Review
Paper
Head
and
Neck
Oncology
Extracranial
primary
and
secondary
meningiomas
GiorgioIaconetta,AntonioSantella,MarcoFriscia, VincenzoAbbate,LuigiCalifano: Extracranialprimaryandsecondarymeningiomas. Int.J.OralMaxillofac.Surg. 2012;41:211–217. #2011InternationalAssociationofOral andMaxillofacial Surgeons.PublishedbyElsevierLtd. Allrights reserved.
GiorgioIaconetta1,
AntonioSantella2,MarcoFriscia2, VincenzoAbbate2,LuigiCalifano2
1DepartmentofNeurosurgery,Schoolof Medicine,UniversityofNaples‘FedericoII’, Naples,Italy;2DepartmentofOraland Maxillo-FacialSurgery,SchoolofMedicine, UniversityofNaples‘FedericoII’,Naples,Italy
Abstract. Meningiomaisawell-recognizedtumourofthecentralnervoussystem. However,extracranialnon-duralorectopicmeningiomasarerareandinmostofthe reportedcases,meningiomasarediagnosedonlyafterhistopathologicexamination. Overthelast5years,theauthorshaveseenthreecases.Inthesecasereports,they discussthesalientfeaturesoftheselesions,whichcanaidthepreoperativediagnosis andmanagementofthesepatients.Oneofthecasesisararity,owingtotheextreme extracranialpositionwhichallowedthepressureofthetumourabradetheadjacent structures.Inonecase,reconstructionoftheskullboneusingpolymericmaterials (Acrylicmatter)wasnecessary.Intheothertwocases,titaniumplatesandscrews wereusedtoreconstructthejaw.
Keywords: extracranial meningioma; skull basemeningioma;ectopicmeningioma. Acceptedforpublication31August2011 Availableonline9November2011
Meningioma is a common intracranial tumourwithavarietyofhistomorphologic growthpatterns,whichareusuallyeasily recognized7.Theirextracraniallocationis rare but two categories can be distin-guished:primaryandsecondary extracra-nialmeningiomas.Theprimarytypearises from either displaced embryonic ara-chnoid cells or from multipotential mesenchymal cells, and the secondary type arises as a direct extension of an intracranial mass. Primary extracranial (ectopic, extracalvarial) meningiomas of thenasalcavity,temporalbone,paranasal sinuses, and nasopharynx (hereinafter referred to collectively as the sinonasal tract)areveryrare.
Theliteratureisgenerallylimitedto iso-lated case reports2,4,10,13,14 with a few reviews3. Histologically, meningiomas of thesinonasaldistrictareidenticaltotheir intracranialcounterparts,although diagnos-ticdifficultiesarefrequentlyencounteredin
thedifferential diagnosiswithcarcinoma, melanoma, and olfactory neuroblastoma resulting from therarity of meningiomas inthislocation.
Meningiomasrepresentabout20–30% ofallprimitiveencephalictumours.They probablyarisefromthemeningeal cover-ings,andarachnoidalcapcellsofthebrain andspinalcordand1–2%havean extra-craniallocation1.Possiblemechanismsfor extracranial meningioma have been pro-posed8,20.
Themostfrequentsitesofan external mass are the orbit, the outer table and scalp, the paranasal sinuses, the nasal cavity, the parotid and parapharyngeal region. It has been estimated that about 20% of intracranial meningiomas could develop an extracranial extension, and themostcommonsiteistheorbit. Follow-ing invasion of the temporal bone, the mostcommonextensionrouteisthrough thejugularandlacerateforaminaintothe
nasopharyngeal,retromaxillary, retroman-dibular and cervicalspaces, whilst inva-sionoftheexternalauditorycanalisvery uncommon5,18.Extensionthroughthe for-amina rotundum, spinosum and ovale, such asthe pterygomaxillaryfissure, the sphenopalatine foramenandthe pterygo-palatinecanalisrare.Whenmeningiomas occurintheheadandneck,thediagnosis and management often represent a great challenge.
