Braz. j. . vol.83 número4

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www.bjorl.org

Brazilian

Journal

of

OTORHINOLARYNGOLOGY

ORIGINAL

ARTICLE

Evaluation

of

vestibular

evoked

myogenic

potentials

(VEMP)

and

electrocochleography

for

the

diagnosis

of

Ménière’s

disease

夽

Pauliana

Lamounier

a,b

,

Thiago

Silva

Almeida

de

Souza

c

,

Debora

Aparecida

Gobbo

b

_,

_Fayez

_Bahmad

_Jr.

a,d,∗

a_Universidade_de_Brasília_(UNB),_Ciências_da_Saúde,_Brasília,_DF,_Brazil

b_Centro_de_{Reabilitac¸ão}_e_{Readaptac¸ão}_Dr._Henrique_Santillo_(CRER-GO),_Goiânia,_GO,_Brazil

c_Pontifícia_Universidade_Católica_de_Goiás_(PUC-GO),_Goiânia,_GO,_Brazil

d_Instituto_Brasiliense_de_{Otorrinolaringologia,}_Brasília,_DF,_Brazil

Received19October2015;accepted14April2016 Availableonline2June2016

KEYWORDS

Ménière’sdisease; Electrocochleography; Vestibularevoked myogenicpotential

Abstract

Introduction:Ménière’sdisease(MD)isaninnereardisordercharacterizedbyepisodicvertigo, tinnitus,earfullness,andfluctuatinghearing.Itsdiagnosiscanbeespeciallydifficultincases wherevestibular symptomsarepresentinisolation(vestibularMD).The definitivediagnosis ismadehistologicallyandcanonlybeperformedpost-mortem,afteranalysisofthetemporal bone.Endolymphatichydropsisahistopathologicalfindingofthediseaseandoccursmoreoften inthecochleaandsaccule,followedbytheutricleandsemicircularcanals.Vestibularevoked myogenicpotentials(VEMP)emergedasthemethodofassessmentofvestibularfunctionin1994. Untilthen,therewasnouniquewayofassessingsaccularfunctionandtheinferiorvestibular nerve.Giventhatthesacculeisresponsibleformostcasesofseverehydrops,VEMPappearsas anewtooltoassistinthediagnosisofMD.

Objective:To evaluate the sensitivity and specificity of VEMP and electrocochleography (EcochG)inthediagnosisofdefiniteMDcomparedwithclinicaldiagnosis.

Methods:Thestudyincludes12patients(24ears)diagnosedwithdefiniteMDdefinedaccording totheclinicalcriteriaproposedbytheAmericanAcademyofOtolaryngology---HeadandNeck Surgery(AAO-HNS)in1995,aswellas12healthyvolunteersallocatedtothecontrolgroup(24 ears).A clinicaldiagnosis bytheAAO-HNScriteria wasconsideredasthegold standard.All

夽 _Please_cite_this_article_as:_Lamounier_P,_de_Souza_TS,_Gobbo_DA,_Bahmad_Jr._F._Evaluation_of_vestibular_evoked_myogenic_potentials_(VEMP) andelectrocochleographyforthediagnosisofMénière’sdisease.BrazJOtorhinolaryngol.2017;83:394---403.

∗_{Corresponding}_author.

E-mail:fayezbjr@gmail.com(F.BahmadJr.).

PeerReviewundertheresponsibilityofAssociac¸aoBrasileiradeOtorrinolaringologiaeCirurgiaCervico-Facial.

http://dx.doi.org/10.1016/j.bjorl.2016.04.021

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patientsunderwentanotoneurologicalexamination,includingpuretoneandspeech audiome-try,VEMP,andextratympanicEcochG.Thesensitivityandspecificitytodetectthepresenceor absenceofdiseasewerecalculated,aswellastheir95%confidenceintervals.Thereliabilityof VEMPandEcochGinbothearswasassessedusingthekappaindex.

Results:In bothtestsandinbothears,theabilitytodiagnosehealthycaseswashigh,with specificityrangingfrom84.6%to100%.Moreover,theabilityoftheteststodiagnosethedisease variedfromlowtomoderatesensitivity,withvaluesrangingfrom37.5%to63.6%.Theagreement ofbothtestsintherightear,measuredbythekappacoefficient,wasequalto0.54(95%CI: 0.20---0.89),indicatingamoderateagreement.Intheleftear,thatagreementwasequalto0.07 (95%CI:−0.33to0.46),indicatingaweakcorrelationbetweenthetests.Thesensitivityofthe VEMPfortherightearwas63.6%andfortheleftear,62.5%.ThesensitivityofEcochGforthe rightearwas63.6%and37.5%fortheleftear.

