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Brain and Behavior Exam 1 > Lec 10 Cranial Nerves > Flashcards

Lec 10 Cranial Nerves Flashcards

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1
Q

What does somatic efferent innervate?

A

skeletal muscles

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2
Q

What does visceral efferent innfervate?

A

scmooth muscle, cardiac muscle, or glands

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3
Q

Which CN is not considered part of the peripheral nervous system?

A

CN II [optic]

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4
Q

What are 2 exceptions to the rule that cortical innervation of CNs is bilateral?

A

parts of

  • CN VII [facial]
  • CN XII [hypoglossal]
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5
Q

What is significant about CN cortical innervation being bilateral?

A
  • a unilateral cortical lesion would not significantly impact cranial nerve function
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6
Q

What is the 2, 4, 3 rule for Cn exit? Which cranial nerves are ignored in this rule?

A
  • 2 out of midbrain: CN III, CN IV
  • 4 out of pons: CN V, CN VI, CN VII, CN VIII
  • 3 out of medulla: CN IX, CN X, CN XII
  • ignores I, II, XI
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7
Q

Do the cranial nerves ever cross?

A

No, except the 4th CN

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8
Q

Are clinical findings on the same side or opposite side from cranial nerve involved?

A

same side!

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9
Q

How do you test for olfactory nerve clinically?

A
  • close eyes, test each side individually with other nostril occluded
  • place aromatic stimulus under nostril – coffee, chocolate
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10
Q

What is anosmia?

A
  • loss of smell, often accompanies by loss of sensation of taste
  • can be due to anterior cranial fossa fracture
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11
Q

What is parosmia? cause?

A

perversion of sense of smell

- due to temporal lobe pathology

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12
Q

What is CSF rhinorrhea? cause?

A
  • can occur with cribiform plate fracture [trauma/tumor]

- get CSF leaking through dural tear

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13
Q

What is olfactory hallucination? cause?

A
  • hallucinations of sense of smell [smell something that isn’t there]
  • common with temporal lobe seizures
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14
Q

What is papilledema? significance?

A
  • swelling of optic nerve

- usually sign of increased intracranial pressure

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15
Q

What is optic atrophy?

A
  • pale optic nerve
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16
Q

what is optic neuritis? presentation?

A
  • inflammatory response along optic nerve

- presents with pain on eye movement, central visual loss, decreased visual acuity, altered color vision

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17
Q

Where is primary visual cortex?

A

posterior pole of occipital

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18
Q

How can pituitary tumor affect optic?

A
  • can compress optic chiasm and lead to visual field defects
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19
Q

What are the 4 parts to the CN2 examination?

A
  1. acuity [snellens]
  2. visual fields
  3. pupillary reflexes
  4. fundoscopy
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20
Q

What eye movements is medial rectus responsible for?

A

adduction

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21
Q

What eye movements is inferior rectus responsible for?

A

depression

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22
Q

What eye movements is superior rectus responsible for?

A

elevation

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23
Q

What eye movements is inferior oblique responsible for?

A

extorsion [rotate out]

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24
Q

What eye movements is superior oblique responsible for?

A

intorsion [rotate in]

CN IV

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25
Q

What eye movements is lateral rectus responsible for?

A

abduction

CN VI

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26
Q

Where do the fibers of occulomotor nerve arise?

A

from nucleus in midbrain at level of superior colliculus

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27
Q

What is function of edinger-westphal nucleus?

A

responsible for autonomic function of oculomotor –> pupillary constriction, lens accomodation

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28
Q

Where does the occulomotor nerve exit?

A

ventrally from interpeduncular foss of midbrain

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29
Q

Where does the occulomotor nerve enter the orbit?

A

through superior orbital fissure

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30
Q

What are signs of 3rd nerve palsy? Cause?

A
  • wrinkled forehead, raised eyebrow, ptosis [drooped eyelid], dilated pupil [+light sensitivity], down and out eye
  • can get it from posterior communicating artery aneurysm or other compressive lesion to 3rd nerve
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31
Q

Aneurysm of what artery would lead to 3rd nerve palsy?