Thedifferential diagnosis of extracra-nial meningiomas includes a variety of benignandmalignantneoplasms, includ-ing epithelial tumours (carcinoma), neurogenictumours(melanomaand olfac-tory neuroblastoma), vascular tumours (angiofibroma, paraganglioma), and mesenchymal tissue tumours (aggressive psammomatoid-ossifyingfibroma)22.
According to the WHO classification thereare15histologicsubtypesof menin-giomas(Table1).Amongstthesesubtypes,
doi:10.1016/j.ijom.2011.08.005,availableonlineathttp://www.sciencedirect.com
meningothelial, fibrous and transitional (mixed)arethemostcommon.The prog-nosticsignificanceofthesesubtypesisvery low,althoughsomesubtypes,suchasclear cellmeningiomasandpapillary meningio-mas, areclinically aggressive; 2–10%of thesetumoursaremalignant.
Meningiomasaresoft,smooth-surfaced masseswithabroadduralattachment;the microscopicfindingsshowlobulesof neo-plastic cells creating a syncytial appear-ance,andfibroustissueistypicallyscant. Thecellsshowroundtoovalnuclei, deli-catechromatin,smallsolitarynucleoli,and often nuclear-cytoplasmic invaginations calledpseudoinclusions(syncytialvariant). Thetransitionalvariantdemonstrates pro-minentlobules,whorls,collagenizedblood vessels, and psammoma bodies. The fibrous variant is generally less cellular andconsistsofelongatedcellsimmerged inacollagen-richmatrix.Theclassic ultra-structuralfindingsshowinterdigitating pro-cesses, well-formed desmosomes and hemidesmosomes.Atypicalandmalignant meningiomas demonstrate hypercellular-ity, necrosis, sheet-like growth and the cytologic findings include high nuclear-cytoplasmicratios,coarsechromatin, pro-minentnucleoli,andhighmitoticactivity. The clinical and radiographic features of these tumours are non-specific, and consequently an accurate diagnosis requires histologic evaluation. Histologi-callyandimmunophenotypically, extracra-nial meningiomas are the same as their intracranial counterparts. An awareness ofthesepathologicand immunohistochem-icalfeaturesshouldallowthemtobe dis-tinguished from other sinonasal tract tumours. The clinical manifestations, radiographic findings, andhistologic fea-tures cannotpredicttheclinical outcome
accurately, even though, with complete surgicalextirpation,sinonasaltract menin-giomashaveagoodoverallprognosis23.
Duringthelast5years,theauthorshave observed three cases of extracranial meningiomas. They discuss the salient features ofthese lesions, which can aid the preoperative diagnosis and manage-mentofthesepatients.
Casereports
Case1
A 75-year-old female patient presented with progressive swelling overthe right sideoftheouterheadandtemporalregion. It was associated with local pain and progressiveproptosis.Shedeniedvertigo, imbalanceortinnitus.Hermedicalhistory was unremarkable. On examination, she hada6cm,firm,nontender, noncompres-sible swelling on the right temporal
region, fixed to the underlying bone. The skin over the swelling was normal andtheunderlyingmasscouldbepinched off(Fig.1).There wereno other neuro-logicalsymptomsordeficits.Neurologic examination,including evaluation ofthe cranialnerves,andheadandneck exam-inationwerenormal.Computed tomogra-phy (CT), before and after contrast administration,showedalargeenhancing extracraniallesionlocatedintothe infra-temporalfossa; theunderlyingbonewas irregular and soft in places and it was infiltratedbythetumour(Fig.2).
Anemicoronalskinincisionwasmade onthe rightside(Fig.3a)anddissection revealedthetumour(Fig.3b).The tempor-alismusclewas extensivelyinfiltratedby the neoformation, so it was completely removed. The lesion was removed (Fig.3c).Itwasalsonecessarytoremove partofthetemporalbone,whichwas par-tiallydestroyedbythetumour.This extre-melyrare presentation revealed a totally extracranial meningioma the pressure of whicherodedthebone.Skullbone recon-structionwas performedusingpolymeric materials(Acrylic)andfixedusingtitanium platesandscrews.3weekslater,theAcrylic matterwasremovedduetoaninfection.
