表现为眼眶（炎性）假瘤的视神经束膜炎

　　DISCUSSION

　　Opticperineuritis（OPN）isalsoknownasperiopticneuritis,anddescribesinflammationofopticnervesheathwithoutinflammationoftheopticnerveitself[4,5].Theinflammationisassumedtoaffecttheopticnervesheathonlywhenthereisevidenceofopticnervedysfunctionwithnormalintracranialpressure[5].Recently,theopticperineuritishasbeenfocusedontheidiopathicinflammatoryresponseofopticnervesheath[4,5].Opticperineuritisoccasionallyoccursasamanifestationofspecificinfectiousorinflammatorydisorder,eg.Wegenergranulomatosis,giantcellarteritisorinitialpresentationofsarcoidosis[6,7].

　　Opticperineuritisisararepresentationanditisonesubclassificationofidiopathicorbitalinflammationororbitalpseudotumor[1].Otherorbitalstructuresthatmaybeinvolvedarelacrimalgland（dacryoadenitis）,extraocularmuscles（myositis）,sclera（scleritis）ororbitalfat[1].IdiopathicorbitalinflammationinvolvingtheorbitalapexiscalledTolosoHuntsyndrome[1].Ittypicallyproducedpainfulexternalophthalmoplegiaregardlessofcavernoussinusinvolvement[1].Acuteonsetoforbitalpain,limitedocularmotilityandproptosisarecharacteristicpresentationsofidiopathicorbitalinflammationafterexcludingothersecondaryinflammationsorinfections[1].Somepatientsdonotpresentclassicalsignsandsymptomsoforbitalpseudotumor,makingorbitalimagingavitallyimportantinvestigationtoascertainthediagnosis[1].Asinourcase,patientpresentedwithminimalinflammationofconjunctivawithmarkedlyreducedopticnervefunctionandocularmotility.However,therewasnosignofproptosis.So,clinicallyitwasdifficulttodistinguishbetweenopticperineuritisandretrobulbaropticneuritis.MostofclinicalfeaturesofpatientwithOPNarealsolikelytobemisdiagnosedofhavingopticneuritis（ON）[4].However,demographicdataofopticperineuritisshowmostpatientswithOPNarewomenwithbroaderrangeofage（36%aremorethan50yearsold）[4].ThemeanageofOPNpatientsisolderthanpatientswithopticneuritis[4].PatternofvisuallossisalsodifferentinapatientwithOPNcomparedtoON.InOPNpatientvisuallossprogressesoverseveralweeksbeforethecorrectdiagnosisismadeandcommonlyhassparingofcentralvision[4],whileinONpatientthevisuallossprogresseswithinfewdaysandsparingofcentralvisionislesscommon.

　　InOPN,theinflammationofextraocularmusclecausesmotilitydisturbanceasoccurredinthispatient.OthersignsthatmayhelptodiagnoseOPNaresubtleptosis,chemosisanddiplopia（orbitalinvolvement）[4].IncontrasttoONpatient,abnormaleyemotilityandtheothersignsmentionedarenottypicalfeaturesunlessitisassociatedwithbrainsteminvolvementduetomultifocaldemyelinatingdisease[5].However,somepatientswithOPNalsodonothaveanyproptosisorophthalmoplegiawhichmimicretrobulbaropticneuritis[8,9].

　　ThediagnosisofOPNistypicallybasedoncombinationofclinicalandradiographicimagingfindingsparticularlymagneticresonanceimaging（MRI）[4].OpticnervebiopsyisnotindicatedinmostcasesofsuspectedOPN[1,4].ThecharacteristicpatterninneuroimagingofOPNtypicallyshowsenhancementofopticnervesheath（“tramtrack”onaxialviewand"doughnut"oncoronalview）asfoundinourpatient[4].Therewaspresenceofstreakyenhancementoforbitalfat[9]anditwasalsofoundinherMRI.InanotherpublishedcasereportofOPN,MRIshowedenhancementofopticnervesubstanceduetoinflammationofintraneuralpialseptaandopticnervesheath[9].ThesechangesinneuroimagingarenotfoundinpatientswithtypicaldemyelinatingON.ThoseradioimagingfindingsarebestobtainedfromMRIscansspecificallytheuseofdedicatedorbitalviewswithfatsuppressionandgadolinium[9].Computedtomographicscanning,however,doesnotusuallygiveadequatespatialresolutiontodistinguishperineuralenhancementfromintraneuralenhancementasfoundindemyelinatingON[4].Furthermore,thehighresolutionCTimagingisassociatedwithradiationexposureandmayputrisktoothermortalityormorbidityduetoiodinatedcontrast[9].

　　ItisimportanttodifferentiatebetweenOPNandONfortworeasons.Thetreatmentandprognosisaredifferent.PatientwithOPNwillrespondtocorticosteroidsorantiinflammatoryagentsandmayneedtoprolongthetreatmenttopreventrecurrence.Ifnottreated,thepatientwillcontinuetolosevision.IncontrastwithON,thetreatmentismorecontroversial[10].

　　CorticosteroidshavenotbeenproventoinfluencethevisualoutcomeandmanypatientsdidnotreceivethetreatmentinOPN.Therouteofadministrationanddosagearealsodifferent.InOPN,oralcorticosteroidwiththedosageof80mg/dayisrecommendedbutcontraindicatedinONbecauseitmayincreasetherateofrecurrenceofopticneuritis[11].ThecourseofcorticosteroidtreatmentinONisshorter（twoweeks）butitisnotlongenoughforOPN.

　　TheprognosisofOPNisgenerallyexcellent[4].ThepatientshavingOPNarenotatriskofdevelopingmultiplesclerosisbutarelikelytohaverecurrentvisuallossinfuture.ComparedtoONpatients,theyareathighriskofdevelopingmultiplesclerosisandneedtocounsel.

　　Inconclusion,opticperineuritisisararepresentationofidiopathicorbitalinflammationsyndromethatclinicallymaymimicretrobulbaropticneuritis.Earlydiagnosistodifferentiatethetwoclinicalentitieswillresultinbettermanagementandimprovethevisualprognosis.

　【参考文献】

　1AmericanAcademyofOphthalmology.Basicandclinicalsciencecourse:orbit,eyelids,andlacrimalsystem.Section7.SanFrancisco:AAO;20022003

　　2NobleSC,ChandlerWF,LloydRV.Intracranialextensionoforbitalpseudotumor:acasereport.Neurosurgery1986;18:798801

　　3KayeAH,HahnJF,CraciumA,HansonM,BerlinAJ,TubbsRR.Intracranialextensionofinflammatorypseudotumoroftheorbit.Casereport.JNeurosurg1984;60:625629