Patients suffering from anosmia have completely lost the ability to perceive odors. None of the more than 10000 known possible variations of odors can be perceived anymore. The different forms of anosmia are not considered rare clinical pictures.
What is anosmia?
All odors are perceived and processed in the brain, this happens via the so-called olfactory cells of the nasal roof. From there, the information is transmitted as a nerve impulse via the olfactory nerves to the cerebral cortex. In anosmia, this physiological process is either disturbed or can no longer take place at all. How the exact conversion of odor information into odor perception occurs in the brain has not been definitively clarified to date. The part of the brain responsible for the perception of odors is also responsible for the processing of emotions, among other things. In everyday life, the lack of olfactory perception results in a variety of restrictions for those affected, combined with a significantly reduced quality of life. Since the sense of smell is also closely linked to the sense of taste, this also causes problems. If, for example, a piece of chocolate is put in the mouth, the affected person can only taste the sweetness, but not the fine nuances of the chocolate aroma. According to WHO estimates, tens of thousands of people worldwide contract anosmia every year. Depending on the cause, anosmia can be a temporary disorder or a permanent, lifelong limitation. According to the regulations of the Social Security Code, those affected can have a degree of disability determined by a doctor once they have reached a certain level of anosmia.
Causes
The reasons for the occurrence of anosmia can be very different. In total anosmia, the function of the olfactory nerves has completely failed. No odors can then be perceived at all. If there is selective anosmia, then the affected person can no longer perceive only certain odors. This clinical picture is not even noticed by the mostly older patients for a long time. In addition, a distinction must be made between peripheral and central anosmia, depending on the location and extent of nerve damage:
- If only the olfactory cells are damaged, it is a peripheral anosmia.
- If the olfactory perceptions can not be processed in the brain, physicians speak of a central anosmia due to the brain damage.
The main cause of all types of anosmia is a degeneration of nerve or brain cells due to increasing age. Especially after the 60th year of life, the ability to smell decreases significantly in both sexes. However, this is a process that takes years and is rather gradual. It is quite certain that inhaled smoking and excessive alcohol consumption also lead to a strong impairment of the ability to smell. However, the resulting nerve damage is fully reversible to a certain extent.
Symptoms, complaints, and signs
Particularly in the attenuated peripheral forms of olfactory impairment due to nerve degeneration, the changes are not even noticed for a long time. In central anosmia, the symptoms may appear more quickly if, for example, tumor growth is the cause. If there is an obstruction of nasal breathing, the ability to perceive odors is also restricted. This is because the gas particles that convey the odor then only partially reach the olfactory cells. In the case of olfactory cell damage, patients complain of a false smell, also known as olfactory illusion, as well as a bilateral loss of the ability to smell. This process is perceived as very unpleasant by those affected. Since taste perception is always affected in anosmia, sufferers often also complain of loss of appetite or depressive moods. Even one’s own body odor can no longer be perceived, which can also lead to social restrictions under certain circumstances.
Diagnosis and course
The suspected diagnosis is made by the family doctor, and the final diagnosis is made by the ENT specialist. To make the diagnosis, the complete nasal mucosa is examined using a rhinoscope. This is a flexible nasal endoscope with an additional light source, so the doctor can easily assess the condition of the nasal mucosa. In addition, the sense of smell must be checked in detail to confirm the diagnosis.This is done subjectively by the presentation of various odorants and objectively by the method of so-called electronic reaction olfactometry. If central anosmia is suspected, additional imaging methods such as CT or MRI are used.
Complications
Congenital anosmia does not usually result in complications. In contrast, sudden onset anosmia is often associated with several problems. First, a sudden absence of the sense of smell results in a loss of quality of life. The psychological consequences range from depression and anxiety disorders to fear of unpleasant self-smell and severe behavioral disorders. In the long term, anosmia reduces general well-being; the former quality of life is usually not regained in the event of a sudden illness. Physically, anosmia can quickly lead to malnutrition and subsequently to deficiency symptoms and further complaints. Often, affected persons oversalt or over-season food in order to enhance the taste experience. This can lead to damage to the taste buds, but also to various health problems. Due to the lack of a sense of smell, there is also a risk that toxic or spoiled food will be consumed, which can result in food poisoning, for example. Danger to life exists if escaping gases or fires cannot be perceived due to anosmia. Moreover, the absence of the sense of smell can lead to problems in everyday life and at work, often causing severe psychological and emotional stress. A sudden onset of anosmia must therefore always be clarified by a physician.
When should you go to the doctor?
