Agnosia – Definition, Types, Symptoms, Causes, Diagnosis and Treatments

Imagine for a moment that you have had a seizure that leaves you unconscious for a short time and when you finally wake up, everything around you seems the same, but different. How is that, you ask? Imagine that you are looking at a big box on the wall, you can see its dimensions but cannot remember what it is, someone sitting next to your bed calls it television, but it still seems so strange, then you think, who is this person sitting next to you? side? She says she’s your sister, but you don’t recognize her. This scenario may seem like something out of a scary movie, but for people suffering from agnosia this is the reality.

What is agnosia?

It is a rare neurological disorder that causes the loss of the ability to recognize any familiar person , object, and sound or the ability to understand the meaning of any object or difficulty in processing sensory information, such as touch, sound, and even light. in the presence of intact senses.

Brain lesions develop due to neurological ailments or brain lesions mainly in the occipital, temporal or parietal lobe of the ventral stem of the brain. In addition to neurological disease, agnosia can also be the result of stroke, severe head injury, developmental disorders , or dementia .

Agnosia only affects a single modality, such as vision or hearing. More recently, a top-down disruption is considered to cause impaired handling of perceptual information.

Types of Agnosia

There are different types of agnosia depending on the perception of sight, hearing or the tactile senses. The types are as follows:

Visual

It affects the ability to process incoming visual information and understand its meaning. There are two main types of visual agnosia: apperceptive and associative.

Agnosia aperceptiva visual

People with visual apperceptive agnosia cannot properly process what they see and distinguish between different visual stimuli, even the same object shown from different angles may not appear as the same object to them.

Associative visual agnosia

People with visual associative agnosia cannot match the object they see with the information stored in their memory , they can draw an object (which means that they process the information from visual stimuli correctly), but they cannot tell what it is.

Prosopagnosia

It is the inability to recognize faces, it is caused by problems with the fusiform face area, a specific region of the brain that recognizes faces. This often occurs in patients with Alzheimer’s disease and autism.

Acromatopsia

It refers to the inability to recognize a color, while it can be perceived or distinguished.

Alexia pura

It is the inability to recognize words visually, it is not possible to read with pure alexia. You can usually still speak and write without difficulty.

Akinetopsia

Also known as cerebral akinetopsia or motion blindness, it is an extremely rare neuropsychological disorder in which a patient cannot perceive movement in his visual field, despite being able to see stationary objects without problems.

auditory

Auditory agnostics do not attribute values ​​to verbal or non-verbal sounds, people with pure word deafness have intact hearing but cannot understand the spoken word, usually the result of bilateral trauma to the temporal cortico-subcortical regions of the brain. . Auditory nonverbal agnostics do not associate sounds with specific objects or events, such as a dog barking or a door slamming. In these patients, the lesions tend to be located in the right hemisphere.

Fonoagnosia

It is the inability to recognize and identify familiar voices. It develops when the brain suffers damage to a certain part of the sound association region, this region is located in the right half of the brain, although you can understand the words that others speak if you have this condition.

Tactile

Also called astereognosis, it is often difficult to recognize as we rarely identify objects solely by sensation. Information about the object, including its weight, size and texture, is not given any value, lesions in the somatosensory cortex are believed to be responsible for the condition.

Autotopagnosia

It is associated with the inability to orient parts of the body, and is caused by a lesion in the parietal part of posterior thalmic radiation.

Causes of agnosia

It occurs when the brain suffers from any type of trauma or damage to certain signaling pathways that deal with sensory processing, information storage and knowledge, it also integrates memory with recognition and perception.

Brain injuries to the parietal, occipital, or temporal lobes of the brain due to sudden head trauma, stroke, or encephalitis, etc. they result in agnosia. Other conditions that lead to it include deterioration or damage of the lobes of the brain, carbon monoxide poisoning, dementia , tumors, anoxia, abscesses or pockets of pus, developmental disorders, inherited or acquired brain infection, sudden recovery from blindness or disorders progressive neurodegeneratives such as Alzheimer’s disease .

Risk factors for agnosia

Associated risk factors include the following:

• The Caucasian race is more prone.
• It affects women.
• Advanced age.
• Any kind of serious head injury.
• The habit of smoking.
• Obesity.
• If an individual suffers from a vascular disease such as coronary disease, hypercholesterolemia, atherosclerosis, diabetes, hypertension, etc.

