Cranial Nerves Flashcards
(125 cards)
1
Q
What Nervous Systems are the Cranial Nerves a part of?
A
Peripheral Nervous System
2
Q
Describe how the Cranial Nerves Arise.
A
Arise at irregular intervals from the CNS.
3
Q
How many axons do cranial nerves carry?
A
1,000.
4
Q
What are the different axon types?
A
- General Sensory.
- Special Sensory.
- Motor.
- Autonomic.
Cranial Nerves can be a combination of both.
5
Q
What does the Brainstem join?
A
The brainstem joins the brain to the spinal cord.
6
Q
What is the role of the Brainstem?
A
Regulate cardio-respiratory functions and maintaining consciousness.
7
Q
What is the Brainstem the main location of?
A
Cranial nerve nuclei (majority of).
8
Q
Which Cranial Nerves are found in the Forebrain?
A
Olfactory Nerve (CN1). Optic Nerve (CN2).
9
Q
Which Cranial Nerves are found in the Midbrain?
A
Oculomotor Nerve (CN3). Trochlear Nerve (CN4).
10
Q
Which Cranial Nerves are found in the Pons?
A
Trigeminal Nerve (CN5). Abducens Nerve (CN6). Facial Nerve (CN7). Vestibulocochlear Nerve (CN8).
11
Q
Which Cranial Nerves are found in the Medulla?
A
Glossopharyngeal Nerve (CN9). Vagus Nerve (CN10). Accessory Nerve (CN11). Hypoglossal Nerve (CN12).
12
Q
What is the Roman Numeral for the Olfactory Nerve?
A
CNI.
13
Q
What is the Roman Numeral for the Optic Nerve?
A
CNII.
14
Q
What is the Roman Numeral for the Oculomotor Nerve?
A
CNIII.
15
Q
What is the Roman Numeral for the Trochlear Nerve?
A
CNIV.
16
Q
What is the Roman Numeral for the Trigeminal Nerve?
A
CNV.
17
Q
What is the Roman Numeral for the Abducens Nerve?
A
CNVI.
18
Q
What is the Roman Numeral for the Facial Nerve?
A
CNVII.
19
Q
What is the Roman Numeral for the Vestibulocochlear Nerve?
A
CNVIII.
20
Q
What is the Roman Numeral for the Glossopharyngeal Nerve?
A
CNIX.
21
Q
What is the Roman Numeral for the Vagus Nerve?
A
CNX.
22
Q
What is the Roman Numeral for the Accessory Nerve?
A
CNXI.
23
Q
What is the Roman Numeral for the Hypoglossal Nerve?
A
CNXII.
24
Q
What is the function of the Olfactory Nerve?
A
Is a special sensory nerve for olfaction (sense of smell). Axons travel to the olfactory bulb, olfactory tract and into the temporal lobe.
25
Is the Olfactory Nerve a 'true' Cranial Nerve?
No, it is a paired anterior extension of the forebrain.
26
What is the word for loss of smell?
Anosmia.
27
How do you test the Olfactory Nerve?
Often not tested but the person is asked about difficulties or changes in the sense of smell, sometimes using smelling salts.
28
What can cause a loss of smell?
1. Head injury-> secondary to shearing forces +/ basilar skull fracture.
2. Tumours at the base of the frontal lobes within the anterior cranial fossa.
29
Is the Optic Nerve a 'true' Cranial Nerve?
No, it is a paired anterior extension of the forebrain.
30
What pathway is the Optic Nerve part of?
Visual Pathway.
31
Describe the pathway the optic nerve travels in to perceive vision.
Retinal ganglion cells send action potentials (impulses generated by cells within the retina) to axons from the optic nerve, which exists at the back of the orbit via the optic canal and the fibres cross and merge at the optic chiasm. They will reach the primary visual cortex where the action potentials are perceived as vision.
32
What does the Optic Nerve do?
Carries sensory fibres from one eye.
33
What happens at the Optic Chiasm?
Mixing of sensory fibres from right and left optic nerves.
34
What does the Optic Tract Contain?
Sensory information from part of the left and part of the right eye.
35
Describe the characteristics of lesions within the visual pathway?
