Anosmia

Anosmia, also known as anosphresia or olfactory anaesthesia, is the complete lossabsence of the sense of smell. 

Terminology

In addition to anosmia, there is also hyposmia (a.k.a. olfactory hypoesthesiahypoaesthesia) representing a diminished sense of smell and parosmia (a.k.a. dysosmia or paraosmia) referring to any pathology of the olfactory system^1,5. 

Epidemiology

It is estimated that the point prevalence of an impaired sense of smell is as much as 19.1% adult population, and four-fifths of over 75-year-olds ².

Pathology

Aetiology

The underlying causes of anosmia may be subdivided into²:

• conductive: an obstruction to the passage of odorants, or
• sensorineural: an impairment of the ability to detect the odorants

Conductive

Common

• allergic rhinitis
• rhinosinusitis +/- sinonasal polyposis
• recreational drugs, e.g. cocaine

Uncommon

• systemic pathologies with olfactory complications, e.g. granulomatosis with polyangiitis
• postoperative, for example nasal surgery
• medications, e.g. antibiotics, 

Sensorineural

Common

• post-viralviral infections e.g. coronaviruses, 
• neurological disease, primarily neurodegenerative, e.g. Parkinson disease, Alzheimer disease, also stroke, myasthenia gravis
• psychiatric
  • depression
  • bipolar disorder
  • schizophrenia
• head injury

Uncommon

• intracranial lesions
• toxins, e.g. heavy metals, solvents (e.g. ammonia, benzene)
• genetic, e.g. Kallman syndrome

History and etymology

Anosmia is derived from Classical Greek roots. "οσμη" (osme) means the an aroma or scent. "" (an) is a prefix used to indicate negation ⁴.