A 55-year-old man presented with chronic headaches. He had right orbital pain for several months and right exophthalmos. Otherwise, he did not have any significant medical history. Physical examination revealed right exophthalmos and a palpable mass in the right medial canthus, which prompted a computed tomography (CT) scan of the orbits/sinuses (Figures 1 and 2).
Erini Makariou, MD
Nouredine Guaouguaou, MD,
Department of Radiology, Georgetown University Hospital,
A 55-year-old man presented with chronic headaches. He had right
orbital pain for several months and right exophthalmos. Otherwise,
he did not have any significant medical history. Physical
examination revealed right exophthalmos and a palpable mass in the
right medial canthus, which prompted a computed tomography (CT)
scan of the orbits/sinuses (Figures 1 and 2).
Exophthalmos caused by an ethmoidal mucocele
The CT examination of the orbits/sinuses showed a well-defined
ovoid mass that was homogenous in appearance, expanding and
obliterating the right ethmoid cells. The lesion was predominantly
hypo-dense and measured 3.5 × 2.7 × 2.7 cm. There was erosion of
the medial wall of the right orbit and extension of the mass into
the orbit with lateral displacement of the medial rectus muscle and
optic nerve. The lesion caused exophthalmos (Figure 1). It extended
superiorly through an erosion of the orbital roof into the frontal
sinus, which was opacified. There was also erosion of the
cribriform plate but no involvement of the brain parenchyma (Figure
A mucocele is an epithelial-lined, mucus-containing sac that is
the most common cause of paranasal sinus expansion. Accumulation of
mucoid secretions behind an obstructed paranasal sinus ostium is
the primary etiology. This accumulation expands the sinus cavity
and produces thinning or erosion and remodeling of the bony wall.
The obstruction of the sinus cavity can be due to many causes, such
as chronic sinusitis, nasal polyposis, neoplasia, postsurgical
changes, or any other abnormality or trauma. They occur most
frequently in the fronto-ethmoidal region. The frontal sinuses are
involved approximately in 60% of cases, the ethmoidal complex in
30%, the maxillary in 10%, and the sphenoid sinuses are involved
There is an increased incidence in patients with cystic
Mucoceles are usually observed during adulthood. In most cases,
patients have a clinical history of chronic nasal polyposis or
panasinusitis. The leading symptoms are unilateral proptosis with
ophthalmalgia, double vision or decreased acuity, a palpable mass
in the superior medial aspect of the orbit or medial canthus with
the fronto-ethmoidal mucoceles, and headaches.
On plain X-ray films, a soft-tissue density mass may be seen
obliterating the sinus with associated expansion of the involved
sinus. Bony changes, such as erosion or thinning, may also be seen,
especially with frontal mucoceles. These findings are better
visualized on CT. Surrounding zone of bone thickening due to
chronic infection is another manifestation. After intravenous
contrast administration, there is uniform lack of enhancement with
only a rim of enhancement from the infected mucosal membrane.
Macroscopic evidence of calcifications may suggest superimposed
fungal infection as seen in 5% of the cases. On magnetic resonance
imaging (MRI), mucoceles are of low signal intensity on T1-weighted
and of high signal intensity on T2weighted images. But a mixed type
of signal may also be seen based on the presence of blood or
inspissated secretions. Postgadolinium-enhanced MRI shows no
enhancement of the mucocele.
Sinus cavity expansion differentiates mucoceles from
uncomplicated chronic sinusitis (a finding never seen with
sinusitis). It may be impossible to separate a long-standing
mucocele producing bony erosions or remodeling from a sinus
malignancy or aggressive infection, without the benefit of
postcontrast images. A benign rim of enhancement is identified in
the case of a mucocele and a nodular or solid enhancement in the
case of malignancy.
Mucoceles may protrude into the orbits and cause vision problems
and proptosis. Intracranial extension may produce optic nerve
damage and blindness, involvement of the cavernous sinus with
neurological symptoms, or hormonal changes in case of involvement
of the sellar turcica/pituitary gland. Superimposed infections may
also occur leading to pyoceles.
Surgical complete removal of the sinus mucocele lining is the
traditional treatment. However, in recent years, there has been a
trend toward transnasal endoscopic management because of its low
morbidity rates and recurrence rates at or close to 0%.
Mucoceles are the most common benign lesions that produce
expansion of the paranasal sinuses. Approximately 90% occur in the
fronto-ethmoidal sinuses. Appropriate therapy of the mucocele may
correct the associated complications, such as exophthalmos, and may
prevent visual loss.