Cranial Nerves Flashcards

1
Q

What are the 3 regions of the brainstem?

A

Midbrain
Pons
Medulla

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2
Q

What are nuclei in the brain?

A

Collections of the cell bodies of nerve fibres

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3
Q

How many cranial nerves arise from the brain itself (forebrain)?

A

2

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4
Q

How many cranial nerves arise from the midbrain?

A

2

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5
Q

How many cranial nerves arise from the pons?

A

4

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6
Q

How many cranial nerves arise from the medlla?

A

4

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7
Q

What is the mneumonic to help remember how many cranial nerves arise from different regions of the brain/brainstem?

A

2, 2, 4, 4

2 arise from forebrain
2 arise from midbrain
4 arise from pons
4 arise from medulla

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8
Q

Which 2 cranial nerves arise from the forebrain?

A

Olfactory and optic

CN I and II

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9
Q

How many cranial nerves arise from the brainstem?

A

10 (III- XII)

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10
Q

What kind of information does the olfactory nerve transmit?

A

Special sensory

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11
Q

What is the function of the olfactory nerve?

A

Smell

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12
Q

What is the route and relation of the olfactory nerve to the CNS?

A

Olfactory nerve -> cribiform foramina -> olfactory bulb -> olfactory tracts -> forebrain

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13
Q

What is anosmia?

A

The absence of the sense of smell

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14
Q

What skull base cavity does the olfactory nerve (CN I) travel through?

A

Crimiform foramina of cribiform plate

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15
Q

What is the target tissue of the olfactory nerve?

A

Mucosal membrane roof of nasal cavity

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16
Q

How is the olfactory nerve tested?

A

Enquiry about sense of smell, smelling salts

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17
Q

What kind of information does the optic nerve transmit?

A

Special sensory

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18
Q

What skull base cavity does the optic nerve (CN II) pass through?

A

Optic canal

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19
Q

What does the anatomical course of the optic nerve describe?

A

Transmission of special sensory information from the retina to the primary visual cortex

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20
Q

What happens at the optic chiasm?

A

Optic nerves cross over

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21
Q

What is the point at which the optic nerve enters the retina?

A

Optic disc

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22
Q

Why can the optic nerve swell due to raised ICP?

A

Carry extension of meninges - can see evidence of raised ICP on fundoscopy as a swollen optic disc

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23
Q

What would lesions involving the retina or the optic nerve cause?

A

Visual disturbance affecting only one eye

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24
Q

Where is the primary visual cortex?

A

Occipital lobe

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25
Q

Why do pituitary tumours cause bilateral visual symptoms?

A

Compress optic chiasm - both eyes affected

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26
Q

What does the pituitary gland lie in close proximity to?

A

Optic chiasm (in middle cranial fossa)

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27
Q

What would a patient with bitemporal hemianopia describe?

A

Tunnel vision (visual defect affecting the peripheral vision in both eyes)

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28
Q

In which bone is the optic chiasm?

A

Sphenoid

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29
Q

Which two cranial nerves arise from the midbrain?

A

Oculomotor and Trochlear

CN III and IV

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30
Q

What kind of information does the oculomotor nerve (CN III) transmit?

A

Motor and autonomic (parasympathetic)

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31
Q

What motor function does the oculomotor nerve serve?

A

Innervates most extraocular muscles

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32
Q

What do the autonomic components of the oculomotor nerve do?

A

Supplies sphincter pupillae (pupil) and ciliary muscle (lens)

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33
Q

What are the functions of the oculomotor nerve?

A

Eye movements, pupil constriction, eyelid opening

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34
Q

What foramen does the oculomotor nerve (CN III) pass through?

A

Superior orbital fissure

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35
Q

Describe the route of the oculomotor nerve

A

From the midbrain, runs through lateral wall of cavernous sinus, exits through the SOF, into orbit

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36
Q

What are the three main causes of an oculomotor nerve lesion?