A

posterior communicating artery

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32
Q

What is diabetic 3rd nerve palsy?

A
  • due to ischemic lesion to nerve, lose nerve but spare pupil/pupilloconstrictor fibers that travel on outside of nerve
  • get pain
  • resolves in 4-6 wks
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33
Q

What part of oculomotor function is lost first in a compression related lesion?

A

parasympathetic [pupil constriction] lost first –> get dilated pupil and photosensitivity

  • because parasympathetic fibers run on the outside of the nerve
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34
Q

What part of oculomotor function is spared in diabetic 3rd nerve palsy?

A

parasympathetic [pupil constriction] spared

  • because parasympathetic fibers run on the outside of the nerve
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35
Q

What is the only cranial nerve that exits from dorsal aspects of brainstem?

A

trochlear nerve

36
Q

What is the only cranial nerve to originate totally from the contralateral nucleus?

A

trochlear nerve

37
Q

Which nerve has the longest intracranial course of all cranial nerve?

A

trochlear nerve

38
Q

What are signs of trochlear lesion?

A
  • affected high slightly elevated and extorted

- might see patient tilting head to normal side so both eyes can be at same angle

39
Q

What is the largest cranial nerve?

A

trigeminal [CN V]

40
Q

What are the 3 sensory nuclei of trigeminal nerve [and function of each]?

A

spinal trigeminal nucleus: pain, temperature, crude touch

pontine trigeminal/chief sensory nucleus: discriminative touch

mesencephalic nucleus: proprioceptions from muscles of mastication

41
Q

Where is the motor nucleus for trigeminal?

A

in the pons, travels with mandibular division

42
Q

Where does V1 [trigeminal opthalmic] leave?

A

leaves orbit through superior orbital fissure

43
Q

Where does V2 [trigeminal maxillary] enter skull?

A

enters skull through foramen rotundum

44
Q

Where does V3 [trigeminal mandibular] enter skull?

A

enters skull through foramen ovale

45
Q

Which of the 3 trigeminal branches has motor output?

A
  • all 3 have sensory

- only mandibular has motor as well

46
Q

Where is the trigeminal ganglion?

A

meckel’s cave in pos

47
Q

Where does trigeminal exit the brain?

A
  • lateral surface of pons [large sensory root and smaller motor root emerge]
48
Q

What is the trigeminal autonomic reflex?

A
  • irritation of trigeminal leads to parasympathetic activation [eyes tear, nose run] because of close proximity of superior salivatory nucleus
49
Q

What is trigeminal neuralgia? signs? cause?

A
  • usually one sided V2 and V3 distribution
  • repetitive, brief stabbing pains
  • affects age 40+
  • have trigger zones that cause electric pain when lightly touch
  • symptoms occur only during day not during sleep
  • due to vascular compression by looping SCA [superior cerebellar artery]
50
Q

What is treatment for trigeminal neuralgia?

A
  • antiepileptic drugs

- neurosurgery

51
Q

What common virus can affect trigeminal ganglion?

A
  • herpes zoster –> get herpes opthalmicus
52
Q

What happens with CN V in brainstem lesion?

A

have ipsilateral pain/temp and sensory loss

53
Q

What happens with CN V in cerebrum lesion?

A

have contralateral sensory loss

54
Q

What is jaw jerk?

A

get problem with CNV3 [mandibular] –> issue with trigeminal motor, jaw deviates toward lesion side

55
Q

What is so special about trigeminal nerve root entry zone?

A
  • proximal trigeminal nerve root is sensitive to vascular compression since oligodendrocyte-derive myelination surrounds axons 3-5 mm from lateral pons
  • not as sturdy as peripheral schwann myelin
  • fibers associated with light touch are closest to this zone so most at risk
56
Q

Where does CN VI emerge?

A

pons at pontomedullary junction

57
Q

Where does CNVI enter the orbit?

A

via superior orbital fissure

58
Q

What is sign of lesion at CN VI? Cause?

A
  • diplopia [double vision] at a distance, medially directed eye
  • likely due to increased ICP
59
Q

Where does CN VII emerge?

