BAROGNOSIA: ORIGIN, CONCEPT, TEST, RELATED DISORDERS - ANATOMY AND PHYSIOLOGY - 2024

The barognosia or barognosis is a medical term used to describe the ability of humans to distinguish the difference in weight between two objects, using only the sense of touch. Even objects can be the same shape and size but of different weight.

If the individual is able to recognize which is heavier and which is the lightest, it means that his barognosia is intact. The evaluation of barognosia is one of the tests that are part of the exploration of deep sensitivity.

Representative image of weight discrimination through the signals emitted to the brain through touch. (Barognosia). Source: publicdomainvectors.org/. Edited image

Barognosia, as well as other properties such as baresthesia, are possible thanks to the strategic presence, distribution and function of the Pacini corpuscles. These are located in the dermis (deepest layer of the skin), in the subcutaneous tissue, as well as at the level of the bone with the greatest predilection in the periosteum.

Pacini corpuscles are receptors that allow the capture and processing of information on two important variables such as: weight and pressure.

Fibers emerge from the receptors through which nerve impulses travel, passing through peripheral nerves, spinal cord, medulla oblongata, thalamus and parietal cortex of the CNS, where nerve impulses are finally interpreted.

Patients who lose the ability to discriminate between different weights are said to have "embraognosia" or "baroagnosia."

Origin and concept

Baro comes from the Greek baros which means weight, gnosia, knowledge or perception and the ending (ia) means quality. The word barognosia then refers to the ability to know or perceive the weight of objects.

If this term is given the prefix (a) that means (without), it would remain as encompassing, in this case the meaning changes to the inability to know or perceive the weight of the objects. The letter (a) can also be placed before gnosia, leaving it as baroagnosia. It means the same as embraognosia.

Barognosia evaluation test

The analyzes that evaluate the superficial and deep sensitivity require great concentration, both from the patient and the specialist. To perform the test it is necessary that the patient is relaxed, willing to collaborate. On the other hand, a calm and confidence-inspiring environment should be sought, since the test requires the patient to have their eyes covered.

The dynamics of the test will be explained to the patient, as well as the importance of the test and the correct way to answer the questions, since the answers must be clear and precise. It is a great mistake to suggest an answer to the patient, since he must give it spontaneously. If the response is induced, the test loses validity.

The test can be performed with the patient sitting or lying down, but preferably sitting. The patient's eyes will be covered and objects will then be delivered to their hands.

It can be done with both hands at the same time and indicate which of the two hands contains the heaviest object, or it can be done with one hand, placing the object, removing it and then placing the other. The patient is asked to indicate which of the two was heavier.

The patient must respond, in either of the two modalities.

The objects will be changed and the experience will be repeated, and the same question will be asked. The most commonly used objects are weights commonly used in the gym. The weights can be of different sizes or even the same size and shape but of different weights.

Balls can also be used. For example, in one hand you place a tennis ball and in the other a ball of the same size, but it is made of sponge or foam.

The results obtained are recorded.

Interpretation

If the patient is correct, it is said that he presents the capacity for barognosia intact. This from the medical point of view means that the receptors, as well as the afferent pathways through which impulses travel and the brain integration centers where impulses are interpreted, are in perfect condition.

If, on the other hand, the patient is unable to discriminate between the different weights, the patient is said to have embraognosia.

The most important thing in the neurological examination evaluation is not only to detect the deficiency in the ability to perceive and discriminate between the different weights, but to diagnose where the cause of the problem lies.

It is important to determine at what level the damage exists. The possibilities are: at the level of receptors due to burns or tendon tears, at the level of a peripheral nerve, in the medullary canals or in the thalamus or parietal cortex.

Knowing the cause will help in choosing a more effective therapy.

Related disorders

Abarognosia

It is the inability of the patient to discriminate between different weights or to perceive the weight of objects. This anomaly is generally due to damage that occurred at the level of the parietal lobe and is expressed on the opposite side where the injury is recorded.

Syndromes that can lead to embraognosia

Lesions in the parietal cortex

Since the parietal lobe is the anatomical site responsible for conscious sensation, it is reasonable to think that deep sensation disturbances are due to injury at this level. This is where stereognosia, graphesia and barognosia, among others, enter.

Guillain Barre syndrome

Guillain-Barré syndrome is an autoimmune disease that can develop after suffering from a viral or bacterial infection. This syndrome is characterized by the appearance of a symmetrical weakness that progresses rapidly. It is possible that it may affect the respiratory bulbar muscles.

On the other hand, the syndrome can present with loss of tendon reflexes and also with mild or absent sensory signs. Among the latter, the loss or decrease of barognosia could be mentioned, along with other sensitive capacities, such as: baresthesia, stereoognosia and palesthesia.

Psychogenic disorders

On some occasions, psychiatric disorders can manifest alterations at the sensory level, characterized by complex abnormalities that make their interpretation difficult.

References

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