ND - Brain Lesions Causing Visual Field Defects - Week 2 Flashcards
Define homonymous.
Same side
List three possible locations of a lesion if it is chiasmal.
Chiasm
Optic tract
Lateral geniculate nucleus
List three possible locations of a lesion if it is post-chiasmal.
Parietal lobe
Occipital lobe
Other
List the four descriptors that a visual field loss of brain origin needs.
Side (R/L)
Nature (Homonymous/bitemporal/nasal)
Congruity (similarity)
Type of defect - hemianopia/quadrantanopia etc
What are VF defects in the arcuate region called (isolated)? What about if they are joined to BS?
If isolated, Bjerrum scotoma
Otherwise is called arcuate if joined to BS
What can early loss of superficial GCs lead to in terms of ONH appearance?
Gives a steep cup with a notch paracentral to Bjerrum scotoma
What can early loss of deep GCs lead to in terms of ONH appearance?
Gives a honeycomb and saucerised cup appearance
What does a VF defect involve if it respects the horizontal midline?
It involves the RGCs
What do altitudinal VF defects usually indicate for and where?
Ischaemia of one pole of the ONH
Can a banana VF defect be ONH or retina or both?
Could be either
True or false
Defects at or beyond the chaism will affect VF in both eyes.
True
What does a bowtie atrophy indicate the presence of?
A lesion in the contralateral optic tract involving crossed retinal fibres nasal to the fovea.
Are individuals with bitemporal hemianopia symptomatic? Explain.
Total chiasmal VF hemi-defect can give a hemi-field slide due to the loss of fusion (such as with hyper/eso/exophoria), and this can manifest habitual heterophoria
Where is the defect for a pie in the sky VF?
Post-chiasmal - temporal lobe
Where is the defect for a pie on the floor VF?
Post-chiasmal - parietal lobe
Define the Riddoch phenomenom. What kind of lesions can it occur in?
Perfecption of movement but loss of form
Can occur in occipital lesion
Define cortical blindness. What happens to the artery involved?
Total blindness due to bilateral occipital lobe lesions
It infarcts the basilar artery
Do pupils react normally in cortical blindness? What about their ERG/VER responses?
Pupil responses are fine
ERG is fine
VER is abnormal
Can individuals with cortical blindness have motion perception?
Yes but residual
Do individuals with cortical blindness present with a normal fundus exam?
Yesd
Is hallucination possible with cortical blindness? Explain.
Yesd, they may have visual percepts (this is CBS) and deny blindness.
They hallucinate - Anton’s syndrom.
Describe the procedure to test for cortical VF loss. What does indicate for? What can happen with chronic cases?
Amsler grid
Indicates for scotoma
Cortical filling occurs with chronic cases
What two things is simultaneous confrontation good for and not good for?
Good
Screening and testing large peripheral defects
Sensitivity
Not good
Retinal or optic lesions
Small defects