Ageusia

From Wikipedia, the free encyclopedia
Ageusia
Pronunciation
SpecialtyNeurology

Ageusia (from negative prefix a- and Ancient Greek γεῦσις geûsis 'taste') is the loss of taste functions of the tongue, particularly the inability to detect sweetness, sourness, bitterness, saltiness, and umami (meaning 'savory taste'). It is sometimes confused with anosmia – a loss of the sense of smell. True ageusia is relatively rare compared to hypogeusia – a partial loss of taste – and dysgeusia – a distortion or alteration of taste.[1][2]

Even though ageusia is considered relatively rare it can impact individuals of any age or demographic. Due to the COVID-19 pandemic, there has been an increase in reported cases of ageusia, making it more commonly diagnosed than before.[3]

Causes[edit]

Ageusia can arise from various factors:[4][2][5][3]

Ageusia can further be influenced by lifestyle choices such as smoking, obesity, and inadequate nutrition. Additionally, conditions like diabetes and hypertension can play a role in contributing to ageusia, as well as some nutrient deficiencies, especially in zinc and vitamin B-12.[3]

Neurological damage[edit]

Tissue damage to the nerves that support the tongue can cause ageusia, especially damage to the chorda tympani nerve and the glossopharyngeal nerve. The chorda tympani nerve passes taste for the front two-thirds of the tongue and the glossopharyngeal nerve passes taste for the back third of the tongue. The lingual nerve (which is a branch of the trigeminal V3 nerve, but carries taste sensation back to the chorda tympani nerve to the geniculate ganglion of the facial nerve) can also be damaged during otologic surgery, causing a feeling of metal taste.[citation needed]

COVID-19[edit]

Main article: Symptoms of COVID-19 § Loss of taste and chemesthesis

Ageusia and anosmia in COVID-19 patients occur independently of nasal obstruction or other rhinitis symptoms, likely attributed to direct viral damage to olfactory and gustatory receptors[6]

Anosmia has become a more notable symptom frequently seen in COVID-19 cases and taste issues are often associated with this diagnosis. New research on COVID-19 and taste dysfunction suggests that taste difficulties arise independently and separate from smell issues. This compelling feature of how SARS-CoV-2 affects the nervous system selectively could explain how taste and smell issues appear in people with the virus.[7]

Studies investigating the prevalence of taste disorders stemming from the COVID-19 pandemic indicate that a wide range of individuals were impacted, with some experiencing these issues more severely than others:[7]

Patients[7] %
European Patients 55.2%
North American Patients 61.0%
Asian Patients 27.1%
South American Patients 29.5%
Australian Patients 25.0%

Patients with ageusia observed in 28.0% of patients, hypogeusia in about 33.5%, and dysgeusia in about 41.3% of patients.[7]

In April 2020, 88% of a series of over 400 COVID-19 disease patients in Europe were reported to report gustatory dysfunction (86% reported olfactory dysfunction).[8]

An individual with ageusia related to a COVID-19 infection may recover within one to two weeks, but without treatment, the infection can persist.[3]

Proposed Mechanisms of Infection[edit]

Recent research has hinted at a connection between the distribution of taste cells and ACE2 receptors in ageusia. It's been observed that there's a higher proportion of ACE2-positive cells among taste cells, suggesting a possible pathway for SARS-CoV-2 to invade and cause ageusia in affected individuals.[9]

Ageusia could possibly occur due to changes in the abundance or lack of saliva that can eventually cause damage to the cells on the tongue's surface.[10]

Saliva and Ageusia[edit]

Taste perception starts when molecules interact with receptors on taste buds. These taste buds are primarily located on the tongue's papillae near the minor salivary glands. When food enters the mouth, saliva helps in dissolving the food particles and surrounds the taste buds. This kickstarts the process of taste perception.[11]

Saliva is essential in taste sensation, partially through its interaction with various receptors.[11]

Zinc[edit]

Research on zinc deficiency has linked it to hyposalivation and alterations in taste perception. One significant factor tied to taste bud abnormalities in relation to zinc deficiency is the lack of a zinc-binding protein called Gustin. Reduced levels of zinc in saliva have been associated with hypogeusia or ageusia conditions.[11]

Low levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in saliva have also been linked to an impaired taste sensation.[11]

Diagnosis[edit]

Ageusia is usually diagnosed by an otolaryngologist, also known as an ear nose and throat doctor(ENT).[3] These individuals can evaluate a patient's loss of taste among other things. To do this, a specialist will look into any other factors that could be causing ageusia, such as examining the head, nose, ears, and mouth. As well as imaging of the head and neck, to help further identify or eliminate the presence of tumors, focal lesions, or any type of injury that could possibly be affecting any taste-related networks.[4] [12][13]An otolaryngologist can also conduct a series of tests to assess the severity of ageusia, which includes identifying specific tastes that the patient can sense or recognize.[12][13]

An example of a test used by researchers and doctors is electrogustometry. This test involves applying mild electric currents to specific tongue areas, to assess taste sensitivity in patients exhibiting ageusia and its symptoms.[4]

Treatment[edit]

Treatment for ageusia varies depending on its cause, whether it stems from an illness, medication, traumatic injury or other causes.

