Vocal cord dysfunction (VCD), also known as paradoxical vocal cord movement, is described as paroxysms of glottis obstruction due to true vocal cord adduction.1 Since VCD presents as a constellation of symptoms associated with dyspnea, it often is misdiagnosed as asthma.2 Vocal cord dysfunction often manifests as episodic dyspnea and wheezing, may occur with exercise, and may be minimally responsive to initial therapies. Flattened inspiratory curves may be noted on pulmonary function tests (PFTs), but direct laryngoscopy is the gold standard for diagnosis.3 A cohort of proven patients with VCD with a plateau in the inspiratory curve of PFTs also had a plateau on expiratory phase in 81% of cases.4
The differential diagnosis of patients presenting with upper airway symptoms is broad. It must include VCD, asthma, angioedema, laryngomalacia, vocal cord polyps, vocal cord tumors, and neurologic conditions such as brain stem compression or movement disorders. Essentially, all movement disorders of vocal cords must be considered, and organic causes of this movement disorder can be evaluated by visualization of the vocal cords. Triggers for VCD include exercise, airborne irritants, gastroesophageal reflux disease (GERD), allergic rhinitis, medications, and psychological conditions.5 Additionally, VCD can coexist with asthma, further complicating accurate diagnoses.6
Therapies are reported in case studies, but no large randomized controlled trials exist to evaluate current therapy options. Primary treatments of asthma therapy were largely ineffective, and ideal therapy includes a multidisciplinary approach, including speech therapy to optimize laryngeal control and treatment of all identified laryngeal irritants.6
The prevalence of VCD is unknown, with no prospective cohort studies completed to date and conflicting diagnostic criteria used in many case studies.7 A prevalence of 2.8% was noted in one particular cohort of 1,028 patients admitted to a rehabilitation center in a calendar year with the primary pulmonary diagnosis on admission.6 Females seemed to be affected at a higher ratio than were males, 2 to 3 females per 1 male diagnosis.7
In the military population, certain risk factors were noted in returning deployed members, including anxiety/high stress, exercise, and acute respiratory illnesses.8 In that particular cohort, 72% positive predictive value was noted for VCD if flattened inspiratory flow loops with negative methacholine challenge were present.
Diagnostic criteria are challenging, as symptoms such as dyspnea may be present acutely, last < 2 minutes, be self-limiting, and completely resolve outside of acute events. Stridor may be noted, primarily above the vocal cords, and less audible on chest auscultation.6 A goal of therapy, in addition to dedicated speech pathologist input, is optimizing comedical conditions, including GERD, allergic rhinitis, concomitant asthma, and any psychological diagnoses.9
Athletes are a particular subset of patients with VCD who are crucial to appropriately diagnose, including a detailed history and physical, PFTs, and proceeding to direct laryngoscopy to confirm diagnoses.10 Behavioral management includes rescue breathing techniques, and speech therapy programs focus on relaxation of the larynx and diaphragmatic breathing techniques, with the goal of establishing sense of control during acute events.10 Military service members are expected to operate at a high-intensity level similar to that of athletes, and treatments considered for athletes are applicable to military service members as well. Military strength and cardiovascular standards are measured by a combination of push-ups, sit-ups, and a run test, in addition to waist measurements. Some of the cohort were identified during physical fitness standard failures, usually in the run test, and ultimately received a pulmonology referral for wheezing or dyspnea with exertion. The objective of this retrospective cohort study was to evaluate 100 consecutively diagnosed cases of VCD in a military treatment facility.
Methods
The authors conducted a retrospective chart review of DoD military medical records of outpatient diagnoses in 100 consecutive diagnoses of VCD from January 2011 to February 2014. Institutional review board approval was obtained under Project RSM20130001E by the Exempt Determination Official at Eglin Air Force Base (AFB), Florida.
All cases were identified at time of VCD visualization and were diagnosed with video stroboscopy by speech therapy or by visual laryngoscopy by the otolaryngology or pulmonology departments via direct visualization.
Cases were collected chronologically, and all diagnosed cases at Eglin AFB hospital were included. Follow-up was scheduled with all patients diagnosed in Speech Therapy, and most patients were concurrently treated by Pulmonology or Allergy/Immunology. Pulmonary function tests were obtained in 98 of the 100 diagnosed cases. Patients eligible for care at Eglin AFB included active-duty and Reserve military members plus dependents and retirees.
The majority of patients diagnosed in this cohort were seen and diagnosed by Speech Therapy. Video stroboscopy is based on the principle that a movement of an object higher than a certain flicker rate appears to stand still to direct visualization, but with a rate of light exposure and imaging above the flicker rate by video, the true movement of the object can be identified.¹¹ Video stroboscopy is considered highly sensitive for organic disorders of vocal cords, but it is not specific for either organic or dysfunctional disorders.¹¹ It is still the gold standard above direct visualization, as it can detect abnormal movement of vocal cords above the critical rate that the human eye would perceive as not moving due to the frequency of movement (Figures 1 & 2).¹¹
In an older study, laryngoscopy was able to diagnose 100% of patients with symptomatic paradoxical vocal cord movement and additional 60% asymptomatic patients with a constellation of symptoms consistent with paradoxical vocal cord movement.¹²
Speech Therapy; Ear, Nose, and Throat (ENT); and Pulmonology may not perform direct visualization in these patients at initial presentation due to other suspected diagnoses. A more common test is the PFT, especially if asthma or other airway tract diseases are suspected (Figure 3).
