Session 5 - Cranial Nerved VIII - XII

Question 1

Describe the type of fibres, route and function of the Vestibulocochlear nerve CN VIII.

Answer 1

Special Sensory
Route: Through internal auditory meatus > to chochlea.

Function:
Sensory of Hearing! + Balance

Question 2

How is the vestibulocochlear nerve CN VIII tested, and what problems can occur with the nerve?

Answer 2

• Test Hearing, and enquire about balance.

Problems

• Damage to nerve, brainstem of cochlea can cause hearing loss.
• Presbyacusis - Old age related sensorineural hearing loss (often bilateral).
• Acoustic neuroma - benign tumour involving vestubulocochlear nerve.

Question 3

What are acoustic neuromas? What are the symptoms?

Answer 3

Benign tumours of the swann cells surrounding the vestibular component of CN VIII.
Can compress nerve and other CNs in proximity.

• Unilateral hearing loss
• Tinnitus
• Vertigo
• Numbness
• Pain or weakness down one half of face.

Question 4

Name the cranial nerves which arise from the medulla oblongata.

Answer 4

Glossopharyngeal (IX)
Vagus (X)
Accessory (XI)
Hypoglossal (XII)

Question 5

What is the route of the glossopharyngeal nerve?

Answer 5

From the medulla, exits through base of the skull through the jugular foramen.
Descends down the neck, before heading to parts of the tongue and pharynx.

Question 6

What types of axons are in the glossopharyngeal?

Answer 6

Main function is general sensory.

Some special sensory, autonomic, and motor functions too.

Question 7

What are the functions of the glossopharyngeal CN IX nerve?

Answer 7

General Sensory
- Sensation of soft palate, tonsils and pharynx

Special Sensory

• Middle ear and tympanic membrane (inner surface)
• Sensory from carotid body + sinus
• Taste, general sensation post. 1/3 tongue

Autonomic
- innervation of parotid gland

Muscular
- Supplies stylopharyngeus (only)

Question 8

How is the glossopharyngeal nerve CN IX tested?

Answer 8

Sensory - Gag reflex

Taste (not formally tested)

Tested in conjunction with CN X (vagus)

Question 9

What is the route of the Vagus Nerve CN X?

Answer 9

Medulla > Jugular foramen > Carotid sheath

Question 10

What are the functions of the Vagus Nerve?

Answer 10

General Sensory
- Sensory to lower pharynx and larynx
Motor
- Muscles of soft palate, pharynx + larynx
Autonomic
- Parasympathetic to thoracic and abdominal viscera

Question 11

Where do the left and right recurrent laryngeal nerves go through? (branches of CN X)

Answer 11

Right recurrent = turns under right subclavian.

Left recurrent = turns under arch of aorta

Question 12

How is the vagus nerve tested for function?

Answer 12

• Noting the speech (controled by CN X)
• Swallowing / coughing
• Say ‘Ahhh’ - observing uvula
• Gag reflex (efferent limb!)

Question 13

How can observing the uvula tell us about the function of Vagus nerve?

Answer 13

Vagus innervated the muscles in the soft palate.
When patient says ‘ahhh’, lifts soft palate.
If there is a problem with one side of the vagus, the uvula will point in one direction (due to no muscle contraction on one side)

Question 14

What may happen with damage to the recurrent larygneal branch of the vagus nerve?

Answer 14

Hoarseness of voice, dysphonia (difficulty speaking)

Question 15

What is the route / special properties of the Accessory Nerve CN XI?

Answer 15

Has a Spinal and Cranial part.
We can forget about the cranial part!

Spinal roots come from spinal cord, and move UP through foramen magnum, and join the cranial roots, which merge forming the Accessory nerve.

Question 16

What is the route and function of the Accessory nerve CN XI?

Answer 16

Motor fibres only
Moves through the jugular foramen.

Function: Innervate the sternocleidomastoid and trapezius. (only the spinal roots do this)

Question 17

How is the Accessory Nerve CN XI tested?

Answer 17

Shrug shoulder against resistance.

Turn head against resistance.

Question 18

Where does the Accessory nerve travel in the neck? What is the clinical relevance?

Answer 18

Through POSTERIOR TRIANGLE.

Susceptible to damage in this area, e.g. surgery, biopsy of lymph node etc.

Question 19

What is a sign that the accessory nerve may be damaged?

Answer 19

Atrophy to trapezius muscle, causing increased angle from neck to shoulders.

Question 20

What is the route and function of the hypoglossal nerve CX VII?

Answer 20

Motor function only.
Route: Through hypoglossal canal > down neck, over arteries > underneath tongue > innervates tongue

Function: Motor supply to muscles of tongue

Question 21

How is the hypoglossal nerve function tested?

Answer 21

Inspection of movement of tongue (get them to move around mouth etc)
(left half of tongue = left hypoglossal, vice versa)

Question 22

What conditions can injury to hypoglossal nerve cause?

Answer 22

Rare
Can cause atrophy and weakness of muscles of tongue, on same side of tongue as the side that the nerve is injured.
(ipsilateral)