Brief description
- What is agnosia? In agnosia, the affected person can no longer recognize sensory stimuli, although perception is preserved, the sensory organ is intact, and attention and intellectual abilities are not impaired.
- Causes: damage to certain lobes of the brain, e.g., due to stroke, brain tumor, brain abscess, or diseases in which successive brain tissue dies (as in Alzheimer’s disease).
- Symptoms: Depending on the type of agnosia, e.g., inability to identify what is seen (visual agnosia) or to recognize sounds (auditory agnosia).
Agnosia: Definition
In agnosia, the affected person can no longer recognize sensory stimuli, although perception itself is preserved. Thus, the sensory organs function correctly, and there is also no mental impairment (such as dementia). Instead, agnosia is based on a disturbance in information processing, for example as a result of a stroke. It is relatively rare.
Forms of agnosia
- visual agnosia with special forms like prosopagnosia, color agnosia
- tactile agnosia
- spatial agnosia
- olfactory agnosia
- auditory agnosia
- autotopagnosia
- Anosognosia
Agnosia: causes and possible diseases
Agnosia results from damage to specific lobes of the brain: Occipital, Parietal or Temporal lobes – all part of the cerebrum. For example, visual agnosia is caused by damage to the occipital lobe – the rearmost part of the cerebrum whose tasks include visual information processing. In contrast, acoustic agnosia is due to damage in the area of the posterior temporal lobes (temporal lobe), which is indispensable for hearing. Autotopagnosia results from injury to the parietal lobe.
Possible causes of brain damage include:
- Head injury
- Stroke
- Brain tumor
- Brain abscess
- Diseases with progressive decay of brain tissue (such as Alzheimer’s disease)
Agnosia: symptoms
Visual agnosia
In the case of visual or optical agnosia (also called soul blindness), the affected person is unable to link optical perceptions with optical memories. This means that the patient can see an object (object, face, etc.) but cannot recognize it. However, if he can hear the object or attack it, for example, it is possible that he will recognize it.
Visual agnosia is divided into different subtypes such as:
- Prosopagnosia (face blindness): Affected individuals cannot recognize and distinguish familiar faces (of family members, friends, etc.). Instead, they have to rely on other features (voice, clothing, gestures, etc.) to identify individuals.
- associative agnosia: Here the affected person recognizes the shape and form of an object (such as a hammer), but does not know its meaning. That is, he does not know what the hammer is for.
- Color agnosia: Affected persons can perceive colors, but cannot recognize and name them. This form of agnosia must not be confused with color blindness – a condition in which affected individuals cannot perceive individual or all colors.
Tactile agnosia
Tactile agnosia is also called stereoagnosia, astereognosia or tactile blindness. It is understood as the inability to identify something only by palpation or touch (without visual control), although the sense of touch functions normally. Thus, the affected person cannot recognize and name objects and materials by touching and palpating alone.
Spatial agnosia
In this form of recognition disorder, the affected person cannot orient himself in space or on his own body.
Olfactory agnosia
Auditory agnosia
Auditory agnosia is also called deafness of the soul. It is characterized by the fact that the affected person, despite intact hearing, cannot identify sounds or tones or recognize them in their context. For example, if a telephone rings in the next room, he hears it but cannot recognize it as a telephone ring. Or he can hear individual tones but cannot recognize them in their context as melodies.
Autotopagnosia
In autotopagnosia, the affected person cannot locate and name his own body parts and cannot correctly localize skin stimuli on his own body, although surface sensitivity is intact.
Anosognosia
Agnosia: When should you see a doctor?
If agnosia occurs anew, it is a warning signal for a disturbed brain function. If a stroke is the cause, it is an emergency that must be treated by a doctor immediately!
Agnosia: What does the doctor do?
To diagnose agnosia, the doctor will perform various tests and examinations depending on the sensory area affected. For example, if visual agnosia is suspected, he will ask the patient to name various objects (such as a pen, book, etc.) or demonstrate their use. In order to detect prosopagnosia, the patient is presented with photos of relatives or well-known personalities for naming.
In the run-up to such tests, the doctor must ensure that the patient has understood his instructions and that there is no additional aphasia (speech disorder) – as is often the case, for example, with autotopagnosia. If the patient has difficulty expressing himself and understanding what someone is saying, this can falsify the test result.
If agnosia is actually present, its cause must be clarified. Imaging of the brain, for example by means of computer tomography (CT) or magnetic resonance imaging (MRI), can help. In this way, for example, space-occupying processes such as a tumor or a brain hemorrhage can be identified as the cause of the brain damage and thus agnosia.
Treatment of agnosia
On the other hand, the treatment of agnosia aims to make it as easy as possible for patients to live everyday life with their impairment. Occupational therapists and speech therapists, for example, can show those affected ways to compensate for their deficits. For example, a patient with prosopagnosia (face blindness) trains to recognize people by features other than their face, such as hair color and hairstyle, voice or gait.
Agnosia: What you can do yourself
In any case, relatives can be a great support. It is best to discuss with the attending physician or therapist how they can effectively support the agnosic patient.
