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3 - HNN > Cranial Nerves > Flashcards

Cranial Nerves Flashcards

1
Q

State the number of cranial nerves arising from each part of the brain

A
  • 2 from forebrain
  • 2 from midbrain
  • 4 from pons
  • 4 from medulla
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2
Q

State the cranial nerves that arise from the forebrain

A
  • Olfactory nerve

- Optic nerve

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3
Q

State the function of the olfactory nerve

A

Olfaction - special sensory nerve

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4
Q

Describe the route of the olfactory nerve to the forebrain

A

Nasal epithelium -> cribiform foramina -> olfactory bulb -> olfactory tracts -> forebrain

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5
Q

How is the olfactory nerve tested

A
  • Ask for difficulties or changes in sense of smell

- Test one nostril at a time - one damaged nostril can be compensated by the other

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6
Q

What is the consequence of damaged olfactory nerve

A
  • Loss of sense of smell = ansomia
  • Commonest cause of ansomia - common cold
  • Head injury can cause ansomia
    • Shearing forces which damaged nerve or basilar skull fracture
  • Intracranial tumours at base of frontal lobes - interfere with olfaction
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7
Q

State the function of the optic nerve

A

Vision

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8
Q

State the general optic nerve route from retina

A

Retina -> optic nerve (through optic canal) -> optic chiasm -> optic tract -> primary visual cortex

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9
Q

How can you test for optic nerve

A
  • Test one eye at a time
  • Visual tests - Snellen chart (letters on wall), visual fields
  • Testing pupil responses/reflexes - using pen torches
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10
Q

How can the optic nerve be damaged from increased ICP

A
  • Optic nerve seen directly with ophthalmoscope
  • Optic nerve carry extension of meninges thus nerve can swell due to raised intracranial pressure
    • ICP can be seen as swollen optic disk (papillodema)
    • Optic desk = point at which nerve enters retina
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11
Q

How do lesions at different parts of the route of the optic nerve have different consequences

A
  • Lesions involving the retina or the optic nerve cause visual field disturbance affecting one eye
  • Lesions in the optic chiasm or optic tract involve visual problems in both eyes
  • Pituitary tumours compress optic chiasm, causing bitemporal hemianopia (tunnel vision)
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12
Q

State the nerves that come from the midbrain

A
  • Oculomotor

- Trochlear

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13
Q

What are the functions of the oculomotor nerve

A
  • Motor - most extra-ocular muscles (move eye)
    • Levator palpebrae superioris - opens eyelid
  • Autonomic (parasympathetics) - sphincter pupillae - makes pupil smaller
    - Ciliary muscle - changes lens size
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14
Q

Describe the general route of the oculomotor nerve

A

Midbrain -> cavernous sinus -> superior orbital fissure -> orbit

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15
Q

How is the oculomotor nerve commonly compressed

A
  • Oculomotor nerve lies on the edge of tentorium cerebelli
    • Lies near the uncus, which can slip and squish oculomotor nerve
  • Parasympathetic routes are on the outside and will be compressed first
    • If intracranial pressure increases, pupil control will be compromised first
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16
Q

How do you test the oculomotor nerve

A
  • Inspection of eyelid and pupils
  • Eye movements - (tests III, IV, VI)
  • Pupillary light reflexes
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17
Q

What are signs of symptoms of oculomotor nerve damage

A
  • Pathology can cause pupillary dilation and/or double vision (diplopia)
  • ‘Down and out’ position with severe ptosis (eyelid droops)
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18
Q

What are causes of oculomotor nerve damage

A
  • Raised intracranial pressure (tumour, haemorrhage)
  • Aneurysms
  • Vascular - secondary to diabetes/hypertension - pupil sparing
  • Cavernous sinus thrombosis
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19
Q

State the function of trochlear nerve

A

Motor innervation to superior orbital oblique muscle

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20
Q

Describe the general route of the trochlear nerve and the significance of it

A
  • Posterior midbrain -> cavernous sinus -> superior orbital fissure
  • Only nerve to emerge from dorsal aspect of brainstem - has the longest intracranial distance to travel
    • Higher chance of injury
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21
Q

How do you test trochlear nerve

A

Eye movements

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22
Q

How do patients with trochlear nerve damage present

A
  • Diplopia
  • Rare and often subtle - patients correct the diplopia with tilt of the head
  • Head injury most common cause of injury
  • Congenital palsies in children - vertical misalignment of eyes when looking straight
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23
Q

State the nerves that arise from the pons

A
  • Trigeminal
  • Abducents
  • Facial
  • Vestibulocochlear
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24
Q

State the actions of the trigeminal nerve

A
  • Main sensory nerve of face

- Muscles of mastication

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25
Q

Describe the general route of the branches of the trigeminal nerve

A
  • Ophthalmic (Va) - pons -> superior orbital fissure -> orbit
  • Maxillary (Vb) - pons -> foramen rotundum -> pterygopalatine fossa
  • Mandibular (Vc) - pons -> foramen ovale -> infratemporal fossa
26
Q

How do you test the trigeminal nerve

A
  • Sensation to face - test dermatomal areas of Va, Vb, Vc
  • Muscles of mastication
  • Corneal reflex (afferent limb of corneal reflex)
27
Q

State some conditions involving branches of trigeminal nerve

A
  • Trigeminal neuralgia (mild stimulation of face causes pain)
  • Shingles - sight threatening due to vesicles/scaring on eyelid
  • Corneal ulcer
28
Q

