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Neuro Test 3 > control of eye movement > Flashcards

control of eye movement Flashcards

1
Q

What do normal eye movements require?

A
  • head movement (vestibular info)
  • visual objects (vision)
  • eye movement and position (proprioceptive info) - LMN
  • selection of a visual target (brainstem and cortical areas)
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2
Q

gaze control systems

A
  • saccadic
  • smooth pursuit
  • vestibular-ocular
  • vergence
  • optokinetic
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3
Q

conjugate movements

A

saccadic, smooth pursuit, vestibular-ocular

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4
Q

disconjugate movement

A

vergence

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5
Q

saccadic

-function

A

rapid eye movement that brings image of object onto the fovea (jumpy)

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6
Q

smooth pursuit

-function

A

keeps a moving image centered on the fovea

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7
Q

vestibular-ocular

-function

A

holds image steady on the fovea during head movements

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8
Q

vergence

-function

A

keeps image on fovea when object is moved near

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9
Q

optokinetic

-function

A

holds images of the target steady on the retina during sustained head rotation

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10
Q

nystagmus quick phase

-function

A

directs the fovea toward the oncoming visual scene during self-rotation: resets the eyes during prolonged rotation

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11
Q

saccadic system: horizontal

-overview

A

frontal eye fields or superior colliculus –> contralateral PPRF (horizontal gaze center) –> contralateral [from original stimulus] CN VI lateral rectus + MLF –> ipsilateral [to original stimulus] CN III medial rectus

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12
Q

control mechanisms for horizontal saccadic system

  • voluntary
  • reflex
A

voluntary: frontal eye fields
reflex: superior colliculus

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13
Q

PPRF

A

paramedian pontine reticular formation = horizontal gaze center

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14
Q

CNs in horizontal saccadic system

A

contralateral CN VI

ipsilateral CN III

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15
Q

stimulation of the right frontal eye field

A

drives the eyes left

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16
Q

stimulation of the left frontal eye field

A

drives the eyes right

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17
Q

control mechanisms for vertical saccadic system

  • voluntary
  • reflex
A

voluntary: frontal eye fields
reflex: superior colliculus

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18
Q

riMLF

A

rostral interstitial nucleus of the medial longitudinal fasciculus = vertical gaze center
-near midbrain and diencephalon junction

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19
Q

cells for superior vertical gaze location

A

superior colliculus and posterior commissure

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20
Q

cells for inferior vertical gaze location

A

dorsal and medial to red nucleus

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21
Q

selective gaze palsy -can’t look up

A
  • pineal tumor

- mass pressing on superior midbrain

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22
Q

selective gaze palsy - can’t look down

A

lesions near red nucleus

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23
Q

vertical saccadic system

-overview

A

frontal eye fields/superior colliculus –> riMLF –> CN IV (down) and CN III (up)

24
Q

CNs of vertical saccadic system

A

CN VI and CN III

25
What contributes to reflexive saccadic eye movements?
- supplemetary and parietal eye fields | - superior colliculus
26
excitatory burst neurons
moves eyes towards target
27
tonic neurons
for the final locking on and fixing on the targets
28
steps of brainstem control for saccades
burst and tonic step then pause neurons
29
pause neurons
inhibit burst neurons so no further movements occur
30
locations of burst cells
horizontal: pontine paramedian reticular formation vertical: rostral interstitial nucleus of MLF
31
locations of tonic cells
horizontal: nucleus prepositus hypoglossi in the pons vertical: interstitial nucleus of Cajal in the midbrain
32
locations of pause cells
horizontal and vertical: omnipause cells of Raphe nuclei in the reticular formation
33
How do you test saccades?
request pt visually jump from one object to another
34
destructive lesion of frontal gaze center
transient conjugate eye deviation toward the side of the lesion, difficulty looking away from lesion
35
seizure activity in frontal gaze center
eyes deviate away from the firing gaze center (irritation)
36
stimulation of right parieto-occipital junction
eyes look to the right
37
smooth pursuit | -horizontal pathway
parieto-occipital junction (Brodmann's area 19) --> pontine nuclei (pons) --> contralateral flocculonodular lobe/vestibulocerebellum --> contalateral vestibular nuclei --> ipsilateral CN VI --> MLF --> CN III
38
smooth pursuit | -vertical pathway
parieto-occipital junction (Brodmann's area 19) --> pontine nuclei (pons) --> contralateral flocculonodular lobe/vestibulocerebellum --> contalateral vestibular nuclei --> CN III or CN IV
39
CNs for smooth pursuit
horizontal: CN VI and III vertical: CN III and IV
40
left hemisphere firing during smooth pursuit
eyes move to the left
41
optokinetic pathway
smooth pursuit pathway and nuclei of the accessory optic system
42
for the optokinetic pathway, visual target is broken when the target reaches
the limit of the visual field
43
optokinetic nystagmus
eyes make a quick move in the opposite direction
44
What does the optokinetic pathway require to be intact?
parietooccipital eye field
45
How is smooth pursuit tested?
patient visually tracks slow moving object
46
How is otokinetic tested?
optokinetic tape - move tape through fingers in front of the patient -expect to see optokinetic nystagmus
47
lesion of the parietal lobe
causes loss of smooth pursuit movements toward the side of the lesion. No OKN when tape is moved toward the damaged lobe.
48
vestibular-ocular system | -head turned right
-actiavtes right labyrinth --> CN VIII --> vestibular nuclei --> left CN VI --> MLF --> right CN III
49
testing vestibular-ocular system
Doll's eye maneuver - eyes move in opposite direction of head turning Ice water caloric - eye deviation toward irrigated ear with quick jerk (nystagmus) back. must be conscious to have the corrective jerk or nystagmus (COWS)
50
comatose pt with dysfunction at level of the brainstem testing for vestibular-ocular movement
Doll's eyes and ice water calorics will be absent
51
internuclear opthalmoplegia (INO)
- impaired horizontal eye movements (lesion in the MLF of pons or midbrain) - weak adduction of the affected eye - abduction nystagmus of the contralateral eye - convergence normal
52
left CN VI nucleus lesion
- can look right - can't look left with either eye - convergence normal
53
left CN VI nerve palsy
- can look right - can't look left with left eye, but can look left with right eye - no right eye nystagmus - convergence normal
54
3 steps to near vision
convergence - so image is on fovea accommodation - lens thickens so image is focused on fovea pupillary constriction - better optical performance
55
vergence pathway
primary visual cortex --> visual association cortex --> superior colliculus/pretectal plate/both --> oculomotor N and Edinger-Westphal for dilation
56
test for vergence
patient focuses on a near object
57
Argyll-Robertson pupil (neurosyphilis)
absent light reflex but pupil constricts in near reflex testing

Neuro Test 3 (11 decks)

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