Also available as PDF (figures and tables appear in the PDF).
Introduction: Mucoceles are cystic masses developing after obstruction of the sinus ostium. The symptoms are not specific. Computed Tomography scan (CT scan) and Magnetic Resonance Imaging (MRI) confirm the diagnosis. Objectives: We herein review the radiologic characteristics of mucoceles in CT scan and MRI. Materials and Methods: We report a retrospective study of 43 patients diagnosed with paranasal sinuses mucoceles. CT scans were performed for all patients, but MRI was carried out only in selected cases. Results: Our study was constituted of 27 males and 16 females with a mean age of 47 years. The CT scan appearence of mucoceles were in all cases as a well circumscribed expansile si-nus mass with an effect on the neighbor bone structure. This mass was hypodense in 26 cases, isodense in 14 cases and hyperdense in 3 patients. The paranasal sinuses most frequently affected in our series were the fronto-ethmoidal sinuses. The most affected bone eroded was the lamina papiracea. Intracranial extension was seen in four cases. CT scan allowed to predict the cause of mucoceles in some cases and to provide information about anatomic variants. MRI was realized for 15 patients in addition to the CT scan. It allowed to study the extension of mucoceles to the neighboring organs especially orbital and endocranial ones. Conclusion: The presentations of mucoceles on imaging are quite variable. CT scan provides precious information about the location, bone erosion and extension of the mucoceles. MRI is indicated in some cases especially in cases of orbital or cranial extension.
Keywords: Mucoceles; Paranasal sinuses; Computed Tomography scan (CT scan); Magnetic Resonance Imaging (MRI)
Mucoceles are benign, slow-growing paranasal sinus lesions that develop after obstructions of
the sinus ostium.1 Symptoms are variable. The diagnosis is based on imaging. CT scan of the
sinuses is the method of the choice. MRI is indicated in some cases and provides much infor-
mation of mucocele extensions to adjacent compartments.2
The purpose of this study was to review the role of pre-operative imaging and to il-
lustrate the main characteristics imaging findings of paranasal sinuses mucoceles.
and December 2012.
CT scans of the head were performed for all patients.
Axial, sagittal, coronal and contrast CT scan with 3 mm slice
thickness were reviewed in all cases.
MRI was carried out only in selected cases for the
evaluation of the extension of sinonasal mucoceles. MRI find-
ings on coronal and axial views in T1, T2 weighted and contrast
enhanced images were studied.
Our study was constituted of 27 males and 16 females (sex ra-
tio=1.68) with a mean age of 47 years (from 14 to 77 years).
Rhinosinusitis past history was present in six patients,
a facial traumatism in seven patient and eleven patients have
undergone prior sinus surgery.
The most commonly reported symptoms were ophthal-
mologic one (n=24, 56%), including proptosis (n=16), chronic
lacrimation (n=7), diplopia (n=3), visual acuity reduced (n=2)
and ptosis (n=1).
Headache was present in twenty three patients. Rhino-
logic symptoms were reported in 20 patients and were domi-
nated by chronic discharge (17 cases).
ing the right ethmoid.
On examination, we noted a face swelling in 17 cases,
a proptosis in 16 patients and ophtalmoplegia in two cases.
Endoscopic nasal examination revealed an obstructive
deviation of nasal septum in 10 cases, a filling of middle meatus
in six patients and adhesions between the middle turbinate and
the nasal septum in three cases.
CT scan: The CT scan appearence of mucoceles were in all cases
as a well circumscribed expansile sinus mass with an effect on
the neighbor bone structure. This mass was hypodense in 26
cases, isodense in 14 cases and hyperdense in 3 patients. After
injection of contrast agents, we saw a poor enhancement in three
cases and a peripherally enhanced image in all others cases.
The paranasal sinuses most frequently affected in our
series were the fronto-ethmoidal sinuses (Figure 1). Mucoceles
involved both the frontal and ethmoidal sinus in fourteen cases,
ten mucoceles were located in the ethmoid sinus, and five were
located in the frontal sinus (Figures 2, 3 and 4).
Bone erosion was noted (Figures 5 and 6). The most
affected was the lamina papiracea which was eroded in 27 cases
(Table 1).
