Exam #2: Cranial Nerves IV

Question 1

List the five functional components of the facial nerve (CN VII).

Answer 1

1) SVE
2) SVA
3) GVE
4) GSA
5) GVA

Question 2

What is the SVE component of the facial nerve?

Answer 2

Brachimotor innervation (motor) to the muscles of facial expression

Question 3

What are the muscles of facial expression that are innervated by the facial nerve (CN VII)?

Answer 3

Platysma
Posterior belly of digastric
Stylohyoid 
Stapedius 
Auricularis
Occipitalis muscles

Question 4

What is the SVA function of the facial nerve (CN VII)?

Answer 4

Taste from the anterior 2/3 of the tongue

Question 5

What is the GVE function of the facial nerve (CN VII)?

Answer 5

PNS to the:

• Lacrimal
• Nasal
• Palatine
• Submandibular
• Sublingual glands

Question 6

What is the GSA function of the facial nerve (CN VII)?

Answer 6

General sensation from the skin:

• Posterior to the ear
• Pinna
• External auditory meatus

Question 7

What is the GVA function of the facial nerve (CN VII)?

Answer 7

Visceral sensation from the:

• Nasal cavity
• Soft palate
• Adjacent pharyngeal wall

Question 8

Where does the facial nerve emerge from the brain?

Answer 8

Ventrally at the Cerebello-pontine angle–which is lateral to the abducens

Question 9

What are the two roots of the facial nerve?

Answer 9

1) Facial nerve proper i.e. motor branch

2) Nervus intermedius

Question 10

What specifically does the “Facial Nerve Proper” consist of?

Answer 10

Axons whose cell bodies originate from the facial nucleus

Question 11

What is the function of the “Nervus Intermedius?”

Answer 11

• SVA, GSA, & GVA from neurons originating in the geniculate nucleus
• GVE from the superior salivary nucleus

Question 12

Where does the facial nerve initially pass through as it leaves the brain? What nerve accompanies it?

Answer 12

The facial nerves passes through the internal acoustic meatus w/ vestibulocochlear nerve to enter the facial canal

Question 13

Where is the internal acoustic meatus?

Answer 13

Petrous portion of the temporal bone in the skull

Question 14

What is the swelling of the facial nerve in the facial canal?

Answer 14

Geniculate ganglion, which is the ONLY sensory ganglion of the facial nerve

Question 15

What is the name of the sensory ganglion associated with the facial nerve?

Answer 15

Geniculate ganglion

Question 16

What are the names of the two PNS ganglia associated with the facial nerve?

Answer 16

1) Pterygopalatine ganglion

2) Submandibular ganglion

Question 17

What does the Pterygopalatine ganglion consist of?

Answer 17

Cell bodies of post-synaptic PNS neurons terminating in the:

1) Lacrimal gland
2) Nasal mucous membrane
3) Minor salivary gland

*****Note that b/c of this the Pterygopalatine ganglion is also referred to as the “hay fever ganglion.”

Question 18

What are the functions of the Pterygopalatine ganglion?

Answer 18

1) Lacrimal gland= tear formation
2) Nasal mucous membrane= nasal secretions
3) Minor salivary gland= salivary secretion

Question 19

What does the Submandibular ganglion consist of?

Answer 19

Cell bodies of post-synaptic PNS neurons terminating in the:

1) Submandibular gland
2) Sublingual gland

Question 20

What is the function of the Submandibular ganglion?

Answer 20

Submandibular gland & sublingual gland are BOTH involved in salivation

Question 21

What is the chorda tympani?

Answer 21

• Nerve that carries taste sensation from the anterior 2/3 of the tongue
• Joins the facial nerve (cranial nerve VII) inside the facial canal

Question 22

What is the nerve to the stapedius?

Answer 22

• Part of the facial nerve that innervates the stapedius m.

- Functions to dampen loud noises

Question 23

What happens when the stapedius is paralyzed?

Answer 23

Hyperacusis

Question 24

Through what foramen does the facial nerve exit the skull?

Answer 24

Stylomastoid foramen

Question 25

What are the three nuclei associated with the facial nerve?

Answer 25

1) Facial 2) Superior salivary 3) Solitary

Question 26

What does the facial nucleus contain?

Answer 26

Cell bodies of motor neurons (LMNs)

Question 27

What does the superior salivatory nucleus contain?

Answer 27

Cell bodies of pre-synaptic PNS neurons that synapse with the: 1) Pterygopalatine ganglia 2) Submandibular ganglia

Question 28

What does the solitary nucleus contain?

