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  3. Agnosia
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Agnosia


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Other Names:
Primary visual agnosia; Monomodal visual amnesia; Visual amnesia
Categories:
Nervous System Diseases

Summary Summary


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Agnosia is characterized by an inability to recognize and identify objects and/or persons. Symptoms may vary, according to the area of the brain that is affected.[1] It can be limited to one sensory modality such as vision or hearing; for example, a person may have difficulty in recognizing an object as a cup or identifying a sound as a cough. Agnosia can result from strokes, traumatic brain injury, dementia, a tumor, developmental disorders, overexposure to environmental toxins (e.g., carbon monoxide poisoning), or other neurological conditions.[2][1] Visual agnosia may also occur in association with other underlying disorders.[1] People with agnosia may retain their cognitive abilities in other areas.[2] Treatment of primary agnosia is symptomatic and supportive; when it is caused by an underlying disorder, treatment of the disorder may reduce symptoms and help prevent further brain damage.[1]
Last updated: 4/22/2011

Symptoms Symptoms


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People with primary visual agnosia may have one or several impairments in visual recognition without impairment of intelligence, motivation, and/or attention. Vision is almost always intact and the mind is clear. Some affected individuals do not have the ability to recognize familiar objects. They can see objects, but are unable to identify them by sight. However, objects may be identified by touch, sound, and/or smell. For example, affected individuals may not be able to identify a set of keys by sight, but can identify them upon holding them in their hands.

Some researchers separate visual agnosia into two broad categories: apperceptive agnosia and associative agnosia. Apperceptive agnosia refers to individuals who cannot properly process what they see, meaning they have difficult identifying shapes or differentiating between different objects (visual stimuli). Affected individuals may not be able to recognize that pictures of the same object from different angles are of the same object. Affected individuals may be unable to copy (e.g., draw a picture) of an object. Associative agnosia refers to people who cannot match an object with their memory. They can accurately describe an object and even draw a picture of the object, but are unable to state what the object is or is used for. However, if told verbally what the object is, an affected individual will be able to describe what it is used for.

In some cases, individuals with primary visual agnosia cannot identify familiar people (prosopagnosia). They can see the person clearly and can describe the person (e.g., hair and eye color), but cannot identify the person by name. People with prosopagnosia may identify people by touch, smell, speech, or the way that they walk (gait). In some rare cases, affected individuals cannot recognize their own face.

Some people have a form of primary visual agnosia associated with the loss of the ability to identify their surroundings (loss of environmental familiarity agnosia). Symptoms include the inability to recognize familiar places or buildings. Affected individuals may be able to describe a familiar environment from memory and point to it on a map.

Simultanagnosia is a characterized by the inability to read and the inability to view one's surroundings as a whole. The affected individual can see parts of the surrounding scene, but not the whole. There is an inability to comprehend more than one part of a visual scene at a time or to coordinate the parts.

In rare cases, people with primary visual agnosia may not be able to recognize or point to various parts of the body (autotopagnosia). Symptoms may also include loss of the ability to distinguish left from right.[1]
Last updated: 4/22/2011
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Cause Cause


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Primary visual agnosia occurs as a result of damage to the brain. Symptoms develop due to the inability to retrieve information from those damaged areas that are associated with visual memory. Lesions may occur as a result of traumatic brain injury, stroke, tumor, or overexposure to dangerous environmental toxins (e.g., carbon monoxide poisoning). In some cases, the cause of the brain damage may not be known. Symptoms may vary, according to the area of the brain that is affected.

Visual agnosia may also occur in association with other underlying disorders (secondary visual agnosia) such as Alzheimer's disease, agenesis of the corpus callosum, MELAS, and other diseases that result in progressive dementia. Disorders that may precede the development of primary visual agnosia (and may be useful in identifying an underlying cause of some forms of this disorder) include Alzheimer's disease, Pick's disease, and a rare disorder called Balint's syndrome.[1]
Last updated: 4/22/2011

Diagnosis Diagnosis


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A variety of psychophysical tests can be conducted to pinpoint the nature of the visual process that is disrupted in an individual. Brain damage that causes visual agnosia may be identified through imaging techniques, including computed tomography (CT scan) and magnetic resonance imaging (MRI).[1]
Last updated: 4/22/2011

Research Research


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Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to Agnosia. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.

Organizations Organizations


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Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

  • Brain Foundation
    P O Box 579
    Crows Nest, NSW
    1585 Suite 21
    Regent House 37-43
    Alexander Street Crows Nest, NSW 2065
    Australia
    Telephone: 61 2 9437 5967
    Fax: 61 2 9437 5978
    E-mail: http://brainfoundation.org.au/contact
    Website: http://www.brainfoundation.org.au/

Organizations Providing General Support

  • American Stroke Association
    National Center
    7272 Greenville Avenue
    Dallas, TX 75231
    Telephone: 888-478-7653
    Website: http://www.strokeassociation.org/
Do you know of an organization? We want to hear from you.

Learn More Learn More


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These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The Merck Manuals Online Medical Library provides information on this condition for patients and caregivers. 
  • The National Institute of Neurological Disorders and Stroke (NINDS) collects and disseminates research information related to neurological disorders. Click on the link to view information on this topic.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Agnosia. Click on the link to view a sample search on this topic.

GARD Answers GARD Answers


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Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • Is there a known genetic cause for agnosia? See answer

  • I have a student who appears to have some of the symptoms of agnosia. He had the cord wrapped around the neck at birth. Most of what I've read about visual agnosia is that it happens when older patients have a stroke. Would it be possible for a child, such as this student, to have this condition? See answer


Have a question? Contact a GARD Information Specialist.

References References


  1. Agnosia, Primary Visual. NORD. 2009; http://www.rarediseases.org/search/rdbdetail_abstract.html?disname=Agnosia%2C%20Primary%20Visual. Accessed 4/22/2011.
  2. Agnosia Information Page. NINDS. October 2, 2007; http://www.ninds.nih.gov/disorders/agnosia/agnosia.htm. Accessed 4/22/2011.
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