Evaluation of olfactory loss

Diseases

Summary

Olfactory loss has been linked to a variety of causes and can profoundly influence a patient's quality of life.

Epidemiology

It is estimated that functional anosmia has a prevalence of approximately 5% of the general population.[1] Studies suggest that the prevalence of olfactory impairment in the adult population ranges from 0.6% in those aged <35 years to 13.9% among those aged ≥65 years (depending on the test method used, sample demographics, and definition of impairment).[1] [2] [3]

Prevalence of olfactory impairment increases with age and male sex, increasing to approximately 25% in adults ages 60-90 years.[2] [4][5]

In a cross-sectional sample of older American adults (mean age 68 years), approximately 22% were unable to identify four or more odors using a validated odor identification task.[6] Older African Americans and Hispanics were more likely to suffer from olfactory dysfunction.[6]

Etiology

In patients presenting primarily for loss of smell, the most commonly identified etiologies include a prior viral upper respiratory infection, head trauma, and underlying chronic sinus inflammation.[7] [8] [9] These 3 causes account for over 50% of patients.

Pathophysiology

Olfactory loss may occur as a sensorineural loss, following degenerative changes in the olfactory neuronal receptors or neuroepithelium in the olfactory cleft.[10] It may also occur as a conductive loss following an obstruction or inflammation within the nasal vault that prevents access of odorants to the olfactory receptors.

Types of olfactory loss

The loss may be complete (anosmia) or partial (hyposmia). It may be associated with perceived odor distortions (dysosmia) that are related to actual environmental odorant stimulation (parosmia) or occur spontaneously (phantosmia).

Library

Examination of the right nasal cavity using rigid nasal endoscopy. A polyp can be seen protruding from the superior meatus (arrow), while the middle meatus is clear. a = middle turbinate, b = superior turbinate, c = septum
Rigid nasal endoscopic examination of a left nasal cavity suggests disease high in the nose (arrow), while the middle meatus seems clear. A = middle turbinate, B = septum
Coronal CT scan demonstrates inflammatory ethmoid disease along with obstruction of the olfactory cleft (arrow)
CT scan with coronal view through the anterior ethmoid sinus clearly displays the ostiomeatal complex, with no evidence of disease. The olfactory cleft is patent (arrow)

Citations

Key Articles

Hummel T, Whitcroft KL, Andrews P, et al. Position paper on olfactory dysfunction. Rhinology. 2016 Jan 31;56(1):1-30.[Abstract][Full Text]
Patel ZM, Holbrook EH, Turner JH, et al. International consensus statement on allergy and rhinology: olfaction. Int Forum Allergy Rhinol. 2022 Apr;12(4):327-680.[Abstract][Full Text]
Miwa T, Ikeda K, Ishibashi T, et al. Clinical practice guidelines for the management of olfactory dysfunction - secondary publication. Auris Nasus Larynx. 2019 Oct;46(5):653-62.[Abstract][Full Text]

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