Tympanometric Measurement of Ear Canal Volume in Children With Trisomy 21: Rate of Growth and Predictive Value for Success of Ventilation Tube Insertion

INTRODUCTION: Children with trisomy 21 have narrow ear canals which can make ventilation tube insertion difficult or impossible. This study aimed to use ear canal volume, as routinely reported on tympanometry, to estimate the annual growth rate of the ear canal and to predict the success rate of ventilation tube insertion in children with trisomy 21. METHODS: We conducted a retrospective study on 50 children with trisomy 21 who each had tympanometric ear canal volume measurements available on 3 occasions to calculate the growth rate of the ear canal. We also conducted a separate retrospective study of 83 ventilation tube insertion attempts in 45 children with trisomy 21 to see if the tympanometric ear canal volume was predictive of success or failure. RESULTS: Ear canal volume grows at 0.04-0.05 mL/year on average in children with trisomy 21, but at any given age the variation between children is many times larger than this. Of 83 ventilation tube insertion attempts, 66 were successful (92%) and 7 failed (8%). All failures occurred in children with ear canal volume 0.51 mL or less. Age was not predictive of success of ventilation tube insertion. CONCLUSION: Smaller ear canal volumes are predictive of failure of ventilation tube insertion. Ear canal volumes do grow over time in children with trisomy 21 but at a slow rate. Tympanometry can provide information on ear canal volume, which is useful for discussions about how best to manage otitis media with effusion in children with trisomy 21.