Cranial Nerve Exam

Question 1

What is anosmia?

Answer 1

loss of the sense of smell

Question 2

What are some causes of anosmia?

Answer 2

Parkinson’s, lesions in CN I, tumor at the base of the skull

Question 3

What three things do you want to check for regarding sight?

Answer 3

can someone see distance, up close, and color

Ask the patient if they wear glasses and what for

Question 4

How far should a Snellen chart be held from the patient?

Answer 4

20 ft. Do it for each eye in glass, and for corrected and uncorrected setting

Question 5

How do you test near vision?

Answer 5

Jaegar plates

Question 6

How do you test color vision?

Answer 6

Ishihara plates. Test plate is usually 12. sets are typically 13 or 17 plates

Question 7

What is an optic eye test?

Answer 7

This is referred to as visual field testing by confrontation. You are comparing your visual field (which you assume is normal) with the patient’s. You each maintain focus on the other’s pupil, cover or close opposite eyes (e.g., patient’s right and your left) and compare when you each first see your finger move into the field of vision. This should be simultaneously. Be sure you keep your fingers in a plane half way between you and the patient

Question 8

Are central visual field tests typically done for all patients?

Answer 8

No. Central visual field testing is usually done only in specialty practice (e.g., ophthalmology and neurology). In such cases, this may be done more precisely using a large device called a Goldmann perimeter.

Question 9

Where are the nuclei of CN 3 and 4 located?

Answer 9

in the midbrain

Question 10

Where is the nuclei of CN 5 located?

Answer 10

runs through the brainstem

Question 11

Where are the nuclei of CN 6 and 7 located?

Answer 11

pans

Question 12

Where are the other nuclei of CNs located?

Answer 12

the medulla (bulbar nuclei)

Question 13

What is a cover test?

Answer 13

ask patient to focus on a near object

cover, then uncover one eye

observe if there is adjustment in alignment or readjustment of the eyes in response

normally done in children to diagnose strabismus (squint)

Question 14

How is a pursuit eye movement test performed?

Answer 14

ask patient to follow the motion of an object while keeping their head still. First move to the left and look for nystagmus.

Ask the patient if they have diplopia

Question 15

What is diplopia?

Answer 15

double vision

Question 16

If the patient says he/she does not have diplopia during a left movement pursuit test, what does that tell you?

Answer 16

the left lateral rectus (innervated by CN VI, nucleus in the pans) is intact, as is the right medial rectus (CN III, nucleus in the midbrain)

continue the test for the right side, and if everything is normal you know that the the right lateral rectus (innervated by CN VI, nucleus in the pans) is intact, as is the left medial rectus (CN III, nucleus in the midbrain)

Question 17

What does the upward motion of the pursuit eye test, test?

Answer 17

the superior recti of both eyes (CN III, nuclei in the midbrain)

Question 18

How do you perform the downward motion of the pursuit eye movement test?

Answer 18

ask the patient to follow the downward movement. In order to do this, you will have to hold the eyelids open. You are testing the inferior recti of both eyes (CN III, nuclei in the midbrain)

Question 19

How do you test the superior oblique m.? What is it innervated by?

Answer 19

Start with the object and go down to the corners (like a triangle on both sides)

innervated by CN IV, nucleus in midbrain

Question 20

How do you test the inferior oblique m.? What is it innervated by?

Answer 20

Start with the object and go UP to the corners (like an upside down triangle on both sides)

innervated by CN III, nucleus in midbrain

Question 21

The trigeminal nerve has what three components in terms of clinical testing?

Answer 21

motor, sensory, and reflexive

Question 22

The motor part of CN V supplies what?

Answer 22

the muscles of mastication

Question 23

How do you test the motor component of CN V?

Answer 23

ask the patient to grit their teeth. feel the muscle bulk of masseter, temporalis, and pterygoids

also ask the patient to open their mouth, first down then to each side, against the pressure of your hand

Question 24

How do you test the sensory component of CN V?

