DiagnosticCriteriaforPersistentPostural‐PerceptualDizziness(PPPD):

ConsensusdocumentoftheCommitteefortheClassificationofVestibularDisordersofthe

BáránySociety

JeffreyP.Staab,MD,MS

DepartmentsofPsychiatryandPsychologyandOtorhinolaryngology–HeadandNeck

Surgery,MayoClinic,Rochester,MN,USA

AnnegretEckhardt‐Henn,MD

DepartmentofPsychosomaticMedicine,KlinikumStuttgart,Stuttgart,Germany

ArataHorii,MD,PhD

DepartmentofOtorhinolaryngology,NiigataUniversity,Niigata,Japan

RolfJacob,MD

DepartmentofPsychiatry,UniversityofPittsburgh,Pittsburgh,PAUSA

MichaelStrupp,MD

DepartmentofNeurologyandGermanCenterforVertigoandBalanceDisorders,

Ludwig‐MaximiliansUniversity,Munich,Germany

ThomasBrandt,MD

GermanCenterforVertigoandBalanceDisorders,

Ludwig‐MaximiliansUniversity,Munich,Germany

AdolfoBronstein,MD,PhD

Neuro‐OtologyUnit,DivisionofBrainSciences,ImperialCollegeLondon,London,UK

CorrespondingAuthor:

JeffreyP.Staab,MD,MS

DepartmentofPsychiatryandPsychology

MayoClinic

2001stStSW

Rochester,MN55905USA

Office:1.507.284.4159

Fax: 1.507.284.4158

Email:staab.jeffrey@mayo.edu

Keywords:chronicsubjectivedizziness,phobicposturalvertigo,spacemotiondiscomfort,

visuallyinduceddizziness,classification,BáránySociety

Abbreviations:

BPPV–benignparoxysmalpositionalvertigo

CCBS–CommitteefortheClassificationVestibularDisordersoftheBáránySociety

CSD–chronicsubjectivedizziness

fMRI–functionalmagneticresonanceimaging

ICD‐11–InternationalClassificationofDiseases,11thedition(betadraft)

ICVD–InternationalClassificationofVestibularDisorders

MdDS–maldedebarquementsyndrome

PIVC–parieto‐insularvestibularcortex

PPPD–persistentpostural‐perceptualdizziness

PPV–phobicposturalvertigo

SMD–space‐motiondiscomfort

VV–visualvertigo

Abstract

Thispaperpresentsdiagnosticcriteriaforpersistentpostural‐perceptualdizziness(PPPD)

tobeincludedintheInternationalClassificationofVestibularDisorders(ICVD).Theterm

PPPDisnew,butthedisorderisnot.Itsdiagnosticcriteriawerederivedbyexpert

consensusfromanexhaustivereviewof30yearsofresearchonphobicposturalvertigo,

space‐motiondiscomfort,visualvertigo,andchronicsubjectivedizziness.PPPDmanifests

withoneormoresymptomsofdizziness,unsteadiness,ornon‐spinningvertigothatare

presentonmostdaysforthreemonthsormore.Uprightposture,activeorpassive

movement,andexposuretomovingorcomplexvisualstimulimayexacerbatesymptoms.

Precipitatingdisordersincludeconditionscapableoftriggeringvertigo,unsteadiness,or

dizzinessordisruptingbalance,suchasperipheralorcentralvestibulardisorders,other

medicalillnesses,andpsychologicaldistress.PPPDmaybepresentaloneorco‐existwith

otherconditions.Possiblesubtypesawaitidentificationandvalidationinfuture

investigations.ThepathophysiologicprocessesunderlyingPPPDarenotfullyknown.

Emergingresearchsuggeststhatitmayarisefromfunctionalchangesinposturalcontrol

mechanisms,multi‐sensoryinformationprocessing,orcorticalstructureslinkingspatial

orientationandthreatassessment.Thus,PPPDisclassifiedasachronicfunctional

vestibulardisorder.Itisnotastructuralorpsychiatriccondition.

1.Introduction

Thispaperintroducesthediagnosticcriteriaforpersistentpostural‐perceptual

dizziness(PPPD),achronicfunctionalvestibularsyndrome.PPPDisanewterm,butthe

corefeaturesofthedisordercanbefoundinmedicalwritingsdatingbacktothe19th

century[1‐3].Afterabriefreviewofthishistoricalcontext,thecontemporarybackground

ofPPPDispresented,followedbyitsdiagnosticcriteriawithexplanatorynotestoguide

theirapplication.Then,thedifferentialdiagnosisisdiscussedindetail.Lastly,data

suggestingpossiblepathophysiologicmechanismsissummarized.

1.1.Historicalbackground

Inthe1870s,threeGermanphysiciansdescribedsyndromesofdizzinessand

discomfortinmotionrichenvironments,accompaniedbyautonomicarousal,anxiety,and

avoidanceofprovocativecircumstances[1‐3].Benedikt[1]emphasizedaneuro‐

ophthalmologicprocessinPlatzschwindel(vertigoinaplazaorsquare),whereasCordes

[2]focusedonapsychologicalgenesisinPlatzangst(fearinaplazaorsquare)[4].

Westphal[3]proposedthatposturalcontrol,locomotion,consciousappraisalofspatial

orientation,andthreatassessmentwere“partofoneprocess”inDieAgoraphobie(fearof

themarketplace)[5].OtherEuropeanandAmericanphysiciansaddedcommentary[4,6,7],

includingobservationsthatotologicdiseasescouldtriggerWestphal’sagoraphobia,

especiallyinpeoplewithpre‐existinganxiety[6],butdifferingviewsofthesethree

syndromesanddebatesaboutwhethertheywerepredominantlyneurologicorpsychiatric

innaturewereneverresolved.Asotology,neurology,andpsychiatrymaturedinto

separatespecialtiesintheearly20thcentury,PlatzschwindelandPlatzangstfadedfromuse

andagoraphobiabecameapsychiatricdisorder,losingitsspaceandmotioncontext[8,9].

Acenturylatersmallcaseserieswerepublisheddescribingvarioussyndromesofspatial

disorientationandaberrantmotionsensations,includingsupermarketsyndrome[10],

spacephobia,[11,12],motorist’svestibulardisorientationsyndrome[13],visuallyinduced

motionsymptoms[14],andphysiologicheightvertigo[15].

1.2.Contemporarycontext

Sustainedinvestigationsinlargernumbersofpatientsbeganinthe1980s.From

clinicalobservationsintheirtertiaryotoneurologicpractice,BrandtandDieterich[16]

definedPhobischerAttacken‐Schwankschwindel(phobicposturalvertigo,PPV)in1986asa

syndromeofposturaldizzinessandfluctuatingunsteadinessaccompaniedbymildanxiety

anddepressioninpatientswithobsessivecompulsivepersonalitytraits.Otherfeaturesare

listedinTable1.Brandt,Dieterich,andtheircolleagues[17‐19]showedthatPPVwas

common,persistent,anddistinctfromothervestibulardiseasesandpsychiatricdisorders.

Startinginthemid‐1980s,Jacobandcolleaguesconductedaseriesofinvestigations

intopotentiallinksbetweenanxietysymptoms,persistentdizziness,andvestibular

dysfunctioninpatientsfromatertiaryanxietydisordersclinic[20‐22].In1989,they

described[23]andsubsequentlyvalidated[24]space‐motiondiscomfort(SMD)asa

combinationofuneasinessaboutspatialorientationandincreasedawarenessofmotion

stimuli.Activeorpassivemovement(e.g.,walkingdownasupermarketaisle,ridingina

vehicle)andexposuretomovingorpatternedobjectsintheenvironment(e.g.,passing

traffic,stripedcurtains,crowds)increasedsymptomsinaffectedindividuals.

