Alveolar nerve impairment following bilateral sagittal split ramus osteotomy and genioplasty

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Contents lists available atScienceDirect

Journal

of

Oral

and

Maxillofacial

Surgery,

Medicine,

and

Pathology

j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / j o m s m p

Original

research

Alveolar

nerve

impairment

following

bilateral

sagittal

split

ramus

osteotomy

and

genioplasty

Luigi

Angelo

Vaira

c,∗

_,

_Olindo

_Massarelli

a

_,

_Silvio

_Mario

_Meloni

b

_,

Giovanni

Dell’Aversana

Orabona

c

_,

_Pasquale

_Piombino

d

_,

_Giacomo

_De

_Riu

a

a_University_of_Sassari,_{Maxillofacial}_Unit,_Viale_San_Pietro_43B,₀₇₁₀₀_Sassari,_Italy b_University_of_Sassari,_Dentistry_School,_Viale_San_Pietro_43B,₀₇₁₀₀_Sassari,_Italy c_University_of_Naples_“Federico_II”,_{Maxillofacial}_Unit,_Via_Pansini_5,₈₀₁₃₁_Naples,_Italy d_Second_University_of_Naples,_ENT_Unit,_Via_Pansini_5,₈₀₁₃₁_Naples,_Italy

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received23August2016 Receivedinrevisedform 28November2016 Accepted12December2016 Availableonlinexxx Keywords: Alveolarnerve Genioplasty BSSROcomplications

a

b

s

t

r

a

c

t

Objective:Permanentsensorychangesaftersagittalsplitosteotomyhavebeenestimatedbyvarious methodsofmeasure.Theincidenceaftersagittalsplitosteotomyvaryconsiderably.Thepurposeofthis studywastoevaluatesensoryalterationsinpatientstreatedeitherwithsagittalmandibularosteotomy andgenioplastyoronlywithsagittalmandibularosteotomy.Thetypeofsensoryalterationandthetimes ofrecoveryoflowerlipsensitivitywasalsocheckedinthedifferentgroups.

Methods:106patientswhounderwentBSSROw/ogenioplasty,duringa4-yearperiod,wereincluded. Qualitativeandquantitativetestswereappliedtoinvestigatetactilesensitivity,providingobjectively measurabledatainvolvingtheabilitytofeelthestimulusandtodiscriminateatwopointsstaticstimulus. Thermalsensitivity,sharp/bluntdiscriminationwerealsoevaluated,aswellthequalityofsubjective sensorysymptoms.

Resultsandconclusion:Eighteenmonthsaftersurgery,almostallofthepatientshadsatisfactoryrecovery oftheirinitialskinandmucosalsensorydeﬁcits,buttheintensityofmoreﬁnediscriminativesensitivity wasreducedinthosewhohadsimultaneouslyundergonegenioplastyassociatedwithBSSRO. ©2016AsianAOMS,ASOMP,JSOP,JSOMS,JSOM,andJAMI.PublishedbyElsevierLtd.Allrightsreserved.夽

1. Introduction

Surgicalrepositioningoftheskeletalcomponentsofthefacial structure can be used to improve function and aesthetics. An extensivenumberofosteotomiesareperformedwithinthe max-illofacialregiontofulfilthesepurposes.Themostcommonlyused aretheLeFortIosteotomyofthemaxilla,thebilateralsagittalsplit ramusosteotomy(BSSRO)andgenioplastyofthechinarea[1].A proliferationofsuchtreatmentshasoccurred,owingtothe increas-ing need to improve facial appearance and resolve functional deficits, such as difficultiesin mastication and speech. Various benefitshavebeenreported,includingimprovedmasticatory

func-夽 AsianAOMS:AsianAssociationofOralandMaxillofacialSurgeons;ASOMP:Asian SocietyofOralandMaxillofacialPathology;JSOP:JapaneseSocietyofOral Pathol-ogy;JSOMS:JapaneseSocietyofOralandMaxillofacialSurgeons;JSOM:Japanese SocietyofOralMedicine;JAMI:JapaneseAcademyofMaxillofacialImplants.

∗ Correspondingauthor.

E-mailaddress:luigi.vaira@gmail.com(L.A.Vaira).

tion,reducedtemporomandibularjointpainandimprovedfacial aesthetics[2].However,asthenumberofsurgicalperformances increases, numerous complications, such as vascular problems, temporomandibularjointproblems,nerveinjuriesandinfections, havealsobeenreportedmorefrequently[3].

