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(Edited) Head, Neck & Neuroanatomy COPY > S5) Cranial Nerves > Flashcards

S5) Cranial Nerves Flashcards

1
Q

Which nervous system do cranial nerves contribute to?

A

Peripheral Nervous System

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2
Q

How many cranial nerves are there?

A

12 pairs

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3
Q

Differentiate between the distribution of cranial nerves and spinal nerves

A

Cranial nerves arise at irregular intervals from CNS rather than segments as seen in spinal nerves

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4
Q

Which structure are the cranial nerves related to?

A

Brainstem

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5
Q

What is the brainstem and what does it do?

A
  • The brainstem is a structure which adjoins the brain to the spinal cord and is continuous with spinal cord caudally
  • Vital role in regulation of cardio‐respiratory functions and maintaining consciousness
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6
Q

Which part of the cranial nerves is located in the brainstem?

A

Cranial nerve nuclei

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7
Q

What are nuclei?

A

Nuclei are collections of the cell bodies of nerve fibres that make up the whole cranial nerve

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8
Q

Cranial nerves carry 1000s of axons.

What different types of properties might they convey?

A
  • General sensory
  • Special sensory
  • Motor
  • Autonomic
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9
Q

How are cranial nerves distributed in the brainstem?

A
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10
Q

How are cranial nerves named?

A
  • Individual names + Roman Numeral
  • Roman numeral relates to order that they arise (rostral to caudal)
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11
Q

Label the 12 cranial nerves below:

A
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12
Q

Which 2 cranial nerves come from the forebrain (cerebrum)?

A
  • Olfactory nerve
  • Optic nerve
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13
Q

What is unique about the optic and olfactory cranial nerves?

A

They are paired anterior extensions of forebrain rather than a ‘true’ cranial nerve

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14
Q

Describe the following for the CN I Olfactory Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: special sensory
  • CNS route: forebrain → olfactory tract → olfactory bulb → cribiform plate
  • Function: olfaction
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15
Q

How can one test the function of the CN I Olfactory Nerve?

A
  • Check for difficulties/change in sense of smell
  • Test one nostril at a time
  • Use smelling salts
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16
Q

What is anosmia and what is its commonest cause?

A
  • Anosmia is a loss of sense of smell
  • Commonest cause is a cold
  • Little bit of communication coming from one olfactory tract to another - so to have massive loss of smell both parts of tract must be affected
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17
Q

Other than a cold, identify 2 other events which could cause anosmia

How can head trauma lead to shearing damage of olfactory nerve?

A
  • Head injury (secondary to shearing forces and/or basilar skull fracture)
  • Intracranial tumours at base of frontal lobes (within anterior cranial fossa)
  • Head trauma → slight anterior to posterior displacement of brain in skull cavity → perpendicular relationship of olfactory nerves running through foramina can cause shearing injury
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18
Q

Describe the following for the CN II Optic Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: special sensory
  • CNS route: forebrain → optic tract → middle cranial fossa (optic chiasm) → optic canal → retina
  • Function: vision
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19
Q

How can one test the function of the CN II Optic Nerve?

A
  • Test pupil responses/reflexes (using pen torches)
  • Test one eye at a time
  • Visual tests (Snellen Chart, Visual Fields)
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20
Q

How can the optic nerve be seen directly?

A

Using an ophthalmoscope

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21
Q

What is papilloedema?

A

Papilloedema is a swollen optic disc

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22
Q

What is the significance of papilloedema?

A
  • It provides evidence of raised intracranial pressure
  • Optic nerve swells because it carries an extension of meninges
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23
Q

Describe the impact of lesions involving the retina/optic nerve

A

Lesions involving the retina or the optic nerve cause visual disturbances which affect only one eye

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24
Q

Different lesions give very different patterns of visual loss.

Identify 4 conditions which produce optic nerve lesions

A
  • Optic neuritis
  • Anterior ischaemic optic neuritis (AION)
  • Pituitary tumour
  • Stroke
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25
Q

Describe the course of the visual pathway

A

The visual pathway extends back from the retina towards the primary visual cortex in the occipital lobe

There is communication from the optic tracts with brainstem (midbrain) to allow for certain visual reflexes e.g. pupillary reflexes to light

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26
Q

What effect do pituitary tumours have?

A

Pituitary tumours compress optic chiasm, causing bilateral visual symptoms (bitemporal hemianopia)

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27
Q

Which 2 cranial nerves come from the midbrain?

