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AHNNS > 7. Cranial Nerves I-VII > Flashcards

7. Cranial Nerves I-VII Flashcards

1
Q

What is the location of the majority of the cranial nerve nuclei?

A

Brainstem

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2
Q

What is the role of the brainstem?

A

Regulation of cardio-respiratory functions and maintaining consciousness.

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3
Q

How many cranial nerves arise from the brain (forebrain), midbrain, pons and medulla?

A

Brain (forebrain) - 2.
Midbrain - 2.
Pons - 4.
Medulla - 4.

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4
Q

What cranial nerves arise from the forebrain?

A

I - olfactory nerve.

II - optic nerve.

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5
Q

What is the function of CN I, the olfactory nerve?

A

Special sensory - olfaction.

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6
Q

Through which foramen does CN I, the olfactory nerve pass?

A

Cribiform foramina.

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7
Q

Damage to the CN I, the olfactory nerve, can cause anosmia. What injuries can cause this?

A

Head injury causing anosmia secondary to shearing forces and/or a basilar skull fracture damaging the olfactory nerve.
Intracranial tumours at base of frontal lobes within the anterior cranial fossa.

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8
Q

What is the most common cause of anosmia?

A

Common cold.

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9
Q

How would you test clinically for damage to CN I, the olfactory nerve?

A

Ask if patient has noticed any difficulties or changes in sense of smell.
Test one nostril at a time with smelling salts, coffee, peppermint etc.

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10
Q

What is the function of CN II, the optic nerve?

A

Special sensory - vision.

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11
Q

Through which foramen does CN II, the optic nerve, pass?

A

Optic canal.

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12
Q

Why can the optic nerve swell due to raised intracranial pressure?

A

Carries an extension of the meninges.

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13
Q

What would you see as evidence of raised intracranial pressure on a fundoscopy?

A

Swollen optic disc (papillodema).

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14
Q

Why do lesions involving the retina or the optic nerve cause visual disturbances affecting only one eye?

A

Lesion occurring before the optic chiasm, so there is no mixing of optic nerve fibres.

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15
Q

What can the optic nerve be seen directly with?

A

An ophthalmoscope.

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16
Q

How would you test for damage to CN II, the optic nerve?

A

Test one eye at a time.

Do both visual tests and test the pupil responses/reflexes.

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17
Q

What can cause bilateral visual symptoms (bitemporal hemianopia) and why?

A

Pituitary tumours, as compressive optic chiasm.

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18
Q

What is the purpose of there being some communication from the optic tracts with the brainstem?

A

To allow for certain visual reflexes eg pupillary reflexes to light.

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19
Q

What two cranial nerves arise from the midbrain?

A

CN III - oculomotor.

CN IV - trochlear.

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20
Q

What is the function of CN III, the oculomotor nerve?

A

Motor - supplies most extra-ocular muscles and levator palpebrae superioris (opens eyelid).
Autonomic (parasympathetic) - ciliary muscle (lense) and sphincter pupillae (pupil).

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21
Q

Through which foramen does CN III, the oculomotor nerve pass?

A

Superior orbital fissure.

22
Q

Why can raised intracranial pressure lead to compression of CN III, the oculomotor nerve, causing an enlarged pupil on the affected side?

A

Oculomotor nerve runs very close to the tentorium cerebelli, so raised intracranial pressure pushes the uncus onto the oculomotor nerve.

23
Q

Where do the autonomic and motor fibres sit in CN III, the oculomotor nerve?

A

Autonomic (parasympathetic) found at the edge of the nerve, motor fibres in the centre.

24
Q

What is seen clinically in compression of CN III, the oculomotor nerve?

A

Pupillary dilation and/or diplopia.

‘Down and out’ position with sever ptosis (eyelid droop).

