bedside neuro-otological examination and interpretation of commonly used investigations

13 Pages·2004·0.3 MB·English

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BEDSIDE NEURO-OTOLOGICAL N
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EXAMINATION AND INTERPRETATION l N
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OF COMMONLY USED INVESTIGATIONS s
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JNeurolNeurosurgPsychiatry2004;75(SupplIV):iv32–iv44.doi:10.1136/jnnp.2004.054478 try
he assessment of the patient with a neuro-otological problem is not a complex task if : firs
Tapproachedinalogicalmanner.Itisbestaddressedbytakingacomprehensivehistory,bya t p
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physicalexaminationthatisdirectedtowardsdetectingabnormalitiesofeyemovementsand blis
abnormalities of gait, and also towards identifying any associated otological or neurological h
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problems.Thisexaminationneedstobemindfulofthefactorsthatcancompromisethevalueof d
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thesignselicited,andtherangeofinvestigativetechniquesavailable.Themajorityofpatientsthat s
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present with neuro-otological symptoms do not have a space occupying lesion and the over 0
reliance on imaging techniques is likely to miss more common conditions, such as benign .1
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paroxysmalpositionalvertigo(BPPV),orthefailuretocompensatefollowinganacuteunilateral 36
labyrinthineevent. /jn
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Theroleoftheneuro-otologististoidentifythesiteofthelesion,gatherinformationthatmay p
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leadtoanaetiologicaldiagnosis,andfromthere,toformulateamanagementplan. 0
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BACKGROUND 5
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Balance is maintained through the integration at the brainstem level of information from the 8
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vestibularendorgans,andthevisualandproprioceptivesensorymodalities.Thisprocessingtakes n
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place in the vestibular nuclei, with modulating influences from higher centres including the 4
cerebellum, the extrapyramidal system, the cerebral cortex, and the contiguous reticular N
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formation(fig1).Thereforeanyderangementofthestructureorfunctionofthesensoryinputs, v
ce
tshpeiMncaaelnnpytarcatohlnwvdeaisyttiisob—nusliaswrliiskltlereulylcuttduoererdesisaougrlnttohinseisaefifbfeabclataolnarcnpecaedthiisswoeraqdyuesra—.tetdhaptuirse,ltyhweiotchualodmisootrodrearnodfvveessttiibbuulloar- opyrighmber 2
function. Drachman and Hart1 have emphasised the importance of multi-sensory dizziness, t.004
particularly in the elderly, when two or more of the following conditions are present: visual . D
impairment, peripheral neuropathy, vestibular deficit, cervical spondylosis, and orthopaedic ow
disorders affecting the large joints. An appreciation that dysequilibrium may be consequent on n
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multiplepathologiesisessentialiftheappropriateinvestigationandinterpretationofthedataare a
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tobeachieved. e
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General medical conditions similarly may contribute to dizziness—that is, postural hypoten- fro
sion,vasovagalsyncope,cardiacvalvardisease,hyperventilation—andafullandcomprehensive m
historyisvital.Ageneralmedicalexamination,withparticularattentiontotheeyes,theears,the h
ngeenrveoraulsmsyesdtiecmal,inthveesctiagradtiioovnasscsuhloaurldsyasltseomb,eacnodnstihdeerleodc.omotor system, may be indicated and ttp://jn
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SECTION 1 m
Aural examination j.c
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Acarefulinspectionoftheearisneeded,asanyotologicalpathologyislikelytopointtheclinician m
to a peripheral rather than a central neuro-otological lesion. It includes examination of the o/
auricle,the external auditorymeatus, andthe middle ear—that is,asfaras canbeassessed by n D
examinationofthetympanicmembrane(TM).Thetympanumoffersawindowintothemiddle e
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ear cleft and is affected by most of the changes that can take place in the middle ear. Otitis e
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externa,acute otitis media orTM perforation contraindicate caloric testing. Waxalso precludes b
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caloricirrigationsbecauseitactsasaheatseal,andalsowhenimpactedgivesrisetoaspurious r 3
conductivehearingloss. 1
_________________________ Inspectionoftheearmaybecarriedoutwiththeuseofanotoscopeorwithahead-wornlight , 2
0
Correspondenceto: source,leavingthehandsfree.Thespeculumshouldbedirectedaroundthecircumferenceofthe 22
DrRosalynDavies,The outerearcanallookingfordebris,foreignbodies,inflammation,andfordefectsoftheposterioror b
NationalHospitalfor y
NeurologyandNeurosurgery, anteriorwall.ThemagnifyinglensoftheSiegel’s(orpneumatic)speculumcanbefittedintothe g
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QueenSquare,London speculum and the bulb squeezed to raise intrameatal pressure and then relaxed, sucking the e
WdaCvi1eNs@3uBclGh.,oUrgK;rosalyn. membrane outwards. In the presence of a middle ear effusion, the membrane is immobile; st. P
_________________________ howeverwithaveryflaccidTM,thismayhavebeensuckedbackontothemiddleearmucosa,and ro
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Higher centres Figure1 Sensori-motorphysiologyof u
• Extrapyramidal system themaintenanceofbalanceshowingthe ro
• Cerebellum threesensoryinputsrequiredfor l N
• Reticular formation maintenanceofequilibrium,thecentral eu
modulatinginfluences,andtheefferent ro
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pathways. u
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Vision Perception of try
orientation : firs
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Brain stem h
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Proprioception integrating Osycstuelmomotor d a
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centres 0
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1
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6
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0
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Antigravity 4
