Electronystagmography

Dr. Supreet Singh Nayyar, AFMC

For more ENT topics & ppts, visit www.nayyarENT.com

Electronystagmography28-07-2012www.nayyarENT.com1HISTORYRhythmical movement of eyes was known even in Ancient Greek medicineHippocrates, the father of medicine (460 B.C) & Galen (180 A.D) called it Hippus which means small horseTerm nystagmus was reserved for slow movement of the headBerlin (1891) first attached a watch glass on the eye bulb to record nystagmusDodge & Clinc (1901) photographed light reflex from the eye & recorded nystagmus28-07-2012www.nayyarENT.com2VESTIBULAR REFLEX ARCSensory receptors: 3 cristae & 2 maculaeAfferent neuron: From the sensory cells to the vestibular nuclei2nd order neurons: Vestibular nuclei to:A) Oculomotor nucleiB) Anterior horn cells of spinal cordC) Cerebellar cortexTemporal lobe cortexAutonomic nervous system

28-07-2012www.nayyarENT.com3VESTIBULO-OCULAR REFLEXStimulation of left ear with warm water (44C)Stimulation of left labyrinthImpulse to the VIth nerve of opposite side & IIIrd nerve of same sideContraction of Rt LR & Lt MR leading to conjugate deviation of eyes to the right (slow phase)Stimulation of reticular formation in brainstemCounter the slow deviation of the eyes that jerk back to original position (fast phase)Inhibition/facilitation: Cerebral cortex, cerebellum, reticular formation28-07-2012www.nayyarENT.com4FUNDAMENTALS OF ENGNystagmusContinuous electrical processes in the retinaElectrical field created by positive corneoretinal potentialCoincides with the optical axis of the eyeChange with movement of the eyeDetected with the help of electrodesAmplified & recorded on a running strip of paper/computerPositive & negative deflection

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28-07-2012www.nayyarENT.com6ELECTRODE LOCATIONS

28-07-2012www.nayyarENT.com7ELECTRONYSTAGMOGRAPH TRACINGDepends upon the machine

Monochannel/Multichannel

Sawtoothed curve

Criteria to identify nystagmus beats

Direction of nystagmus

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Oblique NystagmusLatent Period of Caloric ResponsePendular NystagmusNystagmus Perversion28-07-2012www.nayyarENT.com9

Visual Fixation SuppressionFailure of Visual Fixation SuppressionDivergent DissociationMonocular Nystagmus28-07-2012www.nayyarENT.com10ENG PROCEDUREENG Room: quiet, lightproofAway from heavy electrical equipmentsENG Machine: single/multi-channeledProperly groundedBed/table/positioning chairHead-end raised to 30Calibration cross/pendulum

28-07-2012www.nayyarENT.com112 thermostatically controlled caloric water bathsIrrigation apparatusAir caloric irrigatorOptokinetic stimulator

28-07-2012www.nayyarENT.com12PREPARATION OF THE PATIENTAvoid alcohol & certain drugs 48 hrs beforeExamination of the earsCleaning the areaPatient asked to lie down

Application of the electrodesSilver, coated with non-polarizing silver chlorideElectrolyte paste should be appliedShould be firmly applied over the skin

28-07-2012www.nayyarENT.com13CALIBRATION

Electrical Calibration

200 microvolt signal produces a 10mm deflectionAmplitude of nystagmus: in microvoltsDepends on: corneoretinal potentialFrequency & Slow phase: independent28-07-2012www.nayyarENT.com14CALIBRATION

Biocalibration

By using a pendulumMounted in a inverted fashionPatient follows the movement for 10 cycles

28-07-2012www.nayyarENT.com15OPTOKINETIC NYSTAGMUS TESTEvaluates the optokinetic systemPassing before the patient's eyes a series of repetitive visual stimuliRotating drum/moving lights on a calibration barVertical black stripes on a white backgroundDiameter of the drum: 8 inchesHeight: 12 inchesMovement elicites nystagmusSymmetry of responses is evaluated28-07-2012www.nayyarENT.com16THE POSITIONING NYSTAGMUS TESTElicit BPPV nystagmusRecording 1st in erect position for 30 secsPosition changed rapidly to head hanging position with head turned to the right for 30 secs Turned to the erect position & recorded for 30 secsRepeated on the left sideNystagmus: rotatory with predominant vertical componentDone with both eyes open/closed28-07-2012www.nayyarENT.com17THE CALORIC TESTPosition: SupineHead end of table: Raised by 30Ears irrigated with warm & cold water for 40 secs each Nystagmus notedInterval of 8 mins between 2 successive irrigations28-07-2012www.nayyarENT.com18PENDULUM TRACKING TEST

Evaluate optokinetic function of smooth pursuitTracks 10 stimulus cycles Latter 5 are evaluatedSway: 30 visual angleSpeed: less than 50/secRecords: 4 types28-07-2012www.nayyarENT.com19PENDULUM TRACKING TESTNormal: 10 jerky beats superimposed on 5 pendulum cyclesAbnormal: >10 jerky beats (Lt/Rt) on 5 cycles