A good postoperative outcome was achieved.Nonewsymptomsdeveloped1 yearaftersurgery.Thepatientisstill under-going6-monthfollow-up.Histopathology ofthetumourtissueshowedmeningothelial meningioma(Fig.3d)withwhorledaspects andpsammomabodies,occasionalmitotic figures,nonuclearpleomorphismor necro-sis.Histopathological examinationofthe tumourrevealedameningiomawith sev-eralintracellularpseudoluminawithround eosinophilic periodic acid Schiff (PAS), epithelial membrane antigen (EMA) and carcinoembryonicantigen(CEA)positive
Table1. WorldHealthOrganization(WHO)classificationofmeningiomas.
WHOgrade Meningiomaswithlowriskofrecurrenceoraggressivegrowth
Meningothelial I Fibrous(fibroblastic) I Transitional(mixed) I Psammomatous I Angiomatous I Microcystic I Secretory I Lymphoplasmacyte-rich I Metaplastic I
Meningiomaswithgreaterlikelihoodofrecurrenceand/oraggressivebehaviour
Atypical II
Clearcell(intracranial) II
Chordoid II
Meningiomasofanysubtypeorgradewithhighproliferativeindexand/orbraininvasion
Rhabdoid III
Papillary III
Anaplastic(malignant) III
Fig.1. Case1.A75-year-oldfemalepatientpresentedwithswellingovertherightsideofthe outerheadandtemporalregion.
bodies, so-called pseudopsammomabo-dies.Thetumourwasaprimary extracra-nialmeningiomawithoutanyintracranial connexion.
Case2
A 65-year-old female patient presented withnew-onsetheadaches,facialsensory disturbance (second division of the tri-geminal nerve), and airflow reduction
through the left nostril. She complained oflefthypoacusiaandvisualreductionof the left eye. The visual field showed a deficitintheleftlowerquadrantand ultra-sound of the orbit showed retrobulbar optic neuritis. Magnetic resonance ima-gingshowedabnormal enhancementand wideningoftheleftpterygopalatinefossa and sphenoidal sinus and omolateral cavernous sinus. Alesion extended into the middle cranial fossa (Fig. 4a). The
patient was subjected to surgical partial removalofthelesionthroughaleft fronto-temporalapproach.
The tumour was forcibly removed in part, because ofthe extentof thelesion withinthecavernoussinusandsphenoidal sinusandtheinvolvementoftheinternal carotidartery(Fig.4b).Asecond opera-tionwasperformed3weekslaterbecause ofthe tumourextension within the pter-ygopalatinefossa(Fig.4c).
Azig–zagshapedskinincisionfromthe inferior lip to the chin to the ipsilateral mastoidwasused(Fig.5a).Theoralfloor wasalsodissectedandthefacialarteryand vein were exposed. The authors made a para-medianosteotomyofthejawonthe left side, the soft tissues were dissected until,inthelateral pharyngealspaceand inthepterygopalatinefossa,a large, red-brown, hard,elastic neoplasiawas found (Fig. 5b and c). It was not possible to remove the lesion en block, because it wasstronglyfixedtothecranialbase, pene-tratingthecavernoussinusanditinvolved theinternalcarotidartery,soapiecemeal removalwasperformed.Osteosynthesisof the jaw was carried out using titanium plates and screws.Histopathology ofthe tumourtissueshowedcellular pleomorph-ism, nuclear atypia,macronucleoli,small cellformation,sheeting,atypicalmitoses, and necrosis. Histopathological examina-tion of the tumour revealed an atypical meningioma (WHO grade II) (Fig. 5d). Radiotherapy was performed and at the 3-yearfollow-upthepatienthadno neuro-logicalsymptoms(Fig.6).Inthiscasethe extracranial location was a secondary extensionoftheintracranialmeningioma.
