The anatomic analysis of the vidian canal and the surrounding structures concerning vidian neurectomy using computed tomography scans

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www.bjorl.org

Brazilian

Journal

of

OTORHINOLARYNGOLOGY

ORIGINAL

ARTICLE

The

anatomic

analysis

of

the

vidian

canal

and

the

surrounding

structures

concerning

vidian

neurectomy

using

computed

tomography

scans

夽

Gülay

Ac

¸ar

a,∗

_,

_Aynur

_Emine

_C

_¸ic

_¸ekcibas

_¸ı

a

_{, ˙Ibrahim}

_C

_¸ukurova

b

_,

Kemal

Emre

Özen

c

_,

_Muzaffer

_¸eker

_S

a

_{, ˙Ibrahim}

_Güler

d

a_Necmettin_Erbakan_University,_Meram_Faculty_of_Medicine,_Department_of_Anatomy,_Konya,_Turkey

b_Health_Sciences_University,_Izmir_Tepecik_Trainig_and_Research_Hospital,_Department_of_{Otolaryngology-Head}_and_Neck_Surgery, Izmir,Turkey

c_Katip_C_¸elebi_University,_Faculty_of_Medicine,_Department_of_Anatomy,_Izmir,_Turkey d_Selcuk_University,_Faculty_of_Medicine,_Department_of_Radiology,_Konya,_Turkey

Received15September2017;accepted8November2017 Availableonline26December2017

KEYWORDS Intrasphenoid septum; Morphometric analysis; Pterygoidprocess pneumatization; Vidiancanal; Vidianneurectomy Abstract

Introduction:Thetypeofendoscopicapproachchosenforvidianneurectomycanbespeciﬁed

byevaluatingthevidiancanalandthesurroundingsphenoidsinusstructures.

Objective:Thevariationsandmorphometryofthevidiancanalwereinvestigated,focusingon

thefunctionalcorrelationsbetweenthemwhicharecrucialanatomicallandmarksfor

preoper-ativeplanning.

Methods:This study was performed using paranasal multidetector computed tomography

imagesthatwereobtainedwithasectionthickeningof0.625mmof250adults.

Results:The distributionsof500vidian canalvariants werecategorized asfollows;Type 1,

withinthesphenoidcorpus(55.6%);Type2,partiallyprotrudingintothesphenoidsinus(34.8%);

Type3,withinthesphenoidsinus(9.6%).Thepneumatizationofthepterygoidprocessismostly

seeninvidiancanalType2(72.4%)andType3(95.8%)(p<0.001).Themeandistancesfromthe

vidiancanaltotheforamenrotundumandthepalatovaginalcanalweregreaterinthevidian

canalType2and3withthepterygoidprocesspneumatization(p<0.001).Theprevalenceofthe

intrasphenoidseptumbetweenthevidiancanalandthevomerinecrestandlateralattachment

whichendingoncarotidprominenceweremuchhigherinvidiancanalType3thanothertypes

(p<0.001).Themeananglebetweentheposteriorendofthemiddleturbinateandthelateral

marginoftheanterioropeningofthevidiancanalwasmeasuredas33.05±7.71◦.

夽 _Please_cite_this_article_as:_Ac_¸ar_G,_C_¸ic_{¸ekcibas¸ı}_AE,_{¸ukurova ˙I,}_C _Özen_KE,_S_¸eker_M,_{Güler ˙I.}_The_anatomic_analysis_of_the_vidian_canal_and

thesurroundingstructuresconcerningvidianneurectomyusingcomputedtomographyscans.BrazJOtorhinolaryngol.2019;85:136---43.

∗_{Corresponding}_author.

E-mail:gulayzeynep73@gmail.com(G.Ac¸ar).

PeerReviewundertheresponsibilityofAssociac¸ãoBrasileiradeOtorrinolaringologiaeCirurgiaCérvico-Facial. https://doi.org/10.1016/j.bjorl.2017.11.008

1808-8694/©2017AssociaçãoBrasileiradeOtorrinolaringologiaeCirurgiaCérvico-Facial.PublishedbyElsevierEditoraLtda.Thisisanopen accessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).