Conclusion: Thespecificityofbothtestswashigh,andthesensitivityofVEMPwashigherthan thatofEcochG.

© 2017 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-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

Doenc¸adeMénière; Eletrococleografia; Potencialevocado miogênicovestibular

Avaliac¸ãodospotenciaisevocadosmiogênicosvestibulares(VEMP)e eletrococleografianodiagnósticodadoenc¸adeMénière

Resumo

Introdução: A Doença de Ménière (DM) é uma doença daorelha interna caracterizada por vertigemepisódica,zumbido,plenitudeaural,eaudiçãoflutuante.Seudiagnósticopodeser especialmentedifícilnoscasosemqueossintomasvestibularesestãopresentesisoladamente (DMvestibular).Odiagnósticodecertezaéhistológicoesomentepodeserrealizadonopost mortem,apósanálisedoossotemporal.Ahidropisiaendolinfáticaéumachadohistopatológico dadoençaeocorremaisfrequentementenacócleaesáculo,seguidospeloutrículoecanais semicirculares.Ospotenciaisevocadosmiogênicosvestibulares(VEMP)surgiramcomométodo deavaliaçãodafunçãovestibulardesde1994.Atéentãonãohaviaumamaneiraexclusivade avaliaçãodafunçãosacular edonervovestibular inferioresendoosáculoresponsávelpor grandepartedoscasosdehidropisiasevera,oVEMPaparececomoumanovaferramentapara auxiliarnodiagnósticodaDM.

Objetivo: AvaliarasensibilidadeeespecificidadedoVEMPedaEletrococleografia(ECochG)no diagnósticodaDMemcomparac¸ãocomodiagnósticoclínico.

Método: :Foramselecionados12 pacientes(24 orelhas)comdiagnósticodeDMdefinidade acordocomoscritériosclínicospropostospelaAmericanAcademyofOtolaryngology-Headand NeckSurgery1995(AAO-HNS)e12voluntáriossaudáveisalocadosnogrupocontrole(24orelhas). Considerou-seodiagnósticoclínicopelaAAO-HNScomopadrãoouro.Todosospacientesforam submetidos aexame otoneurológico,incluindoaudiometriatonal evocal, VEMP e eletroco-cleografiaextratimpânica.Asensibilidadeeespecificidadeparadetectarapresençaouausência dedoençaforamcalculadaseosrespectivosintervalosdeconfiançade95%obtidos.A confia-bilidadedostestesdediagnósticoVEMPeeletrococleografiaemambasasorelhasfoiavaliada peloíndicekappa.

Resultados: Em ambosos testes eem ambasas orelhas,acapacidade para diagnosticaros casos saudáveis éalta,aespecificidade variandode84,6%---100%. Alémdisso, acapacidade dostestesparaodiagnósticodadoenc¸avariadebaixaamoderadasensibilidade,comvalores de37,5%---63,6%.Aconcordânciadosdoistestesnaorelhadireita,medidapelocoeficientede kappafoiiguala0,54;com95%IC(0,20---0,89),indicandoumaconcordânciamoderada.Para aorelhaesquerdaessaconcordânciafoiiguala0,07com95%IC(-0,33---0,46),indicandouma concordânciafracaentreostestes.AsensibilidadedoVEMPparaaorelhadireitafoide63,6%e paraaorelhaesquerda,de62,5%.AsensibilidadedaECochGparaaorelhadireitafoide63,6% e37,5%paraaorelhaesquerda.

Conclusão:AespecificidadedeambosostestesfoialtaeasensibilidadedoVEMPfoimaiorque adaeletrococleografia.

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Introduction

Ménière’s disease (MD) is an inner ear disorder

charac-terized by episodic vertigo, tinnitus, ear fullness, and

fluctuatinghearing.Thedefinitivediagnosisismade

histo-logically, and can only be performed post-mortem, after

analysis of the temporal bone. In 1995, the American

AcademyofOtolaryngology---HeadandNeckSurgery

(AAO-HNS)1 _developed _diagnostic_criteria _that_are _widely _used.

