Vol. 11 •Issue 10 • Page 16
Allergy & Asthma
Vocal Cord Dysfunction: A Prime Suspect in Asthma Misdiagnosis
Asthma is like love. It’s hard to define, but you know it when it comes along. However, in the diagnosis of asthma as in matters of love, we’re sometimes mistaken. Because of that very real possibility, the first question running through practitioners’ minds when seeing a severe case of asthma should be: “Is this the correct diagnosis?”
A prime suspect for the cause of asthma misdiagnosis is vocal cord dysfunction (VCD), a condition in which the vocal cords adduct during inspiration, producing possible airflow obstruction and wheezing that can mimic asthma. As a result, these patients almost invariably are misdiagnosed as having asthma and often undergo inappropriate medical regimens without any benefit.1
A typical patient with VCD is a young woman in her second or third decade of life. There appears to be an increased prevalence of psychological dysfunction in these patients, with one-third of them having a history of diagnosed psychiatric illness. Health care workers also are overrepresented.2 No explanations exist for the increased prevalence in these populations.
But VCD can affect a wide range of people. It’s been described in patients as young as 4 months of age and as old as 73 years. Teenagers with VCD tend to be overachievers, either academically or athletically, though the relationship remains unclear.
VCD presents in two common ways. The first is that of stridor, which is suggestive of upper airway obstruction. The second is that of asthma.
Patients presenting with stridor may be in severe respiratory distress and so can be quite frightening when seen acutely in an emergency department. Almost a third of patients with VCD have been intubated or had a tracheotomy performed in the past. For the group that presents with asthma, they have symptomatology and physical exams that are similar to that of patients with asthma.
Because the airways are excellent conductors of sound, it’s difficult and unreliable to distinguish VCD from asthma based totally on the physical exam. Triggers for VCD attacks — exercise, viruses and irritants, such as cigarette smoke and often strong smells — are similar to that for an asthma attack. Additionally, a number of patients, especially teenagers, tend to have exercise-induced VCD, which has been called a cause of athletes making mistakes or “choking” at key moments in a game.3
The key to diagnosis is looking for red flags, symptoms that aren’t consistent with what you would expect in a patient with asthma. In the patient’s history, for instance, this would include a lack of alleviation of asthma-like symptoms with albuterol or steroids. At the National Jewish Medical and Research Center, Denver, I had patients who, despite taking high doses of inhaled steroids and averaging more than 20 milligrams a day of prednisone, couldn’t find relief from their symptoms.
Because the vast majority of patients with VCD have normal arterial oxygen levels and normal arterial-alveolar oxygen difference, a red flag in the emergency room may be a patient presenting with an apparent severe asthma attack but having a normal or high oxygen level.
Another red flag can be seen on X-rays. While an acute asthma case typically shows hyperinflation and peribronchial thickening on a chest X-ray, a VCD patient’s is usually normal. In terms of blood chemistries, most patients with acute asthma have eosinophilia, which isn’t present in patients with VCD alone.
If pulmonary function tests are performed during an acute VCD attack, they will usually fail to show any evidence of expiratory airflow obstruction. Instead, evidence of thoracic obstruction will be present as a flattening of the inspiratory limb of a flow-volume loop. VCD patients also often have difficulty in performing spirometry even in times when they aren’t having an attack.
Achieving a correct diagnosis of VCD is dependent on direct visualization of the vocal cords, usually with a flexible fiberoptic rhinoscope. In normal patients, the vocal cords open widely during inspiration and may close somewhat during expiration. In contrast, with inspiration in VCD cases, there’s classically closure of the anterior two-thirds of the vocal cords, with a posterior chink remaining open.
When the patient is asymptomatic, though, the vocal cord motion may appear normal. In order to provoke the abnormal inspiratory closure of the vocal cord, it may be necessary to use an exercise challenge or stimulants, such as methacholine or histamine. Why these stimulants produce abnormal vocal cord motion remains unclear.
PREVALENCE AND THERAPY
The prevalence of VCD in the general population also is unknown. However, at referral centers, such as National Jewish, VCD has been found in almost one-third of the patients who were referred for severe asthma. Specifically, 13.6 percent of patients had VCD without any evidence for asthma, and an additional 16.7 percent had both VCD and asthma.
Increasing evidence suggests that VCD may not be an uncommon syndrome. In a study of patients who had recurrent episodes of asthma symptoms in association with normal spirometry, more than a quarter of them were found to have decreased inspiratory flows, but not the expiratory flows with histamine challenges indicative of VCD.4 In a small study conducted at the emergency room of the Baylor College of Medicine, Houston, two out of 15 patients seen for acute asthma were found to have VCD alone, and an additional four had VCD with asthma.5
As for VCD therapy, it begins with immediately stopping unnecessary medications and treating any psychological factors, as there is a high incidence of psychological disease. Speech therapy often is useful in teaching relaxed throat breathing.
In acute attacks, heliox can be useful because airflow in the glox and large airways is density dependent. Using a low-density gas such as helium allows for improved flows and decreases the sense of dyspnea and may break the oncoming attack. Usually the mixture for heliox is 60 percent to 80 percent helium with the remainder being oxygen.
Lastly, it’s important to note that almost all patients with VCD have some irritant to the vocal cords, which most commonly is gastroesophageal reflux or postnasal drip. Therefore, treatment of these disorders is an important part of the patient’s therapy.
VCD always should be kept in mind when treating a severe asthmatic patient who isn’t responding appropriately to medical therapy.
1. Christopher KL, Wood RP, Eckert RC, et al. Vocal cord dysfunction presenting as asthma. N Engl J of Med. 1983;308:1566-70.
2. Newman KB, Mason U, Schmaling K. Clinical features of vocal cord dysfunction. Am J Respir Crit Care Med. 1995;152:1382-86.
3. McFadden ER, Zawadski DK. Vocal cord dysfunction masquerading as exercise-induced asthma: a physiological cause for “choking” during athletic activities. Am J Respir Crit Care Med. 1996;153(3):942-47.
4. Bucca C, Rolla G, Brussino L, DeRose V, Bugiani M. Are asthma-like symptoms due to bronchial or extrathoracic airway dysfunction. Lancet. 1995;.346:791-95.
5. Bandi V, Wolley M, Hanania N, Zimmerman J, Guntupalli K. Vocal cord dysfunction in patients presenting with asthma exacerbation. Chest. 1996;110(4):84S.
Dr. Newman is senior director, clinical development and medical affairs, Forest Laboratories Inc., New York City.