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Dysosmia

Original Editor - Youssef Maged Saadeldin Mohamed

Top Contributors - Youssef Maged Saadeldin Mohamed  

Introduction

Dysosmia comes from Greek nomenclature Dys- meaning bad, osm- meaning smell, ia- a termination in Greek meaning quality or condition.[1]

Dysosmia is an umbrella term that coves qualitative olfactory disorders, in which there is a change in the quality of olfaction, and it describes two main olfactory disorders; Phantosmia and Parosmia (Troposmia) [2]

Parosmia is a distortion in smell perception in the presence of an odour,ie: smelling a flower but perception of another odour (usually unpleasant) like (gas- ciggarettes-feces-rotten-burn) smell, where as,[3]

Phantosmia is a distortion in smell perception in the absence of an odour, which is why it's usually called olfactory hallucination.[3]


Aetiology

Anatomy of the Structures Involved in Smell (Olfaction).

Olfactory dysfunction is mainly divided into 2 factors

Conductive losses secondary to obstruction of the nasal airflow to the olfactory bulb[4]

Sensory losses secondary to damage or dysfunction of any part of the olfactory tract from olfactory receptors to the olfactory bulb till the olfactory processing part of the brain [4]

Diseases that could affect the olfactory tree include

  1. Alzheimer's Disease [5]
  2. Upper respiratory infections URI [6]
  3. toxins
  4. congenital disorders
  5. Multiple Sclerosis (MS)[7]
  6. Epilepsy[8]
  7. Parkinson's[9][10]
  8. Traumatic Brain Injury[11] [12] [13]

Symptoms

Parosmia signs can vary greatly from person to person. For some, the disease may seem mild and quickly go away, while others may feel that it is more severe and may last for a long time.[14]

In most cases, symptoms of parosmia appear after one has recovered from an illness or infection.[14]

If you have parosmia, you might: [14]

  1. Find it hard to be able to tell or identify certain smells around you.
  2. Smell unpleasant, usually disagreeable odors, mostly around meals, on the contrary.
  3. You may find that the scents that used to be pleasurable now seem overpowering or repulsive.

Examination

History taking and subjective examination:

Take history for:

  1. Any recent URI
  2. Any trauma to the head or problem with sinuses
  3. Exposure to toxins
  4. Nature and severity of altered olfaction and type of triggers

Olfactory function tests

Olfactory dysfunction can either be qualitative (defect in quality) or quantitative (defect in strength).[15]

Function tests mainly focus on testing the quantitative part of olfaction, while history taking focuses on the qualitative part.[15]

The process involves presenting an olfactory probe to the patient's nostrils and documenting their response, known as psychophysical testing. [15]

These tests require patient cooperation and understanding. Olfactory tests are divided into odor threshold tests and suprathreshold tests[15]

Odour Threshold tests

Used for assessing peripheral olfactory ability.(Conductive and sensorineural function of the nose)[15]

Sniffin’ Sticks Test is a psychological semi-objective test that allows assessment of patient's sense of smell using 3 subtests: threshold test, identification test, and discrimination test. [16]

Suprathreshold odour tests

Used for assessing processing centres of olfaction in the brain

University of Pennsylvania Smell Identification Test (UPSIT) is a 40-item scratch-and-sniff olfactory test designed to assess a patient's ability to identify common odours. [17]

Treatment

Many treatments have been proposed for postviral smell disorders. These treatments include pharmacological treatment such as oral and/or topical corticosteroids, caroverine, alpha lipoic acid, vitamin A, minocycline, zinc sulfate, and nonpharmacological treatment such as olfactory training and nasal saline irrigation.[18] [19]

However, there is no standard protocol for the treatment of dysosmia and more research is needed to reach an appropriate protocol.

Olfactory training

Olfactory training therapy is suggested to be the first-line treatment for olfactory dysfunction, as it is an inexpensive method with no serious side effects. It intends to strengthen the olfactory recovery according to the neuronal plasticity of the olfactory system, and also it may increase cognitive processing of the incomplete sensory information. It is performed by patients themselves, 2 times a day over at least 3 months, exposed to 4 intensive odors (phenyl ethyl alcohol: rose, eucalyptol: eucalyptus, citronellal: lemon, and eugenol: cloves)[18]


Corticosteroid treatment

Corticosteroids treatment either topical or oral are the most used method in patients with olfactory dysfunction. However, the efficacy of systemic corticosteroids on postinfectious olfactory disorder is debatable. The duration of illness, safety concerns, age, and general condition of the patients could affect the decision of treatment with systemic corticosteroids. [18]

The use of oral or nasal steroids for treatment of post-COVID 19 smell loss may lower the rate of occurrence of dysosmia in recovered patients later on.

Combination therapy of olfactory training and prescription of corticosteroids was found to be more effective . [19]

[20]

This video explains the different types of olfactory dysfunction

[21]

In this video, you will learn how olfactory training is practised.

