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ESA 4 - Head and Neck > Cranial Nerves > Flashcards

Cranial Nerves Flashcards

1
Q

What does the brainstem adjoin?

A

The brain and the spinal cord

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2
Q

What are the parts of the brainstem?

A
  • Pons
  • Medulla
  • Mid-brain
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3
Q

Is the medulla functionally that different from the spinal cord?

A

Yes, very different

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4
Q

What is the brainstem continuous with caudally?

A

The spinal cord

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5
Q

Where does the brainstem have a vital role?

A

In regulation of cardio-respiratory functions and maintaining consciousness

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6
Q

What runs through brainstem?

A

Ascending and descending fibres between the brain and the rest of the body run through it

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7
Q

What is the brainstem the location of?

A

The majority of cranial nerve nuclei

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8
Q

What are nuclei, in terms of the cranial nerves?

A

Collections of cell bodies of nerve fibres that make up the whole cranial nerve

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9
Q

What are the cranial nerves part of?

A

The peripheral nervous system

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10
Q

Where do the cranial nerves arise from?

A

The central nervous system, at the level of the brainstem, or forebrain in the case of olfactory or optic nerve

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11
Q

How many pairs of cranial nerves are there?

A

12

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12
Q

What does each cranial nerve do?

A

Innervates halves, as they are in pairs

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13
Q

Describe the intervals that the cranial nerves arise from the brainstem (or brain)

A

Irregular intervals from CNS, rather than segments as seen in spinal nerves

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14
Q

What does each cranial nerve have for identification?

A

A roman numeral

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15
Q

What does the numberous of the cranial nerve generally follow?

A

The order in which they arise (or enter) the brainstem, from rostal to caudal

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16
Q

What do cranial nerves carry?

A

1000’s of axons

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17
Q

What are the potential types of axons in cranial nerves?

A
  • General sensory
  • Special sensory
  • Motor
  • Autonomic
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18
Q

How many of the cranial nerves are mixed?

A

Only four

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19
Q

What is meant by a mixed cranial nerve?

A

Contain both motor and sensory modalities

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20
Q

What is the special sense taste carried within?

A

Two of the mixed cranial nerves, mainly CN VII and CN IX

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21
Q

How many of the cranial nerves are purely sensory?

A

3

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22
Q

What do the sensory cranial nerves do?

A

Carry special sensory function, as opposed to general sensation

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23
Q

What cranial nerve is responsible for hearing and balance?

A

CN VIII

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24
Q

What cranial nerve is responsible for vision?

A

CN II

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25
Q

What cranial nerve is responsible for smell?

A

CN I

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26
Q

How many of the cranial nerves are purely motor?

A

5

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27
Q

How many of the cranial nerves carry efferent autonomic fibres?

A

4

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28
Q

Which cranial nerves carry efferent autonomic fibres?

A

CN III, CN VII, CN IX, and CN X

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29
Q

What are the cranial nerves that carry efferent autonomic fibres known as?

A

Visceral motor

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30
Q

What cranial nerve is the most rostal?

A

Olfactory

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31
Q

What is CN I?

A

Olfactory

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32
Q

What route does CN I take?

A

Long nerves dangle down through the cribiform plate, into the olfactory mucosa of the roof of the nasal cavity

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33
Q

What is the sensory function of CN I?

A

Smell

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34
Q

Is CN I motor or sensory?

A

Sensory

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35
Q

How is CN I tested?

A
  • Test one nostril at time
  • Smelling salts, or something quite odouress
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36
Q

Is CN I often formally tested?

A

No, just ask if they have noticed any change/loss in sense of smell

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37
Q

Is CN I a true cranial nerve?

A

No, they are paired extensions of the forebrain

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38
Q

What is the clinical term for loss of smell?

A

Ansomnia

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39
Q

What is the most common cause of ansomnia?

A

Upper respiratory tract infection

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40
Q

How can a head injury cause ansomnia?

A

A bump to the head can cause the brain to wobble, which can produce shearing forces or a basilar skull fracture

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41
Q

What is CN II?

