Astereognosis

The first stage of cognition is familiarization with the environment through the senses - we perceive the world by looking at everything around us, listening to sounds, smelling, tasting, touching. Sensory cognition occurs through the sensation of certain features to the birth of a complete image. A complete or partial disorder of tactile perception, in which a person is unable to identify an object only by touch, without seeing it, is called astereognosis or tactile object agnosia. The patient retains the ability to perceive individual characteristic features of an object by touch, but cannot combine them into a complete image and determine what it is touching.

Causes astereognosis

This pathology is manifested by the loss of the ability to analyze and integrate into a single tactile image skin-kinesthetic signals that, when touching an object, enter the cortex of the parietal region of the brain. A distinction is made between true (primary) astereognosis, in which the sensory basis of tactile perception is preserved, but synthesis is impaired, and false (secondary), which occurs against the background of changes in tactile and/or muscular-articular sensitivity in the hand.

The cause is organic damage to certain areas of the cerebral cortex: the superior parietal lobule behind the postcentral gyrus (area 5 according to Brodmann), the upper parts of the parietal lobe, limited by the postcentral gyrus and occipital lobe (area 7), and the supramarginal gyrus of the dominant hemisphere (area 40).

Potential risk factors for the development of pathological changes in the cerebral cortex include: craniocerebral trauma (usually closed, such as contusions) and their consequences - hematomas, inflammatory processes, areas of ischemia; diseases - acute and chronic cerebrovascular diseases, encephalitis of any etiology, neoplasms, atrophic processes in Alzheimer's disease, Parkinson's disease, Pick's disease, Huntington's chorea, Schilder's leukoencephalitis. [ 1 ], [ 2 ], [ 3 ]

Pathogenesis

The pathogenesis of any type of disorder of gnostic functions comes down to the disruption of transmission of nerve impulses from the periphery to the brain. Three groups of associative fields in the cerebral cortex are distinguished, which decipher sensations (in our case - tactile) and ensure their recognition.

Primary receptors receive skin-kinesthetic impulses directly from peripheral receptors. Secondary receptors, located in the parietal areas of the cerebral cortex, should analyze the incoming information in a healthy organism, summarize it and transmit it to the third level, where it is synthesized into a complete image. However, due to pathological changes in the above-mentioned areas of the cerebral cortex, the function of secondary fields is disrupted, analysis and generalization of information does not occur, impulse transmission is interrupted and a tactile image is not formed. When the patient opens his eyes, he easily recognizes the object. [ 4 ]

Agnosia or sensitivity disorders of various kinds can develop with many pathologies, their statistics are unknown. In addition, astereognosis or tactile object agnosia can go unnoticed for a long time, since it does not cause significant disruptions to everyday life. Astereognosis is almost never found in children, since the pathologies that cause it are typical for adults and even the elderly.

Symptoms astereognosis

Astereognosis is manifested in the failure to recognize various three-dimensional objects when palpating them with one or both hands with the eyes closed. Do we often do this? Apparently not. So the pathology may remain unrecognized for a long time, if not a lifetime.

For example, if an organic defect is localized in Brodmann's field 5 (in the superior parietal lobe, located behind the postcentral gyrus), then a person can clearly recognize hardness, relief, temperature and other properties, but cannot analyze them, synthesize them into a single object and determine what he is touching with his hands. Such a pathology can only be detected by chance.

However, if the defect is localized in field 7 (the upper parts of the parietal lobe, limited by the postcentral gyrus and the occipital region), then astereognosis may be accompanied by autometamorphopsia (body scheme disorder), the patient may confuse the sides of the body - left with right, not be aware of the presence of any disease or defect (anosognosia). [ 5 ], [ 6 ]

If the organic pathology is located in field 40 (marginal gyrus), then the motor analyzer of complex acquired skills may be simultaneously impaired, when previously coordinated, habitual hand movements become out of sync and chaotic (kinesthetic apraxia), or aphasia may be present, manifested by difficulties in articulation, dyslexia, dysgraphia, incomprehension of other people's speech, and a general decrease in speech production.

The last two localizations suggest an earlier appeal for medical help, although the patient usually shows the first signs of concomitant disorders.

Forms

The main types are distinguished by origin. True astereognosis, in which only the integration of all correctly perceived properties of an object in tactile contact into a single image is impaired (after all, peripheral sensitivity is preserved). This form is also called primary astereognosis. The patient with closed eyes correctly names the properties of an object, since he can convey elementary sensations by assessing the smoothness, linear dimensions, and quality of the material by touch, but the image does not form, difficulties arise in determining the volume and it is impossible to name the functional purpose of the object. [ 7 ]

False astereognosis or secondary astereognosis occurs when the conduction of deep or tactile sensitivity impulses is disrupted. A patient with closed eyes cannot understand what his fingers are feeling, or whether they feel at all.

There is also bilateral tactile agnosia, which occurs with organic defects of the middle and upper sections of the posterior central gyrus. And also unilateral - it manifests itself when feeling objects with the hand on the side opposite to the brain lesion.

Separately, as well as in combination with the subject, non-recognition of the texture of the object may be observed.

