Head and Neck ImagingMucocele
expansile
lesion occurring within the cavity of a
paranasal sinus, containing mucoid secretions and bordered by the
sinus mucous membrane. These lesions cause pressure erosion and expansion of the bony
sinus walls, and may displace adjacent structures. Mucoceles are most commonly seen in the
frontal sinus, but may occur in any
paranasal sinus. They originate from
obstruction of the
sinus ostium by
inflammation,
trauma (including surgery) or a
benign or
malignant tumour. The symptoms result from the mass itself and include frontal bossing, proptosis and nasal
obstruction.
A mucocele appears on imaging as an expansile lesion in an airless sinus, with thinning and sometimes erosion of its bony walls (Fig.1). Sometimes a mucocele arises from a closed compartment of a paranasal sinus (see Caldwell Luc procedure). Inspissated mucoceles may show a high density on CT images. The signal characteristics on MRI are variable and depend on the degree of dehydration of the sinusal secretions (Fig.2). Apart from the lining membrane, no contrast enhancement is seen in a mucocele; the enhancement of the lining membrane is more pronounced in an infected mucocele (mucopyocele).
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Frontal mucocele (arrows), compressing the left orbit. Due to dehydration of the secretions, the central portion of the mucocele (asterisk) shows low signal intensity on the coronal T2-weighted (a) and a relative high signal intensity on the T1-weighted (b) spin-echo image.
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Mucocele, Fig.1 | | Mucocele, Fig.2 (a) | | Mucocele, Fig.2 (b) |