Epidemiology
Smell disturbances are frequent in contrast to the taste disturbances which are rather rare in society. Thus it is assumed that in Germany about 79,000 people per year undergo therapy in ENT clinics. In the following, a short overview of the terminology of olfactory disorders will be given.
Quantitative olfactory disorders
Hyperosmia: In case of hyperosmia one is particularly sensitive to olfactory stimuli. Normosmia: Normosmia is only listed for the sake of completeness. There is no change in the sense of smell.
It is therefore the normal state. Hyposmia: If one suffers from hyposmia, the sense of smell is reduced. Partial anosmia: As the name suggests, partial anosmia is merely a loss of sensitivity to a certain odor or group of odors.
Functional anosmia: In the presence of functional anosmia, there is a pronounced impairment of the ability to smell. The residual olfactory capacity is no longer of any significance. Anosmia: In the case of anosmia, the olfactory ability is completely eliminated.
Qualitative olfactory disorders
Parosmia: In the context of a parosmia the smells are perceived differently. Phantosmia: A certain odour is perceived, although no odour is present. Pseudosmia/odor illusion: In the context of a pseudosmia, an odor is reinterpreted imaginatively by strong feelings. Olfactory intolerance: The affected person subjectively feels an increased sensitivity to odours. Objectively speaking, however, the sensation of smell is completely normal.
Causes of olfactory disorders
The causes of a taste disorder can be divided into two major groups. We distinguish sinunasele causes from non-sinunasal causes. Sinunasal causes: The term sinunasal refers to things that originate in the nose or sinuses.
As a result, the olfactory system (“olfactory apparatus”), i.e. the olfactory epithelium in the nose and the olfactory tract, which transmits information from peripheral to central, is not affected. There are several reasons for sinunasal causes of olfactory disorders. Inflammations caused by chronic infections in the nose or the paranasal sinuses, or inflammations caused by allergies or chronic hyperplastic sinusitis with nasal polyps can restrict the ability to smell.
However, it does not necessarily have to be inflammation that causes an olfactory disorder at the sinunasal level. Other sinunasal causes of an olfactory disorder include swelling of the mucous membranes, a curvature of the nasal septum or benign or malignant masses in the nose. Non-sinunasal causes: Here, changes in the olfactory epithelium or the olfactory tract are present, which then lead to an olfactory disorder.
As with sinunasal causes, there are many different possibilities that can lead to a non-sinunasal olfactory disorder. A non-sinunasal olfactory disorder can develop after a viral infection, head trauma or exposure to toxins such as formaldehyde, carbon monoxide or cocaine. Congenital olfactory disorders also belong to this group, as part of the olfactory tract is usually affected. Neurological diseases, such as multiple sclerosis, Parkinson’s or Alzheimer’s disease, can also lead to olfactory disorders. If an olfactory disorder is not caused by one of the non-sinunasel causes just mentioned, it is considered idiopathic, which means “without known cause”.