8. Control of Eye Movements (Keim)

Question 1

Where are the burst cells, tonic cells, and pause cells located for horizontal saccadic movements?

Answer 1

Horizontal

Burst cells: Paramedian pontine reticular formation

Tonic cells: Nucleus prepositus hypoglossi

Pause cells: Omnipause cells of raphe nuclei

Question 2

What three locations are associated with upward gaze?

Tumor of what structure can damage these?

Answer 2

Superior colliculus

Posteiror commissure

Pretectal area

Pineal gland tumors can damage these and result in palsy of upward gaze. (difficulty looking up)

Question 3

What is the key clinical difference between the vergence pathway and the other pathways of eye adduction?

Answer 3

The vergence pathway doesn’t use the medial longitudinal fasciculus.

If a patient can cross their eyes on vergence, but cannot adduct otherwise, MLF is damaged.

Question 4

Which region of the brain performs volitional and reflexive saccades respectively?

Answer 4

Volitional saccades: Frontal eye field.

Reflexive saccades: Superior colliculus.

Question 5

Where is the damage in intranuclear opthalmoplegia?

what are the sx?

Answer 5

In the ipsilateral MLF in the pons and midbrain.

left eye can’t adduct, nystagmus of the CL eye in abduction, eyes can converge, left MLF lesion

Question 6

The right parieto-occipital junction moves the eyes in which direction during smooth pursuit?

Answer 6

To the right.

Question 7

What are the three components of the near reflex?

Answer 7

1. Convergence of the eyes
2. Pupillary constriction
3. Accomodation (lens thickens)

Question 8

Lesions of what structure can cause downward gaze palsy

Answer 8

The red nucleus. (difficulty looking down)

Question 9

What is Argyll-Robertson pupil?

Answer 9

Lack of a light reflex, but pupillary constriction on vergence.

Damages the light reflex, but spares the more ventral pupillary near reflex pathway.

Seen sometimes in tertiary syphilis.

Question 10

What pathway is the rostral interstitial nucleus of the medial longitudinal fasciculus associated with?

Answer 10

The vertical saccade pathway.

Question 11

Where are the burst cells, tonic cells, and pause cells located for vertical saccadic movements?

Answer 11

Vertical:

Burst: Rostral interstitial nucleus of the median longitudinal fissure

Tonic: Interstitial nucleus of cajal

Pause: omnipause cells of the raphe nuclei

Question 12

What are the symptoms of internucler opthalmoplegia?

What if the damage includes the abducens nucleus?

Answer 12

Weak adduction on the side of the lesion.

Nystagmus in the normal eye.

Only see adduction during vergence, rather than smooth pursuit or saccades.

If the abducens nucleus is involved as well, you will lose ipsilateral abduction and contralateral adduction.

Question 13

Where does the smooth pursuit pathway originate?

Answer 13

The parieto-occipital junction

Question 14

Which frontal eye field (right or left) instructs the eyes to perform saccadic movements to the right?

Answer 14

The left frontal eye field.

Question 15

What is the pathway for the Near Reflex?

Answer 15

1. normal visual pathway to striate cortex
2. visual association cortex
3. superior colliculus or pretectal area or both
4. oculomotor nucleus, stimulating medial rectus motor neurons and preganglionic parasympathetics of the Edigner Westphal nucleus
5. the cerebellum helps too

Question 16

What will a CN VI nucleus lesion look like?

Answer 16

Left sided lesion, Pt can’t look left with either eye

left eye can’t abduct

right eye cant adduct

Question 17

What does a CN VI palsy look like?

Answer 17

Left sided lesion-left eye can’t abduct

Question 18

What will a lesion of the parietal lobe cause in the smooth pursuit movements?

Answer 18

loss of smooth pursiot movement toward the side of the lesion

No OKN when tape is moved toward the damaged lobe

Question 19

What is the purpose of the optokinetic mechanism?

Answer 19

holds images steady on the retina during sustained head rotation

uses smooth pursuit pathway and nuclei of the accessory optic sytem

eyes make quick move in opposite direction

requires intact parietoocipital field

Question 20

What is the purpose of smooth pursuit?

If left hemisphere is activated, which way to the eyes move?

Answer 20

keeps moving object centered on fovea using brodmann’s area 19 aka parieto-occipita; area

horizontal-CN 6 and 3

vertical: CN 3 and 4

left hemisphere-eyes move left in smooth pursuit

Question 21

A lesion (Stroke) of the frontal gaze center will cause?

Irritation (Sz) of the frontal gaze center will cause?

Answer 21

transient conjugate eye deviation TOWARD the side of the lesion, difficult to look away

eyes deviate away from the firing gaze center

Question 22

what do we associate with the superior colliculis?

Answer 22

reflexive saccades

Question 23

Damage to the PPRF system in the horiztonal saccade system will cause?

Answer 23

left lesion of PPRF-both eyes CAN’T look left

right lesion of PPRF-both eyes CAN’T look right

Question 24

Lesions of the riMLF in the vertical saccade system will causes

Answer 24

trouble looking UP

often caused by pineal tumor pressing down (near posterior commisures and pineal gland)

Question 25

functions of:

Burst Neurons

Tonic Neurons

Pause Neurons

Answer 25

B: move eyes to target

T: lock and fix on target

P: inhibit burst, stop motion on target