Iowa VEMP-2019

10/10/19

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©2017 MFMER | slide-1

ContemporaryConceptsinVestibular-EvokedMyogenicPotentials

DevinL.McCaslin,Ph.D.DepartmentofOtorhinolaryngologyIowa-Speech-Language-HearingAssociationOctober17th2019


MayoIntegratedNeuro-VestibularTeam(MINT)

• Otolaryngology/Audiology• Neurology• BehavioralMedicine

• PhysicalTherapy• Audiology


SonomotorResponsesForsometimeithasbeenrecognizedthat…

•  Inadditiontomovement,vestibularafferentsmaybeactivatedby:

•  Soundsofhighintensity•  vibrationand•  electricalstimulationappliedoverthemastoidprocess

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Background

•  Sonomotorresponsesinclude:•  theacousticjawreflex(Meier-Ewertetal.1974)•  thepostauricularm.(PAM)potential(Kiang,1963),

•  theinionpotential(Codyetal.,1964)whichhasbecomeoneofagroupofcontemporary…

•  vestibularevokedmyogenicpotentials(VEMP)


ReincarnationoftheSonomotorResponse-VEMPHalmagyiandCurthoys,1990’s

• VEMPcanberecordedfrommusclegroupsthatreacttosound:SCM,trapezius,tricep,gastrocnemiusandquadracepsmusclesetc.etc.(e.g.Ferber-Viartetal.1998;RudisillandHain,2008)


Vestibular-evokedMyogenicPotentials

•  Sternocleidomastoid(SCM)m.

•  Trapeziusm.

• Gastrocnemiusm.

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VEMPisaSonomotor“Reflex”Whatisareflexpathway?

• Consistsof:• Areceptor(endorgan)• Anafferentpathway•  Centralconnections• Anefferentpathway,and,•  Endmuscles



OtolithOrgans

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KeyConcept!

• Weareusingsoundonlyasapressurestimulusi.e.soundpressureisbeingusedasahydro-mechanicalforcetomovetheendolymphaticfluidand,asaconsequence,totranslateotolithstocreatetransduction.

• Alowfrequencytendstoprovideagreaterpush


ReceptorforcVEMPistheSaccule?Hamagyi&Curthoys(2000)

•  Sacculeisvestibularendorganmostsensitivetosound

•  Liesunderthestapesfootplate

• Neuronsfromsaccularmacularespondtotiltsandclickstimuli


NerveofAfferentPathwayisInferiorVestibularNerve?•  Electricaloutputfromthesacculeisroutedthroughtheinferiorvestibularnerve.

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cVEMPPathway“VestibulocollicReflex”•  Saccule(a)•  Inferiorvestibularnerve(a)

• Vestibularnucleus(a)•  Ipsi.medialvestibulospinaltract(MVST)–(e)

•  SpinalaccessorynucleusofCNXI(e)

• CNXI(e)•  SCM(e)

a = afferent, e = efferent


oVEMP Pathway

• oVEMPpathway• Utricle•  Sup.Vestib.Nerve• Med.Vestib.Nuc.• MedialLongitudinalFasciculus

• MotorNucleusofContraCNIII

•  CNIII•  ContraInferiorObliquem.

Utricle

Sup VN


oVEMP Pathway is Bilateral (Response Predominates Contralaterally)

Contralateral response Present consistently Ipsilateral response

Present Inconsistently

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Nomenclaturere:Cervical(scm)VEMP(akacVEMP)

•  1stpositiveandnegativewavesarereferredtoasP13/N23(orP1/N2).

•  PositivewavesrepresentinhibitionofEMG

• NegativewaverepresentsexcitationofEMG

N1/23

P1/13


oVEMPNormalResponse

•  Inresponseto500Hztoneburst

•  N1:~10msec•  P1:~15msec

•  Contralateralresponseoccursslightlyearlierandislargerthanipsilateralresponse(contralateralpathwayisfaster)


ComparedtoAuditoryNerveFibers,VestibularAfferentsShowHighThresholdsandBroad“Tuning” BestFrequenciesandThresholdsofResponseforCochlearNeuronsandAcousticallyResponsiveIrregularVestibularAfferents(McCue&Guinan,1995)

Kiang & Moxon, 1974

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WhatstimulicanbeusedtoelicittheVEMP?

