VNG testing Flashcards
nystagmographyy (ENG/VNG)
most common test evaluation for dizziness, vertigo or imbalance as it assesses both central and peripheral components
-allows to be recorded with either electrodes or infrared video
what are the 3 components that are included in an ENG/VNG
oculomotor evaluation, positional/positioning evaluation and caloric irrigation
what are the 4 potential outcomes from a ENG/VNG
normal, central, non-localizing and peripheral
limitations of a VNG
only telling us about the SCC function, superior vestibular nerve and the central vestibular pathway
calibration for VNG
have the patient seated upright, place the goggles on and have the patient follow the dot on the screen with their eyes only
-it will go up, down, left and right and ensure they track it
patients that may not have a good calibration include ….
dark eyes, makeup on, cataract surgery, lazy eye or glass eye
oculomotor evaluation is recording the eye movements that are modulated. this section consists of …
position maintenance (gaze holding), saccades, pursuit (tracking) and optokinetic (OPK/OKN)
all oculomotor evaluations indicate a ………
central finding however there are exceptions
position maintenance (gaze holding)
consists of central, left, right, up and down positions
-we are identifying if there is nystagmus or not
if there is nystagmus within gaze holding, this indicates …
a central finding UNLESS there is spontaneous nystagmus which then it would be non-localizing
gaze holding steps
instruct the patient that the dot will be steady then will jump to a different place on the screen, have the patient follow that dot as it moves with their eyes only
saccades
assessing the ability to track fast moving targets
-we are identifying the velocity, latency and accuracy of the nystagmus
velocity of saccades
the peak speed of eye movement
-too slow can be seen with drug interaction or drowsiness
-too fast can be seen with calibration issues or with a noisy recording
latency of saccades
the time to get on target
-prolonged is seen with uncooperative patients
-reduced is seen with technical errors or anticipation
accuracy of saccades
the accuracy on the target location
-overshooting (hypermetric)
-undershooting (hypometric)
-both over and under shooting (dysmetria)
if there is nystagmus within saccades, this indicates ….
a central finding
saccade steps
instruct the patient to follow the target with their eyes only as it will jump around randomly on the screen
pursuit (tracking)
horizontal and vertical movements with following an object
-identifying gain, phase and some include the number
gain of pursuit
the eye movement relative to the target
phase of pursuit
the symmetry between the eyes
if there is nystagmus within pursuit, this indicates a ….
central finding
-sensitive for single sided or general damage
pursuit steps
instruct the patient to follow along as the dot or light moves across the screen
-glide with it as it goes
optokinetic (OPK/OKN)
elicited by the tracking of a moving field
-identifying the symmetry and gain of the nystagmus
if there is an abnormal finding in OPK, this indicates a ….
central finding
-often correlated with pursuit
positional/positioning evaluation involve either dynamic or static movements, this consists of ….
positional (dynamic) : dix-hallpike maneuver
positioning (static) : supine head roll and potentially whole body roll
dix-hallpike maneuver
test that is aimed for diagnosing BPPV within the anterior or posterior canal
-identifying if there is torsional nystagmus present or not
dix-hallpike maneuver reasoning
the movement allows for the endolymph to drop into the otoconia therefore placing something responsible for gravity into a place where it is not supposed to be
dix-hallpike maneuver steps
-grab the patients head and shoulder
-turn the head one direction at a 45 degree angle
-rapidly take the patient down to a head hanging position and observe the eyes for torsional nystagmus
-after at least 30 seconds, raise the patient
dix-hallpike maneuver with torsional nystagmus indicates …
if upward torsional it is posterior canal BPPV
if downward torsional it is anterior canal BPPV
dix-hallpike maneuver can be modified to a ….
side laying maneuver by rapidly moving the patient from center to the side
supine head roll (center, left and right)
a test that assesses for horizontal canal BPPV by adjusting the head position when the patient is laying down
supine head roll steps
lay the patient back and put into the center, right and left head position for at least 30 seconds
in order for the nystagmus to be abnormal within the supine head roll, one of the following criteria needs to be met
-if the nystagmus changes direction with any head position
-if the nystagmus is persistent in at least 3 head positions
-if the nystagmus is intermittent in all positions
-if the nystagmus has a slow velocity speed that exceeds 6 degrees/second in any position
if there is nystagmus present in the supine head roll, this indicates …
horizontal canal BPPV AND the need to go onto the whole body roll testing
whole body roll
a test that allows us to test the inner ear without including the potential neck impact
whole body roll steps
have the patient lay on the right side and the left side as if they were going to fall asleep
-keep on each side for at least 30 seconds
calorics is the most informative part of the VNG because ….
you are able to excite only one vestibular organ while the other stays at rest
-identifying unilateral weakness, directional preponderance, fixation suppression and hyperactive/hypoactive responses
unilateral weakness (caloric paresis)
comparing the slow phase velocity (SPV) of the left ear to the SPV of the right
-comparing the strength between the two ears
directional preponderance in calorics
comparing the SPV of eye movements in the same direction
-using COWS to compare
fixation suppression in calorics
observing if the nystagmus goes away or slows down with the addition of a fixation or not
hyperactive/hypoactive responses in calorics
looking for a bilateral caloric weakness
-adding up total eye speed
temperatures for air and water (with times)
water: 30 and 44, recording for 30 seconds
air: 24 and 50, recording for a minute
expected response within calorics
COWS (cool opposite, warm same)
how to record
place patient into caloric position (supine with head elevated at 30 degrees with vision denied), determine proper temperature is turned on, place caloric into ear and start recording, after the time has completed remove and instruct patient to open their eyes, repeat on the other side with the same temperature then different temperature coming back to the first ear last
