Week 18 - Clinical Lecture: Facial Nerve

Question 1

What is the seventh paired cranial nerve?

Answer 1

The facial nerve (CN VII)

Question 2

What are the primary functions of the facial nerve?

Answer 2

• Motor: muscles of facial expression, posterior belly of the digastric, stylohyoid, and stapedius muscles
• Sensory: small area around the concha of the external ear
• Special Sensory: taste sensation to the anterior 2/3 of the tongue
• Parasympathetic: supplies glands in the head and neck

Question 3

What are the glands supplied by the parasympathetic fibers of the facial nerve?

Answer 3

• Submandibular salivary gland
• Sublingual salivary gland
• Nasal mucous glands
• Palatine mucous glands
• Pharyngeal mucous glands
• Lacrimal glands

Question 4

What are the two main parts of the facial nerve’s anatomical course?

Answer 4

• Intracranial
• Extracranial

Question 5

Where does the facial nerve arise?

Answer 5

In the pons of the brainstem

Question 6

What are the two roots of the facial nerve?

Answer 6

• Large motor root
• Small sensory root (intermediate nerve)

Question 7

What important events occur within the facial canal of the facial nerve?

Answer 7

• The two roots fuse to form the facial nerve
• Formation of the geniculate ganglion
• Giving rise to the greater petrosal nerve, nerve to stapedius, and chorda tympani

Question 8

Through which foramen does the facial nerve exit the skull?

Answer 8

The stylomastoid foramen

Question 9

What is the first extracranial branch of the facial nerve?

Answer 9

The posterior auricular nerve

Question 10

What are the five terminal branches of the facial nerve within the parotid gland?

Answer 10

• Temporal branch
• Zygomatic branch
• Buccal branch
• Marginal mandibular branch
• Cervical branch

Question 11

What is the function of the chorda tympani branch of the facial nerve?

Answer 11

Innervates the anterior 2/3 of the tongue with the special sense of taste

Question 12

Fill in the blank: The _______ nerve carries parasympathetic fibers to the mucous glands and lacrimal gland.

Answer 12

Greater petrosal

Question 13

What is the clinical relevance of damage to the facial nerve?

Answer 13

Can produce varied symptoms depending on the site of the lesion

Question 14

What are the symptoms of intracranial lesions of the facial nerve?

Answer 14

• Paralysis or severe weakness of facial expression muscles
• Reduced salivation and loss of taste on ipsilateral 2/3 of tongue
• Ipsilateral hyperacusis
• Ipsilateral reduced lacrimal fluid production

Question 15

What is a common cause of intracranial lesions of the facial nerve?

Answer 15

Infection related to the external or middle ear

Question 16

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

Answer 16

• Parotid gland pathology
• Infection by herpes virus
• Compression during forceps delivery
• Idiopathic causes (Bell’s palsy)

Question 17

True or False: The facial nerve contributes to the innervation of the parotid gland.

Answer 17

False

Question 18

What are the two types of sensory functions of the facial nerve?

Answer 18

Special sensory (taste) and somatic (general) sensory

Question 19

What types of motor functions does the facial nerve carry?

Answer 19

Somatic (branchial) motor and visceral (parasympathetic) motor

Question 20

What type of fibers does the facial nerve carry from the muscles it innervates?

Answer 20

Proprioceptive fibers

Question 21

Where is the motor nucleus of the facial nerve located?

Answer 21

In the ventrolateral part of the pons of the brainstem

Question 22

Where are the cell bodies of the primary sensory neurons of the facial nerve located?

Answer 22

In the geniculate ganglion

Question 23

The central processes of taste sensory neurons end in which nuclei?

Answer 23

The nuclei of the solitary tract in the medulla

Question 24

The processes of general sensation sensory neurons from the external ear end in which nucleus?

Answer 24

The spinal nucleus of the trigeminal nerve

Question 25

What are the two divisions in which the facial nerve (CN VII) emerges?

Answer 25

The primary root and the intermediate nerve

Question 26

What does the larger primary root of the facial nerve innervate?

Answer 26

The muscles of facial expression

Question 27

What types of fibers does the smaller intermediate nerve carry?

Answer 27

Taste, presynaptic parasympathetic, and somatic sensory fibers

Question 28

List the structures CN VII traverses during its course.

