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Sem 4 > H&N 4: Cranial Nerves > Flashcards

H&N 4: Cranial Nerves Flashcards

1
Q

What is CN I?

A

Olfactory nerve

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2
Q

What number is the optic nerve?

A

CN II

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3
Q

What number is the oculomotor nerve?

A

CN III

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4
Q

What is CN IV?

A

Trochlear nerve

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5
Q

What is cranial nerve V?

A

Trigeminal

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6
Q

What number is the abducens nerve?

A

CN VI

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7
Q

What number is the facial nerve?

A

CN VII

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8
Q

What number is the vestibulocochlear nerve?

A

CN VIII

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9
Q

What number is the glossopharyngeal nerve?

A

CN IX

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10
Q

What is cranial nerve X?

A

Vagus

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11
Q

What is cranial nerve XI?

A

Spinal accessory nerve

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12
Q

What is cranial nerve XII?

A

Hypoglossal nerve

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13
Q

What type of nerve fibres does the olfactory nerve transmit?

A

Special sensory (sense of smell)

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14
Q

Where does the olfactory nerve originate from?

A

Forebrain (only CN I and II do not originate form the brainstem)

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15
Q

What does the olfactory nerve pass through to go to the cranial cavity?

A

The cribiform plate of the ethmoid bone (roof of the nasal cavity)

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16
Q

What is anosmia and how can it be caused?

A

Absence of sense of smell
Temporary could be caused by URTI
Permanent could be caused by head injury, tumour, Alzheimer’s or Parkinson’s

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17
Q

What type of nerve fibres does the optic nerve transmit?

A

Special sensory (vision)

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18
Q

Where does the optic nerve originate?

A

From the forebrain (as does CN I)

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19
Q

What is the anatomical course of the optic nerve?

A

From the retina, leaves the orbit via the optic canal (in the sphenoid bone) and then each optic nerve from each eye unites to form the optic chiasm (by the pituitary gland). They then form the optic tracts to the forebrain.

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20
Q

Why can a pituitary adenoma lead to visual problems?

A

As the pituitary gland lies very close to the optic chiasm (in the middle cranial fossa), so enlargement of the pituitary gland can compress the optic nerves and affect their function

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21
Q

Where does the oculomotor nerve originate from?

A

Midbrain (of the brainstem)

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22
Q

What type of nerve fibres does the oculomotor nerve transmit?

A

Mainly motor fibres to most of the extra-ocular muscles

Also autonomic fibres (parasympathetic)

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23
Q

What are the parasympathetic functions of the oculomotor nerve?

A

To the ciliary body (contracts so the lens is adapted to more short range vision)
And sphincter pupillae (constricts the pupil to reduce the amount of light that can enter the eye)

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24
Q

What is the anatomical course of the oculomotor nerve?

A

Emerges from the midbrain
Runs in the roof of the cavernous sinus
Leave cranial cavity via superior orbital fissure, into the orbit

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25
Q

What are the clinical signs of a CN III lesion?

A
  • down and out eye (due to paralysis of superior, inferior and medial rectus and inferior oblique)
  • ptosis (due to paralysis of levator palpebrae superioris)
  • dilated pupil (due to unapproved action of dilator pupillae)
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26
Q

What may cause a lesion of the oculomotor nerve?

A 
Raise ICP (tumour/ haemorrhage)
Aneurysm
Cavernous sinus thrombosis
Hypertension 
Trauma
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27
Q

Where does the trochlear nerve originate from?

A

From the midbrain of the brainstem
It is the only CN to arise from the dorsal aspect of the brainstem, hence it has the longest INTERcranial root of all CNs

28
Q

What nerve fibres does the trochlear nerve transmit/ what is its function?

A

Only motor fibres to the superior oblique muscle (which depresses and intorts the eyeball)

29
Q

What is the anatomical course of the trochlear nerve?

A

From dorsal aspect of the midbrain
In cavernous sinus
Enters superior orbital fissure

30
Q

The trigeminal nerve is associated with derivatives from which pharyngeal arch?

