Examination of Cranial Nerves

Question 1

Where is this examination important if we can simply do an MRI instead?

Answer 1

Clinical exam guides which bit to scan, and when comparing the patients functional status to the MRI then you can decide if the MRI lesion is important. You can also decide which lesion is responsible for the problem.

Question 2

What may you discover on introducing yourself to the patient?

Answer 2

A dysphasia or dysphonia or a decreased conscious level

Question 3

What may you discover on inspection? (5)

Answer 3

Facial palsy
Ptosis
Ophthalmoplegia 
Craniotomy scars
PEG/trachy

Question 4

What is CN IV?

Answer 4

Trochlear

Question 5

What is CN XII?

Answer 5

Hypoglossal

Question 6

What is CN VII?

Answer 6

Facial

Question 7

What is CN IX?

Answer 7

Glossopharyngeal

Question 8

How do you test the olfactory nerve (CN I)?

Answer 8

“Have you noticed any change in your senses of taste or smell?”

Question 9

How do you test the optic nerve? What must you remember to do?

Answer 9

Acuity using a Snellen chart or any printed material at the bed side
Test each eye separately!

Question 10

How do you test the optic nerve if acuity fails?

Answer 10

Finger counting & light discrimination

Question 11

How do you test the visual fields?

Answer 11

Confrontation – compare the patients fields to your own in quadrants, one eye at a time.

Question 12

If there is a lesion at the level of the optic nerve, what is the resulting deficit?

Answer 12

Monocular blindless

Question 13

If there is a lesion at the level of the optic chiasm, what is the resulting deficit?

Answer 13

Bitemporal hemianopia

Question 14

If there is a lesion at the level of the optic tract, what is the resulting deficit?

Answer 14

Contralateral homonymous hemianopia

Question 15

What 6 reflexes do you need to test in the eyes?

Answer 15

Direct
Consensual
Accomodation (all in both eyes)

Question 16

What causes miosis (small pupils)?

Answer 16

Drugs eg Opiates
Horner’s syndrome
Old age

Question 17

What causes mydriasis (dilated pupils)?

Answer 17

Drugs eg Atropine
Oculomotor palsy
Ocular trauma (irregular)

Question 18

How many muscles are there that move the eye? Name them and the movement they do.

Answer 18

6 – superior oblique (incycloduction), superior rectus (elevation, adduction), lateral rectus (abduction), medial rectus (adduction), inferior rectus (depression, adduction), inferior oblique (excycloduction)

Question 19

With the eye abducted, the ______ and ______ move the eye up and down.
With the eye adducted, the _____ and ______ move the eye up and down.

Answer 19

Superior and inferior recti

Superior and inferior obliques

Question 20

Oculomotor palsy results in…?

Answer 20

A dilated pupil and a depressed, abducted eye.

Question 21

Which muscle does CN IV innervate?

Answer 21

Trochlear innervates superior oblique

Question 22

Which muscle does CN VI innervate?

Answer 22

Abducens innervates lateral rectus

Question 23

How do you assess the trigeminal nerve?

Answer 23

Examine facial sensation to fine touch in all 6 areas (V1, 2, 3 on both sides)
Examine muscles of mastication - “clench your teeth” and “open your mouth”
Examine jaw jerk reflex

Question 24

How do you assess the facial nerve?

Answer 24

“Raise your eyebrows”
“Screw your eyes tight shut”
“Puff out your cheeks”
“Big smile

Question 25

Which spares the forehead - a UMN or LMH lesion? Why?

Answer 25

UMN because the forehead area of the facial nucleus is innervated by both motor cortices.

Question 26

What does the corneal reflex test?

Answer 26

V (ophthalmic devision) & VII - part of brain stem tests

Question 27

How do you test CN VIII?

Answer 27

Mask one ear with tragal massage and whisper a number into the tested ear, then ask the patient to repeat the number.

Question 28

Weber and Rinne uses a tuning fork with how many Hz?

Answer 28

512Hz

Question 29

Weber test asks which question?

Answer 29

In which ear is the sound louder?

Question 30

Rinne test asks which question?

Answer 30

Which is louder - air or bone conduction?

Question 31

In a right conductive deafness, which side does Weber localise to? Is the stimulus louder in air or bone?

Answer 31

Localises to right side

Bone stimulus is louder

Question 32

In a right sensorineural deafness, which side does Weber localise to? Is the stimulus louder in air or bone?

Answer 32

Localises to left side

Air stimulus is louder

Question 33

How do you test CN IX, X and XI?

Answer 33

Open mouth, say “ah” - uvula will elevate
It deviates away from a bulbar palsy.
Also test the gag reflex.

Question 34

How do you test CN XI and XII?

Answer 34

“Shrug you shoulders” (tests trapezius)
“Stick out your tongue”
Look for fasciculation and wasting
Deviates towards side of palsy