A
  • Oculomotor nerve
  • Trochlear nerve
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28
Q

Describe the following for the CN III Oculomotor Nerve:

  • Modality
  • CNS route
A
  • Modality: motor and autonomic
  • CNS route: midbrain → cavernous sinus → superior orbital fissure

(close relationship with tentorium cerebelli before enters cavernous sinus)

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29
Q

Describe the motor and autonomic functions of the CN III Oculomotor Nerve

A
  • Motor: innervates 4 extra-ocular muscles and LPS
  • Autonomic: innervates sphincter pupillae (pupil) & ciliary muscle (lens)
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30
Q

How can one test the function of the CN III Oculomotor Nerve?

A
  • Inspection of eyelid and pupils
  • Eye movements (tests III, IV and VI)
  • Pupillary light reflexes
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31
Q

What can result from pathology in the oculomotor nerve?

A
  • Pupillary dilation
  • Double vision (diplopia)
  • Severe ptosis
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32
Q

Causes for CN III lesions can be divided into pupil sparing (appears normal despite symptoms) and pupil involving / compressive:

Identify 4 conditions which could cause pathology in the oculomotor nerve and wether they are pupil sparing or involving

A

Pupil sparing:

  • Microvascular ischaemic (secondary to diabetes/hypertension/>50 years)

Pupil involving / Compressive:

  • Raised intracranial pressure (tumour/haemorrhage) → tentorial herniation
  • Aneurysms (posterior communicating artery)
  • Cavernous sinus thrombosis
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33
Q

Describe the following for the CN IV Trochlear Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: motor
  • CNS route: midbrain → subarachnoid space → cavernous sinus → superior orbital fissure

- Function: innervates superior oblique muscle

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34
Q

Which 2 things are unique about the trochlear nerve?

A
  • Only nerve to emerge from the dorsal aspect of the brainstem
  • Longest intracranial course of any of the cranial nerves
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35
Q

How can one test the function of the CN IV Trochlear Nerve?

A

Eye movements (tests III, IV and VI)

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36
Q

What can result from acute injury to the trochlear nerve?

A
  • Diplopia (rare and often subtle)
  • Congenital palsies (children – cause uncertain)
37
Q

What is the most common causes for injury to the trochlear nerve?

A

Congenital or aquired - Acquired:

  • Head injury / trauma
  • Tumour
  • Microvascular ischaemia - >50 years (diabetes / hypertension)
38
Q

Which 4 cranial nerves come from the pons?

A
  • Trigeminal Nerve
  • Abducens Nerve
  • Facial Nerve
  • Vestibulocochlear Nerve
39
Q

Identify the 3 branches of the CN V Trigeminal Nerve

A
  • Opthalmic nerve (V1)
  • Maxillary nerve (V2)
  • Mandibular nerve (V3)
40
Q

Describe the following for the opthalmic branch of CN V Trigeminal Nerve:

  • Modality
  • CNS route
  • Function
  • Branches
A
  • Modality: general sensory
  • CNS route: pons → middle cranial fossa → trigeminal cave → cavernous sinus → superior orbital fissure
  • Function: innervate scalp, forehead and nose
  • Branches: lacrimal, frontal, nasociliary
41
Q

Describe the following for the maxillary branch of CN V Trigeminal Nerve:

  • Modality
  • CNS route
  • Function
  • Branches
A
  • Modality: general sensory
  • CNS route: pons → middle cranial fossa → trigeminal cave → cavernous sinus → foramen rotundum → pterygopalatine fossa → infraorbital fissure
  • Function: innervates cheeks, lower eye lid, upper lip, upper teeth and palate
  • Branches: infraorbital nerve branches through infraorbital foramen
42
Q

Describe the following for the mandibular branch of CN V Trigeminal Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: general sensory, motor
  • CNS route: pons → middle cranial fossa → trigeminal cave → foramen ovale
  • Function: innervates anterior 2/3 tongue, skin over mandible and lower teeth, muscles of mastication
43
Q

What is a ganglion?

A

A ganglion refers to a collection of the nerve cell bodies outside the central nervous system

44
Q

What is the trigeminal cave?

A

The trigeminal cave is a depression of the temporal bone, located lateral to the cavernous sinus

45
Q

How can one test the function of the trigeminal nerve?

A
  • Test dermatomal areas relating to CN V1, V2, V3
  • Test muscles of mastication
  • Test corneal reflex
46
Q

Identify 2 clinical conditions that cause pathology in the trigeminal nerve

A
  • Trigeminal neuralgia
  • Shingles
47
Q

Identify a nerve which arises from the maxillary division of the trigeminal nerve

When is it vulnerable to injury?