Recently,theBáránySocietydevelopedanewguidelinefor

the diagnosis of MD; after an evolutionary understanding

of MD and vestibular migraine, the most common

differ-ential diagnosis, the need to update these criteria was

highlighted.2

For a long time, it was believed that endolymphatic

hydrops would be the histopathological substrate of the

disease;thisoccursmoreofteninthecochleaandsaccule,

followedbytheutricleandsemicircularchannels.3,4_Recent

studies have indicated that hydrops is a finding of the

MD,together withthe symptoms, sinceit alone does not

explainalltheclinicalfeatures,includingtheprogressionof

hearinglossandthefrequencyofvertigoattacks.According

to the criteria of the AAO-HNS, individuals with two or

more spontaneous episodes of vertigo, lasting ≥20min,

with documented hearing loss in at least one occasion

and tinnitus or ear fullness are clinically classified as

havingdefiniteMD.The diseaseiscalled probablewhena

definedepisodeofvertigo inthepresenceof documented

sensorineural hearing loss in at least one occasion, ear

fullness, or tinnitus. MD is also classified as possible in

the presence of Ménière-type episodic vertigo without

documented hearing loss or when there is sensorineural

hearingloss,fixed or floating,associatedwithimbalance,

withoutadefinedepisodeofdizziness.1

According to the criteria of the Bárány Society, MD

is classified as definite or probable. In definite MD, the

patientshouldhavehadtwoormorespontaneousepisodes

of vertigo, each lasting from 20min to 12h; documented

mild to moderate sensorineural hearing loss; aural

symp-toms(hearing, tinnitus,andfullness) inthe affected ear;

and exclusion of other vestibular disorders that explain

the symptoms. In probable MD, the patient should have

had two or more episodes of vertigo or loss of

bal-ance, each lasting from 20min to 24h; floating aural

symptoms(hearing, tinnitus, or fullness) in that ear;and

exclusion of other vestibular disorders that explain the

symptoms.2

The cause of hydrops is still unknown, and most

theoriesarebasedonthechange inproduction or

resorp-tion of endolymph. In 1982, Schuknecht5 _postulated _that

hydrops causes rupture of Reissner’s membrane, allowing

theendolymphaticfluid,richin potassium,tocontactthe

perilymph andreach the surfaceof the ciliated cells and

thevestibulocochlearnerve,causinghearinglossandvertigo

attacks.Somebelievethateventhedistensionofthebasilar

membranebytheendolymphatichydropsmayalreadylead

todegenerationof ciliated cells andtherefore their

mal-function,causing adecreasein theaction potential(AP).6

Anatomicalandvascularabnormalitiesarepossiblyrelated

toitsetiopathogenesis.

In 1989, Rauch et al. found histological evidence of

endolymphatichydropsin13outof13casesofpatientswith

MD,butareviewofmedicalrecordsofsixoutof19

tempo-ralboneswithendolymphatichydropsrevealednosignsor

symptomsofMD.Theyobservedthatmanyinnerearshave

endolymphatichydropswithoutclinicalsyndrome

manifes-tation. Some suggest that endolymphatic hydropsmay be

anepiphenomenonofthepathophysiologicalmechanismof

MD.7

The hypothesis of genetic predisposition is widely

accepted,sinceapositivefamilyhistoryispresentinmany

patients with MD. Research shows that the disease could

result from mutations in the short arm of chromosome

6, where the histocompatibility antigen (HLA) is located;

such mutations would be synergistic to the development

ofMD.Approximately7%ofpatientswithfamilialMDhave

an autosomaldominantmodel with60% penetrance anda

geneticpatternofanticipation, inwhichthenext

genera-tionwiththedisease willpresentmore intensesymptoms

with earlier onset.6,8 _Genetic _studies _in _families _suggest

that the genetic mechanism associated with MD is

com-plexandthatthereismorethanonegeneinvolvedinmost

cases.6,8,9

Asotherinnereardisorders,MDhasalsobeenregarded

as an autoimmune disease, as evidenced by a

rela-tionship with circulating immune complexes, suggesting

deposition in the endolymphatic sac.6,9 _The _autoimmune

theory has also been strengthened by recent evidence

of anti-endolymphatic sac auto-antibodies in the serum

of patients with MD. Inhalant and food allergies have

been associated with MD and, in many cases, allergic

patientsimprovedtheirsymptomsafterspecificantiallergic

therapy.6,9,10

Electrocochleography(EcochG) hasbeen usedforyears

in thediagnosis ofendolymphatic hydropsinthe cochlea.

