Congenital and unilateral anosmia: how to treat

The complete loss of sensation of smell - anosmia - is a violation of the functions of the olfactory sensory system and arises for various reasons, being a symptom of a fairly large number of diseases.

In addition, many diseases, in the symptomatology of which there is a decrease or a partial loss of smell - hyposmia. Both variants are classified according to ICD-10 as one of the manifestations of diagnosed disease states and pathologies associated with perception, and have the code R43.0.

[1], [2], [3], [4]

Epidemiology

Judging by how little doctors talk about anosmia (the biochemistry of odor perception is being studied, but not fully understood), the data on its prevalence are contradictory. However, experts at the American Academy of Neurology (AAN) say that about 14 million Americans over 55-60 years of age have problems with smell, and more than 200,000 people turn to doctors about this every year.

Men are more likely than women to lose their sense of smell, especially smokers and those who have experienced a stroke or suffer from chronic rhinitis and  nasal congestion.

According to the British Rhinological Society, at least 220,000 British adults complain of a decrease in smell. A poll of almost 10 thousand people in Spain showed that two out of every ten respondents have this or that form of deterioration of the perception of smell.

Complete anosmia in 2004 was diagnosed in 1.4 thousand adult Swedes (with a population of 10 million). Basically, these are elderly people, and specialists explain this by atrophy and a reduction in the number of olfactory neurons or sensoneural disorders characteristic of elderly people.

[5], [6], [7], [8],

Causes of the anosmia

The key causes of anosmia are gradation, which is based on the neurophysiology of odor perception and the clinical features of respiratory and paranasal diseases, as well as neurosensory pathologies.

In terms of duration, loss of smell can be temporary and permanent, and for etiology - congenital (genetically determined) and acquired. Most often, the symptoms of anosmia occur at the level of the epithelium of the nasal cavity and olfactory receptors (neurosensory cells).

Thus, the initial or essential anosmia is determined by destructive changes in the olfactory epithelium, when receptors cease to detect odors, that is, react to particles of volatile substances that enter the nasal cavity with air. This form of loss of smell is considered peripheral and as a symptom occurs with infections, in particular, as a loss of smell in the common cold.

First of all, loss of smell is noted for colds, but it should be borne in mind that 25% of rhinoviruses do not give symptoms, and perhaps the only sign may be loss of smell without a cold, diagnosed as idiopathic.

As a rule, the temporary loss of smell after the flu does not cause people anxiety, because the cells of the olfactory epithelium can be restored (for more on this, see the section on the treatment of anosmia).

Olfactory sensory neurons from bacterial toxins suffer much more. Thus, loss of smell in genyantritis, especially chronic, is explained by otolaryngologists by the fact that the inflammatory process, localized in the paranasal sinuses, can spread higher - into the frontal sinuses, and the resulting swelling compress the olfactory nerve. Serious attitude requires  acute inflammation of the trellis labyrinth, which can be a complication of sinusitis and lead to a complete loss of smell. Irritation of the mucous membranes, their dystrophy and partial loss of smell are characteristic of chronic atrophic rhinitis, sinusitis, frontitis, and  oes.

Severe mucosal edema and nasal occlusion with secretions of different consistency and decreased olfaction are symptoms of hay fever (allergic rhinitis).

At any age, nasal congestion and loss of smell due to nasal obstruction can occur not only in the common cold, but also due to curvature of the nasal septum, adenoids, the presence of foreign bodies in the nasal cavity, and the presence of polyps and  malignant tumors of the nose. Moreover, problems with odor discrimination are caused not only by the nasal polyposis itself: rhinologists admit that there is a loss of smell after removal of polyps or a tumor, and also after unsuccessful rhinoplasty due to the formation of scars or cartilaginous bridges (synechiae) in the nose.

The olfactory receptors are affected by the inhalation of toxic chemicals, pesticides, heavy metals and radiation therapy: complete loss of smell after irradiation is the consequence of gamma radiation treatment of brain tumors, bone tissue and skin of the facial part of the skull.