A) Normal tracingB) Central lesionC) Grossly disorganized/ataxic tracingAdvanced central lesion

28-07-2012www.nayyarENT.com20SPONTANEOUS NYSTAGMUS TESTSupine/ caloric position1min recording of eyes closed nystagmusEyes open & asked to look straight1 min recordingLatter 30 secs is consideredNumber of beats to Rt & Lt are countedCo-ordination of 2 eyes is notedOver 70% normal individuals may show nystagmusNormal: upto 19 beats/30 secs in any directionAbnormal: >19 beats/30 secs in any directionLimited localization value28-07-2012www.nayyarENT.com21SPONTANEOUS NYSTAGMUS TEST

Failure of Visual Fixation SuppressionDirection changing Spontaneous NystagmusCongenital Fixation NystagmusVertical Spontaneous Nystagmus28-07-2012www.nayyarENT.com22GAZE TESTPatient is asked to look 30 to the right, left, up & downRecording in each positionDuration: 30 minsNystagmus on gaze deviationAlways pathologicalDifferenciate from fatigue nystagmus

28-07-2012www.nayyarENT.com23INTERPRETATION OF GAZE TESTNo nystagmus in any position: Normal

Right beating nystagmus in right lateral position: CNS pathology (cerebellar)

Left beating nystagmus in left lateral position: CNS pathology (cerebellar)

Gradually diminishing intensity of right/left beating nystagmus: Physiological end-point nystagmus

Rebound nystagmus: Chronic cerebellar pathology

28-07-2012www.nayyarENT.com24POSITIONAL TESTStatic test to stimulate the otolith organsRecording: for 1min with eyes closedPositions: sitting erect, supine, supine with head turned left & right lateral, supine with head hyperextendedNon-specific evidence of vestibular disorder Little localizing valueSignificant: with eyes open/ 3 or more positions out of 7Positional nystagmus changing direction: CNS lesionFactors affecting the nystagmus28-07-2012www.nayyarENT.com25

28-07-2012www.nayyarENT.com26Benign Positional NystagmusCentral Positional NystagmusLatency2-10 secNoneAdaptation

Within 30 secPersistsFatiguabilityDisappears on repetitionPersistsVertigo

PersistentAbsent/MildDirectionUndermost sideVariable

QUANTITATIVE EVALUATION OF ENG28-07-2012www.nayyarENT.com27QUANTITATIVE EVALUATION OF ENGDURATION

Popular when nystagmus was directly observedENG: not a satisfactory parameterInduced nystagmus declines over a period of timeDifficult to identify the end point accuratelyNystagmus reactions of different intensity may have same duration

28-07-2012www.nayyarENT.com28QUANTITATIVE EVALUATION OF ENGMaximum Slow Phase Velocity

Widely used parameter

True representative of vestibular activity

Manual calculation: Bias

28-07-2012www.nayyarENT.com29QUANTITATIVE EVALUATION OF ENGCulmination Frequency

Fq of nystagmus in culmination phase of caloric responseSimple & accurate measurementMinimal personal errorIndicated as: No.of beats/30 secMidpoint: Culmination point (b/w 50-110sec)Delay: Central pathology

28-07-2012www.nayyarENT.com30CLAUSSENS BUTTERFLY CHARTPictorial representation of caloric testingRepresented in 4 quadrants showing caloric response in each earHorizontal axis: represents timeVertical axis: no. of nystagmus beats

Readings shown as normal (0), hypoactive (1) and hyperactive (2)Normal 19 beats/ 30 sec = 0Hypoactive < 19 = 1Hyperactive >19 = 2

Made for easier and faster interpretation

28-07-2012www.nayyarENT.com31 Normal Range Rt 44 : 22 59 beats / 30 sec Lt 44 : 23 63 beats / 30 sec Rt 30 : 24 67 beats / 30 sec Lt 30 : 27 68 beats / 30 sec

Minor & major butterfly

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28-07-2012www.nayyarENT.com33DIGITAL ENG TELEMETRIC ENGAccurate calculation

Minimal unwanted artifacts

Good quality ENG record

ConvenientTime 7 place independent recording by patient himself

Specially developed goggles

Connected to recording device28-07-2012www.nayyarENT.com34THE ROTATORY TESTSConcept of retinal slipPrevented in normal person by VORRotatory test thus tests this VORConducted in special chairs!st carried out by BaranyPresent method: Torsion swing chairAsymmetry suggests vestibular pathologySlow harmonic acceleration test

28-07-2012www.nayyarENT.com35VIDEONYSTAGMOGRAPHYRecording of eye movements by camera

Artifacts are non existent

Can record rotational nystagmus

Advantages & disadvantages over ENG

28-07-2012www.nayyarENT.com36THANK YOU for more ENT ppts & topics, visit www.nayyarENT.com

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