A mucocele is an epithelial lined mucus-containing sac completely filling a paranasal sinus and capable of expansion. They are relatively unusual, occurring most frequently in the fronto-ethmoidal region. The imaging features on plain X-ray, computerized tomography and magnetic resonance imaging are relatively characteristic allowing distinction of the lesion from other pathologies in this area although the mucoceles may occur in association with other pathologies such as nasal polyposis and neoplasia

Howard, D

Lloyd, G

Lund, VJ

Savy, L

English

UCL Discovery

Journal of Laryngology &amp; Otologyhttp://journals.cambridge.org/JLOAdditional services for Journal of Laryngology &amp; Otology:Email alerts: Click hereSubscriptions: Click hereCommercial reprints: Click hereTerms of use : Click hereOptimum imaging for mucocelesGlyn Lloyd, Valerie J. Lund, Lloyd Savy and David HowardJournal of Laryngology & Otology / Volume 114 / Issue 03 / March 2000, pp 233 ­ 236DOI: 10.1258/0022215001905238, Published online: 08 March 2006Link to this article: http://journals.cambridge.org/abstract_S0022215100000712How to cite this article:Glyn Lloyd, Valerie J. Lund, Lloyd Savy and David Howard (2000). Optimum imaging for mucoceles. Journal of Laryngology & Otology, 114, pp 233­236 doi:10.1258/0022215001905238Request Permissions : Click hereDownloaded from http://journals.cambridge.org/JLO, IP address: 144.82.107.169 on 17 Oct 2012The Journal of Laryngology and OtologyMarch 2000, Vol. 114, pp. 233–236Radiology in FocusOptimum imaging for mucocelesGlyn Lloyd, D.M., F.R.C.R., F.R.C.Ophth., Valerie J. Lund, M.S., F.R.C.S., F.R.C.S.(Ed.), Lloyd SavyB.Sc., F.R.C.R., David Howard, F.R.C.S., F.R.C.S.(Ed.)AbstractA mucocele is an epithelial lined mucus-containing sac completely ￿lling a paranasal sinus and capable ofexpansion. They are relativelyunusual, occurring most frequently in the fronto-ethmoidalregion. The imagingfeatureson plainX-ray,computerizedtomographyand magneticresonance imagingare relativelycharacteristicallowing distinction of the lesion from other pathologies in this area although the mucoceles may occur inassociation with other pathologies such as nasal polyposis and neoplasia.Key words: Mucocele; Frontal sinus; Ethmoid sinus; Diagnostic imagingIntroductionA mucocele is an epithelial lined mucus-containing saccompletely ￿lling a paranasal sinus and capable ofexpansion by virtue of a dynamic process of boneresorption and new bone formation.1,2 They are locallydestructive and the erosion and expansion of the bonywallsencroachupon and displaceadjacentstructures.Theyoccur most frequently in the frontal sinus but may arise inthe ethmoids and rarely in the sphenoid sinus or maxillaryantrum (Table I). They may result from infection, traumaincluding previous surgery, fractures and bullet wounds,nasal polyposis, or tumours (benign e.g. osteomas) orrarely,malignant).Most cases result from a combinationofobstruction and in￿ammation although cases in which nodemonstrable cause can be determined, represent thelargest sub-group (36 per cent).3 In some cases there ishistological evidence of an increase in the number ofsecretory cells in the lining membrane and hypersecretionof mucus may be a contributory factor.2,4 One recent studyhas demonstrated an increase in pressure within themucocele.5Materials and methodsFrom a cohort of 121 patients with paranasal sinusmucoceles, imaging was available for retrospective studyin 70 cases. This review is based upon the results of thisanalysis togetherwith the review of the relevant literature.Plain X-raysFrontal sinus mucoceles can be readily diagnosed on plainX-ray but mucocelesin the maxillaryantrum and sphenoidsinuses may not be recognized as such and in the anteriorethmoids they may be missed entirely. For these reasonsCT is the primary imaging method of choice.Computerized tomography (CT)CT in the axial and direct coronal planes is the optimummethod of showing the bone expansion which occurs inmucocele formation; typically the bony outline becomesmore