Everything

Slow phase of nystagmus is what of head movement

opposite

Low velocity chair movements will create what type of phase for our eyes

Low phase because our VOR is not optimized for such low frequencies

What can cause a phase lead

anticipation of cerebellum

It starts to move the eyes ahead of the chair making it seem that there will be movement and compensate the VOR

Mechanisms involved in VOR

Mechanical response

velocity storage

adaptation

Pros for rotary chair

tests frequencies between calorics and vHIT

good for kids

good for pre and post rehab

not a lot of patient factors

If something is abnormal in rotary chair would you see it on calorics?

Yes because high frequencies are recovered first, and rotary chair tests a higher frequency

cons of rotary chair

Only tests 2 canals

not great at laterality

Rotary chair passive or active

passive

Frequencies tested during SHA

.01 - .64

Velocity storage mechanism

kicks in when constant velocity is reached

decreases perception of spinning but allows for perception to stay

Time constant

How long it takes for nystagmus to become 37% of peak SPV

What if there is a longer time constant

Likely a central finding

Means something in the brain can’t regulate nystagmus

What if the time constant is shorter

Peripheral finding

Do you want to see low gain with fixation during VOR suppression test

Yes, that means they can suppress the nystagmus (no central concerns)

Is the eye movement an immediate response to a head turn?

No (8-9 msec)

What happens to the eyes for a head turn if there is a UVL?

Eyes move with the head because the VOR does not work

Does UVL affect the VOR when turning away from the lesioned side?

UVL should not affect the VOR when moving towards the healthy side, but may have less gain (below 0.7)

Earth fixed target

Target is fixed on the wall

Head fixed target

Target moves when the head moves

overt saccades

eye movement after the head has stopped moving

covert saccades

eye correction during the head impulse

SHIMP

Patient focuses on head fixed target

Clinician quickly and abruptly turns pt head

Clinician observes for any catch up saccades

Why is there a delay in eye movement when we move their head

Takes 80 msec before we can suppress VOR

What would you expect to see during vHIT if person is abnormal

Eyes move with the target

They do not have a healthy VOR and eyes will move when the target moves

Pts without vestibular function do not have corrective saccades

Pros of vHIT

There is not much decrement in the VOR with age

vHIT can test all 6 canal function and detect mild impairments

Bilateral loss can quickly and easily be measured

Special value in testing vestibular function in children

screen potential stroke patients in the ER

Utilization in concussion protocols

Cons of vHIT

Goggle slippage

Learning curve to administer test

Early stages of development

Postural stability requires what

Synchronous integration of information sent by peripheral sensors to be received and coordinated at the cerebellum

Do we need to do CDP if the only complaint is episodic vertigo?

If we are thinking it is BPPV, probably not.

SOT

Assess ability to use each sensory input in combination or isolation during maintenance of stance

MCT

Characterization of reaction to sudden, unexpected disturbance COG or COM position

Adaptation test

Want to see if the person can learn how to keep their balance

What if a person cannot adapt during adaptation test?

Concerns of neurological disorders

Concerns of otolith dysfunction

This test measures ability to perform volitional, quiet stance during a series of six specific conditions

SOT

6 conditions of SOT

1 - eyes open, floor still, visual still

2 - eyes closed, floor still,

3 - eyes open, floor still, visual moves

4 - eyes open, floor moves, visual still

5 - eyes closed, floor moves

6 - eyes open, floor moves, visual moves

Why might a person prefer visual input

It was the most reliant system at one point

Might see this with people who have acute vestibulopathy

Vestibular dysfunction pattern

abnormal 5 and 6 or 5 alone

Visual vestibular dysfunction pattern

Abnormal on 4, 5, and 6

visual preference pattern

abnormal 3 and 6 or 6 alone

visual preference/vestibular dysfunction

abnormal 3, 5, and 6

Somatosensory/vestibular dysfunction

abnormal 2, 3, 5, and 6

Non organic pattern

abnormal 1, 2, 3, 4, but normal 5 and 6

When should CDP be implemented?

Person complaining of dysequilibrium and instability

malingering

cervicogenic dysequilibrium (i.e., head trauma)

Poor compensated vestibular injuries

Spontaneous nystagmus criteria

Anything 3 degrees or less is not significant

4-5 is noteworthy

6 or greater is clinically significant

Why must we know if there is spontaneous nystagmus in reclined position

Need to know if there is nystagmus for when we do calorics because it is in the same position

Gaze abnormalities are peripheral or central?

Both

Follow Alexander’s Law to know if it’s peripheral

Saccadic abnormalities likely of what origin?

Central

Saccadic parameters to look at

Latency

Velocity

Accuracy

Gain for smooth pursuit

eye velocity / target velocity

Symmetry vs Asymmetry during smooth pursuit

Symmetry - person can track target as it moves both ways

Asymm - Eyes can move when target moving to the right but when moving to the left they have saccadic movements

Test used for BPPV

Dix-Hallpike

Signs of BPPV (posterior canal)

Delay in nystagmus when going from seated to supine

Should see torsional or rotary nystagmus

Nystagmus should fatigue usually within 20 seconds

Sitting up should make the nystagmus go in opposite direction

Do you want to try to suppress nystagmus during positional testing?

Yes

What is considered significant nystagmus during positionals

6 degrees per second - clinically significant

4-5 - noteworthy

3 or less - insignificant (unless it supports other test findings)

What are we measuring during caloric testing

Degree of nystagmus

What is considered significant difference during calorics

20%

Fixation index

SPV with fixation / SPV without fixation

Abnormal fixation index

50% or greater

Abnormal fixation index is indicative of what

Central issue (the person is unable to suppress nystagmus)

Bilateral weakness

Less than 6 SPV is abnormal

All 4 irrigations did not create SPV of 6 d/sec

Unilateral weakness

20-25% difference between ears

One side weaker than the other

Directional preponderance

Comparing LB vs RB nystagmus

Non localizing finding

Positive number = L weaker

Negative number = R weaker

Can calorics localize side of lesion?

Yes

Does a bilateral weakness indicate complete loss of vestibular function?

No

Can calorics be the only abnormal result from a comprehensive exam?

Yes

Testing very low frequency

These are the window to the vestibular system

The eyes

Are the eyes open or closed during VNG testing

Open

Remove eyeglasses

Pretest instructions for VNG

No alcohol 48 hours prior to testing

No caffeine or tobacco 2 hours prior

Take only necessary medications

No mascara or eye make uo

Visual test battery

Gaze

Saccades

Visual pursuit/tracking

OPK

How low does the head hang during dix hallpike?

lower than the shoulder blades

What are you looking for with positional testing?

Nystagmus

What does the temperature changes do during calorics?

Changes density of endolymph on the side thats irrigated

Canal that’s tested during calorics

Lateral canal

What frequency is stimulated during calroics

Low frequency