www.bjorl.org
Brazilian
Journal
of
OTORHINOLARYNGOLOGY
REVIEW
ARTICLE
Vestibular
evoked
myogenic
potentials
in
the
prognosis
of
sudden
hearing
loss
---
a
systematic
review
夽
Nathalia
de
Paula
Doyle
Maia
∗,
Karen
de
Carvalho
Lopes
,
Fernando
Freitas
Gananc
¸a
UniversidadeFederaldeSãoPaulo(Unifesp),DepartamentodeOtorrinolaringologiaeCirurgiadeCabec¸aePescoc¸o,Ambulatório deOtoneurologia,SãoPaulo,SP,Brazil
Received1June2019;accepted1October2019 Availableonline2November2019
KEYWORDS
Vestibularevoked myogenicpotentials; Prognosis;
Suddenhearingloss
Abstract
Introduction:Sudden hearing loss is an otorhinolaryngological emergency that often leads to severedamage tothe auditory andvestibular function.The vestibular evoked myogenic potentialisatestthatallowsanoninvasiveevaluationoftheotolithicsystemfunction and vestibulospinalandvestibulo-ocularpathways.
Objective: Toevaluatetheimportanceofvestibularevokedmyogenicpotentialindetermining theprognosisofpatientswithsuddenhearingloss.
Methods:AsearchforarticlespublisheduptoDecember2018wasperformedinthePubMed, Cochrane,VHL andLILACSdatabases usingMeSH descriptors.Retrospectiveandprospective articles wereincludedcontainingcervicalorocular vestibularevokedmyogenicpotentialin suddenhearinglosspatientsandinformationonassociatedvertigoand/ordizziness.
Results:Sixteenof62initiallyselectedarticlesmettheinclusioncriteriaandwereanalyzed. Regardingthemethodologyoftheevaluatedstudies,8studieswereprospective,sixwere ret-rospective,onecontainedpartofthedatafromaretrospectiveanalysisandanotherpartfrom aprospectiveanalysis,andonestudywascross-sectional.Atotalof872patientswere eval-uated(50.22%malesand49.77%females)withameanageof51.26years.Fourhundredand twenty-sixpatients(50.35%)hadvertigoand/ordizzinessassociatedwithsuddenhearingloss. Thecervicalvestibularevokedmyogenicpotentialwasperformedinallstudies,butonlyseven assessedtheocularvestibularevokedmyogenicpotential.Thecervicalvestibularevoked myo-genicpotentialshowedalterationsin38.65%of846evaluatedears,whereasocularvestibular evoked myogenicpotentialshowedalterationsin47.88%of368evaluated ears.Thehearing recovery ratewas analyzedby8articles,with63.4%of410evaluatedearsshowinghearing recovery.
夽 Pleasecitethisarticleas:MaiaNP,LopesKC,Gananc¸aFF.Vestibularevokedmyogenicpotentialsintheprognosisofsuddenhearingloss ---asystematicreview.BrazJOtorhinolaryngol.2020;86:247---54.
∗Correspondingauthor.
E-mail:nathaliadoyle@hotmail.com(N.P.Maia). https://doi.org/10.1016/j.bjorl.2019.10.001
1808-8694/©2019Associac¸˜aoBrasileiradeOtorrinolaringologiaeCirurgiaC´ervico-Facial.PublishedbyElsevierEditoraLtda.Thisisanopen accessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).
248 MaiaNPetal.
Conclusions:Thestudiessuggestthattheassessmentofthevestibularsystemusingvestibular evokedmyogenicpotentialseemstobeimportantintheprognosisofsuddenhearingloss.For betterfollow-upofpatientswithsuddenhearingloss,theemphasisshouldnotbelimitedtothe cochlea,butalsoincludethediagnosisandtreatmentofvestibularabnormalities,regardless ofthepresenceofvertigo.
