Mucocele

This is a case of a left frontal sinus mucocele in a 45-year-old male presenting with signs and symptoms of sinusitis for > 1 year. Image 1, a noncontrast axial T1-weighted sequence, demonstrates enlargement of the left frontal sinus with regions of intrinsic T1-hyper and hypointense signal. Image 2, an axial FLAIR sequence, demonstrates circumferential mucosal thickening, greatest laterally, with more FLAIR isointense signal within the central/medial left frontal sinus. The DWI and ADC maps, on images 3 and 4, demonstrate focal regions of reduced diffusivity within the medial aspect of the left frontal sinus. The fat-saturated axial T2 and post contrast fat-saturated axial T1-weighted sequences, images 5 and 6, redemonstrates the circumferential mucosal thickening and intrinsic T1-hyperintense material medially.These findings are classic for a left frontal sinus mucocele, which is the most common masslike complication of sinusitis. The variable protein content within the mucocele leads to variable signal intensity on the T1- and T2-weighted sequences. The most common sites of involvement are the frontal sinuses, ethmoid air cells, maxillary antra and sphenoid sinuses, in decreasing order of frequency.