Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the seventh coronavirusknown to infect humans, and causing coronavirus disease 2019 (COVID-19). . Since itsemergence in December 2019, in Wuhan, China, SARS-CoV-2 has led to a global pandemic withalmost 188 million cases and 4 million COVID-19 related deaths reported. Althoughinitially considered as a predominantly acute respiratory illness, it soon becameapparent that COVID-19 could also produce neurological manifestations and severeneurological complications. During the acute phase of SARS-CoV-2 infection, about 36% ofcases develop neurological symptoms of which 25% can be attributed to the directinvolvement of the central nervous system.There are increasing reports of central and peripheral nervous system involvement. Acuteneurological manifestations reported, include, but are not limited to: anosmia,dysgeusia, stroke, encephalomyelitis, meningo-encephalitis, posterior reversibleencephalopathy, acute necrotizing encephalopathy, new onset seizures and Guillain-Barresyndrome.However, one of the most perplexing aspects of SARS-CoV-2 is that two to four monthsafter their initial (mostly apparently mild) infection, some COVID-19 patients stillpresent a constellation of more chronic neurological symptoms colloquially known as "longCOVID-19" syndrome. In these patients, COVID-19 appears to affect long-term brainfunction and patients have functional complaints as dyspnea, hyposmia/anosmia,dysgeusia/ageusia, but also, and more importantly, memory and cognitive impairment, pain,deadening fatigue, and alterations in sleeping-pattern/insomnia, all of them correlatedwith typical 18F-FDG brain PET scan abnormalities.At the beginning of the pandemic, the medical world was not expecting the phenomenon ofCOVID-19 patients developing persistent neurologically symptoms. However, more than oneyear after the pandemic, multiple waves of the "long COVID-19" syndrome may be expectedto occur worldwide. To face the long tail impact of the COVID-19 pandemic on publichealth and its social and economic consequences on our society, future research urgentlyneeds to be dedicated to these "long COVID-19" patients in an attempt to determine,understand and manage their symptoms.A lot of "long COVID-19" patients are desperately searching for help. This project foundhis origin in the fact that suddenly many patients spontaneously presented with a similarconstellation of persistent (chronic) symptoms, months after they had (mostly mild)COVID-19, with many of them being relatively young, without underlying health problems,but unable to work due to cognitive impairment. During the entire study, the opinion andfeelings of these patients will be taken in account, all the more so because the majorityof these patients were initially left behind.The primary objective of this study is to determine the different types of neurologicaldysfunction and clinical manifestations of the "long COVID-19" syndrome and to correlatethem to abnormalities/signs on cerebral perfusion scintigraphy. Furthermore, theinvestigators aim to determine and validate a specific imaging biomarker of post-COVID-19encephalopathy.The secondary objective of this study is to determine the best therapeutic modality totreat and improve prognosis of patients with "long COVID-19" syndrome with definedcentral nervous system impairment.