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Neurobiology II > Eye Movements and Pupillary Control > Flashcards

Eye Movements and Pupillary Control Flashcards

1
Q

What is the primary action of lateral rectus?

A

Abduction

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2
Q

What is the primary action of medial recuts?

A

Adduction

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3
Q

What is the:
- primary action?
- action on eye in abducted position?
- action of eye in adducted position?
superior rectus?

A
  • Primary: Elevation and intorsion
  • Abducted position: Elevation
  • Adducted Position: Intorsion
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4
Q

What is the
- primary action
- action on eye in abducted position
- action of eye in adducted position
of inferior rectus?

A
  • Primary: Depression and Extorsion
  • Abducted Position: Depression
  • Adducted Position: Extorsion
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5
Q

What is the
- primary action?
- action on eye in abducted position?
- action of eye in adducted position?
superior oblique?

A
  • Primary: Intorsion and Depression
  • Abducted position: Intorsion
  • Adducted Position: Depression
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6
Q

What is the
- primary action
- action on eye in abducted position
- action of eye in adducted position
inferior oblique?

A
  • Primary: Extorsion and Elevation
  • Abducted Position: Extorsion
  • Adducted Position: Elevation
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7
Q

What movements of the eye occur around the A-P axis?

A

Intorsion & Extorsion

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8
Q

What movements of the eye occur around the horizontal axis?

A

Elevation & Depression

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9
Q

What movements of the eye occur around the vertical axis?

A

Abduction & Adduction

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10
Q

What muscles are innervated by CN III (Oculomotor Nerve)?

A
  • Medial rectus, inferior rectus, superior rectus & inferior oblique
  • Levator palebrae superioris
  • Parasympathetic input to pupil contractor and ciliary muscle
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11
Q

What muscles are innervated by CN IV (Trochlear Nerve)?

A

Superior oblique muscles

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12
Q

What muscles are innervated by CN VI (Abducens Nerve)?

A

Lateral rectus muscle

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13
Q

What constitutes the somatic motor column?

A
  • CN Nuclei (oculomotor, trochlear & abducens)
  • Hypoglossal nucleus
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14
Q

Where does the oculomotor nerve (CN III) arise from?

A
  • Oculomotor nuclei
  • Edinger- Westphal nuclei
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15
Q

What two places does the Oculomotor Nerve exit?

A
  • Upper midbrain at the level of superior colliculi and red nucleus
  • Intrapeduncular fossa
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16
Q

Where does the oculomotor nerve travel?

A
  • B/w posterior cerebral and superior cerebellar arteries
  • In subarachnoid space near the posterior communicating artery
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17
Q

What is the oculomotor nerve susceptible to?

A

Compression from aneurysms

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18
Q

Damage to the oculomotor nerve causes paralysis to what?

A
  • All ipsilateral extra ocular muscles (exceptions)
  • Ipsilateral levator palpeerde superior muscle
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19
Q

Damage to the oculomotor nerve causes paralysis to all ipisilateral extra ocular muscles except what?

A
  • Superior oblique
  • Lateral rectus
  • So eye rests in down & out position
  • Causes diplopia that worsens when looking up and medially
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20
Q

What is ptosis?

A

Eye closed unless upper lid is raised with finger (complete lesion) or drooping (partial lesion)

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21
Q

Oculomotor nerve palsy causes a loss of ipsilateral parasympathetic input which presents as what?

A

Pupil dilated and unresponsive to light

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22
Q

What are the subnuclei of the Oculomotor Nucleus? What muscles to the innervate and what side is innervated?
Focus on Edinger-Westphal & Central Caudal

A
  • Edinger-Westphal (parasympathetic) (Bilateral pupillary constrictors & ciliary muscle of lens)
  • Central caudal (Bilateral levator palpebrae superior)
  • Dorsal (ipsilateral inferior rectus)
  • Intermediate (Ipsilateral Inferior oblique)
  • Ventral (Ipsilateral medial rectus)
  • Medial (contralateral superior rectus)
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23
Q

A unilateral oculomotor nucleus lesion will not cause what?

A
  • Unilateral ptosis
  • Unilateral dilated unresponsive pupil
  • Unilateral superior rectus palsy
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24
Q

Why will a unilateral oculomotor nucleus lesion not cause unilateral ptosis, dilated unresponsive pupil, superior rectus palsy?

A
  • Bilateral levator palpebrae superior and the pupillary constrictor muscles are innervated by a shared, central nucleus
  • Unilateral lesion of the oculomotor nucleus affect both the contralateral superior rectus (contralateral innervation) and the ipsilateral superior rectus (fibers cross before exiting the nucleus)
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25
Q

Where doe the trochlear nerve (CN IV) arise from?