© 2019 Associac¸˜ao Brasileira de Otorrinolaringologia e Cirurgia C´ervico-Facial. Published by Elsevier Editora Ltda. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/). PALAVRAS-CHAVE Potencialevocado miogênicovestibular; Prognóstico; Surdezsúbita
Opotencialevocadomiogênicovestibularnoprognósticodasurdezsúbita---uma revisãosistemática
Resumo
Introduc¸ão:Asurdezsúbitaéumaemergênciaotorrinolaringológicaquefrequentementecursa comgravesdanosàfunc¸ãoauditivaevestibular.Opotencialevocadomiogênicovestibularé um exame quepermite a avaliac¸ão não invasiva da func¸ão dosistema otolítico e dasvias vestíbulo-espinhalevestíbulo-ocular.
Objetivo:Avaliaraimportânciadopotencialevocadomiogênicovestibularnadeterminac¸ãodo prognósticodospacientescomsurdezsúbita.
Método: Umabuscadetrabalhospublicadosatédezembrode2018foirealizadanosbancosde dadosPubMed,Cochrane,BVSeLilacscomdescritorescadastradosnoMeSH.Foramincluídos artigosretrospectivoseprospectivosquecontivessemopotencialevocadomiogênicovestibular cervicalouocularempacientescomsurdezsúbitaeinformac¸õessobrevertigeme/outontura associados.
Resultados: Dezesseisde 62 artigos selecionados inicialmente preencheram os critérios de inclusãoeforamanalisados.Quantoàmetodologiadostrabalhosavaliados,8estudosforam prospectivos,seisretrospectivos,umcontinhapartedosdadosoriundadeumaanálise retro-spectivaeoutrapartedeumaanáliseprospectivaeumestudofoitransversal.Foramavaliados 872pacientes(50,22%dogêneromasculinoe49,77%feminino)commédiade51,26anos.Do totaldepacientes,426(50,35%)apresentavamvertigeme/outonturaassociadaàsurdezsúbita. Opotencialevocadomiogênicovestibularcervicalfoirealizadoemtodososestudos,porémo potencialevocadomiogênicovestibularocularemapenassete.Opotencialevocadomiogênico vestibularcervicalapresentoualterac¸ãoem38,65%de846orelhasavaliadas,enquantoo poten-cialevocadomiogênicovestibularocularestavaalteradoem47,88%das368orelhasavaliadas. A taxade recuperac¸ãoauditiva foianalisada por 8artigos, 63,4% de410 orelhas avaliadas apresentavamrecuperac¸ãoauditiva.
Conclusões:Osestudosdemonstramqueaavaliac¸ãodosistemavestibularcomousodo poten-cialevocadomiogênicovestibularpareceterimportâncianoprognósticodasurdezsúbita.Para melhoracompanhamentodopacientecomsurdezsúbitaaênfasenãodeveserestringiràcóclea, mastambémnodiagnósticoetratamentodealterac¸õesvestibulares,independentementeda presenc¸adevertigem.
© 2019 Associac¸˜ao Brasileira de Otorrinolaringologia e Cirurgia C´ervico-Facial. Publicado por Elsevier Editora Ltda. Este ´e um artigo Open Access sob uma licenc¸a CC BY (http:// creativecommons.org/licenses/by/4.0/).
