Refers to the distortion of the sense of taste.
Often associated with ageusia, the complete lack of taste, and hypogeusia, which is the decrease in taste sensitivity.
An alteration in taste may be a secondary process in various disease states, or it may be a primary process.
The sense of taste is tied together with other sensory systems.
Common causes include chemotherapy, treatment with albuterol, and zinc deficiency.
The sense of taste is based on the detection of chemicals by specialized taste cells in the mouth, with each taste bud containing receptor cells in contact with afferent nerves.
Several afferent nerves innervate a single taste bud, while a single efferent fiber innervates several taste buds.
Taste buds are composed of four different types of cells, and each taste bud has at least 30 to 80 cells.
Type I cells are thinly shaped, usually in the periphery of other cells. They also contain high amounts of chromatin. Type II cells have prominent nuclei and nucleoli with much less chromatin than Type I cells. Type III cells have multiple mitochondria and large vesicles. Type I, II, and III cells also contain synapses. Type IV cells are normally rooted at the posterior end of the taste bud.
Every cell in the taste bud forms microvilli at the ends.
Fungiform papillae are present on the anterior portion of the tongue.
Circumvallate papillae and foliate papillae are found on the posterior portion of the tongue.
The salivary glands keep the taste buds moist with saliva.
Taste buds are present in the mouth, throat, larynx, and esophagus and are replaced every ten days.
Type I cells are thinly shaped, usually in the periphery of other cells.
Type II cells have prominent nuclei and nucleoli.
Type III cells have multiple mitochondria and large vesicles.
Type I, II, and III cells also contain synapses.
Type IV cells are normally rooted at the posterior end of the taste bud.
Every cell in the taste bud forms microvilli at the ends.
Fungiform papillae are present on the anterior portion of the tongue.
Circumvallate papillae and foliate papillae are found on the posterior portion of the tongue.
The salivary glands keep the taste buds moist with saliva.
Taste buds are present in the mouth, throat, larynx, and esophagus and are replaced every ten days.
Treatments include artificial saliva, pilocarpine, zinc supplementation, alterations in drug therapy, and alpha lipoic acid.
The sense of taste is conveyed via three of the twelve cranial nerves.
The chorda tympani is responsible for taste sensations from the anterior two thirds of the tongue.
The glossopharyngeal nerve (IX) is responsible for taste sensations from the posterior one third of the tongue.
A branch of the vagus nerve (X) carries some taste sensations from the back of the oral cavity.
Alterations in the sense of taste is usually manifested as a metallic taste.
The duration of the symptoms depends on the cause.
If dysgeusia is due to gum disease, dental plaque, medication, or a short-term condition such as a cold, it will disappear when cause is removed.
Dysguesia due to neural lesions in the taste pathway may be a permanent process.
Gustatory dysfunction is rare compared to olfactory disorders.
Gustatory dysfunction disorders are difficult to evaluate and diagnose because gustatory functions are associated with the sense of smell, the somatosensory system, and the perception of pain.
Evaluation of dysguesia includes inquiry about: chewing, oral pain, oral hygiene, salivation, swallowing, chewing, previous ear infections, and gastrointestinal problems, presence of other associated illnesses such as diabetes mellitus, hypothyroidism, or malignancy.
Diagnosis of etiology of dysguesia includes a clinical examination is conducted and of the tongue and the oral cavity, nasal cavity and the ear canal.
Gustatory testing may further classify the extent of the process and can measure the sense of taste.
Gustatory testing can performed either as a whole-mouth or regional test.
In regional testing, 20 to 50 µL of liquid stimulus is presented to the anterior and posterior tongue using a pipette, filter-paper disks, or cotton swabs.
In whole mouth testing, small quantities of solution are swished the solution around in the mouth.
Threshold tests for sucrose (sweet), citric acid (sour), sodium chloride (salty), and quinine or caffeine (bitter) are frequently performed.
Suprathreshold tests provide intensities of taste stimuli above threshold levels and assess ability to differentiate between different intensities of taste and to estimate the magnitude of suprathreshold loss of taste.
The administration of chemicals to the tongue, electrogustometry, can be used to report sour or metallic sensations similar to those associated with touching both poles of a live battery to the tongue, but there is poor correlation between electrically and chemically induced tests.
Reflex tests may identify abnormalities in the nerve-to-brainstem pathways: the blink reflex may be used to evaluate the integrity of the trigeminal nerve–pontine brainstem–facial nerve pathway, which may play a role in gustatory function.
Structural imaging is routinely used to investigate lesions in the taste pathway.
