Medicine:Anosmia

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Short description: Inability to smell
Anosmia
Other namesLoss of smell, smell blindness,[1] odor blindness
A side view anatomical drawing of the nasal sinuses depicting inflamed mucosa
Inflamed nasal mucosa causing anosmia
Pronunciation
SpecialtyOtorhinolaryngology
TypesPartial, total[2]

Anosmia, also known as smell blindness, is the loss of the ability to detect one or more smells.[1][2] Anosmia may be temporary or permanent.[3] It differs from hyposmia, which is a decreased sensitivity to some or all smells.[2]

Anosmia can be due to a number of factors, including inflammation of the nasal mucosa, blockage of nasal passages, or destruction of temporal lobular tissue.[4] Anosmia stemming from sinus inflammation is due to chronic mucosal changes in the lining of the paranasal sinus and in the middle and superior turbinates.[5][6]

When anosmia is caused by inflammatory changes in the nasal passageways, it is treated simply by reducing inflammation.[7][8] It can be caused by chronic meningitis and neurosyphilis that would increase intracranial pressure over a long period of time,[9] and, in some cases, by ciliopathy,[10] including ciliopathy due to primary ciliary dyskinesia.[11]

The term derives from the Neo-Latin anosmia, based on Ancient Greek ἀν- (an-) + ὀσμή (osmḗ 'smell'; another related term, hyperosmia, refers to an increased ability to smell). Some people may be anosmic for one particular odor, a condition known as "specific anosmia". The absence of the sense of smell from birth is known as congenital anosmia.[12]

In the United States, 3% of people aged over 40 are affected by anosmia.[3]

Anosmia is a common symptom of COVID-19 and can persist as long COVID.[13]

Definition

Anosmia is the inability to smell.[1] It may be partial or total, and can be specific to certain smells.[2] Reduced sensitivity to some or all smells is hyposmia.[2]

Signs and symptoms

Anosmia can have a number of harmful effects.[14] People with sudden onset anosmia may find food less appetizing, though congenital anosmics rarely complain about this, and none report a loss in weight. Loss of smell can also be dangerous because it hinders the detection of gas leaks, fire, and spoiled food. The common view of anosmia as trivial can make it more difficult for a patient to receive the same types of medical aid as someone who has lost other senses, such as hearing or sight.[citation needed]

Many experience one sided loss of smell, often as a result of minor head trauma. This type of anosmia is normally only detected if both of the nostrils are tested separately. Using this method of testing each nostril separately will often show a reduced or even completely absent sense of smell in either one nostril or both, something which is often not revealed if both nostrils are simultaneously tested.[15]

Losing an established and sentimental smell memory (e.g. the smell of grass, of the grandparents' attic, of a particular book, of loved ones, or of oneself) has been known to cause feelings of depression.[16][better source needed]

Loss of the ability to smell may lead to the loss of libido, but this usually does not apply to those with olfactory dysfunction at birth.[16][17]

Often people who have loss of smell at birth report that they pretended to be able to smell as children because they thought that smelling was something that older/mature people could do, or did not understand the concept of smelling but did not want to appear different from others. When children get older, they often realize and report to their parents that they do not actually possess a sense of smell, often to the surprise of their parents.[citation needed]

Causes

A temporary loss of smell can be caused by a blocked nose or infection. In contrast, a permanent loss of smell may be caused by death of olfactory receptor neurons in the nose or by brain injury in which there is damage to the olfactory nerve or damage to brain areas that process smell (see olfactory system). The lack of the sense of smell at birth, usually due to genetic factors, is referred to as congenital anosmia. Family members of the patient with congenital anosmia are often found with similar histories; this suggests that the anosmia may follow an autosomal dominant pattern.[18] Anosmia may very occasionally be an early sign of a degenerative brain disease such as Parkinson's disease and Alzheimer's disease.[citation needed]

Another specific cause of permanent loss could be from damage to olfactory receptor neurons because of use of certain types of nasal spray; i.e., those that cause vasoconstriction of the nasal microcirculation. To avoid such damage and the subsequent risk of loss of smell, vasoconstricting nasal sprays should be used only when absolutely necessary and then for only a short amount of time. Non-vasoconstricting sprays, such as those used to treat allergy-related congestion, are safe to use for prescribed periods of time.[19] Anosmia can also be caused by nasal polyps. These polyps are found in people with allergies, histories of sinusitis, and family history. Individuals with cystic fibrosis often develop nasal polyps.[citation needed]