A

Trochlear nuclei in the lower midbrain at the level of the inferior colliculi

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26
Q

Which CN is the only CN to exit the brain dorsally?

A

CN IV Trochlear Nerve

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27
Q

What is the only CN to exit the brainstem and then cross to the opposite side?

A

Trochlear Nerve (CN IV)

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28
Q

The Trochlear (CN IV) is susceptible to what?

A

Compression from cerebellar tumors

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29
Q

Trochlear nerve (CN IV) is easily damaged by what?

A

Thin and easily damaged by shear (head trauma)

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30
Q

What does damage to the Trochlear Nerve (IV) cause?

A
  • Paralysis of superior oblique muscle
  • Eye Position: Hypertropia & Extorsion
  • Vertical diplopia
31
Q

In Trochlear Nerve Palsy how is vertical diplopia improved and how is it worsened?

A
  • Improved: With chin tuck and head tilt away from the affected eye
  • Worsens looking down & toward nose
32
Q

Where does the Abducens nerve arise from and exit?

A
  • Arise from: Abducens nuclei on the floor of 4th ventricle under the facial colliculi in the mid to lower pons
  • Exits ventrally at the pontomedullary junction
33
Q

What course does the abducens nerve take to reach the lateral rectus?

A

Long vertical course

34
Q

What is the Abducens Nerve susceptible to?

A

Downward traction injury produced by elevated ICP

35
Q

Damage to the abducens nerve causes what?

A
  • Paralysis of lateral rectus muscle
  • Horizontal diplopia
36
Q

What is the eye position of abducens nerve palsy (CN VI)?

A
  • Affected eye does not abduct normally
  • Possible estropia (eye turns in)
37
Q

How does horizontal diplopia from abducens nerve palsy worsen and improve?

A
  • Worse: gaze towards impaired side & far vision
  • Improve: near vision & when head turn towards affected eye
38
Q

What do brainstem circuits control?

A
  1. Horizontal eye movements
  2. Vertical eye movements
  3. Vergence eye movement
39
Q

What is the purpose on brainstem circuits controlling eye movements?

A
  • Eye movement of the left & right are yoked together for conjugate gaze in all directions
  • Eyes can maintain fused fixation as target move towards or away from viewer
40
Q

What are the brainstem circuits for horizontal eye movements?

A
  • Oculomotor Nucleus
  • Abducen Nucleus
  • Medial Longitudinal Fasciculus (MLF)
  • Paramedian Pontine Reticular Formation (PPRF)
41
Q

What does the oculomotor nucleus control?

A

Ipsilateral medial rectus muscle

42
Q

What does the abducens nucleus control and function as?

A
  • Controls: Ipsilateral rectus muscle
  • Functions: As horizontal gaze center (controls horizontal eye movements for both eyes directed towards the ipsilateral side)
43
Q

What is the medial longitudinal fasciculus (MLF)?

A

Pathway connecting oculomotor, trochlear, abducens & vestibular nucleiW

44
Q

The Paramedian Pontine Reticular Formation (PPRF) provides input from where?

A
  • Cortex
  • Other pathways to the abducens nucleus
45
Q

Describe the pathway for brainstem circuits for horizontal eye movement

A
  • Cortex and other brain regions
  • Right PPRF
  • Right abducens nucleus (to right lateral rectus and to left oculomotor nucleus (via left MLF))
  • to left medial rectus
46
Q

What is the result of the brainstem circuit for horizontal eye movements?

A

Right eye abducts & left eye adducts to gaze to the right

47
Q

What is ipsilateral lateral gaze palsy and what causes it?

A
  • Unable to look with either eye towards the side of the lesion
  • Caused: By lesion to either the abducens nucleus or PPRF
48
Q

What is internucleus ophthalmoplegia and what causes it?

A
  • Ipsilateral eye does not adduct fully on attempted horizontal gaze to the side opposite the lesion
  • Spared function with convergence
  • Triggers nystagmus in the opposite eye
  • Caused by: lesion to MLF
49
Q

What is one-and a half syndrome and what is caused by it?

A
  • Ipsilateral eye no horizontal movement with gaze to either eye
  • Contralateral eye has preserved abduction, but with nystagmus
  • Caused by: lesion involving MLF & abdomen nucleus (or PPRF) on the same side
50
Q

Where are structures controlling vertical eye movements located?

A
  • Midbrain
  • Rostral midbrain reticular formation
  • Pretectal area
51
Q

What are vertical eye movements closely coordinated with?

A

Movement of the upper eyelids in the same direction

52
Q

What does the ventral and dorsal portion go the midbrain control?