Vestibular muscles of .0
labyrinths 5
posture 4
4
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8
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lowering the pressure may suck it out again, allowing a c Osteomasareroundedexcresencesofbone n
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retraction pocket to be distinguished from a perforation. c Exostoses are small osteomata and are quite common in 4
Alternatively, the Valsalva manoeuvre—that is, auto-infla- peoplewhoswimordiveregularly. N
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tionoftheear—canbeusedtoraisemiddleearpressureand cve
tEoxoabmseinrvaetisoimniolafrtchheanaguersi.cle (pinna) EeWIfxaaarimxmpinaactteido,n oorf thoebstcyumrinpgantihcemevmiewbraonfe athned mtymidpdalneic opyright.mber 200
The auricle is essentially vestigial, contributing only to 4
collection of sound, slightly enhancing the efficacy of the membrane,thecerumenmustberemovedcarefullywithout . D
causing pain to the patient. Hard lumps can be removed o
ear.Itshouldbeinspectedforsignsofinflammation,trauma, w
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surgical scars, or haematoma auris following a blow to the lo
ear,andalsoforcongenitaldeformities.Mostdevelopmental Syringing ad
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aidbennotrifmieadlitbieecsauasreeoffatihrleylikoeblvyioausss,ocbiauttedmfiunsdtinbgesocfamreifdudlllye AcbTshoeluptreesceonncetroafinandiecaartiinofnesctitoons(oytritiinsgeixntegrnaormedia) d fro
andinnerearabnormalities—thatis,anotia(absentauricle); c Theearisknowntohaveaperforation hm
microtia (smaller than normal and probably misshapen c Fromthehistory,theearissuspectedtohaveavulnerable ttp
apuopriucllea)ti.oPnr;ef-iasuturliacualuarrisa,papesmndaallgbeslinadrepfitousenedniannt1e.5ri%orotof tthhee tympanicmembrane ://jn
Method n
tragus, results from incomplete fusion of the auricular p
(1) Withthepatientseatedinachair,protecthim/herwith .b
tubercles. m
aplasticcapeandtowel
(2) Askthepatienttoholdakidneydishreceiveronthe j.co
Examination of the external auditory meatus shoulder,justbelowthepinna m
Congenital conditions include a stenosed or atretic external (3) Drawupinametalsyringeasolutionofsterilewater o/
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auditorymeatus(EAM).Inthelatter,theEAMisclosedover of37˚C(anyvariationfromthiswillcausevertigo) D
withamembranous,straightbonywallacrossthecanal.This (4) Drawthepinnaupwardsandbackwards ec
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abnormality can be graded according to severity and radio- (5) Placethenozzleafewmillimetresintothecanal, m
logicalinvestigationneedstobepursuediffound,toidentify pointingupwardsandbackwards be
thesizeandshapeofthemiddleearcavity,andpossibilityof (6) Directthestreamofwateralongtheroofofthecanal, r 3
associatedinnereardisorders. Noteb:etweentheskinandthewax 1, 2
Acquiredabnormalitiesinclude: 0
c Syringingshouldnotbepainfulandshouldbestoppedif 2
c Foreignbodyobstruction 2
thepatientcomplainsofpain b
c Otitis externa. Likely infections: staphylococcus, pseudo- y
c With appropriate instruction, nursing staff can carry out g
monas and diphtheroids; fungal infections—that is, u
thisprocedure e
aspergillus and candida; and viral infections, identified s
by the vesicular eruptions of herpes zoster—that is, c Auralsuctioninthehandsofanotologistmayberequired t. P
Ramsey-Huntsyndrome ifthewaxisnoteasilyremovedbytheabovemeasures ro
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usingtheJobson-Hornprobe,oraCawthornewaxhook.An e
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alternativemethodforremovingwaxissyringing.Ifthewax ro
seems very hard, it can be softened over a period of weeks l N
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using warm olive oil drops administered nightly, or alter- u
natively 5% sodium bicarbonate drops, or a ceruminolytic ro
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preparationavailablecommercially. urg
iv34 P
Tympanic membrane and middle ear sy
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The standard landmarks of the tympanic membrane (TM) h
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are: the central portion with handle of the malleus visible try
tthenrosauginhfethrieordlyru;mide;nthtieficpaatrisonflaocfctihdealsounpgepriroorcleys,saonfdththeeinpcaurss : firs
and the stapedius tendon seen in more TMs. The following t p
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areimportantfeaturestoidentify: b
c Perforations—when seen in the pars tensa, these are lish
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classified as marginal or central; defects of the attic d
portion are described as attic perforations; and the a
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positionoftheperforationisdefinedasanterior,inferior, Figure2 Acuteotitismedia:otoscopicappearanceoflefttympanic 1
membrane.ReproducedwithpermissionofProfessorAnthonyWright, 0
or posterior; large central perforations are described as .1
InstituteofLaryngologyandOtology,London. 1
subtotalandlargemarginalperforationsastotal. 3
6
c Colour—thenormaleardrumhastheappearanceofmother keratin debris in the pars flaccida area on otoscopic /jn
ofpearl.Thelightreflexisfoundantero-inferiorly,where examination. It is potentially serious and requires surgical np
reflection of the examination light occurs. If the mem- removal. .2
0
brane is thickened, the reflex may be lost. If the middle Tubo-tympanic disease describes chronic active otitis 0
4
layer of fibrous tissue of the TM undergoes hyaline media unassociated with cholesteatoma. It is characterised .0
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degeneration it may become impregnated with deposits by recurrent infections rather than persistent infections and 4
4
ofcalcium—thatis,tympanosclerosis. by odourless discharge rather than offensive discharge. A 7
8
c Position of the membrane—Retraction of the membrane centralTMperforationandabreakintheossicularchainor o
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occurs when there is chronic lowering of pressure in the malleus fixation are regarded as ‘‘safe’’ and unlikely to be 2
middleear—thatis,chronicobstructionoftheEustachian associatedwithcholesteatoma. 4 N
tube.Thehandleofthemalleusisdrawninwardandthere Serousotitismediaisrecognisedbyanair/fluidlevelinthe o
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is retraction of the drum toward the medial wall of the middleear,orabluishdiscolourationofthedrum.Alackof coem
