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Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_186_библиотеки_им_акад_М_И_Перельмана

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Differenttypes ofnystagm us .Notethatnys tagmus is nam edforthefastphase:ifthefastphas eistotheleftandthes low phasetotheright,werefertoitasleft-beatingnystagmus .
3. TestofSkew.Thisisatestofverticalocularalignment.Coveroneofthepatient’seyeswithyourhandandaskhimorhertofixateon yournose,thenmoveyourhandbackandforth,fromeyetoeye.Asyoudoso,lookforanyverticalmovement—eitherupordown—of theuncoveredeye,asthoughtheeyeistryingtore-focusonyournose.Skewdeviation,orverticalmisalignmentoftheeyes,isthought tobecausedbysupranuclear(higherinthechainofcommandthantheoculomotornuclei;thesepathwaysprojecttothenucleiofCN3, 4,and6,and—unlikeCN3,4,and6—arepartofthecentralnervoussystem[CNS])oculomotordamage.Therefore:
Thepre senc eof any ver ticalm isalignme nt(i.e.,skewdeviation)suggestsce ntraletiology.
Thea bsence ofa ny vertica lmisa lignmentsuggestsperiphe raletiology
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Testingforskew.
Ifanyoneofthesethreeclinicalsignsisconcerningforcentralvertigo,anMRIofthebrainshouldbe doneinordertoexcludeacentralcause.Thatsaid,donotbefalselyreassuredbyanormalHINTS examination.Thefindingsaresubtleand,asyoucanimagine,thetestsaren’talwaystheeasiesttoreliably perform.Therefore,intheabsenceofaconvincingclinicalhistorythatfavorsaperipheraletiology, maintainingalowthresholdtoscan—regardlessoftheHINTSexamination—isimportant.
TheHINTSExamtoDistinguishBetweenPeripheralandCentralVertigo
HeadImpulseTest Nystagmus TestofSkew
Peripheralvertigo Positive(+correctivesaccade) Horizontal,unidirectional,suppressedbyfixation Negative(noskew) Centralvertigo Negative(nocorrectivesaccade) Vertical,multidirectional,notsuppressedbyfixation Positive(+skew)
Box5.2TheVestibulo-OcularReflex(VOR)
ThepurposeoftheVORistostabilizevisionduringheadmovement.Lookinamirrorwhile shakingyourheadside-to-side.Seehowyoureyesmoveoppositeyourhead,allowingyou toremainfixatedonyourimage?That’stheVOR.ThevestibularsystembywayofCN8and thevestibularnucleicomprisestheafferentlimbofthereflex(itdetectsheadmotion),and theoculomotorsystembywayofCN6andCN3comprisestheefferentlimb(itenableseye movementintheoppositedirection).
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Thevestibulo-ocularreflex(VOR).Activationoftherighthorizontalsemicircularcanalfromarapidhead turntotherightresultsinexcitationoftheleftCN6nucleusandrightCN3nucleus(viathemedial longitudinalfasiculus[MLF];seepage232),drivingtheeyestotheleftandtherebystabilizingthegaze.
PeripheralVertigo
Themajorityofpatientswithvertigo(approximately80%)haveperipheralvertigo.Benignparoxysmal positionalvertigo(BPPV),vestibularneuritisandMenierediseasearethreeofthemostcommoncauses.
1. BPPViscausedbydisplacementoftheotoconiawithineithertheleftorrightinnerear.Forwhateverreason(aging,trauma,andinner eardiseaseareallriskfactors, butsometimesit’sjustbadluck),thecrystals getdisplacedfromtheirnormallocationwithintheotolith organs andfloat into the fluid-filledsemicircular canals.This abnormal, asymmetricstimulationresults inthe falsesensationof head rotationwhenevertheheadmoveseventheslightestbitinspecificdirections.
Mostof whaty ouneedto rememberaboutBPPVisinthename.It’sbenign—ittypicallyself-resolvesoverap eriodofdaystoweeks;paroxy smal—itp resents withvery briefepisodesofvertigo;andp ositional—theseepisodesarepredictablyp rovokedby movement.Patientswillreport sudden-onsetseconds-longepisodes ofseverevertigot hatoccurswhenevertheysitup orturntheirheadtoonesideortheother.Associatednauseaandvomitingarecommon.Thediagnosisissuggested
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bytheclinicalhistoryandconfirmedwiththeDix-Hallpikemaneuver(seeBox5.3).Treatmentiswithcanalithrepositioningmaneuvers,suchastheEpley(Box5.3). Pharmacologic therapy is often given to patients with BPPV as well, but it is not curative. However, antihistamines (e.g., mecliz ine), benzodiazepines, and antiemet icscanbeusedforsymptomaticreliefwhileawaitingsuccessfultreatmentwiththeEpleymaneuver.