Itsclinicalapplication,however,isstillcontroversialamong

otorhinolaryngologistsbecauseofitsvariablesensitivity,as

incasesofhearinglossduetodiseaseprogression,patients

mayexperienceareductionintheamplitudeofAPdueto

lossofauditorynervefibers.11,12

Vestibularevokedmyogenicpotentials(VEMP)emerged

as a method to assess vestibular function in 1994, when

Colebatch andHalmagyi reportedsurface potentialin the

sternocleidomastoid (SCM) muscle in response to clicks

through high-intensity air conduction (100dB),

access-ing the sacculo-collic reflex.13,14 _These _potentials _assess

the saccular and inferior vestibular nerve function, and

are absent or decreased by 30---54% in patients with

MD. The exam is easy to perform, does not cause

dis-comfort to patient, and does not vary with hearing

loss.13---15 _VEMP _can _be _obtained _by _air _and _bone

conduc-tionandgalvanicstimulation,usingtoneburstorclicksas

stimulus.14---16

ThediagnosisofMDcanbedifficult,especiallyincases

where vestibularsymptomsarepresent inisolation

(vesti-bular MD).17 _Until _1994, _there _was _no _unique _method _to

assess saccular and inferior vestibularnerve function.17,18

Asthesacculeisthesecondmostprevalentaffectedsiteof

endolymphatichydrops,representingmostformsofsevere

hydrops,VEMPappearsasanauxiliarytoolinthediagnosis

ofMD.18,19

Thisstudyaimedtoassessthesensitivityandspecificity

ofVEMPandEcochGinthediagnosis ofMD,aswell asthe

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Methods

This was a clinical, prospective trial, which selected 12

patients (24 ears) diagnosed with definite MD according

tothe clinical criteriaproposed by theAAO-HNS in1995,

of whom seven were females and five were male, aged

between 33 and63 yearswitha mean of48.41 years; 12

healthyindividuals,sex-andage-matched,wereallocated

tothecontrolgroup(24ears).Theexclusioncriteriawere

impossibilityofcervicalrotationandmiddleorexternalear

disease. The two researchers who conducted the

assess-mentswereunawareofthegrouptowhichthepatienthad

beenallocated.

The study was approved by the Research Ethics

Committee under opinion No. 10668613.2.0000.0030. All

participantssignedaninformedconsentforinclusioninthe

study.

ClinicaldiagnosisbytheAAO-HNS1995criteriawas

con-sidered as the gold standard, and all patients underwent

otorhinolaryngological and otoneurological examinations,

including pure tone and speech audiometry, VEMP, and

extratympanicEcochG.

Clinical history was taken and a physical examination

wasconducted;thedifferentialdiagnosiswasexcludedand

theclinicaldiagnosisofMDaccordingtotheAAO-HNS1995

criteriawasconfirmed.

Tonalandspeechaudiometry/impedance

The examination was performed in all patients, with the

followinggoals:

• DiagnosehearinglosswichispartofthedefiniteMD

diag-nosticcriteriabytheAAO-HNS;

• Discardcaseswithmiddleeardiseases;and

• Discard cases with conductive loss that alters VEMP

parameters.

VEMP

TherecordingdevicewastheVivoSonicIntegrity,with

pro-grammingforevokedpotentials,usingaspecificprotocolfor

performingtheVEMP.Myogenicpotentialsarepickedupby

electrodesplaced onthe patient’sSCMmuscle(ipsilateral

tothesoundstimulus),thereferenceelectrode(negative)

isplacedontopoftheSCM;theactiveelectrode(positive),

onthesternum;andtheground,ontheforehead.Patients

wereinstructedtoturntheirheadintheoppositedirection

tothesoundstimulus,sothattherewasacontractionofthe

SCMmuscle(Fig.1).

Stimulusandresponseacquisitionparameters

150toneburststimuliwereused,atafrequencyof500Hz,

withtherateof7.1stimuli/s,stimuliintensityof95dBHL,

highpassfiltersof30Hzandlow-passfiltersof1000Hz,

pre-sentedthroughER-A3earphones.Therecordingsweremade

ina30-mswindow.

Thefollowinganalysiscriteriawereconsidered:presence

or absenceofreproduciblewaves and interauralresponse

asymmetryindexfortheamplitude.

Figure1 VEMPperformedontheright.

The presence of reproducible waves and interaural

responseasymmetryindexfortheamplitudeequaltoorless

than34%characterizednormalVEMP.