mlonidgdpleroecaers.sWohfethneseinvceures,athneddhreuamdoisfssttraeptecsh,eadnadroautnwdotrhste, ceoffmuspiloiannscientoof tthhee dmruidmdleisefaorunindcloundetybmlopoadno(mfoertreyx.aOmtphleer, pyrighber 2
the membrane is plastered against the promontory. (A haemo-tympanumafterheadtrauma)orcerebrospinalfluid t.00
frleusiudlteledveflrommayredbuecvtiiosnibloefifmsidecdrleetoerayroptrietisssumree.dIian hthaes withinthemiddleearspace. 4. D
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presence of air bubbles, middle ear fluid is confirmed.) Otosclerosis wn
With raised middle ear pressure, the drum may bulge This is an inherited, autosomal dominant hearing disorder, lo
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outwards and depending on the colour, this increased tending to present in later childhood/adulthood. Deposition d
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motiitdidslmeeedairap(rcehsesrurryeremda)y,obreifcaaunsoerdmbalycaoclouuter,stuhpepbuurlagteivies othfebosnteapinesthfeoootvpallawteinadnodwnaicchoenodcuccutrisveleahdeianrgintogfilxoassti.onThoef d fro
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likelytobecausedbyraisedairpressureinthemiddleear otosclerotic process can extend to involve the otic capsule, h
alone. leading to an additional sensori-neural hearing loss and ttp
vertigo. Typically in the early osteoblastic phase, the ://jn
Disorders of the tympanic membrane and middle ear appearance of the malleus head is hyperaemic—that is, n
p
Congenitalabnormalitiesincludefusionoftheossicles—that Schwartze’ssign. .b
is, congenital stapes fixation, absent stapedius tendon, and m
uncovered or aberrant VIIth nerve. Acquired disorders Glomus tumour j.co
includeacuteotitismedia(fig2),chronicotitismedia,chole- This is a jugulo-tympanic paraganglionoma which tends to m
steatoma,serousotitismedia,andossicularabnormalities. expand within and traverse the petrous temporal bone by o/
n
Cholesteatoma is a cyst lined with squamous epithelium, way of the pneumatised air cell tracts. It can present with D
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whichcan arise in ears undergoing long periods of negative pulsatile tinnitus, and a vascular mass lying behind the c
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middleearpressureandpersistingmiddleearinfection—that tympanicmembranecanbeidentified(alsodescribedasthe m
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is,chronicsuppurativeotitismedia.Cholesteatomatouscysts ‘‘settingsun’’sign).Thesetumoursmayalsoextendintothe e
arelikelytobeginintheatticoftheearandextendintothe labyrinth,orpresentascranialnerveabnormalities. r 3
1
mastoid antrum. They are filled with cast-off epithelial cell , 2
debris and slowly increase in size. They can erode the TESTING OF AUDITORY FUNCTION 0
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surroundingboneandproduceintracranialcomplicationsby Tuning fork tests 2
b
erodingthroughtheduraofthemiddleorposteriorfossa,or Tuningforktestshavebeentraditionallyusedtodistinguish y
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throughthelateralsinusorintothelateralsemicircularcanal conductive from sensorineural hearing loss and to identify u
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(when a positive fistula sign would be elicited, see below). functional hearing loss. With the advent of pure tone s
Cholesteatoma can be diagnosed from a history of per- audiometry,onlyafewofthesetestsarestillusedclinically. t. P
foration, chronic foul smelling discharge from the ear, and Theprinciplesoftuningforktestsare: ro
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Fistula sign Weber’s tuning fork test u
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This is elicited in those patients where transmission of air TheaimofErnstWeber’stest(1934)istoidentifythebetter l N
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pressurechangesfromtheEAMispossiblethroughafistula hearing cochlear. It is used in conjunction with Rinne’s test u
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intothelabyrinth: andisofmostuseinpatientswithunilateralhearingloss: s
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c raisedpressurecausesa conjugatedeviationoftheeyes (1) The512Hztuningforkisstruckandplacedtothehead rg
towards the opposite ear and with maintenance of inthemidline,eitheratthevertexorontheforehead iv35 P
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pressure, a corrective fast eye movement will be (2) Thepatientisaskedtosaywhetherthesoundisheard y
c
introduced. betterinoneear,orequallyinbothears hia
c thenystagmuswillbetowardstheaffectedear AcentralWeberisdescribedifthetoneisheardcentrally try
nysDtaepgemnudsinwgillobne:where the fistula has developed, the c AidleantetirfiaelsisaingnoWrmeablehreisawrinhgenptahteietnotneisheardtooneside : firs
c horizontal(horizontalsemicircularcanal) c identifiesthesideofthebetterhearingcochlear t p
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c torsional(anteriorcanal) c BUT, if there is a conductive component to the hearing b
c vertical(posteriorcanal) loss,thetonemaybeheardinthepoorerhearingear(see lish
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EAMpressuremayberaisedbytragalpressure,butmore Rinne’stest) d
accurately by tympanometry. Hennebert’s sign is a positive The results need to be interpreted with care and only in as
fistulasigninthepresenceofanintactTM. conjunctionwithfurtherhearingtests. 1
0
.1
1
3
c theinnerearismoresensitivetosoundconductedbyair overtones, twothirdsofthewayalongitstinestominimise 6/jn
thanbone distortionproducts. np
c inpureconductivehearingloss,theaffectedearissubject The clinical findings described above will point to the .2
tolessenvironmentalnoiseandismoresensitivetobone appropriatetestbatterytoinvestigatefurtheranyassociated 00
4
conductedsound. hearingloss.Puretoneaudiometryshowstheexistenceand .0
extent of hearing loss and allows determination of whether 5
Themostcommonlyusedtuningforksarethoseat256and 4
512Hz. Lower frequencies produce a vibrotactile stimulus the loss is conductive, or sensorineural, or both. It requires 478
which can result in misleading thresholds. In practice the the cooperation of the subject and as such is a subjective o
256Hz tuning fork better distinguishes air–bone gaps than estimate of hearing thresholds. As a psycho-acoustic mea- n 2
surement, the results of audiometry may be biased by 4
the 512Hz fork. When performed, the prong (tine) of the N
tuningforkshouldbestruckagainstahard,butelastic,mass particular methods of conducting the test, and so a well ov