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Conclusions: Preoperativeradiologicanalysis ofthevidian canal andthesurrounding

struc-tureswillallowsurgeonstochooseanappropriateendoscopicapproachtoensurepredictable

postoperativeoutcomes.

by Elsevier Editora Ltda. This is an open access article under the CC BY license (http://

creativecommons.org/licenses/by/4.0/). PALAVRAS-CHAVE Septointraesfenoidal; Análise morfométrica; Pneumatizac¸ãodo processopterigoide; Canalpterigoideo; Neurectomiado pterigoideo

Avaliac¸ãoanatômicadocanalvidianoeestruturasadjacentesportomograﬁa computadorizadaparaaneurectomiadovidiano

Resumo

Introduc¸ão: Otipodeabordagemendoscópicaparaaneurectomiadovidianopodeserdeﬁnido

pelaavaliac¸ãodocanaldovidianoedasestruturasadjacentesaosseiosesfenoidais.

Objetivo: Investigar as variac¸ões e a morfometria do canal vidiano com enfoque nas suas

correlac¸ões funcionais, pois são parâmetros anatômicos cruciaispara o planejamento

pré-operatório.

Método: Esseestudofoirealizadoutilizando-seimagensdetomograﬁacomputadorizada

multi-detectoresdosseiosparanasaiscomespessuradecortede0,625mmobtidasde250indivíduos

adultos.

Resultados: A distribuic¸ão das 500 variantes do canal vidiano foi categorizada daseguinte

forma:Tipo1,dentrodocorpoósseoesfenoidal(55,6%);Tipo2,protrusãoparcialnointeriordo

seioesfenoidal(34,8%);Tipo3,nointeriordoseioesfenoidal(9,6%).Apneumatizac¸ãodo

pro-cessopterigoidefoiobservadaprincipalmentenocanalvidianoTipo2(72,4%)eTipo3(95,8%)

(p<0,001).Asdistânciasmédiasdocanalvidianoatéoforameredondoeocanalpalatovaginal

forammaioresnocanalvidianodoTipo2e3,comapneumatizac¸ãodoprocessopterigoide

(p<0,001).Apresenc¸adoseptointraesfenoidalentreocanalvidianoeacristavomerianaea

extensãolateral,queterminanaproeminênciadacarótida,foimuitomaiornocanalvidiano

Tipo3doquenosoutrostipos(p<0,001).Aangulac¸ãomédiaentreacaudadaconchamédiae

amargemlateraldaaberturaanteriordocanalvidianofoide33,05◦±7,71◦.

Conclusões: Aanáliseradiológicapré-operatóriadocanaldovidianoedasestruturas

circun-jacentes permitem ao cirurgião escolher uma abordagem endoscópica apropriadae prever

resultadospós-operatórios.

por Elsevier Editora Ltda. Este ´e um artigo Open Access sob uma licenc¸a CC BY (http://

creativecommons.org/licenses/by/4.0/).

Introduction

Thepterygopalatinefossa(PPF)lookslikeaninverse pyra-mid in a relatively deep inaccessible anatomical location that is formed by the perpendicular lamina of palatine bonemedially,greaterwingofsphenoidbonesuperiorly,the pterygoidprocessofsphenoidboneposteriorlyandmaxillary sinusanteriorly.1_The_various_osseous_{communications}_of_the

PPF formsrecognizableanatomical landmarkson Multide-tector Computed Tomography (MDCT) scans that describe themarginsandopeningsofthePPF.2_From_lateral_to_medial

theforamenrotundum(FR),thevidiancanal(VC)whichis locatedinferomedialtoFRandthepalatovaginalcanal(PVC) areclinicallyimportantopeningsincludingcritical neurovas-cularstructuresintheposteriorwallofthePPF.Also,these foraminaareincloseassociationwiththesurrounding sphe-noidsinusstructures.1

Theendoscopicsurgerytoresectatumorthatlocalizes in or around the PPF and to cure the chronic vasomotor rhinitisisanalternativetotraditionalsurgicalapproachand minimizesmorbidityandthesizeoftheincision.3_Currently,

endoscopictransnasalandtranssphenoidvidianneurectomy

are performed; the success rate of both approaches can beinﬂuencedbythedifferentsurroundingsphenoid struc-ture variations such as; VC protrusion into the sphenoid sinus,intrasphenoidseptum,thepterygoidprocess pneuma-tization (PPP) and the relationship of the VC with the middlenasalturbinate.4_So,_preoperative_radiological

eval-uation of the VC corpus types and surrounding sphenoid structuresguidesthesurgeoninchoosinganappropriate sur-gicalapproach,decreasingcomplicationsduringendoscopic surgery.5

Inthisstudy,weobservedVCvariationsandstudiedthe morphometricparametersoftheVCrelatedtothe surround-ing sphenoid structures. Speciﬁcally, we focused on the relationshipbetweenthemandanalyzedthefactorswhich affecttheformationofvariousVCcorpustypesrelatingto endoscopicapproaches.

