ADEM usually evolves after infection of recent vaccination. Disease has a single-phase course but 25% of patients may suffer from a relapse. The incidence of the disease is 0.4-0.8 : 100 000, mortality is about 5%, full remission is achieved in 50-70% of patients. Disease has characteristic seasonality with peaks in winter and spring.
Pathology
The pathophysiology of this disease is still not fully clear despite the large number of immunologic changes discovered during the researches. The observation and investigation of disease characteristics and pathology generally are made on experimental models of the disease. Patients with ADEM have extensive perivenouse inflammatory process in white and grey matter with convoluting demyelinating lesions. Infiltrates consist of macrophages/monocytes and lymphocytes. Recent researches discovered that perivenouse demyelinisation is connected with activation of cortical microglial cells without loss of myelin. Macroscopically there is cerebral edema but microscopically there is hyperemia, endothelial edema, and infiltration of blood vessel wall with perivascular edema.
There are some pro and anti inflammatory cytokines and chemokines involved in pathology of ADEM unlike in MS. IL-1beta, 2, 4, 5, 8, 10; TNF-alfa, IFN-gamma.
Presentation and history
Usually, there was an infection, or fever, or vaccination in recent days/weeks before disease first manifestation. Neurological symptoms evolve 2-30 days after infection or vaccination but it is not fully proven that infection or vaccination is a trigger of ADEM.
Usually patient’s presentation consists of fever, cephalgia, meningismus, that evolves in the beginning latter in the course of the disease focal lesion signs are emerging. Classical ADEM symptoms are encephalopathy, seizures, bilateral optic neuritis; other symptoms depend on localization of lesions.
Diagnostics
Spinal tap usually shows pleocytosis (100/3) with elevated myelin basic protein in cerebrospinal fluid. There are no oligoclonal bands in liquor of patient with ADEM.
MRI shows extensive white matter lesions in the brain and spinal cord of patient with ADEM. Classical localization of lesions is subcortical region and central part of the white matter. Cortical and basal ganglia lesions are reported in patients with ADEM.
Therapy
Corticosteroids: Methylprednisolon 20mg/kg/24h 3-5 days long continuing with oral Prednisolon for 4 to 6 weeks, tapering the dose down slowly.
IVIG: is an alternative treatment for ADEM, administered in dose of 0.4-2g/kg i/v 2-3 day long.
Plasmapheresis: is administered as last chance for patients who did not respond to corticosteroids in highest doses. Plasmapheresis improves symptoms but there is no evidence of benefits administering plasmapheresis on early stages of disease.