A
  • Ventral portion: mediates downgaze
  • Dorsal portion: mediated upgaze
53
Q

What does ventral and dorsal lesions cause?

A
  • Ventral lesions: impair downgaze
  • Dorsal lesions: impair upgaze
54
Q

What is progressive supranuclear palsy and what does it cause?

A
  • Midbrain atrophy
  • Causes impaired vertical eye movement
55
Q

What may lesions to the pons cause?

A
  • May impair horizontal gaze (abducens) but spare vertical eye movements
  • Locked in syndrome (preserved vertical eye movement used for communication)
56
Q

What muscles do convergence of the eyes?

A

Bilateral medial recti

57
Q

What muscles do divergence of the eyes?

A

Bilateral lateral recti

58
Q

Both brainstem circuits are mediated by what?

A
  • Mediated by separate neuron pools in the midbrain reticular formation
  • Influenced by descending inputs
59
Q

What does the frontal eye fields generate?

A

Saccades in the contralateral direction via connection to contralateral PPRF

60
Q

What does Parieto-occipital- temporal cortex control?

A

Smooth pursuit movements in the ipsilateral direction via connection to vestibular nuclei, cerebellum & PPRF

61
Q

What is cortical control of eye movement influenced by?

A
  • Primary visual cortex & visual association cortex
  • Basal Ganglia (modulated eye movements)
62
Q

What are right way eyes?

A
  • Eyes look away from side of weakness
  • Impaired eye movement in contralateral direction
63
Q

Lesion to what causes right way eyes?

A

Cerebral hemisphere

64
Q

What is wrong way eyes?

A

Eyes look toward the side of weakness

65
Q

How does wrong way eyes occur?

A
  • Seizures (frontal eye fields & motor association cortex)
  • Thalamic hemorrhage
  • Lesions to pons (corticospinal + PPRF or abducens nucleus)
66
Q

Describe the parasympathetic pathway for pupillary constriction

A
  • Light enter one eye
  • Projects to both optic tracts (some fibers cross at optic chiasm)
  • Synapse in pretectal area (axons both cross & remain ipsilateral)
  • Synapse on pregagnlionic parasympathetic fibers in bilateral Edinger-Westphal nuclei (axons both cross and remain ipsilateral to travel bilaterally in oculomotor nerve
  • Synapse on post ganglionic parasympathetic in the ciliary ganglia
  • Pupillary constrictor muscles
67
Q

When light shone into R eye cause:
- Direct response?
- Consensual response?

A
  • Direct response: Pupil constriction of R eye
  • Consensual response: Pupil constriction of L eye
68
Q

What is the pupillary light response in someone with an oculomotor nerve lesion?

A
  • Ipsilateral pupil may appear dilated relative to opposite eye (more obvious in light room vs dark)
  • Ipsilateral pupil shows a decreased or absent repose to light shone in either eye
69
Q

What is the pupillary light response when there is damage to afferent pathway?

A
  • Damage before optic chiasm
  • Neither eye response to light shone in ipsilateral eye
  • Both respond to light shone in contralateral eye
70
Q

When a visual object moves from far to near, input from visual cortex to the parasympathetic pathways in the midbrain result in what?

A
  • Pupillary constriction
  • Accommodation of the lens (ciliary muscle)
  • Convergence of the eyes
71
Q

Describe the sympathetic pathway for pupillary dilation

A
  • Descending sympathetic pathway for pupil dilation travels down from hypothalamic nuclei to T1-T2
  • Synapse on preganglionic sympathetic neurons in intermediolateral cell column of upper thoracic spine
  • Exit T1 & T2 nerve roots and travel around the apex of the lung to ascend in paravertebral sympathetic chain
  • Synapse on postganglion sympathetic neurons in superior cervical ganglion
  • Ascen through carotid plexus along with internal carotid artery
  • Activates pupillary dilator muscle, superior tarsal muscle (assist with upper lid elevation) & cutaneous arteries & sweat glands
72
Q

What is Horner’s Syndrome and what are the symptoms?

A
  • Caused by disruption of sympathetic pathways to eye & face

Symptoms:
- Ptosis (upper eyelid droops)
- Miosis (decreased pupil size & impaired dilation)
- Anhidrosis (decrease sweating ipsilateral face & neck)

73
Q

What are lesion locations that cause Horner’s Syndrome?

A
  • Lateral hypothalamus
  • Brainstem lesion
  • Spinal cord trauma
  • Damage to T1/T2 nerve roots (disc herniation, apical lung tumor)
  • Cavernous sinus (thrombosis, aneurysm)
  • Orbit

Neurobiology II (14 decks)

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