Answer 24

ask patient to close eyes and use soft touch to test the three sections of CN V

“Can you feel that?” “Does it feel the same on both sides?”

can follow with a pin prick for hard touch

Question 25

CN VII has motor, sensory, and reflexive components. How do you test the motor component of CN VII?

Answer 25

ask the patient to:

1) raise the eyebrows
2) frown down
3) squeeze the eyelids tight and you try to open one at a time with them resisting
4) show me your teeth
5) blow out checks

Question 26

How do you test the sensory component of CN VII?

Answer 26

taste to anterior 2/3 of tongue. “Have you noticed any changes in your sense of taste?”

Question 27

What is hyperacusis?

Answer 27

increased sensitivity to noise- can loose the dampening noise effect of the stapedius

Question 28

How do you test CN VIII?

Answer 28

Cover the triages of one hear and ask the patient to repeat numbers whispered in the other ear

rinne and weber’s tests can be performed if there is any doubt

Question 29

What do the Rinne and weber’s tests do?

Answer 29

help distinguish between air conduction and bone conduction

Question 30

Which is typically better, air or bone conduction?

Answer 30

air

Question 31

For a hearing test, what frequency tuning fork should be used?

Answer 31

512 Hz

Question 32

How do you perform a Rinne’s test?

Answer 32

strike the tuning fork gently. Hold the end of the fork to the mastoid process to test bone conduction until the patient cannot hear it anymore, then move the fork over the ear to test air conduction. The patient should still hear something over the ear after he/she cannot hear when the fork is over the mastoid process

Question 33

How do you perform a Weber’s test?

Answer 33

strike the tuning fork and place the end on the forehead and see if the sound localizes to either the right or left ear. “Is that any different in either ear?”

Question 34

What forms the afferent and efferent limbs of the gag reflex?

Answer 34

CN 9 and 10, respectively

Question 35

How do you test CN 9 and 10?

Answer 35

ask the patient to open their mouth and say ‘ah’. Observe if the uvula moves upward and the palatal folds move symmetrically

Question 36

How do you test the gag reflex?

Answer 36

touch the posterior wall of the pharynx using a fresh spatula

Question 37

How do you test the accessory nerve?

Answer 37

start by visually examining the SCM and trapezius for any signs of muscle wasting

trapezius -ask the patient to do a shoulder shrug and apply downward pressure and ask them to resist

SCM- ask the patient to turn their head to the left and use your hand to apply pressure to try to move the head back to the midline. This tests the RIGHT SCM. repeat with the left SCM

Question 38

How do you test CN XII?

Answer 38

the hypoglossal nerve supplies the tongue so ask the patient to open their mouth to observe the tongue at rest. Look for wasting .

Ask the patient to stick out their tongue and see if it deviates to the left or right. Tongue will deviate TO the side of the lesion

Question 39

How do you test the light reflex?

Answer 39

Shine a light in the eye

CN 2 is the afferent limb and CN 3 the efferent limb of the pupillary light reflex that brings parasympathetic nerves back to the eye to make the pupil smaller

Question 40

How do you test the accommodation reflex?

Answer 40

Two ways:
1) ask the patient to look at an object in the far field and switch to looking at your finger about 1 ft away

2) bring your finger from far to the near and ask the patient to go cross-eyed

The accommodation reflex occurs in response to focusing on a near object. As with the pupillary light reflex, CN 2 is the afferent limb. The efferent limb consists of preganglionic parasympathetic GVE fibers of CN 3 that synapse in the ciliary ganglion and ultimately innervate the sphincter pupillae muscle, responsible for pupillary constriction, and the ciliary muscles, responsible for accommodation of the lens for near vision.

Question 41

What could be the causes of a single small pupil?

Answer 41

syphillis, ophiods (drugs), and Horner syndrome

Question 42

What could be the causes of a single enlarged pupil?

Answer 42

drugs (cocaine), CN III palsy, or homozate pupil (?)