Amiodarone is a drug used in the treatment of arrhythmias of the heart. A clinical study demonstrated that the use of this drug induced anosmia in some patients. Although rare, there was a case in which a 66-year-old male was treated with amiodarone for ventricular tachycardia. After the use of the drug he began experiencing olfactory disturbance, however after decreasing the dosage of amiodarone, the severity of the anosmia decreased accordingly, suggesting a relationship between use of amiodarone to the development of anosmia.[20]

COVID-19-related anosmia

Chemosensory disturbances, including loss of smell or taste, are the predominant neurological symptom of COVID-19.[21][22] As many as 80% of COVID-19 patients exhibit some change in chemesthesis, including smell. Loss of smell has also been found to be more predictive of COVID-19 than all other symptoms, including fever, cough or fatigue, based on a survey of 2 million participants in the UK and US.[23] Google searches for "smell", "loss of smell", "anosmia", and other similar terms increased since the early months of the pandemic, and strongly correlated with increases in daily cases and deaths.[24] Research into the mechanisms underlying these symptoms is currently ongoing.[25][26]

Many countries list anosmia as an official COVID-19 symptom, and some have developed "smell tests" as potential screening tools.[27][28]

In 2020, the Global Consortium for Chemosensory Research, a collaborative research organization of international smell and taste researchers, formed to investigate loss of smell and related chemosensory symptoms.[29]

Possible causes

Diagnosis

Diagnosis begins with a detailed history, including possible related injuries, such as upper respiratory infections or head injury. The examination may involve nasal endoscopy for obstructive factors such as polyps or swelling.[4] A nervous system examination is performed to see if the cranial nerves are affected.[4] On occasion, after head traumas, there are people who have unilateral anosmia. The sense of smell should be tested individually in each nostril.[15]

Many cases of congenital anosmia remain unreported and undiagnosed. Since the disorder is present from birth the individual may have little or no understanding of the sense of smell, hence is unaware of the deficit.[51] It may also lead to reduction of appetite.[52]

Treatment

Though anosmia caused by brain damage cannot be treated, anosmia caused by inflammatory changes in the mucosa may be treated with glucocorticoids. Reduction of inflammation through the use of oral glucocorticoids such as prednisone, followed by long term topical glucocorticoid nasal spray, would easily and safely treat the anosmia. A prednisone regimen is adjusted based on the degree of the thickness of mucosa, the discharge of oedema and the presence or absence of nasal polyps.[7] However, the treatment is not permanent and may have to be repeated after a short while.[7] Together with medication, pressure of the upper area of the nose must be mitigated through aeration and drainage.[53]

Anosmia caused by a nasal polyp may be treated by steroidal treatment or removal of the polyp.[54]

One experiment, where two people were given a single dose of 1,000 mg of turmeric, reported to find improvements in COVID-19-induced anosmia (and ageusia), however actual studies have yet to be done regarding this.[55]

Although very early in development, gene therapy has restored a sense of smell in mice with congenital anosmia when caused by ciliopathy. In this case, a genetic condition had affected cilia in their bodies which normally enabled them to detect air-borne chemicals, and an adenovirus was used to implant a working version of the IFT88 gene into defective cells in the nose, which restored the cilia and allowed a sense of smell.[56][57]

Epidemiology

In the United States 3% of people aged over 40 are affected by anosmia.[3]

In 2012, smell was assessed in persons aged 40 years and older with rates of anosmia/severe hyposmia of 0.3% at age 40–49 rising to 14.1% at age 80+. Rates of hyposmia were much higher: 3.7% at age 40–49 and 25.9% at 80+.[58]

Famous people with anosmia

See also

  • Phantosmia
  • Parosmia
  • Anosmia Awareness Day
  • Zicam, a medicine that caused some users to permanently lose their sense of smell
  • Ageusia, the loss of the sense of taste

