7. Vng

Front 1

typical subtests of the ENG/VNG Battery

Back 1

• oculomotor and gaze stabilization
• positional and positioning
• caloric

Front 2

components of oculomotor and gaze stabilization

Back 2

• spontaneous and gaze nystagmus
• saccade
• smooth
• optokinetic

Front 3

components of positional and positioning

Back 3

• head and body positions
• dix-hallpike

Front 4

components of caloric testing

Back 4

response and fixation

Front 5

advantages of ENG/VNG (over other vestibular tests)

Back 5

• documentation of nystagmus to analyze
• examine voluntary eye movements (cerebellum)
• testing one labyrinth at a time (calorics) - help to localize site of lesion

Front 6

limitations of ENG/VNG (over other vestibular tests)

Back 6

• cannot record tracings of rotational/torsional eye movements (can only see on video)
• lack of wide range of stimulus in caloric testing
• only horizontal canal is stimulated in caloric testing
• does not provide much information on central compensation and functional balance

Front 7

a normal ENG?VNG CANNOT indicate completely normal vestibular function

Back 7

know know

Front 8

oculography

Back 8

recording of eye movement

Front 9

nystagmography

Back 9

recording or nystagmus

Front 10

How can recordings be obtained?

Back 10

electrical

infrared

video

other

Front 11

What do you look for in examination of eye movements

Back 11

horizontal

vertical

torsional (rotary)

nystagmus (strength and suppressibility)

Front 12

symptom impression and elicitation

Back 12

• perception of response similar to symptoms
• does position create symptoms?

Front 13

What does failure to recognize disconjugate eye movements result in?

Back 13

faulty measurement of eye movements because averaged signals do not accurately reflect actual movements of either eye

Front 14

for disconjugate eye movements change the standard protocol to record either...

Back 14

• movements of one eye only
• movements of both eyes independently

Front 15

what does oculomotor testing document?

Back 15

abnormalities of the oculomotor system that can confound interpretation of vestibular test results

Front 16

What anatomical system does oculomotor testing provide a "look" at?

Back 16

the several critical CNS system areas

Front 17

How can you examine eye movement?

Back 17

• visual inspection (frenzel lenses)
• electro-oculography (EOG)
• infrared oculography (IROG)

Front 18

electric oculography

Back 18

• surface measure of corneo-retinal potential (difference between the electrical potential in the cornea and the retina)

Front 19

When looking right, the potential increases in the electrode beside the (right/left) eye and decreases the (right/left) during electric oculography

Back 19

right, left

Front 20

For horizontal recording, where are electrodes placed during electric oculography?

Back 20

at the corner of the eye

Front 21

For vertical recording, the electrodes are placed where during electric oculography?

Back 21

above and below the eyes

Front 22

deficiencies of horizontal and vertical recording

Back 22

• no rotational recording
• variation due to skin conditions, position of eyes
• electrical noise/muscle artifact (eye blink - can occur w/ eyes open or closed)
• light artifact (5-10 minute response time)

Front 23

preparing the electrode site during electric oculography

Back 23

impedance is not as important as long as impedance is roughly equal

Front 24

two channel system works for most recordings providing (electric oculography)

Back 24

• conjugate eye movement confirmed
• no significant differences in vision, eye function (blindness, etc.)

Front 25

eye motion analysis during infrared oculography

Back 25

• measurement of movement of the pupil
• eyes are illuminated with infrared light
• horizontal and vertical channels, observable rotational

Front 26

how is the eye illuminated on the infrared light?

Back 26

• pupil appears as a black dot on the screen
• eyes are not reactive to infrared - can be recorded in complete darkness)
• eliminated unwanted fixation (known to suppress peripheral vestibular-generated nystagmus)

Front 27

deficiencies of infrared oculography

Back 27

• maintaining alignment of camera during motion
• loss of signal with eye closure and blink artifact
• history of lens surgery may influence accuracy
• "GOGGLE" system may require sight in both eyes
• mascara may interfere with the recording

Front 28

Back 28

ENG and VNG recordings

Front 29

principle measures during oculomotor and gaze testing

Back 29

• saccade (target acquisition)
• pursuit (target tracking)
• optokinetic (full-field tracking)
• gaze nystagmus
• spontaneous nystagmus

Front 30

the most important part of the operator is to be...

