FE: Lecture 2: Eye Movement Cranial Nerves Flashcards Preview

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Flashcards in FE: Lecture 2: Eye Movement Cranial Nerves Deck (24):

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

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


What does the term conjugate mean?

each eye gazes at the same point


What is diplopia?

double vision or two eyes looking at different things

this is a MOTOR problem not a sensory


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

Doll's eye reflex- looks right eyes goes left

optokinetic nystagmus


What is the weirdness of the trochlear nerve?

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


What are the different types of eye movements?

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


How do you differentiate direction of torsion?

1. top of eye towards nose- medial rotation, intorsion

2. away from nose- external rotation, extorsion

these happen during side bend of the head


What does a conjugate eye movement mean?

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


What is convergence?

both eyes ADD


What is divergence?

both eyes ABD


What muscles control eye movements?

superior, inferior, medial, lateral rectus

superior and inferior oblique


What two muscles ABD and ADD eyes?

medial and lateral rectus


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

SR- elevates
IR- depresses
obliques rotate- medially


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

Recti rotate
IO- elevates
SO- depresses


What muscles work to contract to the right?

left medial rectus, right lateral rectus


What is the meaning of the mnemonic LR6SO4

lateral rectus is innervated by abducens nerve 6

superior oblique is innervated by trochlear nerve 4

all the rest are oculomotor


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

abducens palsy

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

they also have diplopia due to weak ABD


What is oculomotor palsy?

ipsilateral paralysis of all other muscles

weak add- medial rectus paralysis (ABD at rest)

weak elevation and depressing when ABD- SR/ IR


What other functions are damaged during oculomotor palsy?

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

also a dilated pupil- loss of parasympathetic innervation


What is trochlear palsy?

normal ipsilateral paralysis of superior oblique

weak depression of eye when ADDucted

torsional diplopia when looking forward


What is right side trochlear nerve palsy torsional compensation?

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


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

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


What would happen if you had a lesion in B8?

no paralysis, temporary effects

hard to maintain contralateral eccentric eye position


What pathway do all eye movements go through?

medial longitudinal fasiculus