Introduction
Suddenhearingloss(SHL)isanotorhinolaryngological emer-gency defined as a hearing loss of at least 30dB, at threeconsecutiveaudiometricfrequencies,ofsuddenonset within 72h.1 In most cases, it manifests unilaterally in
individuals in the fourth decade of life,1 with no gender
preference.2 Itsincidence in developed countries is
esti-matedat5---20casesper100,000inhabitants/year.1
ThepathophysiologyofSHLisnotyetfullyestablished. Some associations with viral infections, vascular
disor-ders, andautoimmunediseaseshavebeen reportedinthe literature.3However,inmostcasestheetiologyisstill
con-sideredidiopathic.1
Inadditiontodamagetothehearingfunction,SHLcan leadtochangesinvestibularfunction.4 Itisbelieved that
canbeexplainedbythehypothesisoftheextentofthe dis-easeduetoanatomicalproximity.5Somestudiesshowthat
hearingrecovery seemstobebetterin patientswith nor-malresultsincalorictestingandvestibularevokedmyogenic potential(VEMP).4,6However,theassociationbetween
hear-inglevelandvestibulardysfunctioninSHLpatientsremains inconclusive.4
Severalmedicationshavebeeninvestigatedforthe treat-mentofSHL.However,systemiccorticosteroidshavebeen recommendedasthedrugofchoice.7Analternativeto
sys-temictreatmentisintratympanictherapy,whichhasalower riskofsystemicsideeffects,allowingmedicationtodirectly penetratethecochleaandreachahighconcentration,even whenusedatlowdoses.Intratympanictherapyisconsidered tobeasecond-linetherapyandisrecommendedforcases where hearing recoveryhas not occurred aftertreatment withoralcorticosteroids.8
Somefactorsrelatedtoprognosishavebeendescribed, suchasage,presenceofvertigo,severity,andaudiometric pattern of hearing loss, VEMP, evokedauditory brainstem response(ABR), andotoacousticemissions (OAE).9Studies
have observed that hyporeflexivity in caloric testing, the absenceofV-waveintheABR,thelackofresponseinVEMP, andabsenceofOAEareassociatedwithaworseprognosisof SHL.5,10,11 However,thereisstillcontroversyregardingthe
resultsofthesestudies.
VEMPisashort-latencyevokedpotentialthatallowsthe noninvasiveassessmentoftheotolithicsystemfunctionand vestibulospinal and vestibulo-ocular pathways.3 It can be
dividedintocervicalvestibularevokedmyogenicpotential (cVEMP) and ocular vestibular evoked myogenic potential (oVEMP). cVEMP assesses the saccule, inferior vestibular nerve,lateralvestibularnucleus,vestibulospinaltract,and sternocleidomastoidmuscle.TheoVEMPmainlyreflectsthe functionoftheutricleandsuperiorvestibularnerve.
In some studies, a greater number of patients with profound hearing loss have been found to have abnormal VEMPresults.4However,insomecases,noassociationwas
observed between VEMP alterations and hearing level.4
Therefore, the findings of the VEMP role in predict-ing the auditory prognosis of patients with SHL are still controversial.12
Finally, thisreviewaimstoevaluatethe importanceof VEMPinSHL,summarizingtheavailabledataonthe alter-ations of this test in the prognosis of patients with this disease.
Methods
Datasourcesandsearchstrategy
A systematic review on VEMP in SHL was performed using MeSH descriptors in the PubMed, Cochrane, VHL andLILACSdatabasesforstudiespublisheduntilDecember 2018. After combining specific keywords (‘‘sudden deaf-ness,‘‘suddenhearingloss’’,‘‘suddensensorineuralhearing loss, ‘‘VEMP’’, ‘‘vestibular evoked myogenic potential’’, ‘‘vestibularevokedmyogenicpotentials’’),articleswritten inEnglish,PortugueseandSpanishwereselectedmanually. Anadditionalbibliographicresearchwasperformedto pro-videspecificinformationregardingVEMPandSHL.
Eligibilitycriteriaforstudyselection
Thefollowing eligibilitycriteriawereusedforinclusionin the analysis of this review: retrospective or prospective evaluationthroughcervicalorocularVEMPinpatientswith suddenhearinglossandinformationonassociatedvestibular
symptoms.Casereports,bookchapters,systematicreviews, andstudiesthatdidnotprovide sufficientinformationfor theanalysisinthisprojectwereexcluded.
Dataextraction
Thenecessaryinformationanddatawereextractedfromthe selectedstudiesandquantifiedusingastandardized proce-dure.Thecharacteristicsofeachstudywereevaluated,such asyear of publication,studydesign, age,gender, number ofassessedpatients,laterality,presenceofvertigoand/or dizziness,momentofVEMPperformance, abnormalitiesin cVEMPoroVEMP(thefollowingwereconsideredalterations: absent or asymmetric response and change in latency), auditory recovery and moment of the final audiometric assessment. The hearingrecovery criteria wasconsidered as any improvement from 10 decibels on the average of at least four frequencies of the initial tonal audiometry, regardlessoftheclassification(total,partialor mild)used inthestudies.
