Computerized tomography (CT) offers the gold standard in terms of imaging the extent of disease and the fine detailed anatomy, both pre-requisites to the safe practice of endoscopic sinus surgery. Neither plain X-rays nor magnetic resonance imaging (MRI) offer optimal information in this respect. A variety of protocols minimizing radiation dose to the lens whilst providing high quality images are presented together with a menu of anatomical features that require careful evaluation pre-operatively

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 hereImaging for endoscopic sinus surgery in adultsValerie J. Lund, Lloyd Savy and Glyn LloydJournal of Laryngology & Otology / Volume 114 / Issue 05 / May 2000, pp 395 ­ 397DOI: 10.1258/0022215001905670, Published online: 08 March 2006Link to this article: http://journals.cambridge.org/abstract_S002221510000116XHow to cite this article:Valerie J. Lund, Lloyd Savy and Glyn Lloyd (2000). Imaging for endoscopic sinus surgery in adults. Journal of Laryngology & Otology, 114, pp 395­397 doi:10.1258/0022215001905670Request Permissions : Click hereDownloaded from http://journals.cambridge.org/JLO, IP address: 144.82.107.76 on 08 Oct 2012The Journal of Laryngology & OtologyMay 2000, Vol. 114, pp. 395–397Imaging for endoscopic sinus surgery in adultsValerie J. Lund, M.S., F.R.C.S., F.R.C.S. (Ed.), Lloyd Savy, B.Sc., F.R.C.R.,Glyn Lloyd, D.M., F.R.C.R., F.R.C.Ophth.AbstractComputerized tomography (CT) offers the gold standard in terms of imaging the extent of disease and the ￿nedetailed anatomy, both pre-requisites to the safe practice of endoscopic sinus surgery. Neither plain X-rays normagnetic resonance imaging (MRI) offer optimal information in this respect. A variety of protocols minimizingradiation dose to the lens whilst providing high quality images are presented together with a menu of anatomicalfeatures that require careful evaluation pre-operatively.Key words: Imaging; endoscopic sinus surgery; rhinosinusitisIntroductionFor many years plain radiographs provided clinicians withthe information required regarding sinonasal pathology,supplemented in selected cases by hypocycloidal tomogra-phy. The maxillary sinus was well displayed by plain sinusX-rays and was the focus of most surgical interventions inthe form of wash-outs, inferior meatal antrostomies andCaldwell-Luc procedures in chronic rhinosinusitis. Theresurgence of interest in the role of the natural drainagepathways of the sinuses embodied in the concept of the‘osteomeatal complex’ coincided with the improvedvisualization afforded by endoscopy and CT that in turnresulted in the widespread development of endoscopicsinus surgery (ESS) for in￿ammatory sinonasal disease.Plain X-raysWith the widespread availability of CT, the role of plainsinus X-rays (occipito-mental, occipito-frontal, and lateral)has become less clear. Plain X-rays are inexpensive andinvolve exposure to less radiation than CT but, for the pre-operative evaluation for endoscopic sinus surgery, CT isessential to demonstrate the ￿ne detailed anatomy and fullextent of disease. Therefore, plain X-rays are unnecessary.Computerized tomography (Figures 1 and 2)The necessity for a CT scan prior to endoscopic sinussurgery is now generally accepted as the gold standard indemonstrating both extent of disease and the ￿ne detailedanatomy. The literature contains many alternative proto-cols but the following have been developed over the last 16years to provide optimum imaging with minimal radiationdosage to the eye (Table I) (Figure 3).Fig. 1Coronal CT through infundibulum showing the optimalanatomical detail.Fig. 2Axial CT in same patient showing relationship of ethmoidsand sphenoid to orbit and carotid arteries.From the Institute of Laryngology and Otology, University College London, London, UK.395The direct coronals are a pre-requisite to virtually allprotocols even with the advent of the fast spiral scannerswhich have considerably improved the quality of recon-structed images, both axial and sagittal. Generally recon-structions are reserved for those patients who cannotadequately extend their neck. Axial scans optimallydemonstrate the relationship of the posterior ethmoidsand sphenoid to the optic nerve and carotid artery but maynot be required in every case, particularly were disease islimited to the