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28 Cards in this Set
- Front
- Back
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Vermis
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shapes saccades
responsible for fast movements lesion in vermis --> problem w/amplitude of saccade |
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Vestibulo-Cerebellum (Flocullus & Nodulus)
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shapes slow movements
maintains equilibrium Lesion in Vestibulo-Cerebellum --> nystagmus, pursuit problems, Cogwheel Nystagmus problems with slow phase/step |
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Alexanders Law
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Congenital nystagmus
null position is in direction of slow phase |
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Congenital Nystagmus treat
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1. yolked prism w/apex pointing in direction of slow phase (base in direction of jerk)
2. Associated phoria tests to determine if asymetrical prism would work better |
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Infantile squint syndrome: 3 components
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Latent Nystagmus
Asymmetric OKN Dissociated Vertical Deviation |
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Latent Nystagmus
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Ipsilateral NOT isn't stimulated
esotropia during first 6 months eye drifts inward when covered? eye drifts to side of stimulated NOT |
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Asymetric OKN
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loss of Cortical Input
Cortex --> ipsilateral NOT can't track targets temporal |
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Dissociated Vertical Deviation
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Double hyper: both eyes go up when covered w/paddle & down when not
when one eye is occluded it goes up under the paddle |
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What are the acquired nystagmus
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Gaze Stabiliztion
Gaze holding Rebound Nystagmus Periodic Alternating Nystagmus (PAN) Vertical Nystagmus (up & downbeat) SeeSaw Nystagmus |
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Gaze Stabilization problems
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problem w/semicircular canals
Eyes drift toward impaired canal and jerk away Test using COWS (only in healthy) |
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Endpoint Nystagmus (Gaze Holding)
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Problem w/Nodulus Floculus (neural Integrator)
step/position not holding up fixate --> drifts back to Primary Position the saccades back to fixation DUI |
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Rebound Nystagmus
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Problem in Nodulus Floculus (step/position not holding)
extension of Endpoint Nystagmus jerk in opposite direction when return to primary position |
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Periodic Alternating Nystagmus (PAN)
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problem in Nodulus/Vermis
38% of Congenital nystagmus have this wave form |
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Vertical Nystagmus
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SemiCircular canal problem
(Up beat & Down beat) Freq = 3Hz Amplitude= 2 degrees Jerk nystagmus in Primary Position & increases in amplitude as eyes move in direction of fast Downbeat is serious |
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SeeSaw Nystagmus
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problem in otoliths, flocullus Nodulus
Freq= 1 Hz Amplitude = very large one eye up - intorts one eye down - extorts |
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Fixation Basics
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Tremor
Drift Small Saccades Be able to report scale of fixation problem - 10 min Arc |
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Tremor
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1/2 min Arc
Freq= 50-60 Hz |
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Drift
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6 min Arc
Velocity = 1 Arc min/sec Binocular -Corrects vergence misalignment |
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Micro Saccades
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6 min Arc
Freq= 2-5 (3) times/sec corrects monocular fixation errors - eyes are conjugate but different amplitudes yolked |
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VOR details
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latency = 10-15 msec
Velocity = 200-300 msec Freq = 4 Hz codes velocity |
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Depolarize hair cells
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Excitatory
hair follicles toward Kinocilium |
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Ophthalmostatic
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otolith (utricle & saccule)
absolute head position in space by monitoring translation acceleration & head orientation w/respect to gravity |
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Ophthalmokinetic (VOR)
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see while rotating head & body
sensitive to 1/2 degree/sec horizontal stimulated endolymph toward Ampulla Vertical Stimulated endolymph away Ampulla |
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either FEF or SC damaged
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Weakend saccade function
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both FEF & SC damaged
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no saccade
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Purely vertical Saccades
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both contra & ipsi must e stimulated
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Pursuit Stimuli
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Velocity > position
MT retinal error MST head error 20-40msec open loop 60-80 velocity for target |
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Parinaud's Syndrome
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- Lesions rostral to III
○ Vicinity of Superior Colliculi Paralysis of vertical gaze, failure of convergence (normal lateral gaze ability) |