Methods

The approval of thisretrospective investigation was done by our local Ethics Committee with an approval number 2016/543 and performed usingparanasal MDCT imagesof

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Table1 Deﬁnitionsofvariationsofthevidiancanal and

thesurroundingstructures.

Variations Deﬁnitions

VCcorpustypes

Type1 Thevidiancanalwaslocatedwithin

sphenoidbonyroof

Type2 Thevidiancanalwaspartiallyprotruded

intosphenoidsinus

Type3 Thevidiancanalwastotallyprotrudedinto

sphenoidsinuswithastalk

Intrasphenoidseptumtypes

Vomerine crest-VC

Thesphenoidseptumbetweenthe

vomerinecrestandthevidiancanal

ICAS Thesphenoidseptumwhichdeviated

laterallyandattachedtothecarotid

prominence

OCS Thesphenoidseptumwhichdeviated

laterallyandattachedtotheopticcanal

Pterygoidprocesspneumatization

Existing Thesphenoidpneumatizationextendedinto

thepterygoidprocess

Not existing

Therewasnopneumatizationinthe

pterygoidprocess

VC-medialplateofthepterygoidprocessrelationship

Medial Thevidiancanalwaslocatedmediallyto

themedialplateofthepterygoidprocessor

onsameline

Lateral Thevidiancanalwaslocatedlaterallyto

themedialplateofthepterygoidprocess

Nasalseptumdeviation

Right Thenasalseptumdeviatingtoright

Left Thenasalseptumdeviatingtoleft

Absent Therewasnoseptumdeviation

250 patients who were referred to Department of Radi-ology from January 2016 to July 2016. All patients were evaluated using 128 slice MDCT scanner (Siemens, imag-ing parameters: kV, 120; mA, 160; rotation time, 0.5s; collimation,128×0.625;FOV,220mm).Multiplanar

recon-structionimages(associatedcoronalandsagittalimagesof 1mm slice thickness) were generated onthe basis of the axialimageswhichwereobtainedwithasectionthickening of0.625mm.AccordingtoapremadeprotocolonSyngoVia (Siemens,Germany)allscanswereanalyzed.The patients withapreviousparanasalsinussurgery,nasaltraumaor frac-tures,andparanasaltumorswereexcluded.

WeobservedthevariationsoftheVCcorpustypesandthe surroundingstructuresasshowninTable1.The VCcorpus typesaccordingtotherelationshipwiththesphenoidsinus werecategorizedintothreetypeswhicharebasedonYeh etal.’s4 _{classiﬁcation}_as_follows;_Type_1,_within_the

sphe-noidcorpus(Fig.1A);Type2,partiallyprotrudingintothe sphenoidsinus(Fig.1B);Type3,totallyprotrudingintothe sphenoidsinuswithastalk(Fig.1C).ThelocalizationofVC accordingtothemedialplateofthepterygoidprocess(MPP) wasdeﬁnedasmedial(includingmedialandsameline)and lateral(Fig.1AandB). The sphenoidpneumatization pat-tern (Fig. 2A),the intrasphenoid septum between the VC andthevomerinecrest(Fig.1AandC)andlateral attach-mentsoftheseptumwhichendsonthecarotidprominence (ICAS)(Fig.2B)ortheopticcanal(OCS)wereanalyzed.Also, the presence of the PPP, which was deﬁned asthe sphe-noid pneumatization extended into the pterygoid process wasobserved(Figs.1Cand3A).Thenasalseptumdeviation wasdeterminedastoright,toleftandnoseptumdeviation. AsseeninTable2,themorphometricparameters includ-ingthemeandiameterofthesphenopalatineforamen(SPF), thedistancesfromthevomerinecresttothePVCandVC, thedistancebetweentheFRandtheVCweremeasuredin coronalplane(Fig.3A).Topredictthefeasibilityofvidian neurectomy,wemeasuredthemeananglebetweenthe pos-teriorendofthemiddleturbinate(MTP)andlateralmargin oftheanterioropeningoftheVC(Fig.3BandC).Also,the lengthandthemeandiametersofthemiddlepart,anterior and posterior openings of the VC were measured in axial plane(Fig.3C).Inourstudy,afemalepatientwhowas 19-years-old hadnoleftFR(Fig.4A)andamalepatientwho was68-years-oldhadnorightFR(Fig.4B).

SPSS22(SPSS,Inc.,Chicago,IL,USA)wasusedfor statis-ticalanalysis.Forstatisticalcomparisons,Chi-squaretest, unpairedt-test,One-WayAnalysisofVariance(ANOVA)were usedandavalueofp<0.05wasconsideredsigniﬁcant.

