Olfactory impairment (dysosmia) is a variety of odor perception disorders that are manifested by an increase or decrease in olfactory function, an inability to recognize familiar aromas. The symptom occurs in inflammatory processes in the nasal cavity, craniocerebral injuries, other neurological or psychiatric diseases. To determine the root cause of the impaired sense of smell, olfactometry, ENT examination, radiography and tomography of the skull bones are performed. Until an accurate diagnosis is made, medications are not prescribed.
Manifestations depend on the characteristics of the olfactory disorder. Patients may notice a decrease in sensitivity to smells or a complete loss of smell. Dysosmia often forms gradually: first, sensitivity to weak odors disappears, and then even sharp odorous substances (for example, ammonia) cease to differ. Often, taste sensations are simultaneously reduced. If the condition is formed against the background of inflammatory diseases, olfactory disorders are combined with mucous secretions, nasal congestion, itching and burning.
In other cases, there is an increase in sensitivity to aromas, when even familiar smells cause discomfort to a person, cause headaches and other unpleasant sensations. With a perversion of smell, patients may notice a sudden sensation of stench, which is described as the smell of feces, gasoline, chemicals (cacosmia). Disorders of the olfactory function do not pose a threat to human life, but sometimes they become the first symptoms of severe neurological diseases, so when they appear, you should seek qualified medical help.
The olfactory zone of the nasal mucosa, containing specific nerve receptors, is located in the superior nasal concha. In order for a person to smell odors, air, along with odorous substances, must pass through this section of the respiratory tract. In the presence of mechanical obstacles to the passage of air to the anatomical structures, olfactory disturbances are observed, such as a decrease in sensitivity to some or all odors. This condition is often caused by deviated nasal septum, hypertrophic rhinitis, sinusitis and adenoids.
Pathological insensitivity to odorous substances can be provoked by violations from different parts of the olfactory analyzer. Normally, information from the receptors of the nasal mucosa through special fibers enters the subcortical structures and the center of smell in the cerebral cortex. The symptom is noted with traumatic injury and rupture of the olfactory nerve due to craniocerebral trauma, errors during neurosurgical operations. With unilateral damage to the nervous structures, the loss of smell is determined only on the side of the pathological process.
Inhibition of sensitivity to various aromas develops during pathological processes in the mucous membrane of the nasal cavity (for example, atrophic rhinitis), when peripheral nerve receptors are destroyed. Smell disturbances also occur in degenerative brain diseases (Parkinson's, Alzheimer's) and brain tumors. In this case, dysosmia is due to gradual atrophy and death of the nerve cells of the olfactory zone.
A special mechanism of smell impairment is characteristic of epilepsy. In this disease, patients note the appearance of unpleasant odors, which is associated with the formation of excitation zones in the brain, impulses from which spread to various parts of the cortex. Dysosmia can also occur in the absence of organic pathology - a symptom is observed in acute psychoses, hysterical states. The development of olfactory dysfunction is associated with functional impairment of connections between the parts of the peripheral and central nervous system.
Olfactory disorders are divided into acquired and congenital (with Kallman's syndrome). All pathological conditions are classified into two groups: symptoms of irritation (increased sensitivity to various odors) and symptoms of loss (decrease in smell). To choose the right method of treatment, classification by type of disorders is also important, according to which the following types of olfactory disorders are distinguished:
Depending on the location of the lesion, rhinogenic olfactory disorders are distinguished, which are associated with chronic rhinitis, deviated septum, nasal polyps, and neurosensory. The latter, in turn, are divided into peripheral (pathology of the olfactory nerve endings in the nasal cavity) and central (damage to the brain centers of smell). Separately, combined dysosmia is distinguished, when nasal breathing disorders are combined with changes in the mucous membrane of the olfactory region.