Methodologicalqualityassessment
The assessment of quality and risk of bias of the ana-lyzedstudies was performed using the Agency for health careresearchandquality(AHRQ)checklist.13 Thislisthas
11 evaluation criteria, including source of information, inclusion andexclusion criteria, time period,consecutive patients,masking,qualityassurance,explanationfor exclu-sions, confounder control, incomplete data withdrawal, datacollection and follow up.One item is scored as1 if included in the article and0 ifit is not. A scoreof 8 or higherindicatesahigh-qualitystudy(Table1).
Results
Accordingtotheabovementionedcriteria,62articleswere initially selected. Of these, 25 were excluded by the abstract,2becausetheyweresystematicreviews,1because it was a book chapter and 8 articles because they were writtenin Chinese.Of the26 remainingarticles, 10were excluded after reading the full article, as they did not providesufficientinformationtoverifythemethodological qualityrequiredforinclusioninthisstudy.Finally,16articles metthenecessarycriteriaforthefinalreview(Fig.1).
Clinicaldataandcomplementaryexaminationsofthe16 selectedarticlesarelistedinTable2,indescendingorder of publicationdate, and the parameters usedto perform VEMP(cervicalandocular)arelistedinTable3.Eight stud-ieswereprospective,1,12,14---19sixwereretrospective,3---6,20,21
one study contained part of the data from a retrospec-tiveanalysisandtheotherpartfromaprospectiveanalysis (consideredasretrospective/prospective),22andonewasa
cross-sectionalstudy.23 Atotalof872patientswere
evalu-ated,ofwhich50.22%weremalesand49.77%females,with a mean age of 51.26 years. Four hundredand twenty-six patients (50.35%) had vertigo and/or dizzinessassociated with the SHL. cVEMP was performed in all articles, but oVEMPonlyin 7ofthem.1,3,4,6,15,21,22 Of846ears inwhich
250 MaiaNPetal.
Table1 QualitycontrolofselectedstudiesaccordingtotheAgencyforHealthCareResearchandQuality(AHRQ)criteria. Articles QualityoftheArticleaccordingtoAHRQ
A B C D E F G H I J K Score Liu,Jetal. 1 1 1 1 0 1 1 1 0 1 0 8 Chen,YH,Young,YH 1 1 1 1 0 1 1 1 0 0 1 8 Pogsonetal. 1 1 1 1 1 1 1 1 0 1 1 10 Niuetal. 1 1 1 1 0 1 1 1 0 1 0 8 Leeetal. 1 1 1 1 1 1 0 1 0 1 0 8 Fujimotoetal. 1 1 1 0 1 1 0 1 0 1 0 7 Nagaietal. 1 1 1 1 0 1 0 1 0 1 1 8 Youetal. 1 1 1 0 1 1 1 1 1 1 0 9 Oiticica,etal. 1 1 1 1 0 1 1 1 0 1 1 9 Ogawaetal. 1 1 0 1 0 1 1 1 0 1 1 8 Korresetal. 1 1 1 1 1 1 1 1 1 1 1 11 Stamatiouetal. 1 1 1 0 1 1 1 1 1 1 0 9 Hongetal. 1 1 1 0 0 1 1 1 1 1 1 9 Chen,CN,Young,YH 1 1 1 0 0 0 0 1 0 1 1 6 Iwasakietal. 1 1 1 1 0 1 1 1 0 1 1 9 Wu,CC,Young,YH 1 1 1 1 0 0 0 1 0 1 1 8
A,sourceofinformation;B,inclusionandexclusioncriteria;C:timeperiod;D,consecutivepatients;E,masking;F,qualityassurance; G,explanationofexclusions;H,controlofconfounders;I,incompletedatawithdrawal;J,dataintegrity;K,follow-up;1,present;0, notpresentornotclear.
Selected articles in the electronic database
n=62
Articles excluded by abstract, type of study and language
n=36
Articles included in the study by title or abstract
n=26
Articles excluded for not providing enough data for analysis
n=10
Articles included in the systematic review
n=16
Figure 1 Flowchart ofarticle selection for the systematic review.
