Control of Eye Movements Flashcards
medial and lateral rectus
adduct & abduct
upgaze
superior rectus
inferior oblique
down fze
inferior rectus
superior oblique
CN III exits at
interpedunular fossa of midbrain
CN IV exits at
(trochlear)
dorsum of brainstem - caudal midbrain and wraps around brainstem
CN VI
(abducens) brainstem- medullary pontine junction
ipslateral vs contralateral
CN IV is contralateral, rest are ipsi
what else travels in occulomotor nerves
parasymps
PS in occulomotor
arise from Edinger-Westphal nucleus–>synapse in ciliary gnaglion with post gang–>lens becomes rounder
compression of 3rd CN
pupil dilation
afferent projections of occulomotor
pretectal region
what is CN 3 in close contact with when comes out of interpendicular fossa
posterior cerebral and posterior communicating artery–> aneurysms
where is an area that extraoccular nerves are often damaged?
pituitary fossa or cavernous sinus
trochlear pathway
rostral pons/caudal midbrain (trochlear nucleus)
- ->decussates in brainstem
- ->exits from dorsal side brainstem at ponto-mesencephalic junction
*passes in lateral cavernous sinus
abducens pathway
caudal pons–>leaves brainstem at medullary pontine junction
saccadic eye movements
very rapid jump in eye to acquire new target or follow moving target
5th of a second processing delay
when extraoccular nerve damaged
drift TOWARDS muscle
voluntary eye movements
cerebral cortex/superior colliculus–> paramedian reticular formation
head turn vs saccade
head turns 20-40 ms after saccade
microsaccade
keeps imagine from staying on same rod or cone too long
Voluntary Horizontal Gaze pathway
R frontal eye field of cerebral cortex –>right superior colliculus–decussate–>left paramedian pontine reticular formation–>left CNV1
..–> to L lateral rectus
..through MLF contralaterally to right CN III–>R medial rectus
TOWARDS the PPRF involved (towards left)
sensory aspect of superior colliculus
retina (vision)
inferior colliculus (sound)
spinal cord (somatic sensation)
cerebral cortex
motor aspect of superior colliculus
eye/head movements
from spinal cord (tectospinal tract) & brainstem (tectoreticular tract)
medial longitudinal funiculus
interconnects nuclei of extraoccular muscles to coordinate conjugate eye movements
damage to MLF
internuclear opthalmoplegia
eye movement laterally is not followed by medial movement of other eye
voluntary vertical gaze pathway
diffuse areas of cerebral cortex
–>rostral interstital nucleus
–> posterior commissure for upgaze
OR –>CN III and IV
parinaud-Syndrome
eyes retract in back of head when try to look up
–>due to pressure from expanding mass dorsal to midbrain
Progressive supranuclear palsy
patient cant look up or down voluntarilly, but when head is flexed or extended, eyes can move in these directions
degenreation of vertical gaze center
vertical gaze center
rostral interstitial nucleus
vestibulooccular reflex
eye movements in response to change in head
vestibuloccular reflex pathway
CNVII -->flocculus -->vestibular nucleus OR -->vestibular nucleus -->CN VI, PPRF --MLF-->CN III, IV
damage to vestibuloccular reflex
nystagmus
- -drift of eyes as if eyes head was moving
- -triggers rapid saccadic eye movement to original target
- jerky, repetitive eye movement
tracking
eyes move smoothly only when you are tracking or when your head is moving
voluntarily but needs a stimulus
smooth pursuit/tracking pathway
occipital eye field -->pontine nucleus OR -->frontal eye movt-->pontine nucleus -->middle cerebellar peduncle -->contralateral flocculus -->inferior cerebral peduncle -->ipsilateral vestibular complex -->CN VI, PPRF (bilaterally) --MLF-->CN III, CN IV
occipital eye fields are not
well defined in occipital lobe
–region near junction of occipital lobes with posterior parietal and temporal lobe
includes areas involved in interpreting movement of objects
fixation and optokinetic reflexes
use same wiring as smooth pursuit
fixation
ability to fixate on a moving target
–complements vestibulooccular to stabilize eyes
optokinetic
involves fixation on objects that are moving in relation to the head
(like when moving in a car)-eyes tracking object involuntarily for a distance and saccade in opposite direction to re-aqcuire target
if one visua cortex is damage
opto is damaged in that nystagmus is lost when bjects move TOWRDS side of damaged cortex lesion (away from side of vision loss)
vergence
convergence or divergence of eyes in order to focus close-up or off in a distance
vergence pathway
occipital cortical projections–>vergence center in mesencephalic RF
vergence is wire in parallel with
accomodation
–pupillary constriction and contraction of cillary muscle occurs at same time to allow for close focus
pupillary light reflex
bilateral constriction of pupil in response to light stimulus
R retina–>R pretectal nuclei–>R edinger westphal OR L edinger westphal (through posterior commissure)
pendular nystagmus
oscillations equal in both directions
NOT due to CNS or vestibular damage
jerk nystagmus
slow and fast component
indicates problem with vestibular system (iinner ear nerves, nerves to flocculus, vest nuclei, MLF)
slow component is
imbalance in vestibular nuclei
fast component
awareness of cerebral cortex and evoke fixation
vertical gaze center
rostral interstial nucleus of MLF
horizontal gaze center
PPRFe
