Visual agnosia

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at October 15, 2016
StartDiseasesVisual agnosia

Visual agnosia affects a small number of the general population. The condition involves a person's inability to recognize or identify objects visually, and it results from brain damage. Objects are visible to people with visual agnosia, but recognizing the objects is nearly impossible. 

Contents

Definition & Facts

People who suffer from this health condition do not have vision problems like blindness nor are they unintelligent. These people know precisely what specific objects are, but the condition removes the ability to identify them based on their vision.

Cognitive abilities are not affected in other ways. Those who suffer from this type of agnosia are typically diagnosed after a stroke, traumatic brain injury, or other conditions such as brain tumors or poisoning that can cause brain damage.

There’s more than one form of agnosia such as auditory agnosia and tactile agnosia, but visual agnosia is the most common form. Visual agnosia was first described in 1888. Apperceptive visual agnosia involves the inability to perceive shapes, whereas associative visual agnosia involves the inability to associate one's visual perceptions of objects with stored memories. Prosopagnosia involves the inability to recognize faces.

Symptoms & Complaints

There is one primary symptom associated with visual agnosia, which is the inability to recognize objects or places familiar in a person’s mind. A person may be in good health otherwise yet be unable to clearly identify an object.

For example, a person with visual agnosia might see a cookie sitting on a table in the same room, but may be unable to identify the cookie by name due to the inability to recognize it. They may not be able to identify the cookie out of a series of objects. They may not be able to associate the cookie with another cookie. Yet, this person can be aware of cookies and what they are.

This person may need to pick up the cookie, hold it, and smell or even taste it to recognize that it is a cookie. When a person begins to complain that objects are only recognizable by smell, touch, taste or even sound, it’s the most obvious symptom of this condition.

Causes

People who suffer from visual agnosia have suffered a form of brain damage, which can be the result of a number of different causes:

Carbon monoxide can cause agnosia, particularly apperceptive visual agnosia in which a person is unable to recognize or reproduce shapes.

Brain damage can affect the occipital lobe which is where the visual cortex is located. Fusiform face area is part of the temporal lobe and is linked to facial recognition.

Diagnosis & Tests

Diagnosing visual agnosia will call for ruling out all other cognitive disabilities such as memory loss and aphasia as well as ruling out any problems with visual acuity and perception. The clinician will try to determine that the failure to identify or recognize is limited to one modality: in this case, vision.

It involves object identification tests as well as neuroimaging scans. The former involves cognitive tests to determine if a person can identify an object visually. Warrington Memory Test for faces and the Benton Face Recognition are two such tests that can diagnose prosopagnosia specifically. Neuroimaging scans involve diagnosing underlying brain injury and can include magnetic resonance imaging (MRI) scans and computed tomography (CT) scans.

Some doctors prefer to use other imaging techniques to make a diagnosis, but the vast majority choose one of these commonly used methods. This type of testing helps doctors locate the injury to the brain to determine whether or not it is the cause of a person’s sudden inability to perform basic functions in relation to recognition. 

Treatment & Therapy

Treatment for visual agnosia is not always straightforward. How an individual responds to treatment varies based on a myriad of factors. This could include the severity of the injury that caused the agnosia, the patient’s attitude, and the patient’s ability to relearn basic functions.

Most people who do suffer this type of visual agnosia are treated through various forms of physical therapy, speech therapy, or occupational therapy with an aim towards helping patients relearn the basic functions and objects necessary to allow a person to get through the basics of day-to-day life without as much struggle. Other patients are taught coping skills that teach the ability to get through the day-to-day frustrations patients face as a result of this diagnosis. 

Learning how to rely on other senses can be a component of therapy as can learning various alternate contextual cues to identify people and objects.

Prevention & Prophylaxis

Preventing brain injury can reduce the likelihood of visual agnosia but is not always an option for most patients. Taking the time to allow for basic precautions such as wearing a helmet when on a bike or motorcycle and protecting the head from injury are prudent regardless.

Certain lifestyle choices such as regular exercise and a healthy diet can reduce the risk of stroke and brain tumors which can cause visual agnosia, and using common sense and detection methods to prevent toxic poisoning from chemicals such as carbon monoxide are also helpful. The only way to prevent the likelihood of this condition is to protect the brain from trauma, illness, or injury.