Lab Unit 03: Cranial Nerves

Question 1

Sternocleidomastoid (SCM) – (Moore 991)

Answer 1

• Origin (PA):
Mastoid process
+ lateral half of superior nuchal line.
• Insertion (DA):
- Sternal head: Anterior surface of manubrium of sternum.
- Clavicular head: Superior surface of medial third of clavicle.
• Nerve:
- CN XI Accessory nerve (motor)
- AR C2, C3 (pain and proprioception).
• Action:
- Bilaterally: Flexes the neck.
- Unilaterally: Ipsilateral lateral neck flexion and contralateral rotation.

Question 2

Upper Trapezius – (Moore 700)

Answer 2

• Origin (PA):
   Medial third of superior nuchal line
   \+ External occipital protuberance
   \+ Nuchal ligament
   \+ SP C7. 
• Insertion (DA):
   Lateral third of clavicle
   \+ Acromion.
• Nerve:
   - CN XI Accessory nerve (motor)
   - AR C3, C4 (pain and proprioception).
• Action:
   Elevates, adducts, and upwardly rotates scapula.

Question 3

Middle Trapezius – (Moore 700)

Answer 3

• Origin (PA): SP T1-5.
• Insertion (DA):
   Medial margin of acromion
   \+ superior lip of spine of scapula.
• Nerve:
   - CN XI Accessory nerve (motor)
   - AR C3, C4 (pain and proprioception).
• Action: Adducts the scapula.

Question 4

Lower Trapezius – (Moore 700)

Answer 4

• Origin (PA): SP T6-T12.
• Insertion (DA): Spine of scapula.
• Nerve:
- CN XI Accessory nerve (motor)
- AR C3, C4 (pain and proprioception).
• Action: Depresses, adducts, and upwardly rotates scapula.

Question 5

Cranial Nerves

Answer 5

• CN I Olfactory
• CN II Optic
• CN III Oculomotor
• CN IV Trochlear
• CN V Trigeminal
   - CN V1 Opthalmic division
   - CN V2 Maxillary division
   - CN V3 Mandibular division
• CN VI Abducens
• CN VII Facial
• CN VIII Vestibulocochlear
• CN IX Glossopharyngeal
• CN X Vagus
• CN XI Accessory
• CN XII Hypoglossal

Question 6

CN I Olfactory

Answer 6

• Special sensory visceral afferent
• Function: Smell
• Test:
- Unilateral test that must be performed bilaterally
- Block one nostril + place something pungent under the other nostril (coffee). Ask the patient when they smell it.

Question 7

CN II Optic

Answer 7

• Special Sensory
• Function:
- Visual acuity
- Intactness of visual fields
• Test: w/ an Snellen chart placed 6m away
- close one eye and read the smallest line they can make out
- 1 miss is fine; 3-4 move up one line

Question 8

CN III Olfactory

Answer 8

• Motor
• Function:
   - Pupil constriction
   - Upward / Downward / Medial gaze
   - Eyelid elevation
• Test:
   • Pupil constriction (direct & consensual)
      - Shine a light in patients eye. Look to see if the pupil of the eye the light is shone in constricts; also look if the contralateral pupil constricts.
   • Eyelid elevation
      - Look for symmetry of the eyelids
      - Ptosis (droopy eyelid)

Question 9

CN IV Trochlear

Answer 9

• Motor
• Inferior with lateral eye movement (“cute shoes”)
• Test:

Question 10

CN V Trigeminal

Answer 10

• Mixed
• Function:
   • Sensory:
     - face, cornea, nasal & oral cavity, upper & lower teeth
    - Ophthalmic, Maxillary, Mandibular division
   • Motor:
      - Muscles of Mastication
      - Mandibular division

• Test:
• Sensory component:
- Sensation to face (hot/cold, sharp/dull)
- Corneal reflex:touch cornea w/ a paper towel
–> blinking
• Motor component:
- Palpate masseter muscles

Question 11

CN VI Abducens

Answer 11

• Motor
• Function: Pure lateral eye movement
• Test: III, IV, VI tested together
- Smooth pursuits:
Check for smooth tracking (“follow my pen”)
- Saccades:
Accuracies (no jumping or overshooting; “look at my nose, look at my pen”)

Question 12

CN VII Facial

Answer 12

• Mixed
• Function:
   • Sensory: Taste to the anterior 2/3rds of tongue
   • Motor: Muscles of facial exression
• Test:
   • Sensory component:
      - Taste test: ID sweet or salty
   • Motor component:
      - Corneal reflex:touch cornea w/ a paper towel
        --> blinking
      - "Make faces"

Question 13

CN VIII Vestibulocochlear

Answer 13

• Sensory
• Function:
- Cochlear function: Hearing acuity
- Vestibular function: position in space related to position & movement of head and balance

• Test:
• Hearing tests:
- Rine Test (Air): tuning fork through air
- Weber Test (Bone): tuning fork on bony promnence: mastoid process, cranium

• Vestibular testing:

  - cold/warm stimulus
   - -> SHOULD cause vertigo/nystagmus
   - -> direction of nystagmus or eye beating
   - -> COWS: cold opposite, warm same

• Vestibulo-ocular reflex

  - Reflex test for III, VI & VIII
  - Eyes should stay on examiners nose while head thrust performed.
  - Conjugate horizontal gaze: coordinated eye movement

Question 14

CN IX Glossopharyngeal

Answer 14

• Mixed
• Function:
  
  • Sensory: touch & taste sensaton on posterior 1-3rd of tongue and pharyngeal wall (gag reflex)
  • Motor: swolloing, gag reflex

• Test:
• Sensory component:
- Taste test: Does it taste bitter?
- Gag reflex: lightly stimulate back of throat
• Motor component:
- Have patient swallowing a liquid

Question 15

CN X Vagus

Answer 15

• Mixed
• Function:
• Sensory: heart, lungs, trachea, pharynx, larynx, bronchi, GI tract, external ear
• Motor: heart, lungs, trachea, palate, pharynx, larynx, bronchi, GI tract
ex: constricts bronchioles, decreases HR, increases GI motility

• Test:
   • Say Ahhh - Test
      --> examine symmetry of uvula
      If lesion --> uvula deviates contralaterally
      (strong side is pulling)
      --> listen for hoarsness

• -> If both severed –> aphonia (unable to talk)
• -> if one severed –> deviates from affected side

Question 16

CN XI Accessory

Answer 16

• Motor
• Function:
   - Sternocleidomastoid (SCM)
   - Trapezius
• Test:
   • Shoulder shrug test: Trapezius
   • Head turn test: Sternocleidomastoid

Question 17

CN XII Hypoglossal

Answer 17

• Motor
• Function:
   - Tongue movement, symmetry & shape
• Test:
   • Let me see your tongue test:
      --> examine resting tongue
   • Stick out your tongue test:
      --> examine tongue movement, strength & coordination

–> if lesion –> tongue deviates ipsilaterally (strong side pushing)