Introduction to Vestibular Assessment

Electronystagmography (ENG)

Lecture 9

Topics

• Types of vestibular assessment :Types of vestibular assessment :

ENGENG CDPCDP Rotation testing Rotation testing

Types of Vestibular Assessment

No single procedure can identify the site of the lesion in the vestibular system, therefore a test battery approach is the ideal one to apply

The available evaluation procedures of vestibular function:

I. ENG (Electronystagmography)

II. Computerized Dynamic Posturography (CDP)

AKA: Dynamic Platform Posturography (DPP) OR Moving Platform Moving Platform Posturography (MVP)Posturography (MVP)

III. Rotation Testing

Computerized Dynamic Posturography (CDP)

A test of postural stabilityA test of postural stability

Asses the individual’s ability to use info from the vestibular, Asses the individual’s ability to use info from the vestibular, somatosensory and visual sensory systems both singularly and somatosensory and visual sensory systems both singularly and together to coordinate motor responses to maintain center of together to coordinate motor responses to maintain center of gravity (COG) and balancegravity (COG) and balance

Pt. is placed in a variety of circumstances that compromise the Pt. is placed in a variety of circumstances that compromise the COG COG

Sensory inputs are provided by visual, vestibular and Sensory inputs are provided by visual, vestibular and somatosensory systems, and we are testing if the motor system somatosensory systems, and we are testing if the motor system can make appropriate musculoskeletal adjustments to maintain can make appropriate musculoskeletal adjustments to maintain COGCOG

Computerized Dynamic Posturography (CDP)

CDP test battery: CDP test battery:

1.1. Sensory Organization TestSensory Organization Test

2.2. Motor Control TestMotor Control Test

3.3. Adaptation TestAdaptation Test

Clinical Applications:Clinical Applications: Gives info about how well balance is maintained during challenging Gives info about how well balance is maintained during challenging

situationssituations Results with other tests of balance function helps to determine the Results with other tests of balance function helps to determine the

site of balance disordersite of balance disorder Results asses the pt’s risk for falling and guide balance Results asses the pt’s risk for falling and guide balance

rehabilitation plans rehabilitation plans

Computerized Dynamic Posturography (CDP)

The patient is placed in a standing posture on a fixed instrumented The patient is placed in a standing posture on a fixed instrumented platform platform (forceplate) (forceplate) connected to sensitive detectors, which are able connected to sensitive detectors, which are able to detect the tiny oscillations of the bodyto detect the tiny oscillations of the body

The equipment generates a sequence of standardized motions in the The equipment generates a sequence of standardized motions in the support platform in order to desequilibrate the patient's posturesupport platform in order to desequilibrate the patient's posture

The platform is contained within an enclosure which can also be used The platform is contained within an enclosure which can also be used to generate apparent visual surround motionsto generate apparent visual surround motions

The stimuli are calibrated relative to the patient's height and weightThe stimuli are calibrated relative to the patient's height and weight

A special computer software integrates all this and produces detailed A special computer software integrates all this and produces detailed graphics and reports which can then be compared with normal rangesgraphics and reports which can then be compared with normal ranges

Computerized Dynamic Posturography (CDP)

Dual support forceplate surface and visual surround coupled to a computer software program

The forceplate is supported by sensors located under the toes and heels of each foot

These sensors measures the horizontal forces, accelerations of body COG in the anteroposterior and lateral directions and the COG sway angel over time

Computerized Dynamic Posturography (CDP)

Rotation Testing

Eye movements are recorded Eye movements are recorded while the head is moving at various speedswhile the head is moving at various speeds

It provides additional information about how well the balance organs are It provides additional information about how well the balance organs are functioning, along with their connections to the eye musclesfunctioning, along with their connections to the eye muscles

Some rotation tests are computerized, some are notSome rotation tests are computerized, some are not

If its not computerized, If its not computerized, a swivel chaira swivel chair is used and the examiner simply is used and the examiner simply moves the person's head with his or her hands while observing the eye moves the person's head with his or her hands while observing the eye movementsmovements

Use the same type of Use the same type of sticky-patch electrodes sticky-patch electrodes or or gogglesgoggles used for ENG used for ENG

Kinds Of Computerized Rotational Tests

1. 1. Autohead Rotations

Pt. is asked to look at a fixed target and move his/her head back Pt. is asked to look at a fixed target and move his/her head back

and forth or up and down for short periods of timeand forth or up and down for short periods of time

