Definition: what is anosmia?
Anosmia corresponds to the complete or partial loss of the sense of smell and can be temporary or permanent. “It took the Covid-19 epidemic for the French to discover that the sense of smell is useless!“says Jean-Michel Maillard, founder four years ago ofAnosmia.org, an association that helps victims of olfactory disorders. If it is mainly benign (hence the lack of research on the subject), this symptom can be very disabling on a daily basis (feeling of ill-being, eating disorders, security problem, poor lifestyle). It can affect anyone, children as well as adults.
Anosmia was revealed a characteristic symptom of infection with the new coronavirus. Inflammatory consequence or brain damage: scientists have not yet elucidated how the Covid attacks the sense of smell. But he is not the only one likely to put him in danger, at any age. Olfaction can be affected by various disorders and its loss can be total, lasting, or even irreversible., resulting in a disability that is as painful as it is invisible. But “the earlier anosmia is detected, the better quality of life can be improved“, reassures Dr. Robert Chhuor, ENT surgeon.
What are the symptoms of anosmia?
“At the early stage of the disease, the loss of smell described by patients is often sudden onset, complete and associated with an alteration in taste and flavor perception.“, indicates the HAS. This sudden loss is often associated with an edema of the olfactory epithelium, preventing any odor from reaching the sensory cells. Once the edema disappears, the sense of smell recovers naturally.
However, some symptoms may persist beyond a month, including:
- Impaired detection, hyposmia (i.e. partial anosmia);
- An impairment of identification (I do not recognize);
- A distortion of the perception of flavors and smells, parosmia. Frequent during neurosensory recovery, they have a rather good prognosis;
- Fluctuations in the sense of smell, during the same day or over several weeks;
- Nasal discomfort or a feeling of nasal obstruction.
Anosmia: what are the causes of loss of smell?
The sense of smell can be altered at two levels of the pathway that normally allows the olfactory bulbs, located at the top of the nasal cavity, to pick up odorous molecules in the air from a rose or dirty socks, then to transform this chemical information into electrical message, an influx which then carries it to the brain where the smell will be identified.
At the first level, the molecules may not reach the sensitive area of the nose where they must come into contact with the olfactory cells. The problem can also be located higher up, at the level of nerve transmission, affecting the circuit that conducts the smell from the olfactory cells to the brain, via the olfactory nerve: a lesion in one of these three places (nasal cavity, olfactory cells and olfactory bulb) renders one unable to “smell”.
In some (rare) cases, we speak of congenital anosmia, that is to say that it is present from birth.
In all cases, the alteration is accompanied by a decrease or loss of taste (ageusia) : if the taste buds that cover the tongue can detect sweet, salty, acid or bitter, 80% of the taste depends on the sense of smell, by nasal retro-olfaction, when the food is in the mouth.
Anosmia: what diseases (other than Covid) are responsible?
At age 80, 80% of people have faulty olfactory recognition and half are anosmic. But the sense of smell can suffer at any age, and “in 15 to 20% of cases, we do not know what causes its loss“, warns Dr. Wissame El Bakkouri, ENT doctor.
Apart from these mysterious cases, several pathologies can explain the appearance of more or less severe and lasting disorders, explains Dr. Chhuor:
- A tumor : even if sinus or nasal cavity cancers are fortunately rare (3% of ENT cancers).
- Head trauma: 18% of the loss of smell are consecutive to a shock, if it shears the filaments of the olfactory nerves – unable to regenerate – this makes the transmission of odors to the brain impossible and the handicap irreversible.
- Polyps: they are responsible for 5% of partial loss of olfaction: invading the nasal mucosa, they cause local inflammation which hinders the uptake of odours.
- Allergic rhinitis or a virus (acute rhinitis, flu): they can also, more often than one might think, cause a more or less severe disorder, “if it destroys the olfactory tissue, damaging the smell circuitry at the first level“, says Dr. Chhuor.
Neurological diseases like Parkinson’s disease can also be responsible for the loss of smell.
Finally, 25% of losses of smell are linked to viral sequelae, which may prove to be persistent: “5% of patients never fully recover, without identifying the predisposing factors.”
Loss of smell: how is the diagnosis made?
If you no longer feel anything, or much less, consultation with an ENT specialist is required. First step to find the cause, the interrogation which makes it possible to trace possible shock, viral affection, inhalation of toxic product, or even radiotherapy.
Smoking also contributes to this, “tobacco also plays on local inflammation“, warns Dr. Chhuor. A nasal fibroscopy will be performed in the office in search of polyps.
A scanner can be prescribed to deepen the examination of the sinuses, and more rarely the MRI if the doctor wants to visualize the sinuses and the brain. Long – and not rated by Social Security –, the olfactometry examination, which consists of inhaling around forty bottles of odors to determine precisely which ones the patient smells and/or identifies, is unfortunately only carried out in a experimental, regrets Dr. El Bakkouri.
Loss of smell: how is it treated?
Both ENT and patients deplore this: if the loss of smell first requires treating the cause, there is no miracle cure and generally few treatmentsexcept for nasal polyposis.
“As these are chronic conditions, it is difficult to explain to the patient that he will not recover from them.“, observes Dr. Chhuor, but they can be reduced. The inflammation, which causes a permanent obstruction of the nose, can be reduced, in first intention, by corticoids in spray, then, if it persists, by regular cures ( two per year maximum) of oral corticosteroids, and finally by surgery. If the loss of smell lasts more than 15 days, nose washes with saline solution can be offered to the patient, combined with olfactory rehabilitation.
Some cases may now, as a last resort, be eligible for biotherapy, by monthly injection of antibodies. In all cases, and whatever their origin, “the loss of smell is treated above all by olfactory rehabilitation, which improves the quality of life“, says Dr. El Bakkouri. A background training, which consists of stimulating the lost or diminished sense and olfactory recognition, by inhaling 1 to 2 times a day 4 to 6 smellsincluding vanilla beans, coffee, cloves, lemon essential oil, wine vinegar, curry, cinnamon, and rose and lavender essential oils.
To help victims of smell disorders, Anosmie.org offers a free 12-week program of this type on its site, developed with a neuroscientist.
Our Experts:
- Dr Robert Chhuor, ENT surgeon at the Atlantic Polyclinic, in Saint-Herblain (44)
- Dr. Wissame El Bakkouri, ENT doctor at the Rothschild Foundation Hospital in Paris