Gross Anatomy of the Cranial Nerves

Question 1

What are the different sections of the course of a cranial nerve?

Answer 1

CNS part, intracranial part, base of skull part to exit foramen, extracranial part

Question 2

Where is the intracranial part of the cranial nerve course?

Answer 2

Between point of connection with the CNS and their respective base of skull foraminae

Question 3

What cranial nerve exits via the cribiform plate of the ethmoid bone?

Answer 3

CN I

Question 4

Where does CN II exit the skull?

Answer 4

The optic canal

Question 5

What cranial nerves exit via the superior orbital fissure?

Answer 5

CN III, IV, V1 and VI

Question 6

Where do V2 and V3 exit the skull?

Answer 6

V2 = foramen rotundum
V3 = foramen ovale

Question 7

What cranial nerves exit via the internal acoustic meatus?

Answer 7

CN VII and VIII

Question 8

What cranial nerves exit the skull through the jugular foramen?

Answer 8

CN IX, X and XI

Question 9

Where does CN XII exit the skull through?

Answer 9

The hypoglossal canal

Question 10

What are the sensory dermatomes of the trigeminal nerve?

Answer 10

CN V1 = forehead, upper eyelid, tip of nose
CN V2 = mid cheek, lower eyelid, nostril of nose
CN V3 = mid cheek, lower lip, chin

Question 11

How do you test the sensory component of the trigeminal nerve?

Answer 11

Ask patient to close their eyes and gently brush skin in each dermatome with fine tip of cotton wool = ask patient to tell you when they feel it and compare each side

Question 12

How do you test the motor component of the trigeminal nerve?

Answer 12

Palpate strength of contraction of masseter and temporalis by getting patient to clench teeth
Ask patient to open jaw against resistance

Question 13

How do you test the motor part of CN VII?

Answer 13

Ask patient to frown, close eyes tightly, smile and puff out cheeks

Question 14

How do you test the vagus nerve?

Answer 14

Ask patient to say ah = motor test, uvula should lift straight up, also tests CN V3
Ask patient to swallow small amount of water = watch larynx and for splutter
Listen to speech for hoarseness
Ask patient to cough

Question 15

How is the spinal accessory nerve connected to the CNS?

Answer 15

Via cervical spinal nerve anterior rootlets to the spinal cord

Question 16

What is the intracranial part of the spinal accessory nerve?

Answer 16

Ascends through the foramen magnum then travels towards jugular foramen in posterior cranial fossa

Question 17

Where does the spinal accessory nerve course along the base of the skull?

Answer 17

Junction between the temporal and occipital bones

Question 18

What is the extracranial part of the spinal accessory nerve?

Answer 18

Axons supply sternocleidomastoid on deep surface then continue across posterior triangle of neck deep to investing fascia and supply trapezius

Question 19

Ho do you test the spinal accessory nerve?

Answer 19

Ask patient to shrug shoulders

Ask patient to turn head to look up towards opposite side

Question 20

How do you tell the named nerves of the cervical plexus apart from the extracranial part of the spinal accessory nerve?

Answer 20

Named nerves also pass deep to midpoint of posterior border of sternocleidomastoid but don’t pass deep to trapezius

Question 21

How does the hypoglossal nerve connect to the CNS?

Answer 21

Via many rootlets that attach lateral to pyramids of the medulla oblongata

Question 22

What is the intracranial part of the hypoglossal nerve?

Answer 22

Passes anteriorly towards the hypoglossal canal in the posterior cranial fossa

Question 23

Where does the hypoglossal nerve course along the base of the skull?

Answer 23

Along the occipital bone

Question 24

What does the hypoglossal nerve supply?

Answer 24

Most of the muscles of the tongue, except palatoglossus

Question 25

What is the extracranial part of the hypoglossal nerve?

Answer 25

Descends in neck lateral to carotid sheath, passes anteriorly at level of hyoid bone towards lateral aspect of tongue

Question 26

How do you test the hypoglossal muscle?

Answer 26

Ask patient to stick tongue straight out = tongue tip should remain in midline