“Brain fog” in the post-acute phase of Covid-19

Abstract

Introduction: Covid-19 infection can affect not only the airways but also other organs such as the brain. Individuals that tested positive for SARSCoV-2 may be asymptomatic, but can also have symptoms - such as “brain fog” - during the acute phase and/or the post-acute phase (being the last ones defined as long haulers). “Brain fog” is a set of symptoms characterized by cognitive dysfunction that includes the inability to concentrate, executive function deficits, anterograde and retrograde amnesia. Objective: Review the pathophysiology of individuals with Covid-19 post-acute phase brain fog. Design and setting: A literature review was conducted on the topic. Methods: 12 original selected articles in English and Portuguese from PubMed and Google Academic databases dated from 2017 to 2021. Results: Research evidenced that 18-36% of the patients hospitalized for Covid-19 that had neurological symptoms also experienced brain fog in the post-acute phase. Although not completely elucidated, there are hypothesized mechanisms to clarify the neurological symptoms in the “long haulers’’ patients, such as the release of pro-inflammatory substances that reduce synaptic fidelity due to dysregulation in the levels of neurotransmitters which are fundamental for brain function. In addition, SARS-CoV-2 provides microthrombus formation and possible small cerebral ischemia. Conclusion: The pathophysiology of brain fog is not yet fully proven, since the literature on the subject is limited. Therefore, more robust research in patients who developed neurological symptoms after infection by the new coronavirus is needed to clarify the pathophysiology, clinical management and most appropriate treatment for individuals with brain fog.