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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
Q

What contributes to reflexive saccadic eye movements?

A
  • supplemetary and parietal eye fields

- superior colliculus

26
Q

excitatory burst neurons

A

moves eyes towards target

27
Q

tonic neurons

A

for the final locking on and fixing on the targets

28
Q

steps of brainstem control for saccades

A

burst and tonic step then pause neurons

29
Q

pause neurons

A

inhibit burst neurons so no further movements occur

30
Q

locations of burst cells

A

horizontal: pontine paramedian reticular formation
vertical: rostral interstitial nucleus of MLF

31
Q

locations of tonic cells

A

horizontal: nucleus prepositus hypoglossi in the pons
vertical: interstitial nucleus of Cajal in the midbrain

32
Q

locations of pause cells

A

horizontal and vertical: omnipause cells of Raphe nuclei in the reticular formation

33
Q

How do you test saccades?

A

request pt visually jump from one object to another

34
Q

destructive lesion of frontal gaze center

A

transient conjugate eye deviation toward the side of the lesion, difficulty looking away from lesion

35
Q

seizure activity in frontal gaze center

A

eyes deviate away from the firing gaze center (irritation)

36
Q

stimulation of right parieto-occipital junction

A

eyes look to the right

37
Q

smooth pursuit

-horizontal pathway

A

parieto-occipital junction (Brodmann’s area 19) –> pontine nuclei (pons) –> contralateral flocculonodular lobe/vestibulocerebellum –> contalateral vestibular nuclei –> ipsilateral CN VI –> MLF –> CN III

38
Q

smooth pursuit

-vertical pathway

A

parieto-occipital junction (Brodmann’s area 19) –> pontine nuclei (pons) –> contralateral flocculonodular lobe/vestibulocerebellum –> contalateral vestibular nuclei –> CN III or CN IV

39
Q

CNs for smooth pursuit

A

horizontal: CN VI and III
vertical: CN III and IV

40
Q

left hemisphere firing during smooth pursuit

A

eyes move to the left

41
Q

optokinetic pathway

A

smooth pursuit pathway and nuclei of the accessory optic system

42
Q

for the optokinetic pathway, visual target is broken when the target reaches

A

the limit of the visual field

43
Q

optokinetic nystagmus

A

eyes make a quick move in the opposite direction

44
Q

What does the optokinetic pathway require to be intact?

A

parietooccipital eye field

45
Q

How is smooth pursuit tested?

A

patient visually tracks slow moving object

46
Q

How is otokinetic tested?

A

optokinetic tape - move tape through fingers in front of the patient
-expect to see optokinetic nystagmus

47
Q

lesion of the parietal lobe

A

causes loss of smooth pursuit movements toward the side of the lesion. No OKN when tape is moved toward the damaged lobe.

48
Q

vestibular-ocular system

-head turned right

A

-actiavtes right labyrinth –> CN VIII –> vestibular nuclei –> left CN VI –> MLF –> right CN III

49
Q

testing vestibular-ocular system

A

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
Q

comatose pt with dysfunction at level of the brainstem testing for vestibular-ocular movement

A

Doll’s eyes and ice water calorics will be absent

51
Q

internuclear opthalmoplegia (INO)

A
  • 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
Q

left CN VI nucleus lesion

A
  • can look right
  • can’t look left with either eye
  • convergence normal
53
Q

left CN VI nerve palsy

A
  • can look right
  • can’t look left with left eye, but can look left with right eye
  • no right eye nystagmus
  • convergence normal
54
Q

3 steps to near vision

A

convergence - so image is on fovea
accommodation - lens thickens so image is focused on fovea
pupillary constriction - better optical performance

55
Q

vergence pathway

A

primary visual cortex –> visual association cortex –> superior colliculus/pretectal plate/both –> oculomotor N and Edinger-Westphal for dilation

56
Q

test for vergence

A

patient focuses on a near object

57
Q

Argyll-Robertson pupil (neurosyphilis)

A

absent light reflex but pupil constricts in near reflex testing

Neuro Test 3 (11 decks)

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