Unfortunately,despitesubstantialevidencesup p ort ingtheuseoftheEpleymaneuver(onestudycitesan80%curerateat24hours),patientsarefarmorelikely to be p rescribed medication such as meclizineor to undergo expensive and oft en unnecessary neuroimaging t ests. BPPV is “benign” in that it willeventually spontaneouslyresolve,butpatientsaremiserableinthemeantime.Sobeproactiveandtryt heEpley—there’slittleharmandpotentially significantbenefit.
2. Menieredise ase isaheterogeneousconditionofunknowncause1thatpresentswithepisodicinnereardysfunction,characterizedby tinnitus, fluctuatinglow-frequencyhearingloss,andvertigoassociatedwithearfullness. Autoimmunedisease,ageneticpredisposition, and migraine potentially contribute to its pathogenesis. Episodes of vertigo last (by definition) 20 minutes to 12 hours, but hearing impairmentandnauseacanpersistforseveraldays.Thediagnosisis suggestedbyhistoryandconfirmedbyformalhearingevaluation, whichwillshowlow-frequency sensorineuralhearing loss onaudiometry. There isnoproventreatment.Supportivemeasures include avoidance of triggers (alcohol, caffeine, nicotine,andhigh-salt foodsare common triggers) andvestibular rehabilitation. There is no clinicalevidencetosupporttheuseofdiureticsorsteroids.
3. Ves tibularneuritisisthoughttobeaviralorpostviraldiseaseaffectingthevestibularportionofCN8.Classically,vestibularneuritisis characterizedbysevereandpersistentvertigothatisassociatedwithunidirectionalhorizontalnystagmusduetothesuddenasymmetry investibularinput.Nausea,vomiting,andgaitinstabilityarealsocommon.Ifhearingisaffectedaswell,thedisorderiscalledvestibular labyrinthitis. Acute symptoms last for hours to days, oftenwith residual oscillopsia (the sensation that the world is unstable and in motion) andimbalance lastingfor days toweeksor evenlonger. The diagnosis is basedonhistoryandexamination (a positive head impulse test is crucial; the HINTS test was initially developed to distinguish vestibular neuritis from central causes). Treatment is supportive, typicallywith antiemetics and vestibular rehabilitation. In severe cases, there issome evidence that corticosteroids may hastenrecovery.
Box5.3Dix-HallpikeandEpleyManeuvers
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TheDix-Hallpikemaneuver(remember,theDix-Hallpikeisdiagnostic;Dix=Diagnostic!).Toperform thismaneuver,positionthepatientsittinguponanexaminationtable.Turnthehead45°tooneside (you’llneedtodothistwice,oncewiththeheadturnedleftandonceright;typically,onlyonesidewillbe symptomatic),thenquicklylowerthembackwards,sotheheadisextendedabout20°overthebackof thetable.Remembertosupportthepatient’sneckwhenyoudothis.Thenobservethepatient’seyes closely;ifthepatienthasBPPVyoushouldseenystagmusappearwithinabout30seconds.It’snota perfecttest(thesensitivityisabout80%),butifthehistoryseemstofitthediagnosis,apositiveDix­Hallpikemaneuvercanbeveryusefulasconfirmation.Remembertowarnthepatientbeforehand:if theydohaveBPPV,youareeffectivelyprovokinganepisode,andtheywilllikelyfindtheexperience unpleasanttosaytheleast.
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TheEpleymaneuveristhemostwell-establishedtreatmentforBPPV.Putsimply,theideaistoknock thecrystalsbackintotheircorrectposition.TheEpleybeginswiththeDix-Hallpikemaneuver(which willhelpyoudeterminelaterality),followedbyrollingthepatientontotheoppositeshoulderbefore sittingup.Youcanandshouldperformthisonthepatientintheoffice(thepatient’ssymptomsmay entirelyresolve!),but—especiallyforthosewithresidualsymptomsorahistoryofrecurrenceand becausetheEpleyoftentakesseveralattemptstowork—youshouldalsosendthepatienthomewith instructionsonhowtodoitthemselves.Youcanalsoreferthemtoaphysicaltherapistwithexpertise investibulardisorders.
