FUNCTIONAL ANATOMY - Cranial Nerves

Question 1

What are the twelve cranial nerves?

Answer 1

I Olfactory nerve
II Optic nerve
III Oculomotor nerve
IV Trochlear nerve
V Trigeminal nerve
VI Abducens nerve
VII Facial nerve
VIII Vestibulocochlear nerve
IX Glossopharyngeal nerve
X Vagus nerve
XI Accessory nerve
XII Hypoglossal nerve

Question 2

What is the function of cranial nerve I (olfactory nerve)?

Answer 2

Olfaction

Question 3

What are three clinical signs of cranial nerve I (olfactory nerve) dysfunction?

Answer 3

Hyposmia (partial loss of smell)
Anosmia (complete loss of smell)
Inappetence

Question 4

What can be done to test the function of cranial nerve I (olfactory nerve)?

Answer 4

Test the animal’s response to aromatic substances while they are blindfolded

Question 5

What is the function of cranial nerve II (optic nerve)?

Answer 5

Vision

Question 6

What are the functions of cranial nerve III (oculomotor nerve)?

Answer 6

Motor innervation of the ipsilateral dorsal rectus, medial rectus, ventral rectus and ventral oblique extraocular muscles and parasympathetic innervation of the iris (for miosis)

Question 7

What are two clinical signs of cranial nerve III (oculomotor nerve) dysfunction?

Answer 7

Ventrolateral strabismus of the ipsilateral eye
Absent pupillary light reflex (mydriasis)

Question 8

What can be done to test the function of cranial nerve III (oculomotor nerve)?

Answer 8

Observe the eye position
Test pupillary light reflex (PLR)

Question 9

What is the function of cranial nerve IV (trochlear nerve)?

Answer 9

Motor innervation of the contralateral dorsal oblique extraocular muscle

Question 10

What is the clinical sign of cranial nerve IV (trochlear nerve) dysfunction?

Answer 10

Dorsolateral strabismus of contralateral eye

Question 11

What can be done to test the function of cranial nerve IV (trochlear nerve)?

Answer 11

Observe the position of the eye

Question 12

What are the three branches of the trigeminal nerve?

Answer 12

Ophthalmic branch
Maxillary branch
Mandibular branch

Question 13

What are the functions of cranial nerve V (trigeminal nerve)?

Answer 13

Sensory innervation of the face
Motor innervation of the masticatory muscles

Question 14

What are the two clinical signs of cranial nerve V (trigeminal nerve) dysfunction?

Answer 14

Absent facial sensation
Masticatory muscle atrophy

Question 15

What can be done to test the function of cranial nerve V (trigeminal nerve)?

Answer 15

Observe and palpate the masticatory muscles for atrophy
Corneal reflex
Palpebral reflex

Question 16

What is the function of cranial nerve VI (abducens nerve)?

Answer 16

Motor innervation of the ipsilater lateral rectus and retractor bulbi extraocular muscles

Question 17

What are the three clinical signs of cranial nerve VI (abducens nerve) dysfunction?

Answer 17

Medial strabismus of the ipsilateral eye
Inability to retract the eyeball
Absent vestibulo-ocular reflex

Inability to retract eyeball = absent corneal reflex

Question 18

What can be done to test the function of cranial nerve VI (abducens nerve)?

Answer 18

Observe the position of the eye
Corneal reflex
Test vestibulo-ocular reflex

Question 19

What are the functions of cranial nerve VII (facial nerve)?

Answer 19

Sensory innervation to the tongue and ear pinna
Motor innervation of the facial muscles
Parasympathetic innervation of the nasal glands, lacrimal glands and mandibular and sublingual salivary glands

Question 20

What are the three clinical signs of acute cranial nerve VII (facial nerve) dysfunction?

Answer 20

Ipsilateral ear and lip drooping
Absence of blinking
Keratoconjunctivitis sicca

Question 21

What is Keratoconjunctivitis sicca?

Answer 21

‘Dry eye’

Question 22

What is the clinical sign of chronic cranial nerve VII (facial nerve) dysfunction?

Answer 22

Retracted lip

Question 23

What can be done to test the function of cranial nerve VII (facial nerve)?

Answer 23

Palpebral reflex
Menace response
Lip pinch
Schirmers tear test

Question 24

What are the two branches of cranial nerve VIII (vestibulocochlear nerve)?

Answer 24

Cochlear branch
Vestibular branch

Question 25

What are the functions of cranial nerve VIII (vestibulocochlear nerve)?

Answer 25

Hearing Balance

Question 26

What are the two clinical signs of cranial nerve VIII (vestibulocochlear nerve) dysfunction?

Answer 26

Deafness Vestibular symptoms

Question 27

What can be done to test the function of cranial nerve VIII (vestibulocochlear nerve)?

Answer 27

Observe for any vestibular symptoms Test the vestibulo-ocular reflex Brain auditory evoked response (BAER) test for hearing

Question 28

What are the functions of cranial nerve IX (glossopharyngeal nerve)?

Answer 28

Sensory innervation of the tongue and pharynx (taste) Motor innervation to the stylopharyngeus muscle Parasympathetic innervation of the parotid and zygomatic salivary glands

Question 29

What are the functions of cranial nerve X (vagus nerve)?

Answer 29

Sensory innervation of the pharynx (sensation and taste) Motor innervation of the pharynx, larynx and oesophagus Parasympathetic innervation of the cervical, thoracic and abdominal viscera

Question 30

What are the five clinical signs of cranial nerve IX (glossopharyngeal nerve) and cranial nerve X (vagus nerve) dysfunction?

Answer 30

Dysphagia Absent gag reflex Inspiratory dyspnoea Dysphonia Megaoesophagus

Question 31

What can be done to test the functions of cranial nerve IX (glossopharyngeal nerve) and cranial nerve X (vagus nerve)?

Answer 31

Test the gag reflex

Question 32

What is the function of cranial nerve XI (accessory nerve)?

Answer 32

Motor innervation of the neck muscles (trapezius, brachiocephalic and sternocephalic muscles)

Question 33

What is the clinical sign of cranial nerve XI (accessory nerve) dysfunction?

Answer 33

Deviation of the neck

Question 34

What is the function of cranial nerve XII (hypoglossal nerve)?

Answer 34

Motor innervation of the tongue

Question 35

What are the three clinical sign of cranial nerve XII (hypoglossal nerve) dysfunction?

Answer 35

Tongue atrophy Tongue deviation Abnormal deglutition (swallowing)

Question 36

What can be done to test the function of cranial nerve XII (hypoglassal nerve)?

Answer 36

Observe for tongue position and atrophy