defined procedure must be adopted. If the patient is unable ce
(for example, a rubber pad) to prevent production of om
Rinne’s tuning fork test othireoanurninwwgii.lllliTnbhgeetsoeneccaoedosdpsieatrrioaytneat,oladtpedrsiottvsioidnienalcloaubudjdeeciotmilvoegeaicsmaulereainmsvueernsetstigaoo-ff pyright.ber 200
otoacoustic emissions, stapedius reflex threshold measure- 4
HeinrichRinnedescribedhistuningforktestin1855 ment,andbrainstemauditoryevokedresponses. . D
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(1) Theforkisstruckandheldwiththetinesperpendicularto The purpose of aural admittance testing—that is, tympa- w
n
thelongaxisoftheexternalauditorymeatuswiththe nometry—is the objective determination of middle ear lo
closesttine1cmfromtheentrancetothemeatus pressure, the measurement of static acoustic impedance, ad
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(2) Thepatientisaskedtoreportifhecanhearthesound and characterisation of the tympanometric shape. High d
(AC) impedance abnormalities include a perforated tympanic fro
(3) Theforkisimmediatelytransferredbehindtheearwith membrane, middle ear effusion, retracted tympanic mem- m
thebasefirmlypressedtotheboneoverlyingthe brane, or ossicular fixation. Low impedance abnormalities http
(4) mThaestpoaidtie(nBtCis)askedwhichsoundislouder:that‘‘infront idniscrluudpetiotnhifnollaotwroinpghihcetaydmtpraaunmica.membranes and ossicular ://jn
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oftheear’’,orthat‘‘behindtheear’’ p
PositiveRinnetest:ifAC.BC—thatis,thesoundinfront SECTION 2 .bm
oftheearisreportedaslouder: Clinical examination of eye movements j.c
c indicatesnormalhearing Examination of the eye movements requires optimal condi- om
c oranearwithasensorineuralhearingloss. tions.Thereshouldbegoodlightingwiththepatientsitting o/
Negative Rinne test: if BC.AC—that is, the sound in n
comfortably,headerect.Theclinicianshouldbeawareofthe D
frontoftheearisreportedasquieter: visualacuityofbotheyes,usingtheSnellenchartat6m.The ec
c identifies a significant conductive component of hearing e
eyesshouldbeintheprimarypositionofgazeandthevisual m
lossof.15dBHL targetheldatadistancejustgreaterthanthepatient’sfocal b
c BUT,afalsepositiveRinnecanoccurifthereisasevere point. er 3
sensorineural hearing loss in the tested ear, as the BC 1
stimulus is heard in the non-tested ear because of , 2
Cover test for strabismus 0
transcranial transmission, and thus will be louder than 2
Thepresenceofamanifestoralatentstrabismusneedstobe 2
AC sound. This can be overcome by masking the non- b
determined. Either can cause an abnormal eye movement y
affectedearwithaBaranynoisebox. g
examinationbecauseofchangingopticfixationfromoneeye u
TheRinnetesthasahighspecificityforconductivehearing e
totheother.Whenoneeyehasbecomeamblyopic,theother s
lboosns,ebguatpa.low30sednBsitivity,thisnotreaching90%untiltheair– eye should be assessed for both clinical and electro- t. P
nystagmagraphic purposes. To perform the cover test, each ro
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eyeiscoveredinturn,eitherwiththehandorapieceofcard, involvestheparasympatheticfibrescarriedwiththeIIIrd e
u
close tothe eye toprevent optic fixation of the covered eye. nerve ro
Thepatientisaskedtofixateonavisualtargetandthenthe c a lesion of the IVth cranial nerve causes the eye to be l N
coveredeyeobservedasthecoveristakenaway. slightly elevated, leading to adduction of the eye and a eu
(1) Manifest strabismus/exotropion is identified when the possible head tilt to the side to the lesion, to reduce ro
s
affected eye is turned outwards during normal gaze. diplopia u
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iv36 An esotropion is identified when the eye is turned c a lesion of the VIth cranial nerve causes a loss of P
inwardduringnormalgaze. abductionandagaintheheadmaycompensatebyrotating sy
(2) Anexophorioninthecoveredeyeisidentifiedwhenthe towardsthesideofthelesion. ch
covered eye moves inward as the cover is removed. An ia
eosuotpwhaorrdisonwitihs ried-efnixtaiftiieodn.as the covered eye moves OThceurelararsetathbrieliesivnigsusayllsytecmonstrolled systems producing eye try: firs
(3) Latent nystagmus is identified when nystagmus is movements that stabilise gaze: the saccadic system, the t p
seen in the uncovered eye during cover testing. u
smooth pursuit system, and the optokinetic system. The b
Typically, the nystagmus beats away from the covered saccadicsystemrespondstoerrorinthedirectionofgazeby lis
h
eye and is conjugate. Latent nystagmus can be uni- or initiating a rapid eye movementto correcta retinalposition ed
bilateral and is congenitally determined. In some error; the smooth pursuit system is responsible for main- a
patientsitcanbeassociatedwithcongenitalnystagmus s
taininggazeonamovingtargetbykeepingthetargetwithin 1
(videinfra). 0
the visual field; the optokinetic system is thought to be a .1
1
moreprimitiveformofsmoothpursuit,involvingthewhole 3
Range of eye movements 6
The eyes are examined for range in both horizontal and retinainsteadofthefoveaalone.Thesesystemscaneachbe /jn
tested and normal function is likely to indicate integrity of n
vertical planes to a limit of 30˚from the midline. The eye p
centralvestibularpathways. .2
movements are conjugate if both eyes move together. If the 0
0
movementsareconjugatebuttherangeisnotfull,thepatient 4
Saccades .0
mayhaveagazeparesis. 5
This is a fast eye movement with a velocity between 350– 4
4
600˚/second,thevelocityincreasingwithincreasedamplitude 7
Gaze paresis 8
ofeyemovement.Saccadescanbevoluntaryorinvoluntary, o
Agazeparesis occurs ifthereis arestriction in the rangeof n
eyemovements,inoneormoredirections.Itmaybenuclear the former used to move the eyes between visual targets in 2
or supranuclear, with reference to the oculomotor nuclei theshortestpossibletime;theinvoluntarysaccademaintains 4 N
thetargetonthefoveawhentherehasbeenslipoftheretinal o
withinthebrainstem: v
image,andisthefastphaseofnystagmus.Thesaccademay ce
c contralateral horizontal gaze paresis occurs in lesions of om
c tiphseilfartoenratallgeayzeefpiealrdessiisnmthaeyciodretenxtify a lesion of the teg- bofevviseustailblyultarriggoerredce,ravsicianlooprtiogkinin,etwicitnhystaagmfausts,pohracsaenboef pyrighber 2
mentum, or of the ponto-medullary or ponto-mesence- nystagmus shifting the eyes in the direction of the ongoing t.00
head movement before the slow phase compensatory drift. 4
phalicjunctions Normalsubjectsareaccurateuptoatargetjumpof20˚,above . D
c supranuclear gaze palsy can be seen in mesencephalic o
whichasmallcorrectivesaccadeisrequiredtobringthefovea w