(38,65%). The oVEMP showed abnormalities in 181 ears (47.88%),of the378 evaluated ones. The auditory recov-eryratewasanalyzedbyonlyeightarticles.1,5,6,12,14,15,18,20
Twohundredandsixty(63.4%)of410evaluatedearsshowed auditoryrecovery.
Discussion
Suddenhearinglossisarelativelycommoneventin otorhi-nolaryngologyandhasbeenextensivelystudiedsinceitsfirst
descriptionintheliterature.24 However,todateits
patho-physiologyandtheinvolvedprognosticfactorsarenotfully understood.5,25 Inadditiontocochlear symptoms,SHLcan
alsoaffectthevestibularsystem.However,itisimportantto notethatthepresenceofdizzinessisnotmandatory,even with vestibular involvement. Several studies have shown thatage,thepresenceofvertigo,thetypeofhearingloss onaudiometry,thetimebetweendiagnosisandtreatment, calorictestingandVEMPcanbeprognosticfactorsforthis disease. However,many of these correlationsare not yet fullyestablished.6
Findingsabout prognosis and vestibularinvolvement in SHLareuncertain,whichmotivatedthisreview.The VEMP is acomplementarytest, abletoevaluatethefunction of otolithic organs. The cVEMPmainly evaluates thesaccule and inferior vestibular nerve, while oVEMP evaluates the utricleandsuperiorvestibularnerve.Therefore,wedecided toanalyzetheimportanceofVEMPintheprognostic assess-mentofpatientswithSHLbasedonarticlespublishedinthe literature.
The VEMP examination can be performed using click soundortoneburststimuliindBSPL(decibelsoundpressure level) or dB HL (decibelhearing level).26 Because a
high-intensity soundis required forauditory stimulation,there is concern about exposure to VEMP sound stimuli.26 The
sound intensities shouldbe limitedtosafe levelsand the totalenergy deliveredtotheearshouldbe within accep-table limits.26 A 0.1msclick of139dBSPL givenat 5/sec
andpresentedateachearforupto4.8min,forinstance,is withinsafelimitsforsoundexposure.27Therefore,theway
theexamisperformeddoesnotimplyhearingdamage.26,27
Itisalsonoteworthythattherewasnohearingdeterioration inpatientsafterVEMPinallanalyzedstudiesinthisreview. Ofthesevenarticlesthatsimultaneouslyevaluatedboth exams(cVEMPandoVEMP),fourshowedahighernumberof
in the prognosis of sudden hearing loss ---a systematic review 251
Table2 Assessedcharacteristicsoftheselectedstudies.
Authors Year Study Patients(M/F) Laterality Age Vertigoand/or
dizziness
Test perfor-mance
AlteredcVEMPa AlteredoVEMPb Auditoryrecovery