Back 30

• fully aware of the limitations of their technology
• equipped to respond to technical and patient specific problems

Front 31

procedures for calibrations

Back 31

• patient is seated 4 feet from a light bar/LCD projector
• patient follows a target (typically a little red light) +/- 15 degree off-center
• make sure that patient moves only their eyes and not their head
• system gain is adjusted so that eye movements can be recorded against a known value

Front 32

When is repeated calibration essential?

Back 32

for ENG due to changes in the electrode/skin interface over time or slight shifts in the camera system relative to the eyes

Front 33

Where does oculomotor tests evaluate eye movements originating from...

Back 33

the cerebellum

Front 34

abnormalities during oculomotor tests

Back 34

may indicate neurologic disease

Front 35

referrals for oculomotor tests should be based on...

Back 35

patient history and abnormal results

Front 36

procedure for saccade testing

Back 36

• patient is asked to follow a target that jumps quickly
• usually completed with a random pattern
• target (light) can move any where in the visual field within 30 degrees from the center
• target remains in one place anywhere from 1-4 seconds

Front 37

What do you ask the patient to avoid during saccade testing?

Back 37

head movement and not to anticipate target movements

Front 38

saccade testing clinically measures...

Back 38

• accuracy
• velocity (eye speed during movement)
• latency (difference in time from when target is presented and eyes start to move)

Front 39

What are results of saccade testing compared to?

Back 39

age wighted norms

Front 40

Back 40

normal saccade

Front 41

What is the goal of saccade eye movements?

Back 41

to fixate accurately and quickly on a new target (eye movements should be equal in amplitude and distance from one target to the next)

Front 42

abnormalities of saccade testing

Back 42

• undershoots
• overshoots
• glissades
• pulsion

Front 43

undershoots

Back 43

• hypomentria
• abnormal if saccades are consistently less than 70% of the target amplitude

Front 44

overshoots

Back 44

• hypermetria
• abnormal if saccades are consistently over 15-50% of the target amplitude

Front 45

glissades

Back 45

saccade "glides" to an end point; eye drifts toward or away from the target

Front 46

pulsion

Back 46

vertical saccades are "pulled" to the left or right

Front 47

Back 47

saccade undershoot - hypometria

Front 48

Back 48

saccade overshoot - hypermetria

Front 49

Back 49

saccade glissade

Front 50

Back 50

saccade overshoot

Front 51

how is saccade velocity measured?

Back 51

as the peak speed of eye movement when moving from one target to another

Front 52

abnormal saccade velocity

Back 52

consistency slower than 430 degrees per second for large amplitude saccades

consistent lower than 200 degrees per second for small amplitude saccades

Front 53

saccade latency

Back 53

difference in time from then target is presented and eyes start to move

Front 54

latency for random target

Back 54

150-25 msec

Front 55

latency for predictable target

Back 55

76 msec

Front 56

abnormal saccade latency

Back 56

a consistent delay of 260 or longer

Front 57

saccade morphological abnormalities

Back 57

slowing

internuclear ophthalomoplegia (MLF lesion)

Front 58

slowing morphological abnormality

Back 58

saccadic central pathways, pontine gaze centers, defects in OM system (neural centers and ON muscles), MLF lesions, myasthenia gravis, hunting tons disease

Front 59

internuclear ophthalmoplegia

Back 59

• found in MS and brainstem vascular injury
• slow saccade in adducting eye accompanied by simultaneous saccade overshoot in abducting eye

Front 60

pitfalls of saccade interpretation

Back 60

• presence of gaze/congenital nystagmus
• medical or drug effects
• patient inattention
• eye blink
• voluntary or involuntary eye movements

Front 61

what do you ask the patient to do during smooth pursuit?