Intracranial extension was seen in four cases and was
Lamina papiracea 27
Orbital roof 9
Ethmoidal roof 6
Anterior wall of frontal sinus 5
Posterior wall of frontal sinus 5
Postero-superior wall of sphenoidal sinus 3
Medial wall of maxillary sinus 2
External wall of maxillary sinus 1
F: Frontal sinus; E: Ethmoidal sinus; M: Maxilary sinus; S: Sphenoidal sinus.
Table 1. Bone erosion in our study.
consequently to a frontal mucocele in one case, fronto-ethmoidal
mococele in two cases, spheno-ethmoidal mucocele in one other
case (Figure 7).
Extension into the orbite was observed in 27 cases and
concerned predominately the medial wall of the orbite. Optic
nerve was repulsed in two cases of fronto-ethmoidal mucoceles
and one case of fronto-ethmoido-maxillary mucocele. It was
compressed in others three cases of: Ethmoidal, Sphenoidal and
Spheno-ethmoidal mucoceles. We noted one case of atrophic op-
tic nerve in a sphenoidal mucocele (Figures 8, 9 and 10).
CT scan allowed to note a proptosis in 17 cases (grade 2 in
2 7 _ _ 12 4 2 _
2 _ _ _ 5 2 _ _
_ _ _ _ 4 2 _ _
2 _ _ _ 2 1 _ _
2 _ _ _ 2 1 _ _
_ _ 1 _ _ 2 _
_ _ 2 _ _ _ _ _
_ _ 1 _ _ _ _ _
16 patients and grade 3 in one patient with a fronto-ehtmoidal
mucocele associated with an important orbital extension) Others
lesions were observed some predicted of the cause of mucoceles:
*Adhesions between the middle turbinate and lateral nasal wall
were observed in three patients who had prior sinus surgery and
were seen respectively in an ethmoidal, fronto-ethmoidal and
fronto-ethmoidal maxillary mucoceles.
*Calcifications of the frontal recess in one patient having a fron-
tal mucocele and history of craniofacial traumatism.
*Sinus retention were noted in three cases of maxillary mucoce-
le, fronto-ethmoidal and fronto-ethmoido-maxillary mucocele.
*Concha bullosa was present in four patients presenting: Ethmoi-
dal mucocele, Fronto-ethmoidal mucocele, Maxilary mucocele
and Nasal cavity mucocele. (Figure 11)
*Hypoplastic frontal sinuses was noted in one case of ethmoidal
mucocele.
*Agenesis of the frontal sinus in one case of ethmoidal mucoce-
le. (Figure 12)
*Presence of a frontal cell (kuhn’s cell) in a frontal mucocele.
(Figure 13)
*Paradoxical middle turbinate in one patient having a fron-
to-ethmoidal mucocele.
*Septum deviation was observed in 17 patients and were obs-
tructive in 10 cases.
CT scan provided also information about anatomic variants. We
noted:
*Procidence of the canal of the carotid artery in four cases. It
was bilateral in three cases (frontal, maxillary and sphenoi-
: Axial CT scan imaging showing a
mucocele developing from a concha bullosa of the left middle turbinate.
dal mucocele) and unilateral in one case of fronto-ethmoidal
mucocele associated with the presence of a sphenoid sinus septa
attached to the artery canal.
*Procidence of the optic nerve canal in one case of a frontal
mucocele.
*Asymmetry in the height of the ethmoid roof in two cases of a
fronto-ethmoidal mucoceles.
MRI: MRI was realized for 15 patients in addition to the CT scan.
It was indicated in four cases of sphenoid mucoceles (Figure 14)
and in 11 cases presenting orbital or endocranial extension on
CT scan.
Mucoceles appeared as a homogenous round mass who was in:
-Hypointense signal on T1-weighted images, hyperintense si-
gnal on T2-weighted images in nine cases.
-Hyperintense signal on T1-weighted and T2-weighted images
in two cases.
-Hypointense signal on T1-weighted images, isointense signal
on T2-weighted images in two cases.
-Isointense signal on T1-weighted images, hyperintense signal
on T2-weighted images in one case.
-Isointense signal on T1-weighted and T2-weighted images in
one case.
In all cases, we have noted no enhancement after injection of gadolinium.
MRI allowed to study the extension of mucoceles to the neighbo-
ring organs especially orbital and endocranial ones. We observed
that:
-The orbite contents was repulsed in two cases of fronto-eth-
moidi-maxillary mucoceles and one case of fronto-ethmoidal
mucocele. (Figure 15)
-Optic nerve was pushed in three patients who had respectively
sphenoid mucocele, spheno-ethmoidal mucocele, fronto-eth-
moido-maxillary mucocele.
