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► Med - 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
What is the functional component of CN IV?
GSE to the superior oblique
26
Where is the trochlear nucleus located?
Ventral to the periaqueductal gray in the caudal midbrain
27
What is special about the trochlear nerve?
1) Only CN to decussate in the brain | 2) Emerges dorsally
28
Where are the cell bodies of the right nerve are located?
In the left trochlear nucleus
29
What space does the trochelar nerve pass through relative to the cerebral vasculature?
Space between PCA & superior cerebellar artery ****Like CN III
30
Where does the CN IV enter the orbit?
Superior orbital fissure
31
What sinus does CN IV pass through?
Cavernous
32
What are the three main actions of the Superior Oblique muscle?
1) Intorsion 2) Depression 3) Abduction
33
What is the mnemonic to remember the actions of the Superior Oblique?
"Salvation Army Muscle" i.e. down & out muscle
34
What muscle assists the Superior Oblique in downward gaze? What are the clinical implications?
Inferior rectus--damage to the trochlear nerve/ nucleus results in WEAKNESS to downward gaze, but NOT total inability
35
How does damage to the Trochlear nerve differ from damage to the trochlear nucleus?
``` Nerve= ipsilateral defect Nucleus= contralateral defect ```
36
What is the clinical manifestation of damage to the Trochlear nerve?
- Upward gaze due to unopposed action of antagonist, the inferior oblique--referred to as "hypertropia" - Extorsion (rotation around axis laterally)
37
What makes hypertropia worse?
1) Looking down, as in going down stairs 2) Medial gaze, as in reading 3) Tilting the head TOWARD the affected side
38
How do patients compensate for hypertropia/ superior oblique lesion?
1) Tilt head away from affected side | 2) Chin-tuck
39
What is the functional component of the abducens nerve?
GSE to the lateral rectus muscle
40
Where is the abducens nucleus located?
Caudal pons
41
Where does the abducent nerve emerge?
Pontomedullary junction
42
What foramen does the abducent nerve traverse to enter the orbit?
Superior orbital fissure
43
What sinus does the abducent nerve pass through?
Cavernous sinus
44
How does a lesion to the abducent nerve present?
Medial rotation of the eye i.e. "medial strabismus"
45
How will a patient compenstate for a abducent nerve lesion?
Patient will turn the chin in the direction of the lesion
46
What are the two groups of cell bodies contained in the abducens nucleus?
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
How does damage to the abducens nucleus manifest?
Horizontal gaze paralysis to the ipsilateral side i.e. - Abduction deficit on ipsilateral side - Adduction deficit on contralateral side
48
What is the CNS center for conjugate horizontal gaze?
Abducens nucleus
49
What higher brain center stimulates the abducens nucleus?
Reticular formation
50
If the right abducens nucleus is stimulated, which direction will the eyes move?
Right
51
What is Internuclear Ophthalmolegia (INO)?
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
Where is the site of the lesion in INO?
MLF (medial longitudinal fasiculus) the tract that connects the abducens nucleus to the oculomotor nucleus of CN III
53
Can a patient with INO converge their eyes?
YES--this is independent of the MLF
54
What is "one-and-a-half" syndrome?
Lesion of one AN & ipsilateral MLF - Ipsilateral eye has NO horizontal movement - Contralateral eye can ABduct with nystagmus
55
Where is the oculomotor complex located in the brainstem?
Rostral midbrain
56
Where is the trochlear nucleus located in the brainstem?
Caudal midbrain
57
Where is the abducens nucleus located in the brainstem?
Caudal pons
58
Where is the facial nucleus located in the brainstem?
Caudal pons

► Med - Neuroanatomy (36 decks)

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