Bone conduction VEMP (CHL)

Galvanic VEMP

Mechanical (tap) VEMP (CHL)

Air conduction VEMP Sound (unilateral)

Vibration (bilateral)

Electricity (galvanic, bilateral)


B-81 – Bone-conduction VEMPs

Latency (ms)

Am

plitu

de (1

0 µV

/div

)

Air conduction

Bone conduction

oVEMPs


Bone-conduction VEMPS B-81 (Eclipse)

50 55 60 65 70 75

Amplitu

de(µv)

Stimulusintensity(dBnHL)

oVEMPAmplitude

Average

0

25

5

10

15

20

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Cervical VEMPs B-81 (Eclipse)

0

100

200

300

400

500

50 55 60 65 70 75

Amplitu

de(µ

V)

Stimulusintensity(dBnHL)

cVEMPp1-n1Amplitude

Average


KeycVEMPConcepts


MethodstoControlforEMGLevel

• Visualoracousticfeedback•  PatientcanviewEMGtargetamplitudeonaCRTduringdatacollection(orhearEMGconvertedtosound).or,

• CombineoptimizedactivationmethodwithmethodfornormalizingVEMP

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MethodstoControlforEMGLevel:Method1VisualFeedbackofEMGLevel

• RepresentationofEMGactivityisdisplayedonascreenasahorizontallymovingline

• PatientisaskedtomaintainEMGattargetlevel

Target EMG Level

Time

Amplitude Interacoustics Implementation

% completed

Trended EMG

Real-time EMG level Target Peak level


ControlforEMGLevel:AmplitudeNormalization

The process of clipping a signal or waveform such that either the positive or negative portion of it is completely eliminated.

Full-wave Rectification

Unrectified Waveform


TheGestaltoftheIdeaThecommonproblem

•  YourecordaleftearVEMPanditis3xlargerthantherightearVEMP.

• HowdoyouknowwhethertheamplitudedifferenceisduetopathologyorbecausetheEMGfromwhichtheVEMPwasextractedwas3xlargerontheleftsidecomparedtotherightside?

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GestaltoftheIdeaTheCommonProblem

•  SohowaboutifweobtainavaluethatrepresentstheaveragesizeoftheEMGontheleftsideduringsignalaveragingoftheVEMP.Samefortherightside.

•  ThenwedivideintoeachdatapointintheleftVEMPtracingthemeanEMGvalueanddothesameontherightside.Inthiswaywecannormalizethetraces.


ControllerView


AmplitudeNormalization

• RawtonicEMGactivitywascollectedoverthe100msintervalprecedingeachstimulusonset.

•  Foreachofthese100mspre-stimulationtimeblocks,anRMSvaluerepresentingtheEMGlevelofthat100mspre-stimulusintervalwascalculated.

• Attheendoftherecording,anaverageoftheindividualRMSvaluesfromalloftheobtainedpre-stimulusintervalswascalculated.

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ObtainingNormalizationValue

•  EachobtainedVEMPwaveformhasitownspecific“normalizationvalue”whichiscalculatedthisway:

•  EachEpochusedfortheaveragingoftheVEMPwaveformhasitsown100msPrestimperiod.ForeachofthesePrestimperiodstheRMSvoltageiscalculated.

•  TheaverageofallthesePrestimRMSvaluesisthe“normalizationvalue”forthisVEMPwaveform.

Stimulus Stimulus Stimulus

100ms PreStim 100ms PreStim 100ms PreStim

Recording Recording Recording

One Epoch

time in ms


WaveformsPriortoNormalization

RIGHT

P1 amplitude: 348 uV

Ave. RMS EMG: 201 uV

LEFT

P1 amplitude: 120 uV



UncorrectedAsymmetryValue

(amplitude P13-N23left – amplitude P13-N23right) Amplitude Asymmetry --------------------------------------------------------------------- X 100

(amplitude P13-N23left + amplitude P13-N23right)

( 120 uV – 348 uV) Amplitude Asymmetry -------------------------------------------- X 100 = 49% ( 120 uV + 348 uV)

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AfterNormalization

RIGHT

P1 amplitude: 1.55 fV


LEFT

P1 amplitude: 1.055 fV


fV = “Frankenvolts”


CorrectedAsymmetryValue

(amplitude P13-N23left – amplitude P13-N23right) Amplitude Asymmetry --------------------------------------------------------------------- X 100 (amplitude P13-N23left + amplitude P13-N23right)

( 1.05 fV – 1.55 fV) Amplitude Asymmetry -------------------------------------------- X 100 = 19% ( 1.05 fV + 1.55 fV)


ClinicalUtilityofAmplitudeNormalizationforDealingwithAsymmetry

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EffectofNormalization

No Amplitude Normalization Amplitude Normalization


McCaslinetal.,2013,JAAA


OcularVEMP

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OcularVEMP(oVEMP)

• RepresentsthesynchronousevokedextraocularmuscleactivityassociatedwiththeVOR.

• Doesnotrepresentmovementsoftheeyes(i.e.theyareshortlatencyresponsese.g.10msec)

•  EOMshavepropertiesthatallowthemtobeactivatedwithprecisionatshortlatenciesforfinemotorcontrolofeyemovements


EffectofAgeonoVEMPAmplitudeandLatencyFromPikeretal.2011

N10 amplitude decreases with age (mean 4.3 +/- 3.4 µV) N10 latency increases with age


oVEMPOriginatesfromtheUtricle

• Placementofelectrodesbeneathanavertedcontralateraleyeplacestheinferiorobliquem.beneathanactiveelectrode.(Curthoys,2010)

Patrick Lynch

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EffectofGazeDirectiononoVEMPMurnaneetal.2011



