Post-COVID-syndromes: insights from brain imaging

COVID-19 may affect the brain in different ways: The Post-COVID encephalopathy (PCE) is a condition related to a severe course of initial disease and a high burden of comorbidities. Driven by a systemic inflammatory reaction, a subtle but widespread vasogenic edema affects white matter fibers targeting frontal and parietal cortical areas thereby leading to a reduced glucose metabolism within these regions. Clinically, cognitive deficits can be assessed with an emphasis on frontal and parietal functions. Cognitive function and cortical glucose metabolism almost normalize six months after infection, pointing on an at least partial reversibility of this process. In contrast, the pathophysiology of the Post-COVID-syndrome (PCS) is less well understood. According to the WHO-definition, the PCS is defined by i) history of probable or confirmed SARS-CoV-2, ii) at least one symptom (e.g. fatigue, shortness of breath, or cognitive dysfunction) with relevant impact on everyday functioning and iii) a delay of at least 3 months between COVID-19 and diagnosis. Here, younger (45 years on average) and preferentially female patients are particularly at risk. Although subjective cognitive dysfunction occurs frequently in PCS and is associated with disability, patients do not display a seminal impairment in cognitive test batteries. Moreover, assessment of brain metabolism did not reveal any pathology. Thus, PCE and PCS can be seen as cornerstones of a spectrum of cognitive disturbances in the aftermath of COVID-19.