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Agnosia
Last reviewed: 23.04.2024
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Agnosia is the inability to identify an object using one or more sensory organs. Diagnosis is based on clinical symptoms, often using neuropsychological research and using brain imaging techniques (CT, MRI) to identify the cause. The prognosis depends on the nature and extent of the lesion, as well as the age of the patient. Specific treatment does not exist, but occupational therapy can help patients achieve status compensation.
[Types of agnosia
Some variants of brain damage cause different forms of agnosia, which can be associated with any kind of sensitivity. As a rule, only one type of sensitivity is affected; The ability to identify objects through other types of sensitivity does not suffer. An example is the inability to identify objects from a perceived sound, such as a phone call (auditory agnosia), taste (taste agnosia), smell (olfactory agnosia), touch (tactile, tactile agnosia or asteroognosis) or visual signal (visual agnosia).
Other forms of agnosia include very specific and complex processes within one type of sensitivity. For example, prosopagnosia is the inability to identify known individuals, including close friends or, in other cases, to single out individual objects among a class of objects, despite the ability to identify facial features and objects with certain generic characteristics.
Anosognosia often accompanies damage to the right subdominant parietal lobe. The patient denies his illness, insisting that there is nothing abnormal, even when one side of the body is completely paralyzed. When demonstrating a paralyzed part of the body, the patient can deny that it belongs to him, possibly a violation of the body's scheme - autopapognosia. Anosognosia is often combined with the negation of paralyzed or insensitive parts of the body ("loss of half of the trunk" or anosognosia of hemiplegia) or space ("loss of half of space", one-sided spatial agnosia or ignoring half of space), which is characteristic of left-sided lesions.
Combined lesions of the occipital and temporal lobes of the brain can cause an inability to recognize familiar places - a violation of topographic orientation (agnosia of the surrounding environment), visual disturbances (visual agnosia) or color blindness (achromatopsia). Right-sided temporal lesions can cause inability to interpret sounds (auditory agnosia) or impaired perception of music (amusia).
How is agnosia recognized?
The patient is asked to identify common objects using different senses (vision, touch or others). If there is a suspicion of negating half of the space, the patient is asked to identify paralyzed parts of the body or objects in the corresponding half of the space. Neuropsychological research can help to identify more complex variants of agnosia. It is necessary to carry out tests to differentiate the disturbances of sensation and understanding in order to distinguish such defects from agnosia.
Visualization of the brain (CT or MRI using angiography and without) is necessary to characterize central lesions (for example, infarction, hemorrhage, volumetric intracranial process), and also to detect bark atrophy characteristic of degenerative diseases. Physical examination usually allows to identify primary disturbances of certain types of sensitivity, which can make it difficult to further assess the patient's condition.
Treatment of agnosia
Agnosia has no specific treatment. Rehabilitation with the assistance of a speech therapist or an occupational therapist can help the patient achieve compensation for the disease. The degree of recovery depends on the size and location of lesions, the degree of damage and age of the patient. Recovery mostly occurs within the first three months, but generally lasts up to one year.