lesions, in which there is loss of volitional gaze, with n
vertical movements being lost before horizontal. This is on target. Overshooting is rare. The normal saccadic latency loa
beforeanewsaccadecanbegeneratedis200ms. d
identified by finding a full range of eye movements in e
Theabilitytogeneratesaccadesdependsontheintegrityof d
rveessptiobnusleo-otocuilnarvorleufnletxar(yVOreRf)letxestteinstgi.ng—that is, vertical projections between the frontal eye fields, the caudate from
nucleus, the substantia nigra reticulate, and the deep and h
Ocular paresis intermediatelayersofthesuperiorcolliculus.Projectionsare ttp
Warehedryestchoenrjeuigsaated—isasoncioactuiolnaropfaeryeesmisoivselmikeenlyts.—Ththeaptaist,ietnhte’ys tfhroemn htoerethteoptharea-ippsoinlattienrealreatbidcuulcaernsfonrmeravteionnuc(lPeuPsRFa)ndanbdy ://jnn
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eyes should be examined for IIIrd, IVth, and VIth nerve the median longitudinal bundle (MLB) to the contralateral .b
oculomotor nucleus of the medial rectus. The pretectal m
palsies: neurons also project to the oculomotor nuclei, both sets of j.c
(1) The oblique muscles are tested when the eyes are o
asydsdtuemct,edw;illthleowseurptehreioreyeobalniqduec,ontvherrosuelgyhthitesinpfuerllieoyr neuronsconnectingtothevestibularnuclei. onm/
obliquewillelevatetheeye Clinical assessment D
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(2) The rectus muscles are tested with the eye abducted, Saccadiceyemovementsareassessedbyaskingthepatientto c
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with the inferior rectus lowering the eye and the lookbackandforthbetweentwotargetsinfrontofhim/her, m
b
superiorrectuselevatingtheeye. sitedapproximately30˚totherightand30˚totheleftofthe e
An ocular paresis may be caused by a retro-orbital space midline, respectively. Increasing the distance between the r 3
1
occupying lesion or by involvement of the extra-ocular targets beyond 30˚ increases the chance of detecting a , 2
muscles—that is, thyroid eye disease, mitochondrial cyto- hypometric saccade, while reducing the distance increases 0
2
pathyormanifeststrabismus.LesionsoftheIIIrd,IVth,and thechanceofdetectingahypermetricsaccade. 2
b
VIth cranial nerves, or their nuclei, cause a paresis in the y
g
directionofthepullofthemusclestheyinnervate: Abnormalities of saccadic eye movements u
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c a lesion of the IIIrd cranial nerve causes the eye to be Three variables are examined: saccadic reaction time s
drawn down and out, and may ormay not be associated (latency), saccadic velocity, and saccadic accuracy. t. P
with ptosis and a dilated pupil—that is, if the lesion Abnormalities of any of these features may be caused by ro
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centralnervoussystem(CNS)pathologyorocularmyopathy. e
u
Peripheral vestibular pathology does not cause abnormal ro
saccadiceyemovements. l N
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c Internuclear ophthalmoplegia (INO)—caused by a lesion of u
the ipsilateral MLB. May present as ataxic nystagmus, ro
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whereby adducting saccades ipsilateral to the lesion are rg
slower than abducting saccades. Subtle early lesions can iv37 P
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be revealed by electronystagmography (ENG) recordings y
c
ofseparateeyesaccades,showingslowingoftheadduct- h
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ing saccade on the side of the lesion with a normal try
c Lveesloiocnityo,fbPuPtRaFh—yptheirsmecatruicseasbdlouscstinogfsaalclcatdypee(sfigof8)rapid : firs
ipsilateral movements and the eyes move to the contral- t p
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ateral visual field. In response to vestibular or visual blis
stimulation, the eyes display a tonic contralateral devia- h
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tionwithlossofthefastphaseofnystagmus. d
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c One-and-a-half syndrome—seen with extensive brainstem s
1
pathology affecting both the ipsilateral PPRF and the 0
median longitudinal bundles. This syndrome can result Figure4 Optokineticstimulus(seetext).Reproducedwithpermission .11
3
with a failure of conjugate gaze in one direction and an fromJaegerToennies,Wurzburg,Germany. 6
internuclearophthalmoplegiaintheother. /jn
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The pathways subserving vertical and horizontal saccades c Frontal pathology—there may be hypometria or loss of p
.2
areindependent, such thatvertical saccades areunimpaired horizontalsaccades,contralateraltothesideofthelesion. 0
0
by lesions of the PPRF, while lesions of the mesencephalic Verticalsaccadesarenotaffected. 4
.0
reticularformationaffectverticalsaccadesexclusively. 5
4
c Cerebellar pathology—may affect the accuracy of saccades Smooth pursuit 4
7
with undershooting (hypometria) and/or overshooting Smooth pursuit is responsible for maintaining gaze on a 8
o
(hypermetria) ipsilateral to the side of the lesion. Hyper- movingtargetsothatthetargetisstabilisedonthefovea.The n
metria is more common in cerebellar lesions than hypo- gainofthepursuitsystemapproachesunityatpeakvelocities 24
metria,whileinintrinsicbrainstemlesions,hypometriais of30˚/sorsinusoidalrotationat0.1Hz(Balohetal2).Abovea N
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morelikely peakvelocityof60˚/s,orsinusoidalrotationat1Hz,thegain v
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reaction time is prolonged. In these conditions, hypo- system are complementary in stabilising the retinal image, t.004
metria cannot occur. Vertical eye movements are usually withthepursuitsystemefficientatlowtargetvelocities,and . D
affected before horizontal, initially with upgaze more thevestibulo-ocularsystemefficientathighinputvelocities. ow
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pursuit Clinical assessment ad
The smooth pursuit system can be examined clinically by ed
movingatarget—thatis,theexaminer’sfinger—slowlyback fro
and forth in a sinusoidal fashion, initially in the horizontal m
Active optokinetic nystagmus adpneisrdpiplahtcheeremanlevnientstfitrbhouemlarvtehdreitsicomardliedprlsilna,ens,me,aototot0h.2ap–u0mr.s4auHxitizmi.suInmnorcmohfarol.3n0ic˚ http://jn
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Passive optokinetic nystagmus be ipsilateral or bilateral. Pursuit eye movements are ec
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symmetrically affected by age, psychotropic medication, m
