Parosmia
| Parosmia | |
|---|---|
| Other names | Troposmia |
| Symptoms | inability to properly identify an odor's "natural" smell |
Parosmia (from the Greek παρά pará and ὀσμή osmḗ "smell") is a dysfunctional
smell detection characterized by the inability of the brain to correctly identify an odor's "natural" smell.[1] Instead, the natural odor is usually transformed into an unpleasant aroma, typically a "burned", "rotting", "fecal", or "chemical" smell.[2] There can also be rare instances of a pleasant odor called euosmia.[3] The condition was rare and little-researched until it became relatively more widespread since 2020 as a side effect of COVID-19.[4]
Causes
There are numerous diseases with which parosmia is associated. In a case study, Frasnelli et al. examined five patients that endured parosmia or phantosmia, most as a result of
coronavirus disease 2019 as a rare side effect.[6] Common triggers in COVID-19 related parosmia include coffee, chocolate, meat, onion and toothpaste.[7] Exposure to harmful solvents has also been linked to parosmia, specifically by damaging ORNs.[8]
Damage to these neurons could render them unable to correctly encode a signal representing a particular odor, which would send an erroneous signal to the odor processing center, the olfactory bulb. This, in turn, leads to the signal triggering a different smell than the stimulating odor, and thus the patient cannot sync the input and output odors. Damage to ORNs describes a peripheral defect in the pathway, but there are also instances where damage to the processing center in the brain can lead to distorted odors.[citation needed]
Different types of
head trauma could also lead to dysfunctions that relate to what the afflicted brain area controls. In humans, the olfactory bulb is located on the inferior side of the brain. Physical damage to this area would alter how the area processes information in a variety of ways, but there are also diseases that can alter how this area works. If the part of the brain that interprets these input signals is damaged, then a distorted output is possible. This would also lead to parosmia. Temporal lobe epilepsy has led to cases of parosmia, but these were only temporary; the onset of parosmia was a seizure and it typically lasted a week or two after.[9] Parosmia is sometimes associated with Parkinson's disease. Although the specific pathway is undetermined, the lack of dopamine has resulted in documented cases of parosmia and phantosmia.[10]
Diagnosing
One method used to diagnose parosmia is the
MRI
did not reveal any abnormalities; however the parosmia in this case was degenerative, getting worse in time. The authors report that cases of parosmia can predict regeneration of olfactory senses.
Treatment
Symptoms of most patients afflicted with parosmia decrease over time. Although there are instances of parosmia affecting patients for years, this is certainly not the majority of cases. There have been experimental treatments of parosmia with
to the point that the odors are negligible.See also
- Phantosmia, perceiving smells not objectively present
References
- PMID 15723940.
- ^ a b Franselli, J; B.N. Landis; S. Heilmann; B. Hauswald; K.B. Huttenbrink; J.S. Lacroix; D.A. Leopold; T. Hummel (2004). "Clinical presentation of qualitative olfactory dysfunction". Eur Arch Otohinolaryngol. 261: 411–415.
- S2CID 24834566.
- ISSN 0362-4331. Retrieved 2021-06-20.
- PMID 15738120.
- ^ Moss, Alex (2020-08-28). "Covid-19 smell loss 'made meat taste like petrol'". BBC News. Retrieved 2020-08-28.
- ^ "Scientists identify 'trigger molecule' for Covid-related changes to smell". the Guardian. 25 May 2022. Retrieved 28 May 2022.
- PMID 963006.
- S2CID 21513819.
- PMID 24961619.
- S2CID 38532297.
- PMID 895952.
External links
Look up parosmia in Wiktionary, the free dictionary.