Different lesions give very different patterns of visual loss.
36
Give examples of lesions within the visual pathway.
Retinal detachment.
Optic Neuritis.
Pituitary tumour.
Stroke.
37
What do Pituitary Tumours do in respect to the Optic Nerve?
Compress the optic chiasm, causing bilateral visual symptoms called bitemporal hemianopia.
38
How do you test the function of the Optic Nerve?
Visual Acuity Test, such as Snellen Chart, Charting Visual Fields, testing pupillary responses.
39
What device is used to see the Optic Nerve Directly?
Ophthalmoscope, which visualises the optic disc at the point at which the nerve enters the retina.
40
Why can the Optic Nerve Swell due to raised ICP?
The optic nerve carries extension of the meninges .
41
What technique can show raised intracranial pressure?
Fundoscopy.
42
What is the word for a swollen optic disc?
Papillodema.
43
Describe the Visual Pathway.
The visual pathway extends back from the retina towards the primary visual cortex found within the occipital lobe.
There is communication from the optic tracts within the midbrain to allow for certain visual reflexes.
44
What is the function of the Oculomotor Nerve?
It has a motor and autonomic function (also carries autonomic parasympathetic fibres).
1. It innervates most of the muscles that move the eyeball (extra-ocular muscles).
2. Innervates the muscle of the eyelid (Levator Palpabrae Superioris).
3. Innervates the Sphincter Papillae muscle which constructs the pupil- parasympathetic nervous system.
4. Innervates the ciliary muscles for changing eye lens- parasympathetic nervous system.
45
Where is the Oculomotor Nerve Vulnerable to Compression when Intracranial Pressure is raised?
Tentorium Cerebelli and Part of the Temporal Lobe.
46
How do you test the function of Oculomotor, Trochlear and Abducens Nerve?
Inspecting the eyelids and pupil size, testing eye movements and testing pupillary reflexes (to light for example).
47
What can Pathology in the Oculomotor Nerve Cause?
Pupillary Dilation and/ or double vision (diplopia). Down and out position can occur with severe ptosis (eyelid droop).
48
What is the name for double vision?
Diplopia.
49
What is the name for Eyelid Drooping?
Ptosis.
50
What Causes Injury/Pathology to the Oculomotor Nerve?
1. Raised Intracranial Pressure (tumour or haemorrhage) which causes external compression of the nerve.
2. Aneurysm of the posterior communicating artery causes external compression of the nerve.
3. Cavernous Sinus Thrombosis which can also cause external compression of the nerve.
4. Vascular problems, secondary to diabetes or hypertension, which is typically pupil spearing.
51
What is the function of the Trochlear Nerve?
The trochlear nerve has a purely motor function.
| It innervates Superior Oblique (one of the muscles that move the eyeball that is extra-ocular).
52
What Muscle does the Trochlear Nerve Innervate?
Superior Oblique.
53
What Muscles does Oculomotor Nerve Innervate?
1. Extra-ocular Muscles.
2. Lebvator Palpebrae Superioris.
3. Sphincter Pupillae Muscle.
54
Which Nerve Has the Longest Intracranial Course?
Trochlear Nerve.
55
What is the Clinical Presentation of Injury to the Trochlear Nerve?
Diplopia (worse on downward gaze). This is rare and often subtle, corrected with a head tilt.
56
What is the Cause of a Pathology of the Trochlear Nerve?
Head Injury or any cause of raised intracranial pressure.
| Congenital palsies with an unknown cause.
57
Describe in summary the branches of the Trigeminal Nerve.
Branches have an extensive distribution supplying the skin of the face and scalp and the deep structures of the face.
58
Describe the general function of the Trigeminal Nerve.
Overall the Trigeminal Nerve is motor and general sensory in function. It is the main sensory nerve supplying the skin of the face and part of the scalp.
It provides sensory innervation to deep structures within the head including paranasal air sinuses, nasal and oral cavity, anterior part of the tongue and meninges.
Motor to muscles of mastication (Vc only).
59
Which Deep Structures within the head are sensory innervated by the Trigeminal Nerve?
Paranasal Air Sinuses.
Nasal and Oral Cavity.