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Optokinetic nystagmus , 2
The function of optokinetic nystagmus (OKN) is thought to 0
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bethe stabilisation oftheeyes relative tospaceduring slow 2
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headmovementsinthelowfrequencyrange,illservedbythe y
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Seconds VOR—forexample,thepersonlookingatthesceneryfroma u
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Figure3 Activeversuspassiveoptokineticnystagmus(OKN)(see eralretina,theaccessoryoptictract,thevestibularnuclei,and t. P
text). thereticularformation.TherearetwotypesofOKN(fig3): ro
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c Congenital nsyatgmus: reversal of OKN is a significant e
Drum right u
featureinmanycasesofcongenitalnystagmus(fig5).The ro
RT nystagmusbeatsparadoxicallyintheoppositedirectionto l N
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phase eye movements in opposite directions. For clinical s
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origin, and is only likely to be peripheral if seen in the first t p
few days of vestibular neuritis or an acute episode of ub
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Figure5 Congenitalnystagmusshowingtheoptokineticresponseina Physiological vestibular nystagmus d a
patientwithcongenitalnystagmus—thatis,reversalofOKNwiththe s
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induced more through foveal input, and can be induced vestibularinducedeyemovementdeviationisinterruptedby .2
bothbyusingasmalldrumandbyafullfieldoptokinetic a fast eye movement in the opposite direction, generating 00
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stimulus physiological nystagmus. This type of nystagmus can be .0
induced both by rotary chair testing and caloric irrigations 5
c Subcortical optokinetic nystagmus—passive or ‘‘stare’’ OKN, 4
inwhichitisbelievedthattheperipheralretinaisinvolved butalsobyextremesofeyedeviation—thatis,morethan30˚ 47
8
withoutparticipationofthecerebralcortex laterally from the primary position (physiological end point o
nystagmus). n
Although the two tracings appear similar, in the active 2
There is a relation between the magnitude of nystagmus 4
situation,theslowcomponentvelocityissimilartothespeed N
andthestateofarousalinhumansubjectsduringvestibular
of the drum—that is, the gain approaches 1. Also, with o
reversal of the drum direction, the eyes deviate in the stimulation. A subject who is allowed to daydream has a covem
ddcoiirrneedccitttiiiooonnn,ooffsumtbhsoeevrsevlmoedwenbctyoomfthpteohneseudnbrtcu—omrtth.icaHatloiwsp,aettvhhewer,asiyan,mttehheeassstltaohrwee ltcooinwpgeerrrefsoploremwateccdoomnatnpingouunloeaunrstavmceceleonlectiratayltaitorhniatshn—mthfeoetricse.uxSbaujmebcpjtelwcet,hsicoeexispskeaarsitkeeenrds- pyright.ber 200
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component velocity is consistently less than drum velocity, responsewithareductionorlossofnystagmusinresponseto . D
and with drum reversal, the direction of eye deviation is in o
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thedirectionofthefastphaseofthenystagmus. n
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Pathological vestibular nystagmus (spontaneous a
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Clinical assessment nystagmus) e
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Aqualitativeassessmentmaybeundertakenatthebedsideor Spontaneous nystagmus results from an imbalance of tonic fro
in the outpatient department using a small handheld or signals arriving at the oculomotor neurones. Because the m
mechanically driven optokinetic drum. This is a cylinder vestibularsystemisthemainsourceofoculomotortonus,itis h
30cmdiameterthatcanberotatedtoelicitnystagmuseither the driving force of most types of spontaneous nystagmus, ttp
in the horizontal or vertical plane, at speeds from 40˚/s hence the name vestibular nystagmus. There is a constant ://jn
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upwards. p
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c Peripherallesions—theimbalanceofvestibulartoneresult- Left e
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drum. It is best seen with direct observation of the eyes r 3
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Figure6 Peripheralversuscentralnystagmusidentifyingtheeffectsof b
abnormalities of smooth pursuit, and abnormalities of y
fast components mirror abnormalities of voluntary sac- gspaoznetatensetionugsinnyastapgamtieunstownitgha:z(Ae)leaftpisereipnhhaernaclevdeisntibthuelaarbdseefnicciet—otfhe gu
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brainstem and cerebellum result in impaired OKN when infrequencyandslowcomponentvelocityintheabsenceofoptic t. P
thestimulusismovedtowardthedamagedside. fixation. ro
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caused by a peripheral vestibular lesion. Symmetrical e
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gaze evoked nystagmus is commonly observed following ro
the use of anticonvulsants, particularly phenytoin and l N
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phenobarbitone, and ingestion of psychotropic drugs and u
alcohol. Asymmetrical horizontal gaze evoked nystagmus is ro
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Positional nystagmus y
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Nystagmus can be elicited by critical head positioning in hia
certainpathologicalstates.TheDix-Hallpikeheadmanoeuvre try
(bfeitgw7e)enisathvealupaebrilpehteersatlinnysustcahgmpautsienotfsabnendigcannpdaisrotixnygsumisahl : firs
positionalvertigo(BPPV),centralpositionalnystagmus,and t pu
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atypicalpositioningnystagmus.Thetestconsistsof: lis
c seatingthepatientappropriatelyonacouchsothatwhen h
Figure7 TheDix-Hallpikemanoeuvre(seetext). e
supine,theirheadwillextendovertheendofthecouch d
a
c the patient is asked to remove their spectacles and is s
driftoftheeyestowardsthesideofthelesion,interruptedby 1
warnedtheymayfeeldizzyasaresultofthetest 0
a fast component in the opposite direction. The lesion may c he is asked not to close his eyes but to keep his gaze .11
occur in the labyrinth, the vestibular nerve, or in the centredontheexaminer’sforehead 36
vestibularnucleus. c thepatient’sheadisturned30–45˚towardstheexaminer, /jn
Spontaneous nystagmus is invaluable in siting vestibular and moved rapidly into the lying position with the head np