A

Optic nerve

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42
Q

What route does CN II take?

A

Comes from retina, through optic canal. Cross over at the optic chiasms, to optic tracts, to forebrain

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43
Q

Is CN II motor or sensory?

A

Sensory

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44
Q

What is the sensory function of CN II?

A

Vision

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45
Q

How is CN II tested?

A
  • Test one eye at a time
  • Visual tests; visual acuity and visual fields
  • Test pupils
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46
Q

Is CN II a ‘true’ cranial nerve?

A

No, paired anterior extensions of the forebrain

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47
Q

How can CN II be seen directly?

A

With fundoscopy

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48
Q

What is the result of the complex pathway from the retina to the visual cortex of the occipital lobe?

A

Different lesions give very different patterns of visual loss

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49
Q

What can cause lesions of CN II?

A
  • Optic neuritis
  • Pituitary tumour
  • Stroke
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50
Q

What is optic neuritis?

A

Inflammation of optic nerve

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51
Q

What can happen, regarding CN II, when there is a pituitary tumour?

A

Tumours can squash the chiasm, and because of intermingling here, can cause bilateral visual deficit

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52
Q

What is CN III?

A

Oculomotor nerve

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53
Q

What route does CN III take?

A

Passes grom midbrain to the orbit through the superior orbital fissure. Runs through the cavernous sinus

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54
Q

Is CN III motor or sensory?

A

Motor

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55
Q

What is the motor function of CN III?

A
  • Ciliary muscles
  • Sphincter of pupil
  • All extrinsic muscles of the eye, except those supplied by CN IV and VI
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56
Q

How is CN III tested?

A
  • Inspection of the eyelids and pupils
  • Eye movements
  • Pupillary light reflexes
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57
Q

How will a damaged CN III present?

A

Double vision (diplopia), with eye in down and out position, severe ptosis, and maybe pupillary dilation

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58
Q

What can cause CN III lesions?

A
  • Raised intracranial pressure (tumour or haemorrhage)
  • Aneurysms of the posterior communicating artery
  • Cavernous sinus thrombosis from infection or clot
  • Diabetes/hypertension
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59
Q

What is the first sign of raised intracranial pressure?

A

Blown pupil

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60
Q

Why does a blown pupil signify raised intracranial pressure?

A

Superficial parasympathetics run with the oculomotor nerve on the outside, so if pressure exerted from the outside, it affects parasympathetics first. This leads to a loss of sphincter control, and therefore a blown pupil

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61
Q

What CN III lesion will not cause a blown pupil?

A

Diabetes/hypertension

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62
Q

What is CN IV?

A

Trochlear

63
Q

What route does CN IV take?

A

Longest intracranial route of all CN’s

Arises from the dorsal aspect of the brainstem, so moves right around brain and passes through superior orbital fissure

64
Q

Is CN IV motor or sensory?

A

Motor

65
Q

What is the motor function of CN IV?

A

Superior oblique muscles of eye

66
Q

How is CN IV tested?

A

Eye movements

67
Q

Is a CN IV lesion commonly seen isolated?

A

No, rare

68
Q

What is the problem with recognising CN IV lesions?

A

Subtle, as only one muscle affected, so often missed

69
Q

How can the presentation of a CN IV lesion often be corrected?

A

With a slight tilt of the head

70
Q

How does a CN IV lesion present?

A

Diplopia, often worst with downwards gaze

71
Q

What is the most common cause of acute CN IV injury?

A

Head injury, or any cause of raised ICP

72
Q

In whom can congenital palsies of CN IV present?

A

Children

73
Q

What is CN V?

A

Trigeminal

74
Q

What is the route of CN V?

A

Arises from the pons, and gives rise to three divisions;

  • V1, opthalmic, which goes into the eye through the superoir orbital fissure
  • V2, maxillary, which goes through the foramen rotundum
  • V3, mandibular, which goes through the foramen ovale
75
Q

What does the maxillary branch of CN V give off?

