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Head and Neck > Cranial nerves 1-6 > Flashcards

Cranial nerves 1-6 Flashcards

1
Q

What is CN I?

A

The olfactory nerve

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2
Q

Where does CN I originate?

A

It is paired anterior extension of the forebrain

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3
Q

What is the route of CN I?

A

Olfactory nerves in roof of nasal cavity –> through the cribriform foramen of the ethmoid bone –> forms the olfactory bulb –> travels to the olfactory tract to the temporal lobe olfactory cortex

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4
Q

What is the function of CN I?

A

It has a special sensory function for smell

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5
Q

What fibres carry CN I?

A

SVA (special visceral afferent) that carry smell from roof of nasal cavity to CNS

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6
Q

What does the nerve innervate?

A

epithelia lining the nasal cavity

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7
Q

How is it tested?

A

ask for difficulties or change in smell

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8
Q

What is the medical term for loss of smell?

A

anosmia

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9
Q

Why would anosmia occur?

A
  • most commonly upper resp tract
  • secondary to head trauma (shearing forces over the olfactory nerves)
  • tumours at base of frontal lobe
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10
Q

What is CN II?

A

optic nerve

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11
Q

Where does CN II originate?

A

paired anterior extension of the forebrain

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12
Q

What is the route of CN II?

A

Retinal ganglion cells –> axons from optic nerve –> exits back of orbit via orbit canal –> fibres merge at optic chiasm –> occipital lobe visual cortex

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13
Q

What is the function of CN II?

A

special sensory - vision

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14
Q

What are the fibres involved with CN II?

A

special sensory afferent (SSA)

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15
Q

What occurs in the optic chiasm?

A

mixing of the sensory fibres from the right and left optic nerve

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16
Q

What does the optic tract contain?

A

sensory information from part of the right and left eye

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17
Q

How would you test for CN II?

A

-use opthalmoscope to look at the optic disc at the back of retina

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18
Q

What would show if there was raised incracranial pressure?

A

blurry and swollen )papilledema)

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19
Q

What would happen if a pituitary tumour was compression the optic chiasm?

A

bilateral hemianopia (bilateral visual symptoms)

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20
Q

What is the optic disc?

A

the point at which the nerve enters the retina

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21
Q

What is CN III?

A

the oculomotor nerve

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22
Q

Where does CN III originate?

A

mibrain

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23
Q

What is CNIII path?

A

midbrain –> lateral wall of cavernous sinus –> superior orbital fissure

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24
Q

What does CN III supply?

A
  • mnost extra-ocular muscles that move the eyeball
  • levatory palpebral superioris
  • sphincter pupillae (constricts the pupil)
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25
Q

What is its function?

A

motor and autonomic parasympathetic (eye movement and eyelid movement)

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26
Q

What does the parasympathetic supply?

A

the sphincter pupillae

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27
Q

What fibres are associated with CN III?

A

GVE and GSE - General visceral efferent and general somatic efferent

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28
Q

Which fibres is associated with the parasympathetic?

A

GVE (general visceral efferent)

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29
Q

What is the function of the ciliary muscle?

A

constrols pupil constriction and lens thickness (sphincter pupillae too?

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30
Q

How would you test CN III?

A
  • inspect eyelids and pupil size

- pupillary reflexes

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31
Q

What is the typical presentation of the oculomotor injury?

A

down and out eye (have to lift lid to see the eye due to weak muscle

32
Q

What can happen with increased intracranial pressure?

A

the uncus of the brain herniates of the edge of the tentorium cerebelli and compresses the nerve

33
Q

What is diplopia?

A

double vision

34
Q

What can pathology cause?

A

diplopia and pupillary dilation

35
Q

What are the causes for pathology of CN III?

A
  • raised intracranial pressure
  • tumour / haemorrhage
  • cavernous sinus thrombosis
  • secondary to diabetes/hypertension
36
Q

What will you find if the occulomotor nerve is compressors?

A

pupils constantly dilated as the parasympathetic fibres sit outside of the nerve so compression of the nerve will affect these fibres first

37
Q

What is CN IV?

A

Trochlear nerve

38
Q

Where does it originate?

A

midbrain

39
Q

What is its route?

A

mid brain (ventral part) –> cavernous sinus –> superior orbital fissue

40
Q

What is its function?

A

motor

41
Q

What does CN IV do?

