NYSTAGMUSNYSTAGMUS

••NystagmusNystagmus isis characterizedcharacterized byby rythmicrythmic oscillationsoscillations of the of the eyeseyes in in whichwhich eacheach phasephase isis of of equalequal amplitudeamplitude. .

••NystagmoidNystagmoid or or saccadicsaccadic intrusionsintrusions: : oscillatoryoscillatory, , butbut notnot rythmicrythmic. .

••PendularPendular nystagmusnystagmus: : movementsmovements withwith equalequal speedspeed in in bothbothdirectionsdirections..

••JerkJerk nystagmusnystagmus: slow : slow deviationdeviation on one side (slow on one side (slow phasephase) ) followedfollowed byby a a rapidrapid movementmovement in the in the oppositeopposite direction (direction (rapidrapidphasephase).).

ImportantImportant featuresfeatures toto considerconsider whenwhendescribingdescribing a a nystagmusnystagmus: :

1)1) direction direction (in the (in the jerkjerk nystagmusnystagmus itit isis thatthat of the of the

rapidrapid phasephase), ), 2) Plane of oscillation 2) Plane of oscillation (horizontal, vertical, rotational), (horizontal, vertical, rotational), 3) amplitude3) amplitude (fine, medium, (fine, medium, largelarge) ) 4) 4) frequencyfrequency ((lowlow, high)., high).

PHYSIOLOGICPHYSIOLOGIC

1) End 1) End pointpoint nystagmusnystagmus2) 2) OpticokineticOpticokinetic nystagmusnystagmus

3) 3) VestibularVestibular nystagmusnystagmus

CONGENITALCONGENITAL

1)1) Congenital nystagmusCongenital nystagmus2)2) Latent nystagmusLatent nystagmus3)3) Spasmus mutansSpasmus mutans

ACQUIREDACQUIRED1) 1) Peripheral vestibular nystagmusPeripheral vestibular nystagmus

2) 2) Central vestibular nystagmusCentral vestibular nystagmus3) 3) GazeGaze--evoked nystagmusevoked nystagmus

4) 4) Periodic anternating nystagmusPeriodic anternating nystagmus5) 5) Rebound nystagmusRebound nystagmus6) 6) Pendular nystagmusPendular nystagmus7) 7) SeeSee--saw nystagmussaw nystagmus8) Sensitive 8) Sensitive nystagmusnystagmus

9) 9) Convergence retraction nystagmusConvergence retraction nystagmus10) 10) Dissociated nystagmusDissociated nystagmus

1) End 1) End pointpoint nystagmusnystagmus

2) 2) OpticokineticOpticokinetic nystagmusnystagmus

3) 3) VestibularVestibular nystagmusnystagmus

PHYSIOLOGIC PHYSIOLOGIC NYSTAGMUSNYSTAGMUS

PHYSIOLOGIC NYSTAGMUSPHYSIOLOGIC NYSTAGMUS1) 1) EndEnd--pointpoint nystagmusnystagmus

••JerkJerk nystagmusnystagmus commonlycommonly foundfound in in extremeextreme positionspositions of of gazegaze, , withwith rapidrapid phasephase in the direction of in the direction of gazegaze; ;

ItIt maymay presentpresent: : ••after prolongued (>10after prolongued (>10--15 sec) deviations of the eye in extreme 15 sec) deviations of the eye in extreme positionspositions••immediately in immediately in extremeextreme positionspositions, , butbut transitorytransitory, , endingending after a after a few few secondsseconds, , ••permanentlypermanently in in extremeextreme positionspositions butbut maymay regressregress ifif the the gazegazereturnsreturns 1515--2020°° towardstowards the the primaryprimary position. position. ••AnomaliesAnomalies of of ocularocular motilitymotility are are notnot presentpresent in in anyany of the of the threethreeformsforms. .

2) 2) OpticokineticOpticokinetic nystagmusnystagmus

••JerkJerk nystagmusnystagmus causedcaused byby the the repetitiverepetitive movementmovement of of anan imageimage in the visual in the visual fieldfield. .

••The slow The slow phasephase isis a a pursuitpursuit in in whichwhich the the eyeeye followsfollows the the objectobject whilewhile the the rapidrapid phasephase isis a a saccadesaccade whichwhich bringsbringsthe the eyeeye in the in the primaryprimary position in position in orderorder toto fixatefixate the the subsequentsubsequent objectobject. .

