Neurology-Online

The taste disorder

introduction

In contrast to the olfactory disorders that are widespread in society, taste disorders are rather rare. Those affected most often complain about a change in the perception of taste. Things are perceived as bitter or metallic more often than usual.

The different forms of taste disorder

Quantitative taste disorders

Hypergeusia: With hypergeusia, one is particularly sensitive to taste stimuli.
Normogeusy: Normogeusy is listed for the sake of completeness. There is no change in the taste sensation here. Accordingly, it is the normal state.
Hypogeusia: If one suffers from hypogeusia, the sense of taste is reduced. Partial ageusia: As the name suggests, partial ageusia only affects individual taste qualities.
Total ageusia: In the case of total ageusia, none of the four taste qualities sweet, sour, salty and bitter can be felt any more.

Qualitative taste disorders

For the most part, taste disturbances are qualitative. These include parageusia and phantogeusia, which experience has shown to be limited in time, that is, they disappear again after a time interval of about 10 months.

Parageusie: In the context of a parageusie, tastes are perceived differently. For example, something that normally tastes sweet is suddenly perceived as bitter. Flavors are usually perceived as bitter, sour or metallic in the context of a parageusia, which is why the parageusia brings about a considerable reduction in the quality of life.
Phantogeusia: A certain taste is felt in the absence of a stimulus (for example a food). All of these impairments can appear separately; however, those affected often suffer from combinations of quantitative and qualitative taste disorders.

Bitter taste disorder

There are many different causes that can lead to a taste disturbance in which those affected perceive a bitter taste. The most common cause of this is taking medication. The drugs that primarily produce a bitter taste include the antibiotic clarithromycin, the anti-diabetes drug metformin and Vit-D tablets.

Furthermore, inflammation or other diseases of the gums can also lead to such a taste perception. In addition, many pregnant women complain of a regular bitter taste that disappears after a few hours. Other reasons for a bitter taste disorder are the presence of reflux disease, a fungal infection, zinc deficiency and inadequate oral hygiene.

Salty taste disturbance

The most common cause of the perception of a salty taste is a change in the pH value of the body, i.e. a change in the acid-base balance. This is most common in people who are dehydrated, which means that they don't have enough water in their bodies. This lack of water can result from insufficient water consumption, but also from increased excretion, as can be the case, for example, with severe diarrhea.

Furthermore, a salty taste can indicate a lack of vitamins or trace elements such as iron. As already described above, drugs, especially certain antibiotics, can lead to salty taste disorders. In addition, a disturbed function of the salivary glands can lead to an increased salt content of the saliva and thus to such a perception.

Sweet taste disorder

It is very rare for humans to experience an isolated sweet taste disorder. The most common cause of such a disorder is that the general taste perception declines sharply with age; this is known as hypoguesia.However, this process is least pronounced on the taste receptors that are responsible for sweet taste. With hypoguesia in old age, for example, people can only taste sweet, which they then perceive as an increased perception of sweetness.

The causes of a taste disorder

The causes of a taste disorder can be divided into three major groups. A distinction is made between epithelial causes, neural causes and central causes.

Epithelial causes: Our taste organs, the taste papillae and taste buds, which are imperceptible to the human eye, are responsible for taste. If the taste organs are damaged, one speaks of an epithelial cause. The direct damage can be due to various things such as drugs (penicillin, ACE inhibitors, cytostatics used in chemotherapy, and many other drugs). Radiation, atrophic glossitis (inflammation of the tongue), hypothyroidism (underactive thyroid function) and pernicious anemia (anemia caused by a vitamin B12 deficiency) are other epithelial causes of a taste disorder.

Nerve causes: Nerve fibers are responsible for transmitting signals from the taste organs to certain areas in our brain so that we can even taste something. If the nerves responsible (cranial nerve VII, IX or X) are damaged, this can manifest itself in a taste disturbance. Damage to the nerves can be unintentional in the context of ENT operations, by tumors, by fractures of the skull or by a neuritis (Nerve inflammation).

Central causes: Diseases such as post-traumatic diseases are among the central causes of taste disorders Anosmia Ageusia Syndrome (simultaneous loss of smell and taste after a head trauma) or brain tumors.

Medicines as the cause

There are a number of medications which, via different mechanisms of action, can impair the sense of taste. Antidepressants, for example, can lead to a pronounced dry mouth. Due to the reduced saliva production, the function of the taste buds of the tongue can be disturbed and taste can no longer be perceived as intensely. Other drugs, such as the antibiotic metronidazole, can also have a direct influence on the sensory cells and thus lead to a reduction in the sense of taste.