Anterior part of Tongue.
60
How do you test for the Trigeminal Nerve?
1. Test the Dermatomes (Va, Vb, Vc).
2. Testing muscles of mastication (jaw jerk).
3. Testing Corneal Reflex.
61
Give Examples of Conditions Involving Branches of the Trigeminal Nerve.
1. Trigeminal Neuralgia.
| 2. Shingles.
62
Describe the Branches of the Maxillary Division of the Trigeminal Nerve.
1. Infraorbital Nerve: runs through the floor of the orbit. Carries sensory from cheek and lower eye lid.
2. Superior Alveolar Nerve: upper teeth and gum sensory. Blocked by dentists and max fax surgeons.
63
When is the Infraorbital Nerve Susceptible to Injury?
Orbital floor fractures.
64
Describe the Branches of the Mandibular Division of the Trigeminal Nerve.
1. Inferior Alveolar Nerve: runs through bony canal in the mandible exiting as the mental nerve via the mental foramen. Carries sensory from area of mental protuberance (chin) to lower lip and gum.
2. Lingual Nerve: general sensory from the anterior part of the tongue.
3. Auriculotemporal Nerve:general sensory from part of ear, temple area/lateral side of head and scalp and temporomandibular joint.
65
When is the Inferior Alveolar Nerve Susceptible to Injury?
Mandibular Fractures.
66
Name the Branches of the Maxillary Division of the Trigeminal Nerve.
1. Infraorbital Nerve.
| 2. Superior Alveolar Nerve.
67
Name the Branches of the Mandibular Division of the Trigeminal Nerve.
1. Inferior Alveolar Nerve.
2. Lingual Nerve.
3. Auriculotemporal Nerve.
68
Describe the Branches of the Ophthalmic Division of the Trigeminal Nerve.
1. Supraorbital Nerve.
2. Supratrochlear Nerve.
Sensory innervation from the the forehead/anterior scalp. Follow the blood vessel with the same name.
69
Name the Branches of the Ophthalmic Division of the Trigeminal Nerve.
1. Supraorbital Nerve.
| 2. Supratrochlear Nerve.
70
Describe the Abducens Nerve Function.
Purely motor in function. Innervating the Lateral Rectus (one muscle of the extra-ocular).
71
Describe the Pathway of the Abducens Nerve.
Lower pons,
Cavernous Sinus,
Orbit via Superior Orbital Fissure.
72
What muscle does the Abducens Nerve Innervate?
Lateral Ructus.
73
What muscles does the Mandibular Branch of the Trigeminal Nerve Innervate?
1. Messeter.
2. Temporalis.
3. Medial Pterygoid.
4. Lateral Pterygoid.
74
How do patients with a Abducens Nerve Pathology present?
Diplopia.
75
What Injury Can Damage the Abducens Nerve?
Any injury that raises intracranial pressure like a bleed or a tumour. This is because the nerve is easily stretched as it emerges anteriorly at the pono-medullary junction before running under the surface of the pons and towards the cavernous sinus.
76
What Sensory Area does the Infraorbital Nerve Innervate?
Cheek and lower eye.
77
What Sensory Area does the Superior Alveolar Nerve Innervate?
Upper teeth and gums.
78
What Sensory Area does the Inferior Alveolar Nerve Innervate?
Mental protuberance, lower lip and gum.
79
What Sensory Area does the Lingual Nerve Innervate?
Anterior tongue.
80
What Sensory Area does the Auriculotemporal Nerve Innervate?
Ear, temple area, lateral side of head, scalp and temporomandibular joint.
81
What Sensory Area does the Supraorbital and Supratrochlear Nerves Innervate?
Forehead and anterior scalp.
82
Describe the pathway of the Olfactory Nerve.
Nasal Cavity Roof-> Cribiform Foramina-> Olfactory Bulb-> Olfactory Tract-> Temporal Lobe.
83
Describe the pathway of the Optic Nerve.
Retinal Ganglion Cells-> Axons from the Optic Nerve-> Exit back of orbit via optic canal-> fibres cross and merge at the optic chiasm.
84
Describe the pathway of the Oculomotor Nerve.