••The The opticokineticopticokinetic nystagmusnystagmus isis usefuluseful toto demonstratedemonstratethe non the non organicorganic nature of a visual nature of a visual defectdefect..

3) 3) VestibularVestibular nystagmusnystagmus••Due to the movement of Due to the movement of endolymphendolymph towardstowards the the ampullaampulla of one of one side, side, inducedinduced byby bothboth passive passive movementsmovements of the body or head, and of the body or head, and the the irrigationirrigation of the of the earear withwith warmwarm water, water,

••ThisThis causescauses a slow a slow movementmovement of the of the eyeseyes toto the the oppositeopposite side (the side (the vestibulevestibule projectsprojects towardstowards the the contralateralcontralateral horizontalehorizontale gazegaze centerscenters) ) followedfollowed byby a a rapidrapid compensatingcompensating phasephase in the in the oppositeopposite direction. direction.

••The The nystagmusnystagmus ““beatsbeats”” towardstowards the the stimulatedstimulated side (in the direction side (in the direction of head of head movementsmovements or or towardstowards the the earear irrigatedirrigated withwith warmwarm water). water).

••ColdCold water water irrigationirrigation causescauses, , insteadinstead, the , the oppositeopposite phenomenonphenomenon, , withwith inhibitioninhibition of the of the utricleutricle and a and a nystagmusnystagmus whichwhich ““beatsbeats”” towardstowardsthe the oppositeopposite direction. direction.

Caloric testingCaloric testing

1)1)CongenitalCongenital nystagmusnystagmus2) 2) LatentLatent nystagmusnystagmus3) 3) SpasmusSpasmus mutansmutans

CONGENITAL CONGENITAL NYSTAGMUSNYSTAGMUS

CONGENITAL NYSTAGMUSCONGENITAL NYSTAGMUS1) 1) CongenitalCongenital nystagmusnystagmus

••Present at birth or, more frequently, in the first Present at birth or, more frequently, in the first months of life.months of life.

••Binocular, of similar Binocular, of similar amplitureampliture in in bothboth eyeseyes, , ititmaymay bebe pendularpendular or or jerkyjerky in the in the primaryprimary position, position, whilewhile in the in the laterallateral position position itit isis generallygenerally jerkyjerky. .

ItIt isis characterizedcharacterized byby: : ••the the movementmovement occursoccurs in a single in a single planeplane, , generallygenerally the the horizontalhorizontalplaneplane, and , and remainsremains the the samesame in in allall gazegaze positionspositions; ; ••the the oscillationoscillation isis independentindependent fromfrom the position of the head, the position of the head, increasesincreases withwith fixationfixation and and isis reducedreduced byby the the convergenceconvergence or or closingclosing of the of the eyeseyes..••itit isis oftenoften identifiableidentifiable in a in a particularparticular position of the position of the eyeseyes, , knownknownasas the the ««cancellationcancellation positionposition»», in , in whichwhich itit isis inhibitedinhibited or or changeschangesitsits direction.direction.••An anomalous position of the head is often present to allow theAn anomalous position of the head is often present to allow thecancellationcancellation area area toto coincide with the primary position of coincide with the primary position of gazegaze..••Another characteristic is the inverison of the opticokinetic Another characteristic is the inverison of the opticokinetic nystagmus (the nystagmus occurs to the opposite side with respecnystagmus (the nystagmus occurs to the opposite side with respect t toto normalnormal conditionsconditions).).

2) 2) LatentLatent nystagmusnystagmus••LatentLatent nistagmusnistagmus isis a a typetype of of jerkjerk nystagmusnystagmus onlyonly presentpresent in in monocularmonocular vision: vision: whenwhen anan eyeeye isis closedclosed, a , a binocularbinocular and and conjugatedconjugated oscillationoscillation occursoccurs, , withwith rapidrapid phasephase directeddirected towardstowardsthe the viewingviewing side. side.

••thisthis nystagmusnystagmus isis alwaysalways associatedassociated toto strabismusstrabismus ((generallygenerallyesotropiaesotropia) and ) and amblyopiaamblyopia isis frequentlyfrequently presentpresent. .

