Ch 7: Clinical Correlates ph 188-193 Flashcards
what forms the meyer’s loop?
lateral fibers from the lower retinal quadrants that project to the lingual gyrus
in the temporal lobe, what supplies blood to meyer’s loop?
inferior division of MCA
a stroke that involves the inferior division of MCA can cause…
contralateral homonymous superior quadrantoanopsia (lesion to Meyer’s loop)
non-Meyer’s loop fibers are supplied what what artery?
PCA
a lesion to visual radiations, not part of Meyer’s loop can cause…
contralateral homonymous inferior quadrantanopsia
lesions in primary visual cortex caused by stroke involving PCA can cause…
contralateral homonymous hemianopsia that is macular sparing
*macular cortex receives dual blood supply from PCA and MCA
bilateral lesion to MLF results in…
INO–>inability to adduct either eye on attempted conjugate horizontal gaze (convergence will be intact)
also will exhibit monocular nystagmus of the abducting eye
*common in MS
stimulation of the PPRF results in…
ipsilateral horizontal conjuguate gaze
*R PPRF–>abduction of right eye, adduction of left eye and horizontal gaze to the right
one and a half syndrome is caused by
unilateral lesion of the PPRF, abducens nucleus and axons of the MLF form the PPRF
what signs will be seen with one and a half syndrome?
inability to look horizontally toward the side of the lesion with either eye. horizontal gaze is limited to an ability to abduct the eye on the side opposite the lesion. (can only move one eye one way…)
lesions of the frontal eye field results in what signs?
inability to voluntarily generate contralateral horizontal saccades in the absence of a target–>deviation of eyes toward side of lesion
if affects adjacent primary motor cortex–>spastic weakness of contralateral upper limb and lower face
lesion of superior colliculus results in…
transient changes in accuracy, velocity, and frequency of saccades
FEF can still generate saccades, so deficits usually improve with time
occulsion of the basilar artery between the branch points of AICA and superior cerebellar arteries can cause…
locked in state
what are the signs associated with locked-in state?
bilateral lesions of corticospinal tract–>spatic quadriplegia
bilateral corticobulbar lesions–>weakness of all CN innervated muscles except oculomotor!
body and face sensations intact, hearing preserved, and ascending arousal system unaffected
patients are fully awake and aware but can communicate only by attempting to blink or moving eyes vertically
how can locked-in state be tested in regards to the eyes?
cold-water caloric testing: will cause horizontal deviation of eyes toward cold water stimulus without corrective/fast nystagmus because FEF that generate this phase are disconnected from PPRF