OVEMPandReferenceContaminationBestmontageisinfraorbital-chinbipolar

Infraorbital - chin

Infraorb – infraorb. -3cm

Infraorb.-3 cm – chin

Piker et al. 2011 Reference contamination occurred 100% of the time and averaged 30%

(range: 18-43%)

Current montage

Recc’d montage, GJ/DM

Reference contamination

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OVEMPandReferenceContamination

Sandhu et al., Clinical Neurophysiology, 2013


OVEMPandReferenceContaminationBestmontageisinnercanthus


oVEMP

cVEMP

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ClinicalUtility


OverlapinPathways

•  Thereisanoverlapinpathwaysforthecaloric,vHITandoVEMPtests

• Primaryoverlapisthesuperiorvestibularnerve

•  Therefore,ifimpairmentaffectsthesuperiorvestibularnerveonly,abnormalitiesshouldoccurforbothcaloricandoVEMPtestsandcVEMPshouldbenormal

•  Ifimpairmentaffectstheinferiorvestibularnerveonly,abnormalitiesshouldoccurforthecVEMPtestonly.


VestibularNeuritis

•  Thesuperiorvestibularnerveismorecommonlyaffected(longer).

•  Theentirenerveisaffectedin50–55%ofpatientswithVN(Magliuloetal.,2014).

• oVEMPabnormalitiesoccurapproximately70%ofthetimeincontrastto40%forthecVEMP(Tayloretal.,2016).

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Manzari et al., Eur Arch Otorhinolaryngol, 2010

DisassociationbetweencVEMPandoVEMPResponses

LeftInferiorvestibularnerveimpairment


VEMPsandRecoveryofFunction

Murofushi et al., Acta Oto-Laryngologica, 2006

•  Studyexamined13patientswithVN

38%demonstratedrecoveryoffunction

•  Therewasrecoveryofthecaloricresponseinonly1patient.


VestibularSchwannoma

•  ForuseindetectingVScVEMPsandoVEMPsshowsimilarratesofasymmetry(Tayloretal.,2015).

• WhilesmallschwannomaswilltypicallyresultinnormalVEMPslargeschwannomasaremorelikelytoaffectbothcVEMPsandoVEMPs

•  TherearereportedcaseswherepatientswithaVSreportingimbalancehaveabnormalVEMPsandnormalhearing.

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Meniere’s Disease vs Migraine


Meniere’sDiseaseandMigraine

•  30–50%ofsubjectswithadiagnosisofMeniere’sDiseasedemonstrateasymmetriccVEMPsandoVEMPsusingair-conductionstimulation.

• Bone-conductioncVEMPsandoVEMPsareoftennormal(Tayloretal.,2011).

• Mayberelatedtotheeffectsendolymphatichydropsonstapesfootplatemotionandchanges(Huangetal.,2011).


VM-MDandVEMPs

Baier et al., Ann N.Y. Acad Sci, 2009

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cVEMPTuningandMeniere’s

Rauch et al., Otology-Neurotology, 2004


Cervical and Ocular VEMPs and Migraine (Tuning)

Taylor et al., Cephalalgia, 2012


VEMPAmplitudeAsymmetryandVM

Taylor et al., Cephalalgia, 2012

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VEMPs and Vestibular Migraine

Zuniga et al., Otolaryngology Head-Neck Surgery, 2012


Disease Duration and oVEMP Amplitude

Pearson r = -0.062, p = 0.472

Pearson r = -0.123, p = 0.102

t(124)=-2.270, p = 0.025


Disease Duration and cVEMP Amplitude

t(136) = -6.308, p = 0.000

Pearson r = -0.130, p = 0.111

Pearson r = -0.106, p = 0.147

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Disease Duration on cVEMP Threshold

t(124)= 1.365, p = 0.175

Pearson r = 0.198*, p = 0.022

Pearson r = 0.222**, p = 0.008


Third Window Disorders (SCD EVA)


ReviewofSSCDPathophysiologyExcitation

•  Sound•  Valsalva(glottisopen)

•  PositivePressure•  Eyesdeviateupandtowardthenose

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ReviewofSSCDPathophysiologyInhibition

•  Valsalva(glottisclosed)•  Eyemovementswillbedownandawayfromnose


cVEMPoroVEMPforSCD?

Janky et al.,Otol Neurotol, 2013


oVEMPandSCD

Zuniga et al.,Otol Neurotol, 2012

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SCD-4000Hz

Manzari et al., Otolaryngol Head Neck Surg., 2013


EnlargedVestibularAqueduct(EVA)

•  Enlargedvestibularaqueductsyndrome(Tayloretal.,2012)isassociatedwithlargeVEMPamplitudesandlowthresholds.

•  TheresponsescanbeextremelyvariableinEVA.VEMPthresholdsmayshowanincrease(decreasedamplitude)ifthereisaprogressiveofotolithimpairment.


EnlargedVestibularAqueduct

Taylor et al., Ear & Hearing, 2012

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EnlargedAqueduct

Taylor et al., Ear & Hearing, 2012


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