••LatentLatent nystagmusnystagmus followsfollows AlexanderAlexander’’s s rulerule, , thatthat isis itit increasesincreases in in amplitudeamplitude whenwhen the the gazegaze isis in the direction of the in the direction of the rapidrapid phasephase..

••The The originorigin of of thisthis nystagmusnystagmus isis unknownunknown and and therapytherapy mustmust bebedirecteddirected towardstowards the the preventionprevention of of amblyopiaamblyopia. .

3) 3) SpasmusSpasmus mutansmutans••This syndrome is This syndrome is characterizedcharacterized byby the the associationassociation of of nystagmusnystagmus, , oscillationsoscillations and and anomalousanomalous positionspositions of the of the head (head (stiffstiff neckneck). ).

••ItIt generallygenerally presentspresents in the first in the first yearyear of life, and of life, and spontaneouslyspontaneously regressesregresses 11--2 2 yearsyears after after onsetonset. .

••The The nystagmusnystagmus isis irregularirregular, , oftenoften horizontalhorizontal, , withwith high high frequencyfrequency and and reducedreduced amplitudeamplitude. . ••The The amplitudeamplitude isis typicallytypically differentdifferent in the in the twotwo eyeseyes and and monocularmonocular formsforms are are alsoalso presentpresent. .

••AcquiredAcquired spasmusspasmus mutansmutans maymay bebe anan earlyearlysignsign of of tumorstumors of the visual of the visual pathwayspathways, in , in

particularparticular of the of the opticoptic chiasmchiasm, or , or brainstembrainstem..

••The The diagnosisdiagnosis mustmust thereforetherefore bebe of of exclusionexclusion, and , and neuroradiologicneuroradiologic examinationsexaminations

are are necessarynecessary (CT and/or MRI)(CT and/or MRI) in the in the presencepresence of of anyany signssigns of of alterationsalterations of the of the

opticoptic nervenerve or or chiasmaticchiasmatic functionfunction

Acquired nystagmus

1) 1) PeripheralPeripheral vestibularvestibular nystagmusnystagmus

2) 2) CentralCentral vestibularvestibular nystagmusnystagmus

3) 3) GazeGaze--evokedevoked nystagmusnystagmus

4) Periodic anternating 4) Periodic anternating nystagmusnystagmus

5) 5) ReboundRebound nystagmusnystagmus

6) 6) PendularPendular nystagmusnystagmus

7) 7) SeeSee--sawsaw nystagmusnystagmus

8) Sensitive 8) Sensitive nystagmusnystagmus

9) 9) ConvergenceConvergence retractionretraction nystagmusnystagmus

10) 10) DissociatedDissociated nystagmusnystagmus

1) 1) PeripheralPeripheral vestibularvestibular nystagmusnystagmus••ItIt isis causedcaused byby a a dysfunctiondysfunction of the of the labyrinthlabyrinth or or vestibularvestibular nervenerve causingcausing ananasymmetryasymmetry in the in the signalsignal fromfrom the the rightright and and leftleft semicircularsemicircular canalscanals..

••ThereThere are are violentviolent vestibularvestibular dysfunctionsdysfunctions withwith vertigovertigo, and , and lowlow hearinghearing. The . The nystagmusnystagmus isis oneone--directionaldirectional withwith rapidrapid phasephase directeddirected towardstowards the the healthyhealthyside. The side. The amplitudeamplitude of the of the oscillationoscillation increasesincreases whenwhen the the gazegaze isis in the in the direction of the direction of the rapidrapid phasephase ((AlexanderAlexander’’s s rulerule)) whilewhile the the trajectorytrajectory isis generallygenerallymixedmixed, , horizontalhorizontal--torsionaltorsional, , nevernever purelypurely verticalvertical or or torsionaltorsional. .

••FixationFixation reducesreduces the the nystagmusnystagmus asas the the movementsmovements due due toto the visual the visual stimulistimuliare are normalnormal and and balancebalance the the oscillationoscillation causedcaused byby the the vestibularvestibular dysfunctiondysfunction. . OscillopsiaOscillopsia and positive and positive RombergRomberg’’s test are common, s test are common, withwith the direction of the the direction of the fallfall dependingdepending on the position of the head. on the position of the head.

••The The mostmost common common causescauses include include vestibulitisvestibulitis, , neuronitisneuronitis, , ischaemicischaemic lesionslesions, , traumastraumas, and , and drugdrug toxicitytoxicity. .