Neurosensory deﬁcits are reported to be the most com-mon problem following orthognathic surgery [4]. Sagittal split osteotomyandintraoralverticalramusosteotomyarethemost commonly usedosteotomiestocorrect mandibulardeformities. Alteredfunctionoftheinferioralveolarnervesometimes compli-catesmandibularosteotomyandisindicatedbysensorychanges inthedistributionofthementalnerve(thelowerlipandthechin). Theincidence ofpermanent sensorychanges aftersagittalsplit osteotomyhasbeenestimatedbyvarioussubjectiveandobjective measures,which varyconsiderablyintheirabilitytodetectand quantifyanydeﬁcit.Insomestudies,theincidenceaftersagittal splitosteotomyrangedfrom0%to82%.[5]

Injuriestotheinferioralveolarnerveduringtheosteotomies operationmayresultfromstretchingofthenerveduringmedial retraction,adherenceofthenervetotheproximalsegmentafter http://dx.doi.org/10.1016/j.ajoms.2016.12.003

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splitting,directmanipulationofthenerve,bonyroughnessonthe medialsideoftheproximalsegmentormobilisationofthe seg-ment.Therelationofthemandibularcanaltothelateralcortexof themandibularramuscanaffecttheincidenceofnervedamage.In addition,osteosynthesistoolsmaycauseinjuriesviacompression oftheinferioralveolarnerveduringﬁxationordirectinjurytothe nerve[1,6,7].

Virtuallyallpatientshavealteredsensationintheimmediate post-operativeperiod,buteveninthelongterm,morethan one-thirdofpatientsreportsubjectivesensorydisturbances[8–10].The extentandcourseofnerverecoveryvarygreatlyinstudiesinwhich thesubjectivesensationhasbeenfollowedatseveraltimepoints upto1year,butlittleattentionhasbeenpaidtofactorsthatcould explainthevariance.

Persistingsensoryalterationscancauseproblemsinthedaily lives of patientsand decreased satisfaction withthetreatment results.Detailedknowledgeoftherecoverypatternandextentof thesensoryalterationswouldbeofgreatimportanceforpatient communication,aswellasfordeterminingtheneedforpossible furtherdiagnostictestsandtreatmentsduringtherecoveryphase [11].Therefore, one mustcarefullyevaluatethedegree of neu-rosensorydisturbance(NSD)anditstreatmentandprognosisat anearlystageaftersurgery.Suchevaluationwouldbeveryhelpful forcliniciansandtheirpatient.

ForevaluatingtheNSDofthechin,manytypesofneurosensory statusexaminationsareused[5–7,11–14],whichcanbeclassified intothreegroups:measurementsoftouch,painandthermal sen-sation.Physiologically, touchsensationistransmittedbyA-beta fibres,thermalsensationsbyCfibresandpainandcoldsensations byA-deltaandCfibres,respectively[13].Therefore,toincreasethe diagnosticaccuracyofthetestingandtodetectdifferenttypesof damage,varioustestsshouldbecombined,suchascombinationof touchsensoryinobjectiveandsubjectivemanners.

Thepurposeofthisstudywastoverifyifsubstantialdifferences existintermsofsensoryalterationsbetweenpatientstreatedeither withsagittalmandibularosteotomyandgenioplastyoronlywith sagittalmandibularosteotomy.Itwasalsoourintentiontoidentify thetypesofsensoryalterationandthetimesofrecoveryoflower lipsensitivityinthedifferentgroups.

2. Patientsandmethods

TheclinicalrecordsofthepatientswhounderwentBSSROalone orcombinedbimaxillaryosteotomiesattheMaxillofacialSurgery UnitoftheSassariUniversityHospital,Italy,duringa4-yearperiod between2009and2013,wereexamined.

Patientswhohadconditionswithgreaterpropensitytoalter recovery patterns or complicated systemic conditions, such as apersistingorofacialsensory impairment,diabetes,ahistory of facialtraumaoroperationorsignificantpsychiatricdisorderswas excludedfromthestudygroup.Priortosurgery, nervefunction wastestedbilaterallytodocumentanydeficitsduetothe pres-enceofconcomitantdisease;nosuchdeficitswereencountered. Allpatientsfollowedanordinaryrecoverycourseaftersurgeryand noneshowedseverepost-operativecomplications,suchas persis-tentoedemaorinfection.Thestudywasapprovedbytheethical committeeoftheUniversityofSassari.

The same surgeon, who was experienced in orthognathic surgery,performedallsurgeries. Allpatientsweretreatedwith sagittalmandibularramusosteotomy(Epker’svariant),associated ornotwithgenioplasty(atthelowerborder fromtheﬁrst pre-molarareaof onesidetothesameareaontheopposite).Both osteotomieswereperformedwithareciprocatingsawandthen splittedwithsagittalsplitter andseparators.Ostheosintesiswas donewithtitaniumplatesandscrews.

Fig.1. Cutaneousareastested.V:vermilion.M:medianregion.P:paramedian region.F:foramen.

Thesubjectsincluded(106patients, 66menand40women; meanage:26.1years,range:21–37years)weredividedintothe followinggroups:

Group1:classIII,mandibularretrusionwithoutgenioplasty(28 patients)

Group2:classIII, mandibularretrusionplus genioplasty(28 patients)

Group3:classII,mandibularadvancementwithoutgenioplasty (26patients)

Group4:classII,mandibularadvancementplusgenioplasty(24 patients)

Toobtainaprecisemapofthesensitivityoftheregionpertaining totheinferioralveolarnerve(andparticularlythementalnerve), theregionitselfwasdividedintothefollowingareas(Fig.1): -themedianregionofthechinandlip:1cmbilaterallyfromthe

symphysismandibulae,boththecutaneousandmucosalsides; -theparamedianregion:2cmbilaterallyfromthesymphysis,both

cutaneousandmucosalsides;

-theareaofthementalforamen:3cmbilaterallyfromthe symph-ysis(afewmillimetresbelowtherootsofthe4thand5thteeth), onboththecutaneousandmucosalsides;

-thevermilionborderofthelowerlip.

