eosinophilia, allergic bronchopulmonary aspergillosis (ABPA), Churg-Strauss syndrome, and parasitic diseases.

Vocal cord dysfunction (VCD), itself, is not associated with an elevated blood eosinophil count.

Serum immunoglobulin E (IgE) assay

Elevated serum IgE is observed in allergic individuals, but it is not specific for asthma.

This elevation may be observed in other syndromes such as ABPA and Churg-Strauss syndrome. Its presence may indicate a concomitant diagnosis of asthma even though its absence is not exclusionary.

VCD by itself is not associated with an elevated serum IgE level.

Arterial blood gases (ABG)

ABG findings reveal an alveolar-arterial gradient (ie, the alveolar-arterial oxygen difference), which is a measure of oxygen delivery from the lungs to blood, that is usually within reference ranges in the subset of patients with VCD.

In patients with acute asthma, ABG findings may be abnormal, indicative of hypoxemia.

C1 inhibitor and C4 levels

These levels should be evaluated to exclude hereditary angioedema.

This is especially useful if episodes have been prolonged (1-4 d) or if angioedema in other areas or unexplained abdominal pain has occurred in or out of association with episodes of dyspnea.

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Imaging Studies

Chest radiography

Radiographic findings are usually normal, or radiographs may show hyperinflation in asthmatic individuals.

Chest radiography may be used to evaluate other pulmonary diseases or structural laryngeal and cardiac abnormalities that may explain or support the patient's respiratory symptoms.

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Other Tests

Pulmonary function test

Spirometric testing supports the diagnosis of VCD in symptomatic individuals.^[23] This study is used to identify individuals with asthma or other pulmonary abnormalities, including upper airway obstruction. In patients without coexisting asthma, spirometric findings are usually within the reference range during an episode.^{[10, 24]} If flows are decreased during an episode, forced vital capacity (FVC) decreases in tandem with forced expiratory volume in the first second (FEV₁), which is not consistent with classic airflow limitation.

Flow-volume loops are the most useful tool in discriminating between VCD and asthma. Flow-volume loops typically demonstrate inspiratory loop flattening, ie, an inspiratory flow decrease during symptomatic periods suggestive of VCD. In addition, during VCD symptoms, an abrupt drop and rise in the expiratory flow volume loop may be observed in the absence of coughing. See the image below.

View Image

Flow volume loops.

Results of routine measurement of airflow obstruction (ie, FEV₁, peak expiratory flow rate) can be within reference ranges in VCD if the vocal cords close only on inspiration. If vocal cord closure occurs during both inspiration and expiration, FEV₁ can decrease along with the decrease in FVC, making the FEV₁/FVC ratio within the reference range. This distinguishes isolated VCD from VCD concomitant with asthma, in which the FEV₁ is proportionately decreased more than the FVC, representing airflow limitation.

The Pittsburgh Vocal Cord Dysfunction Index

In 2014, researchers developed a scoring index to help distinguish VCD from asthma. Researchers identified symptoms of throat tightness and dysphonia, the absence of wheezing, and the presence of odors as a symptom trigger as key features of VCD that distinguish it from asthma. The index showed good sensitivity (83%) and specificity (95%), and accurately diagnosed VCD in 77.8% of patients with laryngoscopy-proven VCD.^[25]

Methacholine provocation

A patient with VCD shows no bronchial hyperresponsiveness on methacholine challenge unless he or she has concomitant asthma.

This challenge is therefore most helpful in excluding the diagnosis of asthma. It may also be helpful in confirming that a patient with VCD has coexisting asthma.

Exercise provocation

In a patient in whom exercise or strenuous activity is a primary trigger, a graded exercise challenge on a bicycle ergometer or treadmill is helpful to establish a diagnosis.

Allergy skin testing

Perform skin tests to determine the existence of an allergic or environmental trigger or condition (eg, allergic rhinitis, allergic asthma).

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Procedures

Laryngoscopy

The criterion standard for the diagnosis of VCD is direct visualization of the paradoxical adduction of the true vocal cords during inspiration.^{[2, 26, 23]}

The classic textbook picture is the adduction of the anterior two thirds of the vocal cords with a posterior diamond-shaped chink through which air flows during the inspiratory phase.

View Image

Laryngoscopic views of the vocal cords.