KeyFeaturesofPeripheralVertigo
Duration OtherDistinguishingFeatures Diagnosis Treatment
BPPV Episodic(seconds) Positional Positionaltesting Epley
maneuver
Meniere Episodic(minutes-
hours)
Unilateralhearingloss,tinnitus, earfullness
Audiogram Supportive
Vestibular Neuritis
Persistent(hours­days)
Precededbyaviralinfection, rarelyrecurs
Headimpulsetest(+audiogram,ifhearing changesarepresent)
Supportive
Box5.4OtherCausesofPeripheralVertigo
Herpes zoster oticus (Ramsay Hunt syndrome). This is a less common but important cause of peripheral vertigo. It is the result of reactivation of latent herpes zoster infection within the geniculate ganglion (a collection of sensory neurons of the
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facial nerve). The classic symptom triad includes ipsilateral facial paralysis, ear pain, and vesicles in the auditory canal or auricle, but the virus can spread to the eighth cranial nerve as well, causing vertigo, tinnitus, and/or hearing loss. Treatment is with antiviralmedications,althoughevidencefortheirefficacyissparse.
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VesiclesseeninRamsayHuntsyndrome.(ReprintedfromCampbellWW.DeJong’stheNeurologic Examination.7thed.WoltersKluwer;2012.)
Vestibular schwannoma (acoustic neuroma). Schwann cells myelinate peripheral
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nerves.Itmakessense,then,thatschwannomas—relativelycommon,benign tumors— growalongperipheralnerves.AnycranialnervebesidesCN1andCN2canbeaffected (CN1andCN2aretechnicallypartoftheCNS;theyaremyelinatedbyoligodendrocytes, notSchwanncells);whenCN8isaffected,thetumoriscalledavestibularschwannoma. Because these tumors are slow-growing, the CNS is able to compensate for subtle vestibular imbalances, and severe vertigo is relatively uncommon. More often patients experiencegradual-onsetunilateralhearinglossand tinnitus,alongwitha vaguesense of imbalance or gait instability. When vestibular schwannomas are associated with neurofibromatosis type 2, they are often bilateral (see Chapter 17). An MRI of the internalauditorycanal(IAC)isdiagnostic.
AnMRIshowingavestibularschwannoma(whitearrow)locatedatthecerebellopontineangle,where theeighthcranialnerveentersthebrainstem.(ModifiedfromJohnsonJ.Bailey’sHeadandNeck Surgery.5thed.WoltersKluwer;2013.)
Aminoglycosidetoxicity.Manyaminoglycosideantibioticsareboth vestibulotoxicand
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ototoxicandcantherefore cause peripheral vestibulardamage and permanent hearing loss.
CentralVertigo
Centralvertigoiscausedbylesionswithinthecentralnervoussystem.
Infarction(ischemicorhemorrhagic)andmultiplesclerosisaffectingthebrainstemandcerebellar vestibularpathwaysarecommoncauses,butanylesionslocatedintheseareas(includingtumors, abscesses,etc)cancausecentralvertigo.Becausetherearesomanycellsandaxonspackedintothese areas,vertigoisusuallynotisolatedbutisassociatedwithothersignsandsymptoms.Therefore,when vertigopresentswiththeseso-called“neighborhood”signsandsymptoms—thatis,signsandsymptoms attributabletodamageofnearbyneuronalpathways—redflagsshouldgoupforapotentialcentral etiology.Common“neighborhood”symptomsthatlocalizetothebrainstemincludediplopia,dysarthria, anddysphagia(ifyouadddizziness,you’vegottheclassic“4Ds”ofbrainstemlesions).Ataxia,truncal instability,andlimbincoordinationaremoreindicativeofacerebellarlesion.Thepresenceofanyof theseassociatedsymptoms,whenapatientpresentswithnew-onsetvertigo,isanindicationforanurgent MRItoruleoutacentraletiology.
Migraineisbecomingincreasinglyrecognizedasacauseofvertigo.Migrainewithbrainstemaurais consideredasubclassofmigrainewithaura,definedasmigraineassociatedwithanauraconsistingof classicbrainstemsymptomssuchasvertigo,diplopia,anddysarthria.Vestibularmigraineis characterizedbyfrequentvertiginousepisodeslastingfrom5minutesto72hours,atleasthalfofwhich aretemporallyassociatedwithmigraine.Bothofthesediagnosesremainincompletelyunderstoodbutare worthconsideringinpatientsforwhomyourworkupofothercentralcauseshasbeenunrevealing.
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