Anosmia - Causes and Symptoms

Definition

Anosmia is the complete loss of smell. Depending on the circumstances, the inability to perceive odors can be permanent or temporary.

Usually, anosmia is the consequence of an intranasal obstruction, which prevents odors from reaching the olfactory area; however, it can also derive from the destruction of the olfactory neuroepithelium or from impairment at any level of the olfactory nerve.

The lack of perception of odors is a common symptom of rhinitis and sinusitis . A previous infection of the upper respiratory tract (especially of the flu type) is implicated in about 14-26% of all cases of hyposmia (partial loss of smell) and anosmia.

Viral rhinitis (or cold) arises abruptly, resulting in a temporary anosmia associated with nasal congestion, watery or purulent nasal secretions, sneezing, low-grade fever and a sense of itching in the throat. Also in sinusitis the loss of smell is temporary; in addition to this symptom, nasal congestion, pain in the paranasal sinuses, watery or purulent discharge, headache, fever and general malaise are associated. In the presence of allergic and vasomotor rhinitis, on the other hand, anosmia is intermittent and occurs due to congestion and prolonged nasal obstruction.

In pediatric age, hypertrophic adenoids can cause anosmia associated with respiratory disorders due to nasal obstruction, rhinolalia, otitis media and hypoacusis. The presence of polyps, on the other hand, can obstruct the nasal cavities, causing a temporary loss of smell.

Anosmia can be induced by the prolonged use of local decongestant drugs, which cause atrophy of the nasal mucosa with damage to the olfactory neuroepithelium. In some cases, the loss of smell is a consequence of a serious pathology (diabetes mellitus, head trauma and nasal and brain tumors).

In the elderly, anosmia can be manifested by the destruction of central pathways in the context of Alzheimer's disease . A noticeable decrease in the sense of smell is in any case part of the normal aging process, which causes the loss of neurons associated with olfactory receptors; these changes are generally evident from 60 years of age.

Other possible causes include nasal, sinus or intracranial surgery and head and neck irradiation. Certain drugs (such as, for example, enalapril, estrogens, naphazoline, phenothiazines and reserpine), smoking habits and exposure to chemical agents and toxins (eg cadmium and manganese) can also contribute to anosmia.