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Neuro Block 6 > Oculomotor System > Flashcards

Oculomotor System Flashcards

1
Q

Maintaining fixation of eyes on a target

A

Foveation

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2
Q

Point to point shift of fiaxation

A

Saccade

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3
Q

Continuous conjugate eye movements

A

Smooth pursuit

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4
Q

Eyes move opposite to head movement, maintains fixation on a target. Tests brainstem and cerebrum

A

Vestibular-ocular reflex movements

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5
Q

Visual system guides smooth pursuit and fast reflexive re-centering of eyes

A

Optokinetic reflex

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6
Q

Fast re-centered of eyes during/after slow eye movement

A

Nystagmus

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7
Q

Fovea is at the back of the eye, lateral (temporal) to the optic disc

A

Visual axis

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8
Q
  • parallel to the optic nerve

- the 4 rectus muscles are attached at the common tendon, aka Annulus of Zinn.

A

Orbital axis

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9
Q

Vectors for hthe 4 rectus muscle actions are defined by what

A

A line between the common tendon and the point of attachment to the eye

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10
Q

What is the only CN to exit the back of the midbrain

A

Trochlear

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11
Q

What does the trochlear nerve do as it exits the midbrain

A

Cross-crosses each other within midbrain as they exit

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12
Q

Total lesion of CN III

A

Results in Down and out sign in ipsilateral eye. Depressed and abducted due to unopposed actions. Intact functions of IV and VI nerves

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13
Q

3rd nerve palsy results in

A
  • Diplopia due to dysconjugate eye positions
  • drooping or total closure of eyelid
  • pupil dilation and loss of direct response
  • loss of accommodation
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14
Q

Signs of trochlear palsy

A
  • hypertropia and mild extortion
  • vertical diplopia
  • compensate by tilting head diagonllay down
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15
Q

Right abducens palsy

A
  • medial strabismus of right eye due to unopposed MR
  • between when viewing closer objects, worse when looking at far
  • dysconjugate eyes (diplopia) when looking toward affected side
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16
Q

For horizontal gaze

A

The VI nucleus drives activation in the contralateral III nucleus

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17
Q

Function of the VI nucleus

A

When one VI nucleus is going to abduct the ipsilateral eye, it activates contralateral III nucleus and medial rectus

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18
Q

VI nucleus projects to contralateral CNIII nucleus by sending axons across the midline, then sending up the

A

Medial longitudinal fasciculus (MLF)

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19
Q

When is the CNIII/VI nucleus activation recruited?

A

During both voluntary horizontal gaze and by reflex horizontal gaze

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20
Q

Left motor cortex and the circuitry for horizontal gaze

A

Crosses midline in pons to right PPRF, activates right VI nucleus

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21
Q

Right motor cortex and the circuitry for horizontal gaze

A

Projects down and croasses midline in pons to left PPRF, activates left VI nucleus

22
Q

What area is important for vision and just anteiror to precentral gyrus

A

Frontal eye fields: contralteral saccades

23
Q

What area of the cerebrum is important for spatial aspects to vision

A

Parietal occipito temporal area

24
Q

What is an important part of the cerebrum in the back for vision

A

Visual cortex

25
Right abducens nerve damage
- normal left gaze - Right LR rectus palsy - right eye fails to look right
26
Right abducens nucleus damage
- normal left - in right gaze, neither eye looks right - right CN 6 nucleus damaged - right CN 6 nucleus fails to activate left CN 3 nucleus
27
Right PPRF nucleus damage
- left is normal - similar to 6th nucleus damage - height eye looks right - right CN6 nucleus not activated - right CN 6 nucleus fails to activate left CN 3 nucleus, so left MR not activated
28
Damage to left MLF
- left gaze normal - for right gaze, connection from right CN 6 nucleus to left CN 3 nucleus is damaged - right LR can abduct - right CN 3 nucleus not activated - right MR not activated
29
Damage to left CN 6 nucleus and bilateral MLF damage (1.5 syndrome)
Left gaze - left CN 6 nucleus damaged - left LR fails to abduct - right CN3 nucleus not activated by damaged left CN 6 nucleus - left MR not activated - neither eyes look left Right gaze -right CN 6 nucleus cannot activate left CN 3 nucleus, so left MR not activated
30
What does head turn do to gaze?
Causes conjugate horizontal gaze opposite direction
31
Vestibular nuclei in the medulla project where
To contralateral PPRF and activate contralateral CN 6 nucleus
32
What does leftward head turn activate
Left horizontal semicircular canal
33
What does the left vestibular nucleus activate
Right PPRF and right CN 6 nucleus
34
What does the right CN 6 nucleus do once the left vestibular nucleus activates it
- activates right LR and abducts the right eye | - projects up left MLF to activate the left CN3 nucleus and left MR (conjugate gaze to left)
35
What can the vestibulo-ocular reflex be used for
To evaluate the brainstem (medulla, pons, midbrain) in an unconscious unresponsivene patient
36
In a patient with conjugate gaze palsy, the vestibulocochlear-ocular reflex testing can be used for what
Testing the integrity of the CN 6 lower motor neurons
37
What does a normal vestibuli-ocular reflex suggest in someone with a conjugate gaze palsy
-conjugate gaze palsy is the result of an UMN lesion (central hemisphere lesion instead of brainstem)
38
How do you test the vestibulo-ocular reflex?
Dolls head maneuver
39
What is the caloric test?
Putting warm or cold water in ear while patient lies supine. Warm water activates the canals on that side, cold water inhibits the canals on that side
40
Putting warm water in ear for caloric test
- activates the horizontal canals on that side - activates CN 6 nucleus - slow eye movement to the right, then nystagmus to the left.
41
Cold water in the ear with the caloric test
- inhibits the horizontal canals on that side, activates canals on the opposite side - inhibits vestibular activation of left CN6 nucleus, meanwhile CN 8 activates right CN6 nucleus - conjugate slow movement to same side - nystagmus beats to opposite side of cold water
42
What direction does nystagmus beat when warm water is added?
To same side as ear receiving warm water
43
What side does the nystagmus beat to when cold water is added to the ear?
Opposite side of cold water
44
Nystagmus and optokinetic reflex
Eyes first slow-pursuit to the right, then last to left. Whatever direction the object is moving, the nystagmus beats in the opposite direction
45
The nystagmus phase of the vestibulocochlear-ocular reflex in response to doll head to caloric testing is dependent on what
Cerebrum
46
What will happen in the VOR with an unconscious patient with a cerebral pathology?
The slow phase response will be present but the nystagmus phase will be absent, thus the COWS mnemonic does not apply
47
In VOR, if neither the slow phase nor the nystagmus is seen, then a ______ lesion is more likely
Brainstem
48
What is voluntary vertical gaze driven by
Cerebral cortex activation of III and IV nuclei (III for elevation, III and IV for depression)
49
Other than cerebral cortex activation of III and IV nuclei, what else can also drive vertical gaze?
Vertically-oriented semicircular canals and otolith organs. They talk to III and IV nuclei to move eyes vertically
50
What are the middle man regions of the vertical gazes
1. The rostral interstitial nucleus of the MLF | 2. The superior colliculi

Neuro Block 6 (8 decks)

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