Cranial Nerves Flashcards Preview

ESA 4 - Head and Neck > Cranial Nerves > Flashcards

Flashcards in Cranial Nerves Deck (153):
1

What does the brainstem adjoin? 

The brain and the spinal cord

2

What are the parts of the brainstem? 

  • Pons
  • Medulla
  • Mid-brain

 

3

Is the medulla functionally that different from the spinal cord? 

Yes, very different

4

What is the brainstem continuous with caudally? 

The spinal cord

5

Where does the brainstem have a vital role? 

In regulation of cardio-respiratory functions and maintaining consciousness

6

What runs through brainstem? 

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

7

What is the brainstem the location of? 

The majority of cranial nerve nuclei 

8

What are nuclei, in terms of the cranial nerves? 

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

9

What are the cranial nerves part of? 

The peripheral nervous system

10

Where do the cranial nerves arise from? 

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

11

How many pairs of cranial nerves are there? 

12

12

What does each cranial nerve do? 

Innervates halves, as they are in pairs 

13

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

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

14

What does each cranial nerve have for identification? 

A roman numeral 

15

What does the numberous of the cranial nerve generally follow? 

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

16

What do cranial nerves carry? 

1000's of axons

17

What are the potential types of axons in cranial nerves? 

  • General sensory
  • Special sensory
  • Motor 
  • Autonomic

18

How many of the cranial nerves are mixed? 

Only four 

19

What is meant by a mixed cranial nerve? 

Contain both motor and sensory modalities 

20

What is the special sense taste carried within? 

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

21

How many of the cranial nerves are purely sensory? 

3

22

What do the sensory cranial nerves do? 

Carry special sensory function, as opposed to general sensation 

23

What cranial nerve is responsible for hearing and balance? 

CN VIII

24

What cranial nerve is responsible for vision? 

CN II

25

What cranial nerve is responsible for smell? 

CN I

26

How many of the cranial nerves are purely motor? 

5

27

How many of the cranial nerves carry efferent autonomic fibres? 

4

28

Which cranial nerves carry efferent autonomic fibres? 

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

29

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

Visceral motor

30

What cranial nerve is the most rostal? 

Olfactory

31

What is CN I? 

Olfactory 

32

What route does CN I take? 

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

33

What is the sensory function of CN I? 

Smell

34

Is CN I motor or sensory? 

Sensory

35

How is CN I tested? 

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

 

36

Is CN I often formally tested? 

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

37

Is CN I a true cranial nerve? 

No, they are paired extensions of the forebrain 

 

38

What is the clinical term for loss of smell? 

Ansomnia

39

What is the most common cause of ansomnia? 

Upper respiratory tract infection 

40

How can a head injury cause ansomnia? 

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

41

What is CN II? 

Optic nerve

42

What route does CN II take? 

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

43

Is CN II motor or sensory? 

Sensory 

44

What is the sensory function of CN II? 

Vision

45

How is CN II tested? 

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

 

46

Is CN II a 'true' cranial nerve? 

No, paired anterior extensions of the forebrain 

47

How can CN II be seen directly? 

With fundoscopy

48

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

Different lesions give very different patterns of visual loss 

49

What can cause lesions of CN II? 

  • Optic neuritis
  • Pituitary tumour
  • Stroke

50

What is optic neuritis? 

Inflammation of optic nerve

51

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

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

52

What is CN III? 

Oculomotor nerve

53

What route does CN III take? 

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

54

Is CN III motor or sensory? 

Motor

55

What is the motor function of CN III? 

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

 

56

How is CN III tested? 

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

 

57

How will a damaged CN III present? 

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

58

What can cause CN III lesions?

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

 

59

What is the first sign of raised intracranial pressure? 

Blown pupil 

60

Why does a blown pupil signify raised intracranial pressure? 

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 

61

What CN III lesion will not cause a blown pupil? 

Diabetes/hypertension

62

What is CN IV? 

Trochlear

63

What route does CN IV take? 

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

Is CN IV motor or sensory? 

Motor

65

What is the motor function of CN IV? 

Superior oblique muscles of eye 

66

How is CN IV tested? 

Eye movements

67

Is a CN IV lesion commonly seen isolated? 

No, rare

68

What is the problem with recognising CN IV lesions? 

Subtle, as only one muscle affected, so often missed

 

69

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

With a slight tilt of the head

70

How does a CN IV lesion present? 

Diplopia, often worst with downwards gaze

71

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

Head injury, or any cause of raised ICP

72

In whom can congenital palsies of CN IV present? 

Children

73

What is CN V? 

Trigeminal

74

What is the route of CN V? 

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

What does the maxillary branch of CN V give off? 

The intraorbital nerve

76

Where does CN V give off the infraorbital nerve? 

When it goes through the infra-orbital foramen 

77

What does the mandibular branch of CN V give off? 

The mental nerve

78

Where does CN V give off the mandibular nerve? 

When it goes through the mental foramen

79

How can the mental nerve be injured? 