Back 61

to follow a target that moves smoothly back and forth (like a pendulum)

Front 62

what is the goal of smooth pursuit?

Back 62

to maintain gaze on a moving target

Front 63

principle clinical measures during smooth pursuit

Back 63

• gain (eye velocity vs. target velocity)
• symmetry (difference between rightward and leftward scores) - asymmetric pursuit is highly suggestive of CNS lesion
• morphology

Front 64

smooth pursuit is produced and controlled where in the CNS?

Back 64

• frontal cortex
• occipito-patietal-temporal cortex
• converge at the level of the brainstem

Front 65

Back 65

smooth pursuit

Front 66

difficulties in using smooth pursuit to specify clinical abnormalities

Back 66

due to verity of factors, the diagnostic specificity supplied by pursuit findings in minimal

generally utility is to establish the presence of some CNS/oculomotor system pathology

poorly defined norms due to a high level of interdependent in the test variables of frequency, amplitude, and velocianty

Front 67

abnormalities of smooth pursuit

Back 67

disorders and factors leading to smooth pursuit abnormality include (advanced age, brainstem disorders, cerebellar disorders, cerebral cortical disturbances, drug ingestion, inattention, visual disorders)

asymmetrical pursuit (parietal lobe, frontal lobe, latent nystagmus)

Front 68

Back 68

smooth pursuit abnormalities

Front 69

asymmetrical pursuit

Back 69

spontaneous nystagmus

gaze nystagmus

Front 70

disorganized pursuit

Back 70

poor peripheral vision due to retinal degeneration

tracking is okay periodically

Front 71

pitfalls of pursuit interpretation

Back 71

• presence of gaze/congenital nystagmus
• medical or drug effects
• patient inattention
• voluntary or involuntary eye movements
• head movements (patients following target with head and eyes resulting in reduction in measured pursuit)
• high level of variability with advanced age

Front 72

optokinetic testing

Back 72

• dot pattern is moved across the patients field of view
• patient is asked to count the dots as they pass by
• performed at 20 degrees and 40 degrees

Front 73

clinical measures of optokinetic testing

Back 73

gain

symmetry

morphology

Front 74

vertical stripes can be used when testing in enclosed area such as the rotational chair (more provoking)

Back 74

know know

Front 75

Back 75

optokinetic results

Front 76

When in everyday activities does the optokinetic system start when the vestibular system fails to "keep up"?

Back 76

• during sustained head rotation
• during full field visual movement without VOR movement

Front 77

What the the greatest practical utility for optokinetic testing?

Back 77

as a mechanisms to define the oculomotor system capacity to neurally and mechanically drive the eye through nystagmus as a prelude to VOR testing

Front 78

classes of eye movements and associated features

Back 78

Front 79

gaze testing

Back 79

the patient is asked to maintain focus on a target moved and held left, right, up, down

Front 80

What is "gaze-evoked" nystagmus evidence of?

Back 80

potential CNS/oculomotor function pathology

Front 81

etiologies of gaze-evoked nystagmus

Back 81

brainstem or cerebellar disorder, ocular muscle fatigue, congenital nystagmus, normal variant, medication (nystagmus of peripheral vestibular origin is generally suppressed by gaze fixation)

Front 82

specific clinical entities of gaze testing include

Back 82

bruns nystagmus

rebound nystagmus

congenital nystagmus

Front 83

bruns nystagmus

Back 83

cerebellar lesion

asymmetrical; exponential, decreasing velocity in one direction

Front 84

rebound nystagmus

Back 84

brainstem or cerebellar disease

occurs with transition, fades with the time in position

Front 85

congenital nystagmus

Back 85

noted at birth or shortly thereafter

Front 86

Back 86

rebound nystagmus

Front 87

Back 87

bruns nystagmus

Front 88

spontaneous nystagmus test

Back 88

patient is in a sitting position

Front 89

what is spontaneous gaze nystagmus testing

Back 89

for the presence of spontaneous nystagmus with and without fixation and in extremes of horizontal and vertical gaze