anterior sinus system. The amount ofradiation exposure differs depending on the protocol,machine, kV and milliamperes-second (mAs) setting of thescanner3 ranging from a mean lens dose of 70.3 mGy at475.mAs and 17.6 mGy at 210 mAs to 4.7 mGy at 30 mAs.Stammberger4 estimated the lens dose from coronal CT tobe 12–90 mGy whereas that described by Rowe-Joneset.al.2 renders a means lens dose of 9.81 mGy (s.d. 6 5.62).These are all well below the doses regarded as relevant tocataract formation where a threshold of 0.5 to 2 Gy isthought to be signi￿cant.5It is generally agreed that the primary role of the CT isto provide information on the anatomy and extent ofpathology in chronic rhinosinusitis. A period of medicaltherapy is recommended prior to performing the scan andsome radiologists have advocated the use of a topicalvasoconstrictor immediately before scanning6 although thisis not employed in our own practice.A number of important anatomical landmarks may beexamined on the CT scan (Table II) which are of particularimportance in the avoidance of complications e.g. anabsent uncinate process in association with a hypoplasticantrum, or asymmetry of the cribriform niche. Commonvariations in anatomy may also be demonstrated, theincidence of which varies from series to series (TableIII).1,7–11The overall extent and pattern of sinus involvement maybe readily assessed on CT and estimation of disease extentis possible using a number of staging and scoringsystems12–18 of which the Lund and Mackay system hasbeen used for nearly a decade. However, it is wellestablished that the correlation of extent of disease withsymptoms is poor.19,20 It is also clear that there is nocorrelation between the various anatomical variants andextent of disease8,21 which has led to a re-examination oftheir importance in the development of chronic rhinosinu-sitis. It is also worth noting that a number of studies haveshown a signi￿cant degree of incidental changes in‘normal’ controls probably related to recent viral upperrespiratory tract infections.22–24Magnetic resonance imagingThere is an increasing tendency to request magneticresonance imaging (MRI) in preference to CT whichmay be led by the neurologists who obtain MRI in cases offacial pain but this fails to offer optimum information forsurgery. Not only is bone shown as a signal void butin￿ammatory change is potentially over-diagnosed.25Sinonasal mucosa has an excellent blood supply and as aconsequence readily gives a high signal. In addition thenasal cycle may affect the ethmoid sinuses.1 The study ofLeopold et al.26 has shown that whilst the majority ofpatients with acute maxillary sinusitis are symptomaticallybetter within a week, following antibiotic therapy, the sinusmucosa continues to give high signal suggestive ofin￿ammation in up to 50 per cent of scans at eightweeks. Whilst the sensitivity and speci￿city of MRI is ofgreat value in differentiating neoplastic disease from otherTABLE Iprotocols for ct scanning in chronic rhinosinusitisZinreich et al.1 Charing Cross2 RNTNEHPlane Direct coronal Direct coronal Direct coronalSlice thickness 4 mm 2 mm 5 mm (2.5 mm through the OMC)Increments 3 mm 8 mm Contiguous i.e. 5 mm (2.5 mm through the OMC)Scan images 20–25 10.+.2 axial 18–20Window 2,000 Houns￿eld units 2,000 Houns￿eld units Width: 4000Level + 350Radiation 125 kV, 450 mAs 120 kV, 200 mAs 120 kV, 100 mAsOMC = osteomeatal complex.TABLE IIanatomical features to be evaluated on ct scanFrontal and anterior ethmoid sinusesPneumatization of bullaFrontonasal recess – con￿guration e.g. suprabullar cellencroaching on frontonasal recessLamina papyracea – dehiscenceRoof – height and angle on each side– lateral lamella of cribiform niche– dehiscence– angle of crista galli– position of anterior ethmoidal arteryFrontal sinus – size, shape, septa (intersinus and lateral)Maxillary sinus – size and shapeWidth of infundibulumUncinate processInfra-orbital ethmoidal (Haller) cellsNasolacrimal ductPosterior ethmoidsPneumatization with respect to sphenoid e.g. spheno-ethmoidal (Onodi) cells and relation to optic nerveSphenoid sinusOptic nerveCarotid arteryFig. 