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Sem 4 > H&N 4: Cranial Nerves > Flashcards

H&N 4: Cranial Nerves Flashcards

1
Q

What is CN I?

A

Olfactory nerve

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2
Q

What number is the optic nerve?

A

CN II

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3
Q

What number is the oculomotor nerve?

A

CN III

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4
Q

What is CN IV?

A

Trochlear nerve

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5
Q

What is cranial nerve V?

A

Trigeminal

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6
Q

What number is the abducens nerve?

A

CN VI

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7
Q

What number is the facial nerve?

A

CN VII

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8
Q

What number is the vestibulocochlear nerve?

A

CN VIII

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9
Q

What number is the glossopharyngeal nerve?

A

CN IX

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10
Q

What is cranial nerve X?

A

Vagus

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11
Q

What is cranial nerve XI?

A

Spinal accessory nerve

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12
Q

What is cranial nerve XII?

A

Hypoglossal nerve

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13
Q

What type of nerve fibres does the olfactory nerve transmit?

A

Special sensory (sense of smell)

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14
Q

Where does the olfactory nerve originate from?

A

Forebrain (only CN I and II do not originate form the brainstem)

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15
Q

What does the olfactory nerve pass through to go to the cranial cavity?

A

The cribiform plate of the ethmoid bone (roof of the nasal cavity)

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16
Q

What is anosmia and how can it be caused?

A

Absence of sense of smell
Temporary could be caused by URTI
Permanent could be caused by head injury, tumour, Alzheimer’s or Parkinson’s

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17
Q

What type of nerve fibres does the optic nerve transmit?

A

Special sensory (vision)

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18
Q

Where does the optic nerve originate?

A

From the forebrain (as does CN I)

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19
Q

What is the anatomical course of the optic nerve?

A

From the retina, leaves the orbit via the optic canal (in the sphenoid bone) and then each optic nerve from each eye unites to form the optic chiasm (by the pituitary gland). They then form the optic tracts to the forebrain.

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20
Q

Why can a pituitary adenoma lead to visual problems?

A

As the pituitary gland lies very close to the optic chiasm (in the middle cranial fossa), so enlargement of the pituitary gland can compress the optic nerves and affect their function

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21
Q

Where does the oculomotor nerve originate from?

A

Midbrain (of the brainstem)

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22
Q

What type of nerve fibres does the oculomotor nerve transmit?

A

Mainly motor fibres to most of the extra-ocular muscles

Also autonomic fibres (parasympathetic)

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23
Q

What are the parasympathetic functions of the oculomotor nerve?

A

To the ciliary body (contracts so the lens is adapted to more short range vision)
And sphincter pupillae (constricts the pupil to reduce the amount of light that can enter the eye)

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24
Q

What is the anatomical course of the oculomotor nerve?

A

Emerges from the midbrain
Runs in the roof of the cavernous sinus
Leave cranial cavity via superior orbital fissure, into the orbit

