Acute disseminated encephalomyelitis (ADEM) is a rapid inflammatory and demyelinating process of the central nervous
system, mainly affecting the white matter, but also the gray matter. It usually occurs after viral infections or vaccinations. The case of a 26-year-old patient with sensory symptoms and weakness in the left extremities is presented. Tests showed brain and cerebellar lesions with possible demyelination. ADEM is suspected due to a history of herpes zoster. Corticosteroids are administered with satisfactory evolution. ADEM is a serious process that can affect children and adolescents and presents MRI findings similar to Multiple Sclerosis. The diagnosis is exclusionary, the treatment is with corticosteroids, but it can leave sequelae.