Case3
In 1999,a 62-year-old malepatient pre-sentedwithmotorandnominumaphasia, left hypoacusia andtinnitus,pierced-type headache,reductionofvisioninbotheyes and hypostenia ofthelegs,whichled to difficultiesinambulationparticularlywith therightleg.HeunderwentCTandMRIof thebrain.MRIrevealedatumourmassof 3.5cm,enhancedaftercontrastmediumin correspondencewiththelefttemporalpole. Thelesionwasexcisedusingaleft fronto-temporal approach (Fig. 7a and b). The lesionappearedlargelycalcifiedand presented features of meningioma. The histopathological findings suggested a fibroblasticmeningioma.Inthe postopera-tive period, the motor aphasia and the deficit oftherightlegdecreased, butthe nominumaphasiapersisted.6yearslater,in 2005,aneurologicalexaminationrevealed apersistenceofaphasianominumandleft
Extracranialmeningioma
Fig.3.Case1.(a)Theskinmarkedtoshowthelineoftheskinincisionontherightside;(b) intraoperative view ofthe lesion exposed; (c) the lesion removed;(d) histological section (HematoxylinandEosin10)ofthetransitionalmeningiomainfiltratingsoftandmusculartissues. Fig.2. Case1.AxialCTwithcontrastshowingalargeenhancingextracraniallesionlocated intothetemporalandinfratemporalfossa;theunderlyingboneisirregularandsoftinplacesand infiltratedbythetumour.
hypoacusia, and an MRI of the brain showedarecurrenceofthelesion confirm-ing the presence, on the left side, of a temporo-polar neoformation, about 2.5cminsize.Thepatientunderwent cra-niotomyandthetumourmasswasremoved. A fronto-temporalapproach wasused on theleftside.Asintheprevioussurgery,the lesion was moderately vascularized andinfiltratedtheduramaterofthegreat
sphenoidwingandthetemporalfossa.The neoformationappearedroundish, grey–yel-lowandsoftinconsistency.Itwasremoved stepbystep,usingbipolarpliers.Wherethe floorofthemiddlefossawas eroded,the dura mater seemed infiltrated: so it was removed and replaced by a pericardial patch. Histopathological examination of the tumourrevealed atypical transitional meningioma. Postoperatively the aphasia
nominum regressed, but the hypoacusia persisted. After a period of good health, in 2006 a follow-up contrast enhanced CTscanofthebrainshowedaneoformation intheupperportionofthenasalfossa,the pterygomaxillaryfossaandthesphenoidal sinus(Fig. 7c). The bonewas eroded. A different approach was necessary and a mandibular osteotomy was performed to exposethelesioninthepterygomaxillary fossa (Fig. 8). Using an endoscopic approachinthenasalcavity,aturbinectomy andremovaloftheneoformation,located betweenthemiddleturbinateandthenasal septum,wasperformed.Thejawwasfixed using titanium plates and screws. Histo-pathological examination of the tumour revealedarhabdoidmeningiomaandsome areasofnecrosis(WHOgradeII)(Fig.9). Radiotherapywasperformed(Fig.10).This casewasasecondaryextracranialextension ofanintracranialmeningioma.
Discussion
Meningiomasarebenigntumoursderived fromthearachnoidvillousstructuresofthe meningesandarecommon inthecentral nervoussystem23.Extracranial meningio-masarevery rareincomparisontoaxial lesions,andtheincidenceof extracranial-extra-axialmeningiomasrangesfrom1% to2%ofallmeningiomas.Theyhavebeen reportedsporadically. HOYE et al.16
sub-classified extracranial meningiomas on thebasisofthemajoraetiologiesproposed concerning their development, and the most common variety of extracranial meningioma, is that which arises from intracranial dura and extends extracra-nially8.About40%ofthese,developfrom thesphenoidal region intothe orbitwith associatedhyperostosisofboneandwith proptosis and progressive visual impair-ment.Theliteratureindicatesthat extracra-nial meningiomas show a slight female predominance,1:1.2,approximately55%, and males have a worse prognosis. The averageageatpresentationfortheauthors’ patients(67.3years) wasnotinlinewith those reported in the literature (43.4 years).Thereisastatisticallysignificant differencein theageat presentationfor thefemalepatientsinthepresentseries, whowereonaverage(70.0years),older thantheirmalecounterparts(62.0years), comparingtheaverageageofthefemales (48.7 years) and males (36.9 years) reported in the literature. Extracranial meningiomashave beenobserved tobe benignandslowgrowing.
