3.5 Cranial Nerves VIII-XII

Question 1

What is the function of CN VIII?

Answer 1

• Balance
• Eye movement
• Hearing

Question 2

Is CN VIII sensory, motor or both?

Answer 2

Purely sensory

Question 3

CN VIII has two pairs of nuclei in the brainstem. What are they called (very difficult question)

Answer 3

• Vestibular nuclei
• Cochlear nuclei

Question 4

Describe the course of CN VIII

Answer 4

• Two components arise from brainstem
• Form CN VIII, and head out through internal acoustic meatus
• Distally within the meatus, it splits back into the vestibular and cochlear nerve

Question 5

What are some features of CN VIII palsy?

Answer 5

• Sensorineural hearing loss
• Tinnitus
• Vertigo
• Nystagmus

Question 6

What kinds of functions does the glossopharyngeal nerve have?

Answer 6

All of them:
- Somatic sensory (posterior 1/3 of tongue, pharynx, external ear and eardrum)
- Visceral sensory (carotid body)
- Special sensory (taste from posterior 1/3 of tongue)
- Motor (elevating larygnx and pharynx)
- Parasympathetic motor (parotid glands)

Question 7

What are the functions of the vagus nerve?

Answer 7

Everything except visceral sensory:
- Somatic sensory (larynx/laryngopharynx)
- Special sensory (taste at root of tongue)
- Motor (muscles of pharynx, soft palate and larynx)
- Parasympathetic (smooth muscle of trachea, bronchi, GI tract, and heart)

Question 8

Where do CN IX and X emerge from the brain?

Answer 8

Around the olives of the medulla

Question 9

How do CN IX, X, and XI exit the cranial cavity?

Answer 9

Jugular foramen

Question 10

Which nerves control the afferent/efferent limbs of the gag reflex?

Answer 10

• Afferent: CN IX
• Efferent: CN X

Question 11

In a CN IX/X palsy, will the uvula deviate towards or away from the affected side?

Answer 11

Away

Question 12

What are some obvious features of CN IX/X palsy?

Answer 12

• Absent gag reflex
• Deviated uvula
• Laryngeal paralysis (dysphonia)

Question 13

What are some subtle features of a CN IX/X palsy?

Answer 13

• Difficulty swallowing
• Parotid dysfunction
• Loss of taste over posterior third of tongue
• Loss of sensation over posterior third of tongue

Question 14

Is CN XI sensory, motor, or both?

Answer 14

Purely motor; innervates SCM and upper trapezius

Question 15

Describe the course of CN XI

Answer 15

Has a spinal portion and a cranial portion:
- Spinal portion arises from C1-C5; goes to innervate upper traps and SCM
- Cranial portion arises from medulla, and joins vagus nerve

Question 16

How does CN XI enter/exit the cranium?

Answer 16

Enters via foramen magnum. Exits via jugular foramen.

Question 17

Does the hypoglossal nerve have sensory function, motor function, or both?

Answer 17

Purely motor; intrinsic and extrinsic muscles of the tongue.

Question 18

Describe the course of the hypoglossal nerve

Answer 18

• Arises from hypoglossal nucleus in medulla
• Emerges from pre-olivary sulcus in the medulla
• Exits cranial cavity via hypoglossal canal

Question 19

Describe the presentation of a hypoglossal palsy

Answer 19

• Deviation towards affected side
• Possible muscle wasting/fasciculations on affected side