Official websites use. Share sensitive information only on official, secure websites. These authors contributed equally to the work and are considered as co-first authors. These authors contributed equally to the work and are considered as co-last authors. After recovery, during follow-up, of these patients, 31 initially hospitalized in intensive care units underwent additional imaging studies at least one brain MRI. Leptomeningeal enhancement, diffuse brain microhemorrhages, acute ischemic strokes, suspicion of cerebral vasculitis, and acute inflammatory demyelinating lesions were described on the initial brain MRIs.
During follow-up, the evolution of the leptomeningeal enhancement was discordant, and the cerebral microhemorrhages were stable. We observed normalization of the vessel walls in all patients suspected of cerebral vasculitis. Concerning the grey matter volumetry, we observed a loss of volume of 3. Besides, some complications, such as cerebral vasculitis [ 5 , 6 ], were suspected on initial MRIs but could not be confirmed thereafter. The underlying mechanisms involved are probably numerous and non-mutually exclusive [ 9 ].
A direct viral cytopathic effect appears to be uncommon, but parainfectious or postinfectious immune-mediated mechanisms may be at work. Moreover, data about neurocognitive decline after recovery from COVID are accumulating [ 10 , 11 ], but before our study, to our knowledge, no comparison with neuroimaging findings was performed in a large cohort. This single-center study conducted in a well-characterized cohort of COVID patients who underwent a brain MRI for neurological symptoms during the acute phase and carried out additional imaging studies during follow-up, after recovery from SARS-CoV-2 infection, was designed to address this issue.
This observational and purely descriptive study was approved by the ethical committee of Strasbourg University Hospital CE and was conducted in accordance with the Helsinki Declaration and its later amendments. These neuroimaging examinations were either carried out systematically or because of a persistent complaint. All these 31 patients were initially hospitalized in intensive care units ICU for severe disease. Imaging studies were conducted either on a 1. The most frequent sequences performed were 3D T1-weighted spin-echo MRI with and without contrast enhancement; diffusion-weighted, perfusion-weighted, and susceptibility-weighted imaging; and 2D or 3D FLAIR before and after administration of gadolinium-based contrast agent.
Brain MRIs were retrospectively reviewed by two neuroradiologists S. PET examinations were performed on a Siemens Vision. Image acquisition was initiated 30 min after 18F-FDG injection, including a low-dose non-contrast transmission CT scan followed by a PET scan with an acquisition time of 10 min. Sixteen patients were seen by two trained neuropsychologists between three and six months after recovery of COVID The results of four patients were not included in the analysis because they were not native French speakers.
