Postviral olfactory loss
Section snippets
Incidence
A viral upper respiratory infection (URI) is one of the most commonly identified causes of persistent olfactory dysfunction. Data from the University of Cincinnati Taste and Smell Center reported a viral etiology in 78 of 354 patients presenting with a smell loss, or 22% [1]. Other centers have reported similar experiences. The Connecticut Chemosensory Clinical Research Center described 82 patients of 441, or 18.6%, presenting with an olfactory loss following a viral URI [2]. Of 750 patients
Pathophysiology
Although it is unknown which virus is most often associated with olfactory loss, viruses can invade the central nervous system through the olfactory neuroepithelium and olfactory pathways [9]. Damage may occur at the level of the epithelium and receptor cells, or in central processing pathways such as the olfactory bulb. [6] Several animal studies have demonstrated damage to central olfactory pathways and other areas of the brain after intranasal inoculation of different viruses [10], [11].
Diagnosis
There is no definitive test that will identify clearly an olfactory loss as being postviral. The diagnosis is made when a loss immediately follows a URI, in the absence of any other apparent etiology. Patients will describe a persisting olfactory deficit after resolution of cold or flu symptoms, often describing such infections as having been particularly severe. Patients usually will remember such an episode, even though they may not present for months or years afterward. If they do not
Therapy and prognosis
Olfactory neurons present receptor nerve endings that are exposed directly to the external environment, making them unique and vulnerable to injury. Perhaps this is why these bipolar neurons are the only neurons in the central nervous system that can regenerate [22]. At least in theory, therefore, the sense of smell should be able to recover following any number of environmental insults. In reality, this does not occur consistently.
Preliminary observational studies of postviral olfactory loss
References (29)
- et al.
The common cold
Lancet
(2003) - et al.
Behavioral deficits and serotonin depletion in adult rats after transient infant nasal viral infection
Neuroscience
(1990) - et al.
Development of the University of Pennsylvania Smell Identification Test: a standardized microencapsulated test of olfactory function
Physiol Behav
(1984) - et al.
The diagnosis of a conductive olfactory loss
Laryngoscope
(2001) Evaluation of olfactory dysfunction in the Connecticut chemosensory clinical research center
Laryngoscope
(1988)Smell and taste disorders, a study of 750 patients from the University of Pennsylvania Smell and Taste Center
Arch Otolaryngol Head Neck Surg
(1991)Patterns of non-conductive olfactory disorders in eastern Austria: a study of 120 patients from the Department of Otorhinolaryngology at the University of Vienna
Wien Klin Wochenschr
(2001)The common cold. NIAID Fact Sheet
(2003)Postviral olfactory loss
Report of the Panel on Communicative Disorders to the National Advisory Neurological and Communicative Disorders and Stroke Council
(1979)
Viruses and the olfactory system
Effect of olfactory bulb ablation on spread of a neurotropic coronavirus into the mouse brain
J Exp Med
Olfactory mucosal findings and clinical course in patients with olfactory disorders following upper respiratory viral infection
Rhinology
Recent advances in the pathology of olfaction
Proc R Soc Med
Cited by (158)
Polycomb repressive complex 2 regulates basal cell fate during adult olfactory neurogenesis
2023, Stem Cell ReportsBiopsy of the olfactory epithelium from the superior nasal septum: is it possible to obtain neurons without damaging olfaction?
2022, Brazilian Journal of OtorhinolaryngologyOlfactory dysfunction and COVID-19
2022, Operative Techniques in Otolaryngology - Head and Neck SurgeryAlcohol Sniff Test (AST): An Important Tool for Screening Post-Viral Olfactory Loss in Acute Flu-Like Dysfunction
2024, Indian Journal of Otolaryngology and Head and Neck SurgeryType 2 and Non-type 2 Inflammation in the Upper Airways: Cellular and Molecular Alterations in Olfactory Neuroepithelium Cell Populations
2024, Current Allergy and Asthma Reports