References

  1. ↑ 1.0 1.1 1.2 "4. Sensation and perception" (in en). Introduction to Psychology: Gateways to Mind and Behavior. Boston: Cengage Learning. 2014. p. 136. ISBN 978-1-305-09187-0. https://books.google.com/books?id=-4jCBAAAQBAJ&pg=PA136. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 "2. Making sense of symptoms" (in en). Practical Rhinology. CRC Press. 2010. pp. 24–25. ISBN 978-1-4441-0861-3. https://books.google.com/books?id=arSSpm-OgjYC&pg=PA25. 
  3. ↑ 3.0 3.1 3.2 3.3 "Anosmia". StatPearls. StatPearls Publishing. 6 July 2020. http://www.ncbi.nlm.nih.gov/books/NBK482152/. Retrieved 1 December 2020. 
  4. ↑ 4.0 4.1 4.2 "What Is Anosmia?". JAMA 324 (2): 206. July 2020. doi:10.1001/jama.2020.10966. PMID 32556300. 
  5. ↑ "Inflammatory diseases of the nasal cavities and paranasal sinuses". Diagnostic Histopathology 16 (6): 255–264. June 2010. doi:10.1016/j.mpdhp.2010.03.008. PMID 32336992. 
  6. ↑ "Studies on Clinical Features, Mechanisms, and Management of Olfactory Dysfunction Secondary to Chronic Rhinosinusitis". Frontiers in Allergy 3: 835151. 2022. doi:10.3389/falgy.2022.835151. PMID 35386650. 
  7. ↑ 7.0 7.1 7.2 "Anosmia". Lancet 2 (8609): 512. August 1988. doi:10.1016/s0140-6736(88)90160-2. PMID 2900434. (Subscription content?)
  8. ↑ "Sinusitis Clinical Practice Guideline Quick Reference Tools", Pediatric Clinical Practice Guidelines & Policies (American Academy of Pediatrics): pp. 481–484, 2022-04-11, doi:10.1542/9781610026086-part01-27, ISBN 978-1-61002-608-6, http://dx.doi.org/10.1542/9781610026086-part01-27, retrieved 2023-11-07 
  9. ↑ "Anosmia". The Lancet 241 (6228): 55. 1943. doi:10.1016/S0140-6736(00)89085-6. 
  10. ↑ "Olfactory Loss and Dysfunction in Ciliopathies: Molecular Mechanisms and Potential Therapies". Current Medicinal Chemistry 26 (17): 3103–3119. 2019. doi:10.2174/0929867325666180105102447. PMID 29303074. 
  11. ↑ "Ciliopathy with special emphasis on kartageners syndrome". International Journal of Health Sciences 3 (1): 65–69. January 2009. PMID 21475513. 
  12. ↑ "Anosmia-A Clinical Review". Chemical Senses 42 (7): 513–523. September 2017. doi:10.1093/chemse/bjx025. PMID 28531300. 
  13. ↑ "Q&A: COVID-19 and loss of smell, taste" (in en). https://www.mayoclinichealthsystem.org/hometown-health/featured-topic/q-and-a-covid-19-and-loss-of-smell-taste. 
  14. ↑ "Assessing the impact of anosmia: review of a questionnaire's findings". Chemical Senses 24 (6): 705–712. December 1999. doi:10.1093/chemse/24.6.705. PMID 10587505. 
  15. ↑ 15.0 15.1 "Anosmia". Practical Neurology 6 (1): 65. February 2006. http://pn.bmj.com/content/6/1/65.extract. 
  16. ↑ 16.0 16.1 "Sense and scent ability". BBC News. December 27, 2006. http://news.bbc.co.uk/2/hi/uk_news/magazine/6199605.stm. 
  17. ↑ "Depression resulting from olfactory dysfunction is associated with reduced sexual appetite--a cross-sectional cohort study". The Journal of Sexual Medicine 6 (7): 1924–1929. July 2009. doi:10.1111/j.1743-6109.2009.01266.x. PMID 19453919. 
  18. ↑ "Congenital Anosmia". Archives of Otolaryngology–Head & Neck Surgery 118 (1): 10. 1992. doi:10.1001/archotol.1992.01880010012002. https://jamanetwork.com/journals/jamaotolaryngology/article-abstract/620279. 
  19. ↑ Preventing Anosmia from Intranasal Zinc Administration[unreliable medical source?]
  20. ↑ "Anosmia induced by amiodarone". The American Journal of Medicine 120 (11): e9. November 2007. doi:10.1016/j.amjmed.2006.08.029. PMID 17976411. 
