Rotational Testing

Front 1

canals function in paired sets

Back 1

right anterior (superior) and left posterior (inferior)

right posterior (inferior) and left anterior (superior)

right horizontal and left horizontal

Front 2

The VOR is generated in response to __.

Back 2

acceleration

Front 3

the neural integrator

Back 3

converts neural signals proportional to acceleration into velocity signals used for the VOR

Front 4

categories of rotational testing

Back 4

passive rotation (patients entire body is rotated)

active rotation (patient voluntarily moves head)

Front 5

rotary chair components

Back 5

enclosure

chair

head restraint

infrared oculography

optokinetic drum

Front 6

advantages od performing oculomotor testing in the rotational chair enclosure

Back 6

• total darkness eliminated potential for visual fixation
• full field OPK testing makes suppression more difficult

Front 7

components of oculomotor testing

Back 7

spontaneous nystagmus

gaze evoked nystagmus

random saccades

horizontal smooth pursuit

optokinetic testing

Front 8

What should be performed first for interpretation?

Back 8

evaluation of gaze and/or spontaneous nystagmus

Front 9

rotational test paradigms

Back 9

sinusoidal rotation test (VOR, VVOR, Fixation)

velocity step test

Front 10

positioning for rotational testing

Back 10

• patient is securely in rotational chair
• head is restrained - ensures that head movement equals chair movement
• patient wears seatbelt and harness to ensure safety

Front 11

components of sinusoidal harmonic acceleration test

Back 11

VOR vs frequency

VVOR

VOR fixation

Front 12

What is the most widely used rotational test?

Back 12

sinusoidal harmonic acceleration

Front 13

sinusoidal harmonic acceleration

Back 13

rotation around central axis

in either direction

in a variety of speeds (frequencies)

Front 14

frequencies tested for SHA

Back 14

harmonics (multiples of each other)

each frequency is doubled the speed of the previous frequency

Front 15

clinical measures for SHA

Back 15

gain

phase

symmetry

Front 16

peak angular velocity for SHA

Back 16

60 degrees per second

Front 17

SHA note

Back 17

tasking is very important

make sure patient is alter and responsive throughout testing

Front 18

Back 18

SHA example data

Front 19

Back 19

SHA example data

Front 20

VOR gain

Back 20

amplitude of head movement compared to the amplitude eye movement

Front 21

abnormalities of VOR gain

Back 21

abnormal if 2 consecutive frequencies are out of normal range

reduced gain

• can be found at single multiple frequencies
• suggestive of dysfunction or decompensation

excessiv e gain

• rare
• suggestive of cerebellar lesion
• may result from head motion while rotating

Front 22

VOR phase

Back 22

timing of head movement compared to eye movement

"timing" relation between head motion and vestibular response

Front 23

what is phase reported in

Back 23

negative values called "phase leads"

Front 24

abnormalities of VOR phase

Back 24

• specific to vestibular pathology (non-localizing)
• increased LF phase lead (often peripheral pathology)
• decreased phase lead is uncertain, possibly central

Front 25

VOR symmetry responses to

Back 25

rightward and leftward stimulation

should be around 0

Front 26

abnormalities of VOR asymmetry

Back 26

• most common abnormal finding of SHA testing
• non-localizing finding: suggests vestibular decompensation
• correlate with directional preponderance

Front 27

abnormalities of VOR

Back 27

• reduced gain asymmetry: occur often inpatients with acute unilateral vestibular lesions
• once compensation occurs symmetry and gain will return within normal limits (with in a matter of days)
• phase may remain abnormal even after compensation occurs

Front 28

vestibular fixation test

Back 28

• patient rotated around central axis while fixating on target
• target moves at the same speed as the chair
• rotation is performed at 0.04 and 0.08 Hz at 60 degrees per second

Front 29

How is VFX measured?

Back 29

in terms of

• gain
• phase
• symmetry

Front 30

Back 30

VFX results summary

Front 31

VFX interpretation evaluates ENS ability to...

Back 31

suppress VOR with fixation (like VNG testing)

Front 32

excessive gain in VFX demonstrates...