A

- Infraorbital nerve - emerges through infraorbital foramen

  • Vulnerable as passes thorugh bones of floor of orbit (oribital fractures that affect floor of orbit)
48
Q

Identify nerves which arise from the mandibular division of the trigeminal nerve

A
  • Nerves to supply muscles of mastication (infratemporal fossa)
  • Auriculotemporal nerve
  • Inferior alveolar n. → mandibular foramen → Mandible → mental foramen ⇒ mental nerve
  • Lingual nerve (GS tongue)
49
Q

Describe the following for the CN VI Abducens Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: motor
  • CNS route: pons → subarachnoid space (steep upward route) → cavernous sinus → superior orbital fissure
  • Function: innervates lateral rectus
50
Q

How can one test the function of the CN VI Abducens Nerve?

A

Eye movements (tests III, IV and VI)

51
Q

How does an injured abducens nerve present?

How can abducens be injured?

A
  • Patients present with diplopia
  • Injuries:
    • Microvascualr ischaemia
    • Head injury, tumour
    • Raised ICP → False localising sign
52
Q

Describe the following for the CN VII Facial Nerve:

  • Modality
  • CNS route
A
  • Modality: motor, special sensory, autonomic
  • CNS route: pons → internal auditory meatus → petrous part of temporal bone (gives off branches) → stylomatoid foramen → base of skull
53
Q

Describe the motor, special sensory and autonomic functions of the CN VII facial nerve

A
  • Motor – innervates muscles of facial expression
  • SS – taste anterior 2/3 tongue
  • Autonomic – lacrimal, submandibular, sublingual glands and mucous glands of mouth and nose
54
Q

How many branches does the facial nerve have?

A

Seven key branches:

  • 5 extracranial
  • 2 (3?) intracranial (within petrous)
55
Q

How can one test the function of the CN VII Facial Nerve?

A
  • Muscles of facial expression (+/- unilateral droop)
  • Corneal reflex (efferent limb)
  • Taste (anterior 2/3 tongue)
56
Q

Describe the anatomical relationships of the facial nerve

A
  • Associated with vestibulocochlear nerve within posterior cranial fossa and as both enter the IAM
  • Associated with middle ear during its course through petrous temporal bone
  • Associated with parotid gland
57
Q

Identify an idiopathic facial nerve palsy

A
58
Q

Describe the following for the CN VIII Vestibulocochlear Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: special sensory
  • CNS route: pons → cerebellopontine angle → internal acoustic meatus → petrous bone → vestibular and cochlear system
  • Function: hearing/balance
59
Q

How can one test the function of the CN VIII Vestibulocochlear Nerve?

A
  • Test hearing
  • Enquire about balance
60
Q

What is the result of damage involving the vestibulocochlear nerve, its brainstem, nucleus or cochlea?

A
  • Hearing loss (sensorineural)
  • Disturbance of balance (vertigo)
  • Nystagmus (uncontrolled eye movement)
61
Q

What is presbyacusis?

A

Presbyacusis is old‐age related hearing loss

62
Q

What are acoustic neuromas? (Vestibular schwanomma)

A

Acoustic neuromas are benign tumours of the Schwann cells surrounding the vestibular component of CN VIII

63
Q

The physical presence of acoustic neuromas cause the compression of the whole vestibulocochlear nerve.

Identify 5 signs and symptoms

A
  • Unilateral hearing loss
  • Tinnitus
  • Vertigo
  • Numbness
  • Pain or weakness down one half of face
64
Q

Which 4 cranial nerves come from the medulla?

A
  • Glossopharyngeal Nerve
  • Vagus Nerve
  • Accessory Nerve
  • Hypoglossal Nerve
65
Q

Describe the following for the CN IX Glossopharyngeal Nerve:

  • Modality
  • CNS route
A
  • Modality: general sensory, special sensory, autonomic, motor
  • CNS route: medulla → posterior cranial fossa → jugular foramen → carotid sheath (close relationship with internal and external carotid arteries)
66
Q

What are the general sensory functions of the glossopharyngeal nerve?

A
  • General sensation of soft palate, tonsils and oropharynx
  • Innervation of middle ear and tympanic membrane
67
Q

What are the special sensory functions of the glossopharyngeal nerve?

A
  • Sensory from carotid body and sinus
  • Taste and general sensation post. 1/3 tongue
68
Q

What is the motor function of the glossopharyngeal nerve?