A

1st

31
Q

Where does the trigeminal nerve arise from and what is the anatomical course of its branches?

A

From the pons of the brainstem arise 3 peripheral processes

Ophthalmic branch leaves cranium via superior orbital fissure
Maxillary branch leaves cranium via foramen rotundum
Mandibular branch leaves cranium via foramen ovalae

Both ophthalmic and maxillary branches pass through cavernous sinus

32
Q

What type of nerve fibres does the branches of the trigeminal nerve convey?

A

V1: sensory to forehead, scalp, upper eyelid and dorsum of nose. Parasympathetic to lacrimal gland

V2: sensory to lower eyelid, lateral nose, cheeks, upper lip. Parasympathetic to lacrimal gland

V3: sensory to lower lip, mucous membranes, anterior 2/3rds of tongue, chin, external ear. Motor mainly to muscles of mastication. Parasympathetic to salivary glands (parotid, sublingual and submandibular)

33
Q

How can the trigeminal nerve be examined?

A
  • ask px to close eyes and touch divisions of the face with cotton wool
  • ask them to clench claw and deviate mandible from side to side
  • test corneal reflex
34
Q

What is the corneal reflex and what is the afferent and efferent limb?

A

Involuntary blinking of the eye by tactile or painful stimulation of cornea
Afferent branch is CN V1 which detects the stimuli
Efferent branch is CN VII which causes contraction of orbicularis oris muscle
Abscent corneal reflex indicates damage to either of these nerves

35
Q

Where does the abducens nerve arise from and what is its anatomical course?

A

From the pons of the brainstem, through the cavernous sinus, enters the orbit via the superior orbital fissure to innervate lateral rectus muscle

36
Q

What is the function of the abducens nerve?

A

Only motor function, to the lateral rectus muscle (which abducts the eyeball away from the midline)

37
Q

The facial nerve is associated with derivatives from which pharyngeal arch?

A

2nd

38
Q

What are the functions of the facial nerve?

A

Motor: mainly to muscle of facial expression, also muscles of the ear
Special sensory: taste to anterior 2/3rd tongue (NOT general sensory, this is done by CNV3)
Parasympathetic: to many glands including submandibular, sublingual, lacrimal, nasal

39
Q

Where does the facial nerve terminate into its 5 motor branches and what are the branches?

A 
In the parotid gland (although this is not innervated by the facial nerve)
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical
40
Q

Which branch of the facial nerve is special sensory to the anterior 2/3rds of the tongue?

A

Chorda tympani

41
Q

The parasympathetic fibres of the facial nerve are carried out by which branches?

A

Greater petrosal nerve and chorda tympani

42
Q

What is the anatomical course of the facial nerve?

A

Intercranial:
Arise from the pons of the brainstem, through the internal acoustic meatus of the petrous part of the temporal bone, through the facial canal and then exits via stylomastoid foramen

Extracranial:
Runs by ear, and splits into its terminal branches in the parotid gland

43
Q

How can symptoms of facial nerve palsy differ if the lesion is intercranial or extra cranial?

A

Intercranial:
Paralysis of muscles of facial expression as well as different effects depending on affected branches eg chorda tympani damage can cause reduced salivation and taste on ipsilateral 2/3rd tongue, nerve to stapedius can cause ipsilateral hyperacusis, greater petrosal nerve could cause ipsilateral reduced lacrimal fluid production

Extracranial:
Damage would only affect motor function ie muscles of facial expression

44
Q

What are causes of facial nerve lesions?

A

Idiopathic is termed Bell’s palsy
Lesion of extrcranial branches could be due to parotid gland pathology, infection (eg by herpes virus), compression during forceps delivery
Most common cause of intercranial lesion is middle ear pathology eg infection or tumour

45
Q

What is the function of the vestibulocochlear nerve?

A

Purely special sensory, for hearing and balance

46
Q

Where does the vestibulocochlear nerve arise from and where does it exit the cranium?

