Asteregnosis

The first step in cognition is acquaintance with the environment through the senses - we perceive the world, looking at everything around, listening to sounds, smelling, trying on the tongue, feeling. Sensory cognition occurs through the sensation of certain signs to the birth of a whole image. A complete or partial disorder of tactile perception, in which a person is not able to identify an object only by touch, without seeing it, is called astereognosis or tactile objective agnosia. The patient retains the ability to perceive to the touch certain characteristic features of the subject, but cannot combine them into a holistic image and determine what it concerns.

Causes of the asteroid diagnosis

This pathology is manifested by the loss of the ability to analyze and integrate skin-kinesthetic signals into the tactile image, which, when feeling the object, enter the cortex of the parietal region of the brain. There are 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 an organic lesion of some parts of the cerebral cortex: the superior parietal lobe behind the postcentral gyrus (Broadman field 5), the upper parietal lobe limited by the postcentral gyrus and occipital lobe (field 7), the supra marginal gyrus of the dominant hemisphere (field 40).

Probable risk factors for the appearance of pathological changes in the cerebral cortex include: traumatic brain injuries (usually closed, for example, bruises) and their consequences - hematomas, inflammatory processes, areas of ischemia; diseases - acute and chronic cerebrovascular diseases, encephalitis of any etiology, neoplasms, atrophic processes in diseases of Alzheimer's, Parkinson's, Peak, Goettington's chorea, Schilder's leukoencephalitis. [1],  [2], [3]

Pathogenesis

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

Primary take skin-kinesthetic impulses directly from peripheral receptors. Secondary, located in the parietal parts of the cerebral cortex, must in a healthy body analyze the information received, summarize and transfer it to the third level, where it is synthesized into a holistic image. However, due to pathological changes in the above areas of the cerebral cortex, the function of the secondary fields is impaired, analysis and generalization of information does not occur, impulse transmission is interrupted and the tactile image is not formed. When the patient opens his eyes, he easily recognizes the subject. [4]

Agnosia or sensitivity disorders of various kinds can develop with many pathologies, their statistics are not known. In addition, astereognosis or tactile subject agnosia can occur unnoticed for a long time, since it does not cause significant disturbances in the usual life. Astereognosis practically does not occur in children, since the pathologies that cause it are characteristic of adults and even older people.

Symptoms of the asteroid diagnosis

Astereognosis is manifested in the recognition of various volumetric objects when feeling them with one or both hands with eyes closed. How often do we do this? Apparently not. So the pathology for a long time, if not all life, may remain unrecognized.

For example, if the organic defect is localized in field 5 according to Broadman (in the upper parietal lobe located behind the postcentral gyrus), then a person can clearly identify hardness, bump, temperature and other properties, but analyze them, synthesize them into a solid object and determine that it touches his hands, can not. Such a pathology can be detected only by chance.

But, 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 autometamorphopsia (a disorder of the body scheme) may accompany astereognosis, the patient may confuse the sides of the body - the left to the right, not be aware of any either a disease or defect (anosognosia). [5], [6]

If organic pathology is located in field 40 (marginal gyrus), then the motor analyzer of complex acquired skills can be disturbed at the same time, when previously coordinated habitual hand movements mismatch and become chaotic (kinesthetic apraxia) or aphasia is present, manifested by difficulties in articulation, dyslexia, dysgraphia, and misunderstanding foreign speech and a general decrease in speech production.

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

Forms

The main species are distinguished by origin. True astereognosis, in which only the integration into a single image of all the properties of an object correctly perceived in tactile contact is violated (after all, peripheral sensitivity is preserved). This form is also called primary astereognosis. The patient with his eyes closed correctly calls the properties of the object, since he can convey elementary sensations, judging by touch the smoothness, linear dimensions, quality of the material, but the image does not add up, there are difficulties with determining the volume and the functional purpose of the object cannot be called. [7]

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

Two-way tactile agnosia is also distinguished, arising from organic defects in the middle and upper sections of the posterior central gyrus. And also one-sided - it manifests itself when palpating objects with the hand from the opposite side of the brain lesion.

Separately, as well as in combination with the subject, an unrecognition of the texture of the subject may be observed.

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

Complications and consequences

Astereognosis by itself does not particularly complicate the life of a person suffering from this pathology. To identify an object, we usually use sight, and with this the patient is all right. However, the presence of this pathology suggests 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 that are not even compatible with life.

Diagnostics of the asteroid diagnosis

The examination begins with an interview with the patient in order to establish the nature of the complaints, the onset of the disease, the events that preceded it - injury, illness. The presence of astereognosis is confirmed by testing: the patient feels the 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. It is good to use for the diagnosis of Segen boards.

The main purpose of the examination is to establish the causes of brain damage. For this purpose, the patient passes 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, revealing foci of ischemia or inflammation, and tumors. Consultations of specialists of various profiles, including a psychiatrist and a psychotherapist, can be scheduled. [9]

Differential diagnosis

Differential diagnosis is carried out with mental disorders, other agnosia , in particular, impaired tactile perception.

Treatment of the asteroid diagnosis

The patient may be prescribed conservative therapy or recommended a neurosurgical operation 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 cure for astereognosis. The treatment regimen, as a rule, includes:

1. Nootropics or neurometabolic stimulants are the main drugs for the restoration of brain functions in patients with organic syndrome, which improve cerebral activity, neurotransmission, strength of cell membranes and blood vessels, energy nutrition, cellular respiration, which results in a regenerative effect on brain tissue. As a result, fully superior synthetic functions are significantly improved or restored. The first representative of this class of drugs piracetam and its derivatives (racetams) is still used. Γ-aminobutyric acid and complexes based on it (aminalon, neurobutal, phenibut), polypeptides (cerebrolysin, cerebromin), amino acids (glycine), drugs based on gingko biloba, correctors of cerebral circulation disorders (cinnarizine, vinpocetine), complex preparations can be prescribed : olatropyl (γ-aminobutyric acid + piraktktam), lobarone (piracetam + cinnarizine) and many other drugs that show nootropic activity. The choice of the drug is carried out by the doctor depending on the pathology that caused astereognosis. Some nootropic drugs, called true, have the only ability to improve cognitive function by directly affecting nerve cells. Others, in addition, exhibit other pharmacological activity - they soothe, relieve cramps, help to fall asleep, lower blood pressure, thin the blood, and eliminate the effects of hypoxia. Sometimes the nootropic effect is achieved as a secondary effect due to the improvement of microcirculation, antithrombotic, antihypoxic or relaxing effect. The therapeutic effect of nootropic drugs is achieved gradually and becomes apparent after administration for several weeks. They are taken in a long course. They are well suited for this, as they are non-toxic and non-addictive. Reception of 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 reception process, some anxiety and / or sleep disturbances can 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 used, as a rule, no more than two weeks. They can cause dyspeptic symptoms, slow heart rate, and lower body temperature. They are not prescribed for 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 agents, depending on the origin of the disease.
4. Vitamin therapy can be prescribed to any patient - vitamins of group B, ascorbic acid, tocopherol improve brain activity.

Depending on the diagnosis, other drugs and treatment methods may be used.

Patients can be prescribed psychotherapy, classes with a speech therapist (for speech impairments), therapeutic exercises and other rehabilitation courses.

Prevention

In order to prevent the development of this pathology, the most general preventive measures must be observed: a healthy lifestyle to maintain good immunity, adequate behavior and good physical condition to prevent injuries, compliance with the rules of sanitation and hygiene for the prevention of infections. If symptoms of agnosia appear, do not delay the 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, the age of the patient.

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

With surgical pathologies, much depends on the successful operation.

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