Apraxia, Agnosia and higher visual function abnormalities

Question 1

Apraxia

Answer 1

Apraxia is a neurological disorder characterized by the inability to perform learned (familiar) movements on command, even though the command is understood and there is a willingness to perform the movement.

Question 2

Agnosia

Answer 2

Agnosia is a rare disorder whereby a patient is unable to recognize and identify objects, persons, or sounds using one or more of their senses despite otherwise normally functioning senses.

Question 3

Visual neglect

Answer 3

Deficit in visual attention to self or external object.
Almost always occuring for the left hemifield, as the left hemisphere monitors the right hemifield, while
the right hemisphere monitors both hemifields. Visual neglect is caused by lesions in the inferior parietal lobe.

Question 4

Anosognosia

Answer 4

“inability to recognise consciously the presence of a somatic dysfunction indicative of a disease process.”

Up to complete unawareness of the deficit, e.g., in some cases of hemiplegia (complete paralysis of one half of the body) after a stroke. Primarily occurs with non-dominant parietal lesions, and is rather a disorder of attention than of perception

Question 5

Answer 5

Question 6

Visual Agnosia

Answer 6

“A modality specific inability to access semantic knowledge of an object or other stimulus that cannot be attributed to impairment of basic perceptual processes.”

Question 7

Apperceptive visual agnosia

Answer 7

Impairment of high level percepts, caused by bilateral occipitotemporal infarction (a in the pic).
Often, retained semantic knowledge accessible through
other modalities such as auditory, which is not the case for associative visual agnosia.

Question 8

Associative visual agnosia

Answer 8

Inability to activate semantic identifying information, caused by dysfunction in anterior left temporal lobe (b in the pic)
More general loss of semantic knowledge, with no ability to access this via any sensory modality.

Associative visual agnosia patients experience no difficulties in perception, only in naming and semantic knowledge.

Question 9

There are two kinds of Alexia - which?

Answer 9

Peripheral Alexia:
Difficulty transmitting the visual percept to the intact language centres. Caused by ocular problems or visual field defect/neglect.
Subtype is Alexia without Agraphia, where patients can write, but not read what they have just written.

Central Alexia:
Impaired language system

Question 10

Prosopagnosia and related disorders

Answer 10

Inability to recognize people by looking at their face.
Ventral occipitotemporal pathology (especially right side) is observed.

Related disorders:
-Capgras syndrome : Belief that familiar people around one replaced by imposter.

-Fregoli syndrome: Belief that strangers of changing their appearance in disguise

Question 11

Achromatopsia

Answer 11

Achromatopsia is a condition characterized by a partial or total absence of color vision. People with complete achromatopsia cannot perceive any colors; they see only black, white, and shades of gray.

Question 12

Color agnosia and color anomia - whats the difference?

Answer 12

Color agnosia is the inability to retrieve color information in the context of normal perception and language. For example, a patient with color agnosia will be unable to remember the colors of common entities (e.g., “What color is a banana?”) and will be unable to provide a list of objects that come in various colors (e.g., “Name things that are red”)

In color Anomia, perception and semantic knowledge is preserved, however, there is deficits in naming the color.

Question 13

What are the three common aspects of Balint’s syndrome?

Answer 13

-simultanagnosia (inability to perceive visual scene as a whole)

-optic ataxia (inability to reach an specific object
by using vision)

-motor apraxia (difficulty in fixating eyes to
a visual target).

Question 14

Dressing apraxia

Answer 14

In a strict sense, dressing apraxia is not caused by movement disorders, but is related to disorientation of the spatial relationship between the body and clothes.

Question 15

Constructional apraxia

Answer 15

Constructional apraxia refers to the inability of patients to copy accurately drawings or three-dimensional constructions. Left hemisphere damage result in simple drawing, however, right hemisphere damage result in difficulty with replicating spatial relationship of complex figures.

Question 16

Topographagnosia

Answer 16

The inability to find one’s way in a familiar environments and to learn new routes. Deficits in either ventral or dorsal visual association.

Question 17

The difference between Anton’s syndrome and blindsight

Answer 17

Anton’s syndrome: Denial of loss of vision even with functional blindness.

Blindsight: Blindsight is the ability of people who are cortically blind due to lesions in their striate cortex (V1) to respond to visual stimuli that they do not consciously see.

Blindsight = seeing even though you think you can't
Anton's = not seeing even though you think you can

Pick your poison

Question 18

Two examples of visual gain:

• Charles Bonnet syndrome
• Peduncular hallucinosis

Answer 18

Charles Bonnet syndrome: Visual disturbance in which a person with partial or severe blindness experiences visual hallucinations. Often arises in elderly as a result of ocular pathology. Images tends to be complex.

Peduncular hallucinosis: Vivid hallucination may arise in the evening times as a result of midbrain strokes, however, tends to disappear within weeks.

Question 19

Answer 19

Question 20

Conceptual system for actions vs Action production system

What are they?

Answer 20

Conceptual system for action:

• knowledge of tool functions and actions
• e.g. the purpose of a screwdriver

Action production system

• Sensorimotor action programmes concerned with generation and control over movement
• e.g. the ability to tighten a screw

This is an important distinction which can be used to divide diagnostic tests when examining patients with specific deficits.

Question 21

Ideational apraxia

Answer 21

Caused by damage to the conceptual system for action.
A condition in which an individual is unable to plan movements related to interaction with objects, because they have lost the perception of the object’s purpose.

• contents and tool selection errors
• exhibit loss of tool-object action knowledge
• exhibit loss of tool-object association knowledge

Commonly seen in Alzheimer’s disease

Question 22

Ideomotor apraxia

Answer 22

Damage to the Action Production System.

Patients appear to have a rough sense of the desired action but have problems executing it properly.

2 types of errors:
Spatial errors
- postural error
- spatial orientation
- spatial movement

Temporal error:
- fluidity of movement

Most commonly associated with lesions to the premotor cortex.