Answer 28

This is the nucleus that receives the central processes of taste fibers from the tongue

Question 29

What is crocodile/ aligator tear syndrome?

Answer 29

Lesion in the facial nerve proximal to the geniculate ganglion - Pre-ganglionic axons regenerate but make a wrong turn - Axons that should go to the submandibular gland via the chorda tympani - However, instead they join the greater petrosal nerve & go to t he pterygopalatine ganglion ****When the person starts eating, instead of producing saliva, the person produces tears on the affected side of the face

Question 30

What are the two tracts associated with the facial nerve?

Answer 30

1) Solitary Tract | 2) Spinal Tract of V

Question 31

What is the Solitary Tract?

Answer 31

This is the tract that carries taste sensation from the anterior 2/3 of the tongue to the thalamus & hypothalamus *****This tract mediates visceral responses (I.E VOMITING) to unpleasant stimuli.

Question 32

What is the Spinal Tract of V?

Answer 32

* ****The facial nerve does NOT have a pain nucleus | - Instead it relays nociception from the facial nerve to the spinal tract of V (Trigeminal nerve)

Question 33

What is the only cranial nerve to have a pain nucleus?

Answer 33

CN V (Trigeminal)

Question 34

What is the difference between the innervation of the upper & lower halves of the facial nucleus?

Answer 34

Upper= bilateral corticonuclear projections Lower= contralateral corticonuclear projections ONLY

Question 35

What is the pyramidal system? What type of smile is generated by the pyramidal system?

Answer 35

Conscious, voluntary control of facial movement that results in an "imitation smile."

Question 36

What structures do corticonuclear fibers pass through as they descend to the facial nucleus?

Answer 36

Genu | Posterior capsule

Question 37

What happens when there is a UMN lesion at the level of the genu?

Answer 37

Asymmetric smile

Question 38

What is the alternate pathway to the facial nucleus?

Answer 38

This is a pathway distinct from the pyramidal system that goes from: 1) Frontal lobe & basal ganglia 2) Reticular formation 3) Facial nucleus 4) LMN 5) Muscles of facial expression

Question 39

What type of smile is produced by the alternate pathway to the facial nucleus?

Answer 39

"Genuine smile"

Question 40

A patient s/p CVA with asymmetric smile has a symmetric smile in response to the sight of his granddaughter. What pathways is responsible for this?

Answer 40

CVA caused damage to the pyramidal system but the "Alternate pathway" is intact

Question 41

Outline the corneal blink reflex.

Answer 41

Afferent fibers = ophthalmic division of CN V (V.1) Efferent fibers= CN VII-->orbicularis oculi

Question 42

What is the difference between the direct & concensual pathway?

Answer 42

Direct= blink reflex in stimulated eye Consensual= blinck reflex in unstimulated eye

Question 43

What happens when there is a lesion of V.1 in the blink reflex?

Answer 43

Stimulation of affected eye= no blink in either eye Unaffected eye= bilateral blinking of BOTH eyes

Question 44

What happens when there is a lesion of CN VII in the blink reflex?

Answer 44

Affected= blink in opposite eye ONLY Unaffected= blink in ONLY the stimulated eye

Question 45

How does the pupillary light reflex compare to the corneal light reflex?

Answer 45

Pupil= - Afferent= optic - Efferent= CN III *****However, other general concepts (esp. in regards to lesions) remain the same

Question 46

Describe the typical presentation of Bell's Palsy.

Answer 46

Complete facial paralysis on the side of the face IPSILATERAL.

Question 47

Is Bell's Palsy an upper or lower motor neuron lesion?

Answer 47

Lower

Question 48

How does the presentation of Bell's Palsy change if the lesion is in the facial canal vs. distal to the facial canal?

Answer 48

In the facial canal= - Dry eye - Hyperacusis - Pain behind the ear - Diminished taste sensation Distal= paralysis ONLY

Question 49

Match the branches of the facial nerve that are effected to the symptoms of: dry eye, hyperacusis, pain behind the ear, & diminished taste sensation seen in Bell's Palsy w/ lesion in the facial canal.

Answer 49

- Dry eye= petrosal - Hyperacusis= nerve to stapedius - Pain behind the ear= posterior auricular (geniculate ganglion) - Diminished taste sensation= chorda tympani

Question 50

How will a UMN lesion affecting the facial nerve present?

Answer 50

Paralysis of the face BELOW THE EYE on the CONTRALATERAL side, without facial canal lesion symptoms