2. Rotary Chair

Computerized chair that moves the pt. while he/she is seated,

For safety, a harness is worn and the head is restrained against

a headrest

Rotation Testing

Primarily been used for analyzing horizontal canal VOR (Primarily been used for analyzing horizontal canal VOR (vestibulo-ocular reflex))

Patient's eyes should move in a direction opposite to the rotation of Patient's eyes should move in a direction opposite to the rotation of the chairthe chair

The observed nystagmus is a physiologic response and is observed The observed nystagmus is a physiologic response and is observed with acceleration and deceleration of rotationwith acceleration and deceleration of rotation

Sustained rotation should results in a decline of this nystagmusSustained rotation should results in a decline of this nystagmus

The test applies multiple methods of rotations, each is designed to The test applies multiple methods of rotations, each is designed to analyze vestibular responses by observing the eye movementsanalyze vestibular responses by observing the eye movements

Rotation Testing

Clinical applications:

To diagnose patients with peripheral vestibular lesionsTo diagnose patients with peripheral vestibular lesions

To monitor patients undergoing pharmacologic vestibular To monitor patients undergoing pharmacologic vestibular ablation for Ménière syndromeablation for Ménière syndrome

Rotary Chair Testing

Electronystagmography (ENG)

What is ENG?

Electronystagmography is a battery of eye movement is a battery of eye movement tests that look for signs of vestibular dysfunction or tests that look for signs of vestibular dysfunction or neurological problems by measuring nystagmus neurological problems by measuring nystagmus

Its based on Its based on electro-oculography (EOG); a technique that a technique that objectively records eye movements by measuring the objectively records eye movements by measuring the corneoretinal potential

Why it is performed?

To diagnose a patient’s compliant of dizziness or To diagnose a patient’s compliant of dizziness or unsteadinessunsteadiness

The physician used the info provided by the ENG, along The physician used the info provided by the ENG, along with info from other clinical tests, to make a diagnosis with info from other clinical tests, to make a diagnosis

ENG Subtest Battery

1.1. Saccade TestSaccade Test

2.2. Gaze TestGaze Test

3.3. Tracking TestTracking Test

4.4. Optokinetic TestOptokinetic Test

5.5. Position TestPosition Test

6.6. Caloric Test Caloric Test

Recording Eye Movements

Corneoretinal Potentials:: a steady electrical potential a steady electrical potential between the front and back of the eyeballbetween the front and back of the eyeball

It creates electrical fields in the front of the head that It creates electrical fields in the front of the head that rotates as the eye rotates in its orbit rotates as the eye rotates in its orbit

Rotation of this electrical field produces a systematic Rotation of this electrical field produces a systematic voltage change between electrodes attached to the skin voltage change between electrodes attached to the skin on either side of the eyeon either side of the eye

How Eye Movements are Recorded ?

During ENG, eye movements are recorded and analyzed via small During ENG, eye movements are recorded and analyzed via small ElectrodesElectrodes placed on the skin around the eyes placed on the skin around the eyes

A pair of electrodes on the pt’s temples to detect the voltage on the pt’s temples to detect the voltage changes induced by the changes induced by the horizontal eye movementshorizontal eye movements of the two eyes of the two eyes togethertogether

The signal is displayed on the The signal is displayed on the horizontal channelhorizontal channel of the recording of the recording systemsystem

A second pair of electrodes above and below one of the pt’s eyes above and below one of the pt’s eyes to detect voltage changes induced by the to detect voltage changes induced by the vertical eye movementsvertical eye movements of of that eye and this signal is displayed on the that eye and this signal is displayed on the vertical channelvertical channel of the of the recording system recording system

Fifth electrode high on the forehead ( high on the forehead (reference electrodereference electrode) )

Recording by Electrode Placement

How Eye Movements are Recorded ?

Alternatively, eye movements may be recorded by:Alternatively, eye movements may be recorded by:

A. Optical Frenzel GogglesA. Optical Frenzel Goggles Has a combination of magnifying glasses and a lighting systemHas a combination of magnifying glasses and a lighting system When room lights are darkened, nystagmus can easily be seen through When room lights are darkened, nystagmus can easily be seen through

them them

OROR

B. Videonystagmography (VNG)B. Videonystagmography (VNG)   A video eye movement recording system (uses an infrared videoA video eye movement recording system (uses an infrared video

camera mounted inside goggles) camera mounted inside goggles) Eliminate vision entirelyEliminate vision entirely

Optical Frenzel Goggles

Videonystagmogrphy (VNG)