If anosmia is suspected, the patient should talk to his or her family doctor promptly. Often, an impaired sense of smell is due to a harmless cause that can be diagnosed and treated quickly. However, if it is anosmia, a quick diagnosis is necessary, since a tumor or a degenerative nerve or brain disease may be the cause. People over the age of 60 in particular should go to the doctor with complaints of the sense of smell. The ability to smell decreases significantly with age and can cause anosmia in the long term – but if diagnosed in time, this can be treated well. For this reason, at-risk groups in particular, such as heavy smokers and people who regularly drink alcohol, should have an impaired sense of smell examined. Since anosmia is often not immediately perceived by those affected themselves, self-tests are recommended. If the sense of smell or taste is perceived as weakened, a visit to the doctor is recommended. Other contacts are the ENT physician and, depending on the cause, various internists.
Treatment and therapy
Treatment of any form of anosmia must always be cause-related. In many cases, the therapy is considered costly and difficult, and for a complete healing process, the patient will usually have to be very patient. In the essential forms of anosmia, i.e. without a clearly identifiable cause, a self-healing tendency is often observed. If inflammation or polyps of the nasal mucous membranes or paranasal sinuses are the cause, the anosmia usually disappears as soon as the inflammatory process has also subsided. Medications can also cause severe olfactory disturbances as a side effect; in these cases, discontinuation of the medication or its replacement with substitute preparations is necessary. In the case of central anosmia, regaining full olfactory ability is unfortunately not possible in most cases due to irreversible nerve damage. Influenza viruses can also cause severe, irreversible damage to the olfactory cells, leading to anosmia that is resistant to therapy.
Outlook and prognosis
The prognosis of anosmia depends on its cause and location. If inflammation of the nasal mucosa or sinusitis is the reason for the lack of olfactory perception, the chances of affected individuals regaining their sense of smell are good. Thus, olfactory perception usually improves on its own after a severe cold. Chronic mucosal inflammation or allergies can be treated with medications that provide decongestion. If the anosmia is due to polyps, surgical removal helps to restore the sense of smell. If anosmia occurs as a side effect of medications such as antibiotics, these simply need to be discontinued.However, if the anosmia is due to a traumatic brain injury, the prognosis is worse. Only about one in five regains their olfactory sense. If central anosmia is present, for example due to dementia or Parkinson’s disease, attention should be focused on treating the severe underlying disease. According to studies, anosmics who regularly participate in olfactory training have a good prognosis for complete or at least partial recovery from the olfactory disorder. Experts suggest that the six-month training regrows olfactory cells. In some cases, anosmia is congenital or its cause is not identifiable. Spontaneous recovery is rare, but cannot be ruled out in principle.
Prevention
Once anosmia has been diagnosed, affected individuals are at risk of also being unable to detect dangerous odors from toxic fumes, fire, or spoiled food. It is therefore helpful to inform the family environment about the disease. In order to prevent age-related creeping anosmia, it may be useful to have the olfactory system checked at least annually in suspected cases. To prevent stimulant-induced anosmia, alcohol and nicotine consumption should be avoided.
Follow-up
The extent to which follow-up care is necessary depends on whether or not the sense of smell was restored by initial therapy. If the outcome is positive, there should be no further symptoms. Follow-up care is not necessary. However, this does not mean that anosmia cannot develop a second time. There is no immunity. The known causes can cause a loss of smell again. The situation is different if those affected do not fully regain their sense of smell or do not regain it at all after initial treatment. Depending on the cause, doctors administer medication or perform another operation. Scientists assume that human olfactory cells will grow back if they are sufficiently trained. For this purpose, patients are given so-called smelling pens, which they have to sniff several times a day. Anosmia cannot be prevented by preventive measures. This is not where follow-up care comes in. Rather, it attempts to eliminate the causes of the loss of smell through appropriate procedures and to restore the sense of smell with suitable therapy. If this is not successful, it has serious consequences for the sufferer. The consumption of food is no longer possible as usual. In social contact, many stimuli are missing.
What you can do yourself
The loss of the sense of smell significantly limits the quality of life and can even be dangerous in some situations. Often, the importance of the sense of smell for coping with everyday life is underestimated and only the stimulating sensory perception is missed. However, affected persons must realize that they can no longer identify contaminated food as they used to. Great caution is therefore required when storing perishable food. If in doubt, food should rather be disposed of, as food poisoning can become very dangerous. People who live alone or regularly stay alone at home should also bear in mind that they can no longer perceive an apartment fire olfactorily. It is therefore important to install a sufficient number of smoke detectors and to regularly check that they are working properly. Affected persons are often insecure in their social interactions with others because they can no longer perceive whether they smell of sweat on hot summer days, suffer from bad breath or have put on too much perfume or aftershave. Here, affected individuals should seek out a confidant at work or in other groups where they regularly exercise to point out any faux pas.