Thefunction ofthe inferioralveolarand mental nerves was testedfor18monthsaftersurgeries.

Allthetestswerecarriedoutbyanindependentmedicaldoctor inaroomfreeofanyacousticorvisualdisturbancescapableof affectingthetests,withthepatientshavingtheireyesclosed.The resultswererecordedonastandardform.

Qualitativeandquantitativetestswereappliedtoinvestigate tactilesensitivity,providingobjectivelymeasurabledatainvolving theabilitytofeelthestimulusandtodiscriminateatwopoints staticstimulus.Thermalsensitivity,andsharp/blunt discrimina-tionwerealsoevaluated,aswellthequalityofsubjectivesensory symptoms.

2.1. Tactilesensitivity

Objectiveandquantitativeevaluationswereperformedusing theSemmes–Weinsteinpressure aesthesiometer.Thefacialskin sites were tested bilaterally while thepatients kepttheir eyes closed.Thepointsofstimulationwereselectedinrandomorder.

Theteststartedwiththethinnerfilament,followedbyfilaments withprogressivelyincreasingthickness.Thepatientwasaskedto answeryeswhenthetouchofthemonofilamentwasfelt.Then, afilamentimmediatelythickerwastested,butonlyintheareas withoutpositiveresponsetothepreviousfilament.Eachstimulus

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wasmaintainedforapproximately1.5s,andarticulatemovements wereavoidedduringuseofthemonofilaments.Foreach tested monofilament,thestimuliwereapplied4timesineachareaof interest.Thestimulusresponsewasconsideredpositivewhenthere wereatleast3(75%)correctanswers(3of4correctstimuli).The Semmes–Weinsteinmonofilaments2.83and3.22wereselectedas theupperlimitofnormalityforthedetectionthresholdsforthe lowerlipandchin,respectively.

2.2. Two-pointsdiscriminativesensitivity

assessmentwasmadeusingWeber’saesthesiometer,an instru-mentsimilartoapairofdividersthatmakesitpossibletovisualize thedistancebetweenthetwopointsatthetimeitisbeingused. Bothpointswerepositionedsimultaneouslyintheareaoftheskin underinvestigation,andthepatientswereaskedwhetherthey per-ceivedonlyoneortwodistinctstimuli.Beginningwithaminimum distanceof5mm,thepointsweregraduallyseparateduntilthe patientsperceivedthemasseparate;theresultswereconsidered negativeifthepatientsfailedtoperceivetwoseparatestimuliwhen thedistancebetweenthepointswas15mmormore.

Thresholdsoftwo-pointdiscriminationwasassessedusinga “staircaselimitsmethod”[15].Thismethodincludedfourtestseries withalternatingdescendingandascendingstimulusmagnitudes. Athresholdwasbasedonthemeanofeightstimulusmagnitudes correspondingtothereversalsfrompositivetonegativeresponses orviceversainthesefourseries.

2.3. Sharp/bluntdiscrimination

thisteststheabilitytodistinguishthestimuluscausedbythe tipoftheneedleoftheaesthesiometer,orofasmallpaintbrush,to evaluatethepatient’scapacitytodifferentiatebetweenbluntand sharpstimulation.Eachareawasrandomlytouchedbyoneofthe instrumentswhilethepatientswererequiredtokeeptheireyes closedtopreventanyvisualinterference.

2.4. Thermalsensitivity

Thistwo-parttestevaluatedsensitivitytocoldandheat.Aglass testtubewitha4-mmbasewasﬁlledwithwaterheatedtoa tem-peratureof40–45◦C.Afteritsbasehad beenplaced againstthe skin,thepatientswereaskedwhethertheyfeltanysensationof heatwhiletheyweresimultaneouslywarnednottogivean afﬁr-mativereplyonlybecausetheyfeltthecontactwiththetesttube. Thesameoperationwasalsocarriedoutusingice.

2.5. Subjectivesensorysymptoms

Thesubjectindicatethedifferentqualitiesofsensorychanges ona schematic ﬁgureof theface by markingthe regions with differentcolours,classifyingthemin4categories:normal(nerve withnosubjective alterations),negativesymptoms (hypoesthe-sia),positivesymptomswithorwithouthypoesthesia(paresthesia, dysesthesiaand/orpain)andtotallossofsensibility.

2.6. Dataanalysis

Theresultsofthequalitativetests(numericallyunquantiﬁable) wereclassiﬁedasfollows:A:promptperceptionofthestimulus;B: lessintenseperceptionofthestimulus;C:littleperceptionofthe stimulus;D:noperceptionofthestimulus.

The Mann-WhitneyU test wasused tocompare differences between the groups (only in quantitative test). Statistical sig-niﬁcancewasdeﬁnedasP<0.05.Thetwopoints-discrimination

thresholdwasdeterminedforeachsiteandwhetherthese thresh-olds differed between groups depending on surgery, with or withoutgenioplasty, usingan analysisof variance (ANOVA)for repeatedmeasures.