Chemotherapy drugs in particular, such as cisplatin, can lead to a complete loss of taste. Some drugs that are mainly used in the treatment of high blood pressure continue to have such side effects. These include ACE inhibitors such as enalapril, diuretics (especially hydrochlothiazide) and calcium antangonists (nifedipine).
There are also drugs that cause us to perceive certain tastes that are actually not there. One speaks of a so-called dysgusia. Examples of this are the drug allopurinol, vitamin D or many contrast media that can produce a metallic taste on the tongue.

Most medication changes in taste is not a permanent side effect. It can usually go away again by switching to another preparation or medication.

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Side effects of antidepressants
Side effects of ACE inhibitors

Cortisone as the cause

One of the many side effects of taking cortisone is a change in taste. This is especially the case with higher doses, such as those used in shock therapy

Most patients who have changes in their taste during cortisone therapy report having a metallic or bitter taste in their mouths, which can, however, be masked by sucking candy. This side effect usually lasts several days after the administration of cortisone, but then disappears on its own.

Find out more about the side effects of cortisone.

Multiple sclerosis as the cause

Most patients with multiple sclerosis report impaired sensory perception as the disease progresses. So white about. 5-20% of those affected have taste disorders. This can be the result of damage to the brain area that is responsible for the sense of taste, but it can also be the result of damage to the nerves that are responsible for taste and smell.

The taste disturbance primarily affects the perception of sweet and salty tastes. This symptom occurs in most patients as part of a relapse and disappears in many patients at an early stage of the disease with shock therapy with cortisone. Usually, there is a permanent reduction or loss of taste perception only in a late stage of the disease.

Find out all about the topic here: Multiple sclerosis.

The removal of tonsils as the cause

The occurrence of taste disturbances is a rare complication that can occur as part of an almond removal. This is mainly due to the fact that during the operation the tongue is strongly pushed away and this can cause damage. Furthermore, the taste buds in the area of the base of the tongue are greatly stretched during the operation.

After such an operation, the taste disturbances usually only exist for a few days, as the nerve endings have to recover from the strong irritation. Only in very rare cases is there a permanent reduction or even complete loss of taste perception.

More information about a Almond removal you'll find here.

Diagnosing a taste disorder

If a taste disturbance is suspected, the doctor should take a detailed anamnesis, as important information about a possible cause can be obtained here. Following the history and examination of the patient, the presence of a taste disorder should be checked with tests.
Testing of taste: There are two types of tests to check our taste buds. On the one hand, there are the so-called subjective test procedures, which require that the patient is fit and can provide information about what is tasted, and on the other hand, there are objective test procedures that are used when the person concerned cannot cooperate himself and cannot provide any information, such as it is the case with young children or people with dementia.

Our taste buds can be checked using a variety of tests. There is the so-called three-drop method, with which the threshold can be determined from which one perceives a certain taste. To do this, the person concerned has to find out from three drops administered, which drop tastes like something specific and what this drop tastes like. If you don't taste anything at first, the concentration of the flavor is increased until the taste is perceived. Of course, there are also tests that check whether certain flavors can be identified. For this purpose, flavors are administered in liquid (spray or drops) or solid form (e.g. wafers) and a check is carried out to determine whether the tastes can be recognized by the patient.

There is also the option of having those affected indicate the perceived strength of a certain taste. There are certain scales for this from weak to strong. In addition, volume levels can also be used to compare the perceived intensity. The taste can also be checked with the help of other methods and a taste disorder can be objectified. One of these methods aims at the measurement of brain waves after stimulation by means of a flavor substance. It is called an electroencephalogram (EEG).

So-called electrogustometry can also provide information about a neural defect. Here, the electrical perception threshold is determined on both sides of the tongue through the stimulation with currents in the microampere (µA) range. In electrogustometry, it is always important to compare the sides with the healthy side of the tongue, as the electrical perception threshold varies greatly from person to person and so it cannot be compared between people. Central causes of a taste disturbance can be determined by means of magnetic resonance imaging (MRI) of the skull are revealed.

The therapy options for a taste disorder

The treatment options for a taste disorder are limited. For this reason, the cause of the taste disturbance should be carefully searched for and treatment should then be sought or the triggering drug should be discontinued or changed if possible.

In order to get to the bottom of the cause, it makes sense to see an ENT doctor or neurologist. In terms of therapy, it is primarily the qualitative taste disorders that are difficult. No suitable therapy can be offered to these. The only positive thing is the spontaneous regression in a large number of cases after about 10 months. In the meantime, there have also been studies that have shown an improvement in symptoms through the consumption of zinc.