Figure1 CoronalCTsectionsshowingthevidiancanal(thickarrow),palatovaginalcanal(thinarrow),foramenrotundum (arrow-head),pterygoidrecesspneumatization(star).(A)Bilateralvidiancanalsinsidethesphenoidcorpus(VCType1),therightvidian canallocatedlateraltomedialpterygoidplateandleftlocatedatsameline.(B)Thevidiancanalswhichpartiallyprotrudinginto thesphenoidsinus(VCType2)bilaterallylocatedatsamelinewiththemedialpterygoidplate.(C)Thevidiancanalswhichtotally insidethesphenoidsinuswithastalk(VCType3).

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Figure2 (A)CoronalCTsectionshowingtheconchaltypesphenoidpneumatizationpattern(star);(B)AxialCTsectionshowing theintrasphenoidseptumwhichdeviatedandattachedonthecarotidprominence(ICAS)(thickarrow).

Results

Inthisstudy,thepatientsconsistedof107females(43%)and 143males(57%)withamedianageof45.76±17.64yearsfor femalesand40.80±16.47yearsformales.Threevariations of VC corpus anatomy according to the relationship with thesphenoidsinuswerefoundasfollows:Type1whichwas locatedwithin sphenoidbonyroof(55.6%,278/500), Type 2whichwaspartiallyprotrudedintosphenoidsinus(34.8%, 174/500),Type3whichwastotallyprotrudedintosphenoid sinuswithastalk(9.6%,48/500). Wedeterminedthatthe numberoftheintrasphenoidseptumwithsingleseptawas 197(78.8%),withmultipleseptawas45(18%),andwithout septawas8(3.2%).Thedistributionratiosofthesphenoid septumtypeswerefoundasfollows:intrasphenoidseptum betweenVCandthevomerinecrestas13.2%(66/500), lat-eralattachmentof theseptum whichendsonthe carotid prominence(ICAS)as28.4%(142/500)andontheopticcanal (OCS)as14.4%(72/500).Also,wefoundthepatternofthe sphenoidpneumatization asthesellar type(67%) and the prevalenceofthepresenceofthePPPas39.2%(196/500). The VC mostlylocated medialto theMPP (82%,410/500) andtheprevalencesoftheseptumdeviationwerefoundas toright34.4%(86/250),toleft25.2%(63/250),noseptum deviation40.4%(101/250).ThePVCwasidentifiedin372of the500computedtomography(CT)coronalsections(74.4%). TherelationshipoftheVCcorpustypeswiththesurrounding structuresvariationsisshown inTable3.The ratiosofthe presenceofthePPP,theICAS,theseptumbetweenVCand vomerinecrest weresignificantly higherin VCType2 and 3thanType1(p<0.001,p=0.03).Also,theconcurrenceof theICASandthePPPwasstatisticallysignificant(p<0.001), asseeninTable4.

We measured the meandiameters of themiddle part, anteriorandposterioropeningsoftheVCas1.0±0.4mm, 1.9±0.6mmand1.6±0.5mm,respectively.Also,themean length of the VC was found as 12.9±1.9mm. The mean distancesfromthevomerinecresttoVCandtoPVC were measuredas13.6±1.7mmand5.9±3.9mm,respectively. The meandistance betweenVC andFRwas8.1±2.3mm, andthe meandiameterof theSPFwas3.9±0.8mm. The meanvaluefortheanglebetweentheMTPandlateral mar-gin of the anterior opening of the VC was 33.05±7.71◦.

Table2 Deﬁnitionsofthemeasurements.

Measurements Deﬁnitions

VCdiameters

Anterior Theanterioropeningofthevidiancanalon

posteriorwallofthepterygopalatinefossa

Middle Themiddlepartofthevidiancanal

Posterior Theposterioropeningofthevidiancanalon

anteriormarginoftheforamenlacerum

VClength

(A---P)

Thedistancefromtheanteriortoposterior

openingsofthevidiancanal

VClocation

PVC-vomerine crest

Thedistancefromthepalatovaginalcanal

tothevomerinecrest

VC-vomerine crest

Thedistancefromthevidiancanaltothe

vomerinecrest

VC-FR Thedistancefromthevidiancanaltothe

foramenrotundum SPFdiameter Posterior tothe middle turbinate

Thediameterbetweentheperpendicular

plateofthepalatinebone(inferior)andthe

sphenoidbone(superior)

Endoscopicendonasalapproachangle

VC-MTP Angle

Theanglebetweentheposteriorendofthe

middleturbinateandthemostlateral

marginoftheanterioropeningofthevidian

canal

Tables5and6summarizethe relationshipofthe morpho-metricmeasurementswiththe VCvariations andthePPP. According to Tables 5 and 6 the VC Type 3 and the PPP alteredthe VC-FRandVC-PVCdistancesasincreased,but theoppositewastrueforthePVC-vomerinecrestdistance, the anterior and middle diameters of the VC that were smallerinVCType3andPPP(p<0.001).