  21. ↑ "Olfactory and gustatory dysfunctions as a clinical presentation of mild-to-moderate forms of the coronavirus disease (COVID-19): a multicenter European study". European Archives of Oto-Rhino-Laryngology 277 (8): 2251–2261. August 2020. doi:10.1007/s00405-020-05965-1. PMID 32253535. 
  22. ↑ "Smell and taste dysfunction in patients with COVID-19". The Lancet. Infectious Diseases 20 (9): 1015–1016. September 2020. doi:10.1016/S1473-3099(20)30293-0. PMID 32304629. 
  23. ↑ "Real-time tracking of self-reported symptoms to predict potential COVID-19". Nature Medicine 26 (7): 1037–1040. July 2020. doi:10.1038/s41591-020-0916-2. PMID 32393804. 
  24. ↑ "Use of Google Trends to investigate loss-of-smell-related searches during the COVID-19 outbreak". International Forum of Allergy & Rhinology 10 (7): 839–847. July 2020. doi:10.1002/alr.22580. PMID 32279437. 
  25. ↑ Shelton, J. F., Shastri, A. J., Fletez-Brant, K., Aslibekyan, S., & Auton, A. (2022). The UGT2A1/UGT2A2 locus is associated with COVID-19-related loss of smell or taste. Nature Genetics, 54(2), 121-124.
  26. ↑ "COVID-19 and the Chemical Senses: Supporting Players Take Center Stage". Neuron 107 (2): 219–233. July 2020. doi:10.1016/j.neuron.2020.06.032. PMID 32640192. 
  27. ↑ Template:Cite medRxiv
  28. ↑ Template:Cite medRxiv
  29. ↑ "Global Consortium for Chemosensory Research" (in en). https://gcchemosensr.org/. 
  30. ↑ "Olfaction and its alteration by nasal obstruction, rhinitis, and rhinosinusitis". The Laryngoscope 111 (3): 409–423. March 2001. doi:10.1097/00005537-200103000-00008. PMID 11224769. 
  31. ↑ "The prevalence of symptoms in 24,410 adults infected by the novel coronavirus (SARS-CoV-2; COVID-19): A systematic review and meta-analysis of 148 studies from 9 countries". PLOS ONE 15 (6): e0234765. 23 June 2020. doi:10.1371/journal.pone.0234765. PMID 32574165. Bibcode: 2020PLoSO..1534765G. 
  32. ↑ "Coronavirus Disease 2019 (COVID-19) – Symptoms" (in en-us). 13 May 2020. https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html. 
  33. ↑ "Will we ever cure nasal polyps?". Annals of the Royal College of Surgeons of England 101 (1): 35–39. January 2019. doi:10.1308/rcsann.2018.0149. PMID 30286644. 
  34. ↑ "Olfactory dysfunction in patients with head trauma". Archives of Neurology 54 (9): 1131–1140. September 1997. doi:10.1001/archneur.1997.00550210061014. PMID 9311357. 
  35. ↑ National Research Council (US) Committee on Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants (2009) (in en). Hydrogen Sulfide. National Academies Press (US). https://www.ncbi.nlm.nih.gov/books/NBK219913/. 
  36. ↑ "Olfactory dysfunction in parkinsonism: a general deficit unrelated to neurologic signs, disease stage, or disease duration". Neurology 38 (8): 1237–1244. August 1988. doi:10.1212/WNL.38.8.1237. PMID 3399075. 
  37. ↑ "Loss of olfactory function in dementing disease". Physiology & Behavior 66 (2): 177–182. April 1999. doi:10.1016/S0031-9384(98)00262-5. PMID 10336141. 
  38. ↑ "Olfactory function in chemical workers exposed to acrylate and methacrylate vapors". American Journal of Public Health 79 (5): 613–618. May 1989. doi:10.2105/AJPH.79.5.613. PMID 2784947. 
  39. ↑ "Olfactory impairment after chronic occupational cadmium exposure". Journal of Occupational Medicine. 34 (6): 600–605. June 1992. PMID 1619490. 
  40. ↑ "Olfactory disorders induced by cadmium exposure: a clinical study". International Journal of Occupational Medicine and Environmental Health 11 (3): 235–245. 1998. PMID 9844306. 
  41. ↑ "Smell identification ability: changes with age". Science 226 (4681): 1441–1443. December 1984. doi:10.1126/science.6505700. PMID 6505700. Bibcode: 1984Sci...226.1441D. 