If the patient is not symptomatic at the time of laryngoscopy or rhinoscopy, typical vocal cord changes may often be induced by exercise, hyperventilation, or a maximal forced expiratory effort followed by rapid inspiration. These maneuvers may increase the sensitivity of the test.^{[27, 28, 29]}

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Medical Care

A multidisciplinary approach with a physician and speech therapist and a psychiatrist, if needed, is usually effective.^[6]

Speech therapy

The mainstays of treatment for vocal cord dysfunction (VCD) involve teaching the patient vocal cord relaxation techniques and breathing exercises. These procedures have been very successful and are used concomitantly with psychological support in difficult cases.^{[2, 7, 10]}

The role of the speech therapist is to effectively teach and communicate a comprehensive speech therapy plan with appropriate breathing exercises. When a knowledgeable speech therapist is not available, the patient can be taught a breathing relaxation exercise with the use of a simple handout. See the image below.

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Relaxed throat breathing exercises.

Psychotherapy

The role of the psychiatrist is to implement cognitive behavior psychotherapy or general psychotherapy based upon evaluation of psychiatric and/or personality disorders.^{[2, 7, 14, 10]}

According to a systematic review of psychological interventions for patients with VCD, techniques such as psychotherapy, behavioral therapy, use of anti-anxiety and anti-depressant medications, and hypnotherapy in conjunction with breathing exercises may be effective treatment methods.^[30] One study shows psychotherapy directed towards somatoform and conversion disorders may increase efficacy when added to traditional treatment regimens.^[12]

Helium-oxygen therapy

This therapy consists of administration of a helium-oxygen mixture (heliox), which is less dense than air and thus reduces the turbulence in the airway during inspiration.

Heliox administration provides only a short-term benefit, but it may be very helpful in the emergent treatment of acute VCD.^{[31, 32]}

Anticholinergic agent

Inhaled ipratropium may be helpful treatment in patients with exercise-induced VCD. In a series of 6 patients receiving treatment with inhaled ipratropium, all patients reported improvement in symptoms.^{[28, 29]}

Botulinum toxin

An intralaryngeal injection of botulinum toxin relieves symptoms by blocking acetylcholine release at the motor end plate and creating a laryngeal muscle weakness, thus facilitating inspiratory and expiratory airflow.

Its use is considered experimental, and equivocal reports in the literature illustrate both effectiveness and lack of benefit.^{[33, 34]}

Panting

This maneuver causes the adducted vocal cords to relax, which increases the glottic aperture.

Topical lidocaine

This may be applied to the larynx.

The mechanism of action is to break the cycle of hyperactive glottal and supraglottal muscle contractions.^[35]

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Consultations

See the list below:

• Otolaryngologist
• Pulmonologist
• Allergist/immunologist
• Speech therapist
• Psychiatrist

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Diet

No diet restrictions are necessary.

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Medication Summary

No specific pharmacotherapy is indicated.

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Further Outpatient Care

Patients must receive further care to determine the response to patient education and speech therapy and to assess the need for referral for psychiatric care.

Many patients with vocal cord dysfunction (VCD) are treated inappropriately with corticosteroids if they present to an emergency department or acute care facility even after the diagnosis of VCD is established. A handout (see below) for the patient to show to new physicians may be helpful to avoid inappropriate treatment.

View Image

Vocal cord dysfunction treatment plan.

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Deterrence/Prevention

Deterrence and prevention can be achieved by adherence to speech therapy guidelines and exercises and by relaxation therapy or other measures to decrease anxiety.

Avoidance or control of precipitating factors when identified (eg, exercise, environmental or occupational irritants, rhinosinusitis, gastroesophageal reflux disease)^{[36, 37, 38]}

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Prognosis

Prognosis is good with effective response to speech therapy, which allows patients to take control of their disorder.

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Patient Education

Patient education ideally uses a multidisciplinary approach with involvement of a physician and speech therapist and, if needed, a psychiatrist.

The physician's role is to inform the patient of test findings, especially the absence of diseases such as asthma, and to explain the nature of the condition. Patients often express a positive reaction to the initial explanation, and such a reaction usually implies a good prognosis.

The following websites provide online patient educational sources:

• VCD Information from the National Jewish Medical and Research Center
• VCD: Paradoxical Vocal Cord Motion - A Thorough Review

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