A

The intraorbital nerve

76
Q

Where does CN V give off the infraorbital nerve?

A

When it goes through the infra-orbital foramen

77
Q

What does the mandibular branch of CN V give off?

A

The mental nerve

78
Q

Where does CN V give off the mandibular nerve?

A

When it goes through the mental foramen

79
Q

How can the mental nerve be injured?

A

In a fracture of the mandible

80
Q

What does injury of the mental nerve lead to?

A

Loss of sensation in the face

81
Q

Is CN V motor or sensory?

A

Both

82
Q

What is the motor function of CN V?

A

Muscles of mastication

83
Q

What is the sensory function of CN V?

A
  • Face
  • Sinuses
  • Teeth
84
Q

How is CN V tested?

A
  • Sensation to face
  • Muscles of mastication testing
85
Q

What does trigeminal neuralgia cause?

A

Intense pain from very light touch to certain divisions of the trigeminal nerve on the face

86
Q

What clinical condition is CN V implicated in?

A

Shingles

87
Q

What does CN V provide, regarding the eyes?

A

The afferent limb of the corneal reflex

88
Q

What is the function of the corneal reflex?

A

It senses grit etc on your cornea, and causes you to blink

89
Q

What is CN VI?

A

Abducent

90
Q

What course does CN VI take?

A

Arises from the pons, through the cavernous sinus, to the superior orbital fissure

91
Q

Is CN VI motor or sensory?

A

Motor

92
Q

What is the motor function of CN VI?

A

Lateral rectus muscle of the eye

93
Q

How is CN VI tested?

A

Eye movements

94
Q

When is CN VI susceptible to injury?

A

In raised intracranial pressure, e.g. due to bleed or tumour

95
Q

Why is CN VI susceptible to injury in raised intracranial pressure?

A

Due to it running under the surface of the pons upwards towards the cavernous sinus

96
Q

How do patients with CN VI lesions present?

A

Diplopia

97
Q

What is CN VII?

A

Facial nerve

98
Q

What route does CN VII take?

A

Passes into petrous part of temporal bone, goes through the internal acoustic meatus. Through petrous part, gives off branches in the ear. Exits stylomastoid foramen, and gives off 5 terminal branches

99
Q

Is CN VII motor or sensory?

A

Both

100
Q

What is the motor function of CN VII?

A
  • Via it’s primary root-* Muscles of facial expression
  • Via the intermediate nerve-* Submandibular, sublingual, and lacrimal glands
101
Q

What is the sensory function of CN VII?

A
  • Taste to anterior 2/3 of the tongue
  • Soft palate
102
Q

How is CN VII tested?

A
  • Muscles of facial expression
  • Taste to anterior 2/3 of tounge (often not formally tested)
103
Q

Give an example of a facial nerve palsy?

A

Bells palsy

104
Q

What happens in Bells Palsy?

A

Get all muscles of facial expression on one side paralysed, leading to drooping

105
Q

What can cause CN VII palsies?

A

Parotid tumours

106
Q

What is CN VII in close relationship with?

A

Vestibulococlear nerve

107
Q

What is CN VIII?

A

Vestibulocochlear

108
Q

What are the branches of CN VIII?

A
  • Vestibular nerve
  • Cochlear nerve
109
Q

What course does CN VIII take?

A

Goes through internal acoustic meatus, terminates inside the ear. Branches to semi-circular canal and cochlear

110
Q

Is CN VIII motor or sensory?

A

Sensory

111
Q

What is the sensory function of the vestibular branch of CN VII?

A
  • Orientation
  • Motion
112
Q

What is the sensory function of the cochlear branch of CN VII?

A

Hearing

113
Q

How is CN VIII tested?

A
  • Hearing
  • Rinne’s and Weber’s test
114
Q

What pathologies is CN VIII involved in?

A
  • Hearing loss
  • Vertigo
  • Tinnitus
115
Q

What is an acoustic neuroma?

A

A benign tumour of the vestibular cochlear nerve around the internal acoustic meatus

116
Q

What is cranial nerve IX?

