Taste disorders (dysgeusia)

PHYSIOLOGICAL BASES:

Taste strict sense is the sense that perceives the taste of dissolved substances in saliva.

The perception of each individual flavor has a prime seat: the bitter and acid are especially seen in the soft palate, salty the anterior two thirds of the tongue and the sweet on any language.

Sensory receptors are the taste buds, worn by taste buds.

These are located mainly on the tongue, but it also exists in the rest of the pharynx, larynx and esophagus. The sensory signal is conveyed by different nerves depending on the localization of receptors: the anterior two-thirds of the tongue are innervated via Wrisberg, the posterior third of the glossopharyngeal and vagus by the epiglottis.

The influx is going to taste solitary tract nucleus in the brainstem and the ventral posterior medial nucleus of the thalamus, and finally it is transmitted to the parietal cortex.

Note that the taste sensations are physiologically mingled with olfactory perceptions of molecules through the choanae (flavors). These elements allow to better understand what conditions can make patients feel the taste disorder, or dysgeusia.

DIAGNOSTIC:

Clinical examination is intended to clarify the taste complaint and to move towards one of the many causes of dysgeusia.

Examination taste:

The management of patients dysgueusiques faces many obstacles. The former are related to their limits introspection and semantic difficulties. Is there a disorder of taste or rather a disorder of smell? If so on what (s) flavor (s) he carries? Many subjects confuse bitter and acid. Dysgeusia it is quantitative (ageusia, hypogeusia, hypergueusie) or qualitative (paragueusie)?

In the latter case, is there a distortion of taste of one or more substances (aliagueusie) or taste perception without stimulus (fantogueusie)? These semiotic nuances are often difficult to obtain but can direct the etiological investigation.Thus, paragueusies and fantogueusie “metal” or bitter are often associated with a drug case. Moreover, the examination assesses the achievement of the intensity. Indeed, taste loss or a significant decline in the perception of sweet taste evoke a severe deterioration of taste.

General interrogation and physical examination:

Advanced age is a major cause of hypogeusia, due to the physiological depletion of taste buds and frequent xerostomia. Furthermore, in the elderly, other causes of dysgeusia are often associated: the iatrogenic (over 20% of cases), kidney failure, Alzheimer’s disease and deficiencies (zinc, iron, B vitamins and A, etc.).

Neurological diseases, trauma and ENT surgery and diabetes mellitus should be investigated because they can affect the taste pathways. Hormonal status should be clarified: menopause, pregnancy, hypothyroidism and diabetes are often known consultants.

Evaluating the overall condition is helpful.

Weight loss and weakness may reflect the impact of dysgeusia or underlying disease: diabetes, malabsorption, HIV infection, amyloidosis.

Neurological examination explores the cranial nerves, tracks dementia related deficits with a stroke or a combined degeneration of the cord could indicate a vitamin B12 deficiency.

The ENT examination is essential. This research cholesteatoma otitis, sinusitis, rhinitis, oral candidiasis, dry syndrome, macroglossia (hypothyroidism, amyloidosis, etc.).

The examination of mucous membranes, skin, hair and nails can detect signs suggesting iron deficiency or vitamin B group or a Cushing’s disease or amyloidosis (bruising of the eyelids).

The cardiovascular examination may also bring clues: bradycardia did look for other signs of hypothyroidism, orthostatic hypotension may be associated with an unrecognized diabetes or much more rarely with amyloidosis.

Abdominal examination for signs of liver disease (HVB, HVC, alcoholism), a recent constipation (hypothyroidism) or diarrhea (amylose, malabsorption, HIV infection, etc.).

Diagnostic tests:

Upon completion of the clinical examination, a cause is found in most cases. The use of complementary tests is not systematic.

Conventional additional tests:

These non-systematic reviews aim to confirm a suspected cause by clinical examination.

Additional examinations taste:

This is the chemical gustométrie and électrogustométrie.

They allow objectify dysgeusia, assess its severity and possibly

topography endobuccal deficit.

Chemical gustométrie is to taste the reference product solutions at various concentrations to assess the patient’s detection threshold.

The électrogustométrie determines the threshold of perception of an electrical stimulus applied to the tongue. It is not qualitative and less physiological and chemical gustométrie but allows selective explore specific areas of the tongue. It is also simpler to implement and more finely quantitative.

ETIOLOGY:

Main causes of dysgeusia:

The causes of dysgeusia are numerous.

Dysgeusia main drugs responsible for:

TREATMENT:

The treatment is always one of cause when there is: stopping a drug or intoxication, micronutrient supplementation or vitamin, treatment of digestive disease, infectious, endocrine, neurological or metabolic.