This diagnosis is rarely considered beforesurgicalremovaland histopatholo-gicexamination,becauseofitsrarity,and
Fig.5. Case2.(a)Thezig–zagshapedskinincisiontoperformthetransmandibularapproach; (b) exposure of the tumour mass within the pterygopalatine fossa (arrow); (c) the lesion removed;(d)histologicalsection,immunostainingKi-67antigen/Monoclonalmouseantibody (MIB-1)(40),showinghighcellularproliferativeindex.
Fig.4. Case2.(a)MRI,T1-weighted,incoronalviewaftercontrastadministrationshowingthe tumourmassintheleftmiddlefossa,cavernoussinusandpterygopalatinefossa;thecarotid artery is surrounded by the tumour; (b) MRI, T1-weighted, showing the removal of the intracranial lesion byafronto-temporalapproach; (c) axialCTshowing thelesion located withinthepterygopalatinefossa.
theabsenceofclearradiologicalfindings in favour of a meningioma, specially regarding the primary truly extracranial lesions,lackinganydetectableintracranial massorduralattachmentandtheir often non-specificclinicalfindingscomparedto the other more commontumours ofthe softtissues.Thepatienthastobecarefully observedandtheshapeofthelesion,the swelling, thepain withor without com-pression,andtheunderlyingtissuefixation have to beexamined. The skinoverthe swelling isevaluated andtheunderlying massispinched off.Neurological symp-tomshavetobeestimated,including eva-luationofthecranialnervesandheadand neckexamination.Whenthereis involve-mentoftheorbit,itisnecessary to esti-matevisualacuity,whilstinvolvementof
the ear is analysed by audiometry. In general, the most common symptoms are headache, vertigo,and seizures. The differentialdiagnosisofotological symp-toms caused by middle ear tumours includes cholesteatoma, adenoma, para-ganglioma, adenocarcinoma, lymphoma ormetastatic carcinoma.
TheroleofCTwithcontrastmediumis verysignificant andreveals the relation-ship between the tumour and the bony surfaces, the temporal bone, sphenoid ridge, and lateral wall of the orbit, and the possibility of a malignant tumour involving the temporalis muscle and/or bone.MRIallowsastudyofthe vascular-ization, infiltration,extension,limitsand relationships with the brain parenchyma andsurroundingstructures.
Surgicalexcisionisthegoldstandardof treatmentandmustbeplannedby radiolo-gicstudiestodeterminetheextentofthe tumourandthepresenceorabsence ofa companioncentralnervoussystem menin-gioma.Thisincludesremovalofthickened bone and resection ofthe dura involved alongwiththetumor6.Adequateexposure ofthe tumourandinvolved bonecan be achievedusingagenerousscalpincision. Usually, the thickened calvariumis hard butslightlysofterthanthenormalboneand canberemovedeasily.Ifpossible,thishas tobeaccompaniedbyremovalofan ade-quate margin of normal bone. A dural defect can be closed using pericranium harvested from the adjoining region or, alternatively, avascularizedpedicle peri-cranialflapcanbeused19.Atsurgery,the skincanbeseparatedfromthetemporalis fasciaeasily.Afirm,fleshy,highlyvascular tumour infiltratingthetemporalis muscle and densely adherent to the underlying boneisidentifiedanddetachedallaround, along with muscle from the underlying bone,andtogainaccesstothe infratem-poralpartofthetumour,lateral orbitozygo-matic osteotomy is performed. Bony defects can be closed by artificial graft material(polydioxanonsheet)orwith vas-cularizedpediclepericranialflapsbasedon temporalismuscleanditsfasciallayer.If thefrontalsinusesareinvolved,theyshould be excluded from the cranial cavity by cranialization. Although there are occa-sionalreportsofcompleteremissionafter radiationtherapy,surgicalresectionisthe treatmentofchoice.Thedifferentbenign andmalignantlesionsarisinginthisregion includerhabdomyosarcoma, hemangioper-icytoma,chondroblastoma, hyperparathyr-oidism, and fibrous dysplasia. The