3. Results

Resultsofthetestsseemindicatethatpatientswhounderwent mandibularretrusionpresentedabetterperceptionofalltypesof stimula.MentoplastyassociatedwithBSSRO(bothadvancement andretrusion)worsentheabilitytopromptlypercivethe stimu-lation.Inallthepatientgroups,theworsequalityofthesensitive perceptionwasinvermilionarea.

3.1. Semmes-Weinsteinmonoﬁlamenttest

Datawerecollectedbeforeand1,3,6,12and18monthsafter surgeryandareexpressedaspercentagerateofpatientsofeach groupfeelingcorrectlyorabnormallythetactilestimulusinthe investigatedregions(Table1).Beforethesurgeryallthepatients detectedthestimulusof2.83and3.22monoﬁlamentonthelower lipandchin,respectively.

StatisticalanalysisfortheSemmes-Weinsteintestwascarried outandissummarisedbelow:

Until the sixth months control, signiﬁcant differences were observed(P<0.05)betweengroups1and2andgroups3and4 forallregions.ClassIIpatientsreportedgenerallyworstresults, butthesedataresultednosigniﬁcant.

At12and18months,eventhoughtheforamenandespecially thevermillionareashowedlesssensitivity,nosigniﬁcant differ-enceswereobserved(P>0.05)betweenthegroups.

3.2. Two-pointdiscriminationtest

For the two-pointdiscriminationtest, values were collected beforeand3,6and12monthsaftersurgeryandareexpressedas rateofpatientsthatdiscriminatedbetweentwoseparatepoints. Bothpointswerepositionedsimultaneouslyintheareaoftheskin underinvestigationandthepatientswereaskedwhetherthey per-ceivedonlyoneortwodistinctstimuli.Beginningwithaminimum distanceof5mm,thepointsweregraduallyseparateduntilthe patientsperceivedthemasseparate.Theresultswereconsidered negativeifthepatientsfailedtoperceivetwoseparatestimuliwhen thedistancebetweenthetwopointswas15mmormore.Table2 reportsaframeworksummaryofthisevaluation.

Statisticalanalysisforthetwo-pointdiscriminationtestwas car-riedoutandcanbesummarisedafollows:at3,6and12months, signiﬁcantdifferenceswereobserved(P<0.05)betweengroups1 and3(nogenioplasty)andgroups2and4(genioplasty)foralmost allregions.(forvalue<5mm,i.e.excellentsenseofdiscrimination) 3.3. Sharp-bluntdiscrimination

Ingroup1,thestimuluswaspromptlydiscriminatedin79–90% of patientsdepending from theareas. In thegroup of patients whocarriedoutmentoplastyinadditiontomandibularretrusion (group2)theseratesdropto75–81%.Likewise,patientssubjected toisolatedmandibularadvancement(group3)presentaprompt perceptionofthestimulusin80–86%ofthecases,whilethesedata dropto79–82%whengenioplastywasperformed(group4).The differencebetweenthegroupswasnotsigniﬁcant.

3.4. Sensitivitytoheat

In group1, thehot stimuluswaspromptlydiscriminated in 88–89% of patients, dependingfrom theareas. In the groupof

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Table1

ResultsofSemmes-Weinsteinquantitativetest(%ofpatients).

Median Paramedian Foramen Vermillon

1month 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 13 2 15 5 13 2 15 5 13 0 15 5 9 0 12 3 Abnormal 87 98 85 95 87 98 85 95 87 100 85 95 91 100 88 97 3months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 25 12 25 12 25 12 26 13 22 15 22 13 22 13 20 13 Abnormal 75 88 75 88 75 88 74 87 78 85 78 87 78 87 80 97 6months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 58 47 60 50 60 45 60 48 60 48 58 44 56 45 52 40 Abnormal 42 53 40 50 40 55 40 52 40 52 42 56 44 55 48 60 12months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 81 77 82 77 79 74 82 76 80 73 81 74 77 70 78 71 Abnormal 19 23 18 23 21 26 18 24 20 27 19 26 23 30 22 29 18months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 95 95 98 97 95 94 97 95 87 90 93 92 92 90 92 92 Abnormal 5 5 2 3 5 6 3 5 13 10 7 8 8 10 8 8 Table2

ResultsofTwo-pointsdiscriminationquantitativetest(%ofpatients).

Beforesurgery 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

>10mmpoordiscrimination 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

5–10mmgoodsenseofdiscrimination 35 36 39 30 31 31 38 30 31 33 38 30 25 26 26 24 <5mmexcellentsenseofdiscrimination 65 64 61 70 69 69 62 70 69 67 62 70 75 74 74 76

3months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

6months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

12months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

patientswho carried outgenioplasty inadditiontomandibular retrusion(group2)thisratedropsto77–80%.Likewise,patients subjectedtoisolatedmandibularadvancement(group3)present apromptperceptionofthestimulusin78–86%ofthecases,while thisratedropsto77–83%whengenioplastywasperformed(group 4).Thedifferencebetweenthegroupswasnotsigniﬁcant. 3.5. Sensitivitytocold

Ingroup1,thecold stimuluswaspromptlydiscriminated in 85–88%of patients, depending fromthe areas. In thegroup of patientswho carried outgenioplasty inadditiontomandibular retrusion(group2)thisratedropsto77–80%.Likewise,patients subjectedtoisolatedmandibularadvancement(group3)presenta promptperceptionofthestimulusin77–86%ofthecases;thisrate dropsto75–83%incasesthatgenioplastywasperformed(group 4).Thedifferencebetweenthegroupswasnotsigniﬁcant.