Inturn,theabsenceofreproduciblewavesand/or

inter-auralresponseasymmetryindexfortheamplitudegreater

than34%characterizedalteredVEMP.

EcochG

TherecordingdevicewastheVivoSonicIntegrityand

TIP-trode electrodes were inserted in the external auditory

meatus. The ear canal was cleaned with abrasive paste.

Negativeandpositiveelectrodeswereconnectedtothe

Tip-Trodeearphone; thenegativeelectrode inthe stimulated

ear,the positive in the contralateral ear,and the ground

electrodeontheforehead(Fig.2).

Stimulusandresponseacquisitionparameters

Click stimuli were utilized (2---4kHz), at a rate of

11.3stimulus/s; intensity of 99dB HL, high-pass filters of

30Hz,andlow-passfiltersof2400Hz.Therecordingswere

madewitha5-mswindow.

AnSP/PAratiogreaterthan50%wasconsideredaltered.

Statisticalanalysis

Inordertovalidatebothdiagnostictests(VEMPandEcochG),

theclinicaldiagnosiswasconsideredasthegoldstandard.

Bothears were classified as withor without the disease,

and as test instrument, the positive or negative result

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Figure2 EcochGperformedintherightear.

the presence or absence of the disease were calculated,

aswell as their respective 95% confidence intervals. The

reliability of diagnostic tests in both ears was assessed

by kappa, using the scale proposed by Landis and Kock,

which classifies the agreement as: (≤0, poor; 0.10---0.19,

weak;0.20---0.39,regular;0.40---0.59,moderate;0.60---0.79,

substantial;0.80---0.99,almostperfect;1,perfect).The

pro-portionsof positiveand negativeresultsof thediagnostic

testswerecomparedusingMcNemar’stest.Fordata

analy-sis,SAS9.3wasused.

Thesignificancelevelwassetatp<0.05.

Results

At theVEMP, themean p13latency for thecontrol group

was 15.93ms, with standard deviation (SD) of 0.85ms.

Themean n23 latencyfor the controlgroupwas22.80ms

(SD=1.16ms). The meanasymmetry indexfor thecontrol

group was 16.22 (SD=15.58). At the EcochG, the mean

SP/APratioforthecontrolgroupwas24.39%(SD=11.61).All

Specificity measures

Right Left

VEMP

ECochG

Ear 100

90 80 70 60 50 40 30 20 10 0

%

Figure3 VEMP andECochGspecificityinthe rightandleft ears.

Sensitivity measures

VEMP

ECochG 100

90 80 70 60 50

%

40 30 20 10 0

Right Left

Ear

Figure4 VEMP andECochGsensitivityinthe rightandleft ears.

controlgrouppatientshadpuretoneandspeechaudiometry

andimpedancewithinnormallimits.

Inthestudygroup,sixcasesofbilateralMD,fivecases

ofunilateralMDintherightear,andonecaseofMDinthe

left earwere identified, totaling 11 right ears and seven

left ears. Regarding VEMP, 14 ears presented absence of

wavesandtenearsshowedthepresenceofbiphasic

wave-form;bothearsshowedthepresenceofwavesinonlythree

patients,thusenablingcalculationoftheasymmetryindex.

The mean asymmetryindex for thesepatients was11.22.

ThemeanSP/APforthecasegroupwas47.23.

Tables1 and2show theindividualresults ofthe study

groupontherightandleftears,respectively.Tables3and4

showtheindividualresultsofthecontrolgroupontheright

andleftears.

Inbothtestsandbothears,theability todiagnose the

healthycaseswashigh:thespecificityrangedfrom84.6%to

100%(Fig.3).Moreover,theabilityofthetesttodiagnose

thediseasevariedfromlowtomoderate,whicha

sensitiv-ityof37.5---63.6%(Fig.4).Table5showsthesensitivityand

specificityofbothtestsinbothears.

The agreement of both exams in the right ear,

mea-sured by the kappa coefficient, was equal to 0.54 (95%

CI: 0.20---0.89), indicating a moderate agreement. In the

leftear,thatagreementwasequalto0.07(95% CI:−0.33

to0.46), indicating a weakcorrelation betweenthe tests

(Table6).

Fortherightear,theproportionofpositiveandnegative

test VEMP results (37.5---62.5%) did notdiffer significantly

from the proportion of positive and negative results in

EcochG (33.3---66.7%; p=0.6547; Fig. 5). Forthe left ear,

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Table1 Individualresultsoftherightearinthecasegroup.