Front of the midbrain-> Pierce lateral wall of the cavernous sinus-> Superior orbital fissure-> orbit.
85
Describe the pathway of the Trochlear Nerve.
Midbrain-> Lateral wall of cavernous sinus-> superior orbital fissure.
86
Describe the pathway of the Trigeminal Nerve Ophthalmic branch.
Pons-> Trigeminal Ganglion-> Superior orbital fissure-> orbit.
87
Describe the pathway of the Trigeminal Nerve Maxillary branch.
Pons-> Trigeminal Ganglion -> Foramen Rotundum-> Pterygopalatine fossa.
88
Describe the pathway of the Trigeminal Nerve Mandibular branch.
Pons-> Trigeminal Ganglion-> Foramen Ovale-> Infratemporal Fossa.
89
Describe the pathway of the Abducens Nerve.
Lower Pons (between medulla and pons)-> runs upward before passing into the cavernous sinus-> enters into orbit via the orbital fissure.
90
Describe the pathway of the facial nerve.
Lower pons (junction between pons and medulla) then enters the petrous part of the temporal bone via the internal acoustic meatus. The 3 branches are within the temporal bone and exit through the base of the skull at the stylomastoid foramen. The extra cranial branches innervate the muscles of facial expression.
91
What are the functions of the Facial Nerve?
1. Special Sensory: Anterior 2/3 of tongue (taste).
2. Autonomic: Parasympathetic innervation of the lacrimal glands, mucosal glands in nose and roof of mouth and the salivary glands (apart from the parotid gland).
3. Motor.
4. General Sensory: small area of the external ear.
92
What contributes to the Facial Nerve?
Collections of different types of nerves (cell bodies) within the brainstem contribute axons to form the facial nerve.
93
What are the 4 parts of the brainstem that contribute to the facial nerve?
1. Nucleus Solitarius Rostral Gustatory Portion.
2. Motor Nucleus (Branchial Motor).
3. Superior Salivatory Nucleus.
4. Pontine Trigeminal Nucleus.
94
Describe the Nucleus Solitarius Rostral Gustatory Portion of the Facial Nerve.
Contains nerves carrying special sense taste.
95
Describe the Motor Nucleus (Branchial Motor) of the Facial Nerve.
Carry motor to muscles of facial expression.
96
Describe the Superior Salivatory Nucleus of the Facial Nerve.
This is the parasympathetic motor, autonomic fibres to glands (the salivary, lacrimal, mucosal in nose and palate).
97
Describe the Pontine Trigeminal Nucleus of the Facial Nerve.
Small area of sensory innervation within the ear.
98
Describe the 2 roots at the Cerebellopontine angle of the Facial Nerve.
1. Motor Root: which is larger with just motor axons.
| 2. Nervus Intermedius: Sensory and parasympathetic axons.
99
How do you assess the Facial Nerve function?
Test the muscles of facial expression and the corneal reflex.
100
Describe the clinical relevance of the Facial Nerve.
Given the Facial Nerves many functions, facial nerve lesions can present with a variety of symptoms depending on where on the nerve route the pathology is. Other symptoms include: hyperacusis, dry eyes and altered taste. Middle ear pathology in petrous bone can sometimes involve the facial nerve.
The facial nerve has a close relationship with vestibulocochlear nerve within posterior cranial fossa and both enter the internal acoustic meatus.
The extracranial branches of the facial nerve have a close relationship with the parotid gland.
101
Describe the Corneal Reflex.
The afferent limb is by the Trigeminal Nerve and the efferent limb of the reflex by the Facial Nerve.
102
Describe the pathway of the Vestibulocochlear Nerve.
The Cochlea and Semicircular canals (vesticular system) converge to form the Vestibulocochlear Nerve. It enters the internal acoustic meatus. It goes to the lower pons (the junction between the pons and medulla).
103
What is the function of the Vestibulocochlear Nerve?
Hearing and balance as a special sensory function.
104
How do you test the Vestibulocochlear Nerve?
Testing hearing and enquiring balance.
105
Describe the Clinical Points of the Vesticulocochlear Nerve.
Damage involving cochlea, cochlear component of the vestibulocochlear nerve, or brainstem nucleus causes hearing loss.
