Cranial nerves

Question 1

Acronym to recall CNs

Answer 1

Oh Oh Oh To Touch And Feel Virgin Girls Vagina And Hymen

Question 2

Acronym to recall innervation of CNs

Answer 2

Some Say Marry Money But My Brother Says Big Brains Matter More

Question 3

What is CN1?
How to test it?

Answer 3

Olfactory
Sensory
- Any change to sense of smell?

Question 4

What is CN2?
How to test it?

Answer 4

Optic
Sensory
- Pupil reflex –> shine light in eye both sides, pupil should constrict
- Pupil accommodation –> watch finger, should constrict pupils and eyes should converge
- Visual acuity –> read snellen chart covering 1 eye, test both sides
- Visual fields –> detect finger movement in 4 quadrants, cover 1 eye open side test finger wiggling high and low test both sides
- Fundoscopy –> use fundoscope to visualise retina in both eyes

Question 5

What is CN3 4 and 6?
How to test them?

Answer 5

CN3 oculomotor - eyelid opening
CN4 trochlear - eye movement
CN6 abducens - lateral eye movement
Motor

• Draw big H in the air in front of pt, check for double vision, do eyes move synchronously?

Question 6

What is CN5?
How to test it?

Answer 6

Trigeminal
Both sensory and motor
3 divisions - ophthalmic, maxillary, mandibular

Sensory test
- Cotton wool then sharp object with pt eyes closed in all 3 areas both sides of face, can pt feel, is sensation same both sides?

Motor test
- Pt clench, palpate temporalis and masseter, check equal muscle bulk
- Pterygoid - pt keep mouth open against resistance to close under chin - pt move jaw side to side are movements equal
- Corneal reflex - cotton wool on eye - blinking expected
- Jaw jerk reflex - slightly open mouth finger on chin, tap with tendon hammer, slight close expected

Question 7

What is CN7?
How to test it?

Answer 7

Facial
Both sensory and motor
Muscles of facial expression
- Check pt can: raise eyebrows, squeeze eyes shut, show teeth, blow out cheeks

Question 8

What is CN8?
How to test it?

Answer 8

Vestibulocochlear
Sensory

Hearing
- Does pt have hearing difficulties?
- Whisper number in ear, ask pt to repeat, if problem continue with 2 further tests
- Rinne’s - tuning fork in front of ear then behind, which is louder (behind = hear by bone conduction, front = hear by air conduction)
- Weber’s - tuning fork centre forehead, louder RHS LHS or same - should be equal

Question 9

What is CN9, 10?
How to test them?

Answer 9

CN9 Glossopharyngeal - posterior 1/3rd tongue
CN10 Vagus - pharynx and larynx
Both sensory and motor

• Ask pt to cough
• Say ahhh - check palate rises equally both sides, uvula central
• Gag reflex - touch soft palate with wooden spatula

Question 10

What is CN11?
How to test it?

Answer 10

Accessory
Motor

• Ask pt to shrug shoulders and keep raised, try to force down, strength of trapezius
• Turn face left and ask to come central against resistance, repeat RHS, strength should be equal

Question 11

What is CN12?
How to test it?

Answer 11

Hypoglossal
Motor

Tongue movement
- Stick tongue out, check for twitching
- Tongue right then left
- Tongue in each cheek, push against tongue, movement and power should be equal both sides

Question 12

What is Bell’s Palsy, how would it present, which CN affected and how would you manage it?

Answer 12

• Sudden paralysis of facial muscles
• Unable to close eyelid
• Weakened muscles of facial expression - CN7
• Inform pt, can worsen over period of 5 days
• Give eye patch to protect
• Follow up after 1 week, should return to normal