Changes in paranasal sinus abnormalities found incidentally on MRI.

Abnormal opacification of paranasal sinuses on brain MRI was studied in 178 consecutive adult patients who underwent two examinations separated by at least 4 months because of suspected neurological disease. Sinus abnormality was present in 79 (44%) patients; in 60% the abnormality involved two or more sinuses and it was bilateral in 51%. The most frequently abnormal sinus was the maxillary (46%), followed by the ethmoid (32%), sphenoid (16%), and frontal sinuses (6%). Interval occurrence or complete resolution of abnormalities was observed in 52% of patients (66% of the sinuses). In the remaining 48% of patients the abnormalities were present on two or more examinations, unchanged or of increased or decreased severity. The most frequent interval changing abnormalities were complete sinus opacification and fluid levels, followed by irregular mucoperiosteal thickening more than 4 mm thick. No polypoid abnormalities (polyps or mucosal cysts) decreased over time.