wk2: ND - Brain lesions causing visual field defects Flashcards

1
Q

List 3 possible locations of a lesion if it is post-chiasmal

A

Parietal lobe
Occipital lobe
Other

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2
Q

List 4 descriptors of visual field loss arising from brain origin

A

Side (R or L)
Nature (homonymous or bitemporal, binasal)
Congruity (similarity e.g. in terms of severity)
Type (e.g. hemianopia, sup or inf quandrantanopia or sectoranopia)

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3
Q

How can you differentiate a non-glaucomatous visual field loss from a glaucomatous one?

A

Non-glaucomatous defects generally stop when they reach the vertical midline (in fundus) rather than the horizontal one

i.e. a glaucoma defect will NOT respect this vertical midline

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4
Q

Where is a visual field defect most likely located if it respects the vertical midline?

A

Posterior to chiasm (post-chiasmal, so further up in visual pathway) (could even just be chiasmal too based on lecture slides)

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5
Q

Where is a visual field defect most likely located if it respects the horizontal midline?

A

Anterior to chiasm (so pre-chiasmal, think optic nerve, retina)

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6
Q

What type of pattern is shown by visual field loss from optic nerve defects?

A

Arcuate patterns

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7
Q

What are visual field defects in the arcuate region called (when isolated)?

A

Bjerrum scotoma

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8
Q

What are visual field defects in the arcuate region called (when joined with BS)?

A

Arcuate

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9
Q

How does early loss of superficial GCs affect ONH appearance? (2)

A

steep cup with notch paracentral to Bjerrum scotoma

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10
Q

How does an early loss of deep GCs affect ONH appearance? (2)

A

honeycomb and “saucerised” cup and Bjerrum scotom with nasal step

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11
Q

Can retinal visual field defects cross the midlines?

A

yes

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12
Q

What does a retinal visual field defect involve if it respects the horizontal midline? (1)

A

RGCs

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13
Q

What do altitudinal visual field defects usually indicate for?

A

ischaemia for one pole of the ONH

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14
Q

Where might be responsible for a banana visual field defect? (2)

A

Optic Nerve or

Retina

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15
Q

What should you consider first when you see steep sided total peripheral visual field loss?

A

Could be functional (i.e. consciously or unconsciously deciding they can’t see in certain regions)

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16
Q

True/False: Defects at or beyond the chiasm will affect the VF in both eyes

A

True

17
Q

List 3 possible locations of a lesion if it is chiasmal

A

Chiasm
Optic tract
LGN

18
Q

Explain the reasoning behind why lesions at certain locations respect certain midlines?

A

Has to do with the optic nerve fibres, which travel the shortest path they need to get where they need to go

19
Q

What type of defect does Band (bowtie) optic atrophy indicate for?

A

Optic tract lesion in the contralateral optic tract, involving crossed retinal fibres nasal to the fovea (e.g. long standing pituitary lesion)

20
Q

Are people with bitemporal hemianopia symptomatic? Explain

A

Sort of, yeah. Total chiasmal VF hemi-defect can give a hemifield slide due to the loss of fusion (such as with hyper/eso/exphoria), and this can manifest as the patient’s habitual heterophoria

Physiologically, nasal and temporal visual fields overlap between the right and left eyes and allows corresponding retinal points to be established. Fusion allows the two images, one from each eye to be combined into one coherent image.[1][2] Heteronymous hemianopic defects disrupts this fusion due to the absence of right and left visual field overlap and makes maintaining stable orthotropia difficult.[3] Manifestation of horizontal or vertical tropia/phoria causes the hemifields to slide vertically or horizontally respective to one another, resulting in diplopia.[1][3]

21
Q

Define “hemifield slide”

A

Hemifield slide describes the phenomenon of inability to stabilise and fuse visual hemifields in the setting of heteronymous visual field loss.1,2 This presumably results from loss of corresponding retinal points in the two eyes, allowing an underlying phoria to manifest as a tropia, or instability of ocular alignment.

22
Q

Where does a “pie in the sky” VF defect come from?

A

Temporal lobe

(note: pie in the sky is a superior vf defect obv)
(note: not to be confused with Arnie pie in the sky, from the simpsons)

23
Q

Where does a “pie on the floor” VF defect come from?

A

Parietal lobe

24
Q

Why might a patient be unaware of VF defect? (1) What must you do to ensure no VF defect? (1)

A

Foveal sparing. Do confrontation on everyone

25
Q

Define the Riddoch phenomenon. What kind of lesions can it occur in?

A

Perception of movement but loss of form. Can occur in occipital lobe lesions

26
Q

How might the Riddoch phenomenon be found in a patient?

A

Loss in static perimetry but normal kinetic perimetry

27
Q

Define cortical blindness. What happens to the artery involved?

A

Total blindness due to bilateral occipital lobe lesions. Bilateral infarcts of basilar artery

28
Q

How will an (adult) patient with cortical blindness present after testing in your clinic? (6)

A

Pupils: ok
ERG: ok
VER: abnormal
May have residual motion perception (“blindsight”)
Fundus: normal
May have visual percepts (CBS, charles bonnet) and deny

29
Q

Is hallucination possible with cortical blindness?

A

Yep

30
Q

Describe the procedure for testing for corticalVF loss. What does it indicate for? What can happen with chronic cases?

A

Amsler grid
Indicates for scotoma
Cortical filling occurs with chronic cases

31
Q

What two things is simultaneous confrontation good for and not good for?

A
Good: 
Screening and testing large perpheral defects
Sensitivity
Not good:
Retinal or optic lesions
Small defects