A

innervates the superior oblique muscle of the eyeball (depress and laterally rotates the eyeball)

42
Q

Why does CN IV have the longest nerve route?

A

comes off the ventral part of the midbrain so has a longer intracranial route

43
Q

How would you test for CN IV?

A

testing eye movements

44
Q

What fibres does CN IV carry?

A

GSE

45
Q

What pathologies of CN IV can you get?

A
  • diplopia (rare)
  • congenital palsies
  • Head injury causing acute injury or raised ICP
46
Q

What is CN V?

A

trigeminal nerve

47
Q

What are its branches?

A

Va - opthalamic
Vb - maxillary
Vc - mandibular

48
Q

Where does CN V originate?

A

the pons

49
Q

What is the route of Va?

A

pons –> cavernous sinus –> superior orbital fissure –> orbit

50
Q

What is the route of Vb?

A

pons –> cavernous sinus –> foramen rotundum –> pterygopalatine fossa

51
Q

What is the route of Vc?

A

pons –> foramen ovale –> infra temporal fissure

52
Q

What is the function of CN V?

A

general sensory and motor

53
Q

What does CNV do?

A
  • sensory nerve suppling skin of face and some skull
  • sensory to deeper structures
  • motor to muscles of mastication
54
Q

What deeper structures does CN V supply?

A
  • paranasl sinuses
  • nasal and oral cavity
  • sensation to anterior tongue
55
Q

What branch supplies the muscles of mastication?

A

Vc

56
Q

What are the important branches of Va and what do they do?

A

supra orbital and supra trochlear

-sensory from the forehead

57
Q

What are the important branches of Vb and what do they do?

A

infraorbital and superior alveolar nerves

-sensory from cheek and lower eye lid AND sensory room deep structures of the face upper teeth and gum

58
Q

What are the important branches of Vc and what do they do?

A
  • inferior alveolar nerve, inguinal nerve, auriculotemproal
  • sensory from mental protuberance, lower lip and gym
  • general sensory from anterior tongue
  • general sensory from ear, temp and TMJ
59
Q

What nerve is blocked by dentists/ maxfax?

A

Vb - superior alveolar nerves

60
Q

What branch is most susceptible to injury i mandibular fractures?

A

Vc - inferior alveolar nerve

61
Q

How would you test for CNV?

A
  • sensation to face
  • muscles of mastication
  • corneal reflex
62
Q

What pathology of CNV can you get?

A
  • shingles (involves ophthalmic brach

- trigeminal neuralgia (Vb contributes to sudden attack of sharp facial pain

63
Q

What branch is most susceptible to injury in orbital floor fracture?

A

Vb - infraorbital branch

64
Q

What is CN VI?

A

abducens nerve

65
Q

Where does it originate?

A

lower pons

66
Q

What is CN VI route?

A

lower pons –> runs upwards to pass through cavernous sinus –> superior orbital fissure

67
Q

What is the function of CNVI?

A

motor

68
Q

What muscle does it supply?

A

lateral rectus causing abduction of the eyeball

69
Q

How would you test CNVI?

A

ask the patient to look to the right - the eye that doesn’t move is the one thats damages

70
Q

What would the patient present with and why?

A

diplopia as the eyes aren’t aligned

71
Q

Why can CNVI be easily stretched in raised ICP?

A

it emerges anterior at the ponto-medullary junction

72
Q

What other pathologies can you get with CNVI?

A

micro-vascular complication in diabetes or hypertension

73
Q

What fibres do CN V carry?

A

GSA and SVE

74
Q

What fibres does CNVI carry?

A

GSE

75
Q

How could an infection around the orbit spread intracranially?

A

-in opthlamic veins drain structures of the obit and drain mostly via the facial vein with which they anastomose - they also communicate with the cavernous sinus and as the veins are valveless, venous blood can pass in either direction

76
Q

ANSWER ON EXAMPLIFY ABOUT PATIENT HAVIN DIPLOPIA AND A LARGE BRAIN TUMOUR IN THE FRONTAL LOBE AND RAISED ICP - HOW CAN YOU EXPLAIN HIS SYMPTOMS?

A
  • optic nerve is an extension of the forebrain so carries the layers of the meninges with it
  • raised ICP increases pressure in the subarachnoid space
  • the nerve becomes external compressed
  • compression on the optic nerve leads to disruption int he optic nerve function

Head and Neck (13 decks)

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