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Figure3 Morphometricmeasurements(A)CoronalCTsectionsshowingthedistancefromthevidiancanaltopalatovaginalcanal (blackdottedline)andtheforamenrotundum(whitedottedline),theseptum(thinarrow)betweenthevidiancanalandvomerine crest(thickarrow),thepterygoidprocesspneumatization(star).(B)AxialCTsectionshowingtheanglebetweentheposteriorend ofthemiddleturbinateandlateralmarginoftheanterioropeningofthevidiancanal,theanterioropeningofthevidiancanal (thickarrow)andtheposterioropeningofthevidiancanal(thinarrow).(C)CoronalCTsectionsshowingtheanglebetweenthe posteriorendofthemiddleturbinateandlateralmarginoftheanterioropeningofthevidiancanal.

Figure4 (A)CoronalCTimageof19-year-oldwomanshowingunilateralrightforamenrotundum(arrowhead,shehadnoleft foramenrotundum)andthevidiancanals(thickarrow);(B)coronalCTimageof68-year-oldmanshowingunilateralleftforamen rotundum(arrowhead,hehadnorightforamenrotundum)andthevidiancanals(thickarrow).

Table3 Therelationshipbetweenthevariationsofthevidiancanaltypesandthesurroundingstructures.

Thesurroundingstructurevariations VCtype p-Value

Type1N◦(%) Type2N◦(%) Type3N◦(%)

SSrelatedwithICA

Notexisting 223(80.2%) 105(60.3%) 30(62.5%) <0.001 Existing 55(19.8%) 69(39.7%) 18(37.5%) Pterygoidpneumatization Notexisting 254(91.4%) 48(27.6%) 2(4.2%) <0.001 Existing 24(8.6%) 126(72.4%) 46(95.8%) SSrelatedwithOC Notexisting 237(85.3%) 148(85.1%) 43(89.6%) 0.71 Existing 41(14.7%) 26(14.9%) 5(10.4%)

SSbetweenVCandVomerinecrest

Notexisting 251(90.3%) 145(83.3%) 38(79.2%) 0.03

Existing 27(9.7%) 29(16.7%) 10(20.8%)

VCrelationwithMPP

Medial 219(78.8%) 153(87.9%) 38(79.2%) 0.06

Lateral 59(21.2%) 21(12.1%) 10(20.8%)

VC,Vidiancanal;Type1,withinsphenoidcorpus;Type2,partiallyprotrudingintothesphenoidsinus;Type3,totallyprotrudingintothe sphenoidsinus;SS,sphenoidseptum;ICA,internalcarotidartery;OC,opticcanal;MPP,medialpterygoidplate.

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Table4 Therelationshipbetweenthepterygoidpneumatizationandthesurroundingstructuresvariations.

Thesurroundingstructuresvariations Pterygoidprocesspneumatization p-Value

NotexistingN◦(%) ExistingN◦(%)

SSrelatedwithICA

Notexisting 234(77.0%) 124(63.3%) <0.001

Existing 70(23.0%) 72(36.7%)

SSrelatedwithOC

Notexisting 257(84.5%) 171(87.2%) 0.40

Existing 47(15.5%) 25(12.8%)

SSbetweenVCandvomerinecrest

Notexisting 271(89.1%) 163(83.2%) 0.05

Existing 33(10.9%) 33(16.8%)

VCrelationwithMPP

Medial 333(78.0%) 477(88.3%) 0.06

Lateral 67(22.0%) 23(11.7%)

SS,sphenoidseptum;ICA,internalcarotidartery;OC,opticcanal;VC,vidiancanal;MPP,medialpterygoidplate.

Table5 Therelationshipbetweenthemorphometricmeasurementsandthevidiancanalcorpustypes.