--- timec Liu,Jetal. 2017 R 35(9/26) U 41.9 21 --- 17(48.5%)/35 22(62.8%)/35 ---Chen,YH, Young,YH 2016 P 5(4/1) B 45.6 --- D 2(100%)/2 4(100%)/4 5(50%)--- 3 Pogsonetal. 2016 R/Pd 27(17/10) U 57.3 27 De 9(33.3%)/27 19(70.3%)/27 ---Niuetal. 2015 R 149(72/77) U 44.28 87 --- 73(48.9%)/149 84(56.3%)/149 ---Leeetal. 2014 R 92(55/37) U 51.21 52 D 29(31.5%)/92 --- 64(69.5%)--- 2 Fujimotoetal. 2014 R 25(15/10) U 63.6 25 --- 16(64%)/25 10(43%)/23 ---Nagaietal. 2014 P 65(35/30) U 48.9 25 D 27(41.5%)/65 6(9.2%)/65 52(80%)--- 1 Youetal. 2014 R 75(42/33) U 54 48 D 35(47%)/75 36(48%)/75 45(60%)--- 3 Oiticica,etal. 2013 C 21(8/13) U 52.5 --- --- 5(35.7%)/14 --- ---Ogawaetal. 2012 P 80(43/37) U 56.4 36 --- 24(42.1%)/57 --- 47(58.7%)---1 Korresetal. 2011 P 104(48/56) U 52.5 36 D 30(28.8%)/104 --- ---Stamatiou etal. 2009 P 86(39/47) U 51 31 D 26(30.2%)/86 --- ---Hongetal. 2008 P 52(22/30) U 55.1 0 D 14(26.9%)/52 --- 34(65.3%)---1 Chen,CN, Young,YH 2006 P 14(7/7) U 48 5 D 3(21%)/21 --- 5(35.7%)---3 Iwasakietal. 2005 R 22(14/8) U 54 22 D 17(77%)/22 --- 8(36.3%)---f Wu,CC,Young, YH 2002 P 20(8/12) U 44 11 --- 0(0%)/20 ---
---M,male;F,Female;P,Prospective;R,Retrospective;C,Cross-sectional;U,Unilateral;B,Bilateral;D,Testsperformedatdiagnosisorwithin15days;cVEMP,Cervicalvestibularevoked myogenicpotential;oVEMP,Ocularvestibularevokedmyogenicpotential;
a NumberofearswithalteredcVEMP(%)/totaltestedears. b NumberofearswithalteredoVEMP(%)/totaltestedears.
c Earsthatshowedauditoryrecoveryinrelationtoaffectedears---moment(inmonths)offinalaudiometricevaluation. d Until2011,thestudyuseddatafromretrospectiveanalysis,whenitbecameprospective.
e 2patientsunderwenttestsbetween31---49daysafterdiagnosisandnotonthedayofdiagnosis. f Performedafterseveralweeks(unspecified).
252 MaiaNPetal.
Table3 ParametersusedtoperformVEMP(cervicalandocular)intheanalyzedstudies.
Authors Year cVEMP oVEMP
Stimulusused AlterationCriteria Stimulusused AlterationCriteria Liu,Jetal. 2017 Airconductiontone
burst(500Hz100dBnHL) AR>36%;reduced orabsent amplitude; delayedresponse Airconduction toneburst(500Hz, 100dBnHL) AR>40%;absent response Chen,YH, Young,YH 2016 Boneconduction(500Hz 144dBforcelevel) --- Boneconduction (500Hz144dB forcelevel)
---Pogsonetal. 2016 Airconductionclick (105dBnHL140dBSPL)
AR>39,6% Boneconduction (147dBforce level)
AR>39,9%
Niuetal. 2015 Airconductiontone burst(500Hz131dBSPL)
Absentresponse Airconduction toneburst(500Hz 131dBSPL)
Absentresponse
Leeetal. 2014 Airconductionclick Amplitude difference>20% betweenears; absentresponse
---
---Fujimotoetal. 2014 Airconductiontone burst(500Hz95dBnHL 135SPL) AR>34%;absent response Boneconduction toneburst(500Hz 128dBforcelevel) AR>27,3%;absent response
Nagaietal. 2014 Airconductionclick (105dBnHL)
Ratio<0,5 Boneconduction (500Hz115dB forcelevel)
AR>49,7%;absent response
Youetal. 2014 Boneconduction(500Hz 128dBforcelevel) AR>33%;delayed response Boneconduction (500Hz128dB forcelevel) AR>40%;absent response Oiticica,etal. 2013 Airconductiontone
burst(500Hz95dBHL)
AR>40%;absent response
---
---Ogawaetal. 2012 Airconductionclick (105dBnHL)
Ratio<0,5 --- ---Korresetal. 2011 Airconductiontone
burst(500Hz95dBHL)
Absentresponse --- ---Stamatiou
etal.
