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Semester 3 - Head and neck > 8. Cranial Nerves Continued > Flashcards

8. Cranial Nerves Continued Flashcards

1
Q

What is CNVII and where does it originate from?

A

Facial nerve, lateral lower pons (pontomedullary junction)

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2
Q

What is the path of CNVII?

A

Lower pons → Enters petrous bone via Internal auditory Meatus → 3 branches within petrous bone → Exits via sylomastoid foramen

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3
Q

What type of fibres are in CNVII?

A

Special sensory, Motor, parasympathetic

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4
Q

What autonomic fibres are in CNVII and what do they innervate?

A

Parasympathetic: Lacrimal glands, nasal glands, Salivary glands (except parotid)

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5
Q

What is the special sensory function of CNVII?

A

Anterior 2/3 of tongue (taste)

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6
Q

What is the motor function of CNVII?

A

Muscles of facial expression, Stapedius (in middle ear)

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7
Q

Where does the facial nerve first branch and what is the name of the branch?

A

At the geniculate ganglion in the petrous bone

- first of the three intrapetrous branches = greater petrosal nerve

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8
Q

What is the route of the greater petrosal nerve and where does it branch?

A

Leaves petrous bone and branches at pterygopalatine fossa to lacrimal, nasal and oral/palatal mucosal glands

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9
Q

What is the 2nd branch of the facial nerve?

A

nerve to stapedius - branches in middle ear cavity

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10
Q

What type of fibres are in the greater petrosal nerve?

A

purely parasympathetic

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11
Q

what type of fibres are in nerve to stapedius?

A

purely motor

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12
Q

If a lesion affects the nerve to stapedius how may it present?

A

hyperacoustic

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13
Q

what is the third branch of the facial nerve in the petrous bone

A

chorda tympani

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14
Q

What fibres are in the chorda tympani nerve and what are their functions?

A

Parasympathetic: Salivary glands

Special sensory: Anterior 2/3rd tongue

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15
Q

describe the route of the facial nerve after it passes through the stylomastoid foramen?

A

now only contain motor fibres

- route through parotid gland and gives of five terminal extra cranial branches

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16
Q

what are the 5 extra cranial branches of facial nerve?

A

To Zanzibar By Motor Car

temporal
zygomatic 
buccal
marginal mandibular
cervical
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17
Q

How is CNVII tested?

A

Mainly by testing muscles of facial expression (and the corneal reflex orbicularis oculi to close the eye)

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18
Q

Why can symptoms of CNVII lesion vary?

A

Depends on where along the nerve route the pathology is

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19
Q

how do facial nerve lesions present?

A

Unilateral facial droop +/- reporting symptoms due to absence of other facial nerve functions:
Hyperacusis (noise sensitivity), dry eyes, altered taste, dry mouth

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20
Q

Why can middle ear and parotid pathology affect CNVII?

A

Occurs in petrous bone which facial nerve passes through. Passes through parotid gland.

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21
Q

what are some causes of facial nerve lesions?

A
  • Lesions in/around internal acoustic meatus & posterior cranial fossa tumours - point of vulnerability
  • Basal skull fracture (involving petrous bone)
  • Middle ear disease
  • Inflammation in facial canal…facial nerve palsy e.g. Bell’s Palsy, Ramsay-Hunt Syndrome
  • Parotid disease
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22
Q

What is Bell’s Palsy?

A

facial nerve paralysis

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23
Q

what is Ramsay-Hunt syndrome?

A

Varicella zoster infecting facial nerve - shingles

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24
Q

what are distinguishing features of Ramsay hunt syndrome

A

unilateral facial droop

vesicles or rash within external ear

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25
Q

what is key when determining whether facial droop is due to stroke or facial nerve lesion?

A

forehead sparing - stroke

  • Involving motor pathways anywhere along path from primary motor cortex to where synapse with facial nerve motor nuclei
    Upper half of contralateral face spared (has back-up)
  • Involving facial nerve anywhere from from exit from brain stem And along its route to target tissue
    Whole half ipsilateral face
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26
Q

explain how to identify if forehead spared?

A

if forehead affected - no furrows, cannot raise eyebrows

if forehead spared - furrows remain and able to raise eyebrows

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27
Q

why is the forehead spared in stroke but not facial nerve lesion?

A

facial nerve nuclei split into top and bottom half and top half has both contralateral and back up ipsilateral innervation from PMC so if contralateral affected in a stroke then it has a back up supply so forehead spared. lower half has only contralateral supply so leads to contralateral facial droop of lower half

if the facial nerve is affected after it has left brainstem, all motor elements it supplies will be affected on the ipsilateral side

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28
Q

What is CNVIII and where does it originate from?

A

Vestibulocochlear, from the lateral lower pons (pontomedullary junction)

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29
Q

What is the path of CNVIII

A

Cochlea & Semicircular canals (vestibular system) {within petrous bone} → Vestibulocochlear nerve → Internal Acoustic Meatus → lower pons

30
Q

What type of fibres does CNVIII have?

A

Special sensory

31
Q

What is the function of CNVIII?

A

Hearing and balance

32
Q

How is CNVIII tested?

A

gross bedside hearing test (whispering 99 in each ear)* and enquiring about balance + tuning fork testing

33
Q

how do CNVIII lesions present?

A

Hearing loss +/- dizziness (vertigo) +/- tinnitus

34
Q

what are causes of CNVIII lesions?

A
  • Vestibular schwannoma (and other posterior cranial fossa tumours)
  • Occlusion of labyrinthine artery
  • Base of skull fracture (involving petrous bone)
  • Brainstem lesion (pons)- rare ++
35
Q

What is an acoustic neuroma/Vestibular schwannoma?

A

Benign tumour of schwann cells surrounding the vestibulocochlear nerve, compressing the nerve

36
Q

What are the signs and symptoms of acoustic neuroma?

