Early in the COVID-19 pandemic, doctors started to notice something striking. For what was originally described as a respiratory virus, SARS-CoV-2 seemed to have a strong effect on the brain, causing everything from loss of taste and smell and brain fog to, in serious cases, stroke. NYU Langone Health, a New York city research hospital, started collating those anecdotes in hopes of better understanding how the virus affects the brain and nervous system.