神经系统疾病

Examining the Enantiopathic Effect of Covid-19 on Olfactory Sensitivity: A Case Report

Abstract

Shweta Kalita, Chiraag Ashokkumar* and Alan R. Hirsch

Objective: Pathophysiology behind reduced olfactory ability in hyperosmic individuals.
Background: Covid-19 infection as an enantiopathy to hyperosmia has not been described.
Design/Methods: A 63 year-right-handed male presented with hyperosmia of 150% of normal whereby aromas appeared distorted and disgusting. Shortly, he tested positive for Covid-19 which led to a resolution of his hyperosmia. Alcohol Sniff Test scores fluctuated between zero and three (anosmia). Gradually, his smell improved from 80% and 100% of normal. However, post Covid-19 infection, it returned to 130% of normal.
Results: Neurological abnormalities, Olfatory testing, Odor discrimination memory test, Total 7/12 (hyposmia). Bilateral olfactory threshold testing to phenylethyl alcohol 3 (hyposmia). Taste Threshold and Suprathreshold Testing: Mild hypogeusia to Sucrose. Ageusia to Hydrochloric acid, urea and propothiocarbamide. Olfactometer Identification Testing: Left nostril: 10 (anosmia), Right nostril: 8 (anosmia).
Conclusion: The mechanism whereby Covid-19 acts to reduce olfactory ability in normosmic individuals has been postulated as viral involvement of olfactory nerve at olfactory bulb, pathology of sustentacular cells, olfactory receptor site destruction vasculopathy/arteriopathy of cranial nerve or central connections of olfactory nerve or inflammatory response induced destruction of lamina propria and olfactory nerve apoptosis. The same may have incited a reduced olfaction in hyperosmic individuals-such may be under grouped as understanding the pathophysiology of this subject’s hyperosmia. Perceived hyperosmia is often objectively hyposmic pathology of inhibiting the inhibitory olfactory discharges that result in enhancement of perceived odor. Elimination of hyperosmia reduces functionality of remaining normosmic neurons which then became relatively hyposmic, but were perceived as normal due to lack of the inhibitory factors. Recovery of hyperosmia upon recovery of olfactory function from Covid-19 would be consistent with such a postulation. Of those with preexisting chemosensory dysfunction, query as to impact of Covid-19 on remaining sensory function is warranted.