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Neuroanatomy > Exam #2: Cranial Nerve II > Flashcards

Exam #2: Cranial Nerve II Flashcards

1
Q

What are the functional components of CN III?

A
  • GSE= skeletal motor to upper eyelid & extraocular muscles
  • GVE= PNS to smooth muscles of the eye
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2
Q

What skeletal muscles are innervated by CN III i.e. what muscles are innervated by the GVE portion of CN III? What is the mnemonic to help remember these?

A
  • Levator palpebrae superioris
  • Superior rectus
  • Medial rectus
  • Inferior rectus
  • Inferior oblique

*SO4LR6

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3
Q

What smooth muscles are innervated by the PNS division of CN III? What are their functions?

A
  • Sphincter pupillae m.= constriction of the pupil

- Ciliary m.= accommodation for near vision

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4
Q

What is the oculomotor complex?

A

Oculomotor nucleus

Edinger-Westphal nucleus (EW-N)

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5
Q

What is the difference between the oculomotor nucleus & EW-N?

A 
Oculomotor= GSE to most of the extraocular muscles 
EW-N= GVE i.e. PNS
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6
Q

Where is the oculomotor complex located?

A

Rostral midbrain

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7
Q

Describe the pathway of the axons that arise from the oculomotor nucleus.

A

Oculomotor nucleus is located inferior to the EW-N & periaqueductal gray in the rostral midbrain. Axons:

- Pass through Red Nucleus into
- Exit in the Interpeduncular fossa
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8
Q

Where is the EW-N relative to the oculomotor nucleus? Describe the pathway of its axons.

A

Superior–axons follow the same path as the oculomotor nucleus

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9
Q

Where does CN III travel relative to the cerebral vasculature?

A

Between the

  • PCA
  • Basilar
  • Superior Cerebellar Artery
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10
Q

Where are aneurysms most common in the cerebral arteries? What are the clinical implications?

A

Bifurcations–this is close to the space that contains CN III

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11
Q

What foramen does CN III pass through to enter the orbit?

A

Superior orbital fissure

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12
Q

What sinus does CN III pass through? What is the clinical implication?

A

Cavernous sinus–infection or aneurysm in this sinus can impact the function of CN III

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13
Q

Where do preganglionic PNS fibers of EW-N terminate?

A

Ciliary ganglion

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14
Q

What nerve carries postganglionic fibers from the ciliary ganglion?

A

Short ciliary nerves of the trigeminal nerve (CN V)

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15
Q

What muscles do the short ciliary fibers of CN V innervate?

A

Ciliary muscle

Sphincter pupillae m.

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16
Q

What is the function of the ciliary muscle?

A

Lens accomondation for near vision

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17
Q

What is the function of the sphincter pupillae muscle?

A

Pupillary constriction

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18
Q

Describe the presentation of a CN III lesion in regards to its GSE function.

A

The following muscles will be impacted:
LPS = ptosis
- Compensation by raising the eyebrow= wrinkling of forehead

Sup/ Inf. Rectus= no vertical movement

Medial rectus= inability to move medially & no tone= eye pulled laterally

Inferior Oblique paralyzed but Superior oblique intact= down & out

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19
Q

Describe the presentation of a CN III lesion in regards to its GVE function.

A

Sphincter papillae= pupil is dilated (mydriasis)

Ciliary muscle= no accommodation of the lens for near vision/ focus i.e cannot focus on near objects

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20
Q

What is Horner’s Syndrome?

A

Damage of SNS fibers to the head from cervical ganglia

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21
Q

How do you know the difference between CN III Lesion & Horner Syndrome?

A

CN III lesion:

  • Ptosis (more severe)
  • Defective eye movements
  • Eye down & out
  • Mydriasis (dilated)

Horner Syndrome:

  • Ptosis (less severe)
  • NO defective eye movement
  • NO deviation
  • Miosis (constricted pupil)
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22
Q

Outline the pupillary light reflex.

A 
Afferent= optic nerve
Nucleus= EW-N
Efferent= oculomotor
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23
Q

Is the pupillary dilation reflex associated with the oculomotor nerve? SNS or PNS?

A
  • Not associated with the oculomotor nerve**

- SNS

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24
Q

What is Medial Midbrain Syndrome or Weber Syndrome?

A

Lesion to the rostral midbrain that affects the:

1) Corticospinal tracts
2) Corticonuclear tracts
3) CN III

**Results from occlusion of PCA or Basilar A.

25
Q

What is the functional component of CN IV?

