8. Cranial Nerves VIII-XII

Question 1

What is the function of CN VIII, the vestibulocochlear nerve?

Answer 1

Special sensory - hearing and balance.

Question 2

Through which foramen does CN VIII, the vestibulocochlear nerve pass?

Answer 2

External auditory meatus, into petrous part of temporal bone.

Question 3

Damage to CN VIII, the vestibulocochlear nerve, causes what symptoms?

Answer 3

Hearing loss.
Presbyacusis (in both ears).
Vertigo and nystagmus.

Question 4

What other structures near CN VIII, the vestibulocochlear nerve, can be damaged causing the same symptoms as damage directly to the nerve?

Answer 4

The vestibulocochlear’s brainstem nucleus, cochlear, or semicircular canals.

Question 5

How would you test for damage to CN VIII, the vestibulocochlear nerve?

Answer 5

Test hearing.

Enquire about balance.

Question 6

An acoustic neuroma causes damage to CN VIII, the vestibulocochlear nerve. What is an acoustic neuroma?

Answer 6

Benign tumour of the Schwann cells surrounding the vestibular component of CN VIII. Their physical presence causes compression of the whole nerve and the CN in close proximity.

Question 7

Give 3 symptoms of an acoustic neuroma

Answer 7

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

Question 8

What is the function of CN IW, the glossopharyngeal nerve?

Answer 8

General sensory - general sensation of the soft palate, tonsils and oropharynx.
Special sensory - middle ear, tympanic membrane (inner ear), carotid body and sinus, taste and general sensation in posterior 1/3 tongue.
Autonomic - innervation of parotid gland.
Motor - supplies one muscle (stylopharyngeus).

Question 9

How would you test for damage to CN IX, the glossopharyngeal nerve?

Answer 9

Test gag reflex (sensory limb).

Taste.

Question 10

Isolated lesions of CN IX, the glossopharyngeal nerve, are rare. Therefore what nerve should it be tested in conjunction with?

Answer 10

CN X - vagus nerve.

Question 11

Through what foramen does CN IX, the glossopharyngeal nerve pass?

Answer 11

Jugular foramen.

Question 12

What is the function of CN X, the vagus nerve?

Answer 12

General sensory - to the lower pharynx and larynx.
Motor - innervates muscles of soft palate, pharynx and larynx.
Autonomic - parasympathetic supply to the thoracic and abdominal viscera.

Question 13

Through which foramen does CN X, the vagus nerve, pass?

Answer 13

Jugular foramen (then runs down to carotid sheath).

Question 14

CN X, the vagus nerves, give rise to the right and left recurrent laryngeal nerves. Under which artery does each run?

Answer 14

Right - turns under right subclavian.

Left - turns under arch of aorta.

Question 15

How would you test for damage to CN X, the vagus nerve?

Answer 15

Note speech.
Check swallow and cough,
Say ‘AHHH’ observing uvula, to check for deviation.
Test gag reflex (efferent limb, CN IX).

Question 16

What can injury to CN X, the vagus nerve, cause?

Answer 16

One sided soft palate paralysis.

Injury to recurrent laryngeal nerve branch causes hoarseness and dysphonia.

Question 17

What is the function of CN XI, the (spinal) accessory nerve?

Answer 17

Motor - innervate sternocleidomastoid and trapezius.

Question 18

Through which foramen in the skull does CN XI, the (spinal) accessory nerve pass?

Answer 18

Jugular foramen.

Question 19

Why is CN XI, the (spinal) accessory nerve, often referred to as spinal?

Answer 19

Has a cranial root from the medulla and a spinal root. Just test the spinal route.

Question 20

How would you test for damage to CN XI, the (spinal_ accessory nerve?

Answer 20

Shrug shoulders against resistance.

Turn head against resistance.

Question 21

Where is the easiest place to access CN XI, the (spinal) accessory nerve?

Answer 21

In the posterior triangle.

Question 22

What can cause damage to CN XI, the (spinal) accessory nerve?

Answer 22

Lymph node biopsies, surgery and stab wounds to the posterior triangle.

Question 23

What is the function of CN XII, the hypoglossal nerve?

Answer 23

Motor - innervates muscles of the tongue.

Question 24

Through which foramen in the skull does CN XII, the hypoglossal nerve, pass?

Answer 24

Hypoglossal canal.

Question 25

What arteries does XII, the hypoglossal nerve, cross in the neck?

Answer 25

Runs medial to the angle of the mandible, crossing the internal and external carotid arteries.

Question 26

How would you test for damage to CN XII, the hypoglossal nerve?

Answer 26

Inspection and movement of the tongue.

Question 27

What does damage to CN XII, the hypoglossal nerve cause?

Answer 27

Weakness and atrophy of the tongue muscles on the ipsilateral side.

Question 28

What cranial nerves arise from the medulla?

Answer 28

IX - glossopharyngeal.
X - vagus.
XI - accessory.
XII - hypoglossal.