106
What is the medical word for hearing loss?
Sensorineural.
107
What is the medical word for old-age related hearing loss?
Presbyacusis.
108
What is an Acoustic Neuroma?
Benign tumour involving the vestibulocochlear nerve. It is a tumour of the Schwann cells surrounding the vestibular component of the CNVIII. Its physical presence causes compression of the whole nerve.
109
What is the Signs and Symptoms of a Acoustic Neuroma?
1. Unilateral hearing loss.
2. Tinnitus.
3. Vertigo.
4. Numbness, pain or weakness down one half of the face.
110
Which Nerves exit via the Jugular Foramen with the Internal Jugular Vein?
1. Glossopharyngeal Nerve.
2. Vagus Nerve.
3. Accessory Nerve.
111
What characteristics do the 4 cranial nerves in the medulla share?
All 4 cranial nerves arising from the medulla exit the base of the skull to enter into the superior part of the carotid sheath, most quickly exit to travel towards the target tissue. Only the Vagus Nerve runs the length of the carotid sheath.
112
What are the function of the Glossopharyngeal Nerve?
1. General sensation: Palatine tonsils and oropharynx, Middle ear (tympanic branch) and tympanic membrane and the carotid body and sinus.
2. Special Sensory: taste and general sensation of the posterior 1/3 of the tongue.
3. Autonomic: carries parasympathetic innervation to the parotid gland.
4. Motor: supplies the Stylopharngeus which assists in swallowing.
113
How do you test the Glossopharyngeal Nerve?
Gag reflex (sensory limb) only tested if concerns around swallowing and integrity of nerves involved in this reflex. Taste is not formally tested. Tested in conjunction with vagus nerve (CNX). Isolated lesions of CNIX are rare.
114
Describe the pathway of the Vagus Nerve.
Medulla leading into the jugular foramen via the carotid sheath. It then travels through the neck into the thorax and abdomen. It gives many branches on its route. Right and left vagus nerve runs in the carotid sheath. The right recurrent laryngeal nerve turns under the right subclavian and the left recurrent laryngeal nerve turns under the arch of the aorta.
115
What are the functions of the Vagus Nerve?
1. General Sensory: to lower pharynx and larnyx and posterior part of the external ear and tympanic membrane.
2. Motor: muscles of the soft palate, pharynx and larynx.
3. Autonomic: parasympathetic to thoracic and abdominal viscera (e.g. the heart, tracheobronchial tree
116
How do you assess the Vagus Nerve?
Note the patients speech, cough and ability to wallow. Note the movement of the uvula and soft palate when saying Aaah.
Test the gag reflex.
117
Describe the clinical presentation of pathology of the vagus nerve?
isolated lesions of CNX are rare. Injury to its branches, e.g. recurrent laryngeal nerve following thyroid surgery can cause hoarseness and dysphonia.
118
What is the function of the Spinal Accessory Nerve?
Innervate sternocleidomastoid and trapezius (motor).
119
Describe the pathway of the spinal accessory nerve.
Emerges through the jugular foramen, passes deep to sternocleidomastoid and provides its motor innervation. It then runs posterolaterally across the posterior triangle and enters deep to trapezius, providing its motor innervation.
120
How do you assess the Spinal Accessory Nerve?
Shrug shoulders against resistance (trapezius), turn head against resistance (sternocleidomastoid).
121
Describe the Clinical Points of the Spinal Accessory Nerve.
Spinal accessory runs inferiorly through the neck in the posterior triangle quite superficially and thus is susceptible to injury in this area, e.g. in lymph node biopsies, surgery and in stab wounds.
122
What is the function of the Hypoglossal Nerve?
Innervate muscles of the tongue apart from one.
123
Describe the pathway of the Hypoglossal Nerve.
CNXII runs medial to the angle of mandible, crossing the internal and external carotid arteries in the neck. It enters via the Hypoglossal foramen.
124
How do you assess the Hypoglossal Nerve?
Inspection and movement of the tongue.
125
Describe the Clinical Points of the Hypoglossal Nerve.
This is rare. Damage causes weakness and atrophy of the tongue muscles on the ipsilateral side.
