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SA head and neck > S5) Cranial Nerves > Flashcards

S5) Cranial Nerves Flashcards

1
Q

Which nervous system do cranial nerves contribute to?

A

Peripheral Nervous System

supply head and neck

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2
Q

How many cranial nerves are there?

A

12 pairs (always come in 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
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17
Q

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

A
  • Head injury (secondary to shearing forces and/or basilar skull fracture)
  • Intracranial tumours at base of frontal lobes (within anterior cranial fossa)
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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
  • this is the only nerve you can visibly see
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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 3 conditions which produce optic nerve lesions

A
  • Optic neuritis
  • 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

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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
  • Role - responsible for moving the eyeball; elevator palpebral
  • Modality: motor and autonomic
  • CNS route: midbrain → edge of tentorium cerebelli → cavernous sinus → superior orbital fissure
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29
Q

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

A
  • Motor/somatic: innervates 4 extra-ocular muscles and LPS
  • Autonomic/parasympathetic: innervates sphincter pupillae (pupil) & ciliary muscle (lens) to control thickness of the 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 - eyelid droops
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32
Q

Identify 4 conditions which could cause pathology in the oculomotor nerve

A
  • Raised intracranial pressure (tumour/haemorrhage)
  • Aneurysms (posterior communicating artery)
  • Vascular (secondary to diabetes/hypertension)
  • 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: dorsal 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 - double vision (rare and often subtle)
  • Congenital palsies (children – cause uncertain)
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37
Q

What is the most common cause for acute injury to the trochlear nerve?

A

Head injury

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38
Q

Which 4 cranial nerves come from the pons?

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

Identify the 3 branches of the CN V Trigeminal Nerve

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

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

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

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

  • Modality
  • CNS route
  • Function
A
  • Modality: general sensory
  • CNS route: pons → middle cranial fossa → trigeminal cave → foramen rotundum
  • Function: innervates cheeks, lower eye lid, upper lip, upper teeth and palate
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 - severe facial pain (compression of blood vessel)
  • Shingles from herpes zoster virus

– orbital and mandibular fractures

– posterior cranial fossa tumours

47
Q

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

A

Infraorbital nerve

48
Q

Identify 3 nerves which arise from the mandibular division of the trigeminal nerve

A
  • Inferior alveolar ⇒ mental nerve
  • Lingual nerve
49
Q

Describe the following for the CN VI Abducens Nerve:

  • Modality
  • CNS route
  • Function
A
  • Modality: motor
  • CNS route: pons → subarachnoid space → cavernous sinus → superior orbital fissure
  • Function: innervates lateral rectus - rotates eyeball away from nose
50
Q

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

A

resting gaze; Eye movements (tests III, IV and VI)

51
Q

How does an injured abducens nerve present?

A

Patients present with diplopia

52
Q

Describe the following for the CN VII Facial Nerve:

  • Modality
  • CNS route
A
  • Modality: motor (facial expression), special sensory (taste), autonomic (parasympathetic)
  • CNS route: pons → internal auditory meatus → petrous part of temporal bone → base of skull via stylomastoid foramen
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 intracranial (within petrous)
55
Q

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

A
  • Muscles of facial expression
  • 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
  • issue with the facial nerve
  • unilateral facial droop
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
  • Function: hearing/balance
59
Q

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

A
  • Test hearing
  • Enquire about balance -dizziness
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?

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, posterior ⅓
  • CNS route: medulla → posterior cranial fossa → jugular foramen
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

so if any damage it can present with difficulty swallowing, weak cough and difficulties in speech

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

III. exits and heads towards the posterior triangle

  • 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 - trapezius
  • Turn head against resistance - SCM
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

can be damaged due to posterior cranial fossa tumours, and brainstem injuries

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

which 2 cranial nerves arise from the forebrain

A

I → olfactory

II - optic

86
Q

which two cranial nerves arise from the midbrain

A

III - ocular motor nerve

IV - trochlear

87
Q

which 4 cranial nerves arise from the pons

A

V - trigeminal

VI - abducens

VII - facial

VIII - vestibulocochlear

88
Q

which 4 nerves arise from the medulla

A

IX - GLOSSOPHARYNGEAL

X - vagus

XI - accessory

XII - hypoglossal

89
Q

will pathology effecting retina or optic nerve effect one eye or both

A
  • it will effect one eye, causing blurring and reduced vision
90
Q

will damage from optic chasm and optic tract effect one eye or both

A
  • they both contain a mix of sensory fibres from both eyes so both will be effected
91
Q

what are 2 major sensory branches from the ophthalmic branch (Va)

A

frontal nerve - gives rise to supra orbital and super trochlear

nasociliary nerve - supplies nose and and eye

92
Q

name the 2 major sensory branches from the maxillary branch of the trigeminal nerve (Vb)

A

infra orbital nerve - orbital floor

superior alveolar nerves - supplies upper teeth and gums

93
Q

name the 3 major sensory branches of the mandibular branch of the trigeminal nerve Vc

A
  • Auriculotemporal - sensory to side of the scalp
  • lingual nerve - general sensation of anterior ⅔ tongue
  • inferior alveolar nerve - supplies lower teeth and gums
  • mental nerve
94
Q

what is an orbital blow out fracture

A
  • punched under the eye
  • eyeball is pushed into the socket
  • high pressure
  • damage to the infraorbital nerve
  • sensory deficit
95
Q

what are some problems that can arise from facial nerve injury

A
  • caused from basal skull fractures, and posterior cranial fossa tumours
  • can result in middle ear disease
  • bells palsy
  • Ramsay hunt syndrome - little vesicles on the inside of the ear
96
Q

where does the facial nerve enter the skull

A

internal acoustic meatus

97
Q

what are the three branches of the facial nerve

A
  • nerve to stapedius
  • greater petrosal - parasympathetic fibres to lacrimal and mucosal glands
  • chorda tympani - taste anterior ⅔ of tongue and parasympathetic fibres to salivary glands
98
Q

difference in physiology and appearance of a stroke and facial droop

A
  • stroke: due to a blood clot
  • facial droop: to do with a facial nerve
  • in a stroke the patient is more likely to be able to move forehand and eye
99
Q

what are 5 functions of the vagus nerve

A
  1. parasympathetic to the heart
  2. parasympathetic to the stomach
  3. motor to larynx
  4. motor to the pharynx
  5. motor to the soft palate
100
Q

what are 4 roles of the glossopharangeal nerve

A
  1. parasympathetic to the parotid gland
    2.sensory to the middle ear
    3.sensory from the carotid body and sinus
    4.motor to the stylopharynheus

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