Cranial Nerves Flashcards
(125 cards)
1
Q
What are the 3 regions of the brainstem?
A
Midbrain
Pons
Medulla
2
Q
What are nuclei in the brain?
A
Collections of the cell bodies of nerve fibres
3
Q
How many cranial nerves arise from the brain itself (forebrain)?
A
2
4
Q
How many cranial nerves arise from the midbrain?
A
2
5
Q
How many cranial nerves arise from the pons?
A
4
6
Q
How many cranial nerves arise from the medlla?
A
4
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
8
Q
Which 2 cranial nerves arise from the forebrain?
A
Olfactory and optic
CN I and II
9
Q
How many cranial nerves arise from the brainstem?
A
10 (III- XII)
10
Q
What kind of information does the olfactory nerve transmit?
A
Special sensory
11
Q
What is the function of the olfactory nerve?
A
Smell
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
13
Q
What is anosmia?
A
The absence of the sense of smell
14
Q
What skull base cavity does the olfactory nerve (CN I) travel through?
A
Crimiform foramina of cribiform plate
15
Q
What is the target tissue of the olfactory nerve?
A
Mucosal membrane roof of nasal cavity
16
Q
How is the olfactory nerve tested?
A
Enquiry about sense of smell, smelling salts
17
Q
What kind of information does the optic nerve transmit?
A
Special sensory
18
Q
What skull base cavity does the optic nerve (CN II) pass through?
A
Optic canal
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
20
Q
What happens at the optic chiasm?
A
Optic nerves cross over
21
Q
What is the point at which the optic nerve enters the retina?
A
Optic disc
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
23
Q
What would lesions involving the retina or the optic nerve cause?
A
Visual disturbance affecting only one eye
24
Q
Where is the primary visual cortex?
A
Occipital lobe
25
Why do pituitary tumours cause bilateral visual symptoms?
Compress optic chiasm - both eyes affected
26
What does the pituitary gland lie in close proximity to?
Optic chiasm (in middle cranial fossa)
27
What would a patient with bitemporal hemianopia describe?
Tunnel vision (visual defect affecting the peripheral vision in both eyes)
28
In which bone is the optic chiasm?
Sphenoid
29
Which two cranial nerves arise from the midbrain?
Oculomotor and Trochlear
| CN III and IV
30
What kind of information does the oculomotor nerve (CN III) transmit?
Motor and autonomic (parasympathetic)
31
What motor function does the oculomotor nerve serve?
Innervates most extraocular muscles
32
What do the autonomic components of the oculomotor nerve do?
Supplies sphincter pupillae (pupil) and ciliary muscle (lens)
33
What are the functions of the oculomotor nerve?
Eye movements, pupil constriction, eyelid opening
34
What foramen does the oculomotor nerve (CN III) pass through?
Superior orbital fissure
35
Describe the route of the oculomotor nerve
From the midbrain, runs through lateral wall of cavernous sinus, exits through the SOF, into orbit
36
What are the three main causes of an oculomotor nerve lesion?
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
37
Why can cavernous sinus infection cause damage to CN III?
Oculomotor nerve runs through the lateral wall of the cavernous sinus
38
What are the clinical signs of CN III injury?
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)
39
How is CN III tested?
Inspection of eyelid and pupils, eye movements, pupillary light reflexes
40
What kind of information is transmitted by the trochlear nerve (CN IV)?
Motor
41
What is the only nerve to emerge from the dorsal aspect of the brainstem?
Trochlear (CN IV)
42
Which cranial nerve has the longest intracranial course?
Trochlear (CN IV)
43
Describe the course of the trochlear nerve
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
44
Which foramen does the trochlear nerve pass through?
Superior orbital fissure
45
What single muscle does the trochlear nerve innervate?
Superior oblique
46
What is the function of the trochlear nerve?
Innervates one extraorbital muscle - superior oblique
47
What is the overall action of the superior oblique?
Depress and intort the eyeball
48
How is the trochlear nerve examined?
