How COVID-19 Affects the Brain

Abstract

COVID-19 has resulted in more than 120 million cases and 2.6 million deaths to date.Respiratory and gastrointestinal symptoms are accompanied by short-and long-term neuropsychiatric symptoms (NPs) and long-term brain sequelae.Some patients present with anosmia, cognitive and attention deficits (ie, brain fog), new-onset anxiety, depression, psychosis, seizures, and even suicidal behavior. 1,2These present before, during, and after respiratory symptoms and are unrelated to respiratory insufficiency, 1 suggesting independent brain damage.Follow-ups conducted in Germany and the United Kingdom found post-COVID-19 NPs in 20% to 70% of patients, even in young adults, and lasting months after respiratory symptoms resolved, 1 suggesting brain involvement persists.Entering through angiotensin-converting enzyme 2 receptors, 2 SARS-CoV-2 can damage endothelial cells leading to inflammation, thrombi, and brain damage.Moreover, systemic inflammation leads to decreased monoamines and trophic factors and activation of microglia, resulting in increased glutamate and N-methyl-D-aspartate (NMDA) 3 and excitotoxicity (Figure).These insults induce newonset or re-exacerbation of preexisting NPs.