andneurologicaldisease.Forfullassessment,thenystagmic hanging 30˚over the back of the couch (in this way the .20
responseproducedby(1)changeofeyeposition,and(2)the posteriorsemicircularcanaloftheundermostearismoved 04
presenceorabsenceofopticfixation,needstobedocumen- directlythroughitsplaneoforientation) .05
ted.NystagmusisgradedusingAlexander’slaw:ifitisonly c thepatients’eyesareobservedfornystagmusforuptoone 44
presentwhentheeyeisdeviatedtowardsthefastphaseitis minute 78
1˚; if it is also seen in the primary position it is 2˚; and if it c themanoeuvreisrepeatedforboththerightandtheleft on
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is 3˚. The vestibular lesion may only be detected with the N
removalofoptic fixationifthe lesion issmall orcompensa- Peripheral positional nystagmus (caused by BPPV) ov
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the nystagmus may be detected in the dark by ENG or c Latentperiodtoonsetofnystagmusfrom2–45seconds . D
video-oculography. c Development of torsional nystagmus with the fast phase ow
towardstheground(geotropic) n
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Gaze evoked nystagmus c Associatedvertigoandautonomicsymptoms a
d
Patientswithgazeevokednystagmusareunabletomaintain c Adaptationofvertigoandnystagmusonmaintainingthe e
d
stable conjugate eye deviation away from the primary headhangingposition fro
position. The eyes drift backwards towards the centre with c Reversalofnystagmusonreturningtotheuprightposition m
an exponentially decreasing waveform. Corrective saccades c Fatiguingofsymptomsandsignsonrepeatingthetest. h
ceovnoksteadntnlyystraegsemtutsheiseaylewainystihnethdeesdirierdectpioosnitoiofng,atzheu.sIngathzee Central positional nystagmus ttp://jn
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absenceofopticfixation,thefrequencyandslowcomponent Typically, there is no latency to the onset of nystagmus, p
.b
ofvelocitydecrease(fig6).Dysfunctionmaybesecondaryto frequently no vertigo, and no adaptation of fatigability m
alesionanywherefromthemultiplebraincentrescontrolling (table 1). The direction of nystagmus may be towards the j.c
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conjugate gaze to the neuromuscular junction. It is not uppermost ear, or may be vertical in direction. Multiple m
sclerosis, Arnold-Chiari malformation, and cerebellar vascu- o/
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lar disease may produce positional nystagmus that may be D
Table1 Comparisonofbenignparoxysmalpositional theonlysignofposteriorpathology. e
nystagmus(BPPN)andcentralpositionalnystagmus ce
m
(CPN)
b
Congenital nystagmus e
BPPN CPN The patient with congenital nystagmus rarely complains of r 3
1
Latentperiod 2–45seconds 0seconds oscillopsia,buthasacentraleyemovementabnormality.The , 2
Adaptation Within30seconds Persisting nystagmus is in the horizontal plane and may change 0
Fatigability Disappearsonrepetition Persists direction. There is a null point, which is often the head 22
Vertigo Present,sometimessevere Usuallyabsent, b
orverymild position the patient adopts for reading; the slow phase is y
Directionof Torsionalandgeotropic Any dysmorphicandmaybeexponentialasdemonstratedonthe gu
nystagmus e
ENG,andcharacteristicallythereisreversalofOKN—thatis, s
Incidence Common Rare theslowphaseofOKNdoesnotmatchthedirectionofdrum t. P
rotation. ro
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Periodic alternating nystagmus towardsthesideofthelesion.Thistestisfraughtwithfalse e
u
Periodic alternating nystagmus changes direction with a negatives. ro
changeofheadoreyeposition.Cyclelengthvariesfrom1–6 l N
minuteswithnullperiodsof2–20seconds.Theprecisesiteof Tandem gait test eu
thelesionisknown,butboththecerebellumandthecaudal ro
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brainstemhavebeenimplicated. u
When performed with the eyes open, tandem walking is rg
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compensates for chronic vestibular and proprioceptive y
This nystagmus is a rotation of the eye, beating around the c
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visual axis. The direction of beat is better specified in right- deficits. Tandem walking with the eyes closed provides a ia
left terms to avoid confusion—that is, ‘‘clockwise’’ nystag- better test of vestibular function as long as cerebellar and try
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syndrome. speed. Most normal subjects can make a minimum of 10 lis
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visual defects (when it is not associated with balance Vestibular testing 0
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symptoms)oritcandevelopweekstomonthsafterstructural Electronystagmography (ENG) 1
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brainstem disease. In the latter, patients usually show Althoughagoodexaminationofeyemovementscanbemade 6
cerebellar or pyramidal features and describe oscillopsia by direct observation, recording techniques including ENG, /jnn
whichislargelyunchangedbyheadmovements. video-oculography, and spiral coil recordings allow a more p.2
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andhasbeenreportedinanumberofophthalmalogicaland comparativepurposes. 4.0
neurologicalconditions. ENGisthesimplestandmostreadilyavailablesystemfor 5
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recordingeyemovements.Anelectrodeplacedlaterallytothe 4
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The Romberg test was described in 1846 in patients with 2
represents the change in eye position as only small angular 4
dorsal column loss as a result of tabes dorsalis. The test is movements are involved in nystagmus and the relation N
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describedaspositivewhenthereisincreasedbodyswaywith betweenvoltagechangeandeyemovementisvirtuallylinear cve
the eyes closed when the patient is standing with his feet om
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vestibular input, and proprioceptive input. With the loss of ENG can consistently record eye rotations of 0.5˚. This . D
one or more of these inputs, there will be increased o
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physiological sway. Unsteadiness on Romberg testing can n
also occur with acute vestibular deficits and with cerebellar R loa
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of past-pointing and falling—that is, in the direction of the
slow component of nystagmus. The test is performed by L j.co
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asking the patient to stand with their arms extended and