Casegrouprightear Impedance

Patient ClinicalDT VEMP EcochG Audiometry

1 Yes Normal Normal ModerateSNHL,ascending Acurve

2 Yes Altered Altered MildSNHL,flat Acurve

3 No Altered Normal Normal Acurve

4 Yes Altered Altered ModerateSNHL,flat Acurve

5 Yes Altered Altered Mildconductivehearingloss Acurve

6 Yes Normal Altered ModerateSNHL,descending Acurve

7 Yes Normal Altered MildSNHL,flat Acurve

8 Yes Normal Normal MildSNHL,flat Acurve

9 Yes Altered Normal ModerateSNHL,descending Acurve

10 Yes Altered Altered ModerateSNHL,descending Acurve

11 Yes Altered Altered MildSNHL,invertedU Acurve

12 Yes Altered Normal MildSNHL,descending Acurve

Table2 Individualresultsoftheleftearinthecasegroup.

Casegroupleftear Impedance

1 Yes Normal Altered MildSNHL,flat Acurve

2 No Normal Normal Normal Acurve

3 Yes Altered Normal MildSNHL,flat Acurve

4 Yes Normal Altered ModerateSNHL,flat Acurve

5 No Altered Normal Normal Acurve

8 Yes Altered Normal ModerateSNHL,ascending Acurve

11 Yes Altered Altered ModerateSNHL,flat Acurve

12 Yes Normal Normal MildSNHL,descending Acurve

Table3 Individualresultsoftherightearinthecontrolgroup.

Controlgrouprightear Impedance

22 No Altered Altered Normal Acurve

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Table4 Individualresultsoftheleftearinthecontrolgroup.

Controlgroupleftear Impedance

Table5 Sensitivityandspecificityvalues,bytypeoftestinbothears.

Ear Diagnostictest Clinicalexamination

Diseased Healthy

n %(95%CI) n %(95%CI)

Right

VEMP

Positive 7 63.6(30.8---89.1) 2

---Negative 4 --- 11 84.6(54.6---98.1)

EcochG

Positive 7 63.6(30.8---89.1) 1

---Negative 4 --- 12 92.3(64.0---99.8)

Left

VEMP

Positive 5 62.5(24.5---91.5) 1

---Negative 3 --- 15 93.7(69.8---99.8)

EcochG

Positive 3 37.5(8.5---75.5) 0

---Negative 5 --- 16 100.0

Table6 Agreementbetweendiagnostictests.

Ear VEMP EcochG Kappa(95%CI)

Positive Negative Total

Right

0.54(0.20to0.89)

Positive 6 3 9(37.5)

Negative 2 13 15(62.5)

Total 8(33.3) 16(66.7) 24(100.0)

Left

0.07(−0.33to0.46)

Positive 1 5 6(25.0)

Negative 2 16 18(75.0)

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Percentage of positive and negative results by exam in the right ear

100 90 80 % 70 60 50 40 30 20 10 0 Positive Negative Result VEMP ECochG

Figure5 Percentageofpositiveandnegativeresultsbyexam intherightear.

Percentage of positive and negative results by exam in the left ear

% 100 90 80 70 60 50 40 30 20 10 0 Positive Result VEMP ECochG Negative

Figure6 Percentageofpositiveandnegativeresultsbyexam intheleftear.

(25.0---75.0%) did notdiffer significantly in the proportion of positive and negative results in EcochG (12.5---87.5%; p=0.2568;Fig.6).

Discussion

12patientswithdefiniteMDandcontrolswereevaluatedby

audiometryandimpedance,VEMP,andEcochG.

In the present study,VEMP wasperformed in a sitting

position,whichaccordingtopreviousstudiesistheposition

thatprovidesbetteractivationoftheSCM.20---22 _Tone_burst

stimuliwereused,sincestimuliwithfrequenciesnear500Hz

have higher responseamplitudes.23 _The _large _variation_in

responseamplitudecausedbydifferentdegreesofmuscle

contractureobtainedforeachindividualjustifiesthe

analy-sisoftheVEMPresponsesthroughtheinterauralasymmetry

index.Basedonareviewoftheliterature,valuesabove34%

wereconsideredasaltered.22,24_However,_a_biphasic_p13-n23

wavewasobservedintenears(41.66%),whereasonlythree

patientsshowedthepresenceofwavesinbothears,

allow-ingforthecalculationoftheasymmetryindex.In1999,Seo

etal.18 _observed_biphasic_waves _in_72%_of_cases_of_MD_and

Waele,17_in_45.7%_of_cases.