By testing movements of the eye (eg patient asked to follow a point with their eyes without moving their head)
49
What is diplopia?
Double vision
50
How does trochlear nerve palsy present?
Vertical diplopia - exacerbated by looking down and in
Patients can also develop a head tilt away from affected side
51
Which four cranial nerves arise from the pons?
Trigeminal (CN V)
Abducens (CN VI)
Facial (CN VII)
Vestibulocochear (VIII)
52
What is the largest cranial nerve?
Trigeminal (CN V)
53
What kind of information does the trigeminal nerve transmit?
Sensory (all 3 branches) and motor (mandibular branch)
54
Which branch of the trigeminal nerve has motor fibres?
Mandibular
55
What is the motor function of the trigeminal nerve?
Mandibular nerve innervates muscles of mastication
56
What is the sensory function of the trigeminal nerve?
All branches innervate the skin, mucous membranes and sinuses of the face
57
Which foramen does the opthalmic branch of the trigeminal nerve pass through?
Superior orbital fissure
58
Which foramen does the maxillary branch of the trigeminal nerve pass through?
Foramen rotundum
59
Which foramen does the mandibular branch of the trigeminal nerve pass through?
Foramen ovale
60
What nerve is responsible for the afferent limb of the corneal reflex?
Opthalmic division of the trigeminal nerve (detects the stimuli)
61
What is the corneal reflex?
Involuntary blinking of the eyelids - stimulated by tactile, thermal or painful stimulation of the cornea
62
What nerve is responsible for the efferent limb of the corneal reflex?
Facial nerve (contraction of orbicularis ocli muscle)
63
What is an absent corneal reflex a sign of?
Opthalmic/trigeminal or facial nerve damage
64
What are the four terminal branches of the mandibular nerve?
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
What are the three terminal branches of the opthalmic nerve?
Opthalmic nerve is a division of the trigeminal nerve
Its terminal branches are:
1) frontal
2) lacrimal
3) nasociliary
66
Describe the sensory supply of the mandibular nerve
```
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
Describe the sensory supply of the opthalmic nerve
```
Forehead and scalp
Frontal and ethmoidal sinus
Upper eyelid and conjunctiva
Cornea
Dorsum of nose
```
68
Describe the motor supply of the mandibular nerve
Muscles of mastication
69
Describe the sensory supply of the maxillary nerve
```
Lower eyelid and conjunctiva
Cheeks, maxillary sinus
Nasal cavity
Lateral nose
Upper lip
Upper molar, incisor and canine teeth
Superior palate
```
70
What does the inferior alveolar nerve (a branch of mandibular nerve) travel through?
Mandibular foramen
71
What nerve is injured in a blow out fracture?
Infraorbital nerve (branch of maxillary division of trigeminal nerve)
72
What does the inferior alveolar nerve emerge as to give sensation to the lip and chin?
Mental nerve
73
What nerve can be damaged in a fractured mandible?
Inferior alveolar/mental nerve
74
What kind of information does the abducens nerve transmit?
Motor
75
What muscle is innervated by the abducens nerve?
Lateral rectus
76
What is the action of the lateral rectus?
Abduction of the eyeball
77
What presentations could a trigeminal nerve lesion cause?
Loss of corneal reflex
Loss of facial sensation
Paralysis of muscles of mastication
78
What foramen does the abducens nerve pass through?
Superior orbital fissure
79
What does abducens nerve palsy result in?
Horizontal diplopia - defective abduction
80
What is the route of the abducens nerve?
Comes from bottom of pons, through cavernous sinus, through SOF, supplies one muscle of the eye
81
What nerves are tested when examining eye movements?
CN III, IV and VI
82
What kind of information is transmitted by the facial nerve?
```
Motor (muscles of facial expression)
Special sensory (taste to anterior 2/3 of tongue)
Parasympathetic (salivary glands, nasal glands, lacrimal glands)
```
83
What special sensory function does the facial nerve serve?
Taste to anterior 2/3 of tongue
84
What motor function does the facial nerve serve?