A
  • Unilateral hearing loss
  • Tinnitus
  • Vertigo
  • Numbness, pain or weakness down one half of face (involvement of facial and trigeminal nerves )
37
Q

Define presbyacusis.

A

old-age related hearing loss

38
Q

Damage to what structures causes hearing loss?

A

Cochlea, cochlear component of vestibulocochlear nerve, or brainstem nucleus

39
Q

Damage to what structures causes balance disturbance?

A

Semicircular canals, vestibular component of vestibulocochlear nerve, or brain nucleus

40
Q

What do the 4 medullary cranial nerves enter after leaving the skull?

A

Carotid sheath, all exit at some point except vagus

41
Q

What is CNIX and where does it originate from?

A

Glossopharyngeal Nerve from the lateral superior medulla

42
Q

What is CNX and where does it originate from?

A

Vagus, from later upper medulla

43
Q

describe the route of CN IX and X

A

Arise from medulla
Run through posterior cranial fossa
Exit through jugular foramen
Enter into carotid sheath- close relationship with internal and external carotid arteries

44
Q

What type of fibres does CNIX have?

A

General sensory, special sensory, autonomic, motor

45
Q

What is the MAIN function of CNIX?

A

Sensory supply of oropharynx, posterior ⅓ tongue (SS and GS)and middle ear

46
Q

What is the general sensation of CNIX?

A
  • (Palatine) tonsils and oropharynx
  • Middle ear and tympanic membrane (medial side)
  • Sensory from carotid body and sinus
  • Pos 1/3 tongue
47
Q

WHat is the special sensory of CNIX?

A

Taste of posterior 1/3 tongue

48
Q

What is the autonomic function of CNIX?

A

Carries parasympathetic innervation to parotid gland

49
Q

WHat is the motor function of CNIX?

A

Supplies one muscle (stylopharyngeus) which assists in swallowing

50
Q

How is CNIX function tested?

A

Tested in conjunction with vagus nerve (CN X) (when asking patient to swallow)

51
Q

What type of fibres are in CNX?

A

General sensory, motor and autonomic

52
Q

What are the general sensory functions of CNX?

A
  • Sensory to laryngopharynx, and the whole larynx

* Sensory to small part of external ear(external auditory meatus) and tympanic membrane(lateral side)

53
Q

What is the motor function of CNX?

A

• Muscles of soft palate, pharynx, larynx

54
Q

What are the autonomic functions of CNX?

A

Parasympathetic to thoracic (e.g. heart, tracheobronchial tree) and abdominal viscera

55
Q

How is CNIX and X function tested?

A

tested together
Speech, swallow, cough,
soft palate movement & uvula position [CN X]
[gag reflex: IX & X]

56
Q

how is soft palate elevation tested?

A

get patient to say AHHH
if both right and left side of soft palate innervation is intact, soft palate muscle rises equally and uvula stays in centre

if vagus nerve lesion on one side, affected side soft palate won’t elevate and uvula deviates away from weaker side

57
Q

what can cause lesions of CN IX and X?

A
  • RLN branch of CN X- (thyroid pathology or surgery; superior thorax/mediastinal pathology)
  • Pathology involving carotid sheath structures (e.g. common or internal carotid artery dissection/surgery)
  • Posterior cranial fossa tumours, base of skull #s (jugular foramen)
  • Brainstem (medullary) lesions e.g. infarct, MND
58
Q

What is CNXI and where does it originate from?

A

Spinal accessory nerve, Posterolateral medulla

59
Q

What is CNXII and where does it originate from?

A

Hypoglossal nerve, lateral to medullary pyramid

60
Q

describe the path of CN XI and XII

A
  • Arise from medulla (accessory nerve also has some contribution from upper cervical spinal nerves)
  • Run through posterior cranial fossa
  • CNXI exit skull through jugular foramen
  • CNXII exit through hypoglossal canal
  • Enter into carotid sheath-
  • Hypoglossal exits and travels towards tongue
  • Accessory exits and heads towards posterior triangle
61
Q

What type of fibres are in CNXI?

A

Motor

62
Q

What is the function of CNXI?

A

Motor to sternocleidomastoid and trapezius

63
Q

What is the path of CNXI?

A

Medulla → Jugular foramen → carotid sheath → deep to SCM → posterolaterally across posterior triangle → deep to trapezius

64
Q

How is function of CNXI tested?

A
  • Shrug shoulders against resistance (trapezius)

* Turn head against resistance (sternocleidomastoid)

65
Q

Where is CNXI susceptible to damage?

A
  • Spinal accessory runs inferiorly through neck in posterior triangle (is quite superficial)
  • Susceptible to injury in this area e.g. in lymph node biopsies, surgery, stab wound
66
Q

causes of CNXI lesions?

A

fd

67
Q

What is the path of CNXII?

A

Medulla → hypoglossal canal → carotid sheath → medial to mandible angle → between carotids

68
Q

What type of fibres are in CNXII?

A

Motor

69
Q

What is the function of CNXII?

A

Innervates Muscles of the tongue (all except one)

70
Q

How is CNXII function tested?

A

Inspection and movement of the tongue, damage to CNXII cause weakness and atrophy of tongue on ipsilateral side, tongue deviates towards damaged side

71
Q

describe tongue protrusion test for hypogossal damage

A

when asked to stick tongue out, should stay in middle. if damage to hypoglossal nerve, muscle on affected side becomes weak and so tongue deviates to weaker side.

tongue never lies

72
Q

what can cause hypoglossal nerve lesions?

A

Inspection and movement of the tongue, damage to CNXII cause weakness and strophy of tongue on ipsilateral side, tongue deviates towards damaged side

Semester 3 - Head and neck (17 decks)

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