Vestib Final Exam Flashcards
What is included in the ENG test battery?
Gaze Rebound Gaze Saccades Pursuit Optokinetics Head Shake Vibration Hyperventilation Fistula Positional/Positioning Bithermal Calorics
What are the four subgroups of the test battery?
Gaze/oculomotor
Special Tests
Positional/positioning
Calorics
Why is a test battery approach used?
- Cross Check
- Results supported by other findings
- Can help confirm/refute suspicions of history
- looks at different parts of the system
- looking for nystagmus
What is the purpose of gaze testing?
- to detect nystagmus with the head in single position and the eyes: primary, horizontal right & left, up & down
- done with vision allowed and denied
What is the oculomotor - saccade test?
- Patient looks back and forth at visual targets in the horizontal plane. They will be at random distances and directions.
- The movements are examined for abnormalities.
What is the oculomotor - tracking (pursuit) test?
- The patient follows a visual target moving in the horizontal plane
- The recording is examined for abnormalities
What is the optokinetic test?
- The patient follows a series of visual targets moving to the right an then to the left. This provokes optokinetic nystagmus
- The recordings are examined for weak nystagmus in one or both directions of the moving target
What positions are included in the positional testing?
- Supine
- Supine, head right
- Supine, head left
- Right lateral
- Left lateral
Gaze - Rebound
- Nystagmus is present upon returning to center gaze from an eccentric gaze position that is held for 10 seconds
- The nystagmus beats in the opposite direction of the previously held gaze https://www.brainscape.com/study?context_pack_id=1843761&deck_id=1025151
- This is a central finding associated with cerebellar disease
Characteristics of acute unilateral lesion (of a peripheral vestibular lesion)
- never vertical
- horizontal/horizontal - rotary
- unidirectional
- linear slow phase
- always conjugate (eye movements)
- enhanced with eyes closed/vision denied
- Peripheral finding
- Intensity varies with direction of gaze
- strongest in the gaze in the direction of the fast phase
- should become centrally compensated
- decline in intensity over the following weeks and months until compensated
What does alexander’s law pertain to?
- refers to nystagmus in peripheral lesions with eyes open
What is 1st degree alexanders law?
present when nystagmus is found only on lateral gaze in direction of the fast phase
What is 2nd degree alexanders law?
present in primary direction and lateral gaze in direction of quick phase
What is 3rd degree alexanders law?
present in primary, lateral gaze in both directions
Peripheral Lesions
- Intensity decreases over time due to CNS compensation
- Eyes closed/vision denied may be present away from the side of the lesion for months and years
- Horizontal nystagmus MAY be enhanced in vertical gaze
How long do the symptoms of a 1st degree peripheral lesion last?
- 1st degree gone after a few months
How long do the symptoms of a 2nd degree peripheral lesion last?
- 2nd degree gone in a week or two
How long do the symptoms of a 3rd degree peripheral lesion last?
- 3rd degree gone in a few days
What are the characteristics of a CNS Lesion?
- horizontal, vertical, oblique or rotary
- declines slowly, if at all, over time
- does not follow alexander’s law
- is enhanced by ocular fixation
- if horizontal, will beat in both directions (right on right gaze, left on left gaze)
What is Brun’s nystagmus
- Most common CNS nystagmus - bilateral horizontal gaze nystagmus
- Decreasing velocity of slow phase and increased amplitude of nystagmus beats
When would you see a unilateral horizontal gaze nystagmus (CNS)
present eyes open
absent eyes closed (always CNS)
What is rebound nystagmus (CNS)
- Chronic disease of the cerebellar system
- No nystagmus primary position eyes open
- Gaze right > brisk right beating that wanes
- Return to center > left beating that wanes
- Then gaze left > left beating that wanes
- Return to center >now right beating that wanes
What is periodic alternating nystagmus?
- direction alternates at regular intervals
- period is constant for a given individual
may be present eyes open or eyes closed
may be congenital but more likely CNS (MS, acoustic, A-C malformation, cerebellar tumor etc.)
What could upbeating nystagmus be indicative of?
may be present in any gaze up, down or even primary
o Caused by drugs or acquired CNS
What could downbeating nystagmus be indicative of?
