A cross-sectional study of the change in mastoid geometry with age in children without a history of otitis media

Objectives/Hypothesis: This study assessed the normal growth and development of mastoid air-cell system (MACS) geometry from infancy through adolescence. Study Design: Cross-sectional study. Methods: This cross-sectional study evaluated the change with age in MACS volume, surface area, and surface area/ volume ratio in 36 (72 ears) individuals aged 1.6 to 18 years with no history of middle ear disease. The three MACS parameters were reconstructed using computed tomography (CT) scans judged by a radiologist to be normal. Linear regression was used to determine the relationship between the left and right values of each parameter, and between those parameters and age for male and female subjects. Results: For all three MACS parameters, the right and left values were highly correlated. MACS volume and surface area for male and female subjects showed an increase between 1 and 18 years. The surface area/volume ratio for males was independent of age but showed a shallow increase for females. When averaged across all ages, the ratio was similar to those previously reported. Conclusions: The growth trajectory for MACS volume observed in this study was not consistent with other cross-sectional studies employing planimetry or CT of normal subjects that reported inconsistent results. Because of its potential role as a susceptibility factor for otitis media and other otologic problems, it is important to describe the growth and development of MACS geometry. Additional well-controlled studies of this phenomenon are needed to clarify which of the growth trajectories actually describe the growth process for the three parameters of interest.