Front 90

degrees of gaze elicit nystagmus

Back 90

1st degree (if only in gaze direction towards fast phase)

2nd degree (if in fast phase direction and central position)

3rd degree (if in all gaze positions)

Front 91

congenital signs

Back 91

congenital nystagmus

latent nystagmus

Front 92

central signs

Back 92

gaze rebound nystagmus

upbeat nystagmus

down beating nystagmus

saccadic nystagmus

internuclear ophthalmoplegia

see saw nystagmus

Front 93

vestibular signs

Back 93

nystagmus in pts w/ vestibular neuritis

nystagmus in pts with meniere's disease

nystagmus after gentamicin treatment

superior canal dehiscence - tullio

Front 94

fixation in the presence of measurable nystagmus and measured in

Back 94

SP (no target) / SP (target)

Front 95

What does inability to alter fixation index strings imply?

Back 95

central involvement

Front 96

fixation

Back 96

poor suppression of nystagmus in presence of fixation

Front 97

What may result from increased fixation index?

Back 97

artifactual sources affecting pursuit such as decreased visual acuity of the effects of sedating medications

Front 98

Why must spontaneous and gaze testing be performed BEFORE positional or caloric testing?

Back 98

it can produce false positive results

Front 99

What is the rule of thumb for tasking?

Back 99

if the patient has eyes closed or VNG "windows" closed, then task

Front 100

examples of tasking exercises

Back 100

count out loud by 2's, 5's, 10's

adding, subtracting

naming categories

"things you find at the beach, places you have been on vacation, your favorite books/TV shows..."

Front 101

Which tests is tasking especially important?

Back 101

position and caloric tests

Front 102

What happens when there is a failure to maintain a steady level of alertness?

Back 102

results in the nystagmus appearing and disappearing intermittently (depending on patient alertness)

nystagmus may be missed completely

Front 103

signs of central vestibular problem (pontomedullary brain stem vestibulocerebellum) when head motion or changes in head position are relative to gravity

Back 103

• positional downbeat nystagmus
• downbeat nystagmus/vertigo
• upbeat nystagmus/vertigo
• positional nystagmus without major vertigo
• positional vertigo with nystagmus

Front 104

abnormal positional findings with vestibular head motion intolerance (oscillopsia and unsteadiness of gait)

Back 104

• bilateral vestibulopathy
• ocular motor disorders (defective VOR)
• nuerovascular cross-compression ("vestibular paroxymia")
• vestibulocerebellar ataxia
• perilymphatic fistula
• post-traumatic otolith vertigo
• vestibulocerebellar intoxication (e.g., alcohol, phenytoin)

Front 105

abnormal positional findings of the vestibular nerve

Back 105

neurovascular compression ("disabling positional vertigo")

Front 106

abnormal positional findings of the peripheral labyrinth

Back 106

• BPPV
• cupula/endolymph gravity differential (buoyancy mechanism)
• positional alcohol vertigo/nystagmus
• positional "heavy water" nystagmus
• positional glycerol nystagmus
• perilymphatic fistula
• meniere's disease
• vestibular atelectasis (collapse of the walls of the ampullae and utricle)

Front 107

positions for the positional test

Back 107

• static body/head position
• supine: head left, head right, head center
• lateral: body left, body right
• perform with and without fixation (eyes open and eyes closed ) for 10 seconds each

Front 108

What are you determining for positional tests

Back 108

whether the vestibular system responds normally and symmetrically to position changes

Front 109

How does the system compensate following a vestibular lesion

Back 109

quickly in upright position (most frequent)

Front 110

nystagmus is not considered abnormal UNLESS

Back 110

• direction changes within a single head position
• magnitude is >3 degrees in major positions
• slow phase velocity is >6 degrees/sec in one position

Front 111

types of positional findings (2)

Back 111

type I: persistent and direction changing

type II: persistent and direction fixed

Front 112

possibilities for abnormal findings (type I and II) - non-localizing

Back 112

• possible peripheral or central pathologies
• failure to fixate increases the likelihood of central lesion

