Clinical Diagnosis and Treatment of Olfactory Dysfunction

Abstract

Olfactory dysfunction is a relatively common disorder that is often under-recognized by both patients and clinicians. It occurs more frequently in older ages and men, and decreases patients’ quality of life, as olfactory dysfunction may affect the emotion and memory functions. Three main causes of olfactory dysfunction are sinonasal diseases, upper respiratory viral infection, and head trauma. Olfactory dysfunction is classified quantitatively (hyposmia and anosmia) and qualitatively (parosmia and phantosmia). From a pathophysiological perspective, olfactory dysfunction is also classified by conductive or sensorineural types. All patients with olfactory dysfunction will need a complete history and physical examination to identify any possible or underlying causes and psychophysical olfactory tests are essential to estimate the residual olfactory function, which is the most important prognostic factor. CT or MRI may be adjunctively used in some indicated cases such as head trauma and neurodegenerative disorders. Functional MRI (fMRI) and psychophysiological tests (olfactory event-related potential, OERP) are also used in the research setting. Compared to rapid progress that has occurred in fields of basic science and diagnostic tools for the therapy of other diseases and disorders, treatments for olfactory loss are still in a state of unmet need. In most olfactory dysfunctions, there has been no well-designed randomized controlled study to justify or prove effective treatment modalities. Therefore, with more attention to the problem and further research we can expect breakthroughs in the treatment of smell loss in the near future.