Cranial nerves

Question 1

CN I

Answer 1

1. Olfactory = smell

a. damage – anosomia (inability to detect smells, seen with frontal lobe lesions)

Question 2

CN II

Answer 2

2. Optic = vision
   a. damage can cause homonymous hemianopsia (hemianopic visual field loss on the same side of both eyes)
   b. Hemianopias occur because the right half of the brain has visual pathways for the left hemifield of both eyes, and the left half of the brain has visual pathways for the right hemifield of both eyes

Question 3

CN III

Answer 3

3. Occulomotor = pupillary reflexes
   a. motor: medial rectus, superior and inferior rectus, and inferior oblique
   b. damage can cause absence of pupillary constriction or Horner’s syndrome (combination of drooping of the eyelid (ptosis) and constriction of the pupil (miosis), sometimes accompanied by decreased sweating of the face on the same side; redness of the conjunctiva of the eye is often also present)

Question 4

CN IV

Answer 4

4. Trochlear

a. turns adducted eye downwards – superior oblique

Question 5

CN V

Answer 5

5. Trigeminal
   a. V1 sensory on face
   b. V2 opthalmic branch (touch with cotton) = opthalamic division
   c. V3 motor mm of mastication = maxillary/mandibular division

Question 6

CN VI

Answer 6

6. Abducens

a. turns eye out = lateral rectus mm

Question 7

CN VII

Answer 7

7. Facial = facial expression
   a. parasympathetic control of lacrimal, submandibular, and sublingual glands, taste to anterior 2/3 of tongue, innervates ant aspect of tongue
   b. damage causes inability to close eye, droopy corner of mouth, difficulty speaking
   i. LMN lesion = ipsilateral side of face
   ii. UMN lesion = contralateral lower half of face

Question 8

CN VIII

Answer 8

8. Vestibular
   a. balance, gaze stability, auditory
   b. damage can cause vertigo, nystagmus, deafness

Question 9

CN IX

Answer 9

9. Glossopharyngeal
   a. phonation (voice quality), swallowing, innervates the back of the tongue
   b. damage causes dysphonia (hoarse or nasal voice)

Question 10

CN X

Answer 10

10. Vagus
    a. elevates the soft palate
    b. controls position of uvula, gag reflex
    c. muscles in larynx and upper esophagus

Question 11

CN XI

Answer 11

11. Accessory
    a. (spinal) - innervates traps and SCM
    b. damage can cause inability to shrug ipsilateral shoulder (traps) or inability to turn head to opp side (SCM)

Question 12

CN XII

Answer 12

12. Hypoglossal = tongue movement

a. damage = dysarthria or deviation of tongue to the weak side