Some nasal drugs, in particular, relieving nasal congestion, can damage the olfactory epithelium and even cause  dependence on drops in the nose.

Frequent swelling of the nasal mucosa causes an alternative treatment of the common cold with homemade garlic or onion drops that scorch the mucous membrane. There may be a loss of smell after the cyclamen (Cyclamen purpurascens) used in homeopathy: when buried in the nose of undiluted juice from its tubers containing poisonous saponins, the mucosa may swell, as in a chemical burn.

Loss of smell during pregnancy in most cases is partial, due to swelling of the nasal mucosa in response to changes in the hormonal background, as well as with a common cold or exacerbation of allergies.

What is neurotransmitter and central anosmia?

The ability to sense odors can be lost due to a violation of the transmission of signals from olfactory sensory neurons to the brain (sensory transduction) or damage and dysfunction of the main brain structures that analyze nerve impulses and generate a response-a limbic system-sensed smell. In the first case, it is a neurotransmitter (conductor) anosmia, and in the second case - about the central (cerebral) or sensorineural.

Violation of sensory transduction caused anosmia after a head injury - with a fracture of the base of the anterior cranial fossa or latticed bone. Many patients may experience unilateral (unilateral) anosmia (or hemianosmia) as a result of minor head trauma. And the causes of anosmia of central origin in craniocerebral trauma are associated with damage to the frontal lobes of the olfactory bulb or temporal lobes located in the frontal lobes of the brain.

Loss of smell without a cold is one of the clinical symptoms: the syndrome of Pehkrantz (adiposogenital dystrophy, which develops due to the defeat of the hypothalamus); Foster-Kennedy Syndrome; epilepsy, a significant increase in intracranial pressure, dementia (including Lewy bodies), Alzheimer's disease.

Bilateral or bilateral anosmia may result from herpetic encephalitis, primary amoebic meningoencephalitis, and neurosyphilis. To the loss of the sense of smell lead meningiomas of the anterior cranial fossa; malignant neoplasms in the region of the bridge-cerebellar angle or the pyramid of the temporal bone; Neurosurgical operations; neurotoxic drugs.

It is possible to simultaneously lose smell and taste - anosmia and agevia (ICD-10 code - R43.8): both sensory systems have specialized receptors stimulated by molecules of chemical substances, and their functions often complement each other as special visceral afferents of one limbic system. In addition, the olfactory system through the reticular formation is associated with the autonomic centers of the central nervous system, which explains the reflexes from the olfactory receptors to digestion and respiration, for example, nausea and vomiting with particularly unpleasant odors.

And the loss of touch and smell (anaphy and anosmia) is evidence that somatosensory is also impaired: the skin receptors do not react to external stimuli. Most often this is the result of traumatic damage to the frontal and temporal lobes of the brain or loss of functions of the limbic system of the brain in cases of CCT, stroke, intracranial aneurysm, brain tumors, multiple sclerosis.

Congenital anosmia is rare and occurs with hereditary ciliopathy (Kartagener syndrome), Callman and Refsum syndromes, congenital dermoid nasal cyst, and some other forms of abnormal embryonic development.

[9], [10]

Risk factors

It is logical that the risk factors for the appearance of a symptom are diseases. So, all the diseases listed above - from the common cold to the brain tumor - are treated by physicians as their number.

But we should separately say about zinc (Zn), more precisely - about its deficiency in the body. In clinical medicine, loss of smell is considered one of the first signs of chronic zinc deficiency, which also reduces the production of blood leukocytes and reduces resistance to infections.

This microelement is an integral part of at least three thousand different proteins of our body, it is necessary for the production of the metaloenzymatic carbonic anhydrase (CAs VI), which ensures the maintenance of the optimal pH level, tissue regeneration and nerve conduction.