14ears(58.33%)showednowavesat VEMP.Thelackof

response,aswellasasymmetryindexgreaterthan34%,

sug-gest endolymphatic hydrops.17,18,24 _{Jariengprasert} _et _al.25

observedthat theabsenceofwaves andasymmetryindex

alterationsweremoresignificantthanP1andN1latencies

oramplitudemeasuresintheidentificationofsaccular

dys-functioninMD.

Dependingontheseverityofhydrops,somepatientsmay

presentirreversibledegenerationofthesensoryepithelium

of the saccular macula, with absence of waves. In 1999,

Waele17_also_attributed_the_lack_of_VEMP_response_in_patients

withMDtoinsufficientcontractionduringtheexamination,

unrecognizedvestibularpathology,orsaccule

hyposensitiv-ityduetotheagingofthesaccularmacula intheelderly.

Thisineffectivecontractioncan beavoidedbyusing

elec-tromyographytomonitorthedegreeofmusclecontraction,

whichwasnotpossibleinthepresentstudy,sincethe

equip-mentuseddidnothavethisfeature.

TheEcochGusedinthisstudywasextratympanic,which,

according to the literature review, is an effective and

non-invasivemethodofmeasuringcochlearhydrops.26 _The

presenceofSPandAPwasobservedinallpatients.

The responsesshoweda lowtomoderate sensitivityof

VEMPandEcochGinthediagnosisofMDinrelationto

clin-icaldiagnosis.ThesensitivityoftheVEMPfortherightear

was63.6%andfortheleftear,62.5%.Itwasslightlyhigher

thanthat found in theliterature, which ranged from40%

to54%.16,17,27_The_sensitivity_of_EcochG_for_the_right_ear_was

63.6%andfortheleftear,37.5%;theliteraturevaluesrange

from57%to71%.26

The fluctuating course of the disease complicates the

interpretationofelectrophysiologicaltests.Themain

ques-tion regarding the use of diagnostic tests in MD pertains

totheir sensitivity.Egamietal.14 _observed _that,_although

the VEMP sensitivity was not high, it wascomparable to

thecalorictest,providingadditionalinformationtoidentify

vestibularabnormalitiesinMD.

Thehighspecificityofbothtestswasconsistentwith

find-ingsintheliterature,suggestingtheirhighaccuracyinruling

out the presence of disease, assisting especially in cases

wherethereisdifferentialdiagnosis.14,26

RegardingtheVEMP,twoasymptomaticearshadchanged

VEMP.Thisfindingis describedintheliteratureasaresult

ofoccultsaccularhydropsorofbinauralinteractionsinthe

otolith-cervical reflex arc of VEMP. Similar findings were

retrieved in the literature.15---18 _In _2006, _Lin _et _al. _found

that27%ofpatientswithunilateralMDshowedhigh

thresh-olds in the asymptomatic ear, demonstrating that VEMP

canbealtered evenbeforetheappearance of theclassic

symptoms of the disease, and that saccular hydrops may

precedethesymptomsofbilateralMD.19,28,29_In_2000,

Con-lonandGibson30_also_reported_abnormal_clinical_findings_in

asymptomatic ears. There are also individual differences

in the degree of muscle tone and contraction,28,31 _which

theauthorsofthepresentstudytriedtoavoidbysex-and

age-matchingthecontrolgroupandbyusingtheinteraural

asymmetryindexasaparameter.

The abilityto predictthe presence ofabnormalities in

anasymptomaticearis oneofthegreatfeaturesofVEMP.

Knowingwhether the patient has the disease in the

con-tralateralear,forexample,aidsinmakingadecisionabout

ablativeproceduresinthediseasedear.28

Seven ears with MD had normal VEMP. These ears

may have saccular macula free from hydrops, presenting

cochlearhydrops.In1987,OkunoandSando3_examined₂₆

temporalbonesofpatientswithMDanddemonstratedthat

endolymphatichydropswasobservedmostfrequentlyinthe

cochlea,followedbythesaccule,utricle,andsemicircular

(9)