AllthesedataaresummarizedonTable3. 3.6. Subjectivesensorysymptoms

Resultsofthesubjectivesensorysymptomswererecordedat 7daysand1,3,6,12an18months.At7daysallpatientshadatotal lossofsensibilityineveryregionofthechinandthelip.

Thedatarecorded subsequently areresumed in Table4. No patientscomplainedcompleteanaesthesiaat18monthsfollowup.

4. Discussion

Theresultsofthesetestsandtheanalysisofthepatients’ com-mentsrevealedthattheresidualneurosensoryalterationsarenot disabling.Numerousstudies[15–34]havealreadybeenpublished concerningpost-surgical sensitivity of the inferioralveolar and mentalnervesfollowingmandibularosteotomy.Themajor com-plicationofthistypeofprocedurewasatransientor(morerarely) permanentalterationintheneurosensoryfunctionofthelower lip.Becauseoftheiranatomicalposition,theinferioralveolarand mentalnervesmaysuffervarioustypesoftraumaduring orthog-nathicsurgery.Thesemaybeindirect,suchascompressiondueto theformationofapost-operativeoedemaorhaematoma,ordirect, includingstrainand/orcompressionduringseparationofthesoft tissue,osteotomy,repositioningofthebonysegmentsorduring stabilisation.

Accordingtosomeauthors[15],thevascularsupplymayalso becompromised,ifthenerve is exposedduringsurgical proce-dures.Manyexperimentalstudieshavebeenperformedwiththe aimofdemonstratingthatfactorssuchasagecanaffectthe post-operativerecoveryofsensitivity.Adirectcorrelationseemstoexist betweenincreasingageandthepersistenceofparaesthesiaafter sagittalosteotomyofthemandible,particularlyinpatientsolder than40yearsofage[21,25];youngerpatientshaveabetterchance ofrecovery[18].In thisstudy,agedidnot appeartoaffectthe neurosensoryalterationandrecoverypattern.Thisis contradic-torytopreviousstudiesthatindicateolderageasariskfactorfor

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Table3

Resultsofsharp/bluntandthermictests(%ofpatients).

A B C D A B C D A B C D A B C D Group1 Sharp/blunt 85 11 4 0 90 10 0 0 91 9 0 0 79 11 10 0 Heat 89 10 1 0 89 9 2 0 89 10 1 0 88 10 2 0 Cold 87 11 2 0 88 11 1 0 88 11 1 0 85 10 5 0 Group2 Sharp/blunt 81 7 0 0 81 12 7 0 81 13 6 0 75 14 1 0 Heat 79 21 0 0 80 20 0 0 80 20 0 0 77 20 1 0 Cold 78 21 1 0 80 19 1 0 80 19 1 0 77 19 2 0 Group3 Sharp/blunt 85 9 6 0 85 9 6 0 86 8 6 0 80 12 8 0 Heat 86 11 3 0 86 10 4 0 86 10 4 0 78 20 2 0 Cold 86 10 4 0 86 9 5 0 85 11 4 0 77 20 3 0 Group4 Sharp/blunt 82 15 3 0 82 14 4 0 80 16 4 0 79 12 9 0 Heat 83 13 4 0 77 12 11 0 79 11 10 0 77 18 5 0 Cold 83 12 5 0 78 11 11 0 79 11 10 0 75 17 8 0

A:promptperceptionofthestimulus;B:lessintenseperceptionofthestimulus;C:littleperceptionofthestimulus;D:noperceptionofthestimulus.

Table4

Resultsofsubjectivesensorysymptomsassessment(%ofpatients).

1month 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 0 0 0 0 9 7 0 0 9 7 0 0 10 7 0 0 Negativesymptoms 0 0 0 0 10 14 14 12 10 12 12 12 11 14 12 10 Positivesymptoms 22 21 17 19 21 21 11 10 20 23 13 10 22 21 13 14 Anaesthesia 78 79 83 81 60 58 75 78 61 58 75 78 58 58 75 76 3months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 7 5 6 2 18 14 8 6 18 14 8 5 16 13 8 6 Negativesymptoms 38 15 35 20 61 58 50 44 60 58 48 44 63 58 48 44 Positivesymptoms 40 60 39 58 14 21 25 31 15 20 27 32 12 22 25 32 Anaesthesia 15 20 20 20 7 7 17 19 7 8 17 19 9 7 19 18 6months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 40 25 35 25 46 44 44 40 45 44 44 40 45 44 45 40 Negativesymptoms 35 30 40 28 36 40 31 36 37 39 32 35 36 39 30 35 Positivesymptoms 15 25 12 27 12 10 15 11 13 10 16 12 12 11 16 12 Anaesthesia 10 20 12 20 6 6 10 13 5 7 8 13 7 6 9 13 12months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 64 57 57 54 64 67 56 57 64 65 56 55 64 65 57 55 Negativesymptoms 27 25 31 32 27 33 31 29 26 33 31 31 26 33 32 31 Positivesymptoms 9 18 12 14 9 0 13 14 10 2 12 14 10 2 11 14 Anaesthesia 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 18months 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Normal 96 95 98 96 96 96 98 96 97 96 95 95 97 96 96 95 Negativesymptoms 3 3 2 2 3 2 1 2 2 2 4 3 3 3 2 4 Positivesymptoms 1 2 0 2 1 2 1 2 1 1 1 2 0 1 2 1 Anaesthesia 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