Back 32

failure of fixation suppression suggesting potential for cerebellar dysfunction

Front 33

visual-vestibular ocular reflex (VVOR) procedure

Back 33

patient is rotated around central axis with OPK lights stationary at 0.04 and 0.08 Hz at 60 degrees per second

Front 34

vvor is an interaction between

Back 34

visual and vestibular mechanisms

Front 35

What does patient use to track during vvor?

Back 35

combination of VOR and visual pursuit

Front 36

what is vvor useful for diagnosing?

Back 36

peripheral vs central disorders

Front 37

What is indicated for patients with decreased gain in SHA testing and a normal vvor score?

Back 37

they are able to compensate for vestibular loss with a voluntary pursuit

Front 38

what should vvor be if vestibular system is compromised but oculomotor system is normal?

Back 38

vvor should be normal (nystagmus should be present)

Front 39

Back 39

vvor interpretation

Front 40

normal vvor gain

Back 40

0.8 - 1.0

Front 41

What would decreased vvor gain suggest?

Back 41

maybe a brainstem involvement (in conjunction with normal vor)

Front 42

What is increased vvor gain suggestive of?

Back 42

cerebellar involvement

note: patients with cerebellar lesions often exhibit normal VOR and OKN gains

Front 43

Back 43

SHA results summary

Front 44

Back 44

abnormal sha results summary

Front 45

step velocity test

Back 45

impulse rotation sustained in one direction for ~45 seconds - chair is then abruptly stopped

patient rotated around central axis in clockwise and counterclockwise directions at 100 degrees per second

Front 46

what does step velocity test measure?

Back 46

gain

time constant

Front 47

step velocity test...should there be nystagmus?

Back 47

yes, produced by acceleration

Front 48

what component of nystagmus is recorded for step velocity test?

Back 48

slow component

Front 49

What will happen after a period of sustained rotation with step velocity test?

Back 49

intensity of nystagmus will reduce

Front 50

time constant

Back 50

the time needed for the nystagmus to decreased to 30% of its maximum SPV

Front 51

what anatomical things are examined during step velocity test?

Back 51

the response of the horizontal canal and the velocity storage mechanism

Front 52

what is the velocity storage mechanism?

Back 52

a continuation of the neural response after the vestibular labyrinth stops responding

Front 53

nystagmus during step velocity test

Back 53

decreases more after the period of the time constant

stops completely before the end of the 4 sec rotation

Front 54

cupula time constant in humans

Back 54

4 - 7 seconds

Front 55

what does the preservation of nystagmus occur for?

Back 55

central velocity storage

Front 56

abnormal for time constant

Back 56

peak SPV of 60 degrees/second isles than 10 seconds

Front 57

abnormalities of VOR time constant

Back 57

unilateral weakness

bilateral weakness

Front 58

unilateral weakness

Back 58

reduced gain and time constants for rotations ipsilateral to pathology

Front 59

bilateral weakness

Back 59

reduced gain and time constants in both clockwise and counterclockwise directions

Front 60

Back 60

velocity step test

Front 61

advantages of rotational testing

Back 61

• precise physiologic stimulus
• accurate assessment of gain of vestibular system
• assesses compensation for vestibular pathologies
• rarely causes discomfort to patient

Front 62

disadvantages of rotational testing

Back 62

• increased time to complete entire vestibular and balance test battery
• poor ability to produce localized findings

Front 63

adaptions for rotational tests for children

Back 63

• child can sit on adult lap
• pediatric sized goggles used
• shorter testing period
• modified chair

Front 64

advanced rotational tests

Back 64

autorotation test (VAT or VORTEQ)

head-shake test

Front 65

active rotational test procedure

Back 65

• patient is fit with appropriate hardware
• asked to rotate head back and forth horizontally or vertically
• head rotation is in response to a computer generated tone that increases in frequency during a 15-18 second period
• at least three trials should be performed to increase accuracy and eliminate artifact

Front 66

advantages of rotary chair testing for active rotational test

Back 66

• equipment is less expensive
• more natural stimulus frequency
• vertical testing is practical

Front 67

frequency for active rotation test

Back 67

0.5 to 8 hz

Front 68

measures for active rotation test

Back 68

gain

phase

symmetry

Front 69

potential problems for active rotational testing

Back 69

influence of the cervico-ocular reflex

slippage of the sensory band and electrode movement in vigorous head shake