[11], [12], [13], [14], [15], [16]

Pathogenesis

Explaining the pathogenesis of loss of smell in ARI and runny nose, it must be borne in mind that it perceives odors not respiratory ciliated epithelium (regio respiratoria) covering the nasal cavity, but a special olfactory localized in the region of the olfactory or smell (regio olfactoria) between the upper parts of the shells and a septum of the nose.

The mucosa of the olfactory region of the nose has a very complex structure: almost 10 million olfactory sensory neurons are concentrated here, each of them having a dendrite with cilia at one end and an axon on the opposite side. The olfactory epithelium is covered with a mucous secret, and the cilia of the chemoreceptors are a binding protein produced by tubuloalveolar glands that are located around the cilia. In addition, there is a supporting epithelium (for protection of chemoreceptors) and cells of the basal plate of the mucosal epithelium.

It is suggested that the pathogenesis of essential anosmia in rhinitis lies in a reduction in the functional activity (or complete blocking) of the cilia of neurons in the olfactory epithelium due to hyperproduction of mucus, and in cases of chronic inflammation of the mucosa or chemical effects on it - in the atrophy of the olfactory epithelium and its replacement with respiratory epithelium.

Central olfactory ways are formed by axons of olfactory sensory neurons. They are connected in two bundles of non-myelin sheaths of afferent fibers-olfactory nerves (I pair of cranial nerves). These nerves pass through the latticed bone, the prefrontal cortex of the frontal lobe and the olfactory bulbs (clusters amplifying the signal of neurons working as a relay of the olfactory analyzer). Any damage to these structures creates an obstacle to the transmission of impulses and can lead to a complete or partial loss of smell (one- or two-sided).

In the olfactory nerves, the signal enters the endpoint - the structures of the limbic system of the brain: the pyroform and entorhinal cortex of the temporal lobes of the large hemispheres and the amygdala (responsible for the final coding of odor signals by neurons and behavioral reactions to smells). Pathologies in these locations lead to a lack of analysis of signals from olfactory sensory neurons, without which it is simply impossible to smell.

[17], [18]

Complications and consequences

Proceeding from the functions performed by the sense of smell, the main consequences and complications of its partial or complete absence relate to the recognition of the degree of suitability of food for consumption: without perceiving the smell of a spoiled product, it is easy to get food poisoning. And in some situations - for example, a gas leak, electrical appliances, or the presence of toxic gaseous substances in the air - there is a direct threat to life.

At the same time, anomics often retain a normal sense of taste, but the usual psycho-emotional reactions to smells are absent.

Even a partial loss of smell can lead to a decrease in appetite and a depressed state. According to some reports, 17% of people suffering from acquired anosmia fall into depression, without smell, causing positive emotions or associated with pleasant memories.

The right to disability in anosmia (with the appointment of a benefit) can arise only when this condition - along with other symptoms - prevents a person from working, and this happens with strokes, diseases and traumatic brain damage, psychosomatic disorders, etc.

[19], [20], [21], [22]

Diagnostics of the anosmia

The loss of smell is a symptom of various diseases, and the diagnosis of anosmia is reduced to their detection.

Usually with acute rhinitis, the diagnosis of special problems does not cause: the ENT-physician enough to listen to the patient's complaints and conduct a rhinoscopy (examination of the nasal passages and nasal cavity). But if the patient has a protracted or chronic runny nose, nasal congestion and loss of smell, then tests, including analysis of mucus from the nose, will be required  . And if the rhinitis is associated with sensitization, the otolaryngologists send the patients to the allergist - to  diagnose allergies.

In clinical otolaryngology, instrumental diagnostics is used: x-ray of the paranasal and frontal sinuses and  endoscopy of the nasal cavity; To assess nasal breathing, rhinopneumometry is performed, and olfactory sensitivity (with a test kit for odor testing) is used to determine the degree of olfactory sensitivity.