- strongly suggests medullary lesion if present on lateral gaze
What is vertical nystagmus
- Occurs at birth or soon after in an otherwise healthy person
- Fixed, genetic developmental brain defect
- Usually pendular
- May turn to jerk nystagmus in lateral gaze
Barbiturates, Anticonvulsants (effect on vestib testing)
- Act on the CNS
- Can stay in the system 2 days - 2 weeks
- Bilateral gaze nystagmus
- Saccadic pursuit movements
- Upbeating nystagmus
- Abolish or impair fast phase of caloric nystagmus
Antihistamines, Tranquilizers (effect on vestib testing)
- Act on the CNS
- Reduce the firing rate of vestibular nuclei neurons that receive SCC input
- May reduce nystagmus that would have otherwise been present
Alcohol (effect on vestib testing)
- Deterioration of saccadic and pursuit movements
- Positional alcohol nystagmus
What drugs can effect vestibular testing?
- barbiturates, anticonvulsants
- antihistamines and tranquilizers
Alcohol
What is Ocular Dysmetria?
- Cerebellum controls smooth integration of body muscles in agonist/antagonist relationship
- Cerebellar (or its connections) disease causes defects of limb movements
- The ocular component is dysmetria
- Hypermetric = overshoot (by 150 - 200 msec)
Saccadic Slowing
- Normal velocity: 188 deg/sec
- Basal ganglia disease may cause slowing
- The eyes can accurately reach the target but do so much slower than normal. This can be symmetric or asymmetric. CALIBRATION errors and drug use must be ruled out for accurate interpretation
Internuclear opthalmoplegia
- Rounding of one side of upper plateau
- Rounding is caused by lag of adding eye
- If you see this rounding, record from both eyes
What is the procedure for tracking?
- Patient follows target moving in horizontal plane
- Excursion about 30 degrees & speed should net exceed 40-40 degrees per second
- recording examined for abnormalities
What are some normal variations with tracking?
- Occasionally slips off fovea and corrects with a small sccade
- Two or three in a row in which they are doing it correctly because if they can get that the rest are just noise
What is abnormal variations with tracking?
- Saccadic Pursuit
- Aka “cogwheeling” - eyes fall behind the target
- Disorganized and disconjugate
- Reduced horizontal gaze capacity
- Disconjugate movement
- Brainstem localization
What are some pitfalls that can cause an inaccurate read of tracking?
- Drugs o Noise o Inattention o Head movement o Superimposed gaze nystagmus o Superimposed congenital nystagmus o (Cross check with other subtests) • If you are seeing with all test maybe it’s spontaneous
What is the optokinetic test?
o Patient eye movements are recorded with visual field moving horizontally to the right and then to the left
o Speeds increase - 10, 20, 40, 60, 80 degrees per second
What are some normal variations seen with the OPK test?
- Speed of the eyes should match speed of the stimulus up to 30 deg/sec and then may fall behind stimulus (but should still increase)
- Responses should be symmetric
What are the different positions used in positioning testing?
erect (already covered in gaze testing) supine supine, head right supine, head left right lateral (optional) left lateral (optional) Dix Hallpike - head right & left
Normal variations with positioning
- No normal have positional nystagmus with eyes open/vision allowed
- It will always be horizontal, eyes closed/vision denied
- Some do have at least 3 beats with eyes closed
- Some will be direction fixed, other will be direction changing (but never within one position)
- Some will be intermittent and some will be persistent
What are some characteristics of peripheral lesions?
- Intensity decreases over time due to CNS compensation
- 3rd degree gone in a few days
- 2nd degree gone in a week or two
- 1st degree gone after a few months
- eyes closed/vision denied may be present away from the side of lesion for moths and years
- Horizontal nystagmus MAY be enhanced in vertical gaze
Abnormal findings with fixation
usually CNS
Abnormal findings without fixation
Usually non-localizing
Results can support localizing results
ONLY peripheral findings with:
- Unilateral weakness in calorics
- BPPV - torsional nystagmus in D-H
- Positive pressure test - fistula, but remember you do not diagnose
What is the VOR?
maintains vision by generating compensatory eye movements during head motion
What test do you use to measure torsional eye movements
VNG only, can’t measure with ENG
Why do you have the client stop taking tranquilizers, sedatives & vestibular suppressants at least 48 hours before testing?
