Vestibular System II

Question 1

Conjugate Gaze

Answer 1

eyes move in the same direction, in order to keep images oriented on the retina to prevent diplopia

Question 2

Saccade

Answer 2

conjugate, rapid, ballistic movement for foveation, reflexive or voluntary

Question 3

Foveation

Answer 3

saccade to focus new object on fovea

Question 4

Smooth Pursuit

Answer 4

conjugate, slower, to follow moving target, to hold image in fovea

Question 5

Vergence Movement

Answer 5

movement to adjust for objects distant (diverge) and near (converge)

Question 6

Conjugate movements are

Answer 6

SACCADE and SMOOTH PURSUIT (not vergence)

Question 7

PPRF is the center for

Answer 7

HORIZONTAL gaze

Question 8

MLF is the center for

Answer 8

VERTICAL gaze; contributes to horizontal gaze

Question 9

Vestibulo-ocular reflex (VOR) functions to

Answer 9

keep eyes fixed on an object while head is moving

Question 10

In VOR, the eyes and head move __________

Answer 10

opposite

Question 11

Eye movement in VOR is

Answer 11

slow and gradual

Question 12

VOR is a reflex that can be

Answer 12

consciously suppressed as to “lock eyes in head” such as watching a tennis match

Question 13

IN VOR, left scarpa’s ganglion activates

Answer 13

left vestibular nucleus

Question 14

IN VOR, left vestibular nucleus activates

Answer 14

right PPRF

Question 15

In VOR, the right PPRF activates

Answer 15

Right abducens nuclei and the left oculomotor nuclei

Question 16

The fibers that travel from the right PPRF to the left oculomotor are in

Answer 16

MLF tract

Question 17

In reflexive light stimulus, the eyes move _________

Answer 17

TOWARD the stimulus

Question 18

RIght visual field is transmitted to

Answer 18

the left optic tract

Question 19

The left optic tract has some fibers that project to

Answer 19

Left superior colliculus

Question 20

The left superior colliculus projects to the

Answer 20

right PPRF

Question 21

Nystagmus

Answer 21

involuntary eye movements; physiological or pathological

Question 22

optokinetic nystagmus or reflex

Answer 22

alternating slow and fast eye movements for object tracking while head is stationary, slow movement tracks object, fast movement returns eyes once they have reached edge of movement (pathway unknown)

Question 23

railroad nystagmus

Answer 23

classic example of optokinetic nystagus when focusing on a stationary object while passing in a moving train

Question 24

Frontal Eye Field stimulated by

Answer 24

object suddenly appearing in visual field

Question 25

Frontal Eye Field stimulation generates a

Answer 25

voluntary saccade

Question 26

stereopsis

Answer 26

fusion of a single visual image during changes in depth of field (Vergence)

Question 27

Convergence

Answer 27

object moving closer to viewer

Question 28

Divergence

Answer 28

object moving away from viewer

Question 29

Vergence is a type of __________ eye movement

Answer 29

disconjugate

Question 30

Nystagmus is always named for the

Answer 30

FAST component, which is in the same direction as the head movement

Question 31

Testing the unconscious patient using warm caloric test

Answer 31

warm water causes endolymph to flow toward ampulla, activating vestibular system on SAME side, VOR activates circuitry and causes eyes to deviate away followed by a saccade to the SAME side

Question 32

Testing the unconscious patient using cold caloric test

Answer 32

cold water causes endolymph to flow away from the ampulla, activating vestibular system on the OPPOSITE side, VOR activates circuitry and causes eyes to deviate toward followed by a saccade to the OPPOSITE side

Question 33

COWS for Caloric nystagmus test

Answer 33

C- cold, O- opposite, W- warm, S- same; tells you unconscious patient is not braindead

Question 34

Vertigo can result from

Answer 34

lesion anywhere in the vestibular pathway

Question 35

Most cases of vertigo are caused by

Answer 35

peripheral lesions, associated with inner ear (hair cells, endolymph, vestibular nerve)

Question 36

Dix-Hallpike positional testing

Answer 36

helps distinguish between peripheral vs central lesion

Question 37

Peripheral lesions cause vertigo AND

Answer 37

uni-directional HORIZONTAL nystagmus (lesion to peripheral structures)

Question 38

Central lesions cause vertigo AND

Answer 38

POSSIBLY nystagmus in any direction (lesion to nuclei and connections)

Question 39

Doll’s eye (oculocephalic) reflex

Answer 39

rotate comatose patient’s head horizontally, activate VOR reflex and cause eyes to deviate slowly in opposite direction (+); if brain-dead (-) and eyes do not move

Question 40

Lesion to Left abducens nerve

Answer 40

paralysis of ipsilateral lateral rectus muscle; affected eye adducted at rest (medial strabismus), inability to abduct on lateral gaze to that side causing diplopia

Question 41

Lesion to ascending MLF - INTERNUCLEAR OPTHALMOPLEGIA

Answer 41

Inability to adduct eye with IPSILATERAL medial rectus, CONTRALATERAL eye will have nystagmus (lateral strabismus) and eye can no longer couple the eye movements

Question 42

Lesion to abducens nucleus

Answer 42

lies close to ipsilateral PPRF so, IPSILATERAL eye cannot abduct or adduct (PPRF and MLF effected) and opposite eye cannot look toward lesion (adduct)

Question 43

Meniere’s disease

Answer 43

caused by excess endolymph causing overstimulation of hair cells on that side; that causes tinnitus, vertigo, hearing loss

Question 44

Treatment for Meniere’s disease

Answer 44

aminoglycoside therapy, kills hair cell, reduce hair cell stimulation (can result in deafness)

Question 45

one and a half syndrome symptoms

Answer 45

Ipsilateral side cannot aBduct or aDduct, CONTRALATERAL eye cannot aDduct

Question 46

one and a half syndrome cause

Answer 46

abducens nuclei lesion affecting the PPRF and MLF due to Pontine infarcts (Unilateral PPRF lesion causing contralateral impairment to MLF)