In1995,Bronstein[25]identifiedvisualvertigo(VV)inaportionofpatientsinhis

tertiaryotoneurologicclinic.Thissyndrome,whichfollowedacuteperipheralorcentral

vestibularlosses,manifestedwithsensationsofunsteadinessordizzinessonexposureto

complexormovingvisualstimulithatpersisteddespitepatientsseemingtorecoverfrom

theiracutevestibulardeficits.ThevisualcuesthatexacerbatedVVoverlappedwith

environmentalstimulithatactivatedSMD[26,27].

Finally,in2004,Staabandcolleagues[28]describedchronicsubjectivedizziness

(CSD)basedonobservationsofpatientsintheirtertiarybalancecenter,anddefinedit

moreexplicitlyin2007[29].ThissyndromewassimilarinmanywaystoPPV,butfocused

onphysicalsymptomsofpersistentnonvertiginousdizzinessorunsteadinesswith

heightenedsensitivitytomotionofselforobjectsintheenvironmentanddifficultywith

precisionvisualtasks.Theirdefinitionwashighlysensitive(>85%)andspecific(>90%)

foridentifyingCSDversusMenière’sdisease,vestibularmigraine,orbenignparoxysmal

positionalvertigo(BPPV),inpatientswithorwithoutadditionalcomorbidity[30].

1.3.Currentconsiderationsforclassifyingvestibulardiseasesanddisorders

TheInternationalClassificationofVestibularDisorders(ICVD)dividesdiseasesand

disordersbasedondurationofsymptomsintoacute,episodic,orchronicsyndromes[31].

PPPDmaylastformonthstoyearsmakingitachronicvestibularsyndrome.Vestibular

diseasesanddisordersalsoaredividedintostructural,functional,andpsychiatric

conditionsbasedonprovenorpresumedpathophysiologicmechanisms.Herefunctional

conditionsareconsideredastheywereintheearly19thcenturyasdisorders“arisingfrom

achangeinthemodeofactionofanorgan”[32],unrelatedtostructuralorcellulardeficits.

Asrevivedinthemodernera,mostnotablyingastroenterology[33],thisconceptof

functionalconditionsalsodistinguishesthemfrompsychiatricillnesses.StudiesofPPV,

VV,SMD,andCSDidentifiedanumberoffunctionalalterationsinvestibularandbalance

mechanisms[34‐43]andseparatedtheseconditionsfromprimarypsychiatricdisorders

[16,44].Thesefindings,whicharereviewedbelow,appearlargelyapplicabletoPPPD,

indicatingthatitisafunctional,notstructuralorpsychiatric,vestibulardisorder.

2.Methods

In2006,membersoftheBáránySocietycreatedaworkinggrouptostandardize

nomenclatureforvestibulardiseasesanddisordersworldwide.Thisledtoformationof

theCommitteeforClassificationVestibularDisordersoftheBáránySociety(CCBS)to

overseedevelopmentofthefirstInternationalClassificationofVestibularDisorders(ICVD)

[31].Todate,thisprocesshasgeneratedconsensusdocumentsdefiningvestibular

symptoms[45],vestibularmigraine[46],BPPV[47],andMenière’sdisease[48].

Additionaldefinitionsareintheoffing.In2010,theCCBScharteredaBehavioral

Subcommitteetoidentifyprimaryandsecondarypsychiatricdisordersthatcauseor

amplifyvestibularmorbidityandreviewevidenceaboutthenatureofPPV,SMD,VV,and

CSD.Inkeepingwithestablishedproceduresfortheclassificationprocess[49],the

BehavioralSubcommitteeincludedanotologist(A.H.),neurologist(M.S.),andmembers

withspecialexpertiseinpsychosomaticmedicine(J.P.S.,A.E.H.)andpsychiatry(J.P.S.,R.J.).

Membershailedfromthreecontinents(Asia,Europe,andNorthAmerica).Twosenior

neuro‐otologists(T.B.,A.B.)graciouslyagreedtoadvisesubcommitteemembersontheir

deliberations.

ThesubcommitteemetforthefirsttimeinAugust2010duringtheBáránySociety’s

biennialcongressinReykjavík,Iceland.From2010‐2012,thechair(J.P.S.)consultedwith

subcommitteemembersindividually.ThesedeliberationsproducedaconsensusthatPPV,

SMD,VV,andCSDincludedacoresetofphysicalsymptomsthatrepresentedadistinctly

definablevestibulardisorder.Subcommitteememberspreparedadraftdefinitionofthis

disorderthatwasupdatediterativelyafterreviewbythegeneralmembershipofthe

BáránySocietyinJune2012inUppsala,Sweden,theCCBSinNovember2013inMondorf‐

les‐Bains,Luxembourg,andthenagainbythegeneralmembershipinMay2014inBuenos

Aires,Argentina.Thedisorderwasnamedpersistentpostural‐perceptualdizzinessto

reflectitsmaindiagnosticcriteriaofpersistentnon‐vertiginousdizziness,unsteadiness,and

non‐spinningvertigothatareexacerbatedbyposturalchallengesandperceptualsensitivity

tospace‐motionstimuli.Aseparate,100‐wordnarrativedefinitionwaspreparedforthe

WorldHealthOrganizationaspartoftheBáránySociety’srecommendationsforupdatesto

thevestibulardisorderssectionoftheforthcoming11theditionoftheInternational

ClassificationofDiseases(ICD‐11)[50].

3.CriteriaforthediagnosisofPersistentPostural‐PerceptualDizziness(PPPD)

CriteriaA‐EmustbesatisfiedtomakeadiagnosisofPPPD.

A. Oneormoresymptomsofdizziness,unsteadiness,ornon‐spinningvertigoarepresent

onmostdaysfor3monthsormore.1‐3

1. Symptomsarepersistent,butwaxandwane.

2. Symptomstendtoincreaseasthedayprogresses,butmaynotbeactivethroughout

theentireday.

3. Momentaryflaresmayoccurspontaneouslyorwithsuddenmovements.

B. Symptomsarepresentwithoutspecificprovocation,butareexacerbatedby:

1. Uprightposture,

2. Activeorpassivemotionwithoutregardtodirectionorposition,and

3. Exposuretomovingvisualstimuliorcomplexvisualpatterns,

althoughthesethreefactorsmaynotbeequallyprovocative.4

C. Thedisorderusuallybeginsshortlyafteraneventthatcausesacutevestibular

symptomsorproblemswithbalance,thoughlesscommonly,itdevelopsslowly.5

1. Precipitatingeventsincludeacute,episodic,orchronicvestibularsyndromes,other

neurologicormedicalillnesses,andpsychologicaldistress.

a) Whentriggeredbyanacuteorepisodicprecipitant,symptomstypicallysettle

intothepatternofcriterionAastheprecipitantresolves,butmayoccur

intermittentlyatfirst,andthenconsolidateintoapersistentcourse.

b) Whentriggeredbyachronicprecipitant,symptomsmaydevelopslowlyand

worsengradually.

D. Symptomscausesignificantdistressorfunctionalimpairment.

E. Symptomsarenotbetterattributedtoanotherdiseaseordisorder.6

Notes

(1) TheprimarysymptomsofPPPDincludenon‐motionsensationsofdisturbedor

impairedspatialorientation(dizziness),feelingsofbeingunstablewhilestandingor

walking(unsteadiness),andfalseordistortedsensationsofswaying,rocking,

bobbing,orbouncingofoneself(internalnon‐spinningvertigo)orthesurroundings

(externalnon‐spinningvertigo)[45].

(2) Symptomsmustbepresentformorethan15ofevery30days.Mostaffected

individualsexperiencesymptomseverydayornearlyeveryday.