A

1) Increasing ICP - uncus can squish tentorium cerebelli and thus CN III which is in close proximity
2) Aneurysm of the posterior cerebral artery
3) Cavernous sinus infection or trauma

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37
Q

Why can cavernous sinus infection cause damage to CN III?

A

Oculomotor nerve runs through the lateral wall of the cavernous sinus

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38
Q

What are the clinical signs of CN III injury?

A

Oculomotor nerve lesion

1) ptosis - due to paralysis of levator pulpabrae superioris
2) eyeball is down and out - paralysis of rectus muscles and inferior oblique
3) dilated pupil - due to unopposed action of dilator pupillae (can’t costrict)

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39
Q

How is CN III tested?

A

Inspection of eyelid and pupils, eye movements, pupillary light reflexes

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40
Q

What kind of information is transmitted by the trochlear nerve (CN IV)?

A

Motor

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41
Q

What is the only nerve to emerge from the dorsal aspect of the brainstem?

A

Trochlear (CN IV)

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42
Q

Which cranial nerve has the longest intracranial course?

A

Trochlear (CN IV)

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43
Q

Describe the course of the trochlear nerve

A

Arises from posterior aspect of midbrain, runs within the subarachnoid space, moves along lateral wall of cavernous sinus, enters orbit of eye via the SOF

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44
Q

Which foramen does the trochlear nerve pass through?

A

Superior orbital fissure

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45
Q

What single muscle does the trochlear nerve innervate?

A

Superior oblique

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46
Q

What is the function of the trochlear nerve?

A

Innervates one extraorbital muscle - superior oblique

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47
Q

What is the overall action of the superior oblique?

A

Depress and intort the eyeball

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48
Q

How is the trochlear nerve examined?

A

By testing movements of the eye (eg patient asked to follow a point with their eyes without moving their head)

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49
Q

What is diplopia?

A

Double vision

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50
Q

How does trochlear nerve palsy present?

A

Vertical diplopia - exacerbated by looking down and in

Patients can also develop a head tilt away from affected side

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51
Q

Which four cranial nerves arise from the pons?

A

Trigeminal (CN V)
Abducens (CN VI)
Facial (CN VII)
Vestibulocochear (VIII)

52
Q

What is the largest cranial nerve?

A

Trigeminal (CN V)

53
Q

What kind of information does the trigeminal nerve transmit?

A

Sensory (all 3 branches) and motor (mandibular branch)

54
Q

Which branch of the trigeminal nerve has motor fibres?

A

Mandibular

55
Q

What is the motor function of the trigeminal nerve?

A

Mandibular nerve innervates muscles of mastication

56
Q

What is the sensory function of the trigeminal nerve?

A

All branches innervate the skin, mucous membranes and sinuses of the face

57
Q

Which foramen does the opthalmic branch of the trigeminal nerve pass through?

A

Superior orbital fissure

58
Q

Which foramen does the maxillary branch of the trigeminal nerve pass through?

A

Foramen rotundum

59
Q

Which foramen does the mandibular branch of the trigeminal nerve pass through?

A

Foramen ovale

60
Q

What nerve is responsible for the afferent limb of the corneal reflex?

A

Opthalmic division of the trigeminal nerve (detects the stimuli)

61
Q

What is the corneal reflex?

A

Involuntary blinking of the eyelids - stimulated by tactile, thermal or painful stimulation of the cornea

62
Q

What nerve is responsible for the efferent limb of the corneal reflex?

A

Facial nerve (contraction of orbicularis ocli muscle)

63
Q

What is an absent corneal reflex a sign of?

A

Opthalmic/trigeminal or facial nerve damage

64
Q

What are the four terminal branches of the mandibular nerve?

A

Mandibular nerve is a division of the trigeminal nerve

Its terminal branches are:

1) buccal nerve
2) inferior alveolar nerve
3) auriculotemporal nerve
4) lingual nerve

65
Q

What are the three terminal branches of the opthalmic nerve?

