The study of the olfactory organ

The olfactory function is considered important as a very effective method for diagnosis of PNS and CNS diseases. Many of the so-called essential anosmia or "parosmia" can be associated with certain organic diseases of intracranial structures, directly or indirectly related to the olfactory centers and their conductors. Often, the violation of the sense of smell, most often unilateral (for example, objective hypysmia or olfactory hallucinations), may appear among the earliest. Symptoms of intracranial disease. In terms of these provisions, the most valuable methods are the quantitative assessment of the olfactory function, which allows to judge the dynamics of the pathological condition and the effectiveness of treatment.

Anamnesis

Interrogation of the patient is carried out by a generally accepted scheme. Find out the signs of a change in smell: decrease, lack, heightened perception; Do not smells cause any associations or parasms (for example, the smell of a certain substance is perceived as the smell of another or unfamiliar substance). They also find out whether certain odors cause bronchospasm, palpitations, or any vegetative reactions. Clarify the timing of the appearance of violations of smell, their frequency or continuity, dynamics, a possible cause. Clarify the nature of the distant and proximal diseases, the degree of their severity, what signs accompanied these diseases (trauma, acute disorders of cerebral circulation, infectious diseases, poisoning), as well as the nature of the profession and the presence of occupational hazards (a pair of aggressive and toxic liquids, aerosols, smoke and dustiness of the premises).

All methods of olfactory research are divided into subjective, indirectly objective and objective. In everyday clinical practice, mainly subjective, based on the presentation of the test substance and its verbal report ("yes", "no", "yes, but I can not determine", is called a specific smell) are used basically.

Indirect-objective methods are based on the objective registration of so-called olfactory-vegetative reactions arising in response to the activation of projection systems of subcortical olfactory centers, their connections with stem structures and the hypothalamus. These changes may include changes in the heart rate, phase changes in the respiratory cycle, changes in the respiratory rate, olfactonucleolar reflexes, changes in the skin galvanic reaction, etc. When using these methods, indirect vegetative reactions realized by reflex pathway are used as indirect signs of functioning of the olfactory organ: "Receptor - olfactory bulb - subcortical olfactory centers." However, the presence of these reactions is not an absolute indicator of the normal functioning of the olfactory analyzer, since isolated disturbances occurring in the cortical zone of the third neutron, reflecting on the cortical function of the analyzer (perception, recognition, differentiation), may not influence the occurrence of vegetative reactions, below the level of damage (up to the third neutron).

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Objective methods are based on the registration of ECG and EEG

ECG is used in an animal experiment or during a neurosurgical operation, electrodes for recording biopotentials are placed on the olfactory zone of the GM cortex. With EEG electrodes are placed on the skin projections of the cortical zones of the olfactory analyzer located in the temporal-basal sections of the hypnocampus. However, the results of these studies should be treated with a certain degree of mistrust. Only when the ECOH potentials are synchronized with the olfactory stimulation and correspond to the form of typical oscillations, it can be asserted that the reflex path "receptor-cortex" functions. However, here again the question of the qualitative aspect of perception in the last instance remains open, for example, in the phenomenon of parosmia. Methods of ECG and EEG in evaluating the olfactory function have a certain value in a complex examination of patients with volumetric processes in the parieto-occipital-temporal region.

All methods of olfactory research are divided into qualitative and quantitative. A qualitative study is carried out with exposure to PV in close proximity to one, then to another nostril, during which the patient is offered to actively sniff and answer if he smells, and if so, what smell. To carry out this study, different authors have proposed sets of different PTs. The latter are used in the form of solutions placed in dark bottles with ground glass stoppers; on the bottles, numbers are put under which the corresponding PVs are indicated.

Thus, N.S. Blagoveshchenskaya (1990) reports on the set of W.Bornstein (1929) consisting of eight PVs arranged in the sequence from the weakest (No. 1) to the strongest (No. 8): washing (economic) soap, pink water, bitter water, tar, turpentine (these substances act mainly on the olfactory nerve), aqueous ammonia, acetic acid (act on the olfactory and trigeminal nerves), No. 8 chloroform (acting on the olfactory and glossopharyngeal nerves). The use of PV, which have a differentiated effect on the olfactory, trigeminal and lingopharyngeal nerves, has a definite diagnostic value, since with the olfactory nerve completely turned off the patient will still feel the "smells" acting on the V and IX nerves, but in a considerably weakened and distorted form.

At one time, the widespread odorimetric set of VI Voyachek. In the original version, this set consisted of four intensifying PV: 0.5% acetic acid solution (weak odor); pure ethanol (medium strength odor); tincture of valerian (strong odor); Ammonia aqueous solution (superstrong smell). Later, gasoline was added to this set (for persons of technical composition not familiar with the smell of valerian), and distilled water (control).

