Electronystagmography Dr Supreet Singh Nayyar AFMC For more

Electronystagmography Dr. Supreet Singh Nayyar, AFMC For more ENT topics & ppts, visit www. nayyar. ENT. com 1 www. nayyar. ENT. com 28 -07 -2012

HISTORY � Rhythmical movement of eyes was known even in Ancient Greek medicine � Hippocrates, the father of medicine (460 B. C) & Galen (180 A. D) called it ‘Hippus’ which means small horse � Term ‘nystagmus’ was reserved for slow movement of the head � Berlin (1891) first attached a watch glass on the eye bulb to record nystagmus � Dodge & Clinc (1901) photographed light reflex from the eye & recorded nystagmus 2 www. nayyar. ENT. com 28 -07 -2012

VESTIBULAR REFLEX ARC � Sensory receptors: 3 cristae & 2 maculae � Afferent neuron: From the sensory cells to the vestibular nuclei � 2 nd order neurons: Vestibular nuclei to: �A) Oculomotor nuclei �B) Anterior horn cells of spinal cord �C) Cerebellar cortex �Temporal lobe cortex �Autonomic nervous system 28 -07 -2012 www. nayyar. ENT. com 3

VESTIBULO-OCULAR REFLEX � Stimulation of left ear with warm water (44ºC) � Stimulation of left labyrinth � Impulse to the VIth nerve of opposite side & IIIrd nerve of same side � Contraction of Rt LR & Lt MR leading to conjugate deviation of eyes to the right (slow phase) � Stimulation of reticular formation in brainstem � Counter the slow deviation of the eyes that jerk back to original position (fast phase) � Inhibition/facilitation: Cerebral cortex, cerebellum, reticular formation 4 www. nayyar. ENT. com 28 -07 -2012

FUNDAMENTALS OF ENG �Nystagmus �Continuous electrical processes in the retina �Electrical field created by positive corneoretinal potential �Coincides with the optical axis of the eye �Change with movement of the eye �Detected with the help of electrodes �Amplified & recorded on a running strip of paper/computer �Positive & negative deflection 5 www. nayyar. ENT. com 28 -07 -2012

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ELECTRODE LOCATIONS 7 www. nayyar. ENT. com 28 -07 -2012

ELECTRONYSTAGMOGRAPH TRACING � Depends upon the machine � Monochannel/Multichannel � Sawtoothed curve � Criteria to identify nystagmus beats � Direction of nystagmus 28 -07 -2012 www. nayyar. ENT. com 8

Pendular Nystagmus Latent Period of Caloric Response www. nayyar. ENT. com 28 -07 -2012 Oblique Nystagmus Perversion 9

Visual Fixation Suppression Divergent Dissociation 28 -07 -2012 www. nayyar. ENT. com Failure of Visual Fixation Suppression Monocular Nystagmus 10

ENG PROCEDURE � ENG Room: quiet, lightproof � Away from heavy electrical equipments � ENG Machine: single/multi -channeled � Properly grounded � Bed/table/positioning chair � Head-end raised to 30º � Calibration cross/pendulum 28 -07 -2012 www. nayyar. ENT. com 11

� 2 thermostatically controlled caloric water baths � Irrigation apparatus � Air caloric irrigator � Optokinetic stimulator 12 www. nayyar. ENT. com 28 -07 -2012

PREPARATION OF THE PATIENT � Avoid alcohol & certain drugs 48 hrs before � Examination of the ears � Cleaning the area � Patient asked to lie down � Application of the electrodes �Silver, coated with non-polarizing silver chloride �Electrolyte paste should be applied �Should be firmly applied over the skin 13 www. nayyar. ENT. com 28 -07 -2012

CALIBRATION Electrical Calibration � 200 microvolt signal produces a 10 mm deflection � Amplitude of nystagmus: in microvolts � Depends on: corneoretinal potential � Frequency & Slow phase: independent 28 -07 -2012 www. nayyar. ENT. com 14

CALIBRATION Biocalibration � By using a pendulum � Mounted in a inverted fashion � Patient follows the movement for 10 cycles 28 -07 -2012 www. nayyar. ENT. com 15

OPTOKINETIC NYSTAGMUS TEST � Evaluates the optokinetic system � Passing before the patient's eyes a series of repetitive visual stimuli � Rotating drum/moving lights on a calibration bar � Vertical black stripes on a white background � Diameter of the drum: 8 inches � Height: 12 inches � Movement elicites nystagmus � Symmetry of responses is evaluated 16 www. nayyar. ENT. com 28 -07 -2012

THE POSITIONING NYSTAGMUS TEST � Elicit BPPV nystagmus � Recording 1 st in erect position for 30 secs � Position changed rapidly to head hanging position with head turned to the right for 30 secs � Turned to the erect position & recorded for 30 secs � Repeated on the left side � Nystagmus: rotatory with predominant vertical component � Done with both eyes open/closed 17 www. nayyar. ENT. com 28 -07 -2012

THE CALORIC TEST � Position: Supine � Head end of table: Raised by 30º � Ears irrigated with warm & cold water for 40 secs each � Nystagmus noted � Interval of 8 mins between 2 successive irrigations 28 -07 -2012 www. nayyar. ENT. com 18