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25
What are the clinical signs of a CN III lesion?
- down and out eye (due to paralysis of superior, inferior and medial rectus and inferior oblique) - ptosis (due to paralysis of levator palpebrae superioris) - dilated pupil (due to unapproved action of dilator pupillae)
26
What may cause a lesion of the oculomotor nerve?
``` Raise ICP (tumour/ haemorrhage) Aneurysm Cavernous sinus thrombosis Hypertension Trauma ```
27
Where does the trochlear nerve originate from?
From the midbrain of the brainstem It is the only CN to arise from the dorsal aspect of the brainstem, hence it has the longest INTERcranial root of all CNs
28
What nerve fibres does the trochlear nerve transmit/ what is its function?
Only motor fibres to the superior oblique muscle (which depresses and intorts the eyeball)
29
What is the anatomical course of the trochlear nerve?
From dorsal aspect of the midbrain In cavernous sinus Enters superior orbital fissure
30
The trigeminal nerve is associated with derivatives from which pharyngeal arch?
1st
31
Where does the trigeminal nerve arise from and what is the anatomical course of its branches?
From the pons of the brainstem arise 3 peripheral processes Ophthalmic branch leaves cranium via superior orbital fissure Maxillary branch leaves cranium via foramen rotundum Mandibular branch leaves cranium via foramen ovalae Both ophthalmic and maxillary branches pass through cavernous sinus
32
What type of nerve fibres does the branches of the trigeminal nerve convey?
V1: sensory to forehead, scalp, upper eyelid and dorsum of nose. Parasympathetic to lacrimal gland V2: sensory to lower eyelid, lateral nose, cheeks, upper lip. Parasympathetic to lacrimal gland V3: sensory to lower lip, mucous membranes, anterior 2/3rds of tongue, chin, external ear. Motor mainly to muscles of mastication. Parasympathetic to salivary glands (parotid, sublingual and submandibular)
33
How can the trigeminal nerve be examined?
- ask px to close eyes and touch divisions of the face with cotton wool - ask them to clench claw and deviate mandible from side to side - test corneal reflex
34
What is the corneal reflex and what is the afferent and efferent limb?
Involuntary blinking of the eye by tactile or painful stimulation of cornea Afferent branch is CN V1 which detects the stimuli Efferent branch is CN VII which causes contraction of orbicularis oris muscle Abscent corneal reflex indicates damage to either of these nerves
35
Where does the abducens nerve arise from and what is its anatomical course?
From the pons of the brainstem, through the cavernous sinus, enters the orbit via the superior orbital fissure to innervate lateral rectus muscle
36
What is the function of the abducens nerve?
Only motor function, to the lateral rectus muscle (which abducts the eyeball away from the midline)
37
The facial nerve is associated with derivatives from which pharyngeal arch?
2nd
38
What are the functions of the facial nerve?
Motor: mainly to muscle of facial expression, also muscles of the ear Special sensory: taste to anterior 2/3rd tongue (NOT general sensory, this is done by CNV3) Parasympathetic: to many glands including submandibular, sublingual, lacrimal, nasal
39
Where does the facial nerve terminate into its 5 motor branches and what are the branches?
``` In the parotid gland (although this is not innervated by the facial nerve) Temporal Zygomatic Buccal Marginal mandibular Cervical ```
40
Which branch of the facial nerve is special sensory to the anterior 2/3rds of the tongue?
Chorda tympani
41
The parasympathetic fibres of the facial nerve are carried out by which branches?
Greater petrosal nerve and chorda tympani
42
What is the anatomical course of the facial nerve?
Intercranial: Arise from the pons of the brainstem, through the internal acoustic meatus of the petrous part of the temporal bone, through the facial canal and then exits via stylomastoid foramen Extracranial: Runs by ear, and splits into its terminal branches in the parotid gland
43
How can symptoms of facial nerve palsy differ if the lesion is intercranial or extra cranial?
Intercranial: Paralysis of muscles of facial expression as well as different effects depending on affected branches eg chorda tympani damage can cause reduced salivation and taste on ipsilateral 2/3rd tongue, nerve to stapedius can cause ipsilateral hyperacusis, greater petrosal nerve could cause ipsilateral reduced lacrimal fluid production Extracranial: Damage would only affect motor function ie muscles of facial expression
44
What are causes of facial nerve lesions?
Idiopathic is termed Bell's palsy Lesion of extrcranial branches could be due to parotid gland pathology, infection (eg by herpes virus), compression during forceps delivery Most common cause of intercranial lesion is middle ear pathology eg infection or tumour
45
What is the function of the vestibulocochlear nerve?
Purely special sensory, for hearing and balance
46
Where does the vestibulocochlear nerve arise from and where does it exit the cranium?
Arises from the pons of the brainstem, exits the cranium via the internal acoustic meatus of the temporal bone
47
The glossopharyngeal nerve is associated with derivatives of which pharyngeal arch?
3rd
48
What are the functions of the glossopharyngeal nerve?
Special sensory: taste to posterior 1/3rd tongue Sensory: oropharynx, carotid body and sinus, posterior 1/3rd tongue, Eustachian tube, middle ear Motor: stylopharyngeus muscle in the pharynx Parasympathetic: parotid gland
49
Where does the glossopharyngeal nerve arise from and where does it pass through the cranium?
Arises from the medulla of the brainstem | Leaves cranium via the jugular foramen
50
What are the afferent and efferent nerves involved in the gag reflex?
Afferent: glossopharyngeal Efferent: vagus
51
The 4th pharyngeal arch is associated with which nerve?
Vagus nerve, CN X
52
What is the rough anatomical course of the vagus nerve?
Longest course of all CNs Arises rom the medulla of the brain stem Leaves cranium via the jugular foramen Passes through the carotid sheath in the neck Down into the thorax and terminate in the abdomen, giving off branches as it descends
53
What is the function of the vagus nerve?
Sensory: larynx, part of ear, heart, GI tract Motor: muscles in soft palate, larynx and pharynx Special sensory: Parasympathetic: heart and GI tract, SM of trachea and bronchi
54
How does the root of the right recurrent laryngeal nerve differ to that of the left recurrent laryngeal nerve?
Right: hooks under the right subclavian artery and ascends to the larynx Left: hooks under the arch of the aorta and ascends to the larynx
55
What may some symptoms of a CN X lesion be?
Dysphagia, dysphonia
56
What is the function of the accessory nerve?
Motor innervation to SCM and trapezius
57
How could the accessory nerve function be tested?
Ask the patient to shrug their shoulders (trapezius) and turn their head against resistance (SCM), could also observe for any muscle wastage
58
What is the anatomical course of the accessory nerve?
From the medulla of the brain stem, through the jugular foramen and into the posterior triangle of the neck
59
What is the anatomical course of the hypoglossal nerve?
Arises from the medulla of the brainstem, exits the cranium via the hypoglossal canal, runs inferior to mandible and crosses over the ICA and ECA to enter the tongue (Must be wary not to damage CNXII in surgery of carotid arterie due to closeness!)
60
What is the function of the hypoglossal nerve?
Motor function to most of the muscles in the tongue, hence CN XII lesion can present as ipsilateral tongue weakness or atrophy
61
What foramina/ fissures do the three branches of the trigeminal nerves pass through and what areas do they each go to?
Ophthalmic branch goes through superior orbital fissure into the orbit Maxillary branch goes through foramen rotundum in pterygopalatine fossa Mandibular branch goes the formamen ovale into the infratemporal fossa
62
Which cranial nerves pass into the orbit and what do they pass through?
CN II, III, IV, Vi, VI All pass through superior orbital fissure other than CN 1 (optic nerve) which passes through optic canal
63
Where is the cavernous sinus located?
One on either side of the sella turcica
64
What structures pass through the cavernous sinus?
Internal carotid artery | CN III, IV, Vi, Vii, VI
65
What is a cavernous sinus thrombosis?
A venous blood clot within the cavernous sinus Could be a late complication of infection in the danger triangle of the face/ orbits/ paranasal sinuses/ maxillary teeth
66
A lesion to which cranial nerve will leave patients struggling to walk downstairs?
Trochlear nerve As this innervates superior oblique muscle Often present with a subtle head tilt as a result

Sem 4 (25 decks)

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