prolongedsensorydisturbance.Thisdifferenceprobablyresulted becausethepatientgroupofthisstudywasmainlycomposedof adultsunder40yearsold.Toinvestigatetheeffectofageing,future studiesbasedonsubjectswithanindiscriminateagedistribution shouldbeperformed.

Evaluatingthesituationfollowingmultiplesurgicalprocedures isimportant:genioplastyperformedatthesametimeasa sagit-talmandibularosteotomymayleadtonervelesionsatdifferent levelsandthushindersatisfactoryrecoveryofthealtered sensa-tionfromtheseprocedures[19].Genioplastytendstoaggravatethe nervedamagecausedbyorthognathicsurgery.Genioplastyalone is very rarelyassociated withneurosensory disturbances com-paredtoorthognathicsurgerybecauseincisionsareusuallymade atmoreperipheralsitesoftheinferioralveolarnerve(IAN).Few articles[1,13]haveevaluatedtheeffectofgenioplastyon neurosen-sorydisturbance.Thesestudiesreportarelativelylowincidence

ofhypoesthesiaaftergenioplasty.Ourresultsareinaccordwith others[9]showingthattherecoveryoftheIANismuchslowerin patientsundergoingmandibularosteotomycombinedwith genio-plasty,whichisprobablyattributabletothedoubleinsultcausedby thecombinedprocedures.Thedamagingeffectseemstobemore severeinthecaseofclassIIwithgenioplastyandcouldbeexplained bythestretchingofthenerveaftertheadvancement[1].

Recoveryofnervedamagewasmostmarkedfollowingtheﬁrst 3monthsaftersurgery,whichisinaccordwiththeresultsreported in previousprospective1-yearfollow-up studiesonIAN recov-ery afterBSSRO[20].In thecaseof BSSRO,mostnervedamage occursduringthesubperiostealretractiononthemedialsideof themandibularramus,mainlyresultingindemyelinatinglesions owing tocompression. Demyelinating nerve lesions are gener-allyknowntorecoverduringtheﬁrst4monthsafterinjury.The resultsindicatefurthernerveregenerationevenafter6monthsand

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continuingrecoveryuptothe1-yearfollow-up.Thiscorresponds toﬁndingsfromotherstudiesreportingimprovementofsensory alterationupto1yearafterBSSRO[6].

In ourstudy, the mandibularmovement wasrelated tothe increaseinthresholdlevelaftertheoperationbecausedirect stim-ulationordisturbancetotheinferioralveolarnerveseldomoccurs duringosteotomy surgery and traction of thenerve caused by movementofthebonesegmentsmight beoneof thecausesof post-operativesensorydisturbance. Inanytype oforthognathic surgery,nervecompressioncanoccurduetohookingor inflamma-toryoedemaresultingfrommovementofthedistalbonesegments. Atleast1yearisgenerallynecessarytoverifyresolutionofa neurosensoryalteration,as patientsmayreportsensory distur-bancesintheimmediatepost-operativeperiod,butthemajority experiencealmosttotalrecoverywithin18monthspost-operation [17,22].However,thediscordantresultsofthelargenumber of studiesdesignedtotestthefunctionoftheinferioralveolarand mentalnervesoftenmakethemdifficulttocompare.Thisdiscord ismainlyduetomethodologicaldifferences:someareexclusively qualitativestudiesbasedonsubjectivetestsorontheuseof ques-tionnaires[18,23],othersreportbothobjectiveandsubjectivedata obtainedusing exclusivelyqualitative techniques[16,21,35–37] andstillothershaveusedquantitativetests.Theirresults,however, are difficult to compare as the tests themselves were differ-ent[15,22,24–26,38,39].Furthermore,theresultsaresometimes reportedintermsoftherateofareaswithalteredsensitivityand sometimesintermsoftherateofpatientsexamined.Anaccurate evaluationofneurosensorydysfunctionshouldbebasedona stan-dardisedmethodologycapableofinvestigationandquantification, ratherthanonebasedonasimplequestionnaire[28].

Inourseries,oneyearaftersurgery,almostallofthepatients hadsatisfactorysensoryrecoveryoftheirinitialskinandmucosal sensorydeﬁcits,buttheintensityofthesensationwasreducedin thosewhohadsimultaneouslyundergonegenioplasty(groups2 and4)andinthepatientsundergoingorthognathicsurgeryforclass II.