A
  • pons at pontomedullary junction
60
Q

What is unique about upper motor neuron vs lower motor neuron supply for facial nerve?

A
  • supply to upper facial muscles = bilateral
  • supply to lower facial muscles = contralateral

thus: if injury to 1 of upper motor neurons [ex stroke], forehead muscles not affected, BUT contralateral lower face muscles will be affected

61
Q

What happens if lower motor neuron lesion [damage to facial nerve itself or brainstem nucleus]?

A
  • facial palsy on same side as lesion

- upper and lower parts of the face are affected

62
Q

What are some common causes of facial nerve lesion?

A
  • bell’s palsy
  • meningeal process
  • stroke involving nerve VII nuclesu
63
Q

What happens if upper motor neuron lesion to facial nerve?

A
  • contralateral lower facial paralysis

forehead spared due to bilateral innervation

64
Q

What happens in bell’s palsy?

A

ipsilateral total facial paralysis

- drooping, teariness or dryness, pain in or behind ear, drooling, loss of sense of taste

65
Q

Where does CN VIII exit?

A

medulla/pons junction, cerebellopontine angel

66
Q

What causes hemifacial spasm?

A
  • facial nerve compressed by dilated vertebral artery
67
Q

What does gag reflex test?

A
  • sensory component of IX

- motor component of X

68
Q

What is glossopharyngeal neuralgia?

A
  • stabbing pain in throat triggered by yawning/swallowing

- can be associated with bradycardia

69
Q

What is eagle’s syndrome?

A
  • lesion of nerve IX

- dysphagia [difficulty swallowing], unilateral pharyngeal pain with swallowing

70
Q

What is sensorineural hearing loss?

A

hearing loss due to problem with CN VIII, inner ear, or central processing centers of brain

71
Q

What is conductive hearing loss?

A

hearing loss due to problem with middle ear, tympanic membrane, or external ear

72
Q

What happens in acoustic neuroma?

A
  • loss of function of CN VIII (and sometimes CN VII as well)
73
Q

Where does CN IX exit?

A
  • upper medulla from post-olivary sulcus, dorso-lateral to olive
74
Q

Where does CN X exit?

A
  • medullar from post-olivary sulcus, dorso-lateral to olive
75
Q

Where does uvula deviate in CNX lesion?

A

toward normal side [away from lesion]

76
Q

What does glomus jugulare tumor affect? who gets it?

A
  • affects IX, X, XI
  • get pulsatile tinnitus
  • most common in middle aged women
77
Q

What are signs of CN XI lesion?

A
  • weakness turing head to side contralateral to lesion
  • shoulder droop ipsilateral to lesion
  • compression by glomus jugulare tumor
78
Q

Are the CN XI fibers supplying the trapezius or those supplying the sternocleidomastoid more vulnerable?

A
  • those supplying trapezius are more vulnerable
79
Q

Where does CN XII emerge?

A
  • from medulla in area between pyramid and olive
80
Q

What does CN XII innervate?

A

all intrinsic muscles except palatoglossus

81
Q

How do you check for CN XII function?

A
  • check for tongue protrusion in midline
  • tongue will deviate to side of weakness [away from normal]
  • check for slurred speech
82
Q

What would happen in lower motor neuron lesion to CN XII?

A
  • tongue deviates toward lesion, atrophy, fasciculations

- due to: damage to brainstem nucleus or hypoglossal nerve itself from tumors, surgery, amyotrophic lateral sclerosis

83
Q

What would happen in upper motor neuron lesion to CN XII?

A
  • tongue deviates away from lesion, no atrophy or fascicultations
  • due to: cortical stroke or tumor
84
Q

What is pseudobulbar palsy?

A
  • bilateral damage to corticobulbar tracts [pathway from cortex to brainstem]
  • symptoms: inability to control facial movements, impaired swallowing, spastic speech, random crying and laughing spells
  • nerves V, VII, IX, X, XI, XII affeced
85
Q

How do you treat pseudobulbar palsy?

A

dextromethorphan

Brain and Behavior Exam 1 (15 decks)

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