Paranasal sinusitis
The MRI signals in the frontal, maxillary, and sphenoid sinuses were classified as follows 20:
0. Absence of signal: normal 1. Visible illumination of the sinus mucosa, although <5 mm: normal 2. Thickening of the mucosal membrane ≥5 mm, although occupying less than 50 % of the cross-section of the sinus: pathological 3. The mucosa occupies more than 50 % of the cross-sectional area, although the sinus still contains some air: pathological 4. Total sinus opacification or fluid level: pathological 5. Polyp or retention cyst: a lesion with rounded edges surrounded by air: pathological 6. Other: anatomic abnormalities presumed to be attributable to previous nasal or sinus surgery: pathological
The MRI signals in the ethmoid sinuses were classified as follows20:
0. Absence of signal: normal 1. Minimal or moderate sinus opacification: normal 4. Marked or total sinus opacification: pathological
Paranasal sinusitis was defined as the presence of abnormal findings in at least one of the paranasal sinuses detected by head MRI.