8. Control of Eye Movements (Keim) Flashcards
(25 cards)
Where are the burst cells, tonic cells, and pause cells located for horizontal saccadic movements?
Horizontal
Burst cells: Paramedian pontine reticular formation
Tonic cells: Nucleus prepositus hypoglossi
Pause cells: Omnipause cells of raphe nuclei
What three locations are associated with upward gaze?
Tumor of what structure can damage these?
Superior colliculus
Posteiror commissure
Pretectal area
Pineal gland tumors can damage these and result in palsy of upward gaze. (difficulty looking up)
What is the key clinical difference between the vergence pathway and the other pathways of eye adduction?
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.
Which region of the brain performs volitional and reflexive saccades respectively?
Volitional saccades: Frontal eye field.
Reflexive saccades: Superior colliculus.
Where is the damage in intranuclear opthalmoplegia?
what are the sx?
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
The right parieto-occipital junction moves the eyes in which direction during smooth pursuit?
To the right.
What are the three components of the near reflex?
- Convergence of the eyes
- Pupillary constriction
- Accomodation (lens thickens)
Lesions of what structure can cause downward gaze palsy
The red nucleus. (difficulty looking down)
What is Argyll-Robertson pupil?
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.
What pathway is the rostral interstitial nucleus of the medial longitudinal fasciculus associated with?
The vertical saccade pathway.
Where are the burst cells, tonic cells, and pause cells located for vertical saccadic movements?
Vertical:
Burst: Rostral interstitial nucleus of the median longitudinal fissure
Tonic: Interstitial nucleus of cajal
Pause: omnipause cells of the raphe nuclei
What are the symptoms of internucler opthalmoplegia?
What if the damage includes the abducens nucleus?
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.
Where does the smooth pursuit pathway originate?
The parieto-occipital junction
Which frontal eye field (right or left) instructs the eyes to perform saccadic movements to the right?
The left frontal eye field.
What is the pathway for the Near Reflex?
- normal visual pathway to striate cortex
- visual association cortex
- superior colliculus or pretectal area or both
- oculomotor nucleus, stimulating medial rectus motor neurons and preganglionic parasympathetics of the Edigner Westphal nucleus
- the cerebellum helps too
What will a CN VI nucleus lesion look like?
Left sided lesion, Pt can’t look left with either eye
left eye can’t abduct
right eye cant adduct
What does a CN VI palsy look like?
Left sided lesion-left eye can’t abduct
What will a lesion of the parietal lobe cause in the smooth pursuit movements?
loss of smooth pursiot movement toward the side of the lesion
No OKN when tape is moved toward the damaged lobe
What is the purpose of the optokinetic mechanism?
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
What is the purpose of smooth pursuit?
If left hemisphere is activated, which way to the eyes move?
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
A lesion (Stroke) of the frontal gaze center will cause?
Irritation (Sz) of the frontal gaze center will cause?
transient conjugate eye deviation TOWARD the side of the lesion, difficult to look away
eyes deviate away from the firing gaze center
what do we associate with the superior colliculis?
reflexive saccades
Damage to the PPRF system in the horiztonal saccade system will cause?
left lesion of PPRF-both eyes CAN’T look left
right lesion of PPRF-both eyes CAN’T look right
Lesions of the riMLF in the vertical saccade system will causes
trouble looking UP
often caused by pineal tumor pressing down (near posterior commisures and pineal gland)
