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ENT Advanced > Applied Anatomy Of The Cranial Nerves > Flashcards

Applied Anatomy Of The Cranial Nerves Flashcards

1
Q

Where does the oculomotor nerve originate from and which two arteries does it run between?

A

Anterior aspect of the midbrain

Moves anteriorly, passing below the posterior cerebral artery and above the superior cerebellar artery

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2
Q

Where does the oculomotor nerve go after the two arteries?

A

Pierces the dura mater

Enters the lateral aspect of the cavernous sinus

Receives sympathetic fibres from the internal carotid plexus which travel in its sheath but don’t combine

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3
Q

Through which fissure does the oculomotor nerve leave the cranial cavity? What happens to it?

A

Superior orbital fissure

Divides into superior and inferior fibres

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4
Q

What does the superior branch of the oculomotor nerve do?

A

Motor innervation to superior rectus and levator palpebrae superioris

Sympathetic fibres running with it to innervate the superior tarsal muscle

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5
Q

What does the inferior branch of the oculomotor nerve supply?

A

Motor innervation to the inferior and medial rectus and inferior oblique

Parasympathetic fibres to the ciliary ganglion - sphincter pupillae and ciliary muscles

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6
Q

What are the causes of a lesion to the oculomotor nerve?

A

Increase intracranial pressure, compressing it against the temporal bone

Aneurysm of the posterior cerebral artery

Cavernous sinus infection or trauma

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7
Q

Clinical signs of oculomotor nerve lesion?

A

Ptosis due to paralysis of LPS

Eyeball is down and out - paralysis of superior rectus, medial rectus and inferior oblique.

Unable to elevate, depress or adduct the eye

Dilated pupil due to unopposed action of the dilator pupillae

If proximal to the ciliary ganglion, loss of accommodation

If distal to ciliary ganglion, pupils of both eyes will be equal

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8
Q

Which is the largest cranial nerve?

A

Trigeminal nerve

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9
Q

What is the trigeminal nerve associated with?

A

Derivatives of the first pharyngeal arch

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10
Q

What is a nucleus?

A

A collection of nerve cell bodies within the CNS

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11
Q

Where does the trigeminal nerve originate from?

A

Three sensory nuclei -mesencephalic -principle sensory sensory -spinal nuclei of trigeminal nerve

They merge at the level of the pons to form a sensory root

And one motor nucleus (motor nucleus of the trigeminal nerve) extending from the midbrain to the medulla which forms a motor root

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12
Q

What is a ganglion?

A

A collection of nerve cell bodies outside of the CNS

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13
Q

What happens to the roots of the trigeminal nerve at the middle cranial fossa?

A

Sensory root expands into the trigeminal ganglion which is lateral to the cavernous sinus in a depression of the temporal bone called the trigeminal cave

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14
Q

What branches does the peripheral aspect of the trigeminal ganglion give rise to?

A

Ophthalmic (V1)

Maxillary (V2)

Mandibular (V3)

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15
Q

What do the divisions of the trigeminal nerve exit the cranium via?

A

Ophthalmic - superior orbital fissure

Maxillary - foramen rotundum

Mandibular - foramen ovale, entering the infratemporal fossa

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16
Q

What are the terminal branches of the ophthalmic nerve?

A

Frontal

Lacrimal

Nasociliary

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17
Q

What does the ophthalmic nerve innervate?

A

Skin and mucous membranes of derivatives of the frontonasal prominence: -forehead and scalp -cornea -frontal and ethmoidal sinuses -dorsum of nose -upper eyelid and conjunctiva

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18
Q

Where is parasympathetic innervation to the lacrimal gland derived from?

A

Postganglionic fibres from the pterygopalatine ganglion travel with the zygomatic branch of V2 (maxillary) and then join the lacrimal branch of V1

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19
Q

What is an absence of the corneal reflex a sign of?

A

Damage to the trigeminal, ophthalmic or facial nerve

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20
Q

What is the route for the corneal reflex?

A

Stimulation of cornea detected by ophthalmic nerve

Trigeminal ganglion

Trigeminal nerve nucleus in brainstem

Right/left facial nerve via inter-neurones

Orbicularis oculi contracts

Bilateral blinking

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21
Q

How many terminal branches does the maxillary nerve have?

A

14

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22
Q

What does the maxillary nerve innervate?

A

Skin, mucous membranes and sinuses of derivatives of the maxillary prominence of the first pharyngeal arch -lower eyelid and conjucntiva -cheeks and maxillary sinus -nasal cavity and lateral nose -upper lip -superior palate -upper molar, incisor and canine teeth and associated gingiva

23
Q

Where is the parasympathetic supply of the nasal glands derived from?

A

Post-ganglionic fibres travel with the nasopalatine and greater palatine nerves (branches of V2)

24
Q

What are the terminal branches of the mandibular nerve?

A

Buccal nerve

Inferior alveolar nerve

Auricotemporal nerve

Lingual nerve

25
Q

Where do the terminal branches of the mandibular nerve arise?

