How does cardboard taste

What disturbs the sense of smell and taste?

An impaired sense of smell and taste means a significant reduction in the quality of life for the patient concerned. However, the family doctor often finds it difficult to classify the complaints, which are often vaguely described, and how to treat them. Because the first thing to do is to determine whether the sense of taste, smell or the oral sense of touch is disturbed. The following article deals with the etiology of these disorders based on a specific case and provides the general practitioner with a concept for his diagnosis.

A 14-year-old girl has been complaining of a subjectively strong odor and taste disorder for three years. It states that it can only taste the main flavors (sweet, sour, salty, bitter), but no finer differences or spices. As a toddler, she was treated symptomatically or with antibiotics for frequent upper respiratory infections, and when she was at kindergarten, the tonsils and tonsils had to be removed. Two years ago a readenotomy and the reduction of the turbinates were carried out - unfortunately without any influence on the symptoms.

A recent MRI scan of the paranasal sinuses revealed chronic frontal sinusitis; the allergological evaluation was negative. After trauma to the upper jaw three years ago, a root canal treatment of two incisors in the right upper jaw was performed due to inflammation. Sinus infections are currently treated with a steroid-containing nasal spray. So far, none of the measures have led to a normalization of the disturbed taste.

Uncertain patient statements, time-consuming diagnostics, unsatisfactory therapy results: Labeled in this way, taste disorders not only lead to a wallflower existence in everyday medical practice, but also in many specialist practices. Wrongly from the point of view of those affected, because they often suffer severely from the specific limitation of their experience.

For the general practitioner, the problem begins with the description of the complaint: changes in the perception of smell and / or taste can often only be described vaguely by many of those affected due to the redundancy of the corresponding sensory organs. This subjective problem of perception of the patient is offset by limited objective measurement methods, which are often only available in special departments. The therapeutic options that can then be offered are at least as limited. On the basis of the casuistry described at the beginning, aspects relevant to general practitioners in the case of taste disorders are to be presented.

The problem

In everyday parlance, taste is the sum of the impressions made when eating and drinking. However, if you look closely, it describes three senses [1]: the sense of taste, the sense of smell and the oral sense of touch. Only about 5% of all patients with taste disorders actually suffer from a taste disorder [2]. Usually it is olfactory disorders that lead to a change in the perception of aromas and thus to the subjectively disturbed taste sensation.

The gourmet is above all a fine nose

The olfactory epithelium is located in the roof of the main nasal cavity (olfactory fissure), on both sides approximately at the level of the upper turbinate and the corresponding nasal septum area. In this way, a meaningful two-way contact takes place (Fig. 1). When inhaled, the odorous substance molecules are transported from the nasal entrance (orthonasal smelling) to the olfactory receptors. When exhaling through the nose, odorous substances from food reach the olfactory fissure via the oral cavity and nasopharynx (retronasal smelling). The odorous substances are detected there and the information is transmitted via the olfactory tract to the ipsilateral olfactory cortex.

In addition to the sensory (“aromatic odor components”), hedonically documented identification performance by the olfactory nerve, the nose also recognizes sensitive qualities (the stinging of acetic acid, the tingling of menthol, cold and warmth of the food) of food and odorous breath. This guardian function is performed by two branches of the trigeminal nerve, predominantly in the anterior part of the main nasal cavity, and is intended to prevent the inhalation of pollutants at the airway port. The throat at the entrance to the digestive tract has a similar distribution of tasks. The organ of taste not only decides about the palatability of our food, but also warns of harmful or indigestible substances through important reflexes (disgust and gag reflex).

According to current knowledge, the actual sense of taste comprises five qualities: sweet, sour, bitter, salty and umami. Umami could also be called "spicy" and describes a sensation that is triggered by the flavor enhancer glutamate. The primary receptors are taste buds, which in adults are restricted to the soft palate and tongue. The direction of taste from the front two thirds of the tongue is taken over by afferent fibers of the chorda tympani (from the facial nerve) running through the middle ear. The lingual branch of the trigeminal nerve transmits pain, but also the temperature and texture of food from the same region. The posterior third of the tongue is innervated by the glossopharyngeal nerve, the base of the tongue and hypopharynx by the vagus nerve. Gustatory sensations of the palate are transmitted through the superficial petrosal nerve (from the facial nerve).

Also consider local causes

In order for smells and flavors to arrive at the receptors and be deciphered, the mechanical and chemo-physical prerequisites must be right: the patient's nose must be free in the area of ​​the upper nasal passage so that the odorous air can reach the olfactory epithelium (Fig. 2 and 3) . As the air you breathe mainly flows through the lower and middle nasal passages, subjectively free nasal breathing is no guarantee that the olfactory fissure is also free. Diseases of the nasal mucosa or viral and medicinal influences can also cause local damage to the olfactory receptors.

In order for flavorings to be released, food has to be chopped up and processed. This requires a functioning chewing apparatus and sufficient saliva flow. But the tongue receptors must be innervated intact, free and receptive to their work. Oral cavity or tongue diseases (Fig. 4) can also lead to functional impairment, as can mechanical injuries to the afferent nerves through iatrogenic interventions (tonsillectomy, middle ear operations, dental or maxillofacial surgery).

What does that mean for our case?

In the case of patients with taste disorders, the family doctor should proceed in three stages:

  • At the beginning there is an attempt to narrow down the leading deficit on the basis of subjective patient information. Assessments of the taste sensation are easier, since most of those affected can easily state whether they feel the classic taste qualities and other temperature or tactile sensations (cold, warm, rough, hard) on the tongue and in the oral cavity. It is much more difficult with the more complex sense of smell. In doing so, specific questions must be asked about the impression of certain odorous substances that are well known from everyday life. This first analysis should then be objectified by an olfactory and gustatory examination by the specialist. The patient from our case history probably has a predominant olfactory disorder, since the main taste qualities (performance of the tongue) are recognized, but not finer aromas (performance of the nose).
  • In the case of an olfactory disorder, the olfactory pathways are thoroughly investigated (Fig. 1): Not only the region surrounding the olfactory fissure (upper nasal passage, ethmoid bone region), but also the nasopharynx must be shown by means of diagnostic imaging and / or endoscopy. Corresponding causes (e.g. nasal polyps, adenoid tissue in the nasopharynx, inflammation of the paranasal sinuses) should then be treated causally step by step.
  • The aspect of "oral health" is not unimportant: the appropriate chopping of food and the oral sense of touch are essential for sensitive tasting. For this reason, patients with taste disorders must be presented to the dentist to rule out diseases of the teeth, the gums or chewing. This is all the more true if intervening dental measures have taken place in the past (see our case).

1. Landis BN, Just T. What is behind taste disorders? CME 2011; 3 (1): 7-14
2. Hummel Th, Landis BN, Hüttenbrink K-B. Disorders of smell and taste. Laryngo-Rhino-Otol 2011; 90 (Supplement 1): S44-S55

Specialist in general medicine - sports medicine
Specialist in ear, nose and throat medicine