Recording Eye Movements

Effects of eye movements:

Rightward eye movements: causes upward pen deflections on the horizontal channel

Leftward eye movements: causes downward pen deflections on the horizontal channel

Upward eye movements: causes upward pen deflections on the vertical channel

Downward eye movements: causes downward pen deflections on the vertical channel

Recording Eye Movements

Other eye movements:

Oblique eye movement: causes pen deflections on both the horizontal & vertical channels

Torsional eye movement: rotations of the eye clockwise or counterclockwise – causes no pen deflections on either the horizontal or vertical channels

Equipment

The testing roomThe testing room

Eye movement recording Eye movement recording equipment equipment

Caloric stimulating Caloric stimulating equipmentequipment

Visual stimulating Visual stimulating equipment equipment

Other equipmentsOther equipments

The Testing Room

• Subject undergoes Subject undergoes various forms of various forms of stimulation and the stimulation and the ocular response is ocular response is recorded by means of recorded by means of corneorentinal corneorentinal potential and sent to potential and sent to equipment that filters equipment that filters and amplifies the and amplifies the recordings recordings

Eye Movement Recording Equipment

A. Strip-chart system

B. Computer-based system with a monitor will display the eye movements – the info is stored in the computer for later analysis

Visual Stimulating Equipment

Light-bar:

Provides visual stimuli Provides visual stimuli needed for calibration of needed for calibration of the eye movement the eye movement recording system and for recording system and for presenting ENG subtests presenting ENG subtests stimulistimuli

Caloric Stimulating Equipment

Two types:

A. Water irrigator: uses water as the irrigant

B. Air irrigator: uses air as the irrigant

Other Equipments

Examination tableExamination table OtoscopeOtoscope Frenzel’s goggles or infrared eye movement monitor Frenzel’s goggles or infrared eye movement monitor Emesis basin (for vomiting in case of motion sickness)Emesis basin (for vomiting in case of motion sickness) If using water caloric irrigator; a thermometer and If using water caloric irrigator; a thermometer and

graduated cylinder for calibrating the temperature and graduated cylinder for calibrating the temperature and water volume plus an ear cup and headlamp water volume plus an ear cup and headlamp

The Patient

Pretest instructionsPretest instructions

Clinical informationClinical information

Pretest examination Pretest examination

Pretest Instructions / Preparation

Don’t take any tranquilizers, sedatives or vestibular suppressantsDon’t take any tranquilizers, sedatives or vestibular suppressants

and alcohol for at least 48 hours before the tests and alcohol for at least 48 hours before the tests

Other medications taken for heart problems, high blood pressure, Other medications taken for heart problems, high blood pressure, diabetes, seizure prevention or other medical conditions should not diabetes, seizure prevention or other medical conditions should not be interrupted be interrupted

No tobacco or caffeine drinks on the day of the test No tobacco or caffeine drinks on the day of the test

Little or nothing to eat for the 4 hours before testingLittle or nothing to eat for the 4 hours before testing

No make-up or oil on the skin on the day of the test No make-up or oil on the skin on the day of the test

Pretest Examination

Before beginning the ENG tests, the examiner should conduct ear examination & eye movement examination

ear examination: the examiner should seek answers to the following questions:

Is there a TM perforation? Is there evidence of abnormal OE or ME anatomy? Is there an excessive amount of cerumen in the EAC? Is the EAC narrow?

Pretest Examination

Eye examination:

The examiner asks the pt. to fixate upon a forefinger held up in front The examiner asks the pt. to fixate upon a forefinger held up in front

of the pt. about 2 feet away from the pt.’s nose and moves the finger of the pt. about 2 feet away from the pt.’s nose and moves the finger away so that, as the pt. fixates upon it, his or her eyes move to away so that, as the pt. fixates upon it, his or her eyes move to extreme rightward, extreme upward , extreme leftward and extreme extreme rightward, extreme upward , extreme leftward and extreme downward positions downward positions

Then the examiner holds up both forefingers separated by a Then the examiner holds up both forefingers separated by a horizontal distance of about 2 feet and asks the pt. to look rapidly horizontal distance of about 2 feet and asks the pt. to look rapidly form one forefinger to the other form one forefinger to the other

Horizontal Calibration of ENG

The light bar is placed in The light bar is placed in the horizontal position at the horizontal position at a distance of 4 feet from a distance of 4 feet from the pt. forehead and the the pt. forehead and the pt. is asked to follow the pt. is asked to follow the visual target (target visual target (target moving back and forth in moving back and forth in a continuous motion)a continuous motion)

