Cranial Nerves

Question 1

What are the 5 distinct regions of the brain?

Answer 1

Pons and Medulla (Myelencephalon)
Cerebellum (metencephalon)
Midbrain (mesencephalon)
Thalamus/Hypothalamus
Cerebrum (telencephalon)

Question 2

What region do UMNs decussate?

Answer 2

Midbrain, at the Red Nucleus (major motor center)

Question 3

What’s the only nerve to directly associate with the cerebrum/telencephalon?

Answer 3

Olfactory (CN1)

Question 4

What’s the only nerve to directly associate with the thalamus?

Answer 4

Optic (CN2)

Question 5

Which cranial nerve is susceptible to CNS diseases rather than Peripheral nerve diseases?

Answer 5

Optic (CN2)

Question 6

What’s special about CN2?

Answer 6

It is the only cranial nerve that is not a peripheral nerve but an extension of the central nervous system.

Question 7

Trace the path of vision from the retina.

Answer 7

Retina –> Optic Nerve –> Optic Chiasm (decussation) –> LGN (in thalamus) –> Visual Cortex

Question 8

Trace the path of the pupillary light reflex

Answer 8

Retina –> Optic Nerve –> Optic Chiasm (decussation) –> LGN –> Pretectal Nucleus (decussation) –> PSNS Nucleus of Occulomotor (CN3) (decussation) –> Constriction of right pupil

Question 9

What is the net effect of CN3?

Answer 9

Move globe medially/towards the nose

Question 10

What does CN3 do?

Answer 10

PSNS efferent innervation to the eye

Innervate DMV Rectus, ventral oblique and levator palpebra muscle

Question 11

What does CN2 do?

Answer 11

carry visual input from retina to visual cortex

afferent PSNS innervation of the eye

Question 12

What does injury to CN3 look like?

Answer 12

Dilated pupil
Laterally rotated globe -> ventrolateral strabismus
Ptosis or drooping eyelid

Question 13

What causes Cats to have a unilateral D-shaped pupil?

Answer 13

Damage to Short Ciliary nerves in the retrobulbar space

Question 14

What is the CN4?

Answer 14

Trochlear nerve and innervates Dorsal Oblique which Rotates the eye

Question 15

What is CN6?

Answer 15

Abducens and innervates the Lateral Rectus and Retractor Bulbi muscle

Question 16

What would a lesion to CN6 look like?

Answer 16

Medial Strabismus with bulging eyes and inability to pull eyes back in response to threatening or painful stimuli

Question 17

How do you test CN3, 4, and 6?

Answer 17

Rotating the head side to side looking for normal vestibular nystagmus

Question 18

What is CN5?

Answer 18

Trigeminal Nerve and provides sensation to the face and motor to the muscles of mastication

Question 19

What branch of the trigeminal nerve carries innervation to muscles of mastication?

Answer 19

Mandibular

Question 20

How do you completely examine sensation of the face?

Answer 20

Test all branches of trigeminal nerve by stimulating muscles of the eye (ophthalmic), nose (maxillary) and mouth (mandibular)

Question 21

What is CN7?

Answer 21

Facial Nerve and innervates muscles of facial expression, tear production and the tongue (Rostral 2/3 of taste)

Question 22

What is CN9?

Answer 22

Glossopharyngeal nerve and innervates muscles of the pharynx and caudal 1/3 of tongue taste sensation

Question 23

What is CN8?

Answer 23

Vestibulocochoclear nerve and innervates the ear for hearing and balance

Question 24

What are clinical signs of injury to CN8?

Answer 24

Loss of balance, head tilt, falling
Nystagmus, Strabismus
Hearing loss

Question 25

What is a more sensitive test of hearing than banging pots and pans?

Answer 25

BAER - Brainstem Auditory Evoked Response Test

Question 26

What is nystagmus?

Answer 26

repepitive, uncontrolled movement of the eye

Question 27

What is strabismus?

Answer 27

improper location of the eye

Question 28

Where is the lesion with POSITIONAL strabismus

Answer 28

Vestibular injury

Question 29

What would lifting the head and getting a unilateral ventrolateral strabismus or eye droop indicate?

Answer 29

vestibular lesion on the same side

Question 30

What does a non-positional strabismus indicate?

Answer 30

not a CN8 lesion but CN3, 4 and 6 instead

Question 31

Dog has hardly any balance and falling/rolling/head tilt to the right, where's the lesion?

Answer 31

can be peripheral or central but most importantly its VESTIBULAR

Question 32

True or False. Horner's usually presents with Central Vestibular Lesions.

Answer 32

FALSE Horner's will RARELY present with Central lesions but will USUALLY accompany PERIPHERAL lesions. CN7, Horner's and Peripheral Vestibulocochlear nerves run together at level of the ear canal.

Question 33

True or False Central Vestibular Nystagmus changes with body positions?

Answer 33

TRUE. Peripheral lesions will not change but Central DO change.

Question 34

Vertical Nystagmus makes you think _______ right away!

Answer 34

Central Vestibular Lesion

Question 35

Where do CN 9, 10 and 11 come from?

Answer 35

Medulla!!

Question 36

What are the primary clinical signs associated with damage to CN 9, 10 and 11?

Answer 36

Pharynx and Larynx irregularities: Inability to swallow and inspiratory dyspnea Laryngeal paralysis

Question 37

What does the CN 11 do?

Answer 37

Spinal Accessory and innervates trapezius, brachiocephalicus and sternocephalicus