2) 2) CentralCentral vestibularvestibular nystagmusnystagmus••ItIt isis causedcaused byby a a lesionlesion of the of the centralcentral vestibularvestibularconnectionsconnections (the (the vestibularvestibular nuclei and nuclei and theirtheir projectionsprojections, , includingincluding the the vestibulocerebellumvestibulocerebellum). ).

••VestibularVestibular symptomssymptoms are are generallygenerally lessless accentedaccented and and longerlonger lastinglasting withwith respectrespect toto the the peripheralperipheral formform. .

••FixationFixation doesdoes notnot inhibitinhibit the the nystagmusnystagmus and the position and the position of the head of the head doesdoes notnot influenceinfluence RombergRomberg’’s test. s test. VestibuloVestibulo--ocularocular movementsmovements and and pursuitpursuit are are frequentlyfrequently alteredaltered

••NeuroradiologicNeuroradiologic examinationsexaminations are are alwaysalways indicatedindicated. .

TypesTypes of of centralcentral and and peripheralperipheral vestibularvestibular nystagmusnystagmus::••Vertical nystagmus, Vertical nystagmus, downwardsdownwards.. Cerebellar Cerebellar lesionslesions, , lesionslesions of the of the cranialcranialbasebase--spinalspinal cordcord junctionjunction ((ArnoldArnold--ChiariChiari malformationsmalformations)) or of or of regionalregionalvesselsvessels. . NystagmusNystagmus isis presentpresent in the in the primaryprimary position and in the position and in the laterallateral gazegazeand and increasesincreases in the in the downwardsdownwards gazegaze..

••VerticalVertical nystagmusnystagmus, , upwardsupwards. . IntrinsicIntrinsic lesionslesions of the of the brainstembrainstem or or cerebellumcerebellum, due , due toto ischaemiaischaemia, , demyelinationdemyelination or or tumorstumors. . NystagmusNystagmus isispresentpresent in the in the primaryprimary postitionpostition, and , and hashas maximummaximum amplitudeamplitude in the in the upwardsupwards gazegaze, , butbut differentlydifferently fromfrom the the precedingpreceding nystagmusnystagmus, , doesdoes notnotincreaseincrease in the in the laterallateral gazegaze. .

••TorsionalTorsional nystagmusnystagmus.. A rare A rare formform, suggestive of , suggestive of lesionslesions of the of the brainstembrainstemsuchsuch asas syringobulbiasyringobulbia, , syringomyeliasyringomyelia, , WallenbergerWallenberger’’s s. and s s. and vascularvascularalterationsalterations..

•• Horizontal nystagmus.Horizontal nystagmus. Due to peripheral vestibular dysfunctions, it may Due to peripheral vestibular dysfunctions, it may also present as a consequence ofalso present as a consequence of central lesions. The oscillation is not central lesions. The oscillation is not reduced reduced byby fixationfixation and and isis associatedassociated toto homolateralhomolateral pursuitpursuit anomaliesanomalies. .

3) 3) GazeGaze--evokedevoked nystagmusnystagmus••A rare form of nystagmus A rare form of nystagmus withwith lowlow frequencyfrequency jerksjerks similarsimilar toto endend--pointpointnystagmusnystagmus, , exceptexcept forfor the the factfact thatthat itit presentspresents in in lessless extremeextreme gazegaze positionspositionsand and hashas greatergreater amplitudeamplitude. .

••ItIt isis due due toto alterationsalterations of the of the neuronalneuronal integratorintegrator in the control of in the control of saccadicsaccadicpulsepulse--stepstep. The . The eyeseyes cannotcannot maintainmaintain anan eccentriceccentric position and return position and return slightlyslightly backwardsbackwards towardstowards the the primaryprimary position. The position. The rapidrapid phasephase bringsbringsthe the gazegaze back back toto the the desidereddesidered direction.direction.

••SSmoothmooth pursuitspursuits and and fixationfixation are are alsoalso frequentlyfrequently alteredaltered. .

