Cranial Nerves

Question 1

CN I (1)
Sensory or Motor

Answer 1

Olfactory Nerve
- Mediates the sense of smell
- Observed when the sniffs environment
Sensory

Question 2

CN II (2)
Sensory or Motor

Answer 2

Optic Nerve
- Carries visual signals from retina to occipital lobe of brain, observed as the pet tracks an object with its eyes. It also causes pupil constriction.
- The Menace response is the waving of the hand at the dog’s eye to see if it blinks (this nerve provides the vision; the blink is due to cranial nerve VII)
Sensory

Question 3

CN III (3)
Sensory or Motor

Answer 3

Oculomotor Nerve
- Provides motor to most of the extraocular muscles (dorsal, ventral, and medial rectus) and for pupil
constriction
- Observing pupillary constriction in PLR
Motor

Question 4

CN IV (4)
Sensory or Motor

Answer 4

Trochlear Nerve
- Provides motor function to the dorsal oblique extraocular muscle and rolls globe medially
Motor

Question 5

CN VI (5)

Answer 5

Trigeminal Nerve – Maxillary, Mandibular, and Ophthalmic Branches
- Provides motor to muscles of mastication (chewing muscles) and sensory to eyelids, cornea,
tongue, nasal mucosa and mouth
Both (sensory + motor)

Question 6

CN VII (6)
Sensory or Motor

Answer 6

Abducens Nerve
- Provides motor function to the lateral rectus extraocular muscle and retractor bulbi
- Responsible for physiologic nystagmus when turning head (also involves III, IV, and VIII)
- Examined by touching the globe and observing for retraction (also tests V for sensory)
Motor

Question 7

CN VII (7)
Sensory or Motor

Answer 7

Facial Nerve
- Provides motor to muscles of facial expression (eyelids, ears, lips) & sensory to medial pinna (ear flap). Also taste to rostral tongue
- Palpebral response –motor for the blink reflex when touching medial canthus (also tests V for sensory)
- Observe for facial paralysis, deviation of nose to one side, or droopy lips
- Schirmer tear test (this nerve also helps with tear production)
Both (Sensory + motor)

Question 8

CN VIII (8)
Sensory + Motor

Answer 8

Vestibulocochlear Nerve
- Sensory for hearing and head position
- A head tilt or nystagmus may suggest dysfunction of this nerve (vestibular disease or inner ear disease)
Sensory

Question 9

CN IX (9)
Sensory or Motor

Answer 9

Glossopharyngeal Nerve
- Innervates the pharynx for swallowing (with X).Also innervates some salivary glands and provides
taste innervation from caudal tongue
- Examine by eliciting a gag reflex and observing for dysphagia (difficulty swallowing).
Both (sensory + motor)

Question 10

CN X (10)
Senory or Motor

Answer 10

Vagus Nerve
- Innervates the larynx, esophagus, and pharynx. Also provides parasympathetic innervation to the heart
and viscera
- Tested with a gag reflex (along with CN IX)
Both (sensory + motor)

Question 11

CN XI (11)
Sensory or Motor

Answer 11

Spinal Accessory Nerve
- Innervates cranial cervical (neck) muscles
Motor

Question 12

CN XII (12)
Senory or Motor

Answer 12

Hypoglossal Nerve
- Motor to the tongue (causes tongue movement)