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 shortand 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.1,2 These 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.