rounded as the bone remodels in response to thegrowing pressure within the sinus cavity. The mucocelecontent is demonstrated as an homogeneous substance ofmucoid attenuation (10 to 18 HU).6 In long-standingmucoceles with a high protein content, the attenuation ishigher (20–40 HU). After intravenous contrast, only thelining membrane of the mucocele will enhance, though theadministration of contrast medium is rarely necessary.Contrast enhancement is best reserved for magneticresonance imaging (MRI) particularly when there ismucocele formation secondary to a sinonasal tumour(Vide infra).Magnetic resonance imagingMost mucoceles, especially the most common occurring inthe frontal sinus, can be diagnosed by CT or plain X-ray.MRI is only indicated when there is uncertainty followingthe use of these techniques.The usual signal characteristicsare a low T1 and a high T2 but any combination of signalintensitymay be seen depending on the presence of bloodproducts or the degree of hydration of the contents.Generally the older the mucocele the shorter the T1relaxation time. In these circumstances gadolinium-enhanced MRI is a more certain means of diagnosis. The￿uid contents of the expanded sinus will be con￿rmed ifthere is an absent signal after contrast. Post-contrastMRIis particularly useful for demonstrating secondary muco-cele formation when the underlying cause is not demon-TABLE Idistribution of paranasal site mucoceles(n = 121)Fronto-ethmoid 89%Ethmoid 8%Sphenoid 2%Maxilla 1%233strated on CT. The non-enhancing mucocele is readilydistinguished from the causative pathology (Figure 1).Frontal sinusThe classicalappearanceof a frontalsinus mucoceleon CTor plain X-ray is that of an opaque, expanded sinus withloss of the normal scalloped margin. It should be noted,however, thatthis is not a constantfeaturesince it does notoccur when only the horizontal part of the sinus is affectedwhich occurs in approximately 25 per cent of frontal sinusmucoceles.Otherchanges include depression or erosion ofthe supra-orbitalridge and extensionof the softtissue massacross the mid-line through the septum to the oppositefrontal sinus (Figures 2 and 3).Ethmoidal mucocelesThe majority of these are found in the anterior group ofthe ethmoidal cells and it is sometimes dif￿cult todistinguish whether the mucocele has arisen within asuperior anterior ethmoidal cell or the frontal sinus itselfwhen they are best referred to as fronto-ethmoidal(Figure.4). Mucoceles of the posterior ethmoid cells areless common (Figure 5) and may be occasionallyassociated with sphenoid mucoceles.Ethmoid mucoceles are dif￿cult to detect on plainX-raysbut are usually obvious clinicallysince most presentwith a palpable mass at the medial canthus combined withproptosis, lateraland inferior displacementof the globe 91per cent, 55 per cent and 59 per cent respectively.3Epiphora may also occur when expansion of the mucoceleaffectsthe lacrimal sac or duct.Sphenoid mucocelesImaging techniques play a key role in the diagnosis of asphenoid mucocele and it is important that the conditionisrecognized by the radiologist at an early stage so that itFig. 1Coronal T1-weighted MRI. The post-Gadoliniumscan showsa frontal sinus mucocele (non-enhancing) secondary to asquamous cell carcinoma.Fig. 2Coronal CT of a frontal sinus mucocele. There is an opaqueexpanded sinus with loss of the normal scalloped margin anderosion of the supra-orbital ridge.Fig. 3Axial T2-weighted MRI showing a frontal sinus mucocele.234 g. lloyd, v. j. lund, l. savy, d. howardmay be dealt with surgically before vision is seriouslycompromised. The proximity of the sphenoid sinus to theoptic nerve, cavernous sinus and oculo-motor nervesmeans that mucocele expansion readily gives rise tosymptoms resulting from involvement of these structures.Headache combined with eye symptoms such as blurredvisionor diplopiaare early complaints,frequentlyfollowedby visual loss. On plain radiographs sphenoid mucocelesare liable to be mis-diagnosed as pituitary tumours or anasopharyngeal tumour invading the sphenoid; in eithercase this may result in inappropriate treatment.In general the radiological features become moreemphatic as the lesion expands the sphenoid sinus,resulting in elevation or destruction of the ￿oor of theFig. 