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Gait test Figure8 Internuclearophthalmoplegia(INO).Theuppertraceshows 22
themovementsoftherighteyeandthelowertraceshowsthoseofthe b
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the eyes closed, with the patient walking at normal speed arelookingoutat30˚totheleft;atc/c9theeyesareagainlooking u
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towards a fixed target and the examiner close to one side straightahead;atd/d9theeyesarelookingoutat30˚totheright.The s
for safety reasons. As with the Unterberger’s test, patients traceidentifiesaleftINOwithfailureofthelefteyetoadduct(d9)and t. P
with recent unilateral vestibular lesions tend to deviate nystagmusintheabductingrighteye(d). ro
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increased amplitude in darkness. The nystagmus is e
Standard protocol for ENG testing with rotary u
unidirectional with the largest amplitude on horizontal ro
chair gazetowardsthedirectionofthefastcomponent l N
c Calibration—eyes centred, eyes right at 30˚, eyes re- c Vestibular nuclei lesions—in darkness the amplitude of the eu
centred,eyesleft30(repeat) nystagmus may hardly alter but the velocity of the slow ros
c Gazetestingtocharacterisenystagmus: phase may be decreased. Often the nystagmus is bidirec- urg
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opticfixationinhibited) c Cerebellarlesions—thesemaybeassociatedwithpathologi- sy
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recordings required with: (i) gaze upwards at 30˚for eyes. Rebound nystagmus can also be seen, but when t p
10s,then20sinthedark;(ii)gazedown30˚for10s, cerebellar,itistransitoryandwillpersistforamaximum ub
then20sinthedark of 20 seconds. Patients with cerebellar disease may also lis
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c Visualstimuli(*usinglasertargetfor1,2and3) have difficulties in executing commands of saccadic ed
(1) Saccades—betweentwotargetsat5–30apart movements. When asked to turn their gaze laterally a
s
(2) Separateeyesaccades—recordingstakenfromeachof quicklytheyovershootthetarget. 1
the two eyes, paper speed 106normal, then follow Rotary chair testing allows measurement of the eye 0.1
protocolforgazetestingasabove 1
movement response to precise vestibular stimuli and can be 3
(3) Smooth pursuit—at 0.1, 0.2, 0.3, 0.4Hz, maximum 6
velocity40˚/s ofimmenseclinicalvalue.TheVOR(vestibulo-ocularreflex) /jn
provides a simple example of a reflex arc comprising the n
(4) OKN—fullfield,constantvelocityaroundverticalcentral p
vestibular sense organ, the primary, secondary, and tertiary .2
axis,at40˚/s,reversedirectionafter9s 0
vestibular neurones and the effector organ, the oculomotor 0
c Rotarychairtesting 4
muscle.Angularaccelerationintheplaneofthesemicircular .0
(1) Impulsive rotational testing—acceleration rise time of 5
,1stoaconstantvelocityof60˚/s canal leads to endolymph displacement in a direction 44
(2) Sinusoidal VOR testing—at 0.1, 0.2, 0.3, 0.4Hz, opposite to that of rotation and in consequence the cupula 78
maximumvelocity40˚/s of that canal deviates in the same direction as the o
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(3) VORsuppression—at0.1,0.2,0.3,0.4Hz,maximum endolymph, resulting in a change of vestibular tonus, an 2
4
velocity40˚/s excitatorystimulusbeingmatchedbyaninhibitorystimulus N
*The advantage of a laser target is that its size remains fromtheoppositeside.Asaresultthereisanimpactonthe o
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constant with distance from its source, unlike conventional pairofmusclesproducingthecompensatoryeyemovement— coem
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researchpurposes plane of the horizontal canal will produce deviation of the t.00
eyestotheleft. 4. D
VORs act during all natural head movements in life with
sensitivityislessthanthatofdirectvisualinspectionwhichis coordination with visual and cervico-ocular reflexes to ow
approximately0.1˚. provide the most appropriate eye position and eye stability nlo
The plane of the recording electrodes defines the plane a
during head movements. Vision has a powerful suppressive d
of recorded eye movement—that is, electrodes attached effect on vestibular nystagmus that can, however, be seen ed
medially and laterally to the eye will record the horizontal usingFrenzel’sglassesorVOG. fro
componentsofeyemovement,whereasthoseattachedabove m
andbelowwillrecordverticalcomponents.Asinglechannel Types of rotary chair stimuli http
EeyNeGsfrmoamchbiinteemspuomramlaretecsortdhienghsoorinztoontthael msaomveemtreancets.Tohfebtowtho c Impulsive(stepvelocity)stimuli—Constantvelocitiessuchas ://jn
40, 60, 80 or 120˚/s are attained with an abrupt n
channelENGmachinecanrecordthemovementofeacheye p
acceleration of the chair, brought to constant velocity .b
separately (fig 8), and with four channel use the technique within 1 second. This constant velocity is maintained for m
can simultaneously record the vertical movements of each upto2minuteswhilethenystagmicresponsediesaway. j.c
o
eyeaswellasthehorizontalmovements.Thepaperspeedof The chair is suddenly brought to rest with the same m
10mm/s is used although when saccadic accuracy and decelerationandthenormallimitsofnystagmusintensity o/
n
velocity are being tested, 100mm/s or even faster may be are established with normal subjects. It provides a rapid D
necessary.Calibrationisperformed,sothatastandardangle e
assessment of gain (peak slow component velocity 4 c
ofeyedeviationisrepresentedbyaknownamplitudeofpen changeinchairvelocity)andthetimeconstant(timefor em
deflection. Commonly the calibration is adjusted to obtain the slow component velocity to fall to 37% of its initial be
10mmofpendeflectionper10˚. value)ofthecanalreflex. r 3
1
c Sinusoidalstimuli—Toandfroswingingmovementsofthe , 2
Clinical relevance of ENG chair around its vertical axis are programmed with 0
2
ThemainadvantageofENGrecordingsisthatsomepatients variable stimulus parameters—that is, frequency and 2
b
demonstrate nystagmus that is only identifiable when optic amplitude. The threshold for recordable nystagmus, y
g
fixationisremoved. defined as the angular acceleration maintained for 20 u
c Peripheral vestibular disorders—unless acute, these deficits seconds that will produce nystagmus, is 0.15˚/s2 in the es
are unlikely to be associated with nystagmus in the absence of optic fixation. With optic fixation the nystag- t. P
presence of optic fixation but can reveal nystagmus of musthresholdisraisedandisnormallyabout1˚/s2.With ro
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