ofseverehydropsrefractorytomedicaltreatmentmaybe

locatedinthesaccule.16

RegardingEcochG,noasymptomaticearhadaltered

val-ues, and nine ears with MD had normal values. Of these

ears,fivehadmoderatesensorineuralhearinglossandfour

had mild sensorineural hearing loss. Audiometric

thresh-olds around 50dB undermine the analysis of hydrops by

EcochG,32 _and _are _therefore _a _hypothesis _for _the _normal

EcochG observed in five patients with moderate hearing

loss.Theliteraturealsoreportsthatpatientswithhydrops

inotolith organs may have disease-freecochlea, which is

anotherhypothesis thatcouldapplytopatients withmild

hearingloss.AmajoradvantageofVEMPisthatthe

saccu-larmaculaissensitivetosoundevenaftertotaldestruction

ofthecochlea,andthusitcanbeperformedinindividuals

withgoodorbadhearingacuity.14,17,19

Thesamplesizewasonelimitationofthepresentstudy.

Definite MD, with document hearing loss, it is not highly

prevalent,hinderingtheselectionofpatientsforthestudy.

Forthesamereason,itwasnotpossibletocomparepatients

withthesame diseaseduration.Earswithlongerduration

ofsymptomsshowhigherabnormalitiesintheSP/APratio,

andoncetheSPrises,itpersistsforlongperiods26,33_;_that_is,

evenintheperiodbetweenattackstheEcochGcan

demon-stratecochlearhydrops.

CervicalVEMPbyairconductionmaybeincreasedinthe

earlystages ofMD,perhaps duetothe pressureof

saccu-larhydropsagainstthestapesfootplate,increasingsaccular

sensitivitytointensesound.16_Its_measurement_can_be

vari-able, with a tendency to disappear with the progression

of thedisease, aswell as duringthe 24h post-crisis,and

mayreappearafter48horwiththeuseofdrugstoreduce

endolymphatichydrops.2,11,13,34

Theagreementmeasuredbythekappacoefficient

eval-uates the similar results between both exams. The low

correlationbetweenthediagnostictestswasexpected,as

theyevaluatedifferentstructures.Furthermore,theyhave

differentsensitivitiesaccordingtothestageofthedisease;

Vemp is more altered in the symptomatic period, unlike

Ecochg,thatevenintheperiodbetweenattackscan

demon-stratecochlearhydrops.Theagreementfortheleftearwas

low,andlowerthanthatfortherightear,probablybecause

thesizeoftheleftearsamplewassmallerthanthatofthe

rightear.McNemar’stestassessedtheproportionofpositive

andnegativeresultsofVEMPandEcochG,whichwerenot

statisticallydifferentfromeachother,bothintherightand

leftears.

In the control group, the subjects were sex- and

age-matched. However,further studies could pairthe control

group for hearing loss similar tothose of patients in the

casegroupinsteadofselectingcontrolswithnormal

hear-ing, since the hearing thresholds are determining in the

sensitivityofEcochG.

The possibility of assessing saccular hydrops througha

noninvasive,easytoperformmethod,suchastheVEMP,aids

theotorhinolaryngologistindiseasemanagement.In2001,

MurosfushireportedthattheprolongationoflatencyinVEMP

suggestsretrolabyrinthine injury,facilitatingtheexclusion

ofdifferentialdiagnoses.25

Severalfactors corroboratethe aid ofadditionaltests,

such asVEMP and EcochG, in the diagnosis of MD.

Possi-bleMDcasesinwhichthereisnodocumentedhearingloss,

the heterogeneity of thedisease, andthe involvement of

variouslabyrinthinestructuresoftencomplicatethe

diagno-sis.VEMPandEcochGarecomplementarytests,sincethey

assessdifferentlabyrinthinestructures,andshouldbe

incor-poratedintoroutineotoneurologicalexaminations,aidingin

theidentificationofhydropslocationandthepossibilityof

asymptomaticearinvolvement.

Theassessmentofcochlearfunctionwithaudiometryand

EcochG,of thesacculethroughcervicalVEMP, ofthe

utri-cle throughocular VEMP, ofthe lateralsemicircular canal

through caloric tests, and of all the semicircular canals

throughvHITdemonstratestheadvancementofresearchin

thevestibulardiagnosis.Newpathsareopentothe

discov-eryofthepathophysiologicalmechanism ofadiseasethat

wasfirstdescribedoveracenturyagoandstillhasnodefined

treatmentprotocol.

Conclusion

Thespecificityofbothtestswashigh,andthesensitivityof

VEMPwashigherthanthatofEcochG.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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