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10/10/19
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©2017 MFMER | slide-1
ContemporaryConceptsinVestibular-EvokedMyogenicPotentials
DevinL.McCaslin,Ph.D.DepartmentofOtorhinolaryngologyIowa-Speech-Language-HearingAssociationOctober17th2019
©2017 MFMER | slide-2
MayoIntegratedNeuro-VestibularTeam(MINT)
• Otolaryngology/Audiology• Neurology• BehavioralMedicine
• PhysicalTherapy• Audiology
©2017 MFMER | slide-3
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)
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ReincarnationoftheSonomotorResponse-VEMPHalmagyiandCurthoys,1990’s
• VEMPcanberecordedfrommusclegroupsthatreacttosound:SCM,trapezius,tricep,gastrocnemiusandquadracepsmusclesetc.etc.(e.g.Ferber-Viartetal.1998;RudisillandHain,2008)
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Vestibular-evokedMyogenicPotentials
• Sternocleidomastoid(SCM)m.
• Trapeziusm.
• Gastrocnemiusm.
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VEMPisaSonomotor“Reflex”Whatisareflexpathway?
• Consistsof:• Areceptor(endorgan)• Anafferentpathway• Centralconnections• Anefferentpathway,and,• Endmuscles
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OtolithOrgans
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KeyConcept!
• Weareusingsoundonlyasapressurestimulusi.e.soundpressureisbeingusedasahydro-mechanicalforcetomovetheendolymphaticfluidand,asaconsequence,totranslateotolithstocreatetransduction.
• Alowfrequencytendstoprovideagreaterpush
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ReceptorforcVEMPistheSaccule?Hamagyi&Curthoys(2000)
• Sacculeisvestibularendorganmostsensitivetosound
• Liesunderthestapesfootplate
• Neuronsfromsaccularmacularespondtotiltsandclickstimuli
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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
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oVEMP Pathway
• oVEMPpathway• Utricle• Sup.Vestib.Nerve• Med.Vestib.Nuc.• MedialLongitudinalFasciculus
• MotorNucleusofContraCNIII
• CNIII• ContraInferiorObliquem.
Utricle
Sup VN
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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
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oVEMPNormalResponse
• Inresponseto500Hztoneburst
• N1:~10msec• P1:~15msec
• Contralateralresponseoccursslightlyearlierandislargerthanipsilateralresponse(contralateralpathwayisfaster)
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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)
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B-81 – Bone-conduction VEMPs
Latency (ms)
Am
plitu
de (1
0 µV
/div
)
Air conduction
Bone conduction
oVEMPs
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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
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KeycVEMPConcepts
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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
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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
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TheGestaltoftheIdeaThecommonproblem
• YourecordaleftearVEMPanditis3xlargerthantherightearVEMP.
• HowdoyouknowwhethertheamplitudedifferenceisduetopathologyorbecausetheEMGfromwhichtheVEMPwasextractedwas3xlargerontheleftsidecomparedtotherightside?
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GestaltoftheIdeaTheCommonProblem
• SohowaboutifweobtainavaluethatrepresentstheaveragesizeoftheEMGontheleftsideduringsignalaveragingoftheVEMP.Samefortherightside.
• ThenwedivideintoeachdatapointintheleftVEMPtracingthemeanEMGvalueanddothesameontherightside.Inthiswaywecannormalizethetraces.
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ControllerView
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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
©2017 MFMER | slide-32
WaveformsPriortoNormalization
RIGHT
P1 amplitude: 348 uV
Ave. RMS EMG: 201 uV
LEFT
P1 amplitude: 120 uV
Ave. RMS EMG: 105 uV
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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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©2017 MFMER | slide-34
AfterNormalization
RIGHT
P1 amplitude: 1.55 fV
Ave. RMS EMG: 201 uV
LEFT
P1 amplitude: 1.055 fV
Ave. RMS EMG: 105 uV
fV = “Frankenvolts”
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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)
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ClinicalUtilityofAmplitudeNormalizationforDealingwithAsymmetry
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EffectofNormalization
No Amplitude Normalization Amplitude Normalization
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McCaslinetal.,2013,JAAA
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OcularVEMP
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OcularVEMP(oVEMP)
• RepresentsthesynchronousevokedextraocularmuscleactivityassociatedwiththeVOR.