It was stretched in one case of fronto-ethmoidal mucocele with
important orbital extension.
-Endocranial extension was noted in three cases: Spheno-eth-
moido mucocele, fronto-ethmoidal mucocele and fronto-eth-
moido-maxillary mucocele. (Figure 16)
Paranasal sinus mucoceles are cystic masses filled with mucous and lined by respiratory epithelium which are capable of expan-
sion by bone resorption and new bone formation.
They occur principally in the third or fourth decades of
life with a male predilection.
Mucoceles result from the blockage of the sinus drain-
age secondary to inflammation, trauma, anatomical aberrations,
tumours. chronic rhinosinusitis, allergic disease and craniofacial 2,3 disease are the most common cause of mucocele formation.2,3
Symptoms depend on the location of the mucocele
and may vary from rhinological, neurologic, or ophthalmologic 1-3 ones.1-3
CT scan is considered to be the complementary method
of choice in the investigation of mucoceles. It allows to evoke
the diagnosis of the mucocele and determine its location, to study
the neighboring structure (bone erosion, extension), to presume
an aetiology of the sinus ostium obstruction and to research the 3,4 anatomic variants of the sinuses.3,4
Mucocele appears on CT as a homogenous well circu-
mbscribed expansible cyst involving one or much sinuses and
may expand to neighboring structure. they may appear either
hypo- or hyperdense.4 This variable densities depend on their
protein content and possible infection. Mucoceles do not show
contrast enhancement centrally but a thin peripheral enhance-
ment, can be seen and is suggestive of encapsulation.5
The differential diagnosis for mucocele is made with
inflammatory, congenital cystic and neoplastic lesions of skull
base, facial sinuses and nasopharynx.4-6
Mucocele location depends on anatomic conditions that favorise its formation. The frontal sinus is most commonly
affected followed by the ethmoid sinuses, mucoceles occur in these locations in 70 to 90%. Sphenoid mucoceles are rare. The
maxillary antrum is a relatively unfrequent site for mucocele
formation, accounting for 10 percent or less of mucoceles.
In our study, mucoceles were seen frequently in fronto-
ethmoidal sinus followed by ethmoidal location then frontal si-
nus.
The neighboring bone structure is remodeled with areas 2,4,5 of thickening and erosion. In some areas of greater fragility,
we may observe herniation into adjacent structures such as the 4,9 orbite and the endocrine.
CT scan provides also information about existence of
factors favorising mucoceles formation as: Osteoma, Fibrous
displasia, Facial traumatism, Sinonasal polyposis. It can visual-
izes anatomic abnormalities that may cause a blockage of sinus 10-12 drainage. For our patients, CT scan has allowed to evoke the
cause of mucoceles in some cases as adhesions, concha bullosa,
septum deviation, paradoxical middle turbinate.
Furthermore, this exam is essentially to define anatom-
ic variants prior to surgery.13
MRI is an excellent exam in mucocles. It allows to dif-
ferentiate and to assess any extension into the orbit or intracrani-
al compartment, but, unfortunately it can’t study bone detail.
Its indications are in complement of the CT scan in case
of diagnosis doubt in CT scan between mucocele and other tu-
mors or inflammatory lesions, in case of sphenoid location and
in endocranial or orbital extension.14
The MRI appearance of paranasal sinus mucoceles is
quite variable, depending on the composition of the mucocele.16
The usual signal characteristics are a low intense T1 and a high
intense T2 but any combination of signal intensity may be seen
depending on the presence of blood products or the degree of 5,14,17,18 hydration of the contents. The appearance consisted of
hyperintense signal on both T1 and T2 type images, correspond-
ing to more hydrated secretions, which are also high in protein 17-20 content.
We have noted variable presentation of mucocele in
MRI from hypo to hyperintensity T1 and T2 but in all cases, we
have noted no enhancement after injection of gadolinium.
The presentations of mucoceles on imaging are quite variable
depending on its contents. Practicians should know the typical 4-6 as well as atypical findings. Special care should be taken with
regard to differential diagnosis and associated cases.16
The authors declare that they have no conflicts of interest.
7,8 CONSENT
As our article is a retrospective study and did not publish any
personal photo or information regarding any of the patient in
our manuscript thus the consent is not required for the article
publication.