3Axial images of identical section taken: (a) on narrow windowwidths and (b) on wide window widths showing difference ininformation on anatomy and pathology using a sub-optimaland optimal protocol, respectively.396 v. j. lund, l. savy, g. lloydtissue, this degree of discrimination is not normallyrequired in chronic rhinosinusitis.References1 Zinreich SJ, Kennedy DW, Rosenbaum AE, Gayler BW,Kumar AJ, Stammberger H. CT of the nasal cavity andparanasal sinuses: imaging requirements for functionalendoscopic sinus surgery. Radiology 1987;163:769–752 Rowe-Jones J, Mackay I, Colquhoun I. Charing Cross CTprotocol for endoscopic sinus surgery. J Laryngol Otol1995;109:1057–603 Maclennan AC. Radiation doses to the lens from coronalCT scanning of the sinuses. Clin Radiol 1995;50:265-74 Stammberger H. Functional Endoscopic Sinus Surgery.Philadelphia: BC Decca, 19915 Shrimpton PC, Jones DG, Hillier MC. Survey of CTpractice in the UK Part II Dosimetric aspects. NRPB-R249. London: HMSO, 19916 Stringer SP, Manusco AA, Avino AJ. Effect of topicalvasoconstrictor on computed tomography of paranasalsinus disease. Laryngoscope 1993;103:6–97 Bolger WE, Butzin CA, Parsons DS. Paranasal sinus bonyanatomic variations and mucosal abnormalities: CTanalysis for endoscopic sinus surgery. Laryngoscope1991;101:56–648 Lloyd GAS, Lund VJ, Scadding GK. CT of the paranasalsinuses and functional endoscopic surgery: a criticalanalysis of 100 symptomatic patients. J Laryngol Otol1991;105:181–59 East CA, Annis JAD. Preoperative CT scanning forendoscopic sinus surgery: a rational approach. ClinOtolaryngol 1992;17:60–610 Meloni F, Mini R, Rovasio S, Stomeo F, Teatini GP.Anatomic variations of surgical importance in ethmoidallabyrinth and sphenoid sinus. A study of radiologicalanatomy. Surg Radiol Anat 1992;14:65–7011 Arslan H, Aydinhoglu A, Bozkurt M, Egeli E. Anatomicvariations of the paranasal sinuses: CT examination forendoscopic sinus surgery. Auris Nasus Larynx1999;26:39–4812 Friedman WH, Katsantonis GP, Sivore M, Kay S.Computed tomography staging of the paranasal sinusesin chronic hyperplastic rhinosinusitis. Laryngoscope1990;100:1161–513 Jorgensen RA. Endoscopic and computed tomographic￿ndings in osteomeatal sinus disease. Arch OtolaryngolHead Neck Surg 1991;117:279–8714 Gaskins RE. A surgical staging system for chronic sinusitis.Am J Rhinol 1992;6:5–1215 Kennedy DW. Prognostic factors, outcomes and staging inethmoid sinus surgery. Laryngoscope 1992;102:1–1816 Levine H, May M. Rhinology and Sinusology. New York:Thieme Medical Publishers, 199317 Lund VJ, Mackay IS. Staging in rhinosinusitis. Rhinology1993;31:183–418 Gliklich RE, Metson R. A comparison of sinus computedtomography (CT) staging systems for outcome research.Am J Rhinol 1994;8:291–719 Lund VJ, Wright A, Yiokas J. Complications andmedicolegal aspects of endoscopic sinus surgery. J R SocMed 1997;90:422–820 Stewart MG, Sicard MW, Piccirillo JF, Diaz-Marcha PJ.Severity staging in chronic sinusitis: are CT scan ￿ndingsrelated to patients symptoms? Am J Rhinol 1999;13:161–721 Bhattacharyya T, Piccirillo J, Wippold FJ. Relationshipbetween patient-based descriptions of sinusitis and para-nasal sinus computed tomographic ￿ndings. Arch Otolar-yngol Head Neck Surg 197;123:1189–9222 Havas TE, Motbey JA, Gullane PJ. Prevalence ofincidental abnormalities on computerized tomographicscans of the paranasal sinuses. Arch Otolaryngol HeadNeck Surg 1988;114:856–923 Lloyd GAS. CT of the paranasal sinuses: study of a controlseries in relation to endoscopic sinus surgery. J LaryngolOtol 1990;104:477–8124 Gwaltney JM, Phillips CD, Miller RD, Riker DK.Computed tomographic study of the common cold. NEngl J Med 1994;330:25–3025 Cooke LD, Hadley DM. MRI of the paranasal sinuses:incidental abnormalities and their relationship to symp-toms. J Laryngol Otol 1991;105:278–8126 Leopold DA, Stafford CT, Sode W, Szeverenyi NM,Allison JD, Phipps RJ, et al. Clinical course of acutemaxillary sinusitis documented by sequential MRI scan-ning. Am J Rhinol 1994;8:19–28Address for correspondence:Professor V. J. Lund,Institute for Laryngology and Otology,University College London,330 Gray’s Inn Road,London WC1X 8DA, UK.Fax: +44 (0)20 7833 9480TABLE IIIincidence of anatomical variants on ct for chronicrhinosinusitis1,7–11%Concha bullosa 17–30Everted uncinate process 5–21Pardoxical middle turbinates 3–26Haller (Infra-orbital) cells 4–15Agger nasi pneumatization 14–42Onodi (spheno-ethmoidal) cells 5–12radiology in focus 397

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