A

Arises from the pons of the brainstem, exits the cranium via the internal acoustic meatus of the temporal bone

47
Q

The glossopharyngeal nerve is associated with derivatives of which pharyngeal arch?

A

3rd

48
Q

What are the functions of the glossopharyngeal nerve?

A

Special sensory: taste to posterior 1/3rd tongue
Sensory: oropharynx, carotid body and sinus, posterior 1/3rd tongue, Eustachian tube, middle ear
Motor: stylopharyngeus muscle in the pharynx
Parasympathetic: parotid gland

49
Q

Where does the glossopharyngeal nerve arise from and where does it pass through the cranium?

A

Arises from the medulla of the brainstem

Leaves cranium via the jugular foramen

50
Q

What are the afferent and efferent nerves involved in the gag reflex?

A

Afferent: glossopharyngeal
Efferent: vagus

51
Q

The 4th pharyngeal arch is associated with which nerve?

A

Vagus nerve, CN X

52
Q

What is the rough anatomical course of the vagus nerve?

A

Longest course of all CNs
Arises rom the medulla of the brain stem
Leaves cranium via the jugular foramen
Passes through the carotid sheath in the neck
Down into the thorax and terminate in the abdomen, giving off branches as it descends

53
Q

What is the function of the vagus nerve?

A

Sensory: larynx, part of ear, heart, GI tract
Motor: muscles in soft palate, larynx and pharynx
Special sensory:
Parasympathetic: heart and GI tract, SM of trachea and bronchi

54
Q

How does the root of the right recurrent laryngeal nerve differ to that of the left recurrent laryngeal nerve?

A

Right: hooks under the right subclavian artery and ascends to the larynx
Left: hooks under the arch of the aorta and ascends to the larynx

55
Q

What may some symptoms of a CN X lesion be?

A

Dysphagia, dysphonia

56
Q

What is the function of the accessory nerve?

A

Motor innervation to SCM and trapezius

57
Q

How could the accessory nerve function be tested?

A

Ask the patient to shrug their shoulders (trapezius) and turn their head against resistance (SCM), could also observe for any muscle wastage

58
Q

What is the anatomical course of the accessory nerve?

A

From the medulla of the brain stem, through the jugular foramen and into the posterior triangle of the neck

59
Q

What is the anatomical course of the hypoglossal nerve?

A

Arises from the medulla of the brainstem, exits the cranium via the hypoglossal canal, runs inferior to mandible and crosses over the ICA and ECA to enter the tongue
(Must be wary not to damage CNXII in surgery of carotid arterie due to closeness!)

60
Q

What is the function of the hypoglossal nerve?

A

Motor function to most of the muscles in the tongue, hence CN XII lesion can present as ipsilateral tongue weakness or atrophy

61
Q

What foramina/ fissures do the three branches of the trigeminal nerves pass through and what areas do they each go to?

A

Ophthalmic branch goes through superior orbital fissure into the orbit

Maxillary branch goes through foramen rotundum in pterygopalatine fossa

Mandibular branch goes the formamen ovale into the infratemporal fossa

62
Q

Which cranial nerves pass into the orbit and what do they pass through?

A

CN II, III, IV, Vi, VI

All pass through superior orbital fissure other than CN 1 (optic nerve) which passes through optic canal

63
Q

Where is the cavernous sinus located?

A

One on either side of the sella turcica

64
Q

What structures pass through the cavernous sinus?

A

Internal carotid artery

CN III, IV, Vi, Vii, VI

65
Q

What is a cavernous sinus thrombosis?

A

A venous blood clot within the cavernous sinus

Could be a late complication of infection in the danger triangle of the face/ orbits/ paranasal sinuses/ maxillary teeth

66
Q

A lesion to which cranial nerve will leave patients struggling to walk downstairs?

A

Trochlear nerve
As this innervates superior oblique muscle
Often present with a subtle head tilt as a result

Sem 4 (25 decks)

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