A

Innervates stylopharyngeus muscle

69
Q

What is the autonomic function of the glossopharyngeal nerve?

A

Innervates parotid gland

70
Q

How do one test the function of the CN IX Glossopharyngeal Nerve?

A
  • Gag reflex (sensory limb)
  • Taste not formally tested
  • Tested in conjunction with CN X
71
Q

Describe the following for the CN X Vagus Nerve:

  • Modality
  • CNS route
A
  • Modality: general sensory, motor, autonomic
  • CNS route: medulla → jugular foramen → carotid sheath
72
Q

Identify 3 functions of the CN X Vagus Nerve

A
  • Sensory innervation to lower pharynx, and larynx
  • Motor innervation to muscles of soft palate, pharynx, larynx
  • Parasympathetic innervation to thoracic and abdominal viscera
73
Q

How can one test the function of the vagus nerve?

A
  • Noting speech
  • Swallow and cough
  • Observe uvula (say ‘ahh’)
  • Gag reflex (efferent limb)
74
Q

What could result from injury to the recurrent laryngeal nerve branch of the vagus nerve?

A
  • Hoarseness
  • Dysphonia (difficulty speaking)
75
Q

Describe the following for the CN XI Accessory Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: motor
  • CNS route:

I. Cranial part – medulla → jugular foramen → joins the vagus nerve

II. Spinal part – medulla → foramen magnum → jugular foramen

  • Function: spinal part supplies the sternocleidomastoid & trapezius
76
Q

How can one test the function of the CN XI Accessory Nerve?

A
  • Shrug shoulders against resistance
  • Turn head against resistance
77
Q

The spinal accessory nerve runs down through neck in posterior triangle.

What is the clinical significance of this?

A

It is susceptible to injury in this area e.g. in lymph node biopsies, surgery, stab wound

78
Q

Describe the following for the CN XII Hypoglossal Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: motor
  • CNS route: medulla → posterior cranial fossa → hypoglossal canal
  • Function: innervates muscles of tongue
79
Q

How can one test the function of the CN XII Hypoglossal nerve?

A

Inspection and movement of the tongue

80
Q

Damage to the hypoglossal nerve is rare.

Regardless, state the impact of such a damage

A

Weakness and atrophy of the tongue muscles on ipsilateral side

81
Q

Identify the 5 cranial nerves and the specific artery which pass through the cavernous sinus

A
82
Q

Identify another nervous structure which is closely associated with the cavernous sinus

A

Trigeminal ganglion – located lateral to the cavernous sinus

83
Q

What is a cavernous sinus thrombosis?

A

A cavernous sinus thrombosis is a blood clot in the cavernous sinus

84
Q

How might a cavernous sinus thrombosis arise?

A
  • Develops when an infection in the face/skull spreads to the cavernous sinuses
  • The blood clot develops to prevent the infection spreading further, but restricts the blood flow from the brain
85
Q

How does the dual blood supply of CN III lead to diversity of symptoms dependign on the lesion?

A
  • Microvascular diseases tend to affect vasa nevorum
  • So central nerves that are responsible for eyelid and position of eyeball are vulnerable whereas parasympathetic fibres have back up supply not affected
  • In compressive lesions peripheral parasympathetic fibres are 1st to be affected
  • In head injuries check size of pupils to check one hasn’t become fixed & dilated → implies compressive lesion
86
Q

What is false localising sign for absucens nerve? How does it arise?

A
  • Raised ICP tends to lead to things being pushed downwards towards foramen magnum
  • Due to steep upwards pathway of nerve can get stretching of nerve
  • No direct squashing of nerve but are stretching it = false localising sign
  • Problem isn’t necesarily anything near to abducens nerve
87
Q

What 3 branches does the facial nerve give off in the petrous bone?

A
  • Greater petrosal nerve (parasympathetic) → supplies lacrimal gland, nasal, oral mucosal glands, salivary glands
  • Nerve to stapedius (motor)
  • Chorda tympani (parasympathetic & sensory) → SS to anterior 2/3 tongue, parasympathetic to slaivary glands in oral cavity
88
Q

What differant conditions / lesions can affect the facial nerve?

A
  • Lesions in/around internal acoustic meatus & posterior cranial fossa tumours
  • Basal skull fractures (invovlign petrous bone)
  • Middle ear disease
  • Inflammation in facial canal, facial nerve palsy e.g. Bell’s Palsy, Ramsay-Hunt sydrome
  • Parotid disease

(Edited) Head, Neck & Neuroanatomy COPY (19 decks)

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