key: cord-0705821-jhv8mtvn
authors: Vavougios, George D.
title: Potentially irreversible olfactory and gustatory impairments in COVID-19: indolent vs. fulminant SARS-CoV-2 neuroinfection
date: 2020-04-27
journal: Brain Behav Immun
DOI: 10.1016/j.bbi.2020.04.071
sha: b37918b96ec586bd6fff2b3a01d76c42a7f0fc1b
doc_id: 705821
cord_uid: jhv8mtvn

nan

To the Editor:

A recent study by Wu et al [1] discussed the neuroinvasive potential of SARS-CoV-2 on the premises of a lack of pathological evidence of definite CNS infiltration, and a predilection for what the authors termed as short-term effects on cerebral functions.

The authors' report is concise, and accurately identifies the scarcity of definitive laboratory evidence for SARS-CoV-2 CNS latency in the literature. There are, however, several aspects of SARS-CoV-2's neurotropism and its significance Specifically, a recent multicenter study has identified frequent (i.e. more than 80% of the cohort) gustatory and olfactory impairments in included patients.

Notably, while olfactory symptoms were mostly self-limiting, gustatory dysfunction persisted after the resolution of the respiratory symptoms in more than 70% of the patients [2] . Despite not being a constellation of symptoms exclusive to SARS-CoV-2 infection, hypogeusia and hyposmia are recurrent features of COVID-19 even in retrospective studies, where these symptoms were incidentally rather than systematically documented [3] . These very studies support the concept of indolent SARS-CoV-2 neurotropism as part of COVID-19's natural history, with a nevertheless persistent and significant impairment to neuronal function.

Conversely, the case for fulminant neuroinfection is illustrated in the very first case report of SARS-CoV-2 associated encephalitis by Moriguchi and colleagues, where RT-PCR detected SARS-CoV-2 RNA in the patient's CSF, despite a lack of its detection in the nasopharygeal swab specimen [4] .

In their study, Wu and colleagues correctly identify a gap of knowledge in our current understanding of SARS-CoV-2's interaction with neurons. The point they raise however also illustrates, by extent, the importance of recognizing mild manifestations of neurotropism in the clinical setting, such as gustatory and olfactory impairment. This point is further exemplified in the studies of Lechien et al [2] and Bénézit et al [3] , where hypogeusia and hyposmia were detected below at 5% retrospectively and more than 80% of the respective cohorts prospectively. In a similar manner, Moriguchi et al's [4] case report indicates that even a fulminant SARS-CoV-2 neuroinfection may escape current case definitions. Taken together, these reports point toward a needed paradigm shift in study design, in order to properly document and phenotype the extent of SARS-CoV-2's neuroinvasive potential, as well as its possible future consequences.

 Ethics approval and consent to participate : Not applicable.

 Consent for publication : Not applicable / Single Author  Availability of data and materials : Not applicable.

 Competing interests : None declared. 

Nervous system damage after COVID-19 infection: presence or absence

Olfactory and gustatory dysfunctions as a clinical presentation of mild-to-moderate forms of the coronavirus disease (COVID-19): a multicenter European study

Utility of hyposmia and hypogeusia for the diagnosis of COVID-19

A first Case of Meningitis/Encephalitis associated with SARS-Coronavirus-2