  42. ↑ "Esthesioneuroblastoma". eMedicine. October 30, 2009. http://emedicine.medscape.com/article/278047-overview. 
  43. ↑ "Treatment of postviral olfactory loss with glucocorticoids, Ginkgo biloba, and mometasone nasal spray". Archives of Otolaryngology--Head & Neck Surgery 135 (10): 1000–1004. October 2009. doi:10.1001/archoto.2009.141. PMID 19841338. 
    • Lay summary in: "Study Examines Treatment For Olfactory Loss After Viral Infection". ScienceDaily (Press release). October 21, 2009.
  44. ↑ "Olfactory functions and volumetric measures of orbitofrontal and limbic regions in schizophrenia". Schizophrenia Research 74 (2–3): 149–161. May 2005. doi:10.1016/j.schres.2004.07.010. PMID 15721995. 
  45. ↑ "Isolated neurosarcoidosis presenting as anosmia and visual changes". Otolaryngology--Head and Neck Surgery 117 (6): S183–S186. December 1997. doi:10.1016/S0194-5998(97)70097-4. PMID 9419143. 
  46. ↑ "F.D.A. Warns Against Use of Popular Cold Remedy". New York Times. June 16, 2009. https://www.nytimes.com/2009/06/17/health/policy/17nasal.html. 
  47. ↑ "Dental, visual, auditory and olfactory complications in Paget's disease of bone". Journal of the American Geriatrics Society 43 (12): 1384–1391. December 1995. doi:10.1111/j.1532-5415.1995.tb06618.x. PMID 7490390. 
  48. ↑ "Anosmia following operation for cerebral aneurysms in the anterior circulation". Journal of Neurosurgery 72 (6): 864–865. June 1990. doi:10.3171/jns.1990.72.6.0864. PMID 2338570. 
  49. ↑ "Profound olfactory dysfunction in myasthenia gravis". PLOS ONE 7 (10): e45544. 2012. doi:10.1371/journal.pone.0045544. PMID 23082113. Bibcode: 2012PLoSO...745544L. 
  50. ↑ "Clinical effects of red-bellied black snake (Pseudechis porphyriacus) envenoming and correlation with venom concentrations: Australian Snakebite Project (ASP-11)". The Medical Journal of Australia 193 (11–12): 696–700. December 2010. doi:10.5694/j.1326-5377.2010.tb04108.x. PMID 21143062. 
  51. ↑ "Congenital anosmia". International Journal of Pediatric Otorhinolaryngology 41 (2): 207–214. August 1997. doi:10.1016/S0165-5876(97)00075-X. PMID 9306177. 
  52. ↑ "Appetite and Anosmia". The Lancet 297 (7706): 970. 1971. doi:10.1016/S0140-6736(71)91470-X. 
  53. ↑ "Anosmia". The Laryngoscope 73 (4): 468–473. April 1963. doi:10.1288/00005537-196304000-00012. PMID 13994924. 
  54. ↑ "Nasal Polyps Treatment & Management". Medscape. May 1, 2014. http://emedicine.medscape.com/article/994274-treatment. 
  55. ↑ "Turmeric as a Possible Treatment for COVID-19-Induced Anosmia and Ageusia". Cureus 13 (9): e17829. September 2021. doi:10.7759/cureus.17829. PMID 34660038. 
  56. ↑ "Gene therapy rescues cilia defects and restores olfactory function in a mammalian ciliopathy model". Nature Medicine 18 (9): 1423–1428. September 2012. doi:10.1038/nm.2860. PMID 22941275. 
  57. ↑ "Gene therapy restores sense of smell in mice". BBC News. September 3, 2012. https://www.bbc.co.uk/news/health-19409154. 
  58. ↑ "New chemosensory component in the U.S. National Health and Nutrition Examination Survey (NHANES): first-year results for measured olfactory dysfunction". Reviews in Endocrine & Metabolic Disorders 17 (2): 221–240. June 2016. doi:10.1007/s11154-016-9364-1. PMID 27287364. 
  59. ↑ DeGregory, Lane (30 November 2023). "For decades, a Florida woman had no sense of smell. Can she get it back?" (in en). https://www.tampabay.com/news/health/2023/11/30/regain-lost-sense-smell-florida-anosmia/. 
  60. ↑ Sullivan, Justin (8 Apr 2021). "Ben & Jerry's' Ben Cohen Interview". https://www.delish.com/food-news/a36051690/ben-cohen-ben-jerrys-interview/. 

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