• Doesnotrepresentmovementsoftheeyes(i.e.theyareshortlatencyresponsese.g.10msec)
• EOMshavepropertiesthatallowthemtobeactivatedwithprecisionatshortlatenciesforfinemotorcontrolofeyemovements
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EffectofAgeonoVEMPAmplitudeandLatencyFromPikeretal.2011
N10 amplitude decreases with age (mean 4.3 +/- 3.4 µV) N10 latency increases with age
©2017 MFMER | slide-42
oVEMPOriginatesfromtheUtricle
• Placementofelectrodesbeneathanavertedcontralateraleyeplacestheinferiorobliquem.beneathanactiveelectrode.(Curthoys,2010)
Patrick Lynch
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EffectofGazeDirectiononoVEMPMurnaneetal.2011
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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
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OVEMPandReferenceContaminationBestmontageisinnercanthus
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oVEMP
cVEMP
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ClinicalUtility
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OverlapinPathways
• Thereisanoverlapinpathwaysforthecaloric,vHITandoVEMPtests
• Primaryoverlapisthesuperiorvestibularnerve
• Therefore,ifimpairmentaffectsthesuperiorvestibularnerveonly,abnormalitiesshouldoccurforbothcaloricandoVEMPtestsandcVEMPshouldbenormal
• Ifimpairmentaffectstheinferiorvestibularnerveonly,abnormalitiesshouldoccurforthecVEMPtestonly.
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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
©2017 MFMER | slide-53
VEMPsandRecoveryofFunction
Murofushi et al., Acta Oto-Laryngologica, 2006
• Studyexamined13patientswithVN
38%demonstratedrecoveryoffunction
• Therewasrecoveryofthecaloricresponseinonly1patient.
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VestibularSchwannoma
• ForuseindetectingVScVEMPsandoVEMPsshowsimilarratesofasymmetry(Tayloretal.,2015).
• WhilesmallschwannomaswilltypicallyresultinnormalVEMPslargeschwannomasaremorelikelytoaffectbothcVEMPsandoVEMPs
• TherearereportedcaseswherepatientswithaVSreportingimbalancehaveabnormalVEMPsandnormalhearing.
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Meniere’s Disease vs Migraine
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Meniere’sDiseaseandMigraine
• 30–50%ofsubjectswithadiagnosisofMeniere’sDiseasedemonstrateasymmetriccVEMPsandoVEMPsusingair-conductionstimulation.
• Bone-conductioncVEMPsandoVEMPsareoftennormal(Tayloretal.,2011).
• Mayberelatedtotheeffectsendolymphatichydropsonstapesfootplatemotionandchanges(Huangetal.,2011).
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VM-MDandVEMPs
Baier et al., Ann N.Y. Acad Sci, 2009
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cVEMPTuningandMeniere’s
Rauch et al., Otology-Neurotology, 2004
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Cervical and Ocular VEMPs and Migraine (Tuning)
Taylor et al., Cephalalgia, 2012
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VEMPAmplitudeAsymmetryandVM
Taylor et al., Cephalalgia, 2012
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VEMPs and Vestibular Migraine
Zuniga et al., Otolaryngology Head-Neck Surgery, 2012
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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
©2017 MFMER | slide-63
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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©2017 MFMER | slide-64
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
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Third Window Disorders (SCD EVA)
©2017 MFMER | slide-66
ReviewofSSCDPathophysiologyExcitation
• Sound• Valsalva(glottisopen)
• PositivePressure• Eyesdeviateupandtowardthenose
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ReviewofSSCDPathophysiologyInhibition
• Valsalva(glottisclosed)• Eyemovementswillbedownandawayfromnose
©2017 MFMER | slide-68
cVEMPoroVEMPforSCD?
Janky et al.,Otol Neurotol, 2013
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oVEMPandSCD
Zuniga et al.,Otol Neurotol, 2012
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SCD-4000Hz
Manzari et al., Otolaryngol Head Neck Surg., 2013
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EnlargedVestibularAqueduct(EVA)
• Enlargedvestibularaqueductsyndrome(Tayloretal.,2012)isassociatedwithlargeVEMPamplitudesandlowthresholds.
• TheresponsescanbeextremelyvariableinEVA.VEMPthresholdsmayshowanincrease(decreasedamplitude)ifthereisaprogressiveofotolithimpairment.
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EnlargedVestibularAqueduct
Taylor et al., Ear & Hearing, 2012
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EnlargedAqueduct
Taylor et al., Ear & Hearing, 2012
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Questions