Cranial nerves

Question 1

A _______ does not require recognition by the cortex of the cerebrum, but a _______ does.

Answer 1

Reflex

Response

Question 2

What part of the brain is in control of wakefulness?

Answer 2

Ascending reticular activating system (ARAS)

Question 3

How would you determine if there was a lesion in the optic nerve?

Answer 3

Pupillary light reflex with a normal response of observing a mydriatic pupil turn into a mitotic pupil. (II In, III out)
Menace response with a normal response being flinching from a perceived threat. (II in, VII out)
Tracking movement of an object
Visual placement reaction

Question 4

You are testing a dog to determine if there is a lesion in the optic nerve. The menace response is normal, but the pupillary light reflex is not. What is going on?

Answer 4

That means that there is no lesion on the optic or the facial nerve, but there is probably something wrong with the oculomotor nerve.

Question 5

What is strabismus?

Answer 5

Static deviation of an affective eye from normal (due to a nerve lesion)

Question 6

If you notice a dog is exhibiting ptosis, what nerve is likely affected?

Answer 6

Oculomotor nerve, as it innervates the levator palpebrae superioris muscle.

Question 7

There is legion on the trochlear nerve, what is likely the clinical signs you would see in a dog?

Answer 7

It is difficult to see dogs as they have rounded pupils. However, you would likely see the ventral pupil being pulled medially as the dorsal pupil can not be pulled medially due to the cranial nerve IV damage.

Question 8

If you pinch the upper lip of the dog and/or the lateral canthus and there is no reaction, what nerve is likely damaged?

Answer 8

Maxillary branch of the trigeminal nerve

Question 9

If you notice a cat has medial strabismus, which nerve is likely damaged?

Answer 9

The abducens nerve because it provides motor innervation to the lateral rectus m.

Question 10

If you perform a corneal reflex test and notice that the third eyelid does not sweep across the surface of the cornea, what could be happening?

Answer 10

The abducens nerve is damaged and causing the retractor bulbi muscles do not contract in response to the stimulus.

Question 11

What does DVM stand for (other than Doctor of Veterinary Medicine)?

Answer 11

The muscles innervated by the oculomotor nerve. The dorsal, ventral ( and ventral oblique), and medial rectus mm.

Question 12

There is a lesion on the mandibular branch of the trigeminal nerve. What are some clinical signs you may see?

Answer 12

The animal may not be able to close the mouth and there may be poor tone in the masticatory muscles. Also, if you pinch the inferior labia and there is no reaction, there may be a problem ( V in, VII out)

Question 13

A dog can not open his jaw, what nerves may be affected?

Answer 13

The facial nerve ( CN VII ) and/or the mandibular branch CN V as the digastricus muscle is responsible for opening the jaw.

Question 14

What types of tests could you perform to see if CN VII was damaged?

Answer 14

Menace response (II in, VII out) 
Palpebral reflex ( V in, VII out)
Pinch upper/lower labii for a response

Question 15

The left side of a cat’s face is drooping, which nerves could be affected?

Answer 15

The left facial nerve

Question 16

What kind of test can you use to test the parasympathetic facial nerve innervation of an animal’s salivary and lacrimal glands?

Answer 16

It is not practical to test saliva production but a Schirmer Test for tear production ( this is not a definitive test that the facial nerve is affected).

Question 17

If a dog keeps turning and tilting it’s head to the right, which nerve may be affected?

Answer 17

The right vestibulocochlear nerve (CN VIII)

Question 18

If there is a lesion on the vestibulocochlear nerve, what could this affect in the dog?

Answer 18

The dog will not be able to hear and/or keep balance.

Question 19

Nystagmus

Answer 19

A fast paced twitch of the eyeball away from the source of a lesion most likely in CN VIII.

Question 20

A dog has no gag reflex when eating or drinking. Which nerves could have a lesion?

Answer 20

CN IX and CN X

Question 21

If the glossopharyngeal nerve has a lesion, what parts of the animal could be affected?

Answer 21

The animal may not be able to swallow (Dysphagia), there may be decreased/no gag reflex, taste or produce saliva. ( IX in , IX out)

Question 22

During a gag reflex, which nerves are afferent and which are efferent?

Answer 22

Afferent: CN IX and X
Efferent: CN V, VII, IX, X, XI, XII

Question 23

You obtain the heart rate of a cat and auscultate the abdomen. You notice that the heart rate is abnormally increased and there are very sparse gut sounds. Which nerve likely has a lesion?

Answer 23

Vagus nerve ( CN X)

Question 24

Which muscle is the only muscle responsible for opening up the glottis? Which nerve is it innervated by?

Answer 24

Cricoarytenoideus dorsalis, which is innervated by the caudal laryngeal nerve. The caudal laryngeal nerve is the terminal branch of the recurrent laryngeal nerve which is a branch of CN XI (accessory nerve).

Question 25

A dog is presented with stridor and it looks like there is laryngeal paralysis. Which nerve is likely causing the problem?

Answer 25

CN XI

Question 26

If there is a unilateral lesion on the left hypoglossal nerve, what can we expect to see?

Answer 26

The tongue will be set on the right side of the mouth and the tongue will be atrophied.