What are the symptoms of agnosia?

Symptoms generally vary depending on the position and parts of the different sensory lobes of the brain that are damaged:

• When the occipital lobe is damaged:  This lobe takes care of the normal perception of vision processing, when it is damaged or affected by a neurological disease, a visual agnosia occurs in which the patient presents symptoms of loss of ability to identify geometric shapes, features, or colors of any common object or cannot recognize familiar faces or buildings, rooms, or places, but visual perception is not affected at all.
• When the temporal lobe is damaged: Damage to this lobe leads to auditory agnosia as the lobe functions to detect sound. In this case, symptoms would include people who can hear sound but cannot recognize the familiar voice, sounds, or spoken language.
• When the parietal lobe is damaged: This lobe works to detect sensory information related to touch, pain, or temperature. When this lobe is damaged, a tactile agnosia occurs in which people do not perceive the sensation of pain or have difficulty identifying any familiar object by touching alone; however, this patient can recognize the object when he sees it.

How is agnosia diagnosed?

To diagnose an individual with agnosia, it must be seen that the patient has intact language skills , response to stimuli and intelligence, but suffers a loss of sensation. Furthermore, the patient should only experience sensory deficits in only one of the sensory modalities.

• A doctor’s evaluation in which a doctor will ask the patient to recognize and identify common things around the house by perception of sight, hearing, or touch.
• Are performed are standardized tests of brain function including neuropsychological testing to diagnose more accurately agnosia.
• The imaging , such as MRI, CT scans, are performed in the presence or absence of angiographic protocols to identify hemorrhage, infarction, tumor mass, or atrophy lesions detected.
• The examination of the fundus , examination of cerebrospinal fluid and test electroencephalogram also show an abnormal result.

Other differential diagnostic tests can be performed based on the similar symptoms of some diseases such as memory disorders, mental retardation, etc.

What is the treatment for agnosia?

Agnosia is an extremely rare condition, and treatment is partially focused on remedying the underlying causes – some neurological abnormalities can be remedied with brain surgery, while agnosia from a stroke can be permanent.

Occupational and speech therapy can help improve symptoms and lifestyle changes, and supportive care can help people with agnosia learn to cope with their symptoms. Doctors may recommend that they obtain sensory information through other senses, that others explain objects verbally, or establish organizational strategies to cope with their symptoms, but there is no clear cure for agnosia at this time.

There are several methods that can be used to help the individual recognize impairment in perception or recognition that they may have, a patient may be presented with a stimulus for the disability modality only to help increase their awareness of their deficit.

Once the individual recognizes his perceptual or recognition deficit, a form of treatment can be recommended, there are various forms of treatment, such as compensatory strategies with alternative modalities, verbal strategies, alternative guidelines and organizational strategies.

Verbal strategies

The use of verbal descriptions can be useful for people with certain types of agnosia, for example, those who suffer from prosopagnosia may find it a helpful strategy to listen to a description of their friend or family member and recognize them based on this description that they through visual cues.

Alternative signals

Alternative cues can be particularly useful for an individual with environmental agnosia or prosopagnosia, for an individual with environmental agnosia they can include colored cues or tactile markers to symbolize a new room or to remember an area, you can use alternative cues such as a scar on the face of an individual or crooked teeth to recognize the individual. Hair color and length can also be helpful cues.

Organizational strategies

Organizational strategies can be extremely helpful for an individual with visual agnosia. For example, organizing clothing according to different hangers provides tactile clues for the individual, making it easier to identify certain forms of clothing rather than relying solely on visual cues.

Alternative medicine

These strategies cause the use of an unaffected modality. For example, people with visual agnosia can use tactile information to replace visual information. Alternatively, an individual with prosopagnosia can use auditory information to replace visual information. For example, you can wait for someone to speak, and you will generally recognize the individual from their speech.

Can agnosia be prevented?

As such, there are no preventive measures for agnosia, however it can be restricted to a certain level through early detection of the disease associated with appropriate medical treatments and related therapies. Also, the affected person can follow the diet items mentioned below to avoid further complications:

More consumption of fresh fruits and vegetables, dairy products, soybeans, walnut oil, fatty foods, seafood and sweets. Limit your consumption of fish and meat.

Complications that can occur from agnosia

Related probable complications are mentioned in the following points:

• Mild to severe hallucinations .
• Spatial perception disorders.