A

Infratemporal fossa

26
Q

Sensory supply of the mandibular nerve?

A

Mucous membranes and floor of the oral cavity

External ear

Lower lip

Chin

Anterior two thirds of tongue (general sensation)

Lower molar, incisor, canine teeth and associated gingiva

27
Q

What motor supply does the mandibular nerve do?

A

Muscles of mastication

Anterior belly of digastric muscle

Tensor vali palatini

Tensor tympani

28
Q

Parasympathetic innervation of the submandibular and sublingual glands?

A

Post-ganglionic fibres from the submandibular ganglion derived from the facial nerve, travel with lingual nerve to innervate these glands

29
Q

Parasympathetic supply of the parotid gland?

A

Post-ganglion fibres from the otic ganglion (derived from glossopharyngeal nerve) travel with the auricotemporal branch to innervate the parotid

30
Q

What is the facial nerve associated with?

A

Derivatives of the second pharyngeal arch

31
Q

From where and what does the facial nerve begin as?

A

Arises in the pons

Begins as a large motor root and a small sensory root (the branch from the sensory root known as the intermediate nerve)

32
Q

Where do the two roots of the facial nerve travel?

A

Through the internal acoustic meatus, an opening in the petrous part of the bone, in very close proximity to the inner ear

Within the temporal bone, then enter the facial canal which is Z shaped.

33
Q

What happens within the facial canal?

A

The motor root and sensory root fuse to form the facial nerve which forms the geniculate ganglion

Gives rise to the greater petrosal nerve, nerve to stapedius and chorda tympani

Then exits the facial canal and cranium via the stylomastoid foramen, just posterior to the styloid process

34
Q

What does the chorda tympani supply?

A

Taste to anterior two thirds of the tongue

35
Q

What is the first extracranial branch of the facial nerve and what does it innervate? Then where do the next branches go to?

A

Posterior auricular nerve

Motor innervation to some muscles around the ear

More branches go to the posterior belly of the digastric and the stylohyoid muscle

36
Q

Where does the facial nerve travel extracranially?

A

Exits skull, turns superiorly to run anterior to the outer ear

Continues to parotid gland where it terminates and splits into branches

37
Q

Name the terminal branches of the temporal nerve What do they innervate?

A

Temporal

Zygomatic

Buccal

Marginal mandibular

Cervical

Muscles of facial expression

38
Q

What does the posterior auricular nerve innervate?

A

Intrinsic and extrinsic muscles of the outer ear

Occipital part of the occipitofrontalis muscle

39
Q

What does the temporal branch of the facial nerve innervate?

A

Frontalis Orbicularis oculi Corrugator supercillii

40
Q

What does the zygomatic branch of the facial nerve innervate?

A

Orbicularis oculi

41
Q

What does the buccal branch of the facial nerve innervate?

A

Orbicularis oris Buccinator Zygomaticus

42
Q

What does the marginal mandibular branch of the facial nerve innervate?

A

Mentalis muscle

43
Q

What does the cervical branch of the facial nerve innervate?

A

Platysma muscle

44
Q

Which nerve does the chorda tympani hitchhike on?

A

Lingual nerve

45
Q

What does the greater petrosal nerve do?

A

Arises in the facial canal Exits temporal bone via middle cranial fossa Through foramen lacerum to pterygopalatine fossa Forms the pterygopalatine ganglion Branches do parasympathetic innervation to -mucous glands of oral cavity, nose and pharynx -lacrimal gland

46
Q

What forms the submandibular ganglion? What does it innervate?

A

Chorda tympani fibres which combine with the lingual nerve (branch of the trigeminal)

Branches travel to the submandibular and sublingual salivary glands

47
Q

What can cause intracranial lesions of the facial nerve?

A

Middle ear pathology such as a tumour or infection

48
Q

How can you tell if a lesion to the cranial nerve is intracranial or extracranial?

A

Intracranial: muscles of facial expression are paralysed or weakened and can get other symptoms Extracranial: only get loss of facial muscles

49
Q

What can cause an extracranial lesion of the facial nerve?

A

Parotid gland pathology eg tumour Infection of the nerve, especially herpes virus Compression from forceps delivery Idiopathic - Bell’s palsy

50
Q

Why can compression of the facial nerve happen in a forceps delivery?

A

Neonatal mastoid process is not fully developed so doesn’t provide complete protection of the nerve

51
Q

What does the oculomotor nerve do? (CN III)

A

Motor and parasympathetic innervation Motor -extra-ocular muscles (except lateral rectus and superior oblique) Parasympathetic -sphincter pupillae and ciliary muscles of the eye

52
Q

Signs/symptoms of damage to the chorda tympani?

A

Reduced salivation and loss of taste on ipsilateral two thirds of tongue

53
Q

Signs/symptoms if nerve to stapedius is damaged?

A

Ipsilateral hyperacusis

54
Q

Signs/symptoms of greater petrosal nerve damage?

A

Ipsilateral reduced lacrimal fluid production

ENT Advanced (24 decks)

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