Olfactory Disorders (Dysosmia)

Olfactory disorders (synonyms: dysosmia, olfactory disorder, olfactory disorder) are classified as follows:

Quantitative classification of olfaction

• Anosmia (ICD-10-GM R43.0).
  • Functional anosmia: low residual ability, meaningful use of the sense of smell in everyday life not possible
  • Complete anosmia: complete loss of olfaction/loss of sense of smell (loss of smell); no residual ability to smell.
• Hyposmia (ICD-10-GM R43.8): decreased ability to smell.
• Normosmia: normal olfactory capacity.
• Hyperosmia (ICD-10-GM R43.1): increased ability to smell (very rare).

Qualitative disorder of the ability to smell

• Parosmia (ICD-10-GM R43.1): qualitative olfactory or olfactory disorder with disease value in the presence of an irritant source.
• Phantosmia (synonyms: hallucinatory olfactory impressions): perception of odors in the absence of a stimulus source.
• Pseudoosmia: Affected reinterpret perceived odors imaginatively; for example, under the influence of affects (unconscious mis-smelling).
• Olfactory intolerance: affected persons react hypersensitively to fragrances, although the olfactory cells are no more sensitive than normal.

For other forms, see “Classification” below. As part of a multisensory event, smelling plays an important role alongside hearing and vision:

Eating and drinking show the interaction of three sensory channels:

• Gustatory system (glossopharyngeal nerve, facial nerve, vagus nerve); this mediates the following tastes:
  • Sweet, sour, salty, bitter, and umami (= taste of glutama; taste like meat broth).
• Trigeminal system (trigeminal nerve) mediates:
  • Pungency(of mustard) or tingling (of carbonic acid).
• Olfactory system* (nerve olfactorius/smell nerve) mediated:
  • Thousands of odors [Loss of sense of smell is perceived by many patients as a diminution of taste perception].

* First retronasal olfaction accounts for fine taste (flowers (fragrances), wine (aromas), etc.): Volatile aroma compounds released during the consumption of food are transported through the pharynx into the paranasal sinus to the olfactory receptor cells. Disturbances of the sense of smell occur, among other things, when the tractus olfactorius is damaged. Patients who have lost their sense of smell or were born without a sense of smell often have the following complaints:

• Lack of warning function leads to food poisoning, for example.
• Lack of judgment of food and drink leads, for example, to the loss or lack of enjoyment and reward by eating and drinking.
• Lack of perception of body odors causes, for example, insecurity in social contacts (partnership, etc.)

The S2 guideline “Olfactory disorders” distinguishes sinunasal (sinus-related) and non-sinunasal causes of olfactory dysfunction (for details see below “Classification”). Dysosmia can be a symptom of many diseases (see under “Differential diagnoses”). Frequency peak: The disease presbyosmia (deteriorated ability to smell) occurs predominantly after the age of 50. The prevalence (disease frequency) for anosmia is about 5% (in Germany). Approximately one quarter of the population has presbyosmia (> 50 years). Approximately 80,000 people with olfactory disorders are treated in Germany each year. Course and prognosis: The therapy of dysosmia depends on the underlying disease. Since dysosmia is a disorder of a sensory organ, the disease represents a stressful event for the affected person.If nasal (nose-related) diseases are the cause of the olfactory disorder, causal treatment options are available. In addition to surgical therapy, the administration of glucocorticoids is the primary treatment.Olfactory disorders are considered a leading symptom in allergic rhinitis (AR; hay fever) (frequency 20-40%).The prognosis of the olfactory disorder depends on the cause and the time elapsed since the onset of the disorder.Sometimes, spontaneous recovery can occur, even if the disorder has been present for several years. Caution. Olfactory disorders occur as an early symptom of idiopathic Parkinson’s syndrome (IPS) and Alzheimer’s dementia (AD). An appropriate differential diagnosis is therefore indicated (indicated).