Incidental MRI and CT findings in paranasal sinuses and mastoid cells

With increasing numbers of CT and MRI scans being performed, this has lead to an  increase in diagnosis of Sinusitis and Mastoiditis being made and referral to our department.
 Fluid signal in the mastoid can be an incidental finding on T2-weighted magnetic resonance imaging and often is interpreted as mastoiditis by radiologists. 

A recent study examined 28 consecutive cases of such erroneously diagnosed "mastoiditis" and documents the presence or absence of otologic symptoms and clinical signs. They found a very low prevalence of otologic symptoms or pathology and no cases of mastoiditis in these patients, and they determined that magnetic resonance imaging is not an effective screening modality for mastoiditis.

Another study showed 61 % of children had one or more salient findings in their paranasal sinuses or mastoid cells. 48 % had mucosal swelling in their paranasal cavities, 25 % in their mastoid cells. The prevalence was higher among children less than 10 years of age (60 % and 42 %) and among children with current upper respiratory tract infection (71 % and 35 %). There was no correlation to a history of headache, snoring, asthma and allergies, or to gender or place of residence.

CONCLUSION:

Mucosal swelling in paranasal sinuses and in mastoid cells is a frequent incidental finding in adults and more commonly in children. Even major mucosal swelling in a paranasal sinus is not necessarily a sign of infection. In radiological reports the terms "sinusitis" and "mastoiditis" should therefore be used with great caution. The initiation of treatment should be based on clinical symptoms and not on radiological abnormalities alone.