Magnetic resonance imaging allows direct visualization of the cranial nerves to investigate lesions in the taste pathway,
Analysis of mucosal blood flow in the oral cavity and assessment of autonomous cardiovascular system useful in the diagnosis of autonomic nervous system disorders in burning mouth syndrome and in inborn disorders of metabolism both associated with gustatory dysfunction.
Cultures may also be used when fungal or bacterial infections are suspected.
Saliva constitutes the environment of taste receptors, including the ability of transport of tastes to the receptor and protection of the taste receptor.
Saliva evaluation involves sialometry and sialochemistry and electron microscopy of taste receptors may indicate pathological changes in the taste buds.
A major cause of dysgeusia is chemotherapy, for cancer, which induces mucositis, oral infection, and salivary gland dysfunction.
Oral mucositis consists of inflammation of the mouth, along with sores and ulcers in the tissues.
Chemotherapy can cause mucosal infection, which may result in a decrease in saliva.
Approximately 50% of chemotherapy patients suffer from either dysgeusia or another form of taste impairment.
The mechanism of chemotherapy-induced dysgeusia is unknown.
Radiation therapy reduces salivary tissues.
Saliva interacts with and protects the taste receptors in the mouth, and mediates sour and sweet tastes through bicarbonate ions and glutamate, respectively.
The taste of salt occurs when sodium chloride levels surpass the concentration in the saliva.
Taste bud distortions may give rise to dysgeusia.
Taste buds in patients suffering from this taste disorder have fewer microvilli than normal, and the nucleus and cytoplasm are reduced.
Zinc deficiency is associated with dysgeusia as it is partly responsible for the repair and production of taste buds.
Zinc somehow interacts with carbonic anhydrase an enzyme affecting the concentration of gustin, which is linked to the production of taste buds.
Patients treated with zinc have an elevation in calcium concentration in the saliva., and taste buds rely on calcium receptors.
Zinc is a cofactor for alkaline phosphatase, the most abundant enzyme in taste bud membranes.
Zinc is a component of a parotid salivary protein important to the development and maintenance of normal taste buds.
H1-antihistamines can cause dysgeusia.
Hundreds of drugs can affect taste.
The sodium channels linked to taste receptors can be inhibited by amiloride.
The production of new taste buds and saliva can be impeded by antiproliferative agents.
Drug traces in saliva can give rise to a metallic flavor in the mouth and include lithium carbonate and tetracyclines.
Sulfhydryl containing agents including penicillamine and captopril, may react with zinc and cause deficiency..
ACE inhibitors that prevent the production of angiotensin IIhave been linked.
Xerostomia can cause dysgeusia as normal salivary flow and concentration are necessary for taste.
Glossopharyngeal nerve damage can cause dysgeusia, as can injury to the pons, thalamus, and midbrain, all of which compose the gustatory pathway.
Patients with bladder obstruction may experience dysgeusia as the areas responsible for urinary system and taste in the pons and cerebral cortex are close in proximity.
Idiopathic dysgeusia is very common.
Many factors may contribute to this taste disorder: gastric reflux, lead poisoning, diabetes mellitus, pine nuts, pesticides damage to the peripheral nerves, injury to the chorda tympani branch of the facial nerve,
Dysguesia may follow laryngoscopy, tonsillectomy and be experienced with the burning mouth syndrome, and with menopause.
Medications have been linked to approximately 25% of all cases of dysgeusia.
Xerostomia, a side effect of many drugs can lead to the development of taste disturbances such as dysgeusia.
Artificial saliva natural saliva by lubricating and protecting the mouth but does not provide any digestive or enzymatic benefits.
Pilocarpine is a cholinergic drug with neurotransmitter acetylcholine. features and increases in saliva flow is effective in improving taste bud function.
Approximately one half of drug-related taste distortions are caused by a zinc deficiency, and many medications are bind zinc preventing it from functioning properly.
Zinc supplementation may be a beneficial treatment for dysgeusia if there are low levels of zinc in the blood serum.
Alpha lipoic acid (ALA) is an antioxidant that may be a potential treatment for patients with dysguesia.
Management includes: using non-metallic silverware, avoiding metallic or bitter tasting foods, increasing the consumption of foods high in protein, flavoring foods with spices and seasonings, serving foods cold in order to reduce any unpleasant taste or odor, frequently brushing one’s teeth and utilizing mouthwash, or using sialogogues such as chewing sugar-free gum or sour-tasting drops that stimulate the productivity of saliva.
Taste of food can be improved through means other than taste, such as texture, aroma, temperature, and color.
Can lead to weight loss, malnutrition, impaired immunity, and a decline in health.
The elderly are at risk for taste disturbances increasing the chances of developing depression, loss of appetite, and extreme weight loss.
In patients undergoing chemotherapy, taste distortions can make compliance with treatment difficult.