COVID 19-Induced Smell and Taste Impairments: Putative Impact on Physiology

Abstract

Smell and taste impairments are recognized as common symptoms in COVID 19 patients even in an asymptomatic phase. Indeed, depending on the country, in up to 85–90% of cases anosmia and dysgeusia are reported. We will review briefly the main mechanisms involved in the physiology of olfaction and taste focusing on receptors and transduction as well as the main neuroanatomical pathways. Then we will examine the current evidences, even if still fragmented and unsystematic, explaining the disturbances and mode of action of the virus at the level of the nasal and oral cavities. We will focus on its impact on the peripheral and central nervous system. Finally, considering the role of smell and taste in numerous physiological functions, especially in ingestive behavior, we will discuss the consequences on the physiology of the patients as well as management regarding food intake.

Oral Mucosa Could Be an Infectious Target of SARS-CoV-2

“…SARS-CoV-2 invades the central nervous system, but it rarely causes encephalitis or meningitis [11]. However, the onset of COVID-19 in almost 70% of the patients involves dysgeusia and dysosmia, and central nervous system damage is unlikely to be the source of dysgeusia and dysosmia [12]. SARS-CoV-2 invades the peripheral nerves and nociceptors, as do other viruses.…”

Covi̇d 19 Hastalarinda Tat Ve Koku Bozukluklari

“…COVID-19 enfeksiyonlarında meydana gelen tat alma bozuklukları için koku almada olduğu gibi iki temel mekanizma suçlanmaktadır. İlki SARS-CoV-2'nin santral sinir sistemini enfekte etmesi sonucu tat nöronlarının hasar görmesi teorisidir (9). Ancak SARS-CoV-2'ye bağlı ensefalit ve santral sinir sistemi hasar oranlarının düşük olması bu teoriyi desteklememektedir.…”

“…Ancak hastaların yaklaşık %10 kadarı 4-6 haftalık süre sonrasında da şikayetlerinde düzelme olmadığını belirtmektedirler. The British Rhinological Society (BRS) COVID-19'a bağlı koku bozuklukları için literatürdeki ilk tedavi rehberini yayınladı (22). Rehberde 2 haftadan uzun süren koku kaybında koku alma eğitimi yapılması gerektiği ve süreden bağımsız olarak özel durumlar dışında manyetik rezonans görüntülemenin gereksiz olduğu belirtildi.…”

Loss of Smell and Taste as Clinical Onset of COVID-19

“…An animal study, showed increase in macrophages in the olfactory ephitelium and lamina propria after SARS-CoV-2 infection [21]. Generally, most data indicate that the main targets of SARS-CoV-2 are sustentacular cells in the olfactory epithelium [20][21][22][23][24].…”