Cranial Nerves Flashcards
1
Q
What does the brainstem adjoin?
A
The brain and the spinal cord
2
Q
What are the parts of the brainstem?
A
- Pons
- Medulla
- Mid-brain
3
Q
Is the medulla functionally that different from the spinal cord?
A
Yes, very different
4
Q
What is the brainstem continuous with caudally?
A
The spinal cord
5
Q
Where does the brainstem have a vital role?
A
In regulation of cardio-respiratory functions and maintaining consciousness
6
Q
What runs through brainstem?
A
Ascending and descending fibres between the brain and the rest of the body run through it
7
Q
What is the brainstem the location of?
A
The majority of cranial nerve nuclei
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
9
Q
What are the cranial nerves part of?
A
The peripheral nervous system
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
11
Q
How many pairs of cranial nerves are there?
A
12
12
Q
What does each cranial nerve do?
A
Innervates halves, as they are in pairs
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
14
Q
What does each cranial nerve have for identification?
A
A roman numeral
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
16
Q
What do cranial nerves carry?
A
1000’s of axons
17
Q
What are the potential types of axons in cranial nerves?
A
- General sensory
- Special sensory
- Motor
- Autonomic
18
Q
How many of the cranial nerves are mixed?
A
Only four
19
Q
What is meant by a mixed cranial nerve?
A
Contain both motor and sensory modalities
20
Q
What is the special sense taste carried within?
A
Two of the mixed cranial nerves, mainly CN VII and CN IX
21
Q
How many of the cranial nerves are purely sensory?
A
3
22
Q
What do the sensory cranial nerves do?
A
Carry special sensory function, as opposed to general sensation
23
Q
What cranial nerve is responsible for hearing and balance?
A
CN VIII
24
Q
What cranial nerve is responsible for vision?
A
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)*
## Footnote
* 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
