Cranial Nerves

Question 1

Cranial Nerve II

Answer 1

Optic nerve - sensory

• carries visual signal from retina, to occipital lobe of brain
• examined by:
  
  • drop cotton ball (II only)
  • menace response (II visual, VII for blink)
  • pupillary light response (II visual, III pupil contraction)

Question 2

Cranial Nerve IV

Answer 2

Trochlear nerve - motor

• provides motor function to the dorsal oblique extra ocular muscle and rolls globe medially
• examine by observing for dorsolateral rotation of the pupil

Question 3

Cranial Nerve III

Answer 3

Oculomotor nerve - motor

• Efferent only
• Orbital fissure is its exit from skull
• Motor to some of the extraocular muscles
	○ Levator palpebrae (eyelid), dorsal rectus, medial rectus, ventral rectus, ventral oblique muscles
•  preganglionic parasympathetic fibers travel to the ciliary ganglion along this nerve
• Postgangionic parasympathetic fibers from this ganglion go to the constrictor pupillary muscle (CPM) and to the ciliary body of the eye

Question 4

Cranial Nerve V

Answer 4

Trigeminal nerve - both
Maxillary, Mandibular and Ophthalmic branches
- motor to muscles of mastication (masseter and temporal) and sensory to eyelids, cornea, tongue, nasal mucosa and mouth
- examine by:
- palpate muscles of mastication and check jaw tone
- touch nasal septum - look for retraction
- touch globe - look for retraction (also VI for motor)
- palpebral response (also VII for motor)
- pinch lip - observe for snarl response (also VII for motor)

Question 5

Cranial Nerve VI

Answer 5

Abducens nerve - motor
Orbital fissure

• provides motor function to the lateral rectus extra ocular muscle and retractor bulbi
• examine by:
  
  • touching globe and observing for retraction (also V sensory)
  • observe for medial strabismus
  • observe for physiologic nystagmus when turning head (also III, IV and VIII)

Question 6

Cranial Nerve VIII

Answer 6

Vestibulocochlear nerve - sensory

• sensory input for hearing and head position
• examine by:
  
  • hearing assessment, deaf animals may startle easily
  • observe for head tilt, abnormal nystagmus and presence of normal physiologic nystagmus

Question 7

Cranial Nerve VII

Answer 7

Facial nerve - both

• provides motor to muscles of facial expression (eyelids, ears, lips) and sensory to medial pinna, taste to rostral tongue and parasympathetic innervation to lacrimal glands (tear production) and some salivary glands
• examine by:
  
  • menace response (also II visual cue)
  • palpebral response (V for sensory)
  • observe for facial paralysis (deviation of nose or droopy lips)
  • Schirmer tear test
  • ear flick in response to stimulation of medial pinna

Question 8

Cranial Nerve IX

Answer 8

Glossopharyngeal nerve - both

• provides motor and sensory innervation to pharynx for swallowing (with X). Also innervates some salivary glands and provides taste innervation form caudal tongue
• examine by eliciting a gag reflex and observing for dysphagia

Question 9

Cranial Nerve X

Answer 9

Vagus nerve - both

• innervates the larynx, esophagus and pharynx
• also provides parasympathetic innervation to the heart and viscera
• examine by:
  
  • elicit a gag reflex
  • observe for laryngeal paralysis
  • assess for megaoesophagus and regurgitation

Question 10

Cranial Nerve XI

Answer 10

Spinal accessory nerve - motor

• innervates cranial cervical muscles
• rarely assessed and rarely a clinical problem

Question 11

Cranial Nerve XII

Answer 11

Hypoglossal nerve - motor only
Hypoglossal canal

• provides motor to the tongue (extrinsic and intrinsic)
• examine by observing tongue for movement and symmetry or for problems drinking and prehending food
• also a part of the gag reflex

Question 12

Cranial Nerve I

Answer 12

Olfactory - sensory

• mediates the sense of smell
• rarely has a primary neurologic problem
• examined by observing patient sniff around