Answer 28

* Posterior cranial fossa * Internal acoustic meatus * Facial canal * Stylomastoid foramen * Parotid gland

Question 29

What is the sharp bend in the course of the facial nerve called?

Answer 29

Geniculum of the facial nerve

Question 30

What is the site of the geniculate ganglion?

Answer 30

The geniculum of the facial nerve

Question 31

What are the three branches CN VII gives rise to while traversing the temporal bone?

Answer 31

* Greater petrosal nerve * Nerve to the stapedius * Chorda tympani nerve

Question 32

What are the five terminal motor branches of the parotid plexus formed by CN VII?

Answer 32

* Temporal * Zygomatic * Buccal * Marginal mandibular * Cervical

Question 33

Which embryonic structure does the facial nerve supply?

Answer 33

The 2nd pharyngeal arch

Question 34

What muscles are mainly supplied by the facial nerve?

Answer 34

* Muscles of facial expression * Auricular muscles * Posterior belly of the digastric * Stylohyoid * Stapedius

Question 35

What does the facial nerve provide presynaptic parasympathetic fibers to?

Answer 35

* Pterygopalatine ganglion * Submandibular ganglion

Question 36

What glands are innervated by the pterygopalatine ganglion?

Answer 36

* Lacrimal * Nasal * Palatine * Pharyngeal

Question 37

What glands are innervated by the submandibular ganglion?

Answer 37

* Sublingual salivary gland * Submandibular salivary gland

Question 38

True or False: The pterygopalatine ganglion is associated with the maxillary nerve (CN V2).

Answer 38

True

Question 39

What type of sensory fibers accompany the auricular branch of the vagus nerve?

Answer 39

Some fibers from the geniculate ganglion

Question 40

Fill in the blank: Peripheral fibers of sensory neurons of the geniculate ganglion are carried by the _______.

Answer 40

Chorda tympani

Question 41

Which nerve does the chorda tympani join to supply taste buds?

Answer 41

Lingual nerve of CN V3

Question 42

What regions do the taste fibers supplied by the chorda tympani serve?

Answer 42

Taste buds of the anterior two thirds of the tongue and soft palate

Question 43

Where do central fibers of taste neurons pass to after leaving the geniculate ganglion?

Answer 43

To the brainstem via the intermediate nerve

Question 44

Which cranial nerve is the most frequently paralyzed among motor nerves?

Answer 44

CN VII ## Footnote CN VII is also known as the facial nerve.

Question 45

What functions may be lost with a lesion of CN VII near its origin or the geniculate ganglion?

Answer 45

Loss of motor, gustatory (taste), and autonomic functions ## Footnote This includes paralysis of facial muscles and altered secretion of glands.

Question 46

What type of paralysis occurs with a central lesion of CN VII?

Answer 46

Paralysis of muscles in the inferior face on the contralateral side ## Footnote Forehead wrinkling remains unaffected due to bilateral innervation.

Question 47

What is the effect of lesions between the geniculate ganglion and the origin of the chorda tympani?

Answer 47

Produces the same effects as lesions near the ganglion, except lacrimal secretion is not affected ## Footnote This indicates that some autonomic functions may remain intact.

Question 48

How is CN VII vulnerable to injury?

Answer 48

It is vulnerable to compression from viral infections and inflammation ## Footnote This often occurs just before the nerve emerges from the stylomastoid foramen.

Question 49

What types of injuries are common to CN VII?

Answer 49

Knife and gunshot wounds, cuts, birth injury, and temporal bone fractures ## Footnote Damage is usually detectable immediately after the injury.

Question 50

What conditions can affect CN VII?

Answer 50

- Tumors - Aneurysms - Meningeal infections - Herpes viruses ## Footnote These conditions can lead to paralysis of facial muscles.

Question 51

Is sensory loss common with injuries to CN VII?

Answer 51

No, sensory loss in the skin on the posteromedial surface of the auricle is rare ## Footnote Hearing is usually not impaired, but sensitivity to low tones may increase.

Question 52

What is Bell palsy?

Answer 52

A unilateral facial paralysis of sudden onset resulting from a lesion of CN VII ## Footnote It is a specific condition that affects facial muscle control.