In a fracture of the mandible

80

What does injury of the mental nerve lead to? 

Loss of sensation in the face

81

Is CN V motor or sensory? 

Both 

82

What is the motor function of CN V? 

Muscles of mastication 

83

What is the sensory function of CN V? 

  • Face
  • Sinuses 
  • Teeth

 

84

How is CN V tested? 

  • Sensation to face
  • Muscles of mastication testing

 

85

What does trigeminal neuralgia cause? 

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

86

What clinical condition is CN V implicated in? 

Shingles

87

What does CN V provide, regarding the eyes? 

The afferent limb of the corneal reflex

88

What is the function of the corneal reflex? 

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

89

What is CN VI? 

Abducent 

90

What course does CN VI take? 

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

91

Is CN VI motor or sensory?

Motor

92

What is the motor function of CN VI?

Lateral rectus muscle of the eye 

93

How is CN VI tested?

Eye movements

94

When is CN VI susceptible to injury?

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

95

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

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

96

How do patients with CN VI lesions present?

Diplopia

97

What is CN VII?

Facial nerve

98

What route does CN VII take?

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

Is CN VII motor or sensory? 

Both 

100

What is the motor function of CN VII? 

Via it's primary root- Muscles of facial expression

Via the intermediate nerve- Submandibular, sublingual, and lacrimal glands

101

What is the sensory function of CN VII? 

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

 

102

How is CN VII tested? 

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

103

Give an example of a facial nerve palsy? 

Bells palsy

104

What happens in Bells Palsy? 

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

105

What can cause CN VII palsies? 

Parotid tumours

106

What is CN VII in close relationship with? 

Vestibulococlear nerve

107

What is CN VIII? 

Vestibulocochlear

108

What are the branches of CN VIII? 

  • Vestibular nerve
  • Cochlear nerve

109

What course does CN VIII take?

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

110

Is CN VIII motor or sensory? 

Sensory

111

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

  • Orientation 
  • Motion

112

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

Hearing

113

How is CN VIII tested? 

  • Hearing
  • Rinne's and Weber's test

 

114

What pathologies is CN VIII involved in? 

  • Hearing loss
  • Vertigo 
  • Tinnitus

 

115

What is an acoustic neuroma? 

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

116

What is cranial nerve IX? 

Glossopharyngeal 

117

Is CN IX motor or sensory? 

Both

118

What is the motor function of CN IX? 

  • Stylopharyngeus 
  • Parotid gland

119

What is the sensory function of CN IX? 

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

120

Where is the carotid sinus found? 

In the internal carotid artery 

121

What does the carotid sinus possess? 

Baroreceptors that are sensitive to changes in blood pressure

122

What does the carotid body possess? 

Chemoreceptors

123

What are the chemoreceptors in the carotid body sensitive to? 

Blood and oxygen carbon dioxide levels

124

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

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

125

How is CN IX tested? 

Gag reflex (tests sensory limb) 

Taste often not formally tested. 

Tested in conjunction with CN X

126

Are isolated lesions of CN IX common? 

No, rare

127

What is CN X? 

Vagus nerve

128

What course does CN X take? 

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

129

Is CN X motor or sensory? 

Both 

130

What is the motor function of CN X? 

  • Larynx
  • Trachea
  • Bronchial tree
  • GI tract to left colic flexure

 

131

What is the sensory function of CN X? 

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

 

132

How is CN X tested? 

  • Noting speech
  • Swallow
  • Cough
  • Gag reflex (efferent limb) 

 

133

Are isolated lesions of CN X common? 

No, rare

134

What is the clinical sign of isolated CN X lesions? 

Deviation of the uvula when soft palate elevated

135

What can injury to the recurrent laryngeal nerve cause? 

Hoarseness and dysphonia

136

What is CN XI? 

Spinal accessory nerve

137

What route does the spinal accessory nerve take? 

Through jugular foramen

138

Is the spinal accessory nerve motor or sensory? 

Motor

139

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

  • Spinal root
  • Cranial route

 

140

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

  • Sternocleidomastoid
  • Trapezius

 

141

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

Most palantine and pharyngeal muscles

142

How is CN XI tested?

  • Shrug shoulders
  • Turn head against resistance

 

143

Where does CN XI recieve its spinal roots from? 

Upper 5/6 cervical segments

144

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

Ascend up foramen magnum to join cranial root

145

Where does CN XI run down the neck? 

Through the posterior triangle

146

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

It's susceptible to injury in this area

147

How can CN XI be injured in the posterior triangle? 

  • Lymph node biopsies
  • Stab wounds

 

148

What is CN XII? 

Hypoglossal nerve

149

What route does CN XII take? 

Leaves medulla through hypoglossal canal 

150

Is CN XII motor or sensory? 

Motor

151

What is the motor function of CN XII? 

All intrinsic muscles of tongue, except palatoglossus

152

How is CN XII tested? 

Inspection and movement of the tongue

153

What does damage to CN XII cause? 

Weakness and atrophy of the tongue muscles on the ipsilateral side