(3) Symptomsneednotbecontinuous,butmustbepresentforprolonged(hours‐long)

periodsthroughouttheday.Momentarysymptomsalonedonotfulfillthiscriterion.

(4) AllthreeprovocativefactorsofcriterionBmustbediscernableintheclinicalhistory,

butdonothavetobeequallytroublesome.

a. Uprightposturemeansstandingorwalking.

b. Activemotionreferstoaperson’sself‐generatedmovements.Passivemotion

referstoapersonbeingmovedbyconveyancesorotherindividuals(e.g.,ridingin

avehicleorelevator/lift,beingjostledinacrowd).

c. Visualstimulimayencompasslargeorsmallportionsofthevisualfield.Fullfield

stimuli(e.g.,passingtraffic,roomsfilledwithbusydécor,graphicsdisplayedon

largescreens)arethemostprovocative,butsmallerstimuli(e.g.,books,

computers,mobileelectronicdevices)maybetroublesomewhentheyarethe

focusofsustainedvisualattention.

(5) Themostcommonprecipitatingeventsareperipheralorcentralvestibularconditions

(25‐30%ofcases),attacksofvestibularmigraine(15‐20%),panicattacksor

generalizedanxietythatmanifestprominentdizziness(15%each),concussionor

whiplashinjuries(10‐15%),andautonomicdisorders(7%).Othereventsthatare

capableofproducingvertigo,unsteadinessordizziness,oralteringbalancefunction

(e.g.,cardiacdysrhythmias,adversedrugreactions)triggerthedisorderless

commonly(collectively~3%)[29,30].ThemajorityofconditionsthattriggerPPPD

areacuteorepisodicinnature.Patientsreporttheonsetofchronicsymptomsof

PPPDfollowingtheiracuteillnesses.However,precipitantssuchasgeneralized

anxietydisorder,autonomicdisorders,andperipheralorcentraldegenerative

conditionsmaydevelopinsidiously.Inthesecases,patientsarelesslikelytoreporta

distinctonset.Whenaspecificprecipitantcannotbeidentified,particularlywhen

symptomsslowlyworsen,re‐evaluationofthediagnosisisindicatedandaperiodof

prospectivemonitoringmaybeneededtoconfirmit.

(6) PPPDmayco‐existwithotherdiseasesordisorders.Evidenceofanotheractive

illnessdoesnotnecessarilyexcludeadiagnosisofPPPD.Rather,clinicaljudgment

mustbeexercisedtodeterminethebestattributionofthepatient’svestibular

symptomstoallidentifiedillnesses[44,51].

4.Comments

4.1.Furtherdescriptionsofdiagnosticcriteria

ThediagnosticcriteriaofPPPDareexplainedingreaterdetailbelow,basedon

informationderivedfromnumerousreportsonPPV,SMD,VV,andCSD.Table1liststhe

diagnosticcriteriaofPPPDandthecharacteristicsofPPD,SMD,VV,andCSDthatinformed

thedefinition.Citationsgiveninthesubsectionsbelowrelatetothefourprecursors.

4.1.1.Corevestibularsymptoms

TheprimarysymptomsofPPPDaredizziness,unsteadiness,andcertaintypesof

non‐spinningvertigo[16,44].ThedizzinessofPPPDisanon‐motionsymptom[45]that

patientsmaydescribevariouslyascloudiness,fuzziness,fullness,heaviness,orlightnessin

thehead,orafeelingthattheirspatialorientationisnotsharporvisualfocusisnotclear.

Unsteadinessisasensationofinstabilityorwobblingwhenupright,orafeelingofveering

fromsidetosidewhenwalkingwithoutadirectionalpreponderance[45].Non‐spinning

vertigoencompassesfeelingsofswaying,rocking,bouncing,orbobbingthatpatientsmay

describeasmotioninsidetheirheads,involvingtheirentireheadsorbodies,oroccurring

intheenvironment.TiltingandslidingsensationsareincludedintheBáránySociety’s

definitionofnon‐spinningvertigo[45],butthesearenottypicalsymptomsofPPPD

[17,44,51].Intermittent,momentarysensationsofillusorymovementthatlastnomore

thanafewseconds(CriterionA.3.)mayincludebothspinningandnon‐spinningvertigo

[16,17].

4.1.2.Temporalpatternofsymptoms

PPVwasdefinedbyfluctuatingposturalsymptomsandmomentaryillusionsof

movement[16,17].SMDwasdescribedasasituationalphenomenon,occurringduring

exposurestoprovocativestimuli[22,23].TheearliestreportsofVV[25]alsofocusedon

situationalsymptoms,thoughrecentinvestigationsidentifiedalinkbetweenpersistentVV

andchronicdizziness[41].DefinitionsofCSD[29,44]emphasizedchronicsymptoms

lastingthroughoutthedayandexacerbatedbymotionstimuli.Onestudyfoundthat

symptomsofCSDwereabsentormildestforaboutanhourafterpatientsawokeinthe

morning,butthenincreasedasthedayprogressed[52].Theseobservationsidentifiedtwo

temporalpatternsincorporatedintoPPPD(Table1).Mostpatientsexperiencea

backgroundofvestibularsymptomsthroughouttheday,nearlyeveryday[17,44].

Symptom‐freeintervalstendtobebrief(minutestohours),thoughadistinctminorityof

patientsmayexperiencesymptom‐freeperiodslastingfordaystoweeks.Symptomswax

andwanespontaneously,butareaggravatedbythethreeprovocativefactorsofCriterion

B.Whenfreeofthesecircumstances,patients’symptomsmaybeinnocuous,limitedto

non‐motiondizzinesswithminimalunsteadinessornon‐spinningvertigo.However,all

symptomsaresusceptibletoprovocationwithuprightposture,motion,andexposureto

complexvisualstimuli.Withtheseprovocativesituations,unsteadinessandnon‐spinning

vertigotendtodominatetheclinicalpicture.

4.1.3.Provocativefactors

TheprovocativefactorsincludedinCriterionBweredescribedinallormostofthe

precursorsofPPPD(Table1).Uprightposture,activeorpassivemovement,andexposure

tovisuallycomplexormovingstimuliaggravatethecoresymptomsofPPPD.Thereareno

datatoidentifyoneofthesefactorsasbeingmoreprovocativethantheothersorto

determinethesensitivitiesandspecificitiesofdemandingthepresenceofone,two,orall

threefactorstomakeadiagnosisofPPPD.Therefore,CriterionBrequiresthataffected

individualswillreportatleastsomedifficultywithallthreefactors,whilerecognizingthat

patientswillnotbeequallysensitivetoallofthem,andthatthemostprovocativefactor

willvaryamongpatientswithPPPD.

Symptomsmaynotincreaseimmediatelyonstanding,moving,orenteringvisually

stimulatingenvironments,butbuildthroughoutcontinuedexposuretothesesituations.

Symptomsusuallydonotreturntobaselineimmediatelyoncessationofprovocations,but

maylastforhoursthereafter.Thispatterndiffersfromthatexperiencedbypatientswith

structuraldeficitswhosesymptomsincreaseanddecreaseinclosetemporalrelationshipto

motionexposures.PatientswithPPPDmayexpressconcernsabouthavingtoendurean

increaseintheirnoxioussymptomsintheseprovocativesituations,butthisdiffersfrom

individualswithanxietydisorderswhotendtofocusmoreonfearsofbecoming

incapacitated,injuringthemselvesorothers,orattractingunwantedattention.

4.1.3.1.Uprightposture

MostpatientswithPPPDreportmoreseveresymptomswhenstandingorwalking

thanwhensittingorlyingdown[16,17,44].Individualswhoareparticularlysensitiveto

posturalchangesalsomayexperienceincreasedsymptomswhensittinguprightwithout

backorarmsupport.Patientsmaynothaveacompleteresolutionofsymptomswhenlying

down,butrecumbentposturesaretheleasttroublesome.Patientsmayminimizethe

adverseeffectsofuprightposturebytouchingfixedobjects,usinggaitaids,orholdingonto

otherpeople.Patientsdonothavetoholdtightlytosupporttheirweight.Rather,alight

touchissufficienttoobtainthestabilizingeffectofsomatosensoryinput.

