Introduction to Acute Disseminated Encephalomyelitis

Description

Acute Disseminated Encephalomyelitis (ADEM), also known as acute demyelinating encephalomyelitis, is a rare autoimmune disease characterized by a widespread inflammatory attack in the brain and spinal cord. ADEM not only inflames the brain and spinal cord, but it also attacks the nerves of the central nervous system, causing myelin insulation damage and the destruction of white matter. It is frequently caused by a viral infection or (in rare cases) vaccinations. Because the symptoms of ADEM are similar to those of Multiple Sclerosis (MS), the disease is classified as a borderline MS disease. ADEM is distinguished by a single flare-up, whereas MS is distinguished by multiple flare-ups (or relapses) over time. Relapses following ADEM have been reported in up to a quarter of patients, but the majority of these ‘multiphasic' presentations following ADEM are most likely due to MS. The high prevalence of ADEM with hemorrhage is astonishing. Brain inflammation, rather than neurotropism, is most likely caused by an immune response to the disease. CSF analysis revealed no evidence of an infectious process, neurological impairment was not present during the acute phase of the infection, and neuroimaging findings did not match classic toxic and metabolic disorders. The presence of bilateral periventricular lesions that are relatively asymmetrical, as well as deep white matter involvement in the cortical gray-white matter junction, thalami, basal ganglia, cerebellum, and brainstem, suggests an acute demyelination process. Approximately two-thirds of people have had an antigenic challenge in the past. ADEM is thought to be caused by influenza virus, dengue virus, enterovirus, measles, mumps, rubella, varicella zoster, Epstein-Barr virus, cytomegalovirus, herpes simplex virus, hepatitis A, coxsackie virus, and COVID-19. Although only the Sample form of the rabies vaccine has been linked to ADEM, vaccines for hepatitis B, pertussis, diphtheria, measles, mumps, rubella, pneumococcus, varicella, influenza, Japanese encephalitis, and polio have also been implicated. The majority of studies linking vaccination to the onset of ADEM use small sample sizes or case studies. Vaccination does not increase the risk of ADEM, according to large-scale epidemiological studies. While both ADEM and MS involve autoimmune demyelination, they differ in clinical, genetic, imaging, and histopathological aspects. Some authors regard MS and its borderline forms as a spectrum disease, with only chronicity, severity, and clinical course differing, whereas others regard them as distinct diseases. In children, ADEM typically appears after an antigenic challenge and remains monophasic. Nonetheless, ADEM can occur in adults and can be multiphasic clinically. The lack of agreement on a definition of multiple sclerosis makes differential diagnosis more difficult. If MS were solely defined by the separation of demyelinating lesions in time and space, as McDonald proposed, it would be meaningless because some cases of ADEM meet these criteria. AHL (or AHLE) is a severe and often fatal form of ADEM. It is also known as Acute Hemorrhagic Encephalomyelitis (AHEM), Acute Necrotizing Hemorrhagic Leukoencephalitis (ANHLE), Weston-Hurst syndrome, or Hurst's disease. AHL is uncommon occurring in about 2% of ADEM cases and characterized by necrotizing vacuities of the venues, hemorrhage, and edema. Despite clinical trials on ADEM treatment, aggressive treatment aimed at rapidly reducing CNS inflammation is the norm. As first-line therapy, high doses of intravenous corticosteroids, such as methylprednisolone or dexamethasone, are commonly used, followed by 3-6 weeks of gradually decreasing oral prednisolone doses. Patients who received methylprednisolone fared better than those who received dexamethasone. Oral taper periods of less than three weeks are more likely to relapse and result in poorer outcomes. Plasmapheresis, high doses of intravenous immunoglobulin, mitoxantrone, and cyclophosphamide, among other anti-inflammatory and immunosuppressive therapies, has been shown to be beneficial. These are alternative therapies that are used when corticosteroids are ineffective or cannot be used. Children fare better than adults and cases that do not present with fever fare worse. The latter effect could be attributed to either fever's protective effects or the fact that when fever is present, diagnosis and treatment are sought more quickly. MS will be diagnosed if multiple lesions appear at different times and in different areas of the brain.