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 'pleasant/savory taste'). It is sometimes confused with
anosmia – a loss of the
sense of
smell
Smell may refer to;
* Odor, airborne molecules perceived as a scent or aroma
* Sense of smell, the scent also known scientifically as olfaction
* "Smells" (''Bottom''), an episode of ''Bottom''
* The Smell, a music venue in Los Angeles, Californ ...
. Because the tongue can only indicate texture and differentiate between sweet, sour, bitter, salty, and umami, most of what is perceived as the sense of taste is actually derived from smell. True ageusia is relatively rare compared to
hypogeusia – a partial loss of taste – and
dysgeusia – a distortion or alteration of taste.
Causes
The main causes of taste disorders are head trauma, infections of upper respiratory tract, exposure to toxic substances, iatrogenic causes, medicines, glossodynia ("
burning mouth syndrome (BMS)")
[ and COVID-19.
Head trauma can cause lesions in regions of the central nervous system which are involved in processing taste stimuli, including thalamus, brain stem, and temporal lobes; it can also cause damage to neurological pathways involved in transmission of taste stimuli.
]
Neurological damage
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.
Problems with the endocrine system
Deficiency of vitamin B3 ( niacin) and zinc can cause problems with the endocrine system, which may cause taste loss or alteration. Disorders of the endocrine system, such as Cushing's syndrome, hypothyroidism
Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormone. It can cause a number of symptoms, such as po ...
and diabetes mellitus, can cause similar problems. Ageusia can also be caused by medicinal side-effect
In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
s from antirheumatic drugs such as penicillamine, antiproliferative drugs such as cisplatin, ACE inhibitor
Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of hypertension, high blood pressure and heart failure. They work by causing relaxation of blood vessels as well as a decrease i ...
s, and other drugs including azelastine
Azelastine, sold under the brand name Optivar among others, is a H1 receptor-blocking medication primarily used as a nasal spray to treat allergic rhinitis (hay fever) and as eye drops for allergic conjunctivitis. Other uses may include asthma ...
, clarithromycin, terbinafine, and zopiclone.
COVID-19
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
The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste.
In humans, it ...
dysfunction). Research suggests that the loss of taste resulting from COVID-19 might be caused by impairments to the gustatory (and olfactory) system.
Other causes
Local damage and inflammation that interferes with the taste buds or local nervous system, such as that stemming from radiation therapy, glossitis, tobacco use, or the wearing of dentures, can also cause ageusia. Other known causes include loss of taste sensitivity from aging
Ageing ( BE) or aging ( AE) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In ...
(causing a difficulty detecting salty or bitter taste), anxiety disorder
Anxiety disorders are a cluster of mental disorders characterized by significant and uncontrollable feelings of anxiety and fear such that a person's social, occupational, and personal function are significantly impaired. Anxiety may cause physi ...
, cancer, kidney failure and liver failure.
Diagnosis
Aguesia is diagnosed by an otolaryngologist, who 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. 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.
References
External links
* MedTerms Online Medical Dictionary
"Ageusia"
Retrieved April 15, 2005.
* Family Practice Notebook
Retrieved April 15, 2005.
* Massachusetts Eye and Ear Infirmary
"Taste Disorders"
Retrieved May 26, 2010.
{{Taste
Gustatory system
Laryngology
Symptoms and signs of mental disorders
ru:Агевзия