What can happen if the maxillary branch is damaged

A
  • Maxillary nerve -> infraorbital nerve through infraorbital foramen
    • If eye hit, floor of orbit can collapse causing blowout fractured - black eye, bruising
    • Loss of sensation to eye
29
Q

What can happen if the mandibular branch of trigeminal nerve is damaged

A
  • Loss of sensation to lip and teeth

- Fracture -> lip/tongue numbness

30
Q

State the action of abducens nerve

A

Motor innervation to lateral rectus muscle

31
Q

Describe the general route of the abducens nerve

A

Pons -> cavernous sinus -> superior orbital fissure

32
Q

How do you test abducens nerve

A

Testing - eye movements

33
Q

How to patients with abducens nerve damage present

A
  • Clinical points - patients present with diplopia

- Susceptible to injury in raised intracranial pressure as nerve can be easily stretched

34
Q

What are the actions of the facial nerve

A
  • Muscles of facial expression
  • Taste to anterior 2/3 tongue
  • Parasympathetic innervation to lacrimal and salivary gland
35
Q

Describe the general route of facial nerve

A

Pons -> internal auditory meatus -> petrous bone -> branches into different nerves

36
Q

How do you test the facial nerve

A
  • Muscles of facial expression
  • Corneal reflex (efferent limb)
  • Taste
37
Q

How do patients with facial nerve damage present

A

Idiopathic facial nerve palsy - Bell’s palsy

- loss of facial expression to one half of face

38
Q

State the actions of vestibulocochlear nerve

A

Hearing, balance

39
Q

Describe the general route of vestibulocochlear nerve

A

Pons -> internal auditory meatus -> petrous bone -> ear

40
Q

How can the vestibulocochlear nerve be tested

A
  • Test hearing, enquire about balance

- Rinnes Webers test

41
Q

How can damage to vestibulocochlear nerve present

A
  • Damage to cochlea causes hearing loss
  • Presbyacusis - old-age related hearing loss
  • Pathology involving semi-circular canals - disturbance of balance (vertigo) and nystagmus (eye makes uncontrolled movements)
  • Can damage both vestibulo and cochlear parts causing both hearing and balance problems
42
Q

Describe acoustic neuroma and how it presents

A
  • Benign tumour of Schwann cells surrounding vestibulocochlear nerve
    • Compresses whole nerve and other nearby structures
  • Sensorineural hearing loss (hearing loss due to damage of inner ear or vestibulocochlear nerve)
  • Unilateral hearing loss, tinnitus, vertigo, numbness, pain (CN V) or weakness (CN VII) down one half of face
43
Q

State the nerves which arise from the medulla

A
  • Glossopharyngeal
  • Vagus
  • Accessory
  • Hypoglossal
44
Q

State the actions of glossopharyngeal nerve

A
  • General sensation - of soft palate, tonsils and pharynx (oropharynx)
  • Special sensory - middle ear and tympanic membrane
    • Referred pain in ear in sore throat
    • Sensory from carotid body and sinus
    • Taste and general sensation of posterior 1/3 tongue
  • Autonomic - parotid gland
45
Q

Describe the general nerve route of glossopharyngeal nerve

A

Medulla -> jugular foramen -> tongue/pharynx

46
Q

How do you test the glossopharyngeal nerve

A
  • Gag reflex

- Tested in conjunction with CN X

47
Q

State the actions of the vagus nerve

A
  • Sensory to lower pharynx and larynx
  • Muscles of soft palate, pharynx and larynx
    • Swallow (pharynx) and talk (larynx)
  • Parasympathetic to thoracic and abdominal viscera
48
Q

Describe the nerve route of the vagus nerve

A

Medulla -> jugular foramen -> length of neck (carotid sheath) -> abdomen

49
Q

How do you test the vagus nerve

A
  • Noting speech
  • Swallow and cough
  • Say ‘Ahhh’ and observing uvula - should stay in midline
  • Gag reflex
50
Q

How can vagus nerve damage present

A
  • Deviation of the uvula when soft palate elevated when saying ‘Ahhh’
  • Injury to its recurrent laryngeal nerve branch can cause hoarseness and dysphonia
51
Q

State the function of the accessory nerve

A

Innervate SCM and trapezius

52
Q

Describe the general route of the accessory nerve

A

Medulla -> jugular foramen -> muscles

53
Q

How do you test the accessory nerve

A
  • Shrug shoulders against resistance

- Turn head against resistance

54
Q

How is the accessory nerve susceptible to damage

A
  • Spinal accessory runs down through neck in posterior triangle
  • Susceptible to injury in this area - in lymph node biopsies, surgery, stab wound, cancer
55
Q

What is the function of the hypoglossal nerve

A
  • Muscles of the tongue

- Right hypoglossal nerve innervates the right side of the tongue

56
Q

Describe the general nerve route of the hypoglossal nerve

A

Medulla -> hypoglossal canal -> tongue

57
Q

How do you test the hypoglossal nerve

A

Inspection and movement of the tongue

58
Q

How is damage of hypoglossal nerve presented

A
  • Damage to CN XII causes weakness and atrophy of the tongue muscles on ipsilateral side
59
Q

Which cranial nerves travel through superior orbital fissure

A

III, IV, V1, VI

60
Q

Which cranial nerves travel through jugular foramen

A

IX, X, XI

3 - HNN (15 decks)

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