[Long COVID: Pathogenesis and Therapeutic Approach].

A group of patients with coronavirus disease 2019 (COVID-19) exhibited various persistent or new systemic symptoms, including psychiatric symptoms, sleep disturbances, exercise intolerance, arthralgia, headache, cognitive decline, brain fog, and autonomic symptoms, all of which persisted long after the resolution of infectious symptoms. Several imaging studies have shown that long COVID cases present with decreased glucose metabolism and progressive brain atrophy. Although no single pathological hypothesis thoroughly explains the varied clinical presentations and timings, the following have attracted attention: 1) persistent viral infection, 2) persistent inflammation, 3) involvement of the autoimmune system, and 4) mitochondrial dysfunction. In all these hypotheses, inflammatory cytokines may be involved in orthostatic dysregulation by decreasing the expression and activity of ACE2, consequently changing the blood pressure through vagus nerve hyperactivation. Myopathy and peripheral neuropathy may also be caused by direct infection of the muscles and nerves, hypoxia, mitochondrial damage, and cytokine storm. Furthermore, multiple theories regarding the mechanisms by which systemic inflammatory findings affect the central nervous system have been postulated, including neuroinflammation caused by inflammatory cells crossing the blood-brain barrier via choroid plexus cells and the involvement of various autoantibodies. Despite these findings, no definitive consensus has been reached due to the complexity and diversity of COVID-19 pathophysiology. Thus, it is essential to understand the neurological symptoms and pathophysiology involved in long COVID.