Front 113

directions for Dix-Hallpike

Back 113

patient is positioned on table so as to permit rapid laying down into a final position that results in the head and neck slightly extended downward

head it turned 45 degrees towards the suspected side (ipsilateral posterior semicircular canal)

patient is rapidly and smoothly moved into position

Front 114

positive finding if nystagmus (rotatory) is observed during Dix-Hallpike

Back 114

latency of 5-20 seconds

response rapidly fatigues within one minute of onset

may observe nystagmus in the reverse direction after sitting up

Front 115

What generates a response? (movement into position or final position)

Back 115

movement into position

Front 116

How can nystagmus be VISUALLY observed for Dix-Hallpike

Back 116

ENG recordings will miss rotational nystagmus (only has a vertical and horizontal recording)

VNG allows for a recording of the response - so you can document the response and go back and view it if necessary

Front 117

rotatary nystagmus towards the ground

Back 117

geotropic

Front 118

rotatary nystagmus towards the sky

Back 118

ageotropic

Front 119

What is a patient is consistent with BPPV but Hallpikes were negative?

Back 119

possible "spontaneous remission"

have the patient return is symptoms persist or return and then recheck the Hallpike

Front 120

non-classic hallpike findings

Back 120

• subjective symptoms without objective findings
• objective findings without subjective symptoms
• transient vertical nystagmus (non-rotatory)
• transient horizontal nystagmus (non-rotatary)
• persistent vertical nystagmus
• persistent horizontal nystagmus
• combinations of the above

Front 121

anterior canal BPPV (~4% of cases of BPPV)

Back 121

evoked by Hallpike on opposite side

Front 122

How can you tell between anterior and more common posterior canal involvement?

Back 122

for posterior canal: nystagmus is geotropic (beating toward earth)

for anterior canal: nystagmus is ageotropic (beating away from earth)

Front 123

How would you treat anterior canal involvement?

Back 123

do Eply or Semont on the opposite side of the evoked response

Front 124

horizontal canal BPPV (~6% of cases of BPPV)

Back 124

may be provoked by Hallpikes on either side

symptoms are more intense with affected ear down

Front 125

positive finding for horizontal canal BPPV

Back 125

have patient lie flat and move head from left to right, if geotropic nystagmus occurs with vertigo, then its positive

Front 126

How can you treat horizontal canal BPPV?

Back 126

with a "log roll" procedure

patient lies down and rolls 360 degrees in the direction away from the affected ear

Front 127

What does caloric testing measure?

Back 127

unilateral VOR

Front 128

types of calorics

Back 128

• binaural (both ears)
• bi-thermal (warm and cool irrigations)

Front 129

What does a temperature change in the ear create?

Back 129

changes the density of the endolymph

Front 130

mechanisms for changing density of endolymph

Back 130

• convection (dominant - "hot air rises")
• expansion (heated fluid expands)
• neural heating (nerve fibers fire more when heated)

Front 131

What should be done prior to caloric testing?

Back 131

otoscopy

tympanometry

Front 132

why should you do otoscopy prior to caloric testing?

Back 132

look for TM perf (may confound results)

look for cerumen impaction (removal is necessary before testing)

Front 133

What should you discuss with the patient about what they will experience?

Back 133

• explain that this will not elicit an attack
• the water (air) will run for X seconds, then cut-off.."
• you may or may not experience a spinning sensation
• either one os perfectly normal
• if you do feel dizzy, it will only last a minute or two like when you were a kid and you used to spin around
• concentrate on what i am saying, not the dizziness

Front 134

How can you reduce the chances of the patient becoming sick?

