Peter Wostyn
Journal: Medical hypotheses 2021;146():110469
PMID: 33401106
A proportion of COVID-19 patients develop post-COVID-19 syndrome, with long-term symptoms such as persistent fatigue, muscle pains, depressive symptoms, and non-restorative sleep, similar to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). In this article the author presents his medical hypothesis that, in a subset of patients at least, post-COVID-19 fatigue syndrome may result from damage to olfactory (smell) sensory neurons, which in turn may lead to toxic build-up within the central nervous system (CNS) through congestion of the glymphatic system (the waste clearance system of the CNS). Loss of smell and altered sensation of taste have been reported in 33–80% of COVID-19 patients but the underlying mechanisms are not yet known. Most of these patients regain their sense of smell within 1-3 weeks, suggesting that the virus does not affect the olfactory neurons but their surrounding supporting cells. Some patients, however, do not regain their sense of smell for months which may point to the destruction of neurons. A decrease in olfactory neurons may affect the flow of the cerebrospinal fluid (CSF) in an area important for CSF drainage. This may cause an increase in intracranial pressure (idiopathic intracranial hypertension, IIH) and congestion of the glymphatic system, which have been associated with chronic fatigue syndrome, as well as with headaches and tinnitus, symptoms also commonly seen in COVID-19 patients. The author states that if this hypothesis is confirmed, glymphatic-lymphatic drainage therapies, such as osteopathy, should be recommended as early treatment for patients with post-COVID-19 fatigue syndrome.
There has been concern about possible long-term sequelae resembling myalgic encephalomyelitis/chronic fatigue syndrome in COVID-19 patients. Clarifying the mechanisms underlying such a "post-COVID-19 fatigue syndrome" is essential for the development of preventive and early treatment methods for this syndrome. In the present paper, by integrating insights pertaining to the glymphatic system and the nasal cerebrospinal fluid outflow pathway with findings in patients with chronic fatigue syndrome, idiopathic intracranial hypertension, and COVID-19, I provide a coherent conceptual framework for understanding the pathophysiology of post-COVID-19 fatigue syndrome. According to this hypothesis, this syndrome may result from damage to olfactory sensory neurons, causing reduced outflow of cerebrospinal fluid through the cribriform plate, and further leading to congestion of the glymphatic system with subsequent toxic build-up within the central nervous system. I further postulate that patients with post-COVID-19 fatigue syndrome may benefit from cerebrospinal fluid drainage by restoring glymphatic transport and waste removal from the brain. Obviously, further research is required to provide further evidence for the presence of this post-viral syndrome, and to provide additional insight regarding the relative contribution of the glymphatic-lymphatic system to it. Other mechanisms may also be involved. If confirmed, the glymphatic-lymphatic system could represent a target in combating post-COVID-19 fatigue syndrome. Moreover, further research in this area could also provide new insights into the understanding of chronic fatigue syndrome.
Copyright © 2020 Elsevier Ltd. All rights reserved.
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