Computer automatically Computer automatically moves the target and moves the target and adjusts the gain of the adjusts the gain of the horizontal channelhorizontal channel

Vertical channel Vertical channel calibration is done the calibration is done the same way but with the same way but with the light bar rotated into the light bar rotated into the vertical position vertical position

Saccade Test

Evaluates the eye’s ability Evaluates the eye’s ability to rapidly shift the point of visual fixation Requires the pt. to fixate at a point for several secs, then rapidly

switch to a new point and fixate for several secs without any head movement

Looks forLooks for Nystagmus when the head is stable and upright and the when the head is stable and upright and the eyes are in a fixed position eyes are in a fixed position

Gaze Test

Tracking Test

SYN: SYN: Sinusoidal Tracking TestSinusoidal Tracking Test Examines the ocular smooth pursuit systemExamines the ocular smooth pursuit system

Measures nystagmus elicited by the repetitive stimuli movement Measures nystagmus elicited by the repetitive stimuli movement across the visual fieldacross the visual field

Optokinetic Test

Position Test

SYN: Dix-Hallpike Positional Test

Test is designed to determine if placing the pt. in different body positions causes Nystagmus

Positions:

A. SittingB. Right Dix-Hallpike maneuverC. Left Dix-Hallpike maneuverD. SupineE. Right ear downF. Left ear down down

Position Test

A. Sitting: • Pt. in the sitting position and gazing straight ahead. Eye

movements are recorded for at least 30 secs with eyes opened then with eyes closed

B. Right Dix-Hallpike Maneuver: • Pt. wears Frenzel’s goggles or an infrared video eye movement

monitor• Pt. in the sitting position with the head turned 45º to the right then

is pulled directly backward so he/she is lying supine with the head hanging over the end of the examining table

• Eye movements are recorded and visually observe by the examiner for at least 30 secs then pt. is returned to sitting positionposition

Position Test

C. Left Dix-Hallpike Maneuver: • Same as right Dix-Hallpike Maneuver except that the

head turned 45º to the left

D. Supine: • Pt. in the supine position and gazing straight ahead• Eye movements are recorded for at least 30 secs with

eyes opened then with eyes closed

Position Test

E. Right ear down• Same as the supine except that the pt. is in the right-

ear-down position

F. Left ear down • Same as the supine except that the pt. is in left-ear-

down position

Position Test

Position Test

The pt. should be told that the maneuvers may induce intermittent dizziness and its important to report the onset of dizziness

For all the tests, the tracing are inspected for the presence of nystagmus

Caloric Test

SYN: Bithermal Caloric Tests

A test of the horizontal semicircular canals and their afferent pathways

Premise of caloric testing:

both ears receive equal caloric stimuli so it should provoke an equally strong Nystagmus response on both sides

Caloric Test Position

Caloric Test

What happens?

Irrigating the EAC warms or cools the skin and TM, the Irrigating the EAC warms or cools the skin and TM, the temperature change is transmitted to the endolymph in temperature change is transmitted to the endolymph in the horizontal semicircular canals the horizontal semicircular canals

This temperature change causes induction currents in This temperature change causes induction currents in the horizontal canals simulating endolymphatic the horizontal canals simulating endolymphatic movements movements

Caloric Test

Cold Opposite• The cold irrigant provokes a response with fast phases

away from the irrigated ear

Warm Same • the warm irrigant provokes a nystagmus response with

fast phases towards the irrigated ear

• Remember COWS (cold opposite warm same))

Advantages of ENG

A crucial test in evaluating vestibular system because Nystagmus is A crucial test in evaluating vestibular system because Nystagmus is the only physical sign uniquely linked to the vestibular systemthe only physical sign uniquely linked to the vestibular system

Can detect subtle abnormalities at the BS and high levelsCan detect subtle abnormalities at the BS and high levels

The only substantial and documentable evidence of BS dysfunctionThe only substantial and documentable evidence of BS dysfunction

Provides permanent objective recordProvides permanent objective record

Disadvantages of ENG

The Caloric part of ENG does not use a true physiological stimulus (Caloric irrigation is not a natural occurrence)

Caloric test is subject to a variety of variables which are not under the examiner’s control

Examples:

Shape & size of EAC Thickness & position of TM Size of tympanic cavity Thickness of the bone & pneumatization of the pt.’s ME and mastoid