Back 134

interrupt the irrigation if nystagmus intensity exceeds a critical limit

use the same time period for other irrigations

Front 135

how is patient placed for caloric testing

Back 135

patient is placed supine with head tiled 30 degrees off horizontal (horizontal SSC is situated in the vertical plane)

Front 136

when the external canal is exposed to temperature stimuli

Back 136

• binaural, bithermal stimulus
• cool: 30 degrees C (inhibitory response)
• warm: 44 degrees C (excitatory response)
• Ice: 0 degrees C (only performed if they have no response to cool or warm)

Front 137

methods for irrigation

Back 137

• air (heated or cooled and pumped into ear)
• open loop (direct induction of water in ear)
• closed loop (latex balloon with water circulating in it)

Front 138

advantages of air method

Back 138

• cleaner (less chance of giving patient a shower)
• otoscope on front allows you to view EAC while irrigating

Front 139

disadvantages of air method

Back 139

• loud
• can be uncomfortable for patient
• more difficult to achieve transfer into ear
• in patients TM perforation nystagmus for warm irrigations may beat in the opposite direction
• requires minimal warm-up time

Front 140

advantages of open loop method

Back 140

• better transfer of energy (more robust response)
• typically more comfortable

Front 141

disadvantages of open loop method

Back 141

• messier
• response can be uncomfortable for patient
• more difficult to stabilize system
• cannot visualize EAC while irrigating
• cannot be used in pts with TM perforations or PE tubes
• must restock distilled water

Front 142

advantages of closed loop method

Back 142

most effect if patient has a TM perforation

Front 143

disadvantages of closed loop method

Back 143

• transfer of energy not as good as open loop
• ballon can fold on itself
• difficult to use in patients with narrow or curvy canals

Front 144

comparisons for caloric testing

Back 144

• comparing peak slow-phase velocity
• unilateral weakness (left vs right response)
• directional preponderance (left beating vs right beating)
• fixation suppression (eyes open vs eyes closed)

Front 145

What happens if inadequate tasking occurs during the strongest part of the caloric response?

Back 145

the peak nystagmus velocity for that irrigation will be miscalculated

Front 146

Back 146

caloric test equations

Front 147

bilateral weakness caloric response

Back 147

responses from both right and left ear (total RE <12 degrees/sec and total LE <12 degrees/sec)

Front 148

directional preponderance caloric responses

Back 148

>30%

alternative values 25% - 50%

Front 149

unilateral weakness

Back 149

>25%

alternative values 25% - 50%

Front 150

fixation index caloric response

Back 150

>60%

alternative values 50% - 60%

Front 151

hyperactive - total RE >140 degrees/sec or total LE >140 degrees/sec

Back 151

.....

Front 152

caloric test for unilateral weakness equation

Back 152

peripheral vestibular findings: WNL <28%

Front 153

caloric test for fixation suppression equation

Back 153

central finding: WNL <50%

Front 154

example of tasking for caloric testing

Back 154

give me a word in ___ category that begins with the following letter (present letters either alphabetically or randomly depending on patient)

Front 155

clinical factors for caloric irrigation

Back 155

• good irrigation
• repeat of abnormal (weak) findings
• NoteL for caloric, as well as other testing, your results may vary
• normative data can help minimize false positives due to differences in operators and equipment
• order of irrigations
• wait period between irrigations

Front 156

order of irrigations

Back 156

start with one temperature and irrigate ears int he same order for each temperature

Front 157

wait period between irrigations

Back 157

3-5 minutes after the previous caloric nystagmus ends before starting the next irrigation

Front 158

headshake nystagmus

Back 158

a dynamic test though to be a result of asymmetry of VOR

Front 159

procedure for headshake test

Back 159

patient is asked to tilt head down 30 degrees and shake back and forth as quickly as possible for 30 seconds

patient then opens eyes and any nystagmus is observed and recorded for proper documentation

Front 160

headshake test in patients with vestibular asymmetry

Back 160

intact labyrinth generating a stronger response than the lesion side

this increased activity is stored in the velocity storage mechanism

when patient stood head shaking nystagmus is the result

Front 161

head impulse test use

Back 161

used to define inadequacy of unilateral or bilateral vestibular function

Front 162

head impulse procedure

Back 162

the patients head is rapidly turned with eyes focused on a distant object

eyes will stay on object if VOR is intact

Front 163

head impulse is VOR is insufficient to maintain position against head turn

Back 163

corrective saccade