Cranial Nerve Exam

Question 1

What would a lesion look like in CN I?

Answer 1

Loss of smell (decreased appetite, complete loss unlikely), more obvious in working/police dogs

Question 2

What would a lesion look like in CN II?

Answer 2

Blind (unilateral, bilateral)

Question 3

What would a lesion look like in CN III?

Answer 3

Strabismus - lateral deviation of the eye (because lateral rectus is still intact)
Ptosis - drooping of upper eyelid
No constriction of pupils (Myonasis)

Question 4

What would a lesion look like in CN IV?

Answer 4

Strabismus

Lateral rotation of dorsal aspect of pupil (because ventral oblique still has tone)

Question 5

What would a lesion look like in Ophthalmic br of CN V?

Answer 5

No corneal reflex (No sensation to the cornea)

No palpebral reflex (no sensation to upper eyelid and medial canthus)

Question 6

What would a lesion look like in Maxillary br of CN V?

Answer 6

No palpebral reflex (No sensation from lower eyelid and lateral canthus)
No response to pinch of upper lip

Question 7

What would a lesion look like in Mandibular br of CN V?

Answer 7

No response to pinch of lower lip

Not able to close the mouth/poor jaw tone –> atrophy of these muscles

Question 8

What would a lesion look like in CN VI?

Answer 8

Medial strabismus

Not able to retract the globe - no 3rd eyelid moving across

Question 9

What would a lesion look like in CN VII?

Answer 9

No palpebral reflex
No menace response
No response to pinching or upper/lower lip
Deviation of philtrum to normal side
Drooping of face/lack of facial expressions on affected side

Question 10

What would a lesion look like in CN VIII?

Answer 10

Head tilt/turn
No hearing
Circling, leaning, ataxia
Nystagmus - fast AWAY from lesion

Question 11

What would a lesion look like in CN IX?

Answer 11

History of trouble eating/swallowing
Dysphagia (difficulty swallowing: cough, gag, choke)
Decreased/absent gag reflex

Question 12

What would a lesion look like in CN X?

Answer 12

Dyphagia
Decreased/absent gag reflex
Loss of PSNS –> Decreased HR, Decreased gut sounds

Question 13

What would a lesion look like in CN XI?

Answer 13

Possible gait changes and altered head/neck movement

Laryngeal paralysis - Roarers in equine (Stridor - inspiratory noise)

Question 14

What would a lesion look like in CN XII?

Answer 14

Difficulty eating/drinking
Tongue set off to UNAFFECTED side
Decreased tone tone (atrophy)
If bilateral, complete paralysis of tongue

Question 15

Tests for CN I?

Answer 15

Smelly treat without visualization (don’t use noxious substances)

Question 16

Tests for CN II?

Answer 16

Pupillary Light Reflex - Dilated (mydriatic) pupil becomes constricted (miotic) with light - Should be consenual (both R and L constrict at same time) CN II in, CN III out

Menace Response - response to threatening gesture - close eyes - CN II in and CN VII out

Visual placement reaction
Obstacle Course
Tracking an object

Question 17

Tests for CN III?

Answer 17

Look for normal eye position and movement when tracking an object (CN II in, III out)
Look for normal upper eyelid position
PLR - no constriction

Question 18

Tests for CN IV?

Answer 18

Look for abnormal rotation of pupil

Look for normal congruent eye movement

Question 19

Tests for Ophthalmic br of CN V?

Answer 19

Corneal Reflex (CN V in, CN VI out) - touch cornea
Palpebral Reflex (CN V in CN VII out) - touch medial canthus, dog should blink

Question 20

Tests for Maxillary br of CN V?

Answer 20

Palpebral Reflex (V in VII out) 
Pinch upper lip (V in VII out)

Question 21

Tests for Mandibular br of CN V?

Answer 21

Pinch lower lip

Look at jaw tone, ability to close mouth

Question 22

Tests for CN VI?

Answer 22

Look for normal eye movement and position 
Corneal Reflex (V in VI out) - eye should be pulled back and 3rd eyelid should sweep across when cornea is touched

Question 23

Tests for CN VII?

Answer 23

Look for facial symmetry
Could stimulate CN V and observe for efferent response via facial
Schirmer Tear Test - but not definitive (for PSNS function)
Can test taste, but rarely done

Question 24

Tests for CN VIII?

Answer 24

Test hearing and balance separately

Question 25

Tests for CN IX?

Answer 25

Give treat/water - watch for normal swallowing

Gag reflex

Question 26

Tests for CN X?

Answer 26

Gag reflex

Observations

Question 27

Tests for CN XI?

Answer 27

Gait change

Stridor?

Question 28

Tests for CN XII?

Answer 28

Observations about tongue

Difficulty eating/drinking