A set of odorous substances for licensing. Diagnosis and treatment of olfactory disorders

Rationale. Measuring the strength of the sense of smell makes it possible to judge the qualitative or quantitative violation of the sense of smell, to evaluate the various effects of various nasal diseases on it. This is especially important before performing rhinological operations and evaluating their results, for diagnosing perceptual disorders of smell, during professional selection, medical expertise, as often an undiagnosed violation of the sense of smell is determined in patients with diseases of the nose.

Identification of already existing hypo- or anosmia makes it possible to avoid claims that these disorders were caused by the operation.

Depending on what information is needed, specific tests can be performed to determine various aspects of the olfactory system. For rhinology, the quantitative assessment of the sense of smell is important, since hypo- and anosmia are common symptoms in diseases of the nose, such as allergic rhinitis or chronic rhinosinusitis, due to violation of the smell. It is much more difficult to measure qualitative disorders, the so-called dysosmia (parosmia, kakosmiya).

Target. The study of the function of the olfactory analyzer can be used to diagnose perceptual disorders of smell, before performing rhinological operations and to evaluate their results.

Indications. Evaluation of the results of ongoing therapy, diagnosis of perceptual disorders of smell and pathology of the anterior cranial fossa, assessment of professional suitability.

Methodology. Among the subjective methods, screening tests and measurement of the threshold of sensation are commonly used to quantify hypo- and anosmia. Qualitative type methods: odor identification tests and discrimination assessment. The study of smell includes preparation, delivery of an odorous substance to the olfactory zone and evaluation of the reaction of the olfactory analyzer. Subjective examination methods are often used in practice, as they can be performed easily and quickly in a patient who is able to answer questions. Over the past 10 years, several certified screening methods for examining the sense of smell have been developed in the world, which can be carried out by both the doctor and the patient at home. To get a general idea of ​​the set various methods olfactory research, they can be divided into three categories.

Smell screening methods are designed in such a way that they can only determine whether a patient has a smell disorder or not. AT clinical practice most often subjective methods are used. The simplest way research - the use of a set of odorous substances.
It is necessary to have a standard set of 4-6 odorants in sealed vials. It is necessary to conduct a study for each nostril separately to determine whether the violation is unilateral or bilateral (lateralized screening). In children, the study is carried out with turundas moistened with various odorants, the smell of which is familiar to the subject. Starting from the lowest concentration, vessels with an odorous substance are alternately brought to the patient at a distance of 1 cm from the examined half of the nose. After one normal breath, the subject must answer whether he smelled and characterize it.

The dilution of an odorous substance, at which the patient smelled, characterizes the threshold of odor perception, and the dilution that allows you to recognize or characterize the smell - the threshold of odor recognition. Depending on the ability of the olfactory analyzer to recognize various odors, 4 degrees of hyposmia are distinguished: 1st degree (weak smell) - 0.5% solution acetic acid; 2nd degree (medium smell) - pure wine alcohol; 3rd degree ( strong smell) - Valerian tincture; 4th degree (very strong smell) - ammonia.

Quantitative tests (odorimetry) of olfactory function evaluate the threshold of smell of certain odors (the lowest concentration of an odorous substance that can be detected by the researcher at the moment), measuring the degree of impairment of odor perception. The threshold of recognition (the concentration of an odorous substance, which allows not only to feel, but also to recognize the smell) will be slightly higher than the threshold of smell. Devices designed to determine these thresholds are called olfactometers.

There are two main methods of olfactometry: direct and indirect. The direct method measures the amount of odorant required to produce an olfactory sensation. With an indirect method, quantitative indicators of the intensity of the stimulus are determined, for example, the time of smell perception, the concentration of an odorous substance in a solution, etc. There are two main types of olfactometers: with active inspiration, when the patient draws air through the olives inserted into the nose, which first passes through the vessel, where it is saturated with an odorous substance (indications in this case depend on the strength of sniffing); and with forced injection of an odorous mixture.

In practical terms, a quantitative study of smell is usually carried out using a large set of odorous substances, when solutions of various concentrations are prepared from the initial concentration of an odorous substance, which is taken as a unit. Along with determining the threshold of smell in differential diagnosis olfactory disorders, a study of the adaptation process in the olfactory analyzer is used - olfactoadaptometry. The fatigue of the olfactory analyzer develops with prolonged continuous irritation by its odorous substance. The time after which the patient ceases to perceive the threshold dose of the odorous mixture determines the adaptation time. After the cessation of exposure to an odorous substance, the activity of the olfactory analyzer is restored. The beginning of the patient's perception of a previously established threshold dose of an odorous substance determines the readaptation time.

Qualitative olfaction tests are used to assess a wide range of qualitative olfactory disorders and to determine the ability to perceive and distinguish odors. The method of V.I. Voyachek, based on the use of substances with odors of increasing strength, irritating mainly olfactory and trigeminal sensitivity. However, this method, even if absolutely correct execution, has a number of disadvantages, since it is often an impossible task for many patients to recognize odors, even very familiar ones. Assessment of the condition of the trigeminal nerve. In addition to the olfactory hairs, there are endings of the trigeminal nerve in the nasal mucosa. They are needed to determine tactile sensations, pain and temperature changes. The use of special odorants with an irritating component trigeminal nerve possibly to assess his condition.

Factors affecting the result. It should be noted that the threshold of smell even for healthy people during the day is very variable and depends on various reasons: emotional state, state of the nasal cavity at a particular moment. The result of the study also affects whether the subject was warned about the nature of the smell, whether he knew it before, therefore, in order to obtain more accurate data, a quantitative method was proposed.

Alternative methods. Objective research methods. Registration of various unconditioned reflexes and reactions of the central nervous system after exposure to a stimulus is referred to as objective methods, it is convenient to use in pediatric practice. There are the following methods of objective olfactometry: registration of reflex phenomena after stimulation of receptors (registration of olfactory-pupillary, olfactory-respiratory reflexes, reactions of cardio-vascular system and etc.); registration of bioelectric activity of the brain after adequate stimulation; direct assignment of biopotentials from the olfactory region. Registration of brain biopotentials during stimulation of the olfactory analyzer is carried out using electroencephalography and an electronic counting device. However, wide practical use objective electroencephalographic olfactometry is impossible due to technical difficulties; therefore, subjective methods of olfactometry based on the answers of the subject are widely applicable in clinical practice.

In addition to recording olfactory evoked potentials, objective methods include functional MRI and functional positron emission tomography, which can directly show functional changes in the central nervous system in response to odor stimulation. At the moment, these methods are used only for scientific research, but they have the opportunity to become one of the standard clinical studies.

Taste and smell are independent senses, but it is often difficult to draw a line between them only on the basis of the patient's history and complaints. Since isolated taste disorders are extremely rare, a simple study can be done immediately to rule out such a diagnosis. Taste sensitivity is determined using special solutions, such as: salty, sour, bitter, sweet, which makes it possible to detect the absence of perception of one of them. Loss or disturbance of taste can be varying degrees gravity.