••ItIt isis associatedassociated toto cerebellarcerebellar pathologiespathologies butbut maymay presentpresent followingfollowinghemispherichemispheric or or brainstembrainstem lesionslesions whichwhich affectaffect conjugatedconjugated gazegaze mechanismsmechanisms((gazegaze--pareticparetic nystagmusnystagmus). ). ••The The mostmost common cause of common cause of thisthis nystagmusnystagmus isis the the useuse of of sedativessedatives and and antiepilepticantiepileptic drugsdrugs..

4) 4) PeriodicPeriodic alternatingalternating nystagmusnystagmus••ItIt isis a a horizontalhorizontal jerkjerk nystagmusnystagmus presentpresent in the in the primaryprimary position position characterizedcharacterized byby periodicperiodic changeschanges in direction (in direction (approxapprox. . everyevery 2 2 minutesminutes) ) ••ItIt maymay bebe congenitalcongenital or or secondarysecondary toto cerebellarcerebellar or or brainstembrainstempathologiespathologies, or due , or due toto visual visual deprivationdeprivation. . SmoothSmooth pursuitpursuit and and opticokineticopticokinetic nystagmusnystagmus are are alsoalso oftenoften alteredaltered. . ••BadofenBadofen, , myorelaxingmyorelaxing and and antispasticantispastic drugdrug, , isis ableable toto control the control the nystagmusnystagmus in the in the acquiredacquired formform..

5) 5) ReboundRebound nystagmusnystagmus••It consists in a It consists in a horizontalhorizontal jerkjerk nystagmus with rapid phase initially nystagmus with rapid phase initially directed towards the direction of gaze but which changes directidirected towards the direction of gaze but which changes direction on after few seconds of eccentric position.after few seconds of eccentric position.••It primarily occurs It primarily occurs followingfollowing alterationsalterations of the of the cerebellarcerebellarparenchymaparenchyma butbut alsoalso followingfollowing lesionslesions of the of the posteriorposterior cranialcranial fossa. fossa.

6) 6) PendularPendular nystagmusnystagmus••A A nystagmusnystagmus frequentlyfrequently encounteredencountered after after vascularvascular or or demyelinatingdemyelinating lesionslesions of the of the brainstembrainstem or or followingfollowing monolateralmonolateralvisual visual defectsdefects. . ••ItIt isis characterizedcharacterized byby pendularpendular movementsmovements withwith mixedmixed horizontalhorizontal, , verticalvertical and and torsionaltorsional trajectorytrajectory; ; thesethese characteristicscharacteristics differentiatedifferentiate ititfromfrom the the congenitalcongenital formform of of pendularpendular nystagmusnystagmus in in whichwhich the the oscillationoscillation isis purelypurely horizontalhorizontal and and becomesbecomes jerkyjerky in the in the laterallateral gazegaze. . ••InternuclearInternuclear ophthalmoplegiaophthalmoplegia, , skewskew deviationdeviation and and nystagmusnystagmus withwithupwardsupwards jerksjerks are are frequentlyfrequently associatedassociated anomaliesanomalies..

7) See7) See--saw nystagmussaw nystagmus••A rare form of pendular nystagmus characterized in the first haA rare form of pendular nystagmus characterized in the first half of lf of the cycle by the elevation and intorsion of an the cycle by the elevation and intorsion of an eyeeye withwith syncronoussyncronousdepressiondepression and and extratorsionextratorsion of the of the otherother eyeeye; in the ; in the otherother halfhalf of the of the cyclecycle the the movementmovement isis invertedinverted. . ••FrequentlyFrequently associatedassociated toto tumourstumours of the of the chiasmaticchiasmatic regionregion. .

8) Sensitive 8) Sensitive nystagmusnystagmus••ItIt presentspresents followingfollowing lesionslesions of the of the afferentafferent visual system visual system withwithlossloss of of centralcentral vision. In vision. In thisthis situationsituation, the , the capacitycapacity of of maintainingmaintainingstablestable foveationfoveation isis lostlost due due toto micromovementsmicromovements of the of the fixationfixationsystem. system.

••The The severityseverity of the of the nystagmusnystagmus dependsdepends on the on the severityseverity of the of the visual visual defectdefect. In the case of . In the case of bilateralbilateral visual visual reductionreduction, the , the nystagmusnystagmus isis conjugatedconjugated and and prevalentlyprevalently pendularpendular, , isis reducedreduced bybyconvergenceconvergence and and oftenoften accompaniedaccompanied byby oscillationsoscillations of the head of the head ififthe visual the visual defectdefect presentspresents in the in the earlyearly monthsmonths of life. of life.

