B7.035 Prework 1: Eye Movement

Question 1

innervation of extraocular eye muscles

Answer 1

CN III, IV, VI

oculomotor, trochlear, abducens

Question 2

orientation of CN III, IV, and VI nuclei in brainstem

Answer 2

oculomotor nucleus most rostral in midbrain, also the longest
trochlear nucleus below oculomotor
abducens below trochlear in pons

Question 3

abduction

Answer 3

toward ear

Question 4

adduction

Answer 4

toward nose

Question 5

intorsion

Answer 5

rotates eye inward / downward toward nose

Question 6

extorsion

Answer 6

rotates eye upward / outward toward ear

Question 7

function of the H test

Answer 7

examine muscle action in the position where it exerts it’s greatest effect

Question 8

muscles involved in elevation / depression when eye is abducted

Answer 8

superior rectus

inferior rectus

Question 9

muscles involved in elevation / depression when eye is adducted

Answer 9

superior oblique

inferior oblique

Question 10

symptoms of abducens ophthalmoplegia

Answer 10

paralysis of LR muscle (abduction)
affected eye deviates medially at rest
affected eye doesn’t move laterally during lateral gaze
diplopia

Question 11

which muscles control intorsion

Answer 11

superior muscles

• superior oblique
• superior rectus

Question 12

which muscles control extorsion

Answer 12

inferior muscles

• inferior oblique
• inferior rectus

Question 13

symptoms of trochlear ophthalmoplegia

Answer 13

excess extorsion
difficulty with depression in H test
patient tils head away from affected eye to realign visual axes
affected eye is hypertrophic (elevates above horizontal)
patient tucks chin down

Question 14

innervation of the superior oblique

Answer 14

motor axons exit from the DORSAL surface of the midbrain

nucleus is contralateral to innervated eye, but nerve travels ipsilateral to the eye (decussates extremely early)

Question 15

symptoms of oculomotor ophthalmoplegia

Answer 15

abduction of the affected eye
ptosis (paralysis of levator palpebrae)
mydriasis, pupillary dilation (disruption of parasympathetics)

Question 16

where is UMN control for eye movement

Answer 16

frontal eye fields control oculomotor, trochlear and abducens motor neurons via PPRF
allows for conjugate eye movement

Question 17

function of horizontal gaze center

Answer 17

mediates voluntary lateral gaze

Question 18

describe the horizontal gaze center

Answer 18

frontal eye field stimulates neuron in abducens nucleus to act on contralateral lateral rectus
abducens nucleus connects to contralateral oculomotor nucleus via medial longitudinal fasciculus (MLF)
oculomotor nucleus controls medial rectus in other eye so that both eyes gaze together

Question 19

where is the horizontal gaze center

Answer 19

reticular formation of pons

PPRF (paramedian pontine reticular formation)

Question 20

what is internuclear ophthalmoplegia

Answer 20

lesion of the MLF rostral to the abducens nucleus
failure of eye ipsilateral to MLF lesion to adduct
affected eye doesn’t follow unaffected eye

Question 21

symptoms of internuclear ophthalmoplegia

Answer 21

attempted gaze to the right
failure of left eye to adduct during H test
nystagmus in right eye

Question 22

what is nystagmus

Answer 22

jerky movements of unaffected eye to match up with affected eye

Question 23

function of superior colliculus

Answer 23

orientation reflex saccades

Question 24

function of visual cortex

Answer 24

smooth pursuit

tacking objects

Question 25

function of vestibular nuclei

Answer 25

allows eyes to focus on one object while head is moving

Question 26

function of frontal eye fields + superior colliculus

Answer 26

voluntary saccades scanning back and forth without focus on one thing in particular jerky movement