Transcript Calibration and Gaze testing

THE ENG BATTERY
ENG & VNG
Clinical Eye Movement Videos
Calibration
• Confirming relation between:
– Voltage/Infrared video feed
and
– Eye position
• Fixed Targets/Sinusoidal Tracking
Gaze testing
• Gaze at visual targets.
• Eye movements are recorded
– Spontaneous nystagmus
– gaze evoked nystagmus
– other extraneous movments
• Pt. asked to close there eyes without
shifting gaze.
Peripheral Gaze Nystagmus:
• strongest on gaze in
direction of beating
• never vertical
• declines quickly
(within days to a
couple of weeks)
• Alexander's Law:
1st degree Nystagmus:
present only on lat.
gaze
2nd deg: both on
center and lat. side of
beat
3rd deg: on center, and
both lateral gazes.
• Video Periph Gaze
Alexander's Law
Central Nervous System Lesions:
• Often bilateral beating
• Can have vertical beating
• declines slowly if at all
Some Central Gaze Nystagmi:
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Bilateral Horiz. Gaze (Brun's) Nystagmus:
Rebound Nystagmus:
Periodic Alternating Nystagmus:
Vertical Nystagmus:
Congenital Nystagmus:
What is Going on here?:Voluntary Nystagmus
Bilateral Horiz. Gaze (Brun's)
Nystagmus:
• in large CPA tumors.
• Gaze ipsi to lesion generates large slow
nyst, with exp. decay in slow phase.
• Gaze contra to lesion generates small fast
nyst, in opposite direction of ipsi resp.
• Video Bruns
Rebound Nystagmus:
• Cerebellar disease
• movement-generated,
decays rapidly (10-20s)
• Beats in direction of
movement
• Video Rebound
Periodic Alternating Nystagmus:
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Medullary disease.
Periodic Alternating Video
cyclic, 90 s one direction,
10 s nothing or vertical,
then 90s in other direction, 10 s down time,
and back again.
present w/ eyes open or closed.
strongest in middle of phases>>visual impairment.
Vertical Nystagmus:
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Brainstem/Cerebellar or Inf. olivary disease
Can be generated by alcohol, drugs, too.
Upbeat Video
Downbeat Video
Congenital Nystagmus:
• From fixed brain defect either genetic or
developmental in origin.
• Pendular and/or jerk-type
• Disorder of slow eye movement subsystem.
• Null points or periods.
• Convergence inhibition
• Congenital Video
Saccade Testing
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Horizontal
Vertical
Regular pattern or random
Through 20 to 30 degrees.
Saccadic Disorders:
• Occular dysmetria: CBL lesion
– akin to dysdiadochokinesia
– overshoots/undershoots
• Saccadic Slowing: basal ganglia lesion
– normal saccade for 20 deg = 188/sec
• Internuclear Ophthalmoplegia: MLF lesion
– rounded tracings
– one eye lags, smoothing curve.
– separate eye recordings to confirm INO VIDEO
Watch out for:
• Superimposed nystagmi
i) gaze nystagmus
ii) congenital nystagmus
• Drug effects: usually dysmetria
• Patient problems:
i) inattention
ii) eye blinks
iii) head movement: scalloped tracings
Tracking Tests:
• Following pendular movements
• Problems to look for
– saccadic pursuit-eyes snap repeatedly to keep up with
movement = CNS lesion
– disorganized pursuit, wandering, slow, inaccurate
tracking - CNS lesion, usually above the level of the
occulomotor nuclei
– disconjugate pursuit, eyes don't stay together in
tracking - CNS lesion
Things to look out for:
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Drug influences
Inattention: multiple, rapid gaze deviations
Head movement: depressed amplitude
superimposed nystagmus
– gaze: R, L, or bil. >> jerks at extremes
– congenital: often overlies entire tracing
Optokinetic test
• Repeated tracking of moving target, producing
nystagmatic motion.
• Disorders:
– Asymmetry: CNS lesion
diff of > 30 degs, at more than one stim rate.
– Flat / declining resp. to faster rates. brainstem lesion,
possible MS
– Inverted movement: Congenital nystagmus