pathologicfeaturesofextracranial menin-giomasareidenticaltothoseofmore fre-quent intracranial lesions. Preoperative suspicionofameningiomainthesepatients wouldhaveresultedinamoreaggressive surgicalapproach.Recurrenceof intracra-nial meningiomas occurs usually in the primary site and less commonly at the surgicalscar,thereforetheextentof surgi-calexcisionisprobablythemostimportant factorindeterminingoutlook,inorderto decreaserecurrence.Thesurgicalstrategy for primary and secondary extracranial meningiomasisdifferent.Thefirsthasto betreatedasacommontumourofthesoft tissues and the target is to attempt total removal.Secondaryextracranial meningio-masareextensionsofintracraniallesions, migratingthroughtheforaminaoreroding theboneoftheskull,ofteninvolvingvital neurovascularstructures.Aftercraniotomy andtheremovaloftheintracranialportion,
Extracranialmeningioma
Fig.7. Case3.(a)MRI,T1-weighted,axialviewshowingthetumourmass withintheleft middlefossadisplacingthetemporallobe,thecarotidarteryisencasedbythetumour(arrow); (b)MRI,T1-weighted,inaxialview,showingtheremovalofthetumourthroughaleft fronto-temporalapproach;(c)axialCTshowingthetumourmassextendingwithintheleft pterygo-palatinefossa.
Fig.6. Case2.Thepatientinfrontal(a)andlateral(b)view2monthsaftersurgery.Thescaris cosmeticallyacceptableandthereisnofacialnervedeficiency.
generallyatransfacialapproachhastobe performedtoextirpatetheextracranial por-tion.Theextentofsurgerydependsonthe boneerosionduetothetumour,itssize,and degreeofinfiltrationintothesurrounding structures.
Meningiomaswithnegative histopatho-logical features, such as a high mitotic indexandnuclearpleomorphism (anaplas-ticmeningioma),haveahigherprobability ofrecurrence. It has been observed that, afterusingradiotherapy,therecurrenceof intracranial meningiomas is uncommon. Radiotherapy treatment involves post-operative, three dimensional, conformal radiotherapy to partial brain using a 6 MVlinearacceleratorwithfour non-com-planarfieldswith a doseof60Gy in30 fractionsin6weeks.Inpatientswhohave never been subjected to radiation, post-operativeradiotherapyafterrecurrencein ameningiomacanimprovecontrolrates21. Patientswhohavenotreceived radiother-apyearliercansubsequentlyreceive post-operativeradiotherapy.
Theoptimalmanagementandtheoverall prognosisofsuchrecurrences,becauseof theirrarity,areunknown.Forintracranial meningiomas, radiotherapy is frequently recommendedasasafeandreliable adjunc-tivetreatmentforpartiallyresected menin-giomas. When total resection of benign meningiomaisnotfeasible,subtotal resec-tioncombinedwithprecisetreatment plan-ning techniques and adjuvant radiation therapycanachieveresultscomparableto thoseoftotalresection.Increased progres-sion-free survival in the benign tumour groupwasalsosignificantlyassociatedwith increasing the minimum radiation dose (p=0.04)12. Studiesintheliterature pro-vide convincing evidence that radiation therapy is beneficial in the treatment of partiallyresectedmeningiomas. The role of radiotherapy for primary extracranial meningiomashasnotbeenestablished.
Intheliterature,therecurrenceratefor meningiomas after total excision varies from7%to84%,dependingonthe histol-ogyand extent ofsurgery. Theauthors’ surgeryhasbeenveryaggressivebecause thetumourinfiltratednearbystructures.In oneofthepresentcasestheauthorsuseda polymericmaterialforreconstruction,and inthiscasethepatientwasreoperatedon becauseaninfectionoccurred.
Slowlyprogressivelesionsinthe tem-poralregion,presentingduralinvolvement and contrast enhancement on CT, with extensive hyperostosis, suggest a rela-tivelybenignlesion(meningioma).These features could lead to more aggressive resection and a reconstruction of bone defects.
Fig.9. Case3.Histologicalsection(HematoxylinandEosin10)showingmeningiomatous tissueinfiltratingbonylamellae.