Types of tactile agnosia also include a disorder called dermolexia, when the patient cannot recognize numbers, letters or drawn figures “written” on the skin. [ 8 ]

Complications and consequences

Astereognosis itself does not particularly complicate the life of a person suffering from this pathology. To identify an object, we usually use vision, and the patient is fine with this. At the same time, the presence of this pathology indicates that there is an organic lesion of the cerebral cortex, and it is desirable to find out its cause, since it can have dangerous consequences and complications, even incompatible with life.

Diagnostics astereognosis

The examination begins with an interview with the patient to establish the nature of the complaints, the onset of the disease, the events preceding it - injury, illnesses. The presence of astereognosis is confirmed by testing: the patient feels objects, blindfolded, and at the same time answers the doctor's questions about their properties, trying to integrate the tactile image and identify the object. Seguin boards are good for diagnostics.

The main purpose of the examination is to establish the cause of the brain damage. For this purpose, the patient takes the tests prescribed by the doctor, modern instrumental diagnostics are used - magnetic resonance and / or computed tomography of the brain, which allows visualizing soft tissues, blood vessels, bone structures, identifying foci of ischemia or inflammation, tumors. Consultations with specialists of different profiles, including a psychiatrist and psychotherapist, can be prescribed. [ 9 ]

Differential diagnosis

Differential diagnostics are carried out with mental disorders, other agnosias, in particular, tactile perception disorders.

Treatment astereognosis

The patient may be prescribed conservative therapy or recommended neurosurgery to remove a tumor or hematoma, the consequences of a traumatic brain injury. In any case, drug treatment is carried out. There is no special medicine for astereognosis. The treatment regimen usually includes:

1. Nootropics or neurometabolic stimulants are the main drugs for restoring brain functions in patients with organic syndrome, improving general brain activity, neurotransmission, strength of cell membranes and vessels, energy supply, cellular respiration, resulting in a regenerating effect on brain tissue. As a result, higher synthetic functions are significantly improved or completely restored. The first representative of this class of drugs, piracetam and its derivatives (racetams), are still used. γ-aminobutyric acid and its complexes (aminalon, neurobutal, phenibut), polypeptides (cerebrolysin, cerebromin), amino acids (glycine), ginkgo biloba-based drugs, cerebral circulation disorder correctors (cinnarizine, vinpocetine), complex drugs: olatropil (γ-aminobutyric acid + piracetam), omaron (piracetam + cinnarizine) and many other drugs that exhibit nootropic activity can be prescribed. The choice of drug is made by the doctor depending on the pathology that caused astereognosis. Some nootropic drugs, they are called true, have the only ability to improve cognitive functions, directly affecting nerve cells. Others, in addition, exhibit other pharmacological activity - they calm, relieve cramps, help you fall asleep, lower blood pressure, thin the blood, eliminate the effects of hypoxia. Sometimes the nootropic effect is achieved as a secondary effect due to improved microcirculation, antithrombotic, antihypoxic or relaxing effect. The therapeutic effect of nootropic drugs is achieved gradually and becomes obvious after taking them for several weeks. They are taken for a long time. They are well suited for this, since they are not toxic and do not cause addiction. Taking nootropics is not accompanied by the development of speech motor excitation, they are well combined with many pharmacological agents of other groups. Only in rare cases during the course of taking may some anxiety and / or sleep disorders be observed. In addition, individual intolerance is not excluded.
2. Acetylcholinesterase inhibitors, such as ipidacrine, are also used. The drug improves the transmission of nerve impulses from the periphery to the brain. Patients with Alzheimer's or Parkinson's disease may be prescribed drugs of this group, rivastigmine or donepezil. Anticholinesterase drugs are usually used for no more than two weeks. They can cause dyspeptic symptoms, slowing of the heart rate and a decrease in body temperature. They are not prescribed to pregnant and lactating women, people with hyperkinesis, bronchial asthma and vestibular disorders.
3. If astereognosis is a consequence of encephalitis, the patient is prescribed a course of antibiotic therapy, antiparasitic or antiviral drugs, depending on the origin of the disease.
4. Any patient can be prescribed vitamin therapy - B vitamins, ascorbic acid, and tocopherol improve brain activity.

Depending on the diagnosis, other medications and treatments may be used.

Patients may be prescribed psychotherapy, speech therapy (for speech disorders), therapeutic exercises and other rehabilitation courses.

Prevention

In order to prevent the development of this pathology, it is necessary to follow the most general preventive measures: a healthy lifestyle to maintain good immunity, adequate behavior and good physical shape to prevent injuries, compliance with the rules of sanitation and hygiene to prevent infections. If symptoms of agnosia appear, do not delay a visit to the doctor.

Forecast

The outcome of treatment depends on many factors: the severity of the underlying pathology, the timeliness of the measures taken, and the age of the patient.

Young patients after traumatic brain injuries and encephalitis can fully recover, although the treatment and rehabilitation process usually takes a long time, a year or more.

In surgical pathologies, much depends on the successful completion of the operation.

The most unfavorable prognosis occurs when astereognosis is caused by degenerative processes in the brain. In such cases, therapy only halts the progression of the disease.