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Electronystagmography

Electronystagmography. Dr. Supreet Singh Nayyar, AFMC For more ENT topics & ppts , visit www.nayyarENT.com. HISTORY. Rhythmical movement of eyes was known even in Ancient Greek medicine

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Electronystagmography

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  1. Electronystagmography Dr. Supreet Singh Nayyar, AFMC For more ENT topics & ppts, visit www.nayyarENT.com www.nayyarENT.com

  2. 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 www.nayyarENT.com

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

  4. 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 www.nayyarENT.com

  5. 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 www.nayyarENT.com

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  7. ELECTRODE LOCATIONS www.nayyarENT.com

  8. ELECTRONYSTAGMOGRAPH TRACING • Depends upon the machine • Monochannel/Multichannel • Sawtoothed curve • Criteria to identify nystagmus beats • Direction of nystagmus www.nayyarENT.com

  9. Pendular Nystagmus Oblique Nystagmus Latent Period of Caloric Response www.nayyarENT.com Nystagmus Perversion

  10. Visual Fixation Suppression Failure ofVisual Fixation Suppression Divergent Dissociation Monocular Nystagmus www.nayyarENT.com

  11. 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 www.nayyarENT.com

  12. 2 thermostatically controlled caloric water baths • Irrigation apparatus • Air caloric irrigator • Optokinetic stimulator www.nayyarENT.com

  13. 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 www.nayyarENT.com

  14. CALIBRATION Electrical Calibration • 200 microvolt signal produces a 10mm deflection • Amplitude of nystagmus: in microvolts • Depends on: corneoretinal potential • Frequency & Slow phase: independent www.nayyarENT.com

  15. CALIBRATION Biocalibration • By using a pendulum • Mounted in a inverted fashion • Patient follows the movement for 10 cycles www.nayyarENT.com

  16. 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 www.nayyarENT.com

  17. THE POSITIONING NYSTAGMUS TEST • Elicit BPPV nystagmus • Recording 1st 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 www.nayyarENT.com

  18. 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 www.nayyarENT.com

  19. 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 www.nayyarENT.com

  20. 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 www.nayyarENT.com

  21. SPONTANEOUS NYSTAGMUS TEST • Supine/ caloric position • 1min 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 www.nayyarENT.com

  22. SPONTANEOUS NYSTAGMUS TEST Failure of Visual Fixation Suppression Direction changing Spontaneous Nystagmus Vertical Spontaneous Nystagmus Congenital Fixation Nystagmus www.nayyarENT.com

  23. 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 www.nayyarENT.com

  24. 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 www.nayyarENT.com

  25. POSITIONAL TEST • Static test to stimulate the otolith organs • Recording: for 1min with eyes closed • Positions: sitting erect, supine, 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 www.nayyarENT.com

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  27. QUANTITATIVE EVALUATION OF ENG www.nayyarENT.com

  28. 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 www.nayyarENT.com

  29. QUANTITATIVE EVALUATION OF ENG Maximum Slow Phase Velocity • Widely used parameter • True representative of vestibular activity • Manual calculation: Bias www.nayyarENT.com

  30. 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 50-110sec) • Delay: Central pathology www.nayyarENT.com

  31. 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 www.nayyarENT.com

  32. 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 www.nayyarENT.com

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  34. DIGITAL ENGTELEMETRIC ENG • Accurate calculation • Minimal unwanted artifacts • Good quality ENG record • Convenient • Time 7 place independent recording by patient himself • Specially developed goggles • Connected to recording device www.nayyarENT.com

  35. 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 www.nayyarENT.com

  36. VIDEONYSTAGMOGRAPHY • Recording of eye movements by camera • Artifacts are non existent • Can record rotational nystagmus • Advantages & disadvantages over ENG www.nayyarENT.com

  37. THANK YOU for more ENT ppts & topics, visit www.nayyarENT.com www.nayyarENT.com

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