COVID-19 and anosmia: The story so far

Abstract

Objectives The pandemic has affected over 182 million coronavirus disease 2019 (COVID-19) cases worldwide. Accumulated evidence indicates that anosmia is one of the significant characteristics of COVID-19 with a high prevalence. However, many aspects of COVID-19-induced anosmia are still far from being fully understood. The purpose of this review is to summarize recent developments in COVID-19-induced anosmia to increase awareness of the condition. Methods A literature search was carried out using the PubMed, Embase, Web of Science, and Scopus. We reviewed the latest literature on COVID-19-induced anosmia, including mechanisms of pathogenesis, olfactory testing, anosmia as predictive tool, pathological examinations, imaging findings, affected factors, co-existing diseases, treatments, prognosis, hypothesis theories, and future directions. Results The possible pathogenesis of COVID-19-induced anosmia may involve inflammation of the olfactory clefts and damage to the olfactory epithelium or olfactory central nervous system by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The D614G spike variant may also play a role in the increased number of anosmia patients. Anosmia may also be an essential indicator of COVID-19 spread and an early indicator of the effectiveness of political decisions. The occurrence and development of COVID-19-induced anosmia may be influenced by smoking behaviors and underlying diseases such as type 2 diabetes, gastroesophageal disorders, and rhinitis. Most patients with COVID-19-induced anosmia can fully or partially recover their olfactory function for varying durations. COVID-19-induced anosmia can be treated with various approaches such as glucocorticoids and olfactory training. Conclusion Anosmia is one of the main features of COVID-19 and the underlying disease of the patient may also influence its occurrence and development. The possible pathogenesis of COVID-19-induced anosmia is very complicated, which may involve inflammation of the olfactory clefts and damage to the olfactory epithelium or olfactory central nervous system.

Can SARS-CoV-2 positive pregnant women affect the hearing of their newborns: A systematic review

“…COVID-19 predominantly affects the respiratory system of the human body, but it can also cause harm to the central nervous, cardiovascular, gastrointestinal, hepatobiliary, and renal systems [3] . In addition, COVID-19 might induce otolaryngology diseases such as anosmia and sudden sensorineural hearing loss ( HL ) [4] , [5] , [6] .…”

“…SARS-CoV-2 infects human cells through the angiotensin-converting enzyme 2 ( ACE2 ), activating transmembrane serine protease 2 ( TMPRSS2 ), hence enhancing viral uptake [5] . The SARS-CoV-2 virus may infect both the central and peripheral nerve systems, resulting in neurological disorders [15] .…”

Application of Smartphone Otoscope in Telemedicine in Rural Medical Consortium in Eastern China in the COVID-19 Era

“…Don et al ( 16 ) revealed that SO for tympanostomy tube monitoring is workable, allowing otolaryngologists to remotely track children's tympanostomy tubes and providing greater parental satisfaction. With high severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load in the nose and throat and anosmia as one feature of COVID-19, otolaryngology is a high-risk department for COVID-19 ( 9 , 23 , 24 ). As a result, several studies used SO for telemedicine services during COVID-19.…”

Deep Learning-Based Segmentation of Post-Mortem Human’s Olfactory Bulb Structures in X-ray Phase-Contrast Tomography

“…Thus, a structural study of the OB in olfactory dysfunction demonstrated a layer-specific neuronal loss in the glomerular layer [ 46 ], and degenerative changes in OB neurons has been found in AD [ 47 ]; the post-mortem high-resolution MRI of the brains affected by SARS-CoV-2 and histopathological examination demonstrated microvascular changes in OB [ 48 ]. Therefore, future studies on OB in a normal state and pathology will include investigation of the both gross- and micromorphology.…”