[23], [24], [25], [26]

Differential diagnosis

In cases where anosmia as a clinical symptom is present, and its obvious cause can not be determined, differential diagnosis of paranasal diseases and cerebral pathologies is required, including: CT of the head (including sinuses) with contrast and MRI of the brain. Useful information is also in the article -  Investigation of cranial nerves. I pair: olfactory nerve

Many cases of congenital anosmia are not documented and diagnosed: since the disorder is present at birth, the patient's perception of a smell may be minimal or nonexistent.

Treatment of the anosmia

Symptomatic treatment of anosmia is not currently performed: there are no drugs for olfactory recovery. So the therapeutic effects are diseases, in the symptoms of which there is a loss of smell.

That is, if the sensation of smell is lost due to a common cold, then in its treatment apply: different in composition  drops from the common cold, easy-to-use  sprays from nasal congestion. Practice is the appointment of topical glucocorticoids (corticosteroids) as a remedy against mucosal edema, for example, Nasonex in case of loss of sense of smell is used in cases of allergic rhinitis or acute sinusitis - read  Nasonex Sinus  (instructions for use).

But the use of intranasal means does not guarantee the restoration of olfaction, moreover, the mechanism of their pharmacological action and does not take into account the damage to the olfactory epithelium of the nasal cavity. Similarly, inhalations with loss of smell are aimed at eliminating the obstruction of nasal passages, and they certainly bring relief in the common cold. The most effective will be herbal treatment: hot steam inhalation with the addition of chamomile or lavender flowers, plantain leaves, eucalyptus or sage and thyme grass - five minutes a day, three to four times a week or every other day. Physiotherapeutic treatment is also possible - see  Physiotherapy with rhinitis

It is not excluded the appointment of oral administration of Dexamethasone (other trade names - Dexacort, Decadin, Cortadax, Hexadrol, Millicorten, Ortadexon, Resticort) - per tablet (0.5 g) once a day (morning). GCS is contraindicated in acute viral, bacterial and fungal infections, Cushing's syndrome, osteoporosis, chronic hepatitis, pregnancy and lactation. Among its side effects: a decrease in the level of calcium in the body and increased fragility of bones, a decrease in lymphocytes and an increase in the level of erythrocytes in the blood, a deterioration in the functions of the adrenal-pituitary-hypotensive system.

B vitamins B, zinc preparations -  vitamins with zinc, and also lipoic acid (Protogen, Thioacticide), which improves the sense of smell in rhinovirus diseases; recommend taking 0.5-0.6 g per day (for one to two months). Lipoevuyu kstlotu contraindicated to use in gastritis with increased acidity and ulcer of the stomach and duodenum.

Antibiotic therapy is necessary for sinusitis and sinusitis of bacterial etiology, with meningitis, and patients with polyps in the nose and tumors undergo surgical treatment.

If the olfactory periphery is damaged, the olfactory sensory neuron population is destroyed, but the olfactory receptor cells serve, on average, for two months. Like the taste buds of the tongue, the olfactory neuroreceptors are periodically updated, and this is due to the production of the basal fibroblast growth factor (bFGF) by the basal cells of the primary olfactory epithelium, which allows them to differentiate into sensory neurons, compensating for loss and regenerating damage.

In Japan, they try to treat the acquired anosmia by applying a gelatin hydrogel with bFGF to the nasal mucosa.

Prevention

The means for specific prevention of manifestations of such a symptom as loss of smell do not exist, and doctors' advice concerns:

• rational use of drops and aerosols for the treatment of the common cold of any etiology;
• Stay in areas with polluted air, which should be avoided in every possible way;
• refusal from smoking and alcohol;
• increasing physical activity;
• timely treatment of rhinitis and paranasal diseases.

[27], [28], [29]

Forecast

The olfactory system has a unique ability to recover, but unfortunately, anosmia does not always give in to treatment, especially if the cause is age, brain and CNS pathologies or nerve damage.