A

GSE to the superior oblique

26
Q

Where is the trochlear nucleus located?

A

Ventral to the periaqueductal gray in the caudal midbrain

27
Q

What is special about the trochlear nerve?

A

1) Only CN to decussate in the brain

2) Emerges dorsally

28
Q

Where are the cell bodies of the right nerve are located?

A

In the left trochlear nucleus

29
Q

What space does the trochelar nerve pass through relative to the cerebral vasculature?

A

Space between PCA & superior cerebellar artery

**Like CN III

30
Q

Where does the CN IV enter the orbit?

A

Superior orbital fissure

31
Q

What sinus does CN IV pass through?

32
Q

What are the three main actions of the Superior Oblique muscle?

A

1) Intorsion
2) Depression
3) Abduction

33
Q

What is the mnemonic to remember the actions of the Superior Oblique?

A

“Salvation Army Muscle” i.e. down & out muscle

34
Q

What muscle assists the Superior Oblique in downward gaze? What are the clinical implications?

A

Inferior rectus–damage to the trochlear nerve/ nucleus results in WEAKNESS to downward gaze, but NOT total inability

35
Q

How does damage to the Trochlear nerve differ from damage to the trochlear nucleus?

A 
Nerve= ipsilateral defect 
Nucleus= contralateral defect
36
Q

What is the clinical manifestation of damage to the Trochlear nerve?

A
  • Upward gaze due to unopposed action of antagonist, the inferior oblique–referred to as “hypertropia”
  • Extorsion (rotation around axis laterally)
37
Q

What makes hypertropia worse?

A

1) Looking down, as in going down stairs
2) Medial gaze, as in reading
3) Tilting the head TOWARD the affected side

38
Q

How do patients compensate for hypertropia/ superior oblique lesion?

A

1) Tilt head away from affected side

2) Chin-tuck

39
Q

What is the functional component of the abducens nerve?

A

GSE to the lateral rectus muscle

40
Q

Where is the abducens nucleus located?

A

Caudal pons

41
Q

Where does the abducent nerve emerge?

A

Pontomedullary junction

42
Q

What foramen does the abducent nerve traverse to enter the orbit?

A

Superior orbital fissure

43
Q

What sinus does the abducent nerve pass through?

A

Cavernous sinus

44
Q

How does a lesion to the abducent nerve present?

A

Medial rotation of the eye i.e. “medial strabismus”

45
Q

How will a patient compenstate for a abducent nerve lesion?

A

Patient will turn the chin in the direction of the lesion

46
Q

What are the two groups of cell bodies contained in the abducens nucleus?

A

1) motor neurons to the abducent nerve
2) internuclear neurons (interneurons) that cross the midline, join the medial longitudinal fasiculus (MFL), & synapse with the oculomotor nucleus –specifically with cell bodies that innervate the medial rectus

47
Q

How does damage to the abducens nucleus manifest?

A

Horizontal gaze paralysis to the ipsilateral side i.e.

  • Abduction deficit on ipsilateral side
  • Adduction deficit on contralateral side
48
Q

What is the CNS center for conjugate horizontal gaze?

A

Abducens nucleus

49
Q

What higher brain center stimulates the abducens nucleus?

A

Reticular formation

50
Q

If the right abducens nucleus is stimulated, which direction will the eyes move?

51
Q

What is Internuclear Ophthalmolegia (INO)?

A

ADduction deficit of one eye during conjugate horizontal gaze away from the side of the lesion i.e. right lesion:

  • Gaze to the right is NORMAL
  • Gaze to the left is abnormal b/c
    1) Imparied adduction of right eye
    2) Nystagmus w/ abduction of left eye
52
Q

Where is the site of the lesion in INO?

A

MLF (medial longitudinal fasiculus) the tract that connects the abducens nucleus to the oculomotor nucleus of CN III

53
Q

Can a patient with INO converge their eyes?

A

YES–this is independent of the MLF

54
Q

What is “one-and-a-half” syndrome?

A

Lesion of one AN & ipsilateral MLF

  • Ipsilateral eye has NO horizontal movement
  • Contralateral eye can ABduct with nystagmus
55
Q

Where is the oculomotor complex located in the brainstem?

A

Rostral midbrain

56
Q

Where is the trochlear nucleus located in the brainstem?

A

Caudal midbrain

57
Q

Where is the abducens nucleus located in the brainstem?

A

Caudal pons

58
Q

Where is the facial nucleus located in the brainstem?

A

Caudal pons

Neuroanatomy (35 decks)

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