••WhenWhen the visual the visual defectdefect isis monolateralmonolateral, , fixationfixation instabilityinstability withwithprevalentlyprevalently verticalvertical oscillationsoscillations, more , more evidentevident on the on the affectedaffected side, side, are are presentpresent..

9) 9) ConvergenceConvergence retractionretraction nystagmusnystagmus••ThisThis anomalousanomalous movementmovement isis frequentlyfrequently foundfound in the in the posteriorposteriormesencephalusmesencephalus syndromesyndrome ((ParinaudParinaud’’s s.).s s.).

••ItIt isis characterizedcharacterized byby rapidrapid phasesphases whichwhich cause the cause the convergenceconvergenceand and retractionretraction of the of the eyeseyes in the in the upwardupward gazegaze. In . In factfact, , thisthis isis notnot a a realreal nystagmusnystagmus, , butbut ratherrather anan alterationalteration of the of the saccadicsaccadic system system withwith asyncronousasyncronous, , oppositeopposite, , adductionadduction movementsmovements. .

10) 10) DissociatedDissociated nystagmusnystagmus••ItIt isis characterizedcharacterized byby oscillationsoscillations whichwhich are are asymmetricasymmetric betweenbetween

the the twotwo eyeseyes forfor amplitudeamplitude and/or and/or trajectorytrajectory

Convergence retraction nystagmusConvergence retraction nystagmus

Convergence retraction nystagmusConvergence retraction nystagmus

Pupillary light reflex: near dissociation Pupillary light reflex: near dissociation in Parinaud's syndromein Parinaud's syndrome

CT scan of pinealomaCT scan of pinealoma

1) 1) SquareSquare--wavewave jerkjerk2) 2) FlutterFlutter and and

opsoclonusopsoclonus

OTHER OCULAR OTHER OCULAR OSCILLATIONSOSCILLATIONS

1) 1) SquareSquare--wavewave jerkjerk••These are saccadic These are saccadic intrusionsintrusions whichwhich interruptinterrupt the the fixationfixation and and whichwhich, after a , after a normalnormal intersaccadicintersaccadic intervalinterval of 200 of 200 msecmsec, are , are followedfollowed byby the return the return toto the the initialinitial position. position.

••TheyThey representrepresent anan exaggerationexaggeration of of normalnormal microsaccadicmicrosaccadicmovementsmovements associatedassociated toto fixationfixation, and , and withwith smallsmall amplitudeamplitude, , maymaybebe consideredconsidered normalnormal, , especiallyespecially in the in the elderlyelderly; ; ifif ampleample (l(l--55°°) and ) and frequentfrequent, , theythey are are generallygenerally secondarysecondary toto cerebellarcerebellar pathologypathology or or toto progressive progressive supranuclearsupranuclear paralysisparalysis..

••IfIf movementmovement amplitudeamplitude isis greatergreater thanthan 1010°° theythey are are knownknown asasmacro macro squaresquare--wavejerkswavejerks..

2) 2) FlutterFlutter and and opsoclonusopsoclonusOcularOcular oscillationsoscillations withoutwithout intersaccadicintersaccadic intervalinterval. .

••FlutterFlutter:: oscillationsoscillations on the on the horizontalhorizontal plan in the plan in the formform of of pulsespulsesof 3of 3--4 4 microoscillationsmicrooscillations whichwhich interruptinterrupt fixationfixation in the in the primaryprimary

position.position.

••OpsoclonusOpsoclonus:: involontary, chaotic, multivectorial (horizontal, involontary, chaotic, multivectorial (horizontal, vertical, diagonal) movements. This anomaly, also known as vertical, diagonal) movements. This anomaly, also known as

saccadomania, saccadomania, disappearsdisappears duringduring sleepsleep. .

••FlutterFlutter and and opsoclonusopsoclonus are are frequentfrequent in the in the coursecourse of of cerebellarcerebellarpathologiespathologies and and followingfollowing postviralpostviral encephalitisencephalitis. .

••TheyThey maymay alsoalso bebe remote (remote (paraneoplasticparaneoplastic) ) manifestationsmanifestations of of neuroblastomaneuroblastoma in the in the childchild and and visceralvisceral carcinoma in the carcinoma in the adultadult. .