4Axial CT showing expansion of the anterior ethmoidcells dueto a mucocele.Fig. 5Axial CT showing a small posterior ethmoidal mucocele. Thepatient had undergone previous external fronto-ethmoidect-omy elsewhere with a frontal sinus drainage tube left in situ.Fig. 6Axial CT showing a sphenoid mucocele. The ethmoids areopaque due to nasal polyposis.Fig. 7Coronal MRI post-gadoliniumshowing expression of the rightmaxillary antrum due to a mucocele.radiology in focus 235pituitary fossa on the lateral skull ￿lm. Progressiveexpansion will also cause erosion of the medial wall ofthe optic canal and elevation of the planum sphenoidale.CT will show the typical rounded or partially roundedexpansion of the sinus (Figure 6) as opposed to thedestruction of bone associated with neoplasia. MRI is notalwaysneeded for diagnosisbut is the optimummethod fordemonstrating the ￿uid content of the mucocele.Maxillary mucocelesThe maxillaryantrum is a relativelyrare site for mucoceleformation,accounting for 10 per cent or less of mucocelesreported in Europe and the United States,7 odontogeniccysts or cholesterolgranuloma being more common causesof expansion of the antrum. However, in Japan a largeseries of antral cysts or mucoceles have been describedassociatedwith previous CaldwellLuc surgery.8,9 Clinicallythe symptoms are due to sinus expansion into the nose,mouth and orbit resulting in upward displacement of theeye, proptosis and swelling of the cheek. On plain X-raythe sinus is invariably opaque and expanded and as in theother sinuses enlargement with good preservation of thesinus walls is the clue to the diagnosis. CT is indicated tocon￿rm the expansion and MRI will establish the ￿uidcontent of the expanded sinus (Figure 7).References1 Canalis RJ, Zajekuk JT, Jenkins HA. Ethmoidalmucoceles.Arch Otolaryngol 1978;104:286–912 Lund VJ, Milroy CM. Fronto-ethmoidal mucocoeles. ahistopathological analysis. J Laryngol Otol 1991;105:921–33 Lund VJ. Anatomical considerations in the aetiology offronto-ethmoidalmucocele. Rhinology 1987;23:83–84 Lund VJ, Henderson B, Yu Song. Involvement of cytokinesand vascular adhesion receptors in the pathology of fronto-ethmoidal mucoceles. Acta Otolaryngol (Stockh)1993;113:540–65 Kass FS, Fabian RL, Montgomery WW. Manometric studyof paranasal sinus mucoceles. Ann Otol Rhinol Laryngol1999;108:63–66 Forbes W, St C. MRI and CT of the Head and Neck.London: Chapman and Hall Medical, 19947 Marks SC, Latorii JD, Mathog RH. Mucocoeles ofmaxillary sinus. Otolaryngol Head Neck Surg 1997;117:8–218 Iinuma T, Mitzutami A, Miyakawa K. Post-operative cystsof the maxilla. A review of 474 cases. Practica Otol1974;67:427–369 Hasegawa M, Saito Y, Watanabe I. Post-operative muco-celes of the maxillary sinus. Rhinology 1979;17:253–6Address for correspondence:Professor V. J. Lund,Institute of Laryngology and Otology,University College London,330 Gray’s Inn Road,London WC1X 8DAFax: 1 44 171 833 9480TABLE IIdifferential diagnosisFungal diseaseCholesterol granulomaOdontogeniccyst (maxilla)Neoplasia – benign– malignant236 g. lloyd, v. j. lund, l. savy, d. howard

Anatomical considerations in the aetiology of fronto-ethmoidalmucocele.

Fronto-ethmoidal mucocoeles. a histopathological analysis.

Involvement of cytokines and vascular adhesion receptors in the pathology of frontoethmoidal mucoceles. Acta Otolaryngol (Stockh)

Manometric study of paranasal sinus mucoceles. Ann Otol Rhinol Laryngol

Mucocoeles of maxillary sinus. Otolaryngol Head Neck Surg

Post-operative cysts of the maxilla. A review of 474 cases.

Post-operative mucoceles of the maxillary sinus. Rhinology 1979;17:253–6 Address for correspondence: Professor

Road, London WC1X 8DA Fax:

Optimum imaging for mucoceles

Optimum imaging for mucoceles

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