ND - Perceptual Disorders as a Higher Level Dysfunction - Week 9 Flashcards

1
Q

Define visual illusion.

A

Describes visual images that are not the same as the physical reality of the stimulus.
There is an alteration of the interpretation of the physical stimulus.

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2
Q

Define hallucination.

A

An experience involving the apparent perception of something that is not present

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3
Q

Are most visual distortions due to eye disease positive or negative?

A

Negative

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4
Q

List 2 reasons why patients can experience positive visual phenomena. What senses can it affect (3)? Give two examples.

A

Due to abnormal retinal/cortical processing
Can affect auditory, olfactory, and visual senses
Flashes
-due to vitreo-retinal traction
-due to elevated IOP

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5
Q

What is an illusion?

A

Distortion or misinterpretation of a visual input

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6
Q

In what state do illusions occur?

A

Awake people with eyes open

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7
Q

Do illusions involve unusual or normal neural processing?

A

Either

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8
Q

What are pathological illusions due to?

A

Aberrant image processing

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9
Q

Give two ocular causes for pathological illusions and give three examples.

A

Optical
-aniseikonia caused by astigmatism
-anismometropia
Retinal
-due to vitreo-retinal traction

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10
Q

Give two examples of cortical pathological illusions.

A

Palinopsia
Alice in Wonderland syndrome

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11
Q

List three ways to differentiate an ocular vs cortical cause of pathological illusions.

A

One eye (retinal) vs one hemifield
If homonymous, then cortical
Higher order distortions give complex perceptual illusions (shape, depth etc)

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12
Q

What is palinopsia? What is it known as in normal conditions? What about in disease conditions?

A

Propensity for an ìmâgé to persist even after the stimulus has left
In normal conditions it is known as an after-image
In disease conditions, it is exaggerated and called palinopsia

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13
Q

What are four characteristics of palinopsia?

A

Increased duration of the afterimage (tracer - blur)
Reduced amount of time to form an after-image
Positive after-images become noticeable with routine eye movements
Negative after-images also possible (inverted colours)

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14
Q

Are standard after-images positive or negative?

A

Negative

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15
Q

Dysfunction in what region is associated with palinopsia?

A

Brain/cortical dysfunction or pathology

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16
Q

Individuals with what two conditions can experience palinopsia?

A

Migraine sufferers
Visual snow

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17
Q

What are stop-motion action pictures? What is it due to? What percentage of indivduals does it affect (which kind of individuals specifically)?

A

Trailing after ingestion of hallucinogens (serotonin receptor excitotoxicity)
Affectd ~10% of people with migraine

18
Q

What is alice in wonderland syndrome and how long can it last? How long does it last typically?

A

Distortion/illusion that lasts between minutes to days in prone people. Typical duration is ~20 minutes.

19
Q

What is the most prominent symptom of alice in wonderland syndrome?

A

Altered body image, which is disturbing

20
Q

List four characteristics of alice in wonderland syndrome.

A

Sensory distortions, especially touch and hearing
Altered body image
Change in size of inanimate objects

21
Q

List 4 diseases associated with alice in wonderland syndrome.

A

Migraine
Epilepsy
Cerebral lesions
Schizophrenia

22
Q

What are two forms of aura that can occur with alice in wonderland syndrome?

A

Gross magnification of hands/face
Body as taller after enlarging feet

23
Q

Do visual hallucinations require vision? Can they be seen with eyes closed?

A

Vision not needed, can be seen with eyes closed

24
Q

What causes hallucinations (2)? What does this mean?

A

Aberrant inhibition or overexcitation of the brain - doesnt require visual input

25
Q

List three categorisations for visual hallucinations and give two major causes for each.

A

Hallucinations that are isolated findings
-drug induced
-subsequent to vision loss
Hallucinations associated with sleep/trance
-trance-like
-sleep induced
Hallucinations as part of specific pathology
-dementia
psychoses

26
Q

List two syndrome types for hallucinations that arise subsequent to vision loss, and give an example for each.

A

Cortical syndromes
-posterior cortical atrophy
Ocular syndromes
-charles bonnet syndrome

27
Q

What is a cause of posterior cortical atrophy and what is it considered a variant of?

A

Lesion of the primary visual cortex, visual pathway, midbrain, or thalamus
Considered a variant of alzhiemers disease

28
Q

What impairment does posterior cortical atrophy result in (2)?

A

Spatial and percentual impairment?

29
Q

In what percentage of posterior cortical atrophy cases do hallucinations occur? What is needed for this to occur (2)?

A

25%
Requires damage across multiple sites or to a network of interconnecting structures

30
Q

Activation of what brain region are related to hallucinations? Explain how this occurs with loss of vision exactly.

A

Cortical activation in the lateral infero-temporal cortex
Lack of stimulation of visual areas due to loss of vision or a cortical lesion leads to reduced inhibition of the lateral infero-temporal cortex by these areas, giving spontaneous activation of IT neurons, resulting in hallucinations

31
Q

What kind of hallucinations are present in charles-bonnet syndrome? Is cognition intact? What is this syndrome produced by?

A

Hallucinations caused by binocular eye diseases, where cognition is intact
Produced by any disease resulting in bilateral visiond loss

32
Q

List 2 typical casues of charles-bonnet syndrome.

A

Bilateral AMD
Bilateral glaucoma

33
Q

What is the timing and frequency of CBS like?

A

Can vary widely

34
Q

How long can CBS hallucinations last?

A

Usually several minutes, but can be seconds or hours

35
Q

What is a problem with diagnosing CBS (aside from it being a diagnosis by exclusion)?

A

High rate of patient non-reporting of visual hallucinations to care providers due to feal or psychotic labelling

36
Q

What is the mainstay of CBS management? List three additional treatment options.

A

Mainstay is patient reassurance and education on cause
Can also improve visual function, increased social interaction, and improved lighting

37
Q

What does anton-babinski syndrome occur in conjunction with? Is this syndrome common or rare?

A

Very rare
Occurs in conjunction with a sudden bilateral occipital dysfunction

38
Q

What is the visual status of someone with anton-babinski syndrome? How do these individuals behave when interacting with someone?

A

Patient is blind, but behave and talk as though they can see

39
Q

What is visual sno?

A

Continuous appearance of visual static

40
Q

List the diagnostic criteria for visual snow (4).

A

Dynamic visual snow for more than 3 months
At least two additional visual symptoms of palinopsia, entopic phenomena, photophobia, or nytalopia
Symptoms not consistent with typical migraine visual aura
Symptoms not better explained by any other disorder or psychotic drug intake

41
Q

Is visual snow easy to diagnose? Explain.

A

Often misdiagnosed due to lack of objective signs