Mucoceles are chronic,
cystic lesions in the paranasal sinuses. The contents of the mucocele
are sterile, and the lesion is known as mucopyocele if it gets infected.
They are the result
of obstruction of the sinus ostium, causing the accumulation of
secretions into an expanding mass, which lead to remodeling, and
erosion of bone, changing the bony architecture.
The symptoms can be
facial deformity, abnormal protrusion of the eyeball (proptosis)
or abnormal retraction of the eyeball into the socket (enophthalmos),
loss of vision or double vision (diplopia). They may also be non-specific,
such as facial pain, headache or nasal obstruction.
Lesions include sinonasal
polyps and mucous retention cysts. Polyps are inflammatory swelling
of the sinonasal mucosa. Mucus retention cyst is a mucinous gland
whose duct has become obstructed, causing the accumulation of mucus
in the gland.
A mucocele develops
when the drainage of a sinus is compromised. The sinus fills with
mucus and as more mucus accumulates, the sinus may expand from the
pressure. Sinus walls may be remodeled or completely de-ossified
Mucoceles can affect
any age group, and very often, over a year will elapse between a
presumed initiating event and development of a subsequent symptomatic
Mucoceles can resemble
other expansile processes of the paranasal sinuses, such as neoplasia
(new and abnormal growth or formation of tissue) or nasal polyposis.
Ninety percent of mucoceles
involve the frontal or the ethmoid sinuses, with the majority being
in the frontal sinus.
In a CT, the distinction
between a mucocele and a mucous retention cyst can be made on the
basis of the presence of air outlining the upper surface of the
mass. The distinction becomes less important when the lesion is
large, as the treatment is similar for such a large mucous retention
cyst as it is for a mucocele.
Mucoceles may extend
into adjacent structures by herniation. They may herniate internally,
staying within the confines of their sinus of origin or they may
herniate externally, extending outside of the sinus into surrounding
structures such as the orbit or cranial cavity.
of the mucoceles are similar in many respects to the appearance
of non-specific sinusitis, mucus retention cysts and nasal polyposis.
In recent years, advances
in endoscopic sinus surgery have lead to an acceptance of simple
drainage procedures, even for some seemingly very complicated mucoceles.