Gasoline, as the most volatile and most "penetrating" substance from the kit, VI Voyachek placed at number 6. In the absence of its perception, the sense of smell should be considered completely turned off.

The proper conduct of a qualitative olfactory study provides for a certain standardization of the experiment: the exclusion of the possibility of exposure to vapors in the unexplored half of the nose; the evaluation of PV on inspiration with a delay in breathing to exclude retrograde entry of PV in the second half of the nose during exhalation. Fortified in a cleft of a ray and a piece of filter paper with a size of 0.3x1 cm, moistened in a PV solution, bring to one nostril, covering the other, and ask the patient to breathe lightly, hold 3-4 breaths and determine what smell it feels. The results of the study are evaluated according to the 5-power system, depending on what smells the subject perceives:

• I degree - the subject identifies the weakest odor - No. 1;
• II degree - odors No. 2, 3, 4, 6 are perceived;
• III degree - perceived odors number 3, 4, 6;
• IV degree - smells are perceived № 4, 6;
• V degree - only smell 6 is perceived.

If none of the smells is perceived, then the diagnosis of anosmia is established.

With hyposmia, the mechanical cause is excluded. To do this, carefully examine the upper parts of the nasal cavity and, if necessary, treat them with a single lubrication of the mucous membrane solution of adrenaline chloride 1: 1000 (but not with an anesthetic!) And after 5 minutes a second examination is carried out. The appearance or improvement of the sense of smell after this procedure indicates the presence of a "mechanical" hyposmia.

A quantitative study of the olfactory function involves the determination of the threshold of perception and the threshold of recognition. For this, PV olfactive, trigeminal and mixed action are used. The principle of the technique is to dose the volume of air containing PV in a constant concentration, or in a gradual increase in the concentration of PV before obtaining the threshold of perception.

The method of quantitative olfactory research was called olfactometry, and the devices using which this method is realized are olfactometers. Classic examples of such devices can serve as olfactorms Zvaardemaker and Elsberg-Levy. H. Zwaardemaker at the end of the XIX century. Designed olfactometer, the principle of which is that the intake tube is located inside the cylinder, consisting entirely of a dense PV, on the outside covered with glass to prevent its sublimation into the environment. When the distal end of the tube extends beyond the cylinder, the paired vapors do not enter it.

When the tube is drawn into the cylinder, the amount of PV entering it depends on the distance of the tube to the end of the cylinder, that is, on the volume of the PV that can enter the tube. The disadvantage of the method is the uncontrolled active breath of the subject. This deficiency is deprived of the "impulse" (injector) method of Elsberg-Levy.

Elsberg's olfactometer is a hermetically sealed flask with a PV solution, into which two glass tubes (short and long) are introduced with rubber hoses at the proximal ends. The hose of the long tube is covered by a tap or clamp. The hose of the short tube branches into two tubes with olives on the ends. Through a long tube with the help of a syringe with a nozzle into the flask is introduced air, which displaces the vapors of PV through a short tube and olives. The principle of injected feed of PV was used in the olfactometer NS Melnikova and LB Dainiak (1959). In subsequent years, various more advanced designs of olfactometers with electromechanical and electronic dosing of PV were developed, with a complex system for conditioning a fragrant mixture with respect to temperature, humidity and vapor concentration at different modes of supply (intermittent, continuous, increasing, decreasing regimes).

A quantitative study of the olfactory function can be carried out in an extremely simple way with the aid of filter paper and an increasing concentration of any one substance, for example in the range 0.2-0.5% solution of ethyl alcohol, 0.2-0.9% acetic acid solution and etc. For this, a volume of air saturated with vapors from the solution can be dosed with an injection syringe (modification of the Elsberg-Levy method) by sucking this air into an injection syringe (10 or 20 ml) and then introducing it the air ha in the nasal cavity for 1, 2, 3 ml, etc. Until the appearance of a sense of smell. The latter method is simple, reliable and does not require practically any material costs. For the construction of such a device requires a flask, filled with a 1/3 solution of table vinegar; rubber stopper with two glass tubes, on which are put two rubber hoses with clamps; a syringe tightly inserted into one of the hoses, and a thin rubber catheter for insertion into the nose of air taken from a flask containing vinegar vapors. Before the final intake of air, two or three suction are carried out with a syringe to fill the outlet tube with vinegar vapors. The glass end of the sampling tube, inserted into the cavity of the bulb, should be placed well below the end of the second glass tube, but do not touch the liquid. The advantage of this method lies in the fact that during its carrying out the dosed forced introduction of PV into the nasal cavity at the required depth, up to the olfactory gap, which excludes uncontrolled inspiratory force in methods in which forced introduction of PV is not provided.