Morphometricmeasurements Total VCtype p-Value

Type1 Type2 Type3

VCPdiameter(mm) 1.6±0.5 1.6±0.5 1.6±0.5 1.5±0.5 0.25

VCMdiameter(mm) 1.0_±0.4 1.1_±0.4 1.0_±0.4 0.7_±0.2 <0.001

VCAdiameter(mm) 1.9±0.6 2.0±0.5 1.9±0.6 1.5±0.6 <0.001

VClength(mm) 12.9_±1.9 12.9_±1.9 12.8_±1.8 13.4_±1.9 0.19

VC-MTPangle(◦) 33.05±7.71 33.15±7.86 32.58±7.76 34.14±6.57 0.44

PVC-vomerinecrestdistance(mm) 5.9_±3.9 6.4_±3.8 5.5_±4.1 4.2_±3.8 <0.001

VC-vomerinecrestdistance(mm) 13.6±1.7 13.5±1.6 13.4±1.7 14.8±1.4 <0.001

VC-FRdistance(mm) 8.1±2.3 7.1±2.1 9.3±2.0 9.8±2.2 <0.001

SPFdiameter(mm) 3.9±0.8 3.8±0.8 4.0±0.9 4.0±0.8 0.19

VC,vidiancanal;Type1,withinthesphenoidcorpus;Type2,partiallyprotrudingintothesphenoidsinus;Type3,totallyprotruding intothesphenoidsinus;VCP,posterioropeningofthevidiancanal;VCM,middlepartofthevidiancanal;VCA,anterioropeningof thevidiancanal;PVC,palatovaginalcanal;FR,foramenrotundum;SPF,sphenopalatineforamen;MTP,middleturbinateposteriorend. Mean±standarddeviation.

Table6 Therelationshipbetweenthemorphometricmeasurementsandthepterygoidprocesspneumatization.

Morphometricmeasurements Pterygoidprocesspneumatization p-Value

Notexist Exist

Mean_±SD Mean_±SD VCPdiameter(mm) 1.6±0.5 1.5±0.5 0.06 VCMdiameter(mm) 1.1±0.4 0.9±0.4 <0.001 VCAdiameter(mm) 2.0±0.6 1.7±0.6 <0.001 VClength(mm) 12.8_±1.9 13.0_±1.8 0.22 VC-MTPangle(◦) 33.21±7.80 32.79±7.58 0.54

PVC-vomerinecrestdistance(mm) 6.4_±3.8 5.1_±4.1 <0.001

VC-vomerinecrestdistance(mm) 13.5±1.6 13.7±1.8 0.39

VC-FRdistance(mm) 7.2±2.0 9.6±2.1 <0.001

SPFwidth(mm) 3.9±0.8 3.9±0.8 0.37

VCP,posterior opening ofthe vidiancanal; VCM,middle partof thevidian canal;VCA,anterior opening ofthevidian canal; VC, vidiancanal;PVC, palatovaginalcanal;FR,foramenrotundum;SPF,sphenopalatine foramen;MTP,middleturbinate posteriorend. Mean±standarddeviation.

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Discussion

Since the surgical approach to the PPF is difficult, the intraoperativecomplicationssuchasexcessivebleedingand nerveinjurycanoccur. The vidiannerve,whichis formed bydeep(sympatheticfibers)andgreater(parasympathetic fibers) petrosal nerve, courses throughthe VC that is an importantlandmarkduringendoscopicaccesstothePPF.5

Especially,fortreatingtheresistantcasesofchronic vaso-motorrhinitis,thevidianneurectomyinterruptscholinergic innervationofthenasalmucosabyparasympatheticﬁbers.6

Inpreviousstudies, theendoscopicsurgicalapproaches to the VC were classiﬁed as transsphenoidal (Type I) that transectedthevidian nerveinside thesphenoidsinus and transnasal(Type II) thatis performed in theanteriorwall of the sphenoidsinus.7 _Type _I _had _its _advantages _shorter

operatingtime, less risk of injury and reduced bleeding. The patients withno intrasphenoid septum, theVC canal corpusType2and3,thepresenceofthePPP,thegreater distancebetweenVCandFRandtheVCnotinextreme lat-eralizedpositionweresuitableforTypeIapproach.Inother cases,TypeII approachwasmostlychosen.4,5_The _smaller

angle between the posterior end of the middle turbinate andthelateralmarginoftheanterioropeningoftheVC,no extremeseptumdeviation,thepresenceofthegapbetween thesphenoidprocessofthepalatineboneandthesphenoid bonejustmedialtotheVCsigniﬁcantlyincreasedthe suc-cessrateof TypeII approach.5---7 _The _VC_corpus _types_and

thePPPwhichaffectsthemorphometricparametersshould beevaluatedonpreoperative CT scantoavoid iatrogenic injuryduringendoscopicsurgery.4