4.1.3.2.Activeorpassivemovement

Provocativemovementsmayoccurinanydirectionorposition.Mostpatientsfind

thatactiveandpassivemotionsaretroublesomeindirectproportiontotheirintensity.

Speed,duration,andrepetitionofmovementappeartobemoreimportantthanwhether

motionisactivelyorpassivelyinduced.Highvelocitymovementsthatareprolongedor

repeatedareuniversallyprovocativewhetherencounteredactivelyorpassively.

Responsestolessintensemovementsvaryamongaffectedindividuals.Mostpatientsfeel

bestwhenstill,butothersreportthatmovingatamodestpace(e.g.,walkingorridinga

bicycle)ismoretolerablethanremainingstationarywhenupright[51].

4.1.3.3.Visualstimuli

Challengingvisualstimulimaybemovingorstationary.Environmentsthatcontain

fullfieldvisualflow(e.g.,passingtraffic,millingcrowds),largecomplexpatterns(e.g.,busy

carpeting,largestoredisplays),orwide‐openspaceswithdistantorindistinctvisuospatial

referencepoints(e.g.,largefields,warehouses,atria)aremosttroublesome[22‐27,44].

Exposuretofullfieldvisualstimulimayexacerbatesymptomsforhours,evenafterbrief

exposures.Smallervisualtargetsaregenerallylesstroublesomeunlesssustainedattention

tothemisrequired.Performingtasksthatrequirecontinuousvisualfocus(e.g.,readinga

book,usingacomputer,orwatchingtelevision)mayexacerbatesymptomsevenwhen

patientsaresittingstill[29,44].Theincreasingneedinthemodernworldtoview

informationonelectronicscreensisabaneformanypatientswithPPPD.

4.1.4.Clinicalcourse

Inmostcases,PPPDdevelopsastheacutesymptomsofprecipitatingeventsremit

[51].Patientsdonotexperiencesymptom‐freeintervals.Instead,astheiracute

vertiginoussymptomsfade,theydevelopthecharacteristicchronicsymptomsofPPPD.In

othercases,PPPDhasastutteringonset.PatientsmayexperiencePPPD‐likesymptoms

lastingdaystoweeks,untilrecurrencessettleintoapersistentcourse.Thisstuttering

courseismorelikelywhenprecipitantsareshort‐lived,recurrentevents(e.g.,attacksof

BPPV,migraine,orpanic).Leastoften,PPPDhasagradualonset.Precipitantssuchas

generalizedanxiety,autonomicdisorders,anddegenerativediseasesoftheperipheral

vestibularapparatusorcerebellumarechronicconditionsthatmaydevelopslowly.With

thesetriggers,symptomsofPPPDmayappeargraduallyandworsenslowly.

SpecificprecipitantsofPPPDcannotbeidentifiedinallpatients,especiallythose

whohavebeensymptomaticformanyyearsandlackadequatedocumentationoftheir

initialclinicalpresentations.Eveninthesesituations,however,mostpatientsdescribean

acute,subacute,orstutteringonsetofillness.Patientswithclinicalhistoriesofgradually

worseningchronicvestibularsymptomsorbalanceproblemsthathavenoidentifiable

startingpoints,particularlythosewithoutgeneralizedanxietyorautonomicproblems,are

lesslikelytohavePPPDthanthosewithmoredefinitiveonsetsofillness.Theywarrant

prospectiveobservationoveraperiodofseveralmonthstoverifythediagnosticpicture

andproperlyscreenforotherdiseases,especiallyslowlyemergingdegenerativedisorders.

4.2.PossiblevariantsorsubtypesofPPPD

CommonalitiesamongPPV,SMD,VV,CSD,andthesyndromesthatpredatedthem

formedthebasisofthediagnosticcriteriaforPPPD.However,semiologicsimilarities,even

thosestretchingovermorethanacentury,donotnecessarilymeanthatPPPDisasingle

entity.Thecurrentstateofscientificknowledgelefttwoimportantquestionsunanswered:

(1)IsPPPDasingledisorderwithoneprincipalpathophysiologicprocessorisitthe

commonmanifestationofmultipleconditionsthatproducesimilarsymptomsfrom

differentpathophysiologicmechanisms?(2)IfPPPDisasingledisorder,doesithave

clinicallymeaningfulandvalidlydistinguishablesubtypes?

4.2.1.Asingledisorderoragroupofrelatedconditions?

TheprecipitatingfactorsofPPV[16],SMD[23],VV[25],andCSD[29]spanavariety

ofneuro‐otologic,othermedical,andpsychologicalevents.Itisnotknowniftheseact

throughonepathophysiologicprocesstoproduceasinglesyndromeorviaseparate

mechanismsthatshareenoughofafinalcommonpathwaytogeneratesymptomsand

susceptibilitiesthatcloselyresembleoneanother.Theformersituationwouldbeakinto

posttraumaticstressdisorderinwhichawidevarietyoftraumaticexperiencesproduce

onesyndromewithfourclustersofsymptomsthatcanbeprovokedbyinternaland

externalfactors[8].Thelattercircumstancewouldbelikehypertensioninwhich

chronicallyelevatedbloodpressurecanarisefrommultiplediseasesthatproduce

sustainedincreasesinintravascularpressureviadifferentphysiologicmechanisms.

4.2.2.Dosubtypesexist?

AlthoughPPV,SMD,VV,andCSDshareanumberoffeatures,theyalsohavedifferent

areasofemphasis(Table1).PosturalprovocationisadistinguishingfeatureofPPV

[16,17].ItwasnotpartoftheoriginaldescriptionofCSD[29],butwasaddedlater[45].

Difficultywithself‐motionispartofPPV[16,17],SMD[23],andCSD[29,44].Troublewith

visualmotionstimuliistheprimaryfeatureofVV[25‐27]andisemphasizedinSMD[22‐

24]andCSD[29,44].Thus,PPV,SMD,VV,andCSDmayreflectdifferentperspectivesona

single,multifacetedclinicalentityortheymayofferinsightsintopotentiallydistinguishable

subtypesofPPPD(e.g.,posturallypredominantsubtype,visuallypredominantsubtype).

Mildanxietyanddepressivesymptomsandphobicbehaviorswereincludedinthe

descriptionsofPPV[16,17],butwereconsideredcomorbiditiesofCSD[44,51,53].This

raisesthepossibilitythatPPVmaybeeitheradistinctphobicsubtypeofPPPDor

encompassPPPDplusaspecificphobiaofdizziness‐relatedexperiences.

Intheabsenceofdefinitivescientificdataonthesepossiblesubtypes,theBehavioral

SubcommitteechosetodefineonlyPPPDfortheICVD,butallowforclinicalvariabilityas

reflectedinCriterionB.TheWorldHealthOrganizationpermitsrelatedtermstobelisted

intheICD‐11.Therefore,PPV,SMD,VV,andCSDwereretainedasindextermsforcross‐

referencingintheICD‐11betadraftdefinitionofPPPD[50].

4.2.3.Probable(subthreshold)PPPD

Membersofthesubcommitteeconcludedthattherewerenotenoughpublisheddata

todefineaclinicallymeaningfulprobableorsubthresholdversionofPPPD.Clinical

experiencewithPPVandCSDsuggestscautioninapplyingthediagnosisofPPPDto

patientswhodonotfulfillallofitsdiagnosticcriteria.

