Determinants of long-lasting postviral COVID-19 and non-COVID-19 olfactory Dysfunction: The sanctuary theory

Abstract

Since the onset of the Coronavirus disease 2019 (COVID-19) pandemic, the long-lasting postviral olfactory dysfunction (POD) became a prevalent symptom in Western country populations. However, the pathophysiology of long-lasting POD remains poorly understood. The effectiveness of platelet-rich plasma (PRP) injections into the olfactory clefts and recent findings from COVID-19 studies brought new elements in the understanding of the pathophysiology of COVID-19 and non-COVID-19 long-lasting POD. The present hypothesis suggests that the long-lasting POD could be related to a long-lasting silent chronic inflammation in the neuroepithelium due to the persistence of virus antigen into stem cells. The immune response could limit the regenerative and recovery processes, making the olfactory region an incomplete immune sanctuary for some viruses according to some specific pathophysiological phenomena (syncytia formation).