Incidental mastoid opacification in children on MRI

Background: The opacification the mastoid cavity is frequently reported by radiologists on cross-sectional imaging done for non-otological indications. It is well known that presence of fluid the mastoid does not amount to mastoiditis. This study seeks to provide an evidence-based confirmation of this known finding. Objective: The purpose of our study was to determine the prevalence of mastoid opacification in children undergoing outpatient brain MRI examination. Materials and methods: Our study included 515 outpatient children who had brain MRI for indications other than mastoiditis or otitis media from January 2014 to March 2014. Children with history of skull base trauma or radiation were excluded. The age range was 15 days to 18 years. The overall prevalence of mastoid opacification was determined using one sample proportion and exact 95% Clopper-Pearson confidence intervals. The prevalence of mastoid opacification was analyzed based on gender, age and presenting symptoms using chi-square test of association. Results: One hundred ten children (21.4%) had mastoid opacification. Younger patients tended to have higher opacification rates with the prevalence in children younger than 1 year of age and between 1 and 2 years of age as high as 41.7% (20/48) and 47.5% (38/80), respectively. Conclusion: The diagnosis of mastoiditis in children should not be based upon a radiologist’s report of finding fluid or mucosal thickening in the mastoid air cells as incidental opacification the mastoid is seen frequently.