25
What can cause compression of CN III, the oculomotor nerve?
Raised intracranial pressure (due to tumour or haemorrhage). Aneurysms of the posterior communicating artery. Vascular secondary to diabetes of hypertension (typically pupil sparring). Cavernous sinus thrombosis.
26
How would you test for damage to CN III, the oculomotor nerve?
Inspection of eyelid and pupils. Test eye movements. Test pupillary light reflexes.
27
What is the function of CN IV, the trochlear nerve?
Motor - innervates 1 extra-orbital muscle the superior oblique.
28
Through which foramen does CN IV, the trochlear nerve pass?
Superior orbital fissure.
29
What cranial nerve is the only nerve to emerge from the dorsal aspect of the brain, giving it the longest intracranial course of any of the cranial nerves?
CN IV, the trochlear nerve.
30
What can be seen clinically when there is damage to CN IV, the trochlear nerve?
Diplopia which is worse on downward gaze, and can be corrected with tilt of the head.
31
What injuries and conditions can cause damage to CN IV, the trochlear nerve?
Head injury. Any cause of raised intracranial pressure. Congenital palsies.
32
How would you test for damage to CN IV, the trochlear nerve?
Test eye movements.
33
What intracranial nerves arise from the pons?
V - trigeminal. VI - abducens. VII - facial. VIII - vestibulocochlear.
34
What is the function of CN V, the trigeminal nerve?
S - main sensory nerve of the face. | M - supplies muscles of mastication.
35
What are the 3 branches of the trigeminal nerve and what foramen does each pass through?
Opthalmic nerve - superior orbital fissure. Maxillary nerve - foramen rotundum. Mandibular nerve - foramen ovale.
36
What may be seen clinically due to injury of CN V, the trigeminal nerve?
Loss of sensation in dermatomes Va, Vb or Vc. | Lack of corneal reflex as forms afferent limb of corneal reflex.
37
What injuries and conditions can lead to damage of CN V, the trigeminal nerve?
Orbital/facial trauma damaging cutaneous branches. Trigeminal neuralgia. Shingles.
38
How would you test for damage to CN V, the trigeminal nerve?
For sensation test dermatomal areas CN Va, Vb and Vc. Muscles of mastication. Corneal reflex.
39
Where does the maxillary nerve branch of CN V, the facial nerve, run through before exiting the skull for the second time and what as?
Runs through base of orbit, exits as infraorbital nerve.
40
Why can a blow out fracture lead to reduced sensation to the cheek underneath the orbit?
Damaged infraorbital nerve.
41
What 3 branches does the mandibular nerve of Cn V, the trigeminal nerve, give rise to, and what does each innervate?
Interior alveolar nerve - gum. Mental nerve - lip. Lingual nerve - tongue.
42
Why does a fracture to the mandible lead to reduced chin sensation?
The inferior leveller nerve runs through the mandibular foramen, and emerges as the mental nerve through the mental foramen. So a fracture severed the nerve leading to loss of sensation.
43
What is the function of CN VI, the abducens nerve?
Motor - innervates the lateral rectus for lateral abduction of the eye.
44
Through which foramen does CN VI, the abducens nerve pass?
Superior orbital fissure.
45
What type of injury can cause damage to CN VI, the abducens nerve? Why?
Injury eg bleed, tumour leading to raised intracranial pressure. Nerve emerges anteriorly at the ponto-medullary junction before running under the surface of the pons upwards towards the cavernous sinus, so can be easily stretched in raised intracranial pressure.
46
What do patients present with when there is damage to CN VI, the abducens nerve?
Diplopia.
47
What is the function of CN VII, the facial nerve?
Motor - innervates muscles of facial expression. Special sensory - taste at anterior 2/3 tongue. Autonomic (parasympathetic) - to lacrimal gland and salivary gland.
48
Through which foramen does CN VII, the facial nerve pass through?
The internal auditory meatus, then through the petrous part of the temporal bone.
49
How many branches does CN VII, the facial nerve, give off?
5 extracranial and 2 intracranial (within petrous).
50
What structures does CN VII, the facial nerve, have a close relationship with?
Vestibulocochlear nerve. Middle ear. Parotid gland.
51
What can cause damage to CN VII, the facial nerve?
Idiopathic facial nerve palsy eg Bell's palsy.
52
How would you test for damage to CN VII, the facial nerve?
Test muscles of facial expression. Test corneal reflex (efferent limb). Test taste on anterior 2/3 of tongue.

AHNNS (17 decks)

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