We observed the VCcorpus types andthe presence of the PPP with a correlation between them. The ﬁrst aim of our study was to show the relationship of them with themorphometricmeasurementsandthevariationsofthe surroundingsphenoidstructures.Inpreviousstudies, Bidark-otimath et al., Yeh et al., Chen et al. and Cankal et al. reportedtheprevalenceoftheVCType1(withinthe sphe-noid corpus) as 67%, 50.8%, 55%, 54%; Type 2 (partially protrudingintothesphenoidsinus)as22%,39.8%,31%,36%; Type 3 (totally protruding into the sphenoid sinus with a stalk)as11%,9.4%,14%,10%,respectively.4,8---10_In_this_study,

we classiﬁed theVC variants asType1, 55.6% (278/500); Type 2, 34.8% (174/500); Type 3, 9.6% (48/500). Conse-quently, the VC Type 3 constitutes a minority while the VCType 1 makes up half of the canals assimilar to pre-vious studies.The VC Type1that is embeddedinside the sphenoidcorpusinhibitsthevisualizationoftheVCinboth surgicalapproaches.Inthiscase,ifthereisnogapbetween thepterygoidprocessandthesphenoidprocessofthe pala-tinebone,one ofthemis partiallyremoved bytransnasal approach.5,7_On_the_other_hand,_the_prevalence_of_the_PPP

wasdeterminedas39.2%(196/500),similartoprevious stud-iesresultsthatranged between19%and43.6%.4,11,12 _Also,

wereportedthattheprevalenceofthePPPthatfacilitates theTypeIapproachweresigniﬁcantlyhigherin VCType2 (72.4%)andType3(95.8%)asshowninTable3(p<0.001).

Intheliterature,themostcommontypeof pneumatiza-tionofthesphenoidsinuswasfound asthesellartype.5,13

Wealsoobservedthepatternofthesphenoid pneumatiza-tionanddeterminedasthesellartype(67%).Thesellartype

pneumatizationfacilitatesalloftheendoscopicapproaches but, the conchal (nonpneumatized) sphenoid which was found as1%in ourstudy is arelativecontraindicationfor both types. The intrasphenoid septum is usuallydeviated andmostlyattachedtooneside(ICASorOCS).5

Fernandez-Miranda et al. reported that the prevalence of only one midlinesphenoidseptumwas87%andtheICASwas13%.14

WereportedthatthenumberoftheICASwas142(28.4%), theOCSwas72(14.4%)andtheseptumbetweentheVCand vomerinecrestwas66(13.2%).AccordingtoTables3and4, theprevalenceoftheICASandtheseptumbetweentheVC andvomerinecrestwerepositivelycorrelatedwiththeVC protrusionandthepresenceofthePPP(p<0.001),butthe prevalenceoftheOCSwasnotaffected.Inthisrespect,our studyistheﬁrstreportingthatthepresenceoftheICASand theintrasphenoid septumbetweenVC andvomerinecrest is associated withthe VCprotrusion andthe PPP. Speciﬁ-cally,thepresenceoftheintrasphenoidseptumbetweenVC andvomerinecrestcaninhibitvisualizationduringsurgery. Removal of the septum is time-consuming and can cause skull base penetration and injury to the internal carotid arteryeventhoughtheVCprotrusionandPPPexist.4_In

addi-tion,weanalyzedthattheVCismostlylocatedmedialtothe MPPandisnotaffectedbytheVCprotrusionandthePPPin

Tables3and4(p=0.06,p=0.16).Also,wefoundthatthere wasnorelationshipbetweentheseptumdeviationandother parameters.Themediallocationof theVCandnoseptum deviationfacilitatesthetransnasalapproach.

In the literature, the measured mean distances from vomerine crest to VC ranged between 12 and 16mm and to PVC ranged from 8 to 11mm, respectively.4,8,15 _Also,

themeandistancesbetweenFRandVCweremeasuredas ranging between 4 and 8.5mm.3,4,8,15,16 _In _our _study, _we

measured the mean distance from vomerine crest to VC andtoPVCas13.6±1.7mmand5.9±3.9mm,respectively. The mean FR-VC distance was measured as8.1±2.3mm. AccordingtoTables5and6,theVCprotrusionalteredthe VC-FRandVC-PVCdistanceswhichwerelargerinVCType 2 and 3 (p<0.001). Also, these distances were affected asincreasedwiththepresenceofthePPP(p<0.001).Yeh et al., Hewaidi et al., Vescan et al. and Citardi et al. reported a positive correlation between the PPP and the VCprotrusionwhichincreasedthedistancebetweenVCand FRwassimilarwithourstudyresultsthatcanprovideagood surgicalguideinbothendoscopicapproaches.4,11,17,18

How-ever,thesmallerVC-FRandVC-PVCdistancesinVCType1 whichhadnoprotrusionintothesphenoidsinuscancause neurovascularcomplicationsthatshouldbekeptinmindby thesurgeons.Inaddition,thePPPusuallycausesprotrusion ofthesurroundingsphenoidstructuresintothesinus.4_So,

duringtranssphenoidalsurgerythesurgeonshouldbecareful toavoidtheincreasedriskofneurovascularinjury.