Fig.8. Case3.(a)Theskinmarked,showingthezig–zagshapedskinincision;(b)themandible resectedafterthepre-platinghasbeenperformed;(c)exposureofthelesion withintheleft pterygopalatinefossa(arrow).Lingualnerve(arrowhead).
Fig.10. Case3.Thepatientinfrontal(a)andlateral(b)views2monthsaftersurgery.Thescar isnotparticularlyevidentandtheleftfacialnervefunctionispreserved.
The origin of primary extracranial meningiomas remains controversial, although severaltheories have been pro-posed.Theseincludeextraduraltrappingof arachnoid cells during embryogenesis, ectopic migration of the arachnoid cell nests with the developing peripheral nerves,andmetaplasiaofthemature per-ipheral nerve sheath cells or progenitor cells.HOYEetal.16subclassified
extracra-nialmeningiomasonthebasisofthemajor aetiologiesproposedinthedevelopmentof extracranial meningiomas, and the most commonvarietyofextracranial meningio-masisthatwhicharisesfromintracranial duraandextendsextracranially9.Thereare anumberofdifferentmechanismsto sug-gest how extracranialmeningiomas arise and develop8,9,15, including: arachnoidal cellsareevidentinthesheathsofthenerves andvesselswheretheyemergethroughthe skull foramina; displaced pacchionian bodies becomedetached, pinched off, or entrapped during embryologic develop-mentinanextracraniallocation;anorigin from undifferentiated or multipotential mesenchymal cells, such as fibroblasts, Schwanncells,oracombinationofthese, perhapsexplainingthediversepathologic spectrumfoundinmeningiomas;traumatic events or cerebral hypertension that dis-placearachnoidislets.
Byone ormore ofthesemechanisms, arachnoid cells are identifiedoutside the neuraxis and give rise to extracranial meningiomas. Clinicopathologically,they are usually categorized in four groups, based on the suggested aetiologies pro-posedforthedevelopmentofextracranial meningiomas:directextensionofaprimary intracranialmeningiomathroughpressure necrosis/absorptionofthebone,orthrough aniatrogenicornaturalopening(including thecribriformplate);extracranial metasta-sisfromanintracranialmeningioma; extra-cranial meningioma originating from arachnoid cell clusters in the sheaths of thecranialnerves(orvessels)astheyexit throughtheforaminaorsuturelinesofthe skull,includingthecribriformplate; extra-cranialmeningiomawithoutanyapparent demonstrable connexion with foramina, cranialnerves,orcranialprimaries.
Upto20%ofintracranialmeningiomas may have extracranial/extraspinal exten-sion8,includingtheorbit,middleear,soft tissues,andskinoftheheadandneck,and upper airway involvement (nasal cavity, para-nasalsinuses,nasopharynx).Mostof thereportedcasesinvolvingtheupper air-wayrepresentsecondaryextensionfroman intracranial lesion8,10,11,13,17. Extracranial meningiomas arising from the sinonasal
tractortemporalmusclewithnoevidence of an association with an intracranial tumour (also called heterotopic, ectopic, or extracalvarial) are rare2,3,9,10,13,15,22, and most of the reported cases were describedbeforemodernradiographic ima-gingtechniqueswereavailabletoexclude intracranial tumours. There is a growing consensusthatprimaryextracranial menin-giomasaretrulyextracranial,lackingany detectable intracranial mass or ‘dural enhancement’byradiologictechniques.
In summary, the clinical and radio-graphic features of these uncommon lesions are nonspecific, hence, a precise diagnosis requires histologic evaluation. The prognosis, after complete surgical extirpation, is generally good with dis-ease-freesurvivalratesof82%and78% at5and10years,respectively23. Competinginterests Nonedeclared. Funding None. Ethicalapproval Notrequired. References
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Address: MarcoFriscia
DepartmentofOralandMaxilloFacial Surgery
UniversityofNaples‘FedericoII’ ViaPansini5 Napoli80100 Italy Tel:+390817462075 E-mail:marcofriscia@yahoo.it Extracranialmeningioma