4.3.MakingadiagnosisofPPPD

ThediagnosisofPPPDismadebygatheringclinicalhistoryrelevanttoCriteriaA‐D.

Datafromphysicalexaminationsandclinicallyindicateddiagnostictestinghelpto

determineifPPPDisthebestdiagnosis,eitheraloneorincombinationwithotherdiseases

ordisorders(CriterionE).PPPDisnotadiagnosisofexclusion[17,44,51].Itshouldnotbe

giventopatientswhoreportonlynon‐specificchronicvestibularsymptomsorthosewho

haveenigmaticcomplaintsthatdonotfulfillitsdefinition.Insuchcases,prospective

monitoringmayprovidetheclinicalevidenceneededtoverifyorexcludethediagnosis.

4.4.Differentialdiagnosis

ThedifferentialdiagnosisofPPPDincludeschronicsequelaeofacuteprecipitants,

recurrentattacksofepisodicprecipitants,ongoingmanifestationsofchronicprecipitants,

otherchronicvestibularsyndromes,medicalorpsychiatricdisordersthatproduce

persistentunsteadinessordizziness,andadverseeffectsofregularlyconsumed

prescriptionornon‐prescriptionmedications[16,25,29,51].

4.4.1.Chronicsequelaeofacuteprecipitants

SomeprecipitantsofPPPDareacutedisordersthathavethepotentialforchronic

symptomaticcomplications(e.g.,vestibularneuritisorstrokeleadingtopersistent

uncompensatedvestibulopathies).Forthesedisorders,thediagnosticquestioniswhether

patients’presentingsymptomsareduetoPPPDalone,chronicmanifestationsofits

precipitants,orboth[51].Thisdiagnosticdilemmaisresolvedbycarefulattentiontothe

clinicalhistoryandassessmentofpatients’compensationstatus.Ahistoryofpersistent

non‐vertiginousdizzinessandunsteadinessprovokedbyuprightposture,patients’own

movements,andexposuretovisualmotionstimuliplusphysicalexamandlaboratory

evidenceofgoodcompensation(e.g.,nospontaneousnystagmusorabnormalresponsesto

headthrust,headshake,orsteppingtests)indicatesthatPPPDistheonlyactivediagnosis.

Incontrast,thepresenceofongoingepisodesofheadmotion‐provokedvertigoor

unsteadinessandexamfindingsofincompletecompensationwithoutpersistentdizziness

arguesagainstPPPD.Athirdpossibilityisthecombinationofpersistentdizzinessand

motionsensitivityplusheadmotion‐provokedsymptomsandexamfindingsofincomplete

compensation,whichwouldindicatecoexistingPPPDanduncompensatedvestibulopathy.

4.4.2.Recurrentattacksofepisodicprecipitants

PPPDmaybetriggeredbyepisodicvestibulardisorderssuchasvestibularmigraine

[46],BPPV[47],andMenière’sdisease[48]thatcausedistinctboutsofvestibular

symptomsincontrasttothepersistent,waxingandwaningdizziness,unsteadinessand

non‐spinningvertigothatarehallmarksofPPPD.WhenPPPDco‐existswiththese

disorders,properdiagnosisrestonidentifyingthecharacteristicsymptomsofeachactive

disorder.Episodicdisordersadddistinctivevestibularsymptomstothebackgroundof

PPPD[54],suchacuteattacksofvertigopluscephalalgia,photophobiaandphonophobia,

withorwithoutvisualauraforvestibularmigraine[46],short‐livedpositionalvertigofor

BPPV[47],orattacksofvertigo,tinnitus,andfluctuatinghearingforMenière’sdisease[48].

4.4.3.Ongoingmanifestationsofchronicprecipitants

SomeprecipitantsofPPPDarechronicconditionsthemselves(e.g.,chronicanxiety

anddepressivedisorders,post‐concussivesyndrome,autonomicdisorders,andheart

diseases).Theymaycausepersistentunsteadinessordizzinesswithorwithouttriggering

PPPD.Whenpresentalone,theyarenotasgreatlyaffectedbythemotionprovocationsof

CriterionBasisPPPD.Thestrategyfordifferentialdiagnosisinthesecasesistodetermine

ifCriteriaA‐DforPPPDarepresentandevaluatekeyelementsofclinicalhistories,physical

examinations,andlaboratorytestingtodeterminewhichconditionsexplainthepatients’

symptomsbest(i.e.,PPPDalone,precipitatingeventsalone,orboth)(CriterionE).

4.4.3.1.Chronicanxietyanddepressivedisorders

Chronicanxietyduetogeneralizedanxietydisorder,agoraphobia,socialphobia,

obsessivecompulsivedisorders,andtraumaticstressdisordersmaymanifestwith

persistentdizziness[8,9].Depressivedisordersalsomaycausedizziness[55].These

disordersarediagnosedaccordingtothelatestversionsoftheInternationalClassification

ofDiseases[9]orDiagnosticandStatisticalManualofMentalDisorders[8].However,in

neurologic,otologic,andprimarycaresettingswherepatientswithvestibularsymptoms

aremostcommonlyencountered,simpleself‐reportquestionnairesofferavalidand

efficientmeansofdetectingpsychiatricmorbidity.The7‐itemGeneralizedAnxiety

DisordersScale(GAD‐7)maybeusedtoscreenforpathologicalanxiety[56].The9‐item

PatientHealthQuestionnaire(PHQ‐9)maybeusedtoscreenfordepression[57].The14‐

itemHospitalAnxietyandDepressionScale(HADS)coversbothanxietyanddepressive

symptoms[58].Positiveresultsindicatethatananxietyordepressivedisorderislikely,

eitherasthecauseofvestibularsymptomsorco‐existingwithPPPD[17,29,44,53].

Ahistoryoftroublinglifecircumstancesorrecentstressfuleventscannotbeused

asevidencefororagainstthepresenceoffunctionalorpsychiatricdiagnoses,including

PPPD[51].Arecentstudyfoundthatchildhoodandadulthoodadversitywereequally

prevalentinpatientswithstructuralversusfunctionalorpsychiatriccausesofvestibular

symptoms[59].Furthermore,panicattacksandgeneralizedanxietydisorderfrequently

occurintheabsenceofidentifiablestressors[8,9].Therefore,adiagnosisofPPPDrestson

fulfillmentofitsdiagnosticcriteria,regardlessofpatients’historiesofadversity.

4.4.3.2.Postconcussivesyndrome

Patientswithpostconcussivesyndromefollowingatraumaticbraininjuryor

whiplashoftenexperiencechronicdizzinessinadditiontoheadache,insomnia,cognitive

symptoms,andmoodlability[60].PatientswhofulfillallofthediagnosticcriteriaforPPPD

afteratraumaticbraininjuryorwhiplashshouldreceivethediagnosis.Thepresenceor

absenceofothersequelaeofinjurywilldetermineifadditionaldiagnosesarewarranted.

Ontheotherhand,patientswhocomplainofchronicdizzinessafterheadinjuryshouldnot

begivenadiagnosisofPPPDiftheydonotmanifestCriteriaA‐D.

4.4.3.3.Autonomicdisorders

Autonomicdisordersfrequentlycausedizziness.Theautonomicdisordersmostlike

totriggerPPPD,basedonresearchfromCSD[61],aretype1neurocardiogenic(vasovagal)

syncopeandposturalorthostatictachycardiasyndrome,whicharemostoftenencountered

inadolescentsandyoungadults.Orthostaticintolerancewithorwithouthypotensionfrom

neurologicandcardiovascularillnesses(e.g.,autonomicneuropathy)ismorecommonin

olderadults,inwhomitmaybepartofmulti‐factorialdizziness.Patientswithautonomic

disorderstendtohavemorepronouncedorthostaticandexertionaldizzinessthanthose

withPPPD[61].However,symptomsoverlapconsiderably,sothedifferentialdiagnosis

dependsonexaminationofautonomicintegrity.PPPDdoesnotcauseabnormalchangesin

heartrateorbloodpressure.Autonomicdisordersdonotcreatedifficultieswithcomplex

ormovingvisualstimuliinpatientswhoaresittingstill.Thus,vitalsignsduringautonomic

challengesandsensitivitytovisualstimuliwhenseatedatrestbestdistinguishPPPDfrom

autonomicdisorders,recognizingthepotentialforthetwoproblemstoco‐exist.