A

Opthalmic nerve is a division of the trigeminal nerve

Its terminal branches are:

1) frontal
2) lacrimal
3) nasociliary

66
Q

Describe the sensory supply of the mandibular nerve

A
Mucous membranes and floor of oral cavity
External ear
Lower lip
Chin
Anterior 2/3 of tongue (ONLY SENSATION)
Lower molar, incisor and canine teeth
67
Q

Describe the sensory supply of the opthalmic nerve

A
Forehead and scalp
Frontal and ethmoidal sinus
Upper eyelid and conjunctiva
Cornea
Dorsum of nose
68
Q

Describe the motor supply of the mandibular nerve

A

Muscles of mastication

69
Q

Describe the sensory supply of the maxillary nerve

A
Lower eyelid and conjunctiva
Cheeks, maxillary sinus
Nasal cavity
Lateral nose
Upper lip
Upper molar, incisor and canine teeth
Superior palate
70
Q

What does the inferior alveolar nerve (a branch of mandibular nerve) travel through?

A

Mandibular foramen

71
Q

What nerve is injured in a blow out fracture?

A

Infraorbital nerve (branch of maxillary division of trigeminal nerve)

72
Q

What does the inferior alveolar nerve emerge as to give sensation to the lip and chin?

A

Mental nerve

73
Q

What nerve can be damaged in a fractured mandible?

A

Inferior alveolar/mental nerve

74
Q

What kind of information does the abducens nerve transmit?

A

Motor

75
Q

What muscle is innervated by the abducens nerve?

A

Lateral rectus

76
Q

What is the action of the lateral rectus?

A

Abduction of the eyeball

77
Q

What presentations could a trigeminal nerve lesion cause?

A

Loss of corneal reflex

Loss of facial sensation

Paralysis of muscles of mastication

78
Q

What foramen does the abducens nerve pass through?

A

Superior orbital fissure

79
Q

What does abducens nerve palsy result in?

A

Horizontal diplopia - defective abduction

80
Q

What is the route of the abducens nerve?

A

Comes from bottom of pons, through cavernous sinus, through SOF, supplies one muscle of the eye

81
Q

What nerves are tested when examining eye movements?

A

CN III, IV and VI

82
Q

What kind of information is transmitted by the facial nerve?

A
Motor (muscles of facial expression)
Special sensory (taste to anterior 2/3 of tongue)
Parasympathetic (salivary glands, nasal glands, lacrimal glands)
83
Q

What special sensory function does the facial nerve serve?

A

Taste to anterior 2/3 of tongue

84
Q

What motor function does the facial nerve serve?

A

Muscles of facial expression

85
Q

What autonomic function does the facial nerve serve?

A

Parasympathetic

Salivary glands, lacrimal glands

86
Q

What foramen does the facial nerve pass through?

A

Internal auditory meatus

87
Q

Briefly outline the route of the facial nerve

A

Comes from pons, runs through petrous part of temporal bone by going through IAM, gives off a couple of branches inside the petrous bone before exiting through base of skull and giving off its 5 extracranial nerves (TZBMC)

88
Q

What are the 5 extracranial branches of the facial nerve?

A

Temporal, zygomatic, buccal, mandibular, cervical

89
Q

Why would someone with a facial nerve lesion present with hyperacousis?

A

Injury to nerve to stapedius (which dampens noise)

90
Q

What is the branch of the facial nerve that gives special sensory fibres to the anterior 2/3 of the tongue?

A

Chorda tympani

91
Q

Which branch of the facial nerve gives parasympathetic fibres to glands?

A

Greater petrosal nerve

92
Q

What is the most common cause of an intracranial lesion of the facial nerve?

A

Middle ear pathology

93
Q

In extracranial lesions, which function of the facial nerve is affected?

A

Motor function - so paralysis of muscles of facial expression

94
Q

What is idiopathic facial nerve palsy known as?