A

Glossopharyngeal

117
Q

Is CN IX motor or sensory?

A

Both

118
Q

What is the motor function of CN IX?

A
  • Stylopharyngeus
  • Parotid gland
119
Q

What is the sensory function of CN IX?

A
  • Posterior 1/3 of tongue
  • General sensation to pharynx, tonsillar fossa, and pharyngotympanic tube
  • Middle ear cavity
  • Carotid sinus
120
Q

Where is the carotid sinus found?

A

In the internal carotid artery

121
Q

What does the carotid sinus possess?

A

Baroreceptors that are sensitive to changes in blood pressure

122
Q

What does the carotid body possess?

A

Chemoreceptors

123
Q

What are the chemoreceptors in the carotid body sensitive to?

A

Blood and oxygen carbon dioxide levels

124
Q

What happens when chemoreceptors in the carotid body sense a change in blood oxygen and carbon dioxide?

A

Afferent signals are sent via CN IX to cardiorespiratory centres in the medulla

125
Q

How is CN IX tested?

A

Gag reflex (tests sensory limb) ​

  • Taste often not formally tested.*
  • Tested in conjunction with CN X*
126
Q

Are isolated lesions of CN IX common?

A

No, rare

127
Q

What is CN X?

A

Vagus nerve

128
Q

What course does CN X take?

A

Exits skull through jugular foramen, goes into carotid sheath, and down the neck

129
Q

Is CN X motor or sensory?

A

Both

130
Q

What is the motor function of CN X?

A
  • Larynx
  • Trachea
  • Bronchial tree
  • GI tract to left colic flexure
131
Q

What is the sensory function of CN X?

A
  • Pharynx
  • Larynx
  • Reflex sensory from tracheobronchial tree
  • Lungs
  • Heart
  • GI tract to left colic flexure
132
Q

How is CN X tested?

A
  • Noting speech
  • Swallow
  • Cough
  • Gag reflex (efferent limb)
133
Q

Are isolated lesions of CN X common?

A

No, rare

134
Q

What is the clinical sign of isolated CN X lesions?

A

Deviation of the uvula when soft palate elevated

135
Q

What can injury to the recurrent laryngeal nerve cause?

A

Hoarseness and dysphonia

136
Q

What is CN XI?

A

Spinal accessory nerve

137
Q

What route does the spinal accessory nerve take?

A

Through jugular foramen

138
Q

Is the spinal accessory nerve motor or sensory?

A

Motor

139
Q

By what branches does the spinal accessory nerve give its motor supply?

A
  • Spinal root
  • Cranial route
140
Q

What is the motor function of the spinal root of CN XI?

A
  • Sternocleidomastoid
  • Trapezius
141
Q

What are the motor functions of the cranial root of CN XI?

A

Most palantine and pharyngeal muscles

142
Q

How is CN XI tested?

A
  • Shrug shoulders
  • Turn head against resistance
143
Q

Where does CN XI recieve its spinal roots from?

A

Upper 5/6 cervical segments

144
Q

How to spinal nerve roots from the upper 5/6 cervical segments contribute to CN XI?

A

Ascend up foramen magnum to join cranial root

145
Q

Where does CN XI run down the neck?

A

Through the posterior triangle

146
Q

What is the result of CN XI running down the neck through the posterior triangle?

A

It’s susceptible to injury in this area

147
Q

How can CN XI be injured in the posterior triangle?

A
  • Lymph node biopsies
  • Stab wounds
148
Q

What is CN XII?

A

Hypoglossal nerve

149
Q

What route does CN XII take?

A

Leaves medulla through hypoglossal canal

150
Q

Is CN XII motor or sensory?

A

Motor

151
Q

What is the motor function of CN XII?

A

All intrinsic muscles of tongue, except palatoglossus

152
Q

How is CN XII tested?

A

Inspection and movement of the tongue

153
Q

What does damage to CN XII cause?

A

Weakness and atrophy of the tongue muscles on the ipsilateral side

ESA 4 - Head and Neck (30 decks)

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