References

  1. ↑ https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095738343
  2. ↑ Frasnelli J, Landis BN, Heilmann S, Hauswald B, Hüttenbrink KB, Lacroix JS, Leopold DA, Hummel T. Clinical presentation of qualitative olfactory dysfunction. Eur Arch Otorhinolaryngol. 2004 Aug;261(7):411-5.
  3. ↑ 3.0 3.1 Bonfils P, Avan P, Faulcon P, Malinvaud D. Distorted odorant perception: analysis of a series of 56 patients with parosmia. Arch Otolaryngol Head Neck Surg. 2005 Feb;131(2):107-12. doi: 10.1001/archotol.131.2.107. PMID: 15723940.
  4. ↑ 4.0 4.1 Wrobel, Bozena & Leopold, Donald. (2005). Clinical Assessment of Patients with Smell and Taste Disorders. Otolaryngologic clinics of North America. 37. 1127-42. 10.1016/j.otc.2004.06.010.
  5. ↑ Richard L. Doty, Patricio F. Reyes, Tom Gregor, Presence of both odor identification and detection deficits in alzheimer's disease,
  6. ↑ Abdel-Aziz M, Azab N. Dysosmia in Recovered COVID-19 Patients. J Craniofac Surg. 2023 May 1;34(3):843-844. doi: 10.1097/SCS.0000000000009008. Epub 2022 Sep 22. PMID: 36136915; PMCID: PMC10128425.
  7. ↑ Arife Çimen Atalar, Yüksel Erdal, Betül Tekin, Muhammed Yıldız, Özlem Akdoğan, Ufuk Emre, Olfactory dysfunction in multiple sclerosis, Multiple Sclerosis and Related Disorders, Volume 21, 2018,
  8. ↑ Bozena B. Wrobel, Donald A. Leopold, Clinical assessment of patients with smell and taste disorders, Otolaryngologic Clinics of North America, Volume 37, Issue 6, 2004,(https://www.sciencedirect.com/science/article/pii/S003066650400132X)
  9. ↑ Landis BN, Burkhard PR. Phantosmias and Parkinson disease. Archives of Neurology. 2008 Sep 8;65(9):1237-9.
  10. ↑ Hirsch AR. Parkinsonism: the hyposmia and phantosmia connection. Archives of neurology. 2009 Apr 1;66(4):538-42.
  11. ↑ Jacobi G, Ritz A, Emrich R. Cranial nerve damage after paediatric head trauma: a long-term follow-up study of 741 cases. Acta Paediatrica Hungarica. 1986 Jan 1;27(3):173-87.
  12. ↑ Hong SC, Leopold DA, Oliverio PJ, Benson ML, Mellits D, Quaskey SA, Zinreich SJ. Relation between CT scan findings and human sense of smell. Otolaryngology--Head and Neck Surgery. 1998 Feb;118(2):183-6.
  13. ↑ Schechter PJ, Henkin RI. Abnormalities of taste and smell after head trauma. Journal of Neurology, Neurosurgery & Psychiatry. 1974 Jul 1;37(7):802-10.
  14. ↑ 14.0 14.1 14.2 Cavazzana A, Larsson M, Münch M, Hähner A, Hummel T. Postinfectious olfactory loss: A retrospective study on 791 patients. Laryngoscope. 2018 Jan;128(1):10-15. doi: 10.1002/lary.26606. Epub 2017 May 29. PMID: 28556265.
  15. ↑ 15.0 15.1 15.2 15.3 15.4 Whitcroft KL, Cuevas M, Haehner A, Hummel T. Patterns of olfactory impairment reflect underlying disease etiology. Laryngoscope. 2017 Feb;127(2):291-295
  16. ↑ C. Rumeau, D.T. Nguyen, R. Jankowski, How to assess olfactory performance with the Sniffin’ Sticks test®, European Annals of Otorhinolaryngology, Head and Neck Diseases, Volume 133, Issue 3, 2016
  17. ↑ Doty RL, Shaman P, Dann M. Development of the University of Pennsylvania Smell Identification Test: a standardized microencapsulated test of olfactory function. Physiol Behav. 1984 Mar;32(3):489-502. doi: 10.1016/0031-9384(84)90269-5. PMID: 6463130.
  18. ↑ 18.0 18.1 18.2 Kanjanaumporn J, Aeumjaturapat S, Snidvongs K, Seresirikachorn K, Chusakul S. Smell and taste dysfunction in patients with SARS-CoV-2 infection: A review of epidemiology, pathogenesis, prognosis, and treatment options. Asian Pacific Journal of Allergy and Immunology. 2020 Jun 1;38(2):69-77.
  19. ↑ 19.0 19.1 Le Bon SD, Konopnicki D, Pisarski N, Prunier L, Lechien JR, Horoi M. Efficacy and safety of oral corticosteroids and olfactory training in the management of COVID-19-related loss of smell. European Archives of Oto-rhino-laryngology. 2021 Aug;278:3113-7.
  20. ↑ https://www.youtube.com/watch?v=AUvUNzkO_k0
  21. ↑ https://www.youtube.com/watch?v=Qrr0so6pFOs
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