A ADEM is a demyelinating disease of the central nervous system (CNS), single phase, preceded by up to 75% of cases by a viral or bacterial infection, most infections by non-specific respiratory tract. Can also develop after a vaccine, and especially why it is becoming increasingly important in our environment due to the immunization schedules in children. A ADEM after vaccination occurs preferentially after measles, rubella and mumps, but has been described after polio vaccination against tick-borne encephalitis. In our environment have been reported and presented in Congress after several cases of ADEM following dengue and yellow fever vaccine.
The estimated incidence is 0.8 cases per 100,000 inhabitants per year, has no sexual or racial preponderance. Epidemiology has made changes since its original description in the early nineteenth century. In 1931, McAlpine described 3 patterns of initiation of ADEM:
1) post-vaccination,
2) after infection and
3) spontaneous.
At the time this author noted that the forms post-vaccination and spontaneous progress well and the way post-infection progresses poorly. It seems that little has changed since then because recent studies have corroborated these observations.
Symptoms usually occur after 7 to 14 days of infection or vaccination, and although not established a latency period is important to establish the temporal relationship of up to 30 days between infection or vaccination, with the disease. Some symptoms may be associated with age, in children with fever and headache occurs more frequently in adults and sensory and motor symptoms predominate from the outset. Other symptoms such as ataxia, altered level of consciousness and symptoms related to brain stem, occurring in most patients regardless of age.
Studies with Experimental Allergic Encephalitis led to the development of concepts of pathogenesis: the concept of inflammatory cascade that believes in a direct infection of the SN by the pathogen, resulting in tissue damage and invasion of a movement of self-antigens previously confined due to a disintegration of Blood-Brain Barrier. Another concept proposed homology of amino acid sequences between the external and the myelin antigen, or molecular mimicry.
The best diagnostic tool is the Magnetic Resonance Imaging (MRI). The most common are white matter lesions in multiple locations, sometimes with involvement of areas of the cortex and thalamus and basal ganglia, and most important is that these lesions have the same aspect of the evolution time, which differs from MS that has spread injury in time. The MRI should be repeated every six months at least because the lesions of ADEM tend to diminish and even disappear.
Treatment aims to slow the inflammatory response and is accomplished with intravenous steroid therapy in first choice, although there are no controlled studies with this procedure.
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Posted on Apr 17 in Health. Tags: Brain Stem, Central Nervous System, Immunization Schedules, Level Of Consciousness, Polio Vaccination, Temporal Relationship, Yellow Fever Vaccine
Thanks for the illustration , i,m Dr muhamed from Baghdad , we are seeing more cases of post vaccination ADEM , we admit cases on a weekly bases , we depend in diagnosis on history , MRI , & LP to exclude infection .we begin with methyl prednisolone cause no immunoglobuline is available . many patients respond well but we stillo in dought of diagnosis in some cases as no proper tools available for brain biopsy ..