The term anosmia indicates a disturbance of smell that involves the complete loss of the ability to perceive one or more odors.
This disorder can occur in a transient or permanent form , but in any case it is a phenomenon that is associated with taste disturbances. This particular link is related to the fact that the sensation of taste is allowed by the simultaneous and synergistic stimulation of both the sense of taste and the sense of smell .
Therefore, lacking the ability to perceive odors, consequently also have repercussions on the ability to perceive tastes, especially the most delicate ones, causing an additional condition that takes the name of hypoageusia . If you think about it, it is a condition that we often experience when we have a cold in which both the ability to smell and taste food is lacking.
In addition to anosmia , other forms of smell disorders are identified, which can cause a decrease or alteration of the ability to perceive odors. Among these disorders the most common are:
- Hyperosmia , in which subjects perceive odors in an intense and annoying way;
- Hyposmia , in which the intensity of odors is lower;
- Parosmia , in which there is an incorrect perception of the olfactory stimulus;
- Cacosmia , in which the subject experiences a constant unpleasant odor sensation;
- Fantosmia , in which odors are perceived in reality that do not exist.
What are the causes of anosmia Anosmia
is a symptom that characterizes almost all of the affections affecting the nose and the very first respiratory tract as well as being also characteristic of traumatic events affecting the nervous structures that carry the sense of smell .
Non-traumatic causes of anosmia are:
- hypertrophic adenoids affecting children;
- prolonged use of nasal decongestant drugs ;
- nasal polyps ;
- allergic and vasomotor rhinitis;
The main cause of anosmia of traumatic origin and to be connected to traumas that mainly affect the area corresponding to the occipital lobe (posterior area of the brain) or frontal (anterior area of the brain). In this type of event, the continuity of the nerve pathways that connect the receptors located at the level of the nasal mucosa to the central nervous system (olfactory bulb and rhinencephalon) is interrupted, thus preventing the perception of odors. Often this type of event is irreversible and a total recovery of the sense of smell is to be considered a rarity.
In a smaller percentage of cases the condition of anosmiaand to be connected to pathological frameworks affecting the nervous system, which take the name of neuritis, and which are divided into:
- infectious , as in the case of diphtheria, influenza, and typhus;
- metabolic , for example in subjects suffering from diabetes;
- due to a lack of vitamins , especially vitamin A ;
- atrophic of the olfactory mucosa ;
- toxic , due to exposure to substances in particular professions.
In other subjects the cause is due to the lack of development, therefore congenital, of the nerve centers used for the perception of olfactory sensations.
Finally, there is a picture of anosmia in very particular conditions, ie in patients who have undergone removal of the larynx (total laryngectomy) in which normal breathing is interrupted. In this case, the air no longer passing through the nose no longer comes into contact with the olfactory receptors.
How is anosmia
diagnosed ? Diagnosis of anosmia and its causesthat led to this condition must be entrusted exclusively to an otolaryngology specialist, in order to reach the diagnosis of the disorder and to adopt the correct therapeutic strategy suited to the case.
One of the simplest methods to reach a diagnosis is the physical examination through an accurate examination of the structure of the nose (rhinoscopy) in which instruments such as the rhinoscope are used which is inserted inside the nostril.
The doctor will then evaluate the possible presence of pathologies affecting the nose that may exist such as malformations, nasal polyps or obstructions that prevent the air from reaching the mucous membrane of the nose, where the olfactory receptors that will send the odoriferous stimuli are located. to the central nervous system that processes them.
More complex methods, on the other hand, make use of specific diagnostic tools, in which two main methods are distinguished:
- olfactometry: it is a very frequent test in the evaluation of smell disorders, it is non-invasive and does not cause pain. It takes place by administering to the patient some olfactory stimuli contained within small bottles or mechanical syringes, and a written list of responses. Based on the number of correct answers given by the patient, a picture of effective anosmia or hyposmia (in which the ability to perceive olfactory stimuli is reduced) will be outlined. It is a test as simple as it is subjective, therefore the reliability of the answers provided cannot be assessed with measurable criteria. It must be taken into consideration that the patient may be uncooperative and may lie, therefore this type of examination is not always the primary choice for diagnosing anosmia;
- radiological diagnostics: in this type of examinations very precise instruments are used that investigate the possible presence of pathologies affecting the nose (such as tumors or inflammation) or lesions affecting the nervous system involving the olfactory tracts.
What treatments exist
It should be remembered that the indication and prescription of the therapy must be dispensed only by a specialist doctor, only after having made a diagnosis and after having assessed the patient’s general state of health.
The treatments available today are sometimes not completely resolving the problem, except for a small number of subjects affected by olfactory disorders.
The cases that offer the best prospects for recovery are those related to obstructive phenomena in this way, by removing what prevents an adequate flow of air through the nose, it is possible to resolve the problem and return to perceive odors.
Where the triggering cause is anosmiaand to be linked to the presence of polyps or inflammation, a therapy with corticosteroids administered both locally (in the form of nasal sprays), systemic intramuscular or oral route is used. The use of corticosteroids often results in a solution for a large number of patients, but in some cases it is not sufficient.
We then proceed to other therapeutic strategies and therefore to surgery , especially in the case of malformations of the structure of the nose, in which the most performed surgery is septoplasty, where the nasal septum is corrected.
The therapy , on the other hand, is poorly effective, or sometimes ineffective, in patients who have suffered a trauma such as to interrupt the nerve pathways.
A type of treatment that involves the administration of hyaluronic acid is currently being studied, with the assumption that it can promote the regeneration capacity of the mucous membrane of the nose. However, these are studies still in the evaluation phase and not yet in-depth to indicate its use as a therapeutic choice.