FE: Lecture 2: Eye Movement Cranial Nerves

Question 1

How does the eye compensate for the fovea being so small?

Answer 1

eye is constantly moving so the fovea can see whole image, movements must be fast

Question 2

What does the term conjugate mean?

Answer 2

each eye gazes at the same point

Question 3

What is diplopia?

Answer 3

double vision or two eyes looking at different things

this is a MOTOR problem not a sensory

Question 4

What are two loss of reflexes that can occur in the eye?

Answer 4

Doll’s eye reflex- looks right eyes goes left

optokinetic nystagmus

Question 5

What is the weirdness of the trochlear nerve?

Answer 5

exits dorsal side of brainstem (tectum)

crosses midline before exiting therefore:

1. left nucleus damage- right eye paralysis
2. left nerve damage after crossing- left eye paralysis

Question 6

What are the different types of eye movements?

Answer 6

ADD, ABD, Elevation, depression, torsion, vergence, divergence and conjugate

Question 7

How do you differentiate direction of torsion?

Answer 7

1. top of eye towards nose- medial rotation, intorsion
2. away from nose- external rotation, extorsion

these happen during side bend of the head

Question 8

What does a conjugate eye movement mean?

Answer 8

when looking to left ——right eye- ADD, left eye ABD

Question 9

What is convergence?

Answer 9

both eyes ADD

Question 10

What is divergence?

Answer 10

both eyes ABD

Question 11

What muscles control eye movements?

Answer 11

superior, inferior, medial, lateral rectus

superior and inferior oblique

Question 12

What two muscles ABD and ADD eyes?

Answer 12

medial and lateral rectus

Question 13

When the eye is ABDucted what are actions of the muscles?

Answer 13

SR- elevates
IR- depresses
obliques rotate- medially

Question 14

When the eye is ADDucted what are the actions of the muscles?

Answer 14

Recti rotate
IO- elevates
SO- depresses

Question 15

What muscles work to contract to the right?

Answer 15

left medial rectus, right lateral rectus

Question 16

What is the meaning of the mnemonic LR6SO4

Answer 16

lateral rectus is innervated by abducens nerve 6

superior oblique is innervated by trochlear nerve 4

all the rest are oculomotor

Question 17

What is it called when you have damage to abducens nucleus or nerve?

Answer 17

abducens palsy

pt has damage to both CN6 which leads to lateral rectus paralysis

they also have diplopia due to weak ABD

Question 18

What is oculomotor palsy?

Answer 18

ipsilateral paralysis of all other muscles

weak add- medial rectus paralysis (ABD at rest)

weak elevation and depressing when ABD- SR/ IR

Question 19

What other functions are damaged during oculomotor palsy?

Answer 19

drooping eyelids- ptosis b/c CN 3 opens eyelids (levator palpebrae)

also a dilated pupil- loss of parasympathetic innervation

Question 20

What is trochlear palsy?

Answer 20

normal ipsilateral paralysis of superior oblique

weak depression of eye when ADDucted

torsional diplopia when looking forward

Question 21

What is right side trochlear nerve palsy torsional compensation?

Answer 21

when your eyes are forward the eyes laterally rotate and slight elevate (hypertropia)

as a compensation the pt will tuck chin and tilt head to get rid of diplopia

Question 22

Where are the cortical UMN’s for nerves 3, 4 and 6?

Answer 22

cortical area 8/ Brodmann’s 8

route- 1. middle frontal gyrus to PPRF then to pons for nuclei of 3, 4 and 6

this activation produces conjugate eye movements

Question 23

What would happen if you had a lesion in B8?

Answer 23

no paralysis, temporary effects

hard to maintain contralateral eccentric eye position

Question 24

What pathway do all eye movements go through?

Answer 24

medial longitudinal fasiculus