Videonystagmography

What does VNG stand for?

Videonystagmography

What equipment do you need for a VNG?

1. Otoscope

2. Computer to analyze data

3. Infrared goggles or skin electrodes and frenzel’s lenses

4. Patient table or chair that may be positioned into laying

5. Stimulus (light bar or television screen)

6. Bithermal caloric irrigator (air or water)

7. Proper lighting (must be able to reduce lighting)

What are 2 pieces of supplies that you should prepare before VNG?

1. Distilled water/thermometer in situation where ice calorics are necessary

2. Emesis basins to catch water or if patient becomes ill

What two situations should we prepare for before a VNG?

1. Plan for patients who become ill

2. Plan for medical emergencies

How many hours in advance should patients be given their pre-test instructions?

48 hours in advance

How many hours before the VNG do we ask patients to stop taking their non-essential medications?

48 hours in advance

What medicine do we prefer the patients to not take 48 hours before the VNG?

1. Alcoholic beverages

2. Sleeping pills

3. Tranquilizers (valium, xanax)

4. Anti-histamines

5. Anti-dizzy pills

6. Narcotics

7. Cold and allergy medications (even OTC)

What 3 medications do we encourage patients to continue taking?

1. Heart medication

2. High blood pressure medication

3. Anticonvulsant medication

What do we ask patients to stop 24 hours before the VNG?

1. Drinking coffee, tea, soda, or any other caffeinated beverages

2. Smoking or tobacco products (including nicotine patches or vaping)

How long before the VNG do we ask patients to not eat or drink anything?

3 hours before

What outfits/makeup do we ask patients to wear to the VNG?

1. No eye-makeup

2. Wear loose comfortable clothing

What will you need to do if the goggles move around during testing?

Recalibrate

What are the 7 tests that are in the VNG?

1. Spontaneous and gaze nystagmus test

2. Saccades test

3. Smooth pursuit

4. Optokinetic

5. Headshake

6. Positional tests

7. Caloric tests

Why is the room darkened?

So that visual fixation does not occur

Do some units work better if calibration is done with light and then the light is turned down for testing?

Yes

How does the audiologist control the light bar/stimulus screen?

With the computer

What is the pt instructed to do during calibration?

To look right, left, up and down

The audiologist should see square waves

If calibration is unable to be achieved, what is likely present?

A disorder is likely present

What are a few questions that we are trying to answer through the VNG?

1. Do we have a normal VNG?

2. Is this a unilateral or bilateral pathology?

3. What are our recommendations/referrals?

Is nystagmus always abnormal?

No, sometimes nystagmus

How do we test spontaneous nystagmus?

The examiner will instruct the patient to sit quietly and stare ahead, record for 30-40 seconds.

Examiner will task patient to enhance nystagmus

When do we task our patients?

Anytime fixation is denied

If spontaneous nystagmus was present earlier, will it be present in gaze nystagmus testing?

Probably

Is endpoint nystagmus clinically significant?

No

What is endpoint nystagmus?

Basically when the patient looks to a direction in the furthest direction you may see 2-3 betas of nystagmus, but it does not persist

What kind of pathologies are you dealing with if gaze nystagmus is present?

1. Central pathology or

   1. Acute peripheral pathology

What pathology will it be if vertical nystagmus is found?

Central pathology

What pathology will it be if torsional nystagmus is found?

Central pathology

What pathology will it be if nystagmus is increased when fixation is denied?

Probably an acute peripheral pathology

What is Alexander’s Law?

That horizontal nystagmus will increase in it’s intensity as the patient gazes further in the direction of the fast component of the nystagmus

This only applies to horizontal nystagmus

Typically, away from the affected ear

What will happen sometimes with irritative lesions if there is hyperfunction (rather than hypofunction)?

Sometimes the nystagmus might beat towards the side of lesion and will not follow Alexander’s law

What is rebound nystagmus?

When nystagmus is produced beating in the last direction the eye moved as the eye is returned to primary position

Is rebound nystagmus normal?

It’s normal if it’s only a beat or two but if it persists it is a central pathology indicator

What is a saccade?

A fast, jerky eye movement that shifts the gaze from one point to another

What does the patient do during saccade testing?

They track a random movement of light and follow the target closely

What do we instruct the patient to do during saccade testing?

We instruct them to follow the light as it moves and to not guess where the light is going next

What are we watching for in saccade testing?

For overshoots, undershoots, and overall poor tracking

What is the patient instructed to do in smooth pursuit testing?

