Surveying Chemosensory Dysfunction in COVID-19

Abstract

Soon after the outbreak of COVID-19, reports that smell and taste are disrupted by the illness drew the attention of chemosensory scientists and clinicians throughout the world. While other upper respiratory viruses are known to produce such disruptions, their occurrence with the deadly and highly infectious SARS-CoV-2 virus raised new questions about the nature of the deficits, their cause, and whether they might serve as indicators of the onset of the disease. Published in the July and August 2020 issues of Chemical Senses are 2 innovative, large-scale survey studies that were quickly devised and launched by separate multinational groups to address these questions in olfaction, taste, and chemesthesis. The surveys, which took different approaches and had somewhat different goals, add significant new data on the incidence and severity of smell loss in COVID-19, and the potential for olfactory dysfunction to serve as an indicator of the spread and severity of the disease. Less definitive evidence of the frequency, characteristics, and magnitude of disruptions in taste and chemesthesis point to the need for future survey studies that combine and refine the strengths of the present ones, as well as clinical studies designed to selectively measure deficits in all 3 chemosensory systems.

Trigeminal features in COVID‐19 patients with smell impairment

“…14.3% (n = 1) 85.7% (n = 6) when nasal chemesthesis was investigated, it was assessed together with olfaction in a bimodal stimulation, possibly reducing the accuracy of the results. 3 As recently demonstrated by Parma et al, 4 our data confirmed a high rate (56.6%) of severe reduction of nasal chemesthesis in COVID-19 patients with olfactory dysfunction. Our data show that trigeminal nasal sensation resolved in a high percentage of patients after 6 months of follow-up, similarly to the recovery rate of olfactory perception.…”

“…To date, few papers have studied trigeminal nasal sensation in COVID‐19 patients with smell reduction. Moreover, when nasal chemesthesis was investigated, it was assessed together with olfaction in a bimodal stimulation, possibly reducing the accuracy of the results 3 . As recently demonstrated by Parma et al., 4 our data confirmed a high rate (56.6%) of severe reduction of nasal chemesthesis in COVID‐19 patients with olfactory dysfunction.…”

“…Smell dysfunction is a frequent and early symptom of COVID‐19; it is not usually associated with nasal inflammatory reaction, but rather with neuroinvasive properties of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS‐CoV‐2) on olfactory neuroepithelium 1,2 . Previous studies reported post‐infective trigeminal nasal sensation impairment in COVID‐19 patients 3,4 . The purpose of this research note is to confirm this previous anecdotical finding with both subjective and objective tests and to correlate the presence of trigeminal nasal alteration with the degree of olfactory impairment, defining its possible role as a prognostic factor for olfactory dysfunction persistency.…”

“…1,2 Previous studies reported post-infective trigeminal nasal sensation impairment in COVID-19 patients. 3,4 The purpose of this research note is to confirm this previous anecdotical finding with both subjective and objective tests and to correlate the presence of trigeminal nasal alteration with the degree of olfactory impairment, defining its possible role as a prognostic factor for olfactory dysfunction persistency.…”

Does serotonin deficiency lead to anosmia, ageusia, dysfunctional chemesthesis and increased severity of illness in COVID-19?

“…The hitherto unexplained disruption of chemesthetic sensations of coronavirus patients [78] can also be understood by considering the deficiency of 5-HT in coronavirus patients. Chemesthetic sensations of hot pepper and cool mint activate transient receptor potential channels (TRP channels), a family of cation permeable channels (polymodal sensors), which are expressed in the taste buds, nerve fibers, and keratinocytes in the oronasal cavity [79] , [80] , [81] .…”