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Yr 2 - Control > Facial Nerve Revision > Flashcards

Facial Nerve Revision Flashcards

1
Q

What are the modalities of the facial nerve?

A
  1. Motor
  2. Sensory
  3. Special sensory
  4. Parasympathetic
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2
Q

What is the motor function of the facial nerve?

A
  • Stapdeius
  • Posterior belly of digastric
  • Stylohyoid
  • Muscles of facial expression (via 5 terminal motor branches)
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3
Q

What is the somatic sensory function of the facial nerve?

A

A small area around the concha of the external ear

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4
Q

What is the special sensory function of the facial nerve?

A

Taste - anterior 2/3 of tongue via the chorda tympani

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5
Q

What is the parasympathetic function of the facial nerve?

A

Glands of head and neck EXCEPT parotid:

  • Submandibular and sublingual salivary glands
  • Lacrimal glands
  • Nasal, palatine and pharyngeal mucous glands.
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6
Q

Anatomically, the course of the facial nerve can be divided into two parts:

A
  • Intracranial: the course of the nerve through the cranial cavity, and the cranium itself.
  • Extracranial: the course of the nerve outside the cranium, through the face and neck.
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7
Q

Where does CN VII emerge from?

A

Cerebellopontine angle (ventral aspect of pons)

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8
Q

How does the facial nerve enter the cranium?

A

Through the internal acoustic meatus in the petrous part of the temporal bone –> closely related to inner ear here

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9
Q

Where is the internal acoustic meatus?

A

Petrous part of temporal bone

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10
Q

Still within the temporal bone, the roots leave the internal acoustic meatus, and enter what?

A

The facial canal –> this is ‘Z’ shaped

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11
Q

Within the facial canal in the temporal bone, what ganglion is formed by the facial nerve?

A

The geniculate ganglion

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12
Q

What is the geniculate ganglion?

A
  • A collection of pseudounipolar sensory neurons of the facial nerve located in the facial canal of the temporal bone.
  • Function:
    • Sensory ganglion of the facial nerve
    • Contains cell bodies of the fibres responsible for conducting taste sensation from the anterior 2/3 of tongue
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13
Q

Within the facial canal in the temporal bone, what 3 branches does the facial nerve give rise to?

A
  1. Greater petrosal nerve
  2. Nerve to stapedius
  3. Chorda tympani
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14
Q

What is the function of the greater petrosal nerve? What type of nerve is it?

A
  • Type:
    • Mixed nerve - carrying parasympathetic, taste, and sensory fibers
  • Sends parasympathetic fibres to the mucous glands and lacrimal gland.
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15
Q

What is the function of the nerve to stapedius? What is the function of stapedius?

A
  • Nerve: Sends motor fibres to stapedius muscles of the middle ear
  • Function: Stapedius dampens the vibrations of the stapes helping to control the amplitude of sound waves
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16
Q

What can damage to the nerve to stapedius result in?

A

Resulting paralysis of stapedius leads to hypersensitivity to loud noises (hyperacusis).

17
Q

What is the function of chorda tympani?

A

Special sensory: innervates taste to the anterior 2/3 of the tongue (carries taste back to brain)

Parasympathetic: Fibres to the submandibular and sublingual glands (via lingual nerve)

18
Q

After arising in the facial canal, which nerve does the chorda tympani ‘hitch hike’ with? Why?

A
  • ‘Hitchhikes’ with the lingual nerve.
  • The parasympathetic fibres of the chorda tympani stay with the lingual nerve, but the main body of the nerve leaves to innervate the anterior 2/3 of the tongue (taste)
19
Q

After giving off these branches in the facial canal, where does the facial nerve exit the cranium?

A

Via the stylomastoid foramen

20
Q

Where is the stylomastoid foramen?

A

located just posterior to the styloid process of the temporal bone.

21
Q

After exiting the skull, and before dividing into its terminal motor branches, what does the facial nerve supply?

A
  • Posterior auricular nerve –> motor innervation to the some of the muscles around the ear
  • Motor innervation to the posterior belly of digastric and to the stylohyoid muscle
22
Q

After innervating the posterior belly of the digastric muscle and the stylohyoid muscle, where does the facial nerve then pass?

A

continues anteriorly and inferiorly into the parotid gland –> the facial nerve does not contribute towards the innervation of the parotid gland, which is innervated by the glossopharyngeal nerve

23
Q

Within the parotid gland, how does the facial nerve terminate?

A

By splitting into 5 motor branches which supply the muscles of facial expression:

  • Temporal
  • Zygomatic
  • Buccal
  • Marginal meningeal
  • Cervical
24
Q

Intracranial lesions occur during the intracranial course of the facial nerve (proximal to the stylomastoid foramen). What would be the effect of this on:

  • Muscles of facial expression?
  • Tongue?
  • Salivation?
  • Hearing?
  • Lacrimal fluid production?
A
  • Muscles of facial expression will be paralysed or severely weakened - 5 terminal branches
  • Loss of taste on the ipsilateral 2/3 of tongue - chorda tympani
  • Reduced salivation - chorda tympani via lingual nerve
  • Ipsilateral hyperacusis (hypersensitive to sound) - nerve to stapedius
  • Ipsilateral reduced lacrimal fluid production - greater petrosal nerve
25
Q

Define ipsilateral

A

belonging to or occurring on the same side of the body.

26
Q

What is the most common cause of an intracranial lesion of the facial nerve?

A

Infection related to the external or middle ear

27
Q

What is Bell’s palsy?

A

Bell’s palsy is temporary weakness or lack of movement affecting 1 side of the face

28
Q

Extracranial lesions occur during the extracranial course of the facial nerve (distal to the stylomastoid foramen). What is the only function of the facial nerve that is affected?

A

The motor function (as other branches given off intracranially)

29
Q

What do extracranial lesions of the facial nerve result in?

A

paralysis or severe weakness of the muscles of facial expression.

30
Q

What are 4 causes of extracranial lesions of the facial nerve?

A
  1. Parotid gland pathology – e.g a tumour, parotitis, surgery.
  2. Infection of the nerve – particularly by the herpes virus.
  3. Compression during forceps delivery – the neonatal mastoid process is not fully developed and does not provide complete protection of the nerve.
  4. Idiopathic – If no definitive cause can be found then the disease is termed Bell’s palsy.

Yr 2 - Control (71 decks)

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