To track the lights as smoothly and as accurately as possible

What does the smooth pursuit look like on the computer screen?

Like a sine wave

Lack of smooth pursuit may be a ________ sign

Central

Which test is the first test to be affected by aging and medication effects?

Smooth pursuit

What are the patient’s instructions for optokinetic testing?

To watch each light as it crosses the center

Be careful not to overexplain, patients tend to overthink this

What do we want to see during optokinetic testing?

Nystagmus! This is normal

What are 3 signs of a central pathology in optokinetic testing?

1. Inability to induce nystagmus

2. Asymmetry

3. Low gain

What is the Dix-Hallpike primarily used for?

BPPV

What does the patient do during DIx-Hallpike?

The patient is seated and lies back as quickly as possible with examiner’s help, no need to “slam” patient into that position

This is performed to the right and to the left, with the head turned 45 degrees

If there is a brief delay in nystagmus onset during DIx-Hallpike, what is this a sign of?

This is a sign of BPPV

What should we do if nystagmus is present during Dix-Halpike?

Repeat to check for fatiguability. If it is fatigueable it is most likely BPPV

What is the nystagmus fast phase and paired extra-ocular muscles for the Posterior canal?

NFP: Rotary up-beating, torsion to the side involved

PEOM: Ipsilateral superior oblique, contralateral inferior rectus

What is the nystagmus fast phase and paired extra-ocular muscles for the horizontal canal?

NFP: Horizontal geotropic-canalithiasis and ageotropic-cupulothiasis

PEOM: Ipsilateral medial rectus, contralateral lateral rectus

What is the nystagmus fast phase and paired extra-ocular muscles for the anterior canal?

NFP: Rotary down-beating, torsion to the side involved

PEOM: Ipsilateral superior rectus and contralateral inferior oblique

What is positional testing?

Placing the head and body into various positions to check for positional nystagmus

Head right, center and left

Body right and left

How long do we usually record each body/head position in positional testing?

20-30 seconds in each position, if nystagmus is noted continue testing as long as allowed by the computer

Is positional testing performed with or without fixation?

We do both, make sure to task when fixation is denied

Bithermal caloric irrigation may be performed with either _____ or _______.

air or water

What temperature should air and water be for calorics?

Air = ±14 degrees C

Water = ± 7 degrees C

About what temperature would the warm and cool air be?

Warm: 51 degrees C

Cold: 23 degrees C

What acronym do we use to remember the direction of expected nystagmus?

COWS

Cool-opposite, Warm-same

What direction would the nystagmus be if we put cool in the right?

Left beating nystagmus

What direction would the nystagmus be if we put cool in the left?

Right beating nystagmus

What direction would the nystagmus be if we put warm in the right?

Right beating nystagmus

What direction would the nystagmus be if we put warm in the left?

Left beating nystagmus

What instructions do you give your client during calorics?

“I am going to put some air in your ear for 90 seconds. You may feel a sensation of movement, that is normal and it will subside within a few minutes. Your eyes should remain open as much as possible”

What should we always do before calorics?

Otoscopy!

Do we do calorics on surgical ears?

No, unless clearance received by physician and only if using air!

What position will patients be in for bithermal caloric irrigation?

In supine position with head elevated 30 degrees

How should we observe nystagmus during bithermal caloric irrigation?

Nystagmus should be observed until a slight drop in intensity is noted, then allow fixation when still at the height of nystagmus

Patient opens eyes/goggles and stares at examiner’s finger or light in goggles, or dot on the ceiling for approximately 10 seconds

When should you task during calorics?

After removal of air/water

What is caloric irrigation considered the gold standard for?

For assessing the horizontal SCC, VOR, and each ear’s output separately

What do the results of caloric irrigation look like?

1. Computer generates a number in degrees per second (eye speed) for each of the four irrigations

2. Calculate total eye speed by adding up all four numbers

3. How much is right ear contributing?

4. How much is left ear contributing?

How much should the left and right ear be contributing in calorics?

They should contribute equally, 50/50

How can we tell if there is a unilateral weakness in calorics?

If one is contributing significantly less than the other.

Typically, a significant difference is 20-25% or greater

What is the 20-25% difference in an ear usually indicative of?

Of a peripheral weakness

What is directional preponderance?

When beating in one direction is significantly stronger than the other

Greater than 27 degrees may be significant

What can directional preponderance be an indication of?

It can be an indication of a central pathology or non-localizing

What is another central indication?

Symmetrical caloric with central signs throughout VNG battery