120 THE DIAGNOSIS OF PAEDIATRIC VOCAL CORD DYSFUNCTION (VCD)

Abstract

VCD in children is a poorly recognised entity, easily confused with asthma. Thirty-seven children with a diagnosis of VCD made by rhinolaryngoscopy were identified. Eight of 29 patients diagnosed with both VCD and asthma were evaluated during attacks of VCD (defined by rhinolaryngoscopy) or asthma (defined by a positive methacholine challenge). We examined retrospectively the value of clinical assessment, spirometry and blood gas analysis in differentiating between episodes of VCD and asthma in these patients. Laryngeal stridor was the most reliable clinical feature that distinguished VCD from asthma, occurring in 6/8 episodes of VCD and 1/8 episodes of asthma. The presence or localisation of expiratory wheezing was not helpful. Spirometric data did not reliably distinguish VCD from asthma, although inspiratory loop truncation occurred during 4/8 episodes of VCD and not during, asthma. The mean arterial oxygen level, though lower in asthma than in VCD, did not reliably differentiate between both conditions. However, the calculated alveolar-arterial (A-a) gradient was narrow during all episodes of VCD (mean = 6.75 mm Hg) whereas it was widened during all episodes of asthma mean = 20.3 mm Hg). We conclude that VCD occurs in children and frequently coexists with asthma. Episodes of VCD and asthma are not reliably distinguished in children by clinical and spirometric evaluation. Rhinolaryngoscopy is therefore necessary to establish a diagnosis of VCD. Subsequent episodes of VCD may be reliably distinguished from asthma by a normal A-a gradient.