Questions:
1. What are the names and functions of the 2 visual higher cortical function processing streams?
2. What are the findings in a patient with alexia without agraphia?
3. Where is the lesion in alexia without agraphia?
4. What is prosopagnosia?
5. What is visual object agnosia?
6. What is optic aphasia?
7. What is topographagnosia?
8. What is akinetopsia?
9. What is simultagnosia?
10. What is ocular apraxia?
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Questions with answers:
1. What are the names and functions of the 2 visual higher cortical function processing streams?
1. The inferior (ventral) or occipitotemporal pathway for object recognition (the what stream)
2. The superior (dorsal) or occipitoparietal pathway for object localization (the where stream).
2. What are the findings in a patient with alexia without agraphia?
It is the Higher Cortical Disorder in which the patient able to write but not read. It is associated with a right homonymous hemianopia.
3. Where is the lesion in alexia without agraphia?
Left occipital lobe and splenium of corpus callosum
4. What is prosopagnosia?
It is the Higher Cortical Disorder in which the patient cannot recognize famous people or identify familiar faces.
5. What is visual object agnosia?
It is the Higher Cortical Disorder in which the patient is unable to identify objects by sight but can give a verbal description or recognize the object by another sensory modality (e.g. touch).
6. What is optic aphasia?
It is the Higher Cortical Disorder in which the patient is unable to name visually presented objects or point to named objects. These patients are able to name and recognize what he or she hears or feels.
7. What is topographagnosia?
It is the Higher Cortical Disorder in which the patient is unable to identify familiar landmarks and buildings.
8. What is akinetopsia?
It is an extremely rare Higher Cortical Disorder in which the patient shows impairment of motion perception (motion blindness).
9. What is simultagnosia?
It is the Higher Cortical Disorder in which the patient inability to grasp the entire meaning of a picture despite an intact capacity to recognize the picture’s individual constituent elements. On the Ishihara color plates they can recognize colors but not identify the numbers on the plates.
10. What is ocular apraxia?
It is the Higher Cortical Disorder in which the patient cannot look at a specific object that can be seen (deficit in shifting gaze, AKA psychic gaze paralysis, spasm of fixation).
Explanation: “10 Disorders of Higher Cortical Function
Unlike the anterior visual and geniculocalcarine pathways that deliver basic visual information from the eyes to the occipital cortex, association cortical visual areas (higher cortical areas) perform the more complex interpretation of visual information. Many of the syndromes of higher cortical dysfunction are secondary to a disconnection of the flow of visual information between the striate cortex and other cortical regions. When these areas are damaged, visual processing is abnormal despite often normal visual acuity and visual fields.
This chapter focuses on some of the main visual disorders of higher cortical function, particularly their clinical and radiologic findings and causes, commonly encountered in neuro-ophthalmology.
10.1 Classification
Disorders of higher cortical function are often grouped into two processing streams. The first stream, the inferior (ventral) or occipitotemporal pathway for object recognition, extends from below the calcarine fissure into the adjacent temporal lobe. It facilitates object recognition and color perception. Disorders here include achromatopsia, prosopagnosia, alexia, and topographagnosia.
The second stream, the superior (dorsal) or occipitoparietal pathway for object localization extends from the upper bank of the calcarine fissure into the adjacent parietal lobe. It processes visuospatial attributes, including location and motion. Disorders here include akinetopsia, Balint syndrome (simultagnosia, ocular apraxia, and optic ataxia), and hemineglect.
▶Table 10.1 lists the clinical findings, recommended tests, associated clinical signs, and lesions associated with these higher cortical disorders.
Reference:
1. Neuro-ophthalmology Illustrated-2nd Edition. Biousse V and Newman NJ. 2012. Theme.
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