Muscles of facial expression
85
What autonomic function does the facial nerve serve?
Parasympathetic
Salivary glands, lacrimal glands
86
What foramen does the facial nerve pass through?
Internal auditory meatus
87
Briefly outline the route of the facial nerve
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
What are the 5 extracranial branches of the facial nerve?
Temporal, zygomatic, buccal, mandibular, cervical
89
Why would someone with a facial nerve lesion present with hyperacousis?
Injury to nerve to stapedius (which dampens noise)
90
What is the branch of the facial nerve that gives special sensory fibres to the anterior 2/3 of the tongue?
Chorda tympani
91
Which branch of the facial nerve gives parasympathetic fibres to glands?
Greater petrosal nerve
92
What is the most common cause of an intracranial lesion of the facial nerve?
Middle ear pathology
93
In extracranial lesions, which function of the facial nerve is affected?
Motor function - so paralysis of muscles of facial expression
94
What is idiopathic facial nerve palsy known as?
Bell's palsy
95
What are some causes of extracranial lesions of the facial nerve?
Parotid gland pathology (closely related), infection of the nerve, compression, idiopathic
96
Which foramen does the vestibulocochlear nerve go through?
Internal auditory meatus
97
What kind of information does the vestibulocochlear nerve transmit?
Special sensory (hearing and balance)
98
Where is the primary auditory cortex?
Temporal lobe
99
What is an acoustic neuroma?
Benign tumour of the schwann cells surrounding the vestibular component of CN VIII
100
What are the four cranial nerves that arise from the medulla?
Glossopharyngeal (IX)
Vagus (X)
Accessory (XI)
Hypoglossal (XII)
101
What kind of information is transmitted by the glossopharyngeal nerve?
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
What is the motor function of the glossopharyngeal nerve?
Innervates stylopharyngeus
103
What nerve is responsible for the sensory limb of the gag reflex?
Glossopharyngeal
104
What is the autonomic function of the glossopharyngeal nerve?
Parotid gland innervation
105
How is the glossopharyngeal nerve tested?
Gag reflex, tested in conjunction with CN X
106
What foramen does the glossopharyngeal nerve pass through?
Jugular foramen
107
What may glossopharyngeal nerve lesions result in?
Hypersensitive carotid sinus reflex
Loss of gag reflex (afferent)
108
What carries the afferent limb of the gag reflex?
Glossopharyngeal nerve
109
What carries the efferent limb of the gag reflex?
Vagus nerve
110
What kind of information is transmitted by the vagus nerve?
General sensory - lower pharynx and larynx
Motor - muscles of the soft palate, pharynx, larynx
Parasympathetic - thoracic and abdominal viscera
111
What foramen does the vagus nerve pass through to exit the skull?
Jugular foramen
112
Describe the route of the vagus nerve
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
What does the right recurrent laryngeal nerve hook underneath?
Right subclavian artery
114
What does the left recurrent laryngeal nerve hook underneath?
The arch of the aorta
115
How may a patient with vagus nerve lesions present?
- Uvula deviation away from site of lesion
| - Loss of gag reflex
116
What foramen does the accessory nerve pass through?
Jugular foramen
117
What kind of information is transmitted by the accessory nerve?
Motor
118
What is the function of the accessory nerve?
Supplies trapezius and SCM
119
How can the accessory nerve be tested?
Shrug shoulders against resistance, turn head against resistance
120
What does the spinal accessory nerve run down through the neck in?
Posterior triangle - susceptible to injury in this area
121
What kind of information does the hypoglossal nerve transmit?
Motor
122
What is the function of the hypoglossal nerve?
Innervates muscles of the tongue
123
What foramen does the hypoglossal nerve pass through?
Hypoglossal canal (on rim of foramen magnum)
124
What may be seen in a patient with hypoglossal nerve damage?
Weakened tongue
| Tongue may deviate towards side of lesion
125
Which cranial nerves could be affected by cavernous sinus thrombosis?
Oculomotor, trochlear, trigeminal (Va and Vb) and abducens
