Cranial nerves

Question 1

What are the 12 cranial nerves?

Answer 1

CN1 - olfactory
CN2 - optic
CN3 - oculomotor
CN4 - trochlear
CN5 - trigeminal
CN6 - abducens
CN7 - facial
CN8 - vestibulocochlear
CN9 - glossopharyngeal
CN10 - vagus
CN11 - spinal accessory
CN12 - hypoglossal

Question 2

What are the cranial nerves with only motor modalities?

Answer 2

CN 3, 4, 6, 11, 12

Question 3

What cranial nerves have only special sensory modality?

Answer 3

CN 1,2 and 8

Question 4

What 2 cranial nerves have both motor and special sensory?

Answer 4

Facial nerve (CN 7) and glossopharyngeal nerve (CN 9)

Question 5

What 1 nerve has sensory, special sensory and motor modalities?

Answer 5

Vagus nerve (CN10)

Question 6

What passes through the optic canal?

Answer 6

Optic nerve and ophthalmic artery

Question 7

What passes through the foramen rotundum?

Answer 7

Maxiliary nerve (CN V2)

The 2nd branch of trigeminal nerve.

Question 8

What passes through the foramen ovale?

Answer 8

Mandibular nerve (CN V3) - 3rd branch of trigeminal nerve
Accessory meningeal artery
Lesser petrosal nerve

Question 9

What passes through the foramen spinosum?

Answer 9

Middle meningeal artery (passes under the pterion) and the middle meningeal vein.
Meningeal branch of mandibular nerve

Question 10

What passes through superior orbital fissure?

Answer 10

Oculomotor nerve (CN 3)
Trochlear nerve (CN 4)
Ophthalmic nerve (CN V1) - 1st branch of trigeminal nerve
Abducens nerve (CN 6)
Superior ophthalmic vein

Question 11

What passes through the carotid canal?

Answer 11

Internal carotid artery
Nerve plexus

Question 12

What passes through the internal accoustic meatus?

Answer 12

Facial nerve (CN7)
Vestibulocochlear nerve(CN8)
Labrythine artery

Question 13

What passes through the jugular foramen?

Answer 13

Inferior petrosal sinus
Glossopharyngeal nerve (CN9)
Vagus nerve (CN10)
Spinal Accessory nerve (CN11)
Sigmoid sinus
Posterior meningeal artery

Question 14

What passes through hypoglossal canal?

Answer 14

Hypoglossal nerve (CN12)

Question 15

What passes through the foramen magnum?

Answer 15

Medulla oblongata
Vertebral arteries
Spinal roots of accessory nerves

Question 16

Trigeminal nerve is the only cranial nerve to attach to the pons directly. True/false?

Answer 16

True

Question 17

CNV3 supplies sensation to skin over the mandible and temperomandibular joint, except for what part?

Answer 17

Angle of the mandible and some of the external ear which is supplied by the greater auricular nerve (comes off spinal nerves C2, C3).

Question 18

Clinical testing for CN 5?

Answer 18

Sensory:
1. Ask patient to close eyes.
2. Gently brush skin in each dermatome with fine tip of cotton wool.
3. Ask patient to tell you when they feel skin being touched.

Motor:
1. Palpate the strength of contraction of the masseter and temporalis by asking patient to clench teeth.
2. Ask patient to open jaw against resistance.

Question 19

Clinical testing for CN 7?

Answer 19

Ask patient to:
- Frown
- Close eyes tightly
- Smile
- Puff out cheeks

Question 20

Clinical testing for CN 10?

Answer 20

Ask patient to say “ah” - also tests the maxilliary nerve.
- Motor function
- Uvula should lift up in midline
- Unilateral pathology will pull the uvula to 1 side.

Ask patient to swallow some water.
- Watch movement of larynx, splutter could suggest abnormal swallow.

Listen to speech - hoarseness could suggest abnormal muscle function of larynx.

Ask patient to cough (also requires diaphragm).

Question 21

A blown pupil is pathological for what cranial nerve?

Answer 21

Cranial nerve 3

Question 22

What does blown out pupil mean?

Answer 22

a pupil that is largely dilated and unresponsive to light

Question 23

What nerve has the longest intracranial course and as a result of this is most likely to be affected by raised intracranial pressure?

Answer 23

Trochlear nerve (CN 4)

Question 24

What is the main action of CN 6?

Answer 24

Abducens nerve = abduction of eye

Question 25

What is functions of CN V3?

Answer 25

Supply sensation to skin of face Motor to muscles of mastication PLUS tensor tympani, tensor veli palitini Parasympathetics to glands (salivary and lacrimal)

Question 26

Foramen pathway of trigeminal nerve branches?

Answer 26

V1 = superior orbital fissure V2 = foramen rotundum V3 = foramen ovale

Question 27

Forehead sparing occurs in defect with the LMN. True/false?

Answer 27

False UMN = FOREHEAD SPARING: corticospinal tract = stroke, MS LMN = facial nerve/facial motor nucleus = Bell’s palsy, Ramsey hunt

Question 28

What to check with CN 7?

Answer 28

Corneal reflex Ask about taste (supplies taste to anterior 2/3rd tongue) Facial movements e.g. raise eyebrows, puff cheeks

Question 29

Cranial nerve 3 palsy?

Answer 29

Oculomotor palsy = "down and out" eye with ptosis and dilated pupil.

Question 30

Cranial nerve 4 palsy?

Answer 30

Trochlear palsy = "double vision (diplopia) when going downstairs" Vertical diplopia exacerbated looking down OR can have head tilt AWAY from affected side in attempt to accommodate.

Question 31

Cranial nerve 6 palsy?

Answer 31

Abducens palsy = diplopia with resting eye in adduction. (unopposed medial rectus due to problem with lateral rectus). Unable to abduct the eye.

Question 32

The afferent limb of the corneal reflex is carried by what cranial nerve?

Answer 32

Ophthalmic branch of trigeminal nerve

Question 33

For a lesion in the CN 10, what way will the uvula deviate?

Answer 33

The uvula will deviate in the opposite direction from the lesion.

Question 34

Apart from uvular deviation what other features can occur due to a lesion of CN 10?

Answer 34

Central lesions of the vagus nerve can cause dysphagia, dysarthria and hoarseness; uvula deviation (towards the opposite side of the lesion); and transient parasympathetic effects.

Question 35

What feature can occur due to damage of the hypoglossal nerve (CN 12)?

Answer 35

Damage to the hypoglossal nerve causes paralysis of the tongue. Usually, one side of the tongue is affected, and when the person sticks out his or her tongue, it deviates or points toward the side that is damaged.