A

Bell’s palsy

95
Q

What are some causes of extracranial lesions of the facial nerve?

A

Parotid gland pathology (closely related), infection of the nerve, compression, idiopathic

96
Q

Which foramen does the vestibulocochlear nerve go through?

A

Internal auditory meatus

97
Q

What kind of information does the vestibulocochlear nerve transmit?

A

Special sensory (hearing and balance)

98
Q

Where is the primary auditory cortex?

A

Temporal lobe

99
Q

What is an acoustic neuroma?

A

Benign tumour of the schwann cells surrounding the vestibular component of CN VIII

100
Q

What are the four cranial nerves that arise from the medulla?

A

Glossopharyngeal (IX)
Vagus (X)
Accessory (XI)
Hypoglossal (XII)

101
Q

What kind of information is transmitted by the glossopharyngeal nerve?

A

General sensory - innervation of oropharynx, posterior 1/3 of tongue, middle ear cavity

Special sensory - taste to posterior 1/3 of tongue

Parasympathetic - parotid gland

Motor - stylopharyngeus

102
Q

What is the motor function of the glossopharyngeal nerve?

A

Innervates stylopharyngeus

103
Q

What nerve is responsible for the sensory limb of the gag reflex?

A

Glossopharyngeal

104
Q

What is the autonomic function of the glossopharyngeal nerve?

A

Parotid gland innervation

105
Q

How is the glossopharyngeal nerve tested?

A

Gag reflex, tested in conjunction with CN X

106
Q

What foramen does the glossopharyngeal nerve pass through?

A

Jugular foramen

107
Q

What may glossopharyngeal nerve lesions result in?

A

Hypersensitive carotid sinus reflex

Loss of gag reflex (afferent)

108
Q

What carries the afferent limb of the gag reflex?

A

Glossopharyngeal nerve

109
Q

What carries the efferent limb of the gag reflex?

A

Vagus nerve

110
Q

What kind of information is transmitted by the vagus nerve?

A

General sensory - lower pharynx and larynx

Motor - muscles of the soft palate, pharynx, larynx

Parasympathetic - thoracic and abdominal viscera

111
Q

What foramen does the vagus nerve pass through to exit the skull?

A

Jugular foramen

112
Q

Describe the route of the vagus nerve

A

Comes from medulla, exits skull through jugular foramen, stays in carotid sheath, runs down length of neck behind artery and vein in carotid sheath, gives off branches in neck, continues into thorax and abdomen

113
Q

What does the right recurrent laryngeal nerve hook underneath?

A

Right subclavian artery

114
Q

What does the left recurrent laryngeal nerve hook underneath?

A

The arch of the aorta

115
Q

How may a patient with vagus nerve lesions present?

A
  • Uvula deviation away from site of lesion

- Loss of gag reflex

116
Q

What foramen does the accessory nerve pass through?

A

Jugular foramen

117
Q

What kind of information is transmitted by the accessory nerve?

A

Motor

118
Q

What is the function of the accessory nerve?

A

Supplies trapezius and SCM

119
Q

How can the accessory nerve be tested?

A

Shrug shoulders against resistance, turn head against resistance

120
Q

What does the spinal accessory nerve run down through the neck in?

A

Posterior triangle - susceptible to injury in this area

121
Q

What kind of information does the hypoglossal nerve transmit?

A

Motor

122
Q

What is the function of the hypoglossal nerve?

A

Innervates muscles of the tongue

123
Q

What foramen does the hypoglossal nerve pass through?

A

Hypoglossal canal (on rim of foramen magnum)

124
Q

What may be seen in a patient with hypoglossal nerve damage?

A

Weakened tongue

Tongue may deviate towards side of lesion

125
Q

Which cranial nerves could be affected by cavernous sinus thrombosis?

A

Oculomotor, trochlear, trigeminal (Va and Vb) and abducens