5. Conclusions

Inconclusion,thisstudyhasextendedinformationonnormal valuesforstaticlighttouchandstatictwo-pointdiscriminationfor facialsites.Weshowedthatsimplehand-operateddevices,such asSemmes-Weinstein nylonmonoﬁlaments(light touch sensa-tion)andtheWeber’saesthesiometer(two-pointdiscrimination) remainusefulforstudyingtrigeminalsensoryfunction.Theforce conditionsduringtestingaresuchthatnormalvaluesfrom differ-entlaboratoriesforavarietyofsitesaregenerallyapplicableto anytrainedobserver.Theuseofthesedevicesistherefore appro-priate,particularlyindailyclinicalpracticeinwhicheasyandfast applicationisadvantageous.

Eighteen months after surgery, almost all of the patients reportedasatisfactoryrecoveryoftheirinitialskinandmucosal sensory deﬁcits. Patients who had simultaneously undergone genioplastyor surgeryfor class IIpresenteda worstrecover of moreﬁnediscriminativesensitivity.Inthesepatientstherecovery isgenerallyslowerandrequirednotlessthan6–12months.

Conﬂictofinterest

Nonedeclared.

Ethicalapproval

Thestudywasapprovedbytheethicalcommitteeofthe Uni-versityofSassari.

Acknowledgment

None

References

[1]Al-BishriA,DahlbergbG,BarghashcZ,RosenquistaJ,SunzelaB.Incidenceof neurosensorydisturbanceaftersagittalsplitosteotomyaloneorcombined withgenioplasty.BrJOralMaxillofacSurg2004;42:105–11.

[2]PosnickJC,WallaceJW.Complexorthognaticsurgery:assessmentofpatient satisfaction.JOralMaxillofacSurg2008;66:934–42.

[3]SousaCS,TurriniRNT.Complicationsinorthognathicsurgery:a comprehensivereview.JOralMaxillofacSurgMedPathol2012;24:67–74. [4]KimSG,ParkSS.Incidenceofcomplicationsandproblemsrelatedto

orthognathicsurgery.JOralMaxillofacSurg2007;65:2438–44.

[5]PoortLJ,vanNeckJW,vanderWalKGH.Sensorytestingofinferioralveolar nerveinjuries:areviewofmethodsusedinprospectivestudies.JOral MaxillofacSurg2009;67:292–300.

[6]GiannìAB,D’OrtoO,BiglioliF,BozzettiA,BrusatiR.Neurosensoryalterations oftheinferioralveolarandmentalnerveaftergenioplastyaloneorassociated withsagittalosteotomyofthemandibularramus.JCranio-MaxillofacSurg 2002;30:295–303.

[7]KabasawaY,HaradaK,JinnoS,SatohY,MaruokaY,OmuraK.Newevaluation methodforneurosensorydisturbanceinthechinofpatientsundergoing mandibularsagittalsplitramusosteotomy:anapplicationoftheheatﬂux technique.OralSurgOralMedOralPatholOralRadiolEndod

2006;102:719–24.

[8]PanulaK,FinneK,OikarinenK.Incidenceofcomplicationsandproblems relatedtoorthognathicsurgery:areviewof655patients.JOralMaxillofac Surg2001;59:1128–36.

[9]Teerijoki-OksaT,JääskeläinenS,ForssellK,ForssellH.Recoveryofnerve injuryaftermandibularsagittalsplitosteotomy:diagnosticvalueofclinical andelectrophysiologictestsinthefollowup.IntJOralMaxillofacSurg 2004;33:134–40.

[10]WestermarkA,BystedtH,VonKonowL.Inferioralveolarnervefunctionafter mandibularosteotomies.BrJOralMaxillofacSurg1998;36:425–8. [11]Teerijoki-OksaT,JääskeläinenSK,SoukkaT,VirtanenA,ForssellH.Subjective

sensorysymptomsassociatedwithaxonalanddemyelinatingnerveinjuries aftermandibularsagittalsplitosteotomy.JOralMaxillofacSurg

2011;69:208–13.

[12]ParkJW,ChoungPH,SeopKH,KimYK,ChungJW.Acomparisonof neurosensoryalterationandrecoverypatternamongdifferenttypesof orthognathicsurgeriesusingthecurrentperceptionthreshold.OralSurgOral MedOralPatholOralRadiolEndod2011;111:24–33.

[13]SatohY,KabasawaY,JinnoS,OmuraK.Analysisofclinicalusefulnessofthe heatﬂuxtechnique:predictabilityoftherecoveryfromneurosensory disturbancesinthechinundergoingmandibularsagittalsplitramus osteotomy.OralSurgOralMedOralPatholOralRadiolEndod 2008;106:637–43.

[14]VriensJPM,vanderGlasHW.Extensionofnormalvaluesonsensoryfunction forfacialareasusingclinicaltestsontouchandtwo-pointdiscrimination.IntJ OralMaxillofacSurg2009;38:1154–8.