- can cause findings that mimic CNS lesion: gaze-evoked nystagmus, abnormal saccades and tracking
- can suppress vestibular responses: reduced calorics, reduced positional responses
- vestibulotoxicity
What are some sources of noise and artifact during ENG
- blinks
- electrode drift
- 60 Hz noise
What are some sources of artifact and noise in the VNG
- threshold of pupil detection
- droopy eye lids, long eyelashes, eye makeup, large pupol
- eye skin color contrast
- eye blinks
- goggle alignment
Geotropic
nystagmus that beats towards the undermost ear
ageotropic
nystagmus beats away from the undermost ear
What are the three types of pathologic nystagmus
spontaneous (present in the absence of visual stimulation)
gaze-evoked (present in specific gaze direction)
positional (present in specific head position)
What are the three classifications of nystagmus
physiologic (rotation/caloric-induced, OPK, end-point)
Pathologic (peripheral vestibular/central)
Congenital
Nystagmus present with fixation only
- abnormal and CNS
nystagmus present without fixation only
- abnormal and peripheral
Nystagmus present with and without fixation - does not increase with fixation
abnormal and central
Nystagmus present with and without fixation - increases (doubles) without fixation
abnormal and peripheral
Horizontal nystagmus that changes direction in a single head position
CNS
Horizontal nystagmus present with fixation does not increase without fixation
CNS
Horizontal nystagmus is present without fixation and less than 4 degrees/second in VNG or 6 degrees/second in ENG
Normal
Vertical nystagmus present with fixation
CNS
Vertical nystagmus present without fixation and intensity less than 7 degrees/second in VNG
normal
Three tests of oculomotor function
saccade
tracking
optokinetic
What aspects of eye movement are measured by saccade testing?
accuracy
velocity
latency
Abnormal Saccade Slowing
- CNS
Could be caused by drugs or neurodegenerative disorders
Abnormal Saccade Delay
- CNS
drugs, inattention or poor vision
interpret cautiously
Abnormal Saccade Accuracy
CNS
cerebellum or brainstem
- dysmetria (lack of coordination): consistent undershoot or overshoot
- laterpolusion (involuntary movement to one side): overshoot to one side and undershoot to the other
- occular flutter
What are some causes of artifacts in saccade testing
- bad calibration (high or low gain)
- inattention of the patient
- gaze nystagmus or eye blinks that are superimposed
- movement of head
- not measuring enough saccades for analysis
What type of lesion is indicated by abnormal tracking?
CNS
What can cause artifact in tracking and OPK
bad calibration
inattention/following instructions
head movements
mismatch between OPK and tracking
What causes artifact in gaze?
inattention
eye blinks
What is an abnormal finding with positions
Horizontal nystagmus present without fixation
Cause by an asymmetry in the peripheral or central vestibular pathway
Suppressed by fixation (reduced by 50%)
Abnormal:
- Nystagmus greater than 4 degrees/second in VNG or 6 degrees/second in ENG in AT LEAST 1 head position
- Document nystagmus even w/in normal
- Non-localizing peripheral or CNS
- Direction changing in a single head position -> CNS
When does Pan I happen
2-6 hours after drinking
When does Pan II happen
12-48 hours after drinking
What can cause artifacts in positional testing
- lack of alertness
always alert without fixation - eye blinks
- squarewave jerk nystagmus without fixation
When does dix hallpike show a problem in the right posterior canal
Sitting to supine-upbeating & right torsion
Supine to sitting- downbeating & left torsion
When does dix hallpike show a problem in the left posterior canal
Sitting to supine-upbeating & left torsion
Supine to sitting- downbeating & right torsion
When does dix hallpike show a problem in the right anterior canal?
Sitting to supine-downbeating & right torsion
Supine to sitting- upbeating & left torsion
When does dix hallpike show a problem in the left anterior canal ?
Sitting to supine-downbeating & left torsion
Supine to sitting- upbeating & right torsion
What are the parameters for water calorics?
volume - 250 ml
duration 30 sec
temp - 44/30 d C
What are the parameters for air calorics?
volume 8 liters
duration 1 min
temp 50/24 d C
What is a unilateral weakness?
difference in responses from right and left ear
- high clinical significance
What is a directional preponderance?
Relative difference in intensity between left and right beating nystagmus
- low clinical importance
What is the fixation index?
measurement of intensity of nystagmus with fixation versus without