In cases where ageusia is triggered by medication, reducing or discontinuing the medication may alleviate the symptoms. However, if ageusia is linked to an underlying illness or trauma, addressing and treating the root cause of the condition is necessary to manage the ageusia effectively..[4]

Antihistamines, decongestions and antibiotics can be used to treat ageusia.[3]

Complications[edit]

Ageusia, even though not life-threatening, can significantly impact day to day comfort.[4] Many individuals affected by taste disorders can feel isolated in their experiences, which leads to feelings of depression, social withdrawal, and unhealthy eating habits. Such eating habits may involve either insufficient food intake or excessive consumption of sour or sweet foods. This dietary pattern could pose risks, particularly for individuals with diabetes.[4]

References[edit]

  1. ^ "Taste Disorders". Massachusetts Eye and Ear Infirmary. Retrieved 30 November 2018.
  2. ^ a b c Hummel T, Landis BN, Hüttenbrink KB (2011). "Smell and taste disorders". GMS Current Topics in Otorhinolaryngology, Head and Neck Surgery. 10: Doc04. doi:10.3205/cto000077. PMC 3341581. PMID 22558054.
  3. ^ a b c d e f g h "Ageusia (Loss of Sense of Taste): Definition, Causes & Treatment". Cleveland Clinic. Retrieved 2024-04-14.
  4. ^ a b c d e f g h i j k l m n Doty, R.L. (2014). Aminoff, Michael J. (ed.). Ageusia (Encyclopedia of the Neurological Sciences 2nd ed.). Academic Press. pp. 69–71. doi:10.1016/B978-0-12-385157-4.01112-X. ISBN 9780123851581.
  5. ^ a b Al-Ani RM, Acharya D (August 2020). "Prevalence of Anosmia and Ageusia in Patients with COVID-19 at a Primary Health Center, Doha, Qatar". Indian Journal of Otolaryngology and Head and Neck Surgery. 74 (Suppl 2): 2703–2709. doi:10.1007/s12070-020-02064-9. PMC 7435125. PMID 32837952.
  6. ^ Vaira, Luigi; Salzano; Deiana; De Riu (2020). "Anosmia and Ageusia: Common Findings in COVID-19 Patients". The Laryngoscope © 2020 the American Laryngological, Rhinological and Otological Society, Inc. 130 (7): 2. doi:10.1002/lary.28692. PMC 7228304. PMID 32237238. ProQuest 2398912838 – via ProQuest.
  7. ^ a b c d Saniasiaya, Jeyasakthy; Islam, Md Asiful; Abdullah, Baharudin (July 2021). "Prevalence and Characteristics of Taste Disorders in Cases of COVID‐19: A Meta‐analysis of 29,349 Patients". Otolaryngology–Head and Neck Surgery. 165 (1): 33–42. doi:10.1177/0194599820981018. ISSN 0194-5998.
  8. ^ Lechien JR, Chiesa-Estomba CM, De Siati DR, Horoi M, Le Bon SD, Rodriguez A, et al. (August 2020). "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. doi:10.1007/s00405-020-05965-1. PMC 7134551. PMID 32253535.
  9. ^ Tanasa, Ingrid; Manciuic, Carmen; Carauleanu, Alexandru; Navolan, Dan; Bohiltea, Roxana; Nemescu, Dragos. "Anosmia and Ageusia associated with coronavirus infection (COVID‑19) - what is known?". Experimental and Therapeutic Medicine. 20 (3). Spandidos Publications: 2344–2347. doi:10.3892/etm.2020.8808. ISSN 1792-1015.
  10. ^ Jeyasakthy, Saniasiaya MD, MMed; Islam, Md Asiful; Abdullah, Baharudin MBBS, MMed (2021-12-15). "Prevalence and Characteristics of Taste Disorders in Cases of COVID-19: A Meta-analysis of 29,349 Patients". Otolaryngology-Head and Neck Surgery. 165 (1). American Academy of Otolaryngology-Head and Neck Surgery Foundation: 33–42. doi:10.1177/0194599820981018.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ^ a b c d Abduljabbar, Tariq; Alhamdan, Rana S.; Al Deeb, M.; AlAali, K.; Vohra, F. (2020). "Association of Salivary Content Alteration and Early Ageusia Symptoms in COVID-19 Infections: A Systematic Review". European journal of dentistry. 01 (14). doi:10.1055/s-0040-1716986. PMID 33242917.
  12. ^ a b "Ageusia: Causes, Symptoms And Treatment". Netmeds. Retrieved 2021-03-26.
  13. ^ a b "Taste Disorders: Get Facts About Causes, Treatment & Symptoms". MedicineNet. Retrieved 2021-03-26.

External links[edit]

Retrieved from "https://en.wikipedia.org/w/index.php?title=Ageusia&oldid=1221972908"