PENDULUM TRACKING TEST � Evaluate optokinetic function of smooth pursuit � Tracks 10 stimulus cycles � Latter 5 are evaluated � Sway: 30º visual angle � Speed: less than 50º/sec � Records: 4 types 28 -07 -2012 www. nayyar. ENT. com 19

PENDULUM TRACKING TEST � Normal: 10 jerky beats superimposed on 5 pendulum cycles � Abnormal: >10 jerky beats (Lt/Rt) on 5 cycles � A) Normal tracing � B) Central lesion � C) Grossly disorganized/ataxic tracing…Advanced central lesion 28 -07 -2012 www. nayyar. ENT. com 20

SPONTANEOUS NYSTAGMUS TEST � Supine/ caloric position � 1 min recording of eyes closed nystagmus � Eyes open & asked to look straight… 1 min recording � Latter 30 secs is considered � Number of beats to Rt & Lt are counted � Co-ordination of 2 eyes is noted � Over 70% normal individuals may show nystagmus � Normal: upto 19 beats/30 secs in any direction � Abnormal: >19 beats/30 secs in any direction � Limited localization value 21 www. nayyar. ENT. com 28 -07 -2012

SPONTANEOUS NYSTAGMUS TEST Failure of Visual Fixation Suppression Direction changing Spontaneous Nystagmus Vertical Spontaneous Nystagmus Congenital Fixation Nystagmus 28 -07 -2012 www. nayyar. ENT. com 22

GAZE TEST � Patient is asked to look 30º to the right, left, up & down � Recording in each position � Duration: 30 mins � Nystagmus on gaze deviation � Always pathological � Differenciate from fatigue nystagmus 28 -07 -2012 www. nayyar. ENT. com 23

INTERPRETATION OF GAZE TEST � No 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 24 www. nayyar. ENT. com 28 -07 -2012

POSITIONAL TEST � Static test to stimulate the otolith organs � Recording: for 1 min with eyes closed � Positions: sitting erect, supine with head turned left & right lateral, supine with head hyperextended � Non-specific evidence of vestibular disorder � Little localizing value � Significant: with eyes open/ 3 or more positions out of 7 � Positional nystagmus changing direction: CNS lesion � Factors affecting the nystagmus 25 www. nayyar. ENT. com 28 -07 -2012

Latency Benign Positional Nystagmus Central Positional Nystagmus 2 -10 sec None Adaptation Within 30 sec Persists Fatiguabilit Disappears on Persists y repetition Vertigo Persistent Absent/Mild Direction Undermost side Variable 28 -07 -2012 www. nayyar. ENT. com 26

QUANTITATIVE EVALUATION OF ENG 28 -07 -2012 www. nayyar. ENT. com 27

QUANTITATIVE EVALUATION OF ENG DURATION � Popular when nystagmus was directly observed � ENG: not a satisfactory parameter � Induced nystagmus declines over a period of time � Difficult to identify the end point accurately � Nystagmus reactions of different intensity may have same duration 28 -07 -2012 www. nayyar. ENT. com 28

QUANTITATIVE EVALUATION OF ENG Maximum Slow Phase Velocity � Widely used parameter � True representative of vestibular activity � Manual calculation: Bias 28 -07 -2012 www. nayyar. ENT. com 29

QUANTITATIVE EVALUATION OF ENG Culmination Frequency � Fq of nystagmus in culmination phase of caloric response � Simple & accurate measurement � Minimal personal error � Indicated as: No. of beats/30 sec � Midpoint: Culmination point (b/w 50 -110 sec) � Delay: Central pathology 28 -07 -2012 www. nayyar. ENT. com 30

CLAUSSEN’S BUTTERFLY CHART � Pictorial representation of caloric testing � Represented in 4 quadrants showing caloric response in each ear � Horizontal axis: represents time � Vertical axis: no. of nystagmus beats � Readings shown as normal (0), hypoactive (1) and hyperactive (2) �Normal 19 beats/ 30 sec = 0 �Hypoactive < 19 = 1 �Hyperactive >19 = 2 � Made for easier and faster interpretation 31 www. nayyar. ENT. com 28 -07 -2012

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 28 -07 -2012 www. nayyar. ENT. com 32

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DIGITAL ENG � Accurate calculation � Minimal unwanted artifacts � Good quality ENG record � Convenient TELEMETRIC � Time 7 place independent recording by patient himself � Specially developed goggles � Connected to recording device 34 www. nayyar. ENT. com 28 -07 -2012

THE ROTATORY TESTS � Concept of ‘retinal slip’ � Prevented in normal person by VOR � Rotatory test thus tests this VOR � Conducted in special chairs � !st carried out by Barany � Present method: Torsion swing chair � Asymmetry suggests vestibular pathology � Slow harmonic acceleration test 28 -07 -2012 www. nayyar. ENT. com 35

VIDEONYSTAGMOGRAPHY � Recording of eye movements by camera � Artifacts are non existent � Can record rotational nystagmus � Advantages & disadvantages over ENG 28 -07 -2012 www. nayyar. ENT. com 36

THANK YOU for more ENT ppts & topics, visit www. nayyar. ENT. com 37 www. nayyar. ENT. com 28 -07 -2012