Loss Of Smell

Loss of smell (anosmia) can be banal symptoms accompanying some upper respiratory tract infections, but on the other hand sometimes it can be related to severe diseases. The list of possible causes is based on knowledge of the anatomical structures of the olfactory tract.

The basic apparatus of the olfactory system are sensory cells located in the upper part of the nasal mucosa. These cells send out little nerve fibers that create paired olfactory nerve that transmits smell information into olfactory brain center (It is an interesting fact that the brain center for smell is relatively close to the center of emotions). The olfactory disorders are associated with disruption of some parts of the olfactory neural pathway.

Causes

Local infections

Upper respiratory infections affecting nasal cavity (usually common cold) may be associated with swelling of the mucous membranes and disruption of olfactory sensory cells. It also dampens the taste because olfactory sensation is its important part. After the infection withdraws, smell sense quickly returns. The sense of smell may be impaired even in sinusitis. This is usually a bacterial infection that has to be solved by administration of antibiotics or by sinus puncture.

Allergy

Allergic rhinitis may (like common cold) cause swelling of the mucous membrane and disrupt smell sense. Smell usually returns very quickly after withdrawal of the allergic reaction.

Nasal polyps

Nasal polyps develop in cases of chronic inflammation in the nasal cavity (both infectious and allergic). They may cause obstruction to airflow and also impair the olfaction.

Injuries

Head injuries associated with injury of frontal part of brain may induce olfactory nerve damage. Loss of smell is the logical consequence.

Tumors

Brain tumors growing near olfactory nerves may damaged neural transmission and disrupt the olfactory sense. This is typical for otherwise benign meningiomas. There should be always tumor suspicion in people of advanced age who have lost smell sense without any previous upper respiratory tract infection or injury.

Rare genetic syndromes

There are some rare genetic inherited disorders related to smell disorders, Kallmann syndrome may be named as an example.

Diagnostic approach

Short-term loss of smell in common cold does not have to be examined. Prolonged smell loss is however a sign that should be investigated by an otolaryngologist. When there is found no clear reason or when there is a head injury or neurological symptoms present, it is advisable to perform a neurological examination that can include some imaging methods such as brain computed tomography or magnetic resonance imaging.