Anosmia (loss of smell): symptoms, causes and treatment

Losing a sense is always the cause of significant discomfort and difficulties in daily life. People who suffer from blindness or deafness need certain help to be able to fully carry out their lives, not without encountering obstacles along the way.

However, losing the sense of taste or touch also often has a very negative impact on people.

In this article we are going to talk about the loss of the ability to smell, that is, anosmia. This little-known disability is not something that should be considered insignificant, as it can even pose a threat to the person affected by this condition.

• Related article: "Olfactory system: reception, transduction and brain pathways"

What is anosmia?

Anosmia is the inability to perceive the smell or, also, it can be significant decrease in olfactory ability.

This problem can have a variable duration, being in many cases something temporary, due to a cold or some temporary problem in the respiratory tract. In other cases, the cause may be more serious and cause anosmia permanently, such as the genetic factor and having suffered an accident with brain involvement, especially if the brain structures responsible for the sense of sense have been damaged smell.

Thus, the cause of this problem can be as much in the nostrils as in the nerves and the brain. This can cause different types of anosmia, affecting the ability to smell from one or both nostrils. When you can't feel odors in one nostril alone, we talk about unilateral anosmia.

Terms related to anosmia are hyposmia, which is a decreased ability to smell, and hyperosmia, which is when you smell more intensely. It may be the case that it is anosmic only for certain types of odors. When anosmia occurs from birth, it is called congenital anosmia.

How do we smell?

To better understand how anosmia can occur, we must first understand how our sense of smell works. Odor is the sensation resulting from inhaling particles that adhere to receptors in the mucous membranes of the nose. These receptors are found in the yellow pituitary gland. The receptors are capable of detecting up to seven essential odors: ethereal, musky, floral, minty, spicy, camphorous, and putrid. The combination of these allow to perceive up to 10,000 different fragrances.

When the receptor is stimulated, a nerve impulse is sent through the olfactory nerve (first cranial nerve) that carries information to the olfactory bulb. From there, the information goes to the hypothalamus and then to the cerebral cortex, which is where the smell becomes conscious.

If the nasal mucosa, nerves or brain structures involved in odor perception have been affected, anosmia can occur to different degrees and with different treatment options if it is possible to remedy it.

Associated symptoms

The main symptom and by which anosmia is identified is the absence of the perception of olfactory stimuli. The way in which this loss of the ability to smell occurs can occur in multiple ways, either abruptly and insidiously or progressively.

The ability to detect odors is not as developed in humans as it is in other species; however, it has evolutionary purposes and its loss entails disadvantages that affect the day-to-day life of anosmic people.

Spoiled food, gas leaks and fires are situations that can be identified by smell. It is for this reason that not being able to detect them poses a real risk to the person, since they are unknowingly exposing themselves to a potentially deadly threat.

People who have lost the ability to sense smell in an acquired way lose their appetite, given that they cannot perceive a stimulus of the food that makes them attractive, such as their good smell. This can lead to excessive weight loss and malnutrition.

Besides, in cases in which this problem occurs in an acquired form, depressive symptoms occur, because olfactory stimuli associated with emotional memories can no longer be felt, which makes the person feel that they have lost part of their ability to remember. In addition, loss of libido can occur when sexually arousing odors are not detected.

Possible causes

There are multiple causes that may be behind the appearance of anosmia, in addition to being able to affect different structures involved in the sense of smell. Temporary loss of the ability to smell may be due to infectious and inflammatory problemssuch as colds, allergic reactions, acute sinusitis, hay fever, flu, polyps, tumors, and bone deformities inside the nose.

In the cases in which this medical condition occurs in a serious and permanent way, behind it may be having suffered a cranioencephalic accident that has damaged brain structures or have inherited this problem. Anosmia is associated with normal aging and also occurs in early stages of dementia.

This can be a symptom in the Alzheimer disease, Huntington, Parkinson and Niemann-Pick, in addition to appearing in multiple system atrophy, schizophrenia, Korsakov syndrome and other serious disorders. It can also be a consequence of some problems at the brain level that may be behind suffering from anosmia: brain surgery, aneurysms, traumatic brain injuries...

Kallman syndrome is the most frequent cause of congenital anosmia. In this case, it could be due to the fact that in the embryogenesis of the olfactory placode there is a lack of olfactory epithelium that is replaced by respiratory epithelium in the abnormal development of the embryo.

The abuse of nasal sprays can affect the nasal mucosa, both nasal vasoconstriction sprays and those used as a symptomatic remedy for some forms of allergy. Although its occasional use does not pose a risk, its abuse should be avoided and, in case of long-lasting nasal inflammation, consult a professional to evaluate other options. Nasal surgery, such as rhinoplasty, can also cause this problem to appear. Exposure to certain chemicals, such as insecticides and solvents, in addition to suffering from zinc deficiency, it has been associated with the appearance of anosmia.

• You may be interested in: "Kallman syndrome: symptoms, causes and treatment"

Diagnosis

When it comes to finding out if a person may be suffering from anosmia, it is necessary to carry out an interview, since, although It may seem surprising, there are anosmic people who do not know that they suffer from this problem, especially if they have it congenital

To detect this problem acetylcysteine ​​test is used. The person is also asked if they have suffered any type of injury or if they have abused certain substances that are inserted through the nose. In addition, he wonders if he has suffered respiratory problems, especially in the nose. An examination of the inside of the nostrils is performed using a rhinoscope.

Thus, a neurological evaluation is carried out to see if any nerve has been damaged after an accident. The cases of people who have suffered car accidents or of another type who have begun to suffer the symptoms of unilateral anosmia are more common than it is thought.

It is usual that cases of congenital anosmia are not properly detected, mainly because the person has never smelled in his life and, therefore, does not have the experience of what the sense of smell is.

Treatment

Depending on the cause that has caused the anosmia, there will be different treatment. Anosmia due to brain lesions is hardly treatable, but the one caused by inflammation of the nasal mucosa is. In this second case, glucocorticoids, antihistamines, anti-inflammatories and antibiotics are used.

On the other hand, anosmias caused by nasal obstruction or the appearance of polyps and tumors will require surgical intervention. Certain losses of the ability to smell are due to nutritional deficiencies, such as a lack of zinc, they are corrected by providing the deficient substance.

Bibliographic references:

• Roper A. H., BrownR. h. (2007). Smell and taste disorders. In: Roper A. H., BrownR. h. (Eds). Principles of Neurology, (195-202). Mexico: McGraw-Hill Interamericana.
• Soler G. m. (2002). Congenital anosmia: review and clinical cases. Argentine Federation of Otorhinolaryngology Societies, 1: 55-60.