Acute disseminated encephalomyelitis (ADEM) is an inflammatory demyelinating disease of the nervous system. It is typically a monophasic disease that occurs in prepubescent children; more than 80% of cases are reported in children younger than 10 years.[2,3] The onset of ADEM usually occurs in the wake of a clearly identifiable febrile prodromal illness, especially in the form of a nonspecific upper respiratory tract infection or immunization. Most cases of ADEM are thought to occur as a result of an inflammatory response provoked by infection with a virus, viral vaccine, or other infectious agent. ADEM is more common during the winter and spring months.[4,5,6]
A wide array of viral and bacterial pathogens have been associated with ADEM, including viruses such as measles, coronavirus, coxsackieviruses, cytomegalovirus, Epstein-Barr virus, herpes simplex virus, hepatitis A, human immunodeficiency virus, influenza, rubella, varicella zoster, and West Nile virus and bacteria such as Mycoplasma, Leptospira, Borrelia, Chlamydia, Rickettsia, and beta-hemolytic streptococci.[7,8,9] Less than 5% of ADEM cases occur after immunization. ADEM after vaccination has been associated with immunization for measles, rabies, hepatitis B, influenza, mumps, Japanese encephalitis, rubella, polio, varicella, diphtheria/pertussis/tetanus, pneumococcus, and smallpox. ADEM has rarely been reported after the administration of drugs such as sulfonamides, para-aminosalicylic acid, and streptomycin.
The neuropathogenesis of ADEM has not been fully elucidated.[1,2,3] The concepts of immune dysregulation and molecular mimicry have been implicated. T-helper cells sensitized to myelin autoantigens, such as myelin basic protein, proteolipid protein, and myelin oligodendrocyte proteins, may produce cytokines and chemokines, leading to further activation of T-cell and B-cell lines as well as phagocytes. The outcome is acute inflammatory demyelination, most often in the central neurons and rarely in the peripheral neurons. For more pathological details, see the study by Young et al.
ADEM is typically monophasic, but the disease can be recurrent, relapsing, and multiphasic as well. It is mostly associated with constitutional symptoms such as fever, malaise, and lethargy. The hallmark clinical feature is encephalopathy, which ranges from simple lethargy to frank coma and seizures.[1,2,3] Encephalopathy is the first sign of ADEM in more than 94% of cases. Convulsive seizures occur around the onset of ADEM in as many as 25% of cases. Other initial features include focal and multifocal signs manifesting as isolated features or in various combinations.[4,5,6,7] These reflect cerebral, brainstem, and spinal cord dysfunction and include acute hemiparesis, aphasia, cerebellar ataxia, paraparesis and quadriparesis, cranial neuropathies, and, rarely, peripheral neuropathies.[10,11] Cranial nerve palsies are seen in 35% to 40% of ADEM cases. The optic nerve is most commonly involved.
Medscape © 2022
Cite this: Neuro Case Challenge: A 16-Year-Old With Quadriparesis After Respiratory Infection - Medscape - Jun 29, 2022.