2009 Airconductiontone burst(500Hz95dBHL)
Absentresponse --- ---Hongetal. 2008 Airconductionclick
(95dBnHL) Late, Asymmetrical,or AbsentResponse --- ---Chen,CN, Young,YH
2006 Airconductiontone burst(500Hz95dBHL)
--- ---
---Iwasakietal. 2005 Airconductionclick (95dBnHL)
--- ---
---Wu,CC,Young, YH
2002 Airconductiontone burst(500Hz95dBHL)
Ratio>0.33 ---
---−,notinformed;Db,decibel;HL:hearinglevel;Hz,Hertz;AR,asymmetryratio;Nhl,NormalHearingLevel;Ratio,ratiobetweenthe amplitudeofthebiphasicpotentialoftheaffectedsideandthatofthehealthyside;SPL,soundpressurelevel.
patients withchanges in oVEMP than in the cVEMP3,4,6,22;
one article showed a similar number of changes in both exams1andtwohadahighernumberofpatientswithaltered
cVEMPcomparedtooVEMP.15,21Consideringalargernumber
ofpatientswithSHLandalteredcVEMPintheirstudies, Fuji-motoetal.andNagaietal.suggestedthatthesacculecould bemoreeasilydamagedthantheutricle.15,21Thiscouldbe
relatedtothefindingofmicroscopictemporalbonestudies, whichshowedthatlossofvestibularhaircellsinSHLpatients
wasmorefrequentlyobservedinthesacculeandlessinthe utricle and semicircularcanals.21 On the other hand, the
articles thatshowed ahigher prevalence of patientswith SHLandalteredoVEMPsuggestedthattheutriclecouldbe morepronetodamagethanthesaccule.3,4,6,22 Theauthors
state thatthisfindingmayberelatedtothefactthatthe bone canal is verynarrow,making thesuperior vestibular nerve more susceptible to ischemic labyrinth changes or othercomplicationswhencomparedtotheinferior
vestibu-larnerve.28 Thus,itisstilluncertain whichotolithicorgan
istheonemostoftenaffectedand,therefore,thereisstill insufficientdatatostatewhichVEMP(ocularorcervical)is morespecificindeterminingprognosis.
The auditory recovery of SHL patients and associated factors wasalsoanalyzed in this review.Of thereviewed articles,sixshowedthatalteredVEMPinSHLpatientswas associatedwithpoorhearingrecovery.1,5,6,15,20,21Hongetal.
didnotobservetheassociationofalteredcVEMPwiththe patients’ poorer auditory prognosis.12 In contrast to the
describedarticles,Wu,CCandYoung,YHshowedno alter-ation in cVEMP of the assessed SHL patients.19 Stamatiou
etal.observedthattheseverityofvestibularlesioninSHL casesseemstoincreasewithage,afactattributedtothe degenerationofvestibularstructuresthatalreadyoccurin olderindividuals.17Korresetal.suggestedthatmoresevere
hearinglossandadvancedageactedasindependent nega-tivepredictive factorsforauditory recovery,evenwithor withoutlabyrinthineinjury,assessedbycVEMP.16 TheVEMP
(cervicalandocular)wasalteredin41.5%oftheexamined earsin the studiesanalyzed in thisreview.However,only eight studies analyzed the rate of auditory recovery, and thepresenceofalteredVEMPwasaworseprognosticfactor in6ofthem.Therefore,theVEMPshouldbeconsideredas aresourceintheevaluationofpatientswithSHL.
Some limitationsof theanalyzedarticlesarenotbeing multicentricorcase-controlorcohortstudies;samplesize; no data masking and lack of a prolonged follow-up. The investigation of sudden hearing loss with several tests, including vestibular evoked myogenic potential (cervical andocular),VideoHeadImpulseTest(vHIT)and videonys-tagmographycould betterclarify thepathophysiology and extent(thestructuresaffectedintheinnerear)ofthe dis-ease,inadditiontobeingusefulasaprognosticassessment toolforauditoryrecoveryinpatientswithSHL.
Conclusion
The studiessuggest thatthevestibularsystemassessment usingVEMPseemstobeimportantintheprognosisofsudden hearingloss.Forbetterfollow-up ofpatientswithsudden hearing loss, the emphasis should not be limited to the cochlea, but also include the diagnosis and treatment of vestibularalterations,regardlessofthepresenceofvertigo.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
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