Wereportedthatthemeasuredmeandiameters ofthe middle part, anterior and posterior openings of the VC were 1.0±0.4mm, 1.9±0.6mm and 1.6±0.5mm similar tothepreviousstudies,respectively.3,8,10_Also,_we_found_the

meanlengthoftheVCas12.9±1.9mmwhileotherstudies reportedvaluesrangingfrom12.5to17mm.8,10_Mato_et_al.

reportedthatduringthetransnasalapproach,theamountof bonydrillingontheinferomedialsurfaceoftheVCdepends on the length, protrusion of the VC and pneumatization

(8)

degree ofthepterygoidprocess.So,thesedatacanguide asafeproceduretotheanteriorgenuofthepetrousICA.19

ButinthisstudywefoundthatthelengthoftheVCandthe diameteroftheposterioropeningoftheVCwerenot statis-ticallyrelatedwiththetypeoftheVCandthedegreeofthe PPPasseeninTables 5and6.The meandiameters ofthe middlepartandanterioropeningoftheVCweresmallerin VCType3andtheVCwithPPP(p<0.001).

On theotherhand, theanterioropening oftheVCwas located above and 4---6mm posterolateral to the inferior margin of the SPF that is used in transnasal approach.20

Hwangetal.reportedthattheVC-SPFhorizontaldistance was positively, but the diameter of the SPF was nega-tivelycorrelatedwiththeVC-FRdistanceandmeasuredthe mean diameter of the SPF as5.3±1.3mm on the three-dimensionalreconstructionoftheCTscans.3_We_measured

the mean diameter of the SPF as 3.9±0.8mm but, we reportedthatthe diameteroftheSPF wasnotcorrelated withtheVC-FRdistance,theVCcorpustypesandthePPP asseeninTable5and6(p=0.19,p=0.27).

The lateralmarginof theanterioropeningoftheVCis usuallylocated at thesuperolaterallevel of theposterior end of the middle turbinate; the smaller angle between themincreasesthesuccessrateoftheoperations.5_Liu_et_al.

measuredtheaveragevalueofthatangleandcomparedto theoperatingsuccess rates.Theyreportedthat themean angle fromaxialand coronalCT imagingwere30.2±4.9◦ and26.4±9.1◦inthesuccessfulgroup,butthevalueswere 33.8±4.8◦and44.3±8.1◦inthefailedgroup,respectively.6

Inour study,we measured thisangle as33.05±7.71◦ and foundthattheanglevaluewasnotaffectedbytheVC pro-trusionandthePPPasshowninTables5and6.

This studyhassomelimitations. Unapparentmarginsof thePPFcomplicateselectionofsuitableplanesfor measure-ments.CTimagingmaynot representthetrue plane that iscompatiblewhenencounteredduringendoscopicsurgery. Recruitmentofthehighernumberofpatientsandpatients fromdifferentracesmaygiveresearchersmore comprehen-siveresults.

Conclusion

In this study, we examined the VC in all respects and reportedthattheICAS,theseptumbetweenthevidiancanal andthevomerinecrest,theVCcorpustypes,theVC-FRand theVC-PVCdistanceswereaffectedbythepresenceofthe PPPwhich play akey rolein endoscopicsurgery. But, we found thatthe presence ofthe PPPdidnot alterthe dis-tancefromthevomerinecresttotheVCandthelocationof theVCrelatedtoMPP.So,thePPPcanhaveaninﬂuenceon theconﬁgurationofthevidiancanalbutnotontheposition of it.Precise knowledgeof the radiologic anatomyof the pterygopalatine fossamaybeessential fordiagnosing vid-iannervepathologyandchoosinganappropriateendoscopic approachandsideofthesurgicalintervention.Asaresult, the surgical complications associated with an endoscopic vidianneurectomycanbedecreased.

Conﬂicts

of

interest

Theauthorsdeclarenoconﬂictsofinterest.

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