[15]JonesDL,WolfordLM,HartogJM.Comparisonofmethodstoassess neurosensoryalterationsfollowingorthognathicsurgery.IntJAdultOrthod OrthognathSurg1990;5:35–42.

[16]WangJH.WaiteDE:Verticalosteotomyvssagittalosteotomyofthe mandibularramus:comparisonofoperativeandpostoperativefactors.JOral Surg1975;33:596–9.

[17]HohlTH,EpkerBN.Macrogenia:astudyoftreatmentresultswithsurgical recommendations.OralSurgOralMedOralPathol1976;41:545–8. [18]WalterJM,GreggJM.Analysisofpostsurgicalneurologicalterationsinthe

trigeminalerve.JOralSurg1979;37:410–4.

[19]SchendelSA,EpkerBN.Resultsaftermandibularadvancementsurgery:an analysisof87cases.JOralSurg1980;38:265–72.

[20]BrusatiR,FiamminghiL,SesennaE,GazzottiA.Functionaldisturbancesofthe inferioralveolarnerveaftersagittalosteotomyofthemandibularramus: operativetechniqueforprevention.JMaxillofacSurg1981;9:123–5. [21]MacIntoshRB.Experiencewiththesagittalosteotomyofthemandibular

ramus:a13-yearreview.JMaxillofacSurg1981;9:151–3.

[22]NishiokaGJ,ZyssetMK,VanSickelsJE.Neurosensorydisturbancewithrigid ﬁxationofthebilateralsagittalsplitosteotomy.JOralMaxillofacSurg 1987;45:20–6.

[23]UptonLG,RajvanakarnM,HaywardJR.Evaluationoftheregenerative capacityoftheinferioralveolarnervefollowingsurgicaltrauma.JOral MaxillofacSurg1987;45:212–6.

[24]LindqvistCC,ObeidG.Complicationofgenioplastydonealoneorin combinationwithsagittalsplit-ramusosteotomy.OralSurgOralMedOral Pathol1988;66:13–6.

[25]KarasND,BoydSB,SinnDP.Recoveryofneurosensoryfunctionfollowing orthognathicsurgery.JOralMaxillofacSurg1990;48:124–7.

[26]LeiraJI,Gilhuus-MoeOT.Sensoryimpairmentfollowingsagittalsplit osteotomyforcorrectionofmandibularretrognathism.IntJAdultOrthod OrthognathSurg1991;6:161–7.

(7)

[27]PosnickJC,Al-QattanMM,StepnerNM.Alterationinfacialsensibilityin adolescentsfollowingsagittalsplitandchinosteotomiesofthemandible. PlastReconstrSurg1996;97:920–7.

[28]FrydmanWL.Nerveinjuries.OralMaxillofacSurgClinNAm1997;9:207–18. [29]NewmanL.Bewaretheinferioralveolarnerveinramusosteotomy.BrJOral

MaxillofacSurg1997;35:297–302.

[30]AugustM,MarchenaJ,DonadyJ,KabanL.Neurosensorydeﬁcitandfunctional impairmentaftersagittalramusosteotomy:alongtermfollow-upstudy.J OralMaxillofacSurg1998;56:1231–5.

[31]BlomqvistJE,AlberiusP,IsakssonS.Sensibilityfollowingsplitosteotomyin themandible:aprospectiveclinicalstudy.PlastReconstrSurg

1998;102:325–33.

[32]TakasakiY,NomaH,MasakiH,FujikawaM,AlberdasJL,TamuraH,etal.A clinicalanalysisoftherecoveryfromsensorydisturbanceaftersagittal splittingramusosteotomyusingaSemmes?Weinsteinpressure aesthesiometer.BullTokyoDentColl1998;39:189–97.

[33]YlikontiolaL,KinnunenJ,LaukkanenP,OikarinenK.Predictionofrecovery fromneurosensorydeﬁcitafterbilateralsagittalsplitosteotomy.OralSurg OralMedOralPatholOralRadiolEndod2000;90:275–81.

[34]WestermarkA,BystedtH,VonKonowL.Patient’sevaluationoftheﬁnalresult ofsagittalsplitosteotomy:isitinﬂuencedbyimpairedsensitivityofthe lowerlipandchin?IntJAdultOrthodonOrthognathSurg1999;14:135–9. [35]BaileyPH,BaysRA.Evaluationoflong-termsensorychangesfollowing

mandibularaugmentationprocedures.JOralMaxillofacSurg1984;42:722–5. [36]MartisCS.Complicationsaftersagittalsplitosteotomy.JOralMaxillofacSurg

1984;42:101–7.

[37]CoghlanKM,IrvineGH.Neurologicaldamageaftersagittalsplitosteotomy. IntJOralMaxillofacSurg1986;15:369–72.

[38]CampbellRL,ShamaskinRG,HarkinsSW.Assessmentofrecoveryfrominjury toinferioralveolarandmentalnerves.OralSurg1989;64:519–22.

[39]YoshidaT,NagamineT,KobayashiT,MichimiT,NakajimaT,SasakuraH,etal. Impairmentoftheinferioralveolarnerveaftersagittalsplitosteotomy.J Cranio-MaxillofacSurg1989;17:271–6.