4.4.4.Otherchronicvestibularsyndromes

ChronicvestibularsyndromesinthedifferentialdiagnosisofPPPDincludebilateral

peripheralvestibulopathy[62],neurodegenerativedisorders(e.g.,downbeatnystagmus

syndrome,cerebellardiseases)[63,64],andmaldedebarquementsyndrome(MdDS)[65].

4.4.4.1.Bilateralperipheralvestibulopathy

BilateralperipheralvestibulopathyisbestdistinguishedfromPPPDbyits

characteristicfindingsonphysicalexaminationandlaboratorytesting[62],suchas

bilaterallypositiveheadthrustsanddiminishedresponsestocaloricstimulation.Clinical

historymayofferadditionalclues,butthesearenotasdefinitive.Forexample,PPPDdoes

notcauseoscillopsia,butoscillopsiaispresentinonly30‐40%ofpatientswithbilateral

peripheralvestibulopathy.Individualswithbilateralvestibulopathytypicallyhaveless

troublewithcomplexvisualstimuliwhensittingstillthanpatientswithPPPD,butthis

symptomvariesamongpatientswithbothdisorders.

4.4.4.2.Chronicneurologicdisorders

NeurodegenerativedisordersthataffectpostureandgaitsuchasParkinson’s

disease,cerebellardegeneration[64],anddownbeatnystagmussyndrome[63]may

manifestwithdizzinessorunsteadinesswhenstandingorwalkingbeforemotorsignscan

bedetectedonphysicalexamination.Thegradualonsetofthesecomplaintsintherelative

absenceofdifficultieswithcomplexormovingvisualstimulishouldarousesuspicionthat

PPPDisnotthecorrectdiagnosis.Thebestapproachinthissituationisaperiodof

prospectivemonitoring(typically6‐12months)withasymptomlogkeptbythepatient

andserialexaminationsperformedbytheclinicianbeforemakingadefinitivediagnosis.

Bilateralperipheralneuropathyofthefeetandorthostatictremor[66‐68]may

causeorcontributetodizzinessandunsteadinesswhenpatientsareupright,though

neitheronecausestroublewithcomplexormovingvisualstimuli.Peripheralneuropathy

ismuchmorelikelytomanifestwithsensorylossandpain,orpresentasonepartofa

multi‐factorialpicture,thantobethesolecauseofdizziness.Orthostatictremoris

diagnosedbyidentifyingitscharacteristic13‐18Hztremorinthelowerlegson

electromyographicorposturographictesting[66‐68].

4.4.4.3.Maldedebarquementsyndrome

Maldedebarquementsyndrome(MdDS)[65]isaconditionofpersistent

unsteadinesstriggeredbytravelingonboats,aircraft,orautomobiles,usuallyforatleasta

fewhours.Symptomscharacteristicallydecreaseduringpassivemotion(e.g.,ridingina

car)andthenincreaseagainwhenmotionceases.Thatisoppositethepatternfoundin

mostpatientswithPPPD,thoughaminorityofindividualswithPPPDexperience

temporarydecreasesinsymptomsduringmodestmotion,suchaswalkingatamedium

paceorridingabicycleonasmoothpath.A“spontaneousonset”versionofMdDShasbeen

described,thoughmostpatientsinthosereportshadmigraineoranxietydisorders[65],

whichareknownprecipitantsofPPPD.AmajordifferencebetweenMdDSandPPPDisthe

effectoftreatment.MdDSimprovesverylittlewithmedicationsorvestibularhabituation,

whereastreatmentstudiesofPPV[69],VV[70,71],CSD[28],andPPPD,itself[72],showed

significantimprovementswithserotonergicantidepressantsorvestibularhabituation.

4.4.5.Adverseeffectsofmedications

Prescriptionmedications,overthecounterpreparations,anddietarysupplements

maycausedizziness,unsteadiness,andvertigo.Vestibularsymptomscausedbynewly

administeredmedicationsorchangeddosesofexistingmedicationsmaytriggerPPPD.

4.4.6.Otherfunctionalformsofvestibularsymptoms

Cliniciansmayencounterpatientswhodescribepersistentvestibularsymptoms

thatdonotfitthediagnosticcriteriaofeitherPPPDorotherwell‐definedchronic

vestibularsyndromes[51].Examplesincludeconstant,invariantvertigo,unsteadiness,or

dizziness,complexbodymotionsinmultipledirectionssimultaneously,andkaleidoscopic

swirlingmovementsoflargeportionsofthevisualfield.Patientsoftenreportalack

provokingormitigatingfactors.Theseclinicalpresentationshavenotbeenstudied

systematically,buttheircontinuousnature,unwaveringintensity,andabnormal

complexitydistinguishthemfromtheepisodicorfluctuatingsymptomsreportedby

patientswithstructuraldeficits,PPPD,andanxietyordepressivedisordersthatcause

vestibularsymptoms[51].Inmanypatients,thesefunctionalformsofvestibular

symptomsareaccompaniedbyotherchronicphysicalcomplaintssuchasfatigueandpain,

raisingthepossibilitythattheyarebutonemanifestationofabroadersomaticsymptom

[8]orbodilydistressdisorder[73].

4.4.7.Gaitdisorders,falls,andnearfalls

PatientswithPPPDmayreportsensationsofveeringfromside‐to‐sidewhen

walking.Onexam,theymayexhibitamildlysloworcautiousgait.Onestudyofwalking

mechanicsfoundthatpatientswithPPVwalkedslower,hadreducedstridelength,and

spentagreaterfractionoftimewithbothfeetonthegroundthanhealthysubjects[39].

Thesechangescorrelatedwithreducedbalanceconfidence.Acasestudydistinguishedgait

andposturesymptomsofCSDfromthoseoffunctionalgaitdisorders[74].Fallsandnear

fallshaveneverbeenapartofPPVorCSD[51].Therefore,clinicalevidenceofsignificant

changesingaitorrecurrentfallsornearfallsindicatesthepresenceofastructuralor

functionalgaitdisorder.PPPDmayco‐existwiththesedisorders.

4.5.Epidemiology

NoepidemiologicstudiesareavailableforPPPD,butitsprevalenceandincidence

maybeestimatedfromresearchdoneonpatientswithPPV,VV,CSD,andchronicdizziness

followingacutevestibularsyndromes[17,29,41,75‐77].

4.5.1.EstimatesoftheprevalenceofPPPD

ClinicalepidemiologicdatafromtertiarycarecenterswithspecialinterestinPPV

[16]andCSD[29]showedtheirprevalencetobe15‐20%amongallpatientspresentingfor

evaluationofvestibularsymptoms,makingthemthemostcommondiagnosesamong

youngadultsandthesecondmostcommonamongalladults,trailingonlyBPPV.The

averagedurationofillnessatthetimeoftertiaryconsultationwas4.5yearswithsome

patientsexperiencingsymptomsfordecades[16,29].Disabilityvariedwidelyfrom

individualswhohadfewlimitationsindailyfunctioningtothosewhowereseverely

impairedandunabletowork.Theaverageageofpatientspresentingforevaluationof

PPPDisthemid‐40s,witharangefromadolescencetolateadulthood[29,78,79].Afemale

predominancehasbeenreportedinthefirstclinicalreportsonPPPD[78,79].

4.5.2.EstimatesoftheincidenceofPPPD

TheincidenceofPPPDfollowingneuro‐otologictriggersmaybeestimatedfrom

studiesthatfollowedpatientsprospectivelyafterboutsofacuteorepisodicvestibular

disorders(e.g.,vestibularneuritis,BPPV,vestibularmigraine,Menière’sdisease)[75‐77].

TheseinvestigationsfoundPPPD‐likechronicdizziness[75‐77]orpersistentVV[41]in

about25%ofpatientsafter3‐12monthsoffollow‐up,despiteotherwiseadequate

compensationorrecoveryfromtheinitialillnesses.TheseresultsindicatethatPPPDis

likelytodevelopinasignificantproportionofpatientsafflictedwithacuteorepisodic

vestibularsyndromes.Similarprospectivestudiesofclinicaloutcomesfollowingother

medicalandpsychologicalprecipitantsofPPPDhavenotbeenconducted.However,

retrospectiveinvestigationsfoundthatthecourse[53]andtreatmentresponse[80]of

patientswithCSDtriggeredbyanxietydisordersmirroredthatofpatientswithCSD

triggeredbyacutevestibularsyndromes,suggestingthattheclinicalcourseofPPPDmay

besimilarregardlessofprecipitant.Along‐termfollow‐upstudyofpatientswithPPV

foundthatonlyaminorityexperiencedspontaneousresolutionofsymptoms[19].Most

hadachronicwaxingandwaningcourseandthree‐quartersdevelopedanxietyor

depressivecomorbidity.Thus,themajorityofpatientswithPPPDarelikelytoremain

symptomaticwithouttreatment,regardlessofinitialprecipitant.

TheincidenceandprevalenceofPPPDinprimarycarepracticesandthegeneral

populationarenotknownasdetailedepidemiologicstudiesofPPV,SMD,VV,andCSDhave

notbeenconductedinthosesettings.

4.6.PossiblepathophysiologicprocessesunderlyingPPPD

InvestigatorsstudyingPPV,CSD,SMD,andVVhaveidentifiedpathophysiologic

processesthatmaybeapplicabletoPPPD,includinganxiety‐relatedpersonalitytraitsasa

possibleriskfactor[79,81,82]andhighlevelsofanxietyandvigilanceaboutacute

symptomsduringtriggeringeventsasinitialpathologicresponses[41,75‐77].Alterations

inposturalcontrolstrategies[34‐40],shiftsinmulti‐sensoryintegration[41],andreduced

corticalintegrationofspatialorientationinformationwiththreatassessmentsmaybe

sustainingmechanisms[42,43].Allofthesewillhavetobestudiedingreaterdetailin

patientsmeetingthespecificdiagnosticcriteriaforPPPD.

4.6.1.Possibleriskfactors

BrandtandDieterichdescribedobsessivecompulsivepersonalitytraitsintheir

originalpatientcohortwithPPV[16].Subsequentstudiesfoundthatindividualswiththe

anxiety‐relatedpersonalitytraitsofneuroticismandintroversion[81]hadanincreased

riskforCSD.HighneuroticismalsowasidentifiedinareportonPPPD[79].Incontrast,

personsdemonstratingresilience,optimism,andbeliefsthatlifeismeaningfuland

manageablehadareducedriskofpersistentdizzinessafteracutevestibularevents[82].

Patientswithfamilyorpersonalhistoriesofanxietydisorderspre‐datingtheonsetof

vestibularsymptomshadanincreasedriskofdevelopingpersistentdizziness[77]orCSD

[53]aftertriggeringevents.Inpatientswithanxietydisorders,ahistoryofprevious

vestibulardeficitswasassociatedwithSMD[22,23].Thesestudiessuggestthatanxiety‐

relatedpersonalitytraitsorapersonalorfamilyhistoryofanxietydisordersmayberisk

factorsfordevelopingPPPDfollowingrelevantprecipitants.

4.6.2.Initialpathologicreactions

Threeprospectivestudiesfoundthathighanxietyaboutdizzinessduringandafter

boutsofacutevestibularneuritisorBPPVpredictedcontinueddizzinessthree[75]and

twelve[76]monthslater.Theseinitialpsychologicalresponseshadfargreatereffectson

long‐termoutcomesthantheinitialorsubsequentstatesofpatients’peripheralvestibular

functioningorvestibulo‐ocularreflexes.Furthermore,patientswithemergingsymptoms

ofCSDwhoweretreatedwiththreesessionsofcognitivebehavioraltherapystartedwithin

8weeksofprecipitatingeventshadmarkedreductionsindizzinessandavoidanceof

provocativecircumstances[83],benefitsthatenduredatfollow‐upsixmonthslater[84].

Collectively,thesedataraisethepossibilitythatahighlyanxiousresponsetotriggering

eventsmaybethepivotalinitialpathophysiologicprocessinthedevelopmentofPPPD,and

thatearlysymptom‐specificinterventionsmightcounterthiseffect.

4.6.3.Possiblealterationsinposturalcontrol

SeveralinvestigationsshowedthatpatientswithPPVmanifestedanalterationin

posturalcontrolcharacterizedbyhighfrequency,lowamplitudeposturalswayrelatedto

co‐contractionoflowerlegmuscleswhenstandingatrest[34,38].Onestudyofpatients

withCSDdemonstratedsimilarresults[40].Normalpeopleusedthishighdemand

posturalcontrolstrategyinchallengingbalancesituationssuchasstandingatheights[85‐

87].PatientswithPPVadoptedthisstrategyduringlessdemandingtasksthannormal

individuals[35‐37],possiblyrelatedtoalowerthresholdforengagingclosedloopfeedback

mechanismstoadjustposture[38].Brandtetal.[88]reportedthecaseofapatientwho

wasfollowedprospectivelyfromaboutofacutevestibularneuritistothedevelopmentof

PPV.Thetransitiontochronicsymptomscoincidedwithemergenceofthehighfrequency,

lowamplitudeswaypatternofPPV.Futurestudieswillhavetomeasuretheprevalenceof

thisposturalcontrolstrategyamongpatientswithPPPDanddetermineitsassociationwith

clinicalcharacteristicsofthedisorder,particularlyposturalsymptoms.

4.6.4.Possibleassociationwithvisualdependence

Bronsteinandcolleagues[25‐27]showedthatpeoplewithVVmanifestvisual

dependence,atrait‐liketendencytorelyonvisualinformationforspatialorientation.Ina

prospectivestudy,Cousinsetal.,[41]foundthatpatientswhohadpersistentdizzinessfor

atleastsixmonthsfollowingboutsofacutevestibularneuritishadgreatervisual

dependencethanthosewhorecoveredwithoutchronicsymptoms.Futurestudieswill

havetomeasuretheprevalenceandseverityofvisualdependenceinpatientswithPPPD

anddetermineitsassociationwithclinicalfeaturesofthedisorder,particularlyvisual

symptoms.

4.6.5.Possiblechangesinactivityandconnectivityofcrucialbrainregions

ThefirstneuroimagingstudiesofpatientswithCSD[42]andPPPD[43]were

completedrecently.Thefirststudy[42]measuredtheactivityandconnectivityof

vestibular,visual,andanxiety‐relatedregionsofthebrainusingfunctionalmagnetic

resonanceimaging(fMRI)inresponsetosound‐evokedvestibularstimulationinpatients

withCSDversusnormalcontrolsubjectsmatchedforanxiety‐relatedpersonalitytraits.

PatientswithCSDshowedreducedstimulus‐relatedactivityintheparieto‐insular

vestibularcortex(PIVC),anteriorinsula,inferiorfrontalgyrus,hippocampus,andanterior

cingulatecortexcomparedtonormalindividuals.Theyalsohadmorenegative

connectivitybetweenthePIVCandtheanteriorinsula,anteriorcingulatecortex,and

hippocampus,aswellasbetweentheanteriorinsulaandmiddleoccipitalcortex.The

secondstudy[43]comparedwomenwithPPPDtowomenwhohadrecoveredwithout

sequelaefromillnessesthatcausedacutevestibularsymptoms.UsingfMRI,theauthors

foundthatwomenwithPPPDhadlessactivationoftheamygdalaandanteriorcingulate

cortexandgreateractivationoftheleftangulargyrusinresponsetothenon‐motion

stimulusofstandardizedpicturesdesignedtoelicitnegativeemotions.Theseearlyresults

suggestthatbrainareasresponsibleforhighlevelspatialorientation,multi‐sensory

integration,andthreatassessmentmaynotbeasactiveorwellconnectedinpatientswith

PPPDasinnormalpeople,potentiallyleavinglowerlevelpostureandgazecontrol

mechanismspoorlyintegratedwithoneanother.Thesefindingsawaitconfirmationin

largerstudieswithsufficientpowertocontrolforpotentialconfoundsandmeasure

associationswithclinicalaspectsofPPPD.

5.Additionalcommentary

Theconsensusprocessfordecision‐makingseeksaresultthathasbroadsupport.

Itdoesnotrequireunanimity,butdemandsmorethanasimplemajority[89].Werethe

lattersufficientfordevelopingdiagnosticcriteriaorwritingtreatmentguidelines,then

informativeaspectsoftheminorityopinioncouldbelosttopracticingclinicians,the

scientificcommunity,andgeneralpublic.Thoughnotallagree[90],argumentsfor

publishingminorityopinionsinsuchendeavorshavebeenmade[91].

MembersoftheBehavioralSubcommitteeandtheiradvisorsreachedconsensus

aboutthediagnosticcriteriaforPPPDanditsrelationshiptoSMD,VV,andCSD,butnot

PPV.SMDandVVwereseenascomplexsymptoms,notstandalonediagnosticentities.

TheyinformedcriterionBofPPPD,butareknowntooccurinothersituations[23,25].The

definitionofPPPDparalleledworkinotherareasofmedicinewherefunctionaldisorders

(e.g.,thefunctionalgastrointestinaldisorders[33,92]andfibromyalgia[93,94])were

definedbytheircorephysicalsymptoms,andnotassociatedpsychologicalfeatures.CSD

wasastepinthatdirectionbasedinpartonthephysicalfeaturesofPPV[29].However,

thedefinitionofPPPDisbettersupported;hence,PPPDnowfullysupplantsCSD.

Membersofthesubcommitteeandtheiradvisorscarefullyconsideredaproposal

toincludePPVasasubtypeofPPPD.Argumentsinfavorofthisideafocusedonthe

richnessofthedefinitionofPPV,whichincludespersonalityfactorsandpsychological

symptomsthatwereshowntoaffectclinicalpresentation[17,39],aswellas30yearsof

researchthatdescribeditsclinicalcourse[17‐21]andidentifiedpotentialpathophysiologic

mechanisms[35‐39].Argumentsagainsttheideaincludedconcernsthatthemixof

physicalandpsychologicalsymptomsandpersonalitytraitsthatconstitutePPVisdifficult

tooperationalizeinclinicalpractice[44]andmayhavetobeupdatedbasedonnewer

research[81,82],andthatincludingPPVasasubtypeofPPPDwithoutvalidatingtheir

relationshipcouldperplexcliniciansandinvestigators.Intheend,asimplemajorityof

subcommitteemembersvotedagainstincludingPPVasasubtypeofPPPD.

ThedebateaboutPPVhighlightedthefactthatPPPDisadynamicconditionas

illustratedinFigure1.Itisafunctionaldisorder,althoughstructuralandpsychological

factorsaffectitsdevelopment.ClinicianswhoapplyCriteriaAandBassimplechecklistsof

symptomswithoutcapturingthedynamicfeaturesoftheirpatients’histories(CriterionC)

assumeareductionistviewofthediagnosis,potentiallymissingimportantaspectsof

patients’morbidity(CriterionD)andnuancesofthedifferentialdiagnosis(CriterionE).

ScientistswhofailtoconsiderthedynamicsofPPPDriskmuddlingratherthanilluminating

thenatureofthedisorderanditspathophysiologicmechanisms.

ACKNOWLEDGEMENTS

ThisworkwassupportedbytravellinggrantsfromtheBáránySocietyandNeuro+Berlin,a

nonprofitassociationsupportingneurologicalresearch.MembersoftheBehavioral

Subcommitteegratefullyacknowledgethesupport,advice,andrecommendationsoffered

bynumerouscolleaguesthroughoutthisendeavor.

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Table1.FeaturesofPPV,SMD,VV,andCSDthatinformedthedefinitionofPPPD PPV[16] SMD [23] VV[25] CSD [29]

PrimarySymptoms(criteriaA.1‐3)

Dizziness [27,41]

Unsteadiness

Non‐spinningvertigo

Temporalprofile(CriteriaA.1‐3)

Fluctuatingwithmomentaryflares

Situational(provoked)

Situational(provoked),

Persistent[41]

Persistentwithdiurnalvariability

[53]

Provocativefactors(CriteriaB.1‐3)

Uprightposture [45]

Activeorpassivemotion

Movingvisualstimuliorcomplexpatterns

Precipitants(CriterionC.1)

Vestibularsyndromes

Othermedicalillnesses

Psychologicaldistress

Courseofillness(CriteriaC.1.a‐b)

Long‐standing,

waxing/waning[18]Maybelong‐standing

Maybelong‐standing

Chronic

Physicalexamandlaboratoryfindings(CriterionE)

NormalSomatosensorydependenceon

posturography[22]

Centralorperipheral

vestibulardeficits

Abnormalitiesrelatedtocomorbidconditions[45]

FeaturesnotincorporatedintoPPPD

Anxiety PartofPPVAssociated with

SMD[22]AssociatedwithprolongedVV[41]

MaybecomorbidwithCSD[30]

Depression PartofPPV MaybecomorbidwithCSD[30]

PersonalitytraitsObsessive‐compulsivetraitsarepartofPPV

Neurotic,introvertedtraitsmayberiskfactors

forCSD[80]

FigureLegend

Figure1.PutativemechanismsofPPPD.

PPPDisthoughttodevelopviaadynamicprocess(arrow).Inabout70%ofpatients,a

structuralvestibularsyndrome(e.g.,vestibularneuritis,BPPV)orothermedicalcondition

precipitatesPPPD(blackdot,a)[26].Individualswhorespondtothetriggeringeventwith

ahighlevelofanxietyandbodyvigilanceappearlikelytoprogresstoPPPD(i.e.,totraverse

thearrowfromtheinitialstructuraleventthroughthistransientpsychologicalstagetothe

chronicfunctionaldisorder)[39,73,74].Anxiety‐relatedpersonalitytraitsorpre‐existing

anxietydisordersappeartoincreasetheriskofdevelopingPPPD[51,67,75].Inabout30%

ofpatients,PPPDbeginswithacutepsychologicaldistress(blackdot,b)andthen

progressestothefunctionaldisorder[26].PPPDmayco‐existwithstructuralor

psychologicalillnesses[42],placingpatientsintheintersectionsofthefunctionaland

psychologicalorstructuralellipses.Anxiety‐relatedpersonalitytraitsandpsychological

symptoms(checkmarks,)areincorporatedintoPPV[15,16],whereastheyare

consideredpredisposingfactorsandcomorbidsymptoms,respectively,inPPPD.

PPPD=Persistentpostural‐perceptualdizziness

PPV=Phobicposturalvertigo