Acute Disseminated Encephalomyelitis (ADEM)

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated inflammatory demyelinating disease of the central nervous system (CNS) that typically occurs following a viral infection or, rarely, vaccination. It predominantly affects children aged 5 to 8 years, although it can occur at any age. ADEM is characterized by a monophasic (single-episode) course of widespread demyelination affecting the brain and spinal cord, producing multifocal neurological deficits, encephalopathy (altered consciousness), and often dramatic clinical presentations that require urgent neurological evaluation and aggressive immunosuppressive therapy. The pathogenesis of ADEM involves molecular mimicry and post-infectious autoimmunity. During a preceding viral infection (most commonly upper respiratory tract infections, influenza, Epstein-Barr virus, cytomegalovirus, herpes simplex virus, measles, mumps, rubella, or varicella), the immune system generates T-lymphocytes and antibodies directed against viral antigens. Due to structural similarity (molecular mimicry) between certain viral epitopes and myelin proteins (particularly myelin basic protein [MBP], myelin oligodendrocyte glycoprotein [MOG], and proteolipid protein [PLP]), these immune cells cross-react with